KR20200114994A - Method and apparatus for handover without stopping of data transmission or reception in a next generation mobile communication system - Google Patents

Abstract

The present disclosure relates to a communication technique for fusing a 5^th generation (5G) communication system with an Internet of things (IoT) technology to support a higher data transmission rate than that of a 4^th generation (4G) system and a system thereof. The present disclosure can be applied to an intelligent service (for example, smart home, smart building, smart city, smart car or connected car, healthcare, digital education, retail business, security and safety related services, etc.) based on a 5G communication technology and an IoT-related technology. The present disclosure relates to an efficient handover method without stopping of data transmission and reception during handover in a next-generation mobile communication system, and an apparatus thereof. According to the present disclosure, a control signal processing method in a wireless communication system comprises the steps of: receiving a first control signal transmitted from a base station; processing the first control signal received; and transmitting a second control signal generated based on the processing to the base station.

Description

Handover method and device without data transmission/reception interruption in next-generation mobile communication system {METHOD AND APPARATUS FOR HANDOVER WITHOUT STOPPING OF DATA TRANSMISSION OR RECEPTION IN A NEXT GENERATION MOBILE COMMUNICATION SYSTEM}

The present disclosure relates to an efficient handover method and apparatus without data transmission/reception interruption during handover in a next-generation mobile communication system.

Efforts are being made to develop an improved 5G communication system or a pre-5G communication system in order to meet the increasing demand for wireless data traffic after the commercialization of 4G communication systems. For this reason, the 5G communication system or the pre-5G communication system is called a communication system after a 4G network (Beyond 4G Network) or a system after an LTE system (Post LTE). In order to achieve a high data rate, the 5G communication system is being considered for implementation in the ultra-high frequency (mmWave) band (eg, such as the 60 Giga (60 GHz) band). In order to mitigate the path loss of radio waves in the ultra-high frequency band and increase the transmission distance of radio waves, in 5G communication systems, beamforming, massive MIMO, and Full Dimensional MIMO (FD-MIMO) ), array antenna, analog beam-forming, and large scale antenna technologies are being discussed. In addition, in order to improve the network of the system, in 5G communication system, advanced small cell, advanced small cell, cloud radio access network (cloud RAN), ultra-dense network , Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, CoMP (Coordinated Multi-Points), and interference cancellation And other technologies are being developed. In addition, in the 5G system, advanced coding modulation (ACM) methods such as Hybrid FSK and QAM Modulation (FQAM) and SWSC (Sliding Window Superposition Coding), advanced access technologies such as Filter Bank Multi Carrier (FBMC), NOMA (non orthogonal multiple access), and sparse code multiple access (SCMA) have been developed.

Meanwhile, the Internet is evolving from a human-centered connection network in which humans create and consume information, to an Internet of Things (IoT) network that exchanges and processes information between distributed components such as objects. IoE (Internet of Everything) technology, which combines IoT technology with big data processing technology through connection with cloud servers, is also emerging. In order to implement IoT, technology elements such as sensing technology, wired/wireless communication and network infrastructure, service interface technology, and security technology are required, and recently, a sensor network for connection between objects, machine to machine , M2M), and MTC (Machine Type Communication) technologies are being studied. In the IoT environment, intelligent IT (Internet Technology) services that create new value in human life by collecting and analyzing data generated from connected objects can be provided. IoT is the field of smart home, smart building, smart city, smart car or connected car, smart grid, healthcare, smart home appliance, advanced medical service, etc. through the convergence and combination of existing IT (information technology) technology and various industries. Can be applied to.

Accordingly, various attempts have been made to apply a 5G communication system to an IoT network. For example, technologies such as sensor network, machine to machine (M2M), and MTC (Machine Type Communication) are implemented by techniques such as beamforming, MIMO, and array antenna. There is. As the big data processing technology described above, a cloud radio access network (cloud RAN) is applied as an example of the convergence of 5G technology and IoT technology.

In a next-generation mobile communication system, an efficient handover method is required to support a service with low transmission delay and no data loss.

The present invention for solving the above problem is a control signal processing method in a wireless communication system, the method comprising: receiving a first control signal transmitted from a base station; Processing the received first control signal; And transmitting a second control signal generated based on the processing to the base station.

In the present disclosure, various efficient handover methods that prevent data interruption time due to handover from occurring when a handover is performed in a next-generation mobile communication system are proposed to support a service without data interruption.

1A is a diagram showing the structure of an LTE system to which the present invention can be applied.
1B is a diagram showing a radio protocol structure in an LTE system to which the present invention can be applied.
1C is a diagram showing the structure of a next-generation mobile communication system to which the present invention can be applied.
1D is a diagram showing a radio protocol structure of a next-generation mobile communication system to which the present invention can be applied.
FIG. 1E is a diagram illustrating a procedure for establishing a connection with a network by switching from an RRC idle mode to an RRC connected mode by a terminal in the present invention.
1F is a diagram illustrating signaling procedures for performing handover in a next generation mobile communication system.
1G shows specific steps of the first embodiment of an efficient handover method for minimizing data interruption time due to handover in the present invention.
1H shows specific steps of the second and third embodiments of an efficient handover method for minimizing data interruption time due to handover in the present invention.
FIG. 1I shows specific steps of a fourth embodiment of an efficient handover method for minimizing data interruption time due to handover in the present invention.
1J shows specific steps of a fifth embodiment of an efficient handover method for minimizing data interruption time due to handover in the present invention.
1K is a diagram showing the structure of an efficient PDCP layer device that can be applied to embodiments of the present invention.
1L is a diagram illustrating a terminal operation applicable to embodiments proposed in the present invention.
1M shows the structure of a terminal to which an embodiment of the present invention can be applied.
1N is a block diagram of a TRP in a wireless communication system to which an embodiment of the present invention can be applied.

Hereinafter, the operating principle of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted. In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary depending on the intention or custom of users or operators. Therefore, the definition should be made based on the contents throughout this specification.

In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

A term for identifying an access node used in the following description, a term for network entities, a term for messages, a term for an interface between network objects, a term for various identification information And the like are illustrated for convenience of description. Therefore, the present invention is not limited to the terms described below, and other terms referring to objects having an equivalent technical meaning may be used.

For convenience of description below, the present invention uses terms and names defined in the 3GPP 3rd Generation Partnership Project Long Term Evolution (LTE) standard. However, the present invention is not limited by the terms and names, and can be applied equally to systems conforming to other standards. In the present invention, the eNB may be used interchangeably with gNB for convenience of description. That is, a base station described as an eNB may represent a gNB.

The present invention proposes seamless handover methods capable of minimizing data interruption time due to handover or making it 0 ms in a next-generation mobile communication system.

Specifically, the efficient handover methods proposed in the present invention may have one or two or more of the following features.

- Performing data transmission and reception (uplink or downlink data transmission and reception) through protocol layer devices (PHY layer device, MAC layer device, RLC layer device, or PDCP layer device) of the source base station and the first plurality of bearers When the terminal receives a handover command message (for example, a handover command message or an RRC Reconfiguration message) from the source base station, the terminal corresponds to the protocol layer devices of the first plurality of bearers (for example, having the same bearer identifier). ) Protocol layer devices of a new second plurality of bearers are set, and data transmission/reception (uplink or downlink data transmission and reception) is not interrupted through the first plurality of bearers with the source base station, and data is maintained. It may be characterized in that it performs transmission/reception (uplink or downlink data transmission and reception).

- After receiving the handover command message from the above, protocol layer devices (PHY layer device, MAC layer device, RLC layer device, or PDCP layer device) of a plurality of newly configured second bearers are included in the handover command message. It is characterized in that it is set for data transmission and reception with the target base station based on the established bearer configuration information or protocol layer device information.

- In the above, the UE performs data transmission/reception (uplink or downlink data transmission and reception) with the source base station to the protocol layer devices of the first plurality of bearers, while being used as the protocol layer device of the second plurality of bearers (for example, MAC layer device) It may be characterized in that it performs a random access procedure to the target base station. In the above, the random access procedure may include transmitting a preamble, receiving a random access response, or transmitting a message 3.

- In the above, the UE performs a random access procedure to the target base station with the protocol layer device of the second plurality of bearers (for example, the MAC layer device) while performing data transmission and reception with the source base station to the protocol layer devices of the first plurality of bearers. After completing, it may be characterized in that the transmission of a handover completion message to the target base station to the protocol layer devices of the second plurality of bearers.

- In the above, the UE performs a random access procedure to the target base station with the protocol layer device of the second plurality of bearers (for example, the MAC layer device) while performing data transmission and reception with the source base station to the protocol layer devices of the first plurality of bearers. After completion, a handover completion message is transmitted to the target base station to the protocol layer devices of the second plurality of bearers, and data transmission/reception (uplink or downlink) is performed.

- In the above, when the UE completes the random access procedure to the target base station to transmit and receive data with the source base station to the protocol layer devices of the first plurality of bearers (for example, when receiving a random access response or a handover completion message ( For example, RRCReconfiguration message) may be stopped when it is transmitted to the target base station or when data is first transmitted to the target base station using PUCCH or PUSCH uplink transmission resources.

- In the above, when the terminal receives the handover command message, the terminal continues to transmit and receive data (uplink or downlink data transmission and reception) with the source base station to the protocol layer devices of the first plurality of bearers, and the second plurality of bearers. When performing a random access procedure to the target base station and receiving a random access response, or when transmitting a handover completion message to the target base station, or for the first time using the PUCCH or PUSCH uplink transmission resources In this case, the UE stops transmitting the uplink data to the source base station to the protocol layer devices of the first plurality of bearers, and stops transmitting the uplink data to the target base station only to the protocol layer devices of the second plurality of bearers. The protocol layer devices of the first plurality of bearers can continue to receive downlink data from the source base station, and downlink data from the target base station is also available to the protocol layer devices of the second plurality of bearers. It is characterized in that it can continue to receive.

In the following of the present invention, efficient handover procedures without data interruption time are proposed based on the above features.

1A is a diagram showing the structure of an LTE system to which the present invention can be applied.

Referring to Figure 1a, as shown, the radio access network of the LTE system is a next-generation base station (Evolved Node B, hereinafter ENB, Node B or base station) (1a-05, 1a-10, 1a-15, 1a-20) and It is composed of MME (1a-25, Mobility Management Entity) and S-GW (1a-30, Serving-Gateway). User Equipment (hereinafter, referred to as UE or terminal) 1a-35 accesses an external network through ENBs 1a-05 to 1a-20 and S-GW 1a-30.

In FIG. 1A, ENBs 1a-05 to 1a-20 correspond to the existing node B of the UMTS system. The ENB is connected to the UEs 1a-35 through a radio channel and performs a more complex role than the existing Node B. In the LTE system, all user traffic including real-time services such as VoIP (Voice over IP) through the Internet protocol are serviced through a shared channel, so status information such as buffer status, available transmission power status, and channel status of UEs A device that collects and schedules is required, and ENB (1a-05 ~ 1a-20) is in charge of this. One ENB typically controls multiple cells. For example, in order to implement a transmission rate of 100 Mbps, the LTE system uses, for example, an orthogonal frequency division multiplexing (OFDM) in a 20 MHz bandwidth as a radio access technology. In addition, an adaptive modulation and coding method (hereinafter referred to as AMC) that determines a modulation scheme and a channel coding rate according to the channel state of the terminal is applied. The S-GW 1a-30 is a device that provides a data bearer, and creates or removes a data bearer under the control of the MME 1a-25. The MME is a device responsible for various control functions as well as mobility management functions for a terminal, and is connected to a plurality of base stations.

1B is a diagram showing a radio protocol structure in an LTE system to which the present invention can be applied.

Referring to Figure 1b, the radio protocol of the LTE system is PDCP (Packet Data Convergence Protocol 1b-05, 1b-40), RLC (Radio Link Control 1b-10, 1b-35), MAC (Medium Access Control 1b-15, 1b-30). PDCP (Packet Data Convergence Protocol) (1b-05, 1b-40) is in charge of operations such as IP header compression/restore. The main functions of PDCP are summarized as follows.

-Header compression and decompression (ROHC only)

-Transfer of user data

-In-sequence delivery of upper layer PDUs at PDCP re-establishment procedure for RLC AM

-Order reordering function (For split bearers in DC (only support for RLC AM): PDCP PDU routing for transmission and PDCP PDU reordering for reception)

-Duplicate detection of lower layer SDUs at PDCP re-establishment procedure for RLC AM

-Retransmission of PDCP SDUs at handover and, for split bearers in DC, of PDCP PDUs at PDCP data-recovery procedure, for RLC AM

-Encryption and decryption function (Ciphering and deciphering)

-Timer-based SDU discard in uplink.

Radio Link Control (hereinafter referred to as RLC) (1b-10, 1b-35) performs ARQ operation by reconfiguring a PDCP packet data unit (PDU) to an appropriate size. The main functions of RLC are summarized as follows.

-Data transfer function (Transfer of upper layer PDUs)

-ARQ function (Error Correction through ARQ (only for AM data transfer))

-Concatenation, segmentation and reassembly of RLC SDUs (only for UM and AM data transfer)

-Re-segmentation of RLC data PDUs (only for AM data transfer)

-Reordering of RLC data PDUs (only for UM and AM data transfer)

-Duplicate detection (only for UM and AM data transfer)

-Error detection function (Protocol error detection (only for AM data transfer))

-RLC SDU discard function (RLC SDU discard (only for UM and AM data transfer))

-RLC re-establishment

The MACs 1b-15 and 1b-30 are connected to several RLC layer devices configured in one terminal, and perform an operation of multiplexing RLC PDUs to MAC PDUs and demultiplexing RLC PDUs from MAC PDUs. The main functions of MAC are summarized as follows.

-Mapping between logical channels and transport channels

-Multiplexing/demultiplexing of MAC SDUs belonging to one or different logical channels into/from transport blocks (TB) delivered to/from the physical layer on transport channels

-Scheduling information reporting function

-HARQ function (Error correction through HARQ)

-Priority handling between logical channels of one UE

-Priority handling between UEs by means of dynamic scheduling

-MBMS service identification

-Transport format selection

-Padding function

The physical layer (1b-20, 1b-25) channel-codes and modulates upper layer data, converts it into OFDM symbols, and transmits it to the radio channel, or demodulates OFDM symbols received through the radio channel and decodes the channel and delivers it to the upper layer. Do the action.

1C is a diagram showing the structure of a next-generation mobile communication system to which the present invention can be applied.

Referring to Figure 1c, as shown, the radio access network of the next-generation mobile communication system (hereinafter NR or 5G) is a next-generation base station (New Radio Node B, hereinafter NR gNB or NR base station) (1c-10) and NR CN (1c). -05, New Radio Core Network). The user terminal (New Radio User Equipment, hereinafter NR UE or terminal) 1c-15 accesses the external network through the NR gNB 1c-10 and NR CN 1c-05.

In FIG. 1C, the NR gNB 1c-10 corresponds to an Evolved Node B (eNB) of an existing LTE system. The NR gNB is connected to the NR UE 1c-15 through a radio channel and can provide a service superior to that of the existing Node B. In the next-generation mobile communication system, all user traffic is serviced through a shared channel, so a device that collects and schedules status information such as buffer status, available transmission power status, and channel status of UEs is required. (1c-10) is in charge. One NR gNB typically controls multiple cells. In order to implement ultra-high-speed data transmission compared to the current LTE, it may have more than the existing maximum bandwidth, and a beamforming technology may be additionally grafted by using Orthogonal Frequency Division Multiplexing (OFDM) as a wireless access technology. . In addition, an adaptive modulation and coding method (hereinafter referred to as AMC) that determines a modulation scheme and a channel coding rate according to the channel state of the terminal is applied. The NR CN (1c-05) performs functions such as mobility support, bearer setup, and QoS setup. The NR CN is a device responsible for various control functions as well as mobility management functions for a terminal, and is connected to a plurality of base stations. In addition, the next-generation mobile communication system can be interlocked with the existing LTE system, and the NR CN is connected to the MME (1c-25) through a network interface. The MME is connected to the existing eNB (1c-30).

1D is a diagram showing a radio protocol structure of a next-generation mobile communication system to which the present invention can be applied. .

Referring to Figure 1d, the radio protocol of the next-generation mobile communication system is NR SDAP (1d-01, 1d-45), NR PDCP (1d-05, 1d-40), NR RLC (1d-10) in the terminal and the NR base station, respectively. , 1d-35), and NR MAC (1d-15, 1d-30).

The main functions of the NR SDAP (1d-01, 1d-45) may include some of the following functions.

- Transfer of user plane data

- QoS flow and data bearer mapping function for uplink and downlink (mapping between a QoS flow and a DRB for both DL and UL)

- Marking QoS flow ID for uplink and downlink (marking QoS flow ID in both DL and UL packets)

- A function of mapping a relective QoS flow to a data bearer for uplink SDAP PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs).

For the SDAP layer device, the UE may be configured with an RRC message to set whether to use the header of the SDAP layer device or the function of the SDAP layer device for each PDCP layer device, bearer or logical channel, and the SDAP header. When is set, the UE uses the NAS QoS reflective configuration 1-bit indicator (NAS reflective QoS) and the AS QoS reflective configuration 1-bit indicator (AS reflective QoS) in the SDAP header. Can be instructed to update or reset. The SDAP header may include QoS flow ID information indicating QoS. The QoS information may be used as data processing priority, scheduling information, etc. to support smooth service.

The main functions of NR PDCP (1d-05, 1d-40) may include some of the following functions.

Header compression and decompression (ROHC only)

-Transfer of user data

-In-sequence delivery of upper layer PDUs

-Out-of-sequence delivery of upper layer PDUs

-Order reordering function (PDCP PDU reordering for reception)

-Duplicate detection of lower layer SDUs

-Retransmission of PDCP SDUs

-Encryption and decryption function (Ciphering and deciphering)

-Timer-based SDU discard in uplink.

In the above, the reordering function of the NR PDCP device refers to a function of rearranging the PDCP PDUs received from the lower layer in order based on the PDCP sequence number (SN), and the function of delivering data to the upper layer in the rearranged order. It may include, or may include a function of immediately delivering without considering the order, may include a function of recording lost PDCP PDUs by rearranging the order, and reporting the status of lost PDCP PDUs It may include a function of performing the transmission side, and may include a function of requesting retransmission of lost PDCP PDUs.

The main functions of the NR RLC (1d-10, 1d-35) may include some of the following functions.

-Data transfer function (Transfer of upper layer PDUs)

-In-sequence delivery of upper layer PDUs

-Out-of-sequence delivery of upper layer PDUs

-ARQ function (Error Correction through ARQ)

-Concatenation, segmentation and reassembly of RLC SDUs

-Re-segmentation of RLC data PDUs

-Reordering of RLC data PDUs

-Duplicate detection

-Protocol error detection

-RLC SDU discard function (RLC SDU discard)

-RLC re-establishment

In the above, the in-sequence delivery function of the NR RLC device refers to the function of delivering RLC SDUs received from the lower layer to the upper layer in order, and originally, one RLC SDU is divided into several RLC SDUs and received. If so, it may include a function of reassembling and delivering it, and may include a function of rearranging the received RLC PDUs based on RLC sequence number (SN) or PDCP sequence number (SN), and rearranging the order It may include a function of recording lost RLC PDUs, may include a function of reporting a status of lost RLC PDUs to a transmitting side, and a function of requesting retransmission of lost RLC PDUs. If there is a lost RLC SDU, it may include a function of transferring only RLC SDUs before the lost RLC SDU to a higher layer in order, or if a predetermined timer expires even if there is a lost RLC SDU, the timer It may include a function of delivering all RLC SDUs received before the start of the system in order to the upper layer, or if a predetermined timer expires even if there is a lost RLC SDU, all RLC SDUs received so far are sequentially transferred to the upper layer. It may include the ability to deliver. In addition, RLC PDUs may be processed in the order in which they are received (regardless of the order of serial number and sequence number, in the order of arrival) and delivered to the PDCP device regardless of the order (Out-of sequence delivery). Segments stored in a buffer or to be received in the future may be received, reconstructed into one complete RLC PDU, processed, and delivered to the PDCP device. The NR RLC layer may not include a concatenation function, and the function may be performed by the NR MAC layer or may be replaced with a multiplexing function of the NR MAC layer.

In the above, the out-of-sequence delivery function of the NR RLC device refers to a function of directly delivering RLC SDUs received from the lower layer to the upper layer regardless of the order, and originally, one RLC SDU is When it is divided into SDUs and received, it may include a function of reassembling and transmitting them, and includes a function of storing the RLC SN or PDCP SN of the received RLC PDUs, sorting the order, and recording the lost RLC PDUs. I can.

The NR MACs 1d-15 and 1d-30 may be connected to several NR RLC layer devices configured in one terminal, and the main functions of the NR MAC may include some of the following functions.

-Mapping between logical channels and transport channels

-Multiplexing and demultiplexing function (Multiplexing/demultiplexing of MAC SDUs)

-Scheduling information reporting function

-HARQ function (Error correction through HARQ)

-Priority handling between logical channels of one UE

-Priority handling between UEs by means of dynamic scheduling

-MBMS service identification

-Transport format selection

-Padding function

The NR PHY layer (1d-20, 1d-25) channel-codes and modulates upper layer data, makes it into OFDM symbols, and transmits it to the radio channel, or demodulates and channel-decodes OFDM symbols received through the radio channel to the upper layer. You can perform the transfer operation.

FIG. 1E is a diagram illustrating a procedure for establishing a connection with a network by switching from an RRC idle mode to an RRC connected mode by a terminal in the present invention.

In FIG. 1e, the base station may send an RRCConnectionRelease message to the terminal when the terminal transmitting and receiving data in the RRC connected mode does not transmit or receive data for a predetermined reason or for a predetermined period of time to switch the terminal to the RRC idle mode (1e-01). In the future, when the current connection is not established (hereinafter, idle mode UE), when data to be transmitted occurs, it performs an RRC connection establishment process with the base station. The terminal establishes uplink transmission synchronization with the base station through a random access process and transmits an RRCConnectionRequest message to the base station (1e-05). In the message, the identifier of the terminal and the reason for establishing a connection (establishmentCause) are stored. The base station transmits an RRCConnectionSetup message so that the terminal establishes an RRC connection (1e-10).

The message includes configuration information for each service/bearer/each RLC device or logical channel or for each bearer, whether to use ROHC for each bearer/logical channel, and ROHC configuration information (e.g., ROHC version, initial information, etc. ), statusReportRequired information (information that the base station instructs the PDCP Status report to the terminal), drb-ContinueROHC information (configuration information to maintain and use the ROHC configuration information as it is, included in the PDCP layer device configuration information (pdcp-config) to be transmitted. Can). In addition, RRC connection configuration information and the like are stored in the message. The bearer for the RRC connection is also referred to as SRB (Signaling Radio Bearer), and is used for transmission and reception of an RRC message, which is a control message between the terminal and the base station.

The terminal that has established the RRC connection transmits an RRCConnetionSetupComplete message to the base station (1e-15). The message includes a control message called SERVICE REQUEST that requests the MME to set up a bearer for a predetermined service. The base station transmits the SERVICE REQUEST message contained in the RRCConnetionSetupComplete message to the MME or AMF (1e-20), and the MME or AMF determines whether to provide the service requested by the terminal. As a result of the determination, if the terminal determines to provide the requested service, the MME or AMF transmits an INITIAL CONTEXT SETUP REQUEST message to the base station (1e-25). The message includes information such as QoS (Quality of Service) information to be applied when setting up a Data Radio Bearer (DRB), and security-related information (for example, Security Key, Security Algorithm) to be applied to the DRB.

In addition, when the base station has not received the capability information of the UE from the MME or AMF, the base station may transmit a UE capability information request message to the UE to check capability information of the UE (1e-26). Upon receiving the UE capability information request message, the UE may construct and generate a UE capability information message and report it to the base station (1e-27). The terminal capability information message may include what types of handover methods the terminal supports. When the base station checks the terminal capability information, the base station can instruct the terminal by defining an indicator for each handover method as to which handover to instruct in a handover command message when instructing the terminal to handover. The terminal may perform a handover procedure to the target base station according to the handover method indicated in the handover command message.

The base station exchanges a SecurityModeCommand message (1e-30) and a SecurityModeComplete message (1e-35) to configure security with the terminal. When the security configuration is completed, the base station transmits an RRCConnectionReconfiguration message to the terminal (1e-40).

The message includes configuration information for each service/bearer/each RLC device or logical channel or for each bearer, whether to use ROHC for each bearer/logical channel, and ROHC configuration information (e.g., ROHC version, initial information, etc. ), statusReportRequired information (information that the base station instructs the PDCP Status report to the terminal), drb-ContinueROHC information (configuration information to maintain and use the ROHC configuration information as it is, included in the PDCP layer device configuration information (pdcp-config) to be transmitted. Can). In addition, RRC connection configuration information and the like are stored in the message. The bearer for the RRC connection is also referred to as SRB (Signaling Radio Bearer), and is used for transmission and reception of an RRC message, which is a control message between the terminal and the base station.

In addition, the message includes configuration information of a DRB to which user data is to be processed, and the terminal applies the information to configure the DRB and transmits an RRCConnectionReconfigurationComplete message to the base station (1e-45). The base station after completing the DRB setup with the terminal transmits an INITIAL CONTEXT SETUP COMPLETE message to the MME or AMF (1e-50), and the MME or AMF that receives it transmits the S1 BEARER SETUP message and S1 to set up the S-GW and S1 bearers. Exchange BEARER SETUP RESPONSE messages (1e-055, 1e-60). The S1 bearer is a connection for data transmission established between the S-GW and the base station, and corresponds to DRB and 1:1. When all of the above processes are completed, the terminal transmits and receives data through the base station and the S-GW (1e-65, 1e-70). This general data transmission process is largely composed of three steps: RRC connection setup, security setup, and DRB setup. In addition, the base station may transmit an RRC Connection Reconfiguration message to the terminal for a predetermined reason to refresh, add, or change the configuration (1e-75).

In the present invention, a bearer may mean including SRB and DRB, SRB means Signaling Radio Bearer, and DRB means Data Radio Bearer. The SRB is mainly used to transmit and receive RRC messages of the RRC layer device, and the DRB is mainly used to transmit and receive user layer data. In addition, UM DRB refers to a DRB using an RLC layer device operating in an UM (Unacknowledged Mode) mode, and AM DRB refers to a DRB using an RLC layer device operating in an AM (Acknowledged Mode) mode.

1F is a diagram illustrating signaling procedures for performing handover in a next generation mobile communication system.

The terminal (1f-01) in the RRC connected mode state reports the cell measurement information (Measurement Report) to the current source base station (Source eNB, 1f-02) when a periodic or specific event is satisfied (1f-05). Based on the measurement information, the source base station determines whether or not the terminal performs handover to an adjacent cell. Handover is a technology for changing a source base station providing a service to a terminal in a connected mode state to another base station (or another cell of the same base station). If the source base station determines handover, the source base station requests handover by sending an HO (Handover) request message to a new base station, that is, a target base station (Traget eNB, 1f-03) that will provide a service to the terminal (1f- 10). If the target base station accepts the handover request, it transmits a HO request Ack message to the source base station (1f-15). Upon receiving the message, the source base station transmits a handover command message (HO command message) to the terminal (1f-20). The handover command (HO command) message is transmitted from the source base station to the terminal using an RRC Connection Reconfiguration message (1f-20). Upon receiving the message, the terminal stops transmitting and receiving data with the source base station and starts a timer T304. In T304, if the terminal does not succeed in handover to the target base station for a predetermined time, the terminal returns to the original configuration and switches to the RRC Idle state. The source base station delivers a sequence number (SN) status for uplink/downlink data and, if there is downlink data, transfers it to the target base station (1f-30, 1f-35). The terminal attempts random access to the target cell indicated by the source base station (1f-40). The random access is for notifying the target cell that the terminal is moving through handover and at the same time to synchronize uplink synchronization. For the random access, the terminal transmits a preamble ID provided from the source base station or a preamble corresponding to a randomly selected preamble ID to the target cell. After transmission of the preamble, after a specific number of subframes have passed, the UE monitors whether a random access response message (RAR) is transmitted from the target cell. The time interval to be monitored is referred to as a random access response window (RAR window). During the specific time, if a random access response (RAR) is received (1f-45). The terminal transmits a handover complete (HO complete) message to the target base station as an RRC Reconfiguration Complete message (1f-55). When the random access response is successfully received from the target base station as described above, the terminal ends the T304 timer (1f-50). The target base station requests path modification to correct the paths of bearers set as the source base station (1f-60, 1f-65) and notifies the source base station to delete the UE context of the terminal (1f-70). Accordingly, the terminal attempts to receive data from the start of the RAR window to the target base station, and after receiving the RAR, transmits an RRC Reconfiguration Complete message and starts data transmission and reception with the target base station.

The present invention proposes seamless handover methods capable of minimizing data interruption time due to handover or making it 0 ms in a next-generation mobile communication system.

The UE sets a source base station and a plurality of first bearers, and transmits/receives data (uplink or downlink) through protocol layer devices (PHY layer device or MAC layer device or RLC layer device or PDCP layer device) of each bearer. Data transmission and reception) can be performed, but in the following of the present invention, for convenience of explanation, one bearer is described and described as if the terminal has one in the drawings and description.

1G shows specific steps of the first embodiment of an efficient handover method for minimizing data interruption time due to handover in the present invention.

In the first embodiment of the efficient handover method of FIG. 1G, the terminal 1g-20 receives a handover command from the source base station while transmitting and receiving data with the source base station 1g-05 in the first step (1g-01). Even so, in order to minimize a data interruption time occurring during handover, data can be continuously transmitted and received with the source base station.

In the first embodiment of the efficient handover method of FIG. 1G, the terminal 1g-20 randomly accesses the target base station 1g-10 indicated in the handover command message in the second step (1g-02). Stopping data transmission/reception (uplink data transmission and downlink data reception) with the source base station when performing a procedure or when transmitting a preamble or when transmitting data to an uplink transmission resource for the first time using a PUCCH or PUSCH transmission resource. It can be characterized.

In the first embodiment of the efficient handover method of FIG. 1G, the terminal 1g-20 completes the random access procedure to the target base station in the third step (1g-03), transmits a handover completion message, and sends the target base station. It is characterized in that data transmission and reception (uplink data transmission and downlink data reception) with each other are started.

1H shows specific steps of the second and third embodiments of an efficient handover method for minimizing data interruption time due to handover in the present invention.

In the second embodiment of the efficient handover method of FIG. 1H, the terminal 1h-20 receives a handover command from the source base station while transmitting and receiving data with the source base station 1h-05 in the first step (1h-01). Even though it may be characterized in that data can be continuously transmitted and received through the source base station and the protocol layer devices 1h-22 of the first bearer in order to minimize the data interruption time that occurs during handover. have. In addition, the protocol layer devices (PHY layer device or MAC layer device or RLC layer device or PDCP layer device, 1h-21) of the second bearer for the target base station according to the settings included in the received handover command message. It may be characterized in that it can be set or established in advance. The second bearer may be configured and established to have the same bearer identifier as the first bearer so that data interruption time does not occur for each bearer. In addition, even if the terminal receives the handover command message from the source base station, it may be characterized in that it does not initialize the MAC layer device of the first bearer in order to prevent data loss by continuing data transmission and reception due to HARQ retransmission.

In the second embodiment of the efficient handover method of FIG. 1H, the terminal 1h-20 is the target base station 1h-10 indicated in the handover command message in the second step (1h-02). Even when performing a random access procedure through the protocol layer devices of the bearer of (for example, until transmitting a preamble and receiving a random access response), the terminal transmits and receives data to and from the source base station through the protocol layer devices of the first bearer. Link data transmission and downlink data reception) can be continued.

In the second embodiment of the efficient handover method of FIG. 1H, the terminal 1h-20 randomly transmits to the target base station 1h-10 using protocol layer devices of the second bearer in the third step (1h-03). The access procedure may be completed, and data transmission/reception (downlink data reception and uplink data transmission) may be performed. In addition, when the first condition is satisfied, the terminal may stop transmitting and receiving data with the source base station 1h-05 through the protocol layer devices 1h-22 of the first bearer. In the above, the first condition may be one of the following conditions. In addition, the PDCP layer device 1h-21 of the second bearer uses information such as transmission/reception data or serial number information or header compression and decompression context stored in the PDCP layer device 1h-22 of the first bearer. It is possible to continuously perform data transmission/reception with the target base station.

- When the terminal performs a random access procedure to the target base station through the layer devices 1h-21 of the second bearer and receives a random access response

- When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

- When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits data for the first time through the PUCCH or PUSCH uplink transmission resource

- When the base station sets a separate timer as an RRC message to the terminal, and the timer expires

* The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response from the target base station is received, or the handover is completed to the target base station. It may be started when a message is transmitted or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

-After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed. When confirmed by MAC layer device (HARQ ACK) or RLC layer device (RLC ACK)

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

- When the source base station performs the efficient handover proposed in the present invention, a predetermined method (for example, when a predetermined timer expires) determines when to stop transmitting downlink data to the terminal or release the connection with the terminal. It can be determined based on (a timer can be started after a handover instruction) or when an indication that the terminal has successfully performed handover to the target base station from the target base station is received. In addition, if the downlink data is not received from the source base station for a predetermined period of time, the terminal may determine that the connection with the source base station is released and release the connection.

- When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or uplink to the terminal When a link transmission resource is first indicated

* For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

** When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed, so the allocated in the random access response message Alternatively, when the included or indicated first uplink transmission resource is received, it may be determined that the first condition is satisfied.

* If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

** The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a random access response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using uplink transmission resources, and when a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal randomly accesses the target base station. Since the procedure can be considered to have been successfully completed, the UE monitors the PDCCH afterwards, and when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE, or when the first condition is indicated. You can judge that you are satisfied. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It can also be judged that the condition of 1 is satisfied.

- If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

* If the handover command message contains uplink transmission resources for the target base station,

** When the terminal transmits message 3 (e.g., a handover complete message or an RRCReconfigurationComplete message) as an uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, a random access procedure It may be determined that is successfully completed and it may be determined that the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

* If the handover command message does not contain uplink transmission resources for the target base station

** When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (e.g., handover When a completion message or an RRCReconfigurationComplete message) is transmitted and a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) is received from the base station, it may be determined that the random access procedure has been successfully completed and the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

In the third embodiment of the efficient handover method of FIG. 1H, the terminal 1h-20 receives a handover command from the source base station while transmitting and receiving data with the source base station 1h-05 in the first step (1h-01). Even though it may be characterized in that data can be continuously transmitted and received through the source base station and the protocol layer devices 1h-22 of the first bearer in order to minimize the data interruption time that occurs during handover. have. In addition, the protocol layer devices (PHY layer device or MAC layer device or RLC layer device or PDCP layer device, 1h-21) of the second bearer for the target base station according to the settings included in the received handover command message. It may be characterized in that it can be set or established in advance. The second bearer may be configured and established to have the same bearer identifier as the first bearer so that data interruption time does not occur for each bearer. In addition, in the handover command message, in order for the terminal to skip the random access procedure to the target base station through the protocol layer devices of the second bearer, the uplink transmission resource for the target base station may be transmitted to the terminal. As another method, when a handover without a random access procedure is indicated in the handover command message, the terminal synchronizes with the target base station without the random access procedure and monitors the PDCCH from the target base station to receive uplink transmission resources. You can do it. By omitting the random access procedure as described above, data interruption time can be minimized. In addition, even if the terminal receives the handover command message from the source base station, it may be characterized in that it does not initialize the MAC layer device of the first bearer in order to prevent data loss by continuing data transmission and reception due to HARQ retransmission. In addition, in the case of the RLC layer device in the AM mode, it may be characterized in that RLC retransmission can be continuously performed.

In the third embodiment of the efficient handover method of FIG. 1H, the terminal 1h-20 is the target base station 1h-10 indicated in the handover command message in the second step (1h-02). It is characterized in that it is possible to omit performing a random access procedure through protocol layer devices of the bearer of. The terminal may construct and transmit a handover completion message to the target base station through protocol layer devices of the second bearer using the transmission resource of the target base station indicated in the handover command message. As another method, if handover without a random access procedure is indicated in the handover command message, but the uplink transmission resource to the target base station is not included, the terminal synchronizes with the target base station without the random access procedure and When the uplink transmission resource is received by monitoring the PDCCH, the handover completion message may be transmitted to the target base station. In the above, the terminal may be characterized in that it can continue to transmit and receive data (uplink data transmission and downlink data reception) with the source base station through the protocol layer devices of the first bearer.

In the third embodiment of the efficient handover method of FIG. 1H, the terminal 1h-20 randomizes to the target base station 1h-10 using protocol layer devices of the second bearer in the third step (1h-03). The access procedure may be omitted, and data transmission/reception (downlink data reception and uplink data transmission) may be performed. In addition, when the first condition is satisfied, the terminal may stop transmitting and receiving data with the source base station 1h-05 through the protocol layer devices 1h-22 of the first bearer. In the above, the first condition may be one of the following conditions. In addition, the PDCP layer device 1h-21 of the second bearer uses information such as transmission/reception data or serial number information or header compression and decompression context stored in the PDCP layer device 1h-22 of the first bearer. It is possible to continuously perform data transmission/reception with the target base station.

- When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

- When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits data for the first time through the PUCCH or PUSCH uplink transmission resource

- When the base station sets a separate timer as an RRC message to the terminal, and the timer expires

* The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response from the target base station is received, or the handover is completed to the target base station. It may be started when a message is transmitted or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

-After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed. When confirmed by MAC layer device (HARQ ACK) or RLC layer device (RLC ACK)

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

- When the source base station performs the efficient handover proposed in the present invention, a predetermined method (for example, when a predetermined timer expires) determines when to stop transmitting downlink data to the terminal or release the connection with the terminal. It can be determined based on (a timer can be started after a handover instruction) or when an indication that the terminal has successfully performed handover to the target base station from the target base station is received. In addition, if the downlink data is not received from the source base station for a predetermined period of time, the terminal may determine that the connection with the source base station is released and release the connection.

- When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or uplink to the terminal When a link transmission resource is first indicated

* For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

** When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed, so the allocated in the random access response message Alternatively, when the included or indicated first uplink transmission resource is received, it may be determined that the first condition is satisfied.

* If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

** The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a random access response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using uplink transmission resources, and when a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal randomly accesses the target base station. Since the procedure can be considered to have been successfully completed, the UE monitors the PDCCH afterwards, and when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE, or when the first condition is indicated. You can judge that you are satisfied. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It can also be judged that the condition of 1 is satisfied.

- If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

* If the handover command message contains uplink transmission resources for the target base station,

** When the terminal transmits message 3 (e.g., a handover complete message or an RRCReconfigurationComplete message) as an uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, a random access procedure It may be determined that is successfully completed and it may be determined that the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

* If the handover command message does not contain uplink transmission resources for the target base station

** When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (e.g., handover When a completion message or an RRCReconfigurationComplete message) is transmitted and a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) is received from the base station, it may be determined that the random access procedure has been successfully completed and the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

FIG. 1I shows specific steps of a fourth embodiment of an efficient handover method for minimizing data interruption time due to handover in the present invention.

In the fourth embodiment of the efficient handover method of FIG. 1i, the terminal 1i-20 receives a handover command from the source base station while transmitting and receiving data with the source base station 1i-05 in the first step 1i-01. Even though it can be characterized in that data can be continuously transmitted and received through the source base station and the protocol layer devices 1i-22 of the first bearer in order to minimize the data interruption time that occurs during handover. have. In addition, protocol layer devices (PHY layer device or MAC layer device or RLC layer device or PDCP layer device, 1i-21) of the second bearer for the target base station according to the settings included in the received handover command message. It may be characterized in that it can be set or established in advance. The second bearer may be configured and established to have the same bearer identifier as the first bearer so that data interruption time does not occur for each bearer. In addition, in the fourth embodiment, the PDCP layer device of the first bearer and the PDCP layer device of the second bearer may be characterized in that they logically operate as one PDCP layer device, and a more detailed operation method is shown in FIG. 1K. Explain. In addition, in the fourth embodiment, when the UE can transmit both the uplink data to the source base station and the target base station, a coverage reduction problem due to insufficient transmission power of the UE or a transmission resource request to a base station when transmitting uplink data In order to prevent the problem of determining whether to transmit uplink data or not to transmit uplink data (link selection), in the fourth embodiment, the time domain multiplexing (TDM) method is performed by varying the time when the terminal transmits uplink data transmission to the source base station or target base station. It may be characterized in that the uplink data can be transmitted to the source base station or the target base station through different times. As another method, if the base station sets a threshold value with an RRC message, the terminal transmits to the source base station (or target base station) when the size of the uplink data of the terminal is less than the threshold, and uplinks to the source base station and the target base station when it is greater than It is characterized in that it can perform all data transmission. The uplink data transmission may include a buffer status report procedure or a scheduling request procedure for reporting the size of data to be transmitted. In addition, even if the terminal receives the handover command message from the source base station, it may be characterized in that it does not initialize the MAC layer device of the first bearer in order to prevent data loss by continuing data transmission and reception due to HARQ retransmission. In addition, in the case of the RLC layer device in the AM mode, it may be characterized in that RLC retransmission can be continuously performed.

In the fourth embodiment of the efficient handover method of FIG. 1i, the terminal 1i-20 is the target base station 1i-10 indicated in the handover command message in the second step (1i-02). Even when performing the random access procedure through the protocol layer devices of the bearer of the UE, the terminal can continue to transmit and receive data (uplink data transmission and downlink data reception) with the source base station through the protocol layer devices of the first bearer. You can do it.

In the fourth embodiment of the efficient handover method of FIG. 1i, the terminal 1i-20 randomly transmits to the target base station 1i-10 using the protocol layer devices of the second bearer in the third step 1i-03. After completing the access procedure, data transmission and reception (downlink data reception and uplink data transmission) are performed, and the terminal transmits and receives data with the source base station through the protocol layer devices of the first bearer (uplink data transmission and downlink data transmission). Receiving) can also be characterized in that it can continue.

In the fourth embodiment of the efficient handover method of FIG. 1i, if the terminal 1i-20 satisfies the first condition in the fourth step 1i-04, the terminal 1i -22) may be characterized in that it stops transmitting and receiving data with the source base station 1i-05. In the above, the first condition may be one of the following conditions. In addition, the PDCP layer device 1i-21 of the second bearer uses information such as transmission/reception data or serial number information or header compression and decompression context stored in the PDCP layer device 1i-22 of the first bearer. It is possible to continuously perform data transmission/reception with the target base station.

- When the terminal performs a random access procedure to the target base station through the layer devices 1i-21 of the second bearer and receives a random access response

- When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

- When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits data for the first time through the PUCCH or PUSCH uplink transmission resource

- When the base station sets a separate timer as an RRC message to the terminal, and the timer expires

* The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response from the target base station is received, or the handover is completed to the target base station. It may be started when a message is transmitted or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

-After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed. When confirmed by MAC layer device (HARQ ACK) or RLC layer device (RLC ACK)

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

- When the source base station performs the efficient handover proposed in the present invention, a predetermined method (for example, when a predetermined timer expires) determines when to stop transmitting downlink data to the terminal or release the connection with the terminal. It can be determined based on (a timer can be started after a handover instruction) or when an indication that the terminal has successfully performed handover to the target base station from the target base station is received. In addition, if the downlink data is not received from the source base station for a predetermined period of time, the terminal may determine that the connection with the source base station is released and release the connection.

- When the terminal receives an instruction to release the connection with the source base station from the target base station (eg, an RRC message (eg, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When the terminal receives an instruction to release the connection with the source base station from the source base station (for example, an RRC message (for example, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or uplink to the terminal When a link transmission resource is first indicated

* For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

** When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed, so the allocated in the random access response message Alternatively, when the included or indicated first uplink transmission resource is received, it may be determined that the first condition is satisfied.

* If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

** The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a random access response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using uplink transmission resources, and when a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal randomly accesses the target base station. Since the procedure can be considered to have been successfully completed, the UE monitors the PDCCH afterwards, and when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE, or when the first condition is indicated. You can judge that you are satisfied. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It can also be judged that the condition of 1 is satisfied.

- If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

* If the handover command message contains uplink transmission resources for the target base station,

** When the terminal transmits message 3 (e.g., a handover complete message or an RRCReconfigurationComplete message) as an uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, a random access procedure It may be determined that is successfully completed and it may be determined that the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

* If the handover command message does not contain uplink transmission resources for the target base station

** When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (e.g., handover When a completion message or an RRCReconfigurationComplete message) is transmitted and a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) is received from the base station, it may be determined that the random access procedure has been successfully completed and the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

1J shows specific steps of a fifth embodiment of an efficient handover method for minimizing data interruption time due to handover in the present invention.

In the fifth embodiment of the efficient handover method of FIG. 1j, the terminal 1j-20 receives a handover command from the source base station while transmitting and receiving data with the source base station 1j-05 in the first step 1j-01. Even though it can be characterized in that it is possible to continuously transmit and receive data through the source base station and the protocol layer devices 1j-22 of the first bearer in order to minimize the data interruption time that occurs during handover. have. In addition, protocol layer devices (PHY layer device or MAC layer device or RLC layer device or PDCP layer device, 1j-21) of the second bearer for the target base station according to the settings included in the received handover command message. It may be characterized in that it can be set or established in advance. The second bearer may be configured and established to have the same bearer identifier as the first bearer so that data interruption time does not occur for each bearer. In addition, in the fifth embodiment, the PDCP layer device of the first bearer and the PDCP layer device of the second bearer may logically operate like one PDCP layer device, and a more detailed operation method is shown in FIG. 1K. Explain. In addition, in the fifth embodiment, when the UE is able to transmit both the uplink data to the source base station and the target base station, a coverage reduction problem due to insufficient transmission power of the UE or a transmission resource request to a base station when transmitting uplink data In order to prevent a problem of determining whether to transmit uplink data or not (link selection), the transmission of uplink data in the fifth embodiment may be characterized in that transmission of uplink data can be transmitted to only one of the source base station and the target base station. . Therefore, the terminal performs a scheduling request to only one of the source base station or the target base station, and reports on the size of data to be transmitted from the PDCP layer device (e.g., buffer status report transmission) to the source base station or the target base station. It may be characterized in that it is possible to transmit uplink data to only one base station by transmitting to only one of the base stations and receiving uplink transmission resources. In addition, even if the terminal receives the handover command message from the source base station, it may be characterized in that it does not initialize the MAC layer device of the first bearer in order to prevent data loss by continuing data transmission and reception due to HARQ retransmission. In addition, in the case of the RLC layer device in the AM mode, it may be characterized in that RLC retransmission can be continuously performed.

In the fifth embodiment of the efficient handover method of FIG. 1J, the terminal 1j-20 is the second step (1j-02), and the terminal 2 is the target base station 1j-10 indicated in the handover command message. Even when performing the random access procedure through the protocol layer devices of the bearer of the UE, the terminal can continue to transmit and receive data (uplink data transmission and downlink data reception) with the source base station through the protocol layer devices of the first bearer. You can do it.

In the fifth embodiment of the efficient handover method of FIG. 1j, when the terminal 1j-20 satisfies the second condition in the third step (1j-03), the terminal 1j-20 -22) to stop transmitting the uplink data to the source base station, and to transmit the uplink data to the target base station through the protocol layer devices (1j-21) of the second bearer. The data can be continuously received from the source base station and the target base station through protocol layer devices of the first bearer and the second bearer. In the above, the second condition may be one of the following conditions. In addition, the PDCP layer device 1j-21 of the second bearer uses information such as transmission/reception data or serial number information or header compression and decompression context stored in the PDCP layer device 1j-22 of the first bearer. It is possible to continuously perform data transmission/reception with the target base station.

- When the terminal performs a random access procedure to the target base station through the layer devices 1j-21 of the second bearer and receives a random access response

- When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

- When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits data for the first time through the PUCCH or PUSCH uplink transmission resource

- When the base station sets a separate timer as an RRC message to the terminal, and the timer expires

* The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response from the target base station is received, or the handover is completed to the target base station. It may be started when a message is transmitted or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

-After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed. When confirmed by MAC layer device (HARQ ACK) or RLC layer device (RLC ACK)

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

- When the terminal releases the connection with the source base station from the target base station and receives an instruction to switch the uplink to the target base station (for example, an RRC message (for example, an RRCReconfiguration message) or a MAC CE or RLC control PDU or a PDCP control PDU

- When the terminal releases the connection with the source base station from the source base station and receives an instruction to switch the uplink to the target base station (eg, an RRC message (eg, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU)

- When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or uplink to the terminal When a link transmission resource is first indicated

* For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

** When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed, so the allocated in the random access response message Alternatively, when the included or indicated first uplink transmission resource is received, it may be determined that the second condition is satisfied.

* If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

** The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a random access response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using uplink transmission resources, and when a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal randomly accesses the target base station. Since it can be seen that the procedure has been successfully completed, the UE monitors the PDCCH afterwards, and when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE, or when the second condition is first indicated. You can judge that you are satisfied. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It may be judged that the condition of 2 is satisfied.

- If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

* If the handover command message contains uplink transmission resources for the target base station,

** When the terminal transmits message 3 (e.g., a handover complete message or an RRCReconfigurationComplete message) as an uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, a random access procedure It may be determined that is successfully completed and it may be determined that the second condition is satisfied. As another method, it may be determined that the second condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

* If the handover command message does not contain uplink transmission resources for the target base station

** When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (e.g., handover When a completion message or an RRCReconfigurationComplete message) is transmitted and a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) is received from the base station, it is determined that the random access procedure has been successfully completed and the second condition is satisfied. As another method, it may be determined that the second condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

In the above, the downlink from the source base station (or target base station) is characterized in that the terminal can continue to receive downlink data from the source base station and the target base station through protocol layer devices of the first bearer and the second bearer. RLC, not data, through protocol layer devices of the first bearer (or second bearer) for AM bearers so that data can be received smoothly or the source base station (or target base station) can smoothly transmit downlink data. The RLC status report may be characterized by allowing the source base station (or target base station) to continuously perform uplink transmission. This is because, in the case of AM bearers, after transmitting data to the transmitting end, if successful delivery is not indicated by the RLC status report (ie, if the RLC status report is not received), data cannot be continuously transmitted thereafter. In addition, in the fifth embodiment of the efficient handover method of FIG. 1J, the terminal 1j-20 satisfies the second condition in the third step 1j-03, and the protocol layer devices of the first bearer ( 1j-22) stops transmitting the uplink data to the source base station, and switches to start transmitting uplink data to the target base station through the protocol layer devices 1j-21 of the second bearer. In order to smoothly receive downlink data from the source base station (or target base station) or the source base station (or target base station) to smoothly transmit downlink data, the first bearer (or the second bearer) It may be characterized in that the transmission of HARQ ACK or HARQ NACK information or PDCP control data (eg, PDCP status report or ROHC feedback information) can be continuously transmitted through protocol layer devices. In addition, in the fifth embodiment of the efficient handover method of FIG. 1J, the terminal 1j-20 satisfies the second condition in the third step 1j-03, and the protocol layer devices of the first bearer ( 1j-22) stops transmitting the uplink data to the source base station, and switches to start transmitting uplink data to the target base station through the protocol layer devices 1j-21 of the second bearer. The terminal may be characterized in that it may continue to perform data transmission due to HARQ retransmission of the MAC layer device or retransmission of the AM mode RLC layer device in order to prevent data loss to the source base station. In the above, in the fifth embodiment of the efficient handover method of FIG. 1J, the terminal 1j-20 satisfies the second condition in the third step 1j-03, and the protocol layer devices of the first bearer If (1j-22) stops transmitting the uplink data to the source base station and switches to start transmitting the uplink data to the target base station through the protocol layer devices (1j-21) of the second bearer, the target The source base station or the target base station may allocate the transmission resource to the terminal by dividing the time so that the uplink transmission resource to the base station and the uplink transmission resource to the source base station do not collide. If the uplink transmission resource to the target base station and the uplink transmission resource to the source base station collide and overlap, the terminal prioritizes the uplink transmission resource to the source base station in order to maintain the downlink data transmission from the source base station. Transmission can be performed to the source base station. As another method, if the uplink transmission resource to the target base station and the uplink transmission resource to the source base station collide and overlap, the terminal uplink transmission resource to the target base station to maintain downlink data transmission from the target base station. By prioritizing, data transmission may be performed to the target base station.

Specifically, when a handover corresponding to the fifth embodiment of the present invention is instructed when the terminal receives the handover command message, the terminal passes through the first protocol layer device until the second condition is satisfied. By performing a scheduling request and transmitting a buffer status report to the source base station, uplink transmission resources can be received, uplink data can be transmitted, and downlink data can be received from the source base station. However, if the second condition is satisfied, the UE no longer transmits data to the source base station, switches the uplink, performs a scheduling request through the second protocol layer device, and transmits a buffer status report to the target base station. It is possible to receive uplink transmission resources and transmit uplink data to a target base station. However, the UE can continue to receive downlink data from the source base station, and continues to report HARQ ACK or HARQ NACK or RLC status or PDCP control data (eg, PDCP status report or ROHC feedback information) corresponding to the downlink data. It may be characterized in that the transmission is possible. In addition, the terminal may also receive downlink data from the target base station if the second condition is satisfied.

In the fifth embodiment of the efficient handover method of FIG. 1j, if the terminal 1j-20 satisfies the first condition in the fourth step 1j-04, the terminal 1j -22) may be characterized in that the reception of downlink data from the source base station 1j-05 is stopped. In the above, the first condition may be one of the following conditions. In addition, the PDCP layer device 1j-21 of the second bearer uses information such as transmission/reception data or serial number information or header compression and decompression context stored in the PDCP layer device 1j-22 of the first bearer. It is possible to continuously perform data transmission/reception with the target base station.

- When the terminal performs a random access procedure to the target base station through the layer devices 1j-21 of the second bearer and receives a random access response

- When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

- When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits data for the first time through the PUCCH or PUSCH uplink transmission resource

- When the base station sets a separate timer as an RRC message to the terminal, and the timer expires

* The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response from the target base station is received, or the handover is completed to the target base station. It may be started when a message is transmitted or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

-After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed. When confirmed by MAC layer device (HARQ ACK) or RLC layer device (RLC ACK)

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

- When the source base station performs the efficient handover proposed in the present invention, a predetermined method (for example, when a predetermined timer expires) determines when to stop transmitting downlink data to the terminal or release the connection with the terminal. It can be determined based on (a timer can be started after a handover instruction) or when an indication that the terminal has successfully performed handover to the target base station from the target base station is received. In addition, if the downlink data is not received from the source base station for a predetermined period of time, the terminal may determine that the connection with the source base station is released and release the connection.

- When the terminal receives an instruction to release the connection with the source base station from the target base station (eg, an RRC message (eg, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When the terminal receives an instruction to release the connection with the source base station from the source base station (for example, an RRC message (for example, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- If the terminal does not receive downlink data for a predetermined time from the source base station

- When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or uplink to the terminal When a link transmission resource is first indicated

* For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

** When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed, so the allocated in the random access response message Alternatively, when the included or indicated first uplink transmission resource is received, it may be determined that the first condition is satisfied.

* If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

** The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a random access response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using uplink transmission resources, and when a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal randomly accesses the target base station. Since the procedure can be considered to have been successfully completed, the UE monitors the PDCCH afterwards, and when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE, or when the first condition is indicated. You can judge that you are satisfied. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It can also be judged that the condition of 1 is satisfied.

- If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

* If the handover command message contains uplink transmission resources for the target base station,

** When the terminal transmits message 3 (e.g., a handover complete message or an RRCReconfigurationComplete message) as an uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, a random access procedure It may be determined that is successfully completed and it may be determined that the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

* If the handover command message does not contain uplink transmission resources for the target base station

** When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (e.g., handover When a completion message or an RRCReconfigurationComplete message) is transmitted and a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) is received from the base station, it may be determined that the random access procedure has been successfully completed and the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

FIG. 1J may also show specific steps of Embodiment 5-2 of an efficient handover method for minimizing data interruption time due to handover in the present invention.

In the 5-2 embodiment of the efficient handover method of FIG. 1J, the terminal 1j-20 transmits and receives data to and from the source base station 1j-05 in the first step 1j-01, and then a handover command from the source base station. In order to minimize the data interruption time that occurs during the handover, even if the signal is received, data can be continuously transmitted and received through the protocol layer devices 1j-22 of the source base station and the first bearer. can do. In addition, protocol layer devices (PHY layer device or MAC layer device or RLC layer device or PDCP layer device, 1j-21) of the second bearer for the target base station according to the settings included in the received handover command message. It may be characterized in that it can be set or established in advance. The second bearer may be configured and established to have the same bearer identifier as the first bearer so that data interruption time does not occur for each bearer. In addition, in the 5-2 embodiment, the PDCP layer device of the first bearer and the PDCP layer device of the second bearer may be characterized in that they logically operate as one PDCP layer device, and a more detailed operation method is illustrated in FIG. Explained in 1k. In addition, in the case of allowing the UE to transmit both the uplink data to the source base station and the target base station in the 5-2 embodiment, a coverage reduction problem due to insufficient transmission power of the UE or transmission resources to a base station when transmitting uplink data In order to prevent link selection of requesting and determining whether to transmit uplink data, the uplink data transmission in Embodiment 5-2 can be transmitted to only one of the source base station and the target base station. You can do it. Therefore, the terminal performs a scheduling request to only one of the source base station or the target base station, and reports on the size of data to be transmitted from the PDCP layer device (e.g., buffer status report transmission) to the source base station or the target base station. It may be characterized in that it is possible to transmit uplink data to only one base station by transmitting to only one of the base stations and receiving uplink transmission resources. In addition, even if the terminal receives the handover command message from the source base station, it may be characterized in that it does not initialize the MAC layer device of the first bearer in order to prevent data loss by continuing data transmission and reception due to HARQ retransmission.

In the 5-2 embodiment of the efficient handover method of FIG. 1j, the terminal 1j-20 is the target base station 1j-10 indicated in the handover command message in the second step (1j-02). Even when performing the random access procedure through the protocol layer devices of the second bearer, the terminal can continue to transmit and receive data (uplink data transmission and downlink data reception) with the source base station through the protocol layer devices of the first bearer. It can be characterized.

In the 5-2 embodiment of the efficient handover method of FIG. 1J, when the terminal 1j-20 satisfies the second condition in the third step 1j-03, the first bearer protocol layer devices It is characterized in that the transmission of the uplink data to the source base station is stopped through (1j-22), and the uplink data is transmitted to the target base station through the protocol layer devices (1j-21) of the second bearer, The downlink data is characterized in that it can be continuously received from the source base station and the target base station through protocol layer devices of the first bearer and the second bearer. In the above, when the terminal stops transmitting uplink data to the source base station through the protocol layer devices 1j-22 of the first bearer, the UE performs an RLC re-establishment procedure for the transmitting RLC layer device among the protocol layer devices. Can be done. In the above, the second condition may be one of the following conditions. In addition, the PDCP layer device 1j-21 of the second bearer uses information such as transmission/reception data or serial number information or header compression and decompression context stored in the PDCP layer device 1j-22 of the first bearer. It is possible to continuously perform data transmission/reception with the target base station.

- When the terminal performs a random access procedure to the target base station through the layer devices 1j-21 of the second bearer and receives a random access response

- When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

- When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits data for the first time through the PUCCH or PUSCH uplink transmission resource

- When the base station sets a separate timer as an RRC message to the terminal, and the timer expires

* The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response from the target base station is received, or the handover is completed to the target base station. It may be started when a message is transmitted or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

-After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed. When confirmed by MAC layer device (HARQ ACK) or RLC layer device (RLC ACK)

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

- When the terminal releases the connection with the source base station from the target base station and receives an instruction to switch the uplink to the target base station (for example, an RRC message (for example, an RRCReconfiguration message) or a MAC CE or RLC control PDU or a PDCP control PDU

- When the terminal releases the connection with the source base station from the source base station and receives an instruction to switch the uplink to the target base station (eg, an RRC message (eg, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU)

- When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or uplink to the terminal When a link transmission resource is first indicated

* For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

** When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed, so the allocated in the random access response message Alternatively, when the included or indicated first uplink transmission resource is received, it may be determined that the second condition is satisfied.

* If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

** The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a random access response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using uplink transmission resources, and when a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal randomly accesses the target base station. Since it can be seen that the procedure has been successfully completed, the UE monitors the PDCCH afterwards, and when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE, or when the second condition is first indicated. You can judge that you are satisfied. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It may be judged that the condition of 2 is satisfied.

- If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

* If the handover command message contains uplink transmission resources for the target base station,

** When the terminal transmits message 3 (e.g., a handover complete message or an RRCReconfigurationComplete message) as an uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, a random access procedure It may be determined that is successfully completed and it may be determined that the second condition is satisfied. As another method, it may be determined that the second condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

* If the handover command message does not contain uplink transmission resources for the target base station

** When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (e.g., handover When a completion message or an RRCReconfigurationComplete message) is transmitted and a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) is received from the base station, it is determined that the random access procedure has been successfully completed and the second condition is satisfied. As another method, it may be determined that the second condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

In the above, the downlink from the source base station (or target base station) is characterized in that the terminal can continue to receive downlink data from the source base station and the target base station through protocol layer devices of the first bearer and the second bearer. RLC, not data, through protocol layer devices of the first bearer (or second bearer) for AM bearers so that data can be received smoothly or the source base station (or target base station) can smoothly transmit downlink data. The RLC status report may be characterized by allowing the source base station (or target base station) to continuously perform uplink transmission. This is because, in the case of AM bearers, after transmitting data to the transmitting end, if successful delivery is not indicated by the RLC status report (ie, if the RLC status report is not received), data cannot be continuously transmitted thereafter. In addition, in order to smoothly receive downlink data from the source base station (or target base station) or the source base station (or target base station) to smoothly transmit downlink data, the protocol of the first bearer (or the second bearer) It may be characterized in that the transmission of HARQ ACK or HARQ NACK information or PDCP control data (for example, PDCP status report or ROHC feedback information) can be continuously transmitted through layer devices.

Specifically, when a handover corresponding to the fifth embodiment of the present invention is instructed when the terminal receives the handover command message, the terminal passes through the first protocol layer device until the second condition is satisfied. By performing a scheduling request and transmitting a buffer status report to the source base station, uplink transmission resources can be received, uplink data can be transmitted, and downlink data can be received from the source base station. However, if the first condition is satisfied, the UE no longer transmits data to the source base station, switches the uplink, performs a scheduling request through the second protocol layer device, and transmits a buffer status report to the target base station. It is possible to receive uplink transmission resources and transmit uplink data to a target base station. However, the UE can continue to receive downlink data from the source base station, and continues to report HARQ ACK or HARQ NACK or RLC status or PDCP control data (eg, PDCP status report or ROHC feedback information) corresponding to the downlink data. It may be characterized in that the transmission is possible. In addition, the terminal may also receive downlink data from the target base station if the second condition is satisfied.

In the 5-2 embodiment of the efficient handover method of FIG. 1J, if the terminal 1j-20 satisfies the first condition in the fourth step (1j-04), the terminal is the protocol layer devices of the first bearer. It may be characterized in that the reception of downlink data from the source base station 1j-05 is stopped through (1j-22). In the above, the first condition may be one of the following conditions. In addition, the PDCP layer device 1j-21 of the second bearer uses information such as transmission/reception data or serial number information or header compression and decompression context stored in the PDCP layer device 1j-22 of the first bearer. It is possible to continuously perform data transmission/reception with the target base station.

- When the terminal performs a random access procedure to the target base station through the layer devices 1j-21 of the second bearer and receives a random access response

- When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

- When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits data for the first time through the PUCCH or PUSCH uplink transmission resource

- When the base station sets a separate timer as an RRC message to the terminal, and the timer expires

* The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response from the target base station is received, or the handover is completed to the target base station. It may be started when a message is transmitted or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

-After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed. When confirmed by MAC layer device (HARQ ACK) or RLC layer device (RLC ACK)

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

- When the source base station performs the efficient handover proposed in the present invention, a predetermined method (for example, when a predetermined timer expires) determines when to stop transmitting downlink data to the terminal or release the connection with the terminal. It can be determined based on (a timer can be started after a handover instruction) or when an indication that the terminal has successfully performed handover to the target base station from the target base station is received. In addition, if the downlink data is not received from the source base station for a predetermined period of time, the terminal may determine that the connection with the source base station is released and release the connection.

- When the terminal receives an instruction to release the connection with the source base station from the target base station (eg, an RRC message (eg, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When the terminal receives an instruction to release the connection with the source base station from the source base station (for example, an RRC message (for example, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- If the terminal does not receive downlink data for a predetermined time from the source base station

- When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or uplink to the terminal When a link transmission resource is first indicated

* For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

** When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed, so the allocated in the random access response message Alternatively, when the included or indicated first uplink transmission resource is received, it may be determined that the first condition is satisfied.

* If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

** The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a random access response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using uplink transmission resources, and when a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal randomly accesses the target base station. Since the procedure can be considered to have been successfully completed, the UE monitors the PDCCH afterwards, and when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE, or when the first condition is indicated. You can judge that you are satisfied. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It can also be judged that the condition of 1 is satisfied.

- If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

* If the handover command message contains uplink transmission resources for the target base station,

** When the terminal transmits message 3 (e.g., a handover complete message or an RRCReconfigurationComplete message) as an uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, a random access procedure It may be determined that is successfully completed and it may be determined that the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

* If the handover command message does not contain uplink transmission resources for the target base station

** When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (e.g., handover When a completion message or an RRCReconfigurationComplete message) is transmitted and a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) is received from the base station, it may be determined that the random access procedure has been successfully completed and the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

In FIG. 1f of the present invention, when transmitting a handover command message (1f-20) to the terminal, the base station defines indicators for the embodiments proposed in the present invention in the handover command message (for example, RRCReconfiguration message) It is possible to instruct the terminal whether to trigger the handover procedure corresponding to the embodiment, and the terminal performs a handover procedure according to the handover method indicated in the handover command message and minimizes data interruption time to the target base station. Handover can be performed. As another method, in the handover command message, an indicator for the embodiments proposed in the present invention may be defined for each bearer, and a specific embodiment to be applied to which bearer during handover may be indicated in more detail. For example, the embodiments of the present invention may be applied only to an AM bearer driven by an RLC layer device driven in the AM mode, or extended and applied to a UM bearer driven by an RLC layer device driven in the UM mode. May be. In addition, it is assumed that the embodiments proposed in the present invention are applied to DRB. However, if necessary (for example, if the UE maintains the SRB for the source base station and fails to handover to the target base station, it is possible to report or restore the handover failure message to the SRB for the source base station), the SRB is also extended. It can also be applied.

In the embodiments of the present invention, when the UE performs data transmission/reception with the source base station through the protocol layer devices of the first bearer and data transmission/reception with the target base station through the protocol layer devices of the second bearer, the first The MAC layer device of the bearer and the MAC layer device of the second bearer operate separate DRX (Discontinuous Reception) periods, respectively, to reduce battery consumption of the terminal. That is, the UE may continue to apply the DRX cycle of the MAC layer device when transmitting and receiving data through the protocol layer devices of the first bearer even after receiving the handover command message, and the first condition or DRX may be stopped according to the second condition. In addition, the UE may separately apply the DRX cycle to the MAC layer device of the second bearer according to the instruction of the target base station.

In addition, in the present invention, the meaning that the terminal stops uplink transmission to the source base station through the protocol layer devices of the first bearer and stops downlink transmission from the source base station means that the protocol layer devices of the first bearer (PHY layer devices) Or, it means that the UE re-establishes, initializes, or releases a MAC layer device, an RLC layer device, or a PDCP layer device.

In the embodiments of the present invention, for convenience of explanation, it has been described that the terminal is configured with a first bearer for a source base station or a second bearer for a target base station, and the terminal is a plurality of first bearers for the source base station. Alternatively, it can be easily extended to a case in which a plurality of second bearers for the target base station are configured and applied equally. As another method, a case in which a plurality of bearers for a plurality of target base stations are configured can be easily extended and applied equally. For example, it is possible to perform a handover procedure to the first target base station and set the second bearers. If the handover fails, the handover procedure is performed to the second target base station, and the second bearers are set to Among the target base stations, the UE may search for and determine a cell that satisfies a predetermined condition (eg, a certain signal strength or more) by itself, and may determine one cell to perform a handover procedure.

1K is a diagram showing the structure of an efficient PDCP layer device that can be applied to embodiments of the present invention.

In the present invention, the structure of an efficient PDCP layer device as shown in FIG. 1K is proposed. The structure of the PDCP layer device of FIG. 1K can be applied to the second, third, fourth, or fifth embodiment of an efficient handover method for minimizing data interruption time proposed in the present invention.

In FIG. 1K, the terminal 1k-20 performs data transmission/reception with the source base station 1k-05 through the protocol layer devices of the first bearer, and the target base station 1k-10 through the protocol layer devices of the second bearer. ) Data transmission and reception can be performed simultaneously.

In the above, the PDCP layer device of the first bearer and the PDCP layer device of the second bearer may be configured in the terminal, respectively, but may logically operate as one PDCP layer device as shown in FIG. 1K. Specifically, the one PDCP layer device divides the functions of the PDCP layer device into an upper PDCP layer device (1k-23) and two lower PDCP layer devices (1k-21, 1k-) for each source base station and each target base station. 22) can be implemented.

In the above, the upper transmitting PDCP layer device 1k-23 may perform a role of allocating a PDCP serial number to data received from the upper layer device. And header compression can also be performed. In addition, in the two lower transmission PDCP layer devices (1k-21, 1k-22) for each source base station and each target base station, integrity protection is set using a separate security key set with each source base station and each target base station. If present, the integrity protection procedure is applied to the PDCP header and data (PDCP SDU), the encryption procedure is applied, and the transmission is performed by transferring to the transmission RLC layer device of each first bearer or the transmission RLC layer device of the second bearer. I can. In the above, the two lower transmission PDCP layer devices (1k-21, 1k-22) can perform parallel processing of header compression or integrity protection or encryption procedures in parallel to accelerate data processing speed. The two lower transmission PDCP layer devices may be characterized in that the integrity protection or encryption procedure is performed by using different security keys. In addition, it may be characterized in that the integrity protection or encryption procedure of different data is performed by logically applying different security keys or security algorithms in one transmitting PDCP layer device.

In the above, the upper receiving PDCP layer device (1k-23) performs a duplicate detection function on the data received from the lower layer devices based on the PDCP serial number, or arranges the order of the received data in ascending order of the PDCP serial number. By doing so, it can play the role of delivering it to the upper layer in order. In addition, header compression may be decompressed. In addition, in the two lower receiving PDCP layer devices (1k-21, 1k-22) for each source base station and each target base station, integrity protection is set using a separate security key set with each source base station and each target base station. If present, the integrity verification procedure can be applied to the PDCP header and data (PDCP SDU), the decoding procedure is applied, and transmitted to the upper receiving PDCP layer device to perform data processing. In the two lower receiving PDCP layer devices, in order to reduce unnecessary integrity verification or decoding procedures, a window is driven based on the PDCP serial number to discard data outside the window and redundant data is first performed, and valid data in the window is performed. It is also possible to perform the integrity verification or decryption procedure for only those. The two lower receiving PDCP layer devices are respectively based on the PDCP serial number. In the two lower transmitting PDCP layer devices (1k-21, 1k-22), header compression or integrity protection in parallel in order to accelerate data processing speed or It may be characterized in that parallel processing for performing an encryption procedure can be performed, and that the two lower transmission PDCP layer devices perform the integrity protection or encryption procedure using different security keys. It can be characterized. In addition, it may be characterized in that the integrity protection or encryption procedure of different data is performed by logically applying different security keys or security algorithms in one transmitting PDCP layer device. In addition, the lower receiving PDCP layer devices may perform an out-of-sequence deciphering or integrity verification procedure for each data received regardless of the order of the PDCP serial numbers.

When the one PDCP layer device distinguishes between the layer devices of the first bearer and the layer devices of the second bearer, consider that they are connected to different MAC layer devices or have different logical channel identifiers, or Considering that they are different RLC layer devices connected to different MAC layer devices or using different encryption keys, the layer devices of the first bearer (or the first RLC layer device) and By separating layer devices of the second bearer (or second RLC layer devices), encryption or decryption procedures are performed with different security keys for uplink data and downlink data, and different compression protocol contexts are used. It may be characterized by compressing or decompressing.

When the fourth embodiment or the fifth embodiment proposed in the present invention is instructed in the handover command message to the terminal and applied and executed by the terminal, the terminal satisfies the following fourth condition for each bearer before receiving the handover command message. The PDCP layer device used for each bearer can be switched or changed to the structure of the effective PDCP layer device proposed in FIG. 1K, or newly configured and applied. In the above, the fourth condition may be one or more of the following conditions.

- When the terminal receives the handover command message from the source base station and instructs the handover using the fourth or fifth embodiment proposed in the present invention in the handover command message, or the efficient PDCP layer device structure proposed in FIG. 1K If instructed how to apply,

- When the terminal performs a random access procedure to the target base station through the layer devices 1j-21 of the second bearer and receives a random access response

- When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

- When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits or receives data for the first time through the PUCCH or PUSCH uplink transmission resource

- When the base station sets a separate timer as an RRC message to the terminal, and the timer expires

* The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response is received from the target base station or handover to the target base station. It may be started when transmitting a completion message or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

- After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed by MAC. When confirmed by a layer device (HARQ ACK) or an RLC layer device (RLC ACK)

- After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, uplink transmission resources are allocated from the target base station for the first time. When received or when an uplink transmission resource is first indicated

- When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or uplink to the terminal When a link transmission resource is first indicated

* For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

** When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed, so the allocated in the random access response message Alternatively, when the included or indicated first uplink transmission resource is received, it may be determined that the fourth condition is satisfied.

* If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

** The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a random access response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using uplink transmission resources, and when a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal randomly accesses the target base station. Since the procedure can be considered to have been successfully completed, the UE monitors the PDCCH afterwards, and when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE, or the fourth condition is determined for the first time. You can judge that you are satisfied. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It may be judged that the condition of 4 is satisfied.

- If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

* If the handover command message contains uplink transmission resources for the target base station,

** When the terminal transmits message 3 (e.g., a handover complete message or an RRCReconfigurationComplete message) as an uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, a random access procedure It may be determined that is successfully completed and it may be determined that the fourth condition is satisfied. Alternatively, it may be determined that the fourth condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

* If the handover command message does not contain uplink transmission resources for the target base station

** When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (e.g., handover When a completion message or an RRCReconfigurationComplete message) is transmitted and a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) is received from the base station, it is determined that the random access procedure has been successfully completed and the fourth condition is satisfied. Alternatively, it may be determined that the fourth condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

In addition, when the fourth embodiment or the fifth embodiment proposed in the present invention is instructed to the terminal in the handover command message and applied and executed by the terminal, the terminal receives the handover command message if the fourth condition is satisfied for each bearer. The PDCP layer device previously used for each bearer can be switched or changed to the structure of the efficient PDCP layer device proposed in FIG. 1K, or newly configured and applied. In addition, if the following fifth condition is satisfied, the reception of downlink data from the source base station is stopped, and the terminal switches or changes to the structure of the efficient PDCP layer device proposed in FIG. 1K for each bearer, or a handover command to the newly configured structure of the PDCP layer device. Before the message is received, it can be switched back to the PDCP layer device used for each bearer, changed or newly applied. In the above, the fifth condition may be one or more of the following conditions.

- When the terminal performs a random access procedure to the target base station through the layer devices 1j-21 of the second bearer and receives a random access response

- When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

- When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits data for the first time through the PUCCH or PUSCH uplink transmission resource

- When the base station sets a separate timer as an RRC message to the terminal, and the timer expires

* The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response is received from the target base station or handover to the target base station. It may be started when transmitting a completion message or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

- After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed by MAC. When confirmed by a layer device (HARQ ACK) or an RLC layer device (RLC ACK)

- After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, uplink transmission resources are allocated from the target base station for the first time. When received or when an uplink transmission resource is first indicated

- When the terminal receives an instruction to release the connection with the source base station from the target base station (eg, an RRC message (eg, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When the terminal receives an instruction to release the connection with the source base station from the source base station (for example, an RRC message (for example, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- If the terminal does not receive downlink data for a predetermined time from the source base station

- When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or uplink to the terminal When a link transmission resource is first indicated

* For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

** When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed, so the allocated in the random access response message Alternatively, when the included or indicated first uplink transmission resource is received, it may be determined that the fifth condition is satisfied.

* If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

** The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a random access response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using uplink transmission resources, and when a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal randomly accesses the target base station. Since the procedure can be considered to have been successfully completed, the UE monitors the PDCCH afterwards, and when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE, or the fifth condition is determined for the first time. You can judge that you are satisfied. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It may be judged that the condition of 5 is satisfied.

- If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

* If the handover command message contains uplink transmission resources for the target base station,

** When the terminal transmits message 3 (e.g., a handover complete message or an RRCReconfigurationComplete message) as an uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, a random access procedure It may be determined that is successfully completed and it may be determined that the fifth condition is satisfied. Alternatively, it may be determined that the fifth condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

* If the handover command message does not contain uplink transmission resources for the target base station

** When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (e.g., handover When a completion message or an RRCReconfigurationComplete message) is transmitted and a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) is received from the base station, it may be determined that the random access procedure has been successfully completed, and the fifth condition may be satisfied. Alternatively, it may be determined that the fifth condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

As another method, the UE stops receiving downlink data from the source base station when the fifth condition is satisfied, and the RLC layer device or MAC of the first protocol layer device for each bearer determines the structure of the efficient PDCP layer device proposed in FIG. The layer device may be released and the structure of the effective PDCP layer device proposed in FIG. 1K may be continuously applied and used for each bearer.

1L is a diagram illustrating a terminal operation applicable to embodiments proposed in the present invention.

In FIG. 1L, when the terminal 1l-05 receives the handover command message, the terminal sets and establishes protocol layer devices of the second bearer for the target base station indicated in the message, and randomly through the established protocol layer devices. Even when performing the access procedure to the target base station (1l-10, 1l-15), the terminal can continue to transmit and receive data (uplink data transmission and downlink data reception) with the source base station through the protocol layer devices of the first bearer. Yes (1l-20).

If the second condition is satisfied, the UE stops transmitting uplink data to the source base station through the protocol layer devices of the first bearer, and uplinks through the protocol layer devices 1j-21 of the second bearer. The link data is transmitted to the target base station, and the downlink data can be continuously received from the source base station and the target base station through protocol layer devices of the first bearer and the second bearer (11- 30). In the above, the second condition may be one of the following conditions. In addition, the PDCP layer device 1j-21 of the second bearer uses information such as transmission/reception data or serial number information or header compression and decompression context stored in the PDCP layer device 1j-22 of the first bearer. It is possible to continuously perform data transmission/reception with the target base station.

- When the terminal performs a random access procedure to the target base station through the layer devices 1j-21 of the second bearer and receives a random access response

- When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

- When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits data for the first time through the PUCCH or PUSCH uplink transmission resource

- When the base station sets a separate timer as an RRC message to the terminal, and the timer expires

* The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response from the target base station is received, or the handover is completed to the target base station. It may be started when a message is transmitted or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

-After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed. When confirmed by MAC layer device (HARQ ACK) or RLC layer device (RLC ACK)

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

- When the terminal releases the connection with the source base station from the target base station and receives an instruction to switch the uplink to the target base station (for example, an RRC message (for example, an RRCReconfiguration message) or a MAC CE or RLC control PDU or a PDCP control PDU

- When the terminal releases the connection with the source base station from the source base station and receives an instruction to switch the uplink to the target base station (eg, an RRC message (eg, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU)

- When the terminal receives the handover command message from the source base station and instructs the handover using the fourth or fifth embodiment proposed in the present invention in the handover command message, or the efficient PDCP layer device structure proposed in FIG. 1K If instructed how to apply,

- When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or uplink to the terminal When a link transmission resource is first indicated

* For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

** When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed, so the allocated in the random access response message Alternatively, when the included or indicated first uplink transmission resource is received, it may be determined that the second condition is satisfied.

* If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

** The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a random access response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using uplink transmission resources, and when a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal randomly accesses the target base station. Since it can be seen that the procedure has been successfully completed, the UE monitors the PDCCH afterwards, and when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE, or when the second condition is first indicated. You can judge that you are satisfied. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It may be judged that the condition of 2 is satisfied.

- If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

* If the handover command message contains uplink transmission resources for the target base station,

** When the terminal transmits message 3 (e.g., a handover complete message or an RRCReconfigurationComplete message) as an uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, a random access procedure It may be determined that is successfully completed and it may be determined that the second condition is satisfied. As another method, it may be determined that the second condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

* If the handover command message does not contain uplink transmission resources for the target base station

** When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (e.g., handover When a completion message or an RRCReconfigurationComplete message) is transmitted and a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) is received from the base station, it is determined that the random access procedure has been successfully completed and the second condition is satisfied. As another method, it may be determined that the second condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

If the second condition is not satisfied, the second condition can be checked while continuing to perform the existing procedure.

In addition, if the first condition is satisfied, the UE may stop receiving downlink data from the source base station 1j-05 through the protocol layer devices of the first bearer (1l-45). In the above, the first condition may be one of the following conditions. In addition, the PDCP layer device 1j-21 of the second bearer uses information such as transmission/reception data or serial number information or header compression and decompression context stored in the PDCP layer device 1j-22 of the first bearer. It is possible to continuously perform data transmission/reception with the target base station.

- When the terminal performs a random access procedure to the target base station through the layer devices 1j-21 of the second bearer and receives a random access response

- When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

- When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits data for the first time through the PUCCH or PUSCH uplink transmission resource

- When the base station sets a separate timer as an RRC message to the terminal, and the timer expires

* The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response from the target base station is received, or the handover is completed to the target base station. It may be started when a message is transmitted or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

-After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed. When confirmed by MAC layer device (HARQ ACK) or RLC layer device (RLC ACK)

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

- When the source base station performs the efficient handover proposed in the present invention, a predetermined method (for example, when a predetermined timer expires) determines when to stop transmitting downlink data to the terminal or release the connection with the terminal. It can be determined based on (a timer can be started after a handover instruction) or when an indication that the terminal has successfully performed handover to the target base station from the target base station is received. In addition, if the downlink data is not received from the source base station for a predetermined period of time, the terminal may determine that the connection with the source base station is released and release the connection.

- When the terminal receives an instruction to release the connection with the source base station from the target base station (eg, an RRC message (eg, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When the terminal receives an instruction to release the connection with the source base station from the source base station (for example, an RRC message (for example, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- If the terminal does not receive downlink data for a predetermined time from the source base station

- When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or uplink to the terminal When a link transmission resource is first indicated

* For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

** When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed, so the allocated in the random access response message Alternatively, when the included or indicated first uplink transmission resource is received, it may be determined that the first condition is satisfied.

* If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

** The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a random access response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using uplink transmission resources, and when a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal randomly accesses the target base station. Since the procedure can be considered to have been successfully completed, the UE monitors the PDCCH afterwards, and when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE, or when the first condition is indicated. You can judge that you are satisfied. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It can also be judged that the condition of 1 is satisfied.

- If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

* If the handover command message contains uplink transmission resources for the target base station,

** When the terminal transmits message 3 (e.g., a handover complete message or an RRCReconfigurationComplete message) as an uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, a random access procedure It may be determined that is successfully completed and it may be determined that the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

* If the handover command message does not contain uplink transmission resources for the target base station

** When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (e.g., handover When a completion message or an RRCReconfigurationComplete message) is transmitted and a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) is received from the base station, it may be determined that the random access procedure has been successfully completed and the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

If the first condition is not satisfied above, the first condition can be checked while continuing to perform the existing procedure.

In the following of the present invention, examples of the handover procedure for minimizing the data interruption time proposed in the present invention (the first embodiment or the second embodiment or the third embodiment or the fourth embodiment or the fifth embodiment or the fifth embodiment) When performing the -2 embodiment), it is necessary to operate the PDCP layer device to prevent data loss and no data interruption time. Accordingly, in the following of the present invention, embodiments of a PDCP layer device procedure supporting a handover procedure for minimizing data interruption time are proposed.

Embodiments of the PDCP layer apparatus procedure supporting a handover procedure for minimizing data interruption time of the present invention are described in FIG. 1F when the base station transmits a handover command message 1f-20 to the terminal. For example, in an RRCReconfiguration message), indicators for embodiments of the handover procedure for minimizing data interruption time proposed in the present invention can be defined, and the handover procedure corresponding to which embodiment is triggered can be indicated to the terminal , The terminal may perform a handover procedure according to the handover method indicated in the handover command message and perform handover to the target base station while minimizing data interruption time. In addition, in the handover command message (e.g., RRCReconfiguration message), indicators for the embodiments of the PDCP layer device procedure of the handover procedure for minimizing data interruption time proposed in the present invention are defined for each bearer or for each PDCP layer device, and It is possible to instruct the terminal whether to trigger the PDCP layer procedure corresponding to an embodiment, and to cause the terminal to perform the indicated PDCP layer procedure.

In the following of the present invention, a first embodiment of a PDCP layer device procedure that supports a handover procedure for minimizing data interruption time proposed in the present invention is proposed.

In the first embodiment of the PDCP layer device procedure proposed by the present invention, specific operations of a transmitting PDCP entity and a receiving PDCP entity are as follows. The first embodiment may be referred to as a PDCP re-establishment procedure.

First implementation of the PDCP layer device procedure when a higher layer device (for example, an RRC layer device) requests the first embodiment of the PDCP layer device procedure for a certain bearer or when the terminal receives a handover command message or an RRCReconfiguration message If yes is indicated by the indicator, the transmitting PDCP layer device performs the following procedure.

One. If there is no indication to continue to use the header compression protocol for UM DRBs and AM DRBs, the header compression protocol is initialized and started in U (Unidirectional) mode in the IR (Initialization and Refresh) state.

2. For UM DRBs and SRBs, a window state variable (eg TX_NEXT) is set as an initial value.

3. For SRBs, all stored data (eg PDCP SDUs or PDCP PDUs) are discarded. (Because they are RRC messages that were generated to be transmitted to the source base station, discarded to avoid transmission to the target base station)

4. A new security key and encryption algorithm received from an upper layer device (for example, an RRC layer device) is applied.

5. A new security key and integrity protection algorithm received from an upper layer device (for example, an RRC layer device) are applied.

6. For UM DRBs (all previously stored PDCP PDUs are discarded), for data (e.g. PDCP SDUs) that have already been assigned a PDCP serial number but have not yet been delivered to a lower layer device (e.g., PDCP SDUs) It considers data received from SDAP layer device or TCP/IP layer device) and transmits data in ascending order of the COUNT value (or PDCP serial number) allocated before re-establishment of PDCP. And it does not restart the data discard timer. Specifically, a header compression procedure is newly performed on the data (PDCP SDU), an integrity procedure or an encryption procedure is performed again, a PDCP header is configured and transmitted to a lower layer device.

7. For AM DRBs (all previously stored PDCP PDUs are discarded), the first data (e.g. PDCP SDU) for which successful delivery from lower layers (e.g., RLC layer devices) is not confirmed A header compression procedure is newly performed on the data in ascending order of the COUNT value (or PDCP serial number) allocated before establishment, the integrity procedure or encryption procedure is performed again, and the PDCP header is configured and transmitted to the lower layer device for retransmission or Perform the transfer. That is, cumulative retransmission is performed from the first data that has not been successfully delivered.

First implementation of the PDCP layer device procedure when a higher layer device (for example, an RRC layer device) requests the first embodiment of the PDCP layer device procedure for a certain bearer or when the terminal receives a handover command message or an RRCReconfiguration message If yes is indicated by the indicator, the receiving PDCP layer device performs the following procedure.

One. Processes data (eg PDCP PDUs) received from lower layer devices due to re-establishment of lower layer devices (eg RLC layer devices).

2. Discard all stored data (eg PDCP SDUs or PDCP PDUs) for SRBs (discard because they are RRC messages received from the source base station)

3. If the rearrangement timer is running for SRBs and UM DRBs, the timer is stopped and reset. For UM DRBs, header decompression procedure is performed on all stored data (e.g. PDCP SDUs), and Deliver.

4. For AM DRBs, if there is no indication to continue using the header decompression protocol, a header decompression procedure is performed on stored data (eg, PDCP SDUs).

5. If there is no indication to continue using the header compression decompression protocol for UM DRBs and AM DRBs, the downlink header decompression protocol is initialized and starts in U (Uni-directional) mode in the NC (No Context) state.

6. For UM DRBs and SRBs, window variables (for example, RX_NEXT and RX_DELIV) are set as initial values.

7. A new security key and encryption/decryption algorithm received from an upper layer device (eg, an RRC layer device) are applied.

8. Apply a new security key and integrity protection/verification algorithm received from an upper layer device (eg, an RRC layer device).

In the following of the present invention, a second embodiment of a PDCP layer device procedure that supports a handover procedure for minimizing data interruption time proposed in the present invention is proposed.

In the second embodiment of the PDCP layer device procedure proposed by the present invention, specific operations of a transmitting PDCP layer device and a receiving PDCP layer device are as follows. The second embodiment may be referred to as a PDCP data recovery procedure.

Second implementation of the PDCP layer device procedure when a higher layer device (e.g., RRC layer device) requests the second embodiment of the PDCP layer device procedure for a certain bearer or when the terminal receives a handover command message or RRCReconfiguration message If yes is indicated by the indicator, the transmitting PDCP layer device performs the following procedure.

One. When requesting a PDCP data recovery procedure from an upper layer device (eg, an RRC layer device) for AM DRBs, the transmitting PDCP layer device performs the following procedure.

A. Successful delivery from lower layer devices (e.g., RLC layer devices) among data (e.g. PDCP PDUs) that had previously been transmitted to the re-established AM mode RLC layer device or disconnected AM mode RLC layer device ( RLC ACK) is selectively retransmitted in ascending order of the COUNT value (or PDCP serial number) only for all data not confirmed. In the above, transmission and retransmission may be performed by generating data for data previously stored in a buffer or for data that has not yet been generated.

In the following of the present invention, a third embodiment of a PDCP layer device procedure that supports a handover procedure for minimizing data interruption time proposed in the present invention is proposed.

In the third embodiment of the PDCP layer device procedure proposed by the present invention, specific operations of a transmitting PDCP layer device and a receiving PDCP layer device are as follows. The third embodiment may be referred to as a PDCP continue procedure and may be referred to as another name. In addition, the third embodiment may be composed of a 3-1 embodiment and a 3-2 embodiment.

When a higher layer device (e.g., an RRC layer device) requests an embodiment 3-1 of the PDCP layer device procedure for a certain bearer, or when the terminal receives a handover command message or an RRCReconfiguration message, the PDCP layer device procedure is proposed. If the 3-1 embodiment is indicated by the indicator, the transmitting PDCP layer device may perform one or more than one of the following plurality of procedures. As another method, if there is an indication in the handover command message to apply the fourth embodiment or the fifth embodiment proposed in the present invention in handover, one or two or more of the plurality of procedures of the following embodiment 3-1 Can perform.

One. If there is no indication to continue to use the header compression protocol for UM DRBs and AM DRBs, the header compression protocol is initialized and started in U (Unidirectional) mode in the IR (Initialization and Refresh) state.

2. In order to minimize the data interruption time, the window variable (eg TX_NEXT) is not initialized for the UM DRBs because data transmission will be continuously performed to the source base station and the target base station.

3. If a handover command message is received from the source base station, it will no longer transmit and receive RRC messages with the source base station. Therefore, for SRBs, a window state variable (eg TX_NEXT) can be set as an initial value. SRBs for can be released. In addition, for SRBs of the second bearer of the target base station, a window state variable (eg, TX_NEXT) may be set as an initial value. In another way, by maintaining the SRB connection with the source base station, if the terminal fails to handover to the target base station, a handover failure message or an RRC connection re-establishment message or an RRC connection recovery request message is transmitted to the SRB of the source base station. Transmission delay due to handover failure can be reduced. As another method, when maintaining the SRB connection with the source base station in the above, the data stored in the SRB (PDCP SDU or PDCP PDu) is discarded, and the window state variable (for example, TX_NEXT) is set as an initial value. When transmitting a handover failure message, an RRC connection re-establishment message, or an RRC connection recovery request message to the SRB, it is possible to prevent a PDCP serial number gap from occurring.

4. If a handover command message is received from the source base station, it will no longer transmit and receive RRC messages with the source base station. Therefore, all stored data (eg PDCP SDUs or PDCP PDUs) for SRBs is discarded. (Because they are RRC messages that were generated to be transmitted to the source base station, discarded to avoid transmission to the target base station)

5. It is possible to store and prepare a new security key and encryption algorithm received from an upper layer device (for example, an RRC layer device), and apply it to the PDCP layer device of the second bearer for the target base station and apply it to data. In addition, the old security key and encryption algorithm used before receiving the new security key and encryption algorithm from the higher layer device can be continuously applied to the PDCP layer device of the first bearer for the source base station and applied to the data.

6. A new security key and integrity protection algorithm received from an upper layer device (for example, an RRC layer device) can be stored and prepared, and applied to the PDCP layer device of the second bearer for the target base station and applied to the data. . In addition, the old security key and integrity protection algorithm used before receiving the new security key and integrity protection algorithm from the higher layer device can be continuously applied to the PDCP layer device of the first bearer for the source base station and applied to the data.

7. If necessary, set, or indicated or always, the PDCP status report may be transmitted to the source base station to report the current data transmission/reception status (eg, whether data is successfully received).

8. If the user data compression procedure (e.g., Uplink data compression) is configured in the terminal, the terminal may initialize a buffer for the user data compression procedure for the source base station or the target base station (pre-set information in another way ( If there is a Pre-defined dictionary), the buffer can be initialized with the dictionary information). Alternatively, if there is no indication to continue using the buffer contents for the user data compression procedure, the buffer can be initialized.(Another way, if there is pre-defined dictionary, the buffer is initialized with the dictionary information. You may). In addition, user data compression settings for the target base station may be applied or the buffer may be initialized.

When a higher layer device (e.g., an RRC layer device) requests an embodiment 3-1 of the PDCP layer device procedure for a certain bearer, or when the terminal receives a handover command message or an RRCReconfiguration message, the PDCP layer device procedure is proposed. If the 3-1 embodiment is indicated by the indicator, the receiving PDCP layer device may perform one or two or more of the following procedures. As another method, if there is an indication in the handover command message to apply the fourth embodiment or the fifth embodiment proposed in the present invention in handover, one or two or more of the plurality of procedures of the following embodiment 3-1 Can perform.

One. If a handover command message is received from the source base station, all stored data (eg, PDCP SDUs or PDCP PDUs) for SRBs is discarded because it will no longer transmit and receive RRC messages with the source base station. (This is discarded because they are RRC messages received from the source base station) And if the reorder timer is running, it can be stopped. Alternatively, SRBs for the source base station may be released. In addition, window variables (eg, RX_NEXT and RX_DELIV) for SRBs of the second bearer for the target base station may be set as initial values, and if the reorder timer is running, it may be stopped. In another way, by maintaining the SRB connection with the source base station, if the terminal fails to handover to the target base station, a handover failure message or an RRC connection re-establishment message or an RRC connection recovery request message is transmitted to the SRB of the source base station. Transmission delay due to handover failure can be reduced. As another method, when maintaining the SRB connection with the source base station above, the data stored in the SRB (PDCP SDU or PDCP PDu) is discarded, and the window state variable (for example, RX_NEXT) is set as an initial value to When transmitting a handover failure message, an RRC connection re-establishment message, or an RRC connection recovery request message to the SRB, it is possible to prevent a PDCP serial number gap from occurring.

2. Since data transmission/reception is not interrupted and data will be continuously received from the source base station or the target base station, separate processing of data stored for UM DRBs is not required.

3. If the rearrangement timer is running for SRBs and UM DRBs, the timer is stopped and reset. For UM DRBs, header decompression procedure is performed on all stored data (e.g. PDCP SDUs), and Deliver.

4. For AM DRBs, if there is no indication to continue using the header decompression protocol, a header decompression procedure is performed on stored data (eg, PDCP SDUs).

5. If there is no indication to continue using the header compression decompression protocol for UM DRBs and AM DRBs, the downlink header decompression protocol is initialized and starts in U (Uni-directional) mode in the NC (No Context) state.

6. Since data transmission/reception will not be interrupted and data will be continuously received from the source base station or the target base station, window variables (for example, RX_NEXT and RX_DELIV) are not set as initial values for UM DRBs.

7. It is possible to store and prepare a new security key and encryption algorithm received from an upper layer device (for example, an RRC layer device), and apply it to the PDCP layer device of the second bearer for the target base station and apply it to data. In addition, the old security key and encryption algorithm used before receiving the new security key and encryption algorithm from the higher layer device can be continuously applied to the PDCP layer device of the first bearer for the source base station and applied to the data.

8. A new security key and integrity protection algorithm received from an upper layer device (for example, an RRC layer device) can be stored and prepared, and applied to the PDCP layer device of the second bearer for the target base station and applied to the data. . In addition, the old security key and integrity protection algorithm used before receiving the new security key and integrity protection algorithm from the higher layer device can be continuously applied to the PDCP layer device of the first bearer for the source base station and applied to the data.

9. When receiving the PDCP status report, the current data transmission/reception status (eg, whether data has been successfully received) with the source base station or the target base station may be read and reflected in data transmission or retransmission. For example, transmission or retransmission may not be performed on data for which successful delivery is confirmed.

10. If the user data compression procedure (e.g., Uplink data compression) is configured in the terminal, the terminal may initialize a buffer for the user data compression procedure for the source base station or the target base station (pre-set information in another way ( If there is a Pre-defined dictionary), the buffer can be initialized with the dictionary information). Alternatively, if there is no indication to continue using the buffer contents for the user data compression procedure, the buffer can be initialized.(Another way, if there is pre-defined dictionary, the buffer is initialized with the dictionary information. You may). In addition, user data compression settings for the target base station may be applied or the buffer may be initialized.

If a higher layer device (e.g., RRC layer device) requests embodiment 3-2 of the PDCP layer device procedure for a certain bearer or satisfies the third condition, the transmitting PDCP layer device of the terminal implements 3-2 An example is performed, and in detail, one or two or more of the following plurality of procedures may be performed.

One. A new security key and encryption algorithm received and stored from an upper layer device (eg, an RRC layer device) may be applied to the PDCP layer device of the second bearer for the target base station and applied to data. Also, before receiving the new security key and encryption algorithm from the higher layer device, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station may be released or discarded. As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be released for the uplink and kept for the downlink and applied to the received downlink data. . As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be discarded or released when the connection with the source base station (for example, receiving downlink data) is completely released. In addition, it can be continuously applied to data received or transmitted from the source base station before the connection with the source base station is completely released.

2. A new security key and an integrity verification algorithm received and stored from an upper layer device (eg, an RRC layer device) may be applied to the PDCP layer device of the second bearer for the target base station and applied to data. Also, before receiving the new security key and integrity verification algorithm from the higher layer device, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station may be released or discarded. As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be released for the uplink and kept for the downlink and applied to the received downlink data. . As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be discarded or released when the connection with the source base station (for example, receiving downlink data) is completely released. In addition, it can be continuously applied to data received or transmitted from the source base station before the connection with the source base station is completely released.

3. If necessary, set, or indicated or always, the PDCP status report may be transmitted to the source base station or the target base station to report the current data transmission/reception status (eg, whether data is successfully received).

4. For UM DRBs (all previously stored PDCP PDUs are discarded), for data (e.g. PDCP SDUs) that have already been assigned a PDCP serial number but have not yet been delivered to a lower layer device (e.g., PDCP SDUs) It considers data received from SDAP layer device or TCP/IP layer device) and transmits data in ascending order of the COUNT value (or PDCP serial number) allocated before re-establishment of PDCP. And it does not restart the data discard timer. Specifically, a header compression procedure is newly performed on the data (PDCP SDU), an integrity procedure or an encryption procedure is performed again, a PDCP header is configured and transmitted to a lower layer device.

5. For AM DRBs (all previously stored PDCP PDUs are discarded), the first data (e.g. PDCP SDU) for which successful delivery from lower layers (e.g., RLC layer devices) is not confirmed A header compression procedure is newly performed on the data in ascending order of the COUNT value (or PDCP serial number) allocated before establishment (or before the third condition is satisfied or before the RRC message is indicated), and integrity The procedure or encryption procedure is performed again, and the PDCP header is configured and transmitted to the lower layer device to perform retransmission or transmission. That is, cumulative retransmission is performed from the first data that has not been successfully delivered. Alternatively, when retransmission is performed in the above, retransmission may be performed only on data for which successful delivery has not been confirmed from lower layers (eg, RLC layer devices). More specifically, for AM DRBs (all the PDCP PDUs previously stored for transmission to the source base station through the first protocol layer device connected to the PDCP layer device are discarded), the first for transmitting data to the source base station. Lower layers (e.g., RLC layer devices) that are the first protocol layer devices for releasing the lower layers (e.g., RLC layer devices or MAC layer devices), which are protocol layer devices of, and transmitting data to the source base station From the first data (e.g. PDCP SDU) for which successful delivery is not confirmed from, the COUNT value (or PDCP) allocated to before re-establishment of PDCP (or before satisfying the third condition or before the RRC message is indicated) Serial number), a new header or data compression procedure is performed by applying the security key or header compression (or data compression) protocol context corresponding to the target base station to the data in ascending order, and the integrity procedure or encryption procedure is performed again. The PDCP header is configured and transmitted to a lower layer device, which is a second protocol layer device for transmission to a target base station, to perform retransmission or transmission. That is, cumulative retransmission is performed from the first data that has not been successfully delivered. As another method, when performing retransmission in the above, target only data for which successful delivery has not been confirmed from lower layers (e.g., RLC layer devices), which are the first protocol layer devices for transmitting data to the source base station. It is also possible to perform selective retransmission by transferring to a lower layer device, which is a second protocol layer device for transmission to the base station. Alternatively, the transmission or retransmission operation may be performed by releasing lower layers (eg, RLC layer devices or MAC layer devices), which are the first protocol layer devices for transmitting data to the source base station.

6. If the user data compression procedure (e.g., Uplink data compression) is configured in the terminal, the terminal may initialize a buffer for the user data compression procedure for the source base station or the target base station (pre-set information in another way ( If there is a Pre-defined dictionary), the buffer can be initialized with the dictionary information). In addition, the user data compression setting for the source base station may be released or the buffer may be released.

When a higher layer device (e.g., an RRC layer device) requests the 3-2 embodiment of the PDCP layer device procedure for a certain bearer or satisfies the third condition, the receiving PDCP layer device of the terminal implements 3-2 An example is performed, and in detail, one or two or more of the following plurality of procedures may be performed.

One. If there are data (eg PDCP PDUs) received from lower layer devices due to re-establishment of lower layer devices (eg RLC layer devices), processing is performed.

2. Since data transmission/reception is not interrupted and data will be continuously received from the source base station or the target base station, separate processing of data stored for UM DRBs is not required.

3. Since data transmission/reception is not interrupted and data will be continuously received from the source base station or the target base station, window variables (for example, RX_NEXT and RX_DELIV) are not set as initial values for the AM DRB or UM DRBs.

4. A new security key and encryption algorithm received and stored from an upper layer device (eg, an RRC layer device) may be applied to the PDCP layer device of the second bearer for the target base station and applied to data. In addition, if downlink data will no longer be received from the source base station, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station before receiving the new security key and encryption algorithm from the higher layer device It can also be released or discarded. As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be released for the uplink and kept for the downlink and applied to the received downlink data. . As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be discarded or released when the connection with the source base station (for example, receiving downlink data) is completely released. In addition, it can be continuously applied to data received or transmitted from the source base station before the connection with the source base station is completely released.

5. A new security key and an integrity verification algorithm received and stored from an upper layer device (eg, an RRC layer device) may be applied to the PDCP layer device of the second bearer for the target base station and applied to data. Also, if downlink data will no longer be received from the source base station, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station before receiving the new security key and integrity verification algorithm from the higher layer device. May be released or discarded. As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be released for the uplink and kept for the downlink and applied to the received downlink data. . As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be discarded or released when the connection with the source base station (for example, receiving downlink data) is completely released. In addition, it can be continuously applied to data received or transmitted from the source base station before the connection with the source base station is completely released.

6. When receiving the PDCP status report, the current data transmission/reception status (eg, whether data has been successfully received) with the source base station or the target base station may be read and reflected in data transmission or retransmission. For example, transmission or retransmission may not be performed on data for which successful delivery is confirmed.

7. If the user data compression procedure (e.g., Uplink data compression) is configured in the terminal, the terminal may initialize a buffer for the user data compression procedure for the source base station or the target base station (pre-set information in another way ( If there is a Pre-defined dictionary), the buffer can be initialized with the dictionary information). In addition, the user data compression setting for the source base station may be released or the buffer may be released.

In the above, the third condition may be one of the following conditions.

- When the terminal performs a random access procedure to the target base station through the layer devices 1j-21 of the second bearer and receives a random access response

- When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

- When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits data for the first time through the PUCCH or PUSCH uplink transmission resource

- When the base station sets a separate timer as an RRC message to the terminal, and the timer expires

* The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response from the target base station is received, or the handover is completed to the target base station. It may be started when a message is transmitted or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

-After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed. When confirmed by MAC layer device (HARQ ACK) or RLC layer device (RLC ACK)

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

- When the terminal receives an indication to switch the uplink from the target base station to the target base station (eg, an RRC message (eg, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When the terminal receives an indication to switch the uplink from the source base station to the target base station (eg, an RRC message (eg, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When the terminal receives an instruction to release the connection with the source base station from the target base station (eg, an RRC message (eg, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When the terminal receives an instruction to release the connection with the source base station from the source base station (for example, an RRC message (for example, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When the terminal releases the connection with the source base station and releases the first protocol layer devices

- If the terminal does not receive downlink data for a predetermined time from the source base station

- When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or uplink to the terminal When a link transmission resource is first indicated

* For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

** When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed, so the allocated in the random access response message Alternatively, when the included or indicated first uplink transmission resource is received, it may be determined that the third condition is satisfied.

* If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

** The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a random access response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using uplink transmission resources, and when a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal randomly accesses the target base station. Since the procedure can be considered to have been successfully completed, the UE monitors the PDCCH afterwards, and when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE, or the third condition is determined for the first time. You can judge that you are satisfied. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It can be judged that the condition of 3 is satisfied.

- If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

* If the handover command message contains uplink transmission resources for the target base station,

** When the terminal transmits message 3 (e.g., a handover complete message or an RRCReconfigurationComplete message) as an uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, a random access procedure It may be determined that is successfully completed and it may be determined that the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

* If the handover command message does not contain uplink transmission resources for the target base station

** When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (e.g., handover When a completion message or an RRCReconfigurationComplete message) is transmitted and a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) is received from the base station, it may be determined that the random access procedure has been successfully completed and the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

If the third condition is not satisfied, the third condition can be checked while continuing to perform the existing procedure.

In the following of the present invention, a fourth embodiment of a PDCP layer device procedure that supports a handover procedure for minimizing data interruption time proposed in the present invention is proposed.

In the fourth embodiment of the PDCP layer device procedure proposed in the present invention, specific operations of a transmitting PDCP entity and a receiving PDCP entity are as follows. The fourth embodiment may be referred to as a PDCP continue procedure (PDCP continue) and may be referred to as another name. In addition, the fourth embodiment may be composed of a 4-1 embodiment and a 4-2 embodiment. In the fourth embodiment, since data transmission/reception is continued, a header compression protocol is not unnecessarily initialized or handled.

When a higher layer device (e.g., an RRC layer device) requests the 4-1 embodiment of the PDCP layer device procedure for a certain bearer, or when the terminal receives a handover command message or an RRCReconfiguration message, the PDCP layer device procedure is proposed. If the 4-1 embodiment is indicated by the indicator, the transmitting PDCP layer device may perform one or more than one of the following plurality of procedures. As another method, if there is an indication in the handover command message to apply the fourth embodiment or the fifth embodiment proposed in the present invention in handover, one or two or more of the plurality of procedures of the following embodiment 4-1 Can perform.

One. In order to minimize the data interruption time, the window variable (eg TX_NEXT) is not initialized for the UM DRBs because data transmission will be continuously performed to the source base station and the target base station.

2. If a handover command message is received from the source base station, it will no longer transmit and receive RRC messages with the source base station. Therefore, for SRBs, a window state variable (eg TX_NEXT) can be set as an initial value. SRBs for can be released. In addition, for SRBs of the second bearer of the target base station, a window state variable (eg, TX_NEXT) may be set as an initial value.

3. If a handover command message is received from the source base station, it will no longer transmit and receive RRC messages with the source base station. Therefore, all stored data (eg PDCP SDUs or PDCP PDUs) for SRBs is discarded. (Because they are RRC messages that were generated to be transmitted to the source base station, discarded in order not to transmit to the target base station) As another method, if the UE fails to handover to the target base station by maintaining the SRB connection with the source base station, the source base station Transmission delay due to handover failure can be reduced by transmitting a handover failure message, an RRC connection re-establishment message, or an RRC connection recovery request message to the SRB of. As another method, when maintaining the SRB connection with the source base station in the above, the data stored in the SRB (PDCP SDU or PDCP PDU) is discarded, and the window state variable (for example, TX_NEXT) is set as an initial value. When transmitting a handover failure message, an RRC connection re-establishment message, or an RRC connection recovery request message to the SRB, it is possible to prevent a PDCP serial number gap from occurring.

4. It is possible to store and prepare a new security key and encryption algorithm received from an upper layer device (for example, an RRC layer device), and apply it to the PDCP layer device of the second bearer for the target base station and apply it to data. In addition, the old security key and encryption algorithm used before receiving the new security key and encryption algorithm from the higher layer device can be continuously applied to the PDCP layer device of the first bearer for the source base station and applied to the data.

5. A new security key and integrity protection algorithm received from an upper layer device (for example, an RRC layer device) can be stored and prepared, and applied to the PDCP layer device of the second bearer for the target base station and applied to the data. . In addition, the old security key and integrity protection algorithm used before receiving the new security key and integrity protection algorithm from the higher layer device can be continuously applied to the PDCP layer device of the first bearer for the source base station and applied to the data.

6. If necessary, set, or indicated or always, the PDCP status report may be transmitted to the source base station to report the current data transmission/reception status (eg, whether data is successfully received).

7. If the user data compression procedure (e.g., Uplink data compression) is configured in the terminal, the terminal may initialize a buffer for the user data compression procedure for the source base station or the target base station (pre-set information in another way ( If there is a Pre-defined dictionary), the buffer can be initialized with the dictionary information). Alternatively, if there is no indication to continue using the buffer contents for the user data compression procedure, the buffer can be initialized.(Another way, if there is pre-defined dictionary, the buffer is initialized with the dictionary information. You may). In addition, user data compression settings for the target base station may be applied or the buffer may be initialized.

When a higher layer device (e.g., an RRC layer device) requests the 4-1 embodiment of the PDCP layer device procedure for a certain bearer, or when the terminal receives a handover command message or an RRCReconfiguration message, the PDCP layer device procedure is proposed. If the 4-1 embodiment is indicated by the indicator, the receiving PDCP layer device may perform one or two or more of the following procedures. As another method, if there is an indication in the handover command message to apply the fourth embodiment or the fifth embodiment proposed in the present invention in handover, one or two or more of the plurality of procedures of the following embodiment 3-1 Can perform.

One. If a handover command message is received from the source base station, all stored data (eg, PDCP SDUs or PDCP PDUs) for SRBs is discarded because it will no longer transmit and receive RRC messages with the source base station. (This is discarded because they are RRC messages received from the source base station) And if the reorder timer is running, it can be stopped. Alternatively, SRBs for the source base station may be released. In addition, window variables (eg, RX_NEXT and RX_DELIV) for SRBs of the second bearer for the target base station may be set as initial values, and if the reorder timer is running, it may be stopped. In another way, by maintaining the SRB connection with the source base station, if the terminal fails to handover to the target base station, a handover failure message or an RRC connection re-establishment message or an RRC connection recovery request message is transmitted to the SRB of the source base station. Transmission delay due to handover failure can be reduced. As another method, when maintaining the SRB connection with the source base station above, the data stored in the SRB (PDCP SDU or PDCP PDu) is discarded, and the window state variable (for example, RX_NEXT) is set as an initial value to When transmitting a handover failure message, an RRC connection re-establishment message, or an RRC connection recovery request message to the SRB, it is possible to prevent a PDCP serial number gap from occurring.

2. Since data transmission/reception is not interrupted and data will be continuously received from the source base station or the target base station, separate processing of data stored for UM DRBs is not required.

3. Since data transmission/reception will not be interrupted and data will be continuously received from the source base station or the target base station, window variables (for example, RX_NEXT and RX_DELIV) are not set as initial values for UM DRBs.

4. It is possible to store and prepare a new security key and encryption algorithm received from an upper layer device (for example, an RRC layer device), and apply it to the PDCP layer device of the second bearer for the target base station and apply it to data. In addition, the old security key and encryption algorithm used before receiving the new security key and encryption algorithm from the higher layer device can be continuously applied to the PDCP layer device of the first bearer for the source base station and applied to the data.

5. A new security key and integrity protection algorithm received from an upper layer device (for example, an RRC layer device) can be stored and prepared, and applied to the PDCP layer device of the second bearer for the target base station and applied to the data. . In addition, the old security key and integrity protection algorithm used before receiving the new security key and integrity protection algorithm from the higher layer device can be continuously applied to the PDCP layer device of the first bearer for the source base station and applied to the data.

6. When receiving the PDCP status report, the current data transmission/reception status (eg, whether data has been successfully received) with the source base station or the target base station may be read and reflected in data transmission or retransmission. For example, transmission or retransmission may not be performed on data for which successful delivery is confirmed.

7. If the user data compression procedure (e.g., Uplink data compression) is configured in the terminal, the terminal may initialize a buffer for the user data compression procedure for the source base station or the target base station (pre-set information in another way ( If there is a Pre-defined dictionary), the buffer can be initialized with the dictionary information). Alternatively, if there is no indication to continue using the buffer contents for the user data compression procedure, the buffer can be initialized.(Another way, if there is pre-defined dictionary, the buffer is initialized with the dictionary information. You may). In addition, user data compression settings for the target base station may be applied or the buffer may be initialized.

When a higher layer device (for example, an RRC layer device) requests the 4-2 embodiment of the PDCP layer device procedure for a certain bearer or satisfies the third condition, the transmitting PDCP layer device of the terminal implements 4-2 An example is performed, and in detail, one or two or more of the following plurality of procedures may be performed.

One. A new security key and encryption algorithm received and stored from an upper layer device (eg, an RRC layer device) may be applied to the PDCP layer device of the second bearer for the target base station and applied to data. Also, before receiving the new security key and encryption algorithm from the higher layer device, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station may be released or discarded. As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be released for the uplink and kept for the downlink and applied to the received downlink data. . As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be discarded or released when the connection with the source base station (for example, receiving downlink data) is completely released. In addition, it can be continuously applied to data received or transmitted from the source base station before the connection with the source base station is completely released.

2. A new security key and an integrity verification algorithm received and stored from an upper layer device (eg, an RRC layer device) may be applied to the PDCP layer device of the second bearer for the target base station and applied to data. Also, before receiving the new security key and integrity verification algorithm from the higher layer device, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station may be released or discarded. As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be released for the uplink and kept for the downlink and applied to the received downlink data. . As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be discarded or released when the connection with the source base station (for example, receiving downlink data) is completely released. In addition, it can be continuously applied to data received or transmitted from the source base station before the connection with the source base station is completely released.

3. If necessary, set, or indicated or always, the PDCP status report may be transmitted to the source base station or the target base station to report the current data transmission/reception status (eg, whether data is successfully received).

4. For UM DRBs (all previously stored PDCP PDUs are discarded), for data (e.g. PDCP SDUs) that have already been assigned a PDCP serial number but have not yet been delivered to a lower layer device (e.g., PDCP SDUs) It considers data received from SDAP layer device or TCP/IP layer device) and transmits data in ascending order of the COUNT value (or PDCP serial number) allocated before re-establishment of PDCP. And it does not restart the data discard timer. Specifically, a header compression procedure is newly performed on the data (PDCP SDU), an integrity procedure or an encryption procedure is performed again, a PDCP header is configured and transmitted to a lower layer device.

5. For AM DRBs (all previously stored PDCP PDUs are discarded), the first data (e.g. PDCP SDU) for which successful delivery from lower layers (e.g., RLC layer devices) is not confirmed A header compression procedure is newly performed on the data in ascending order of the COUNT value (or PDCP serial number) allocated before establishment (or before the third condition is satisfied or before the RRC message is indicated), and integrity The procedure or encryption procedure is performed again, and the PDCP header is configured and transmitted to the lower layer device to perform retransmission or transmission. That is, cumulative retransmission is performed from the first data that has not been successfully delivered. Alternatively, when retransmission is performed in the above, retransmission may be performed only on data for which successful delivery has not been confirmed from lower layers (eg, RLC layer devices). More specifically, for AM DRBs (all the PDCP PDUs previously stored for transmission to the source base station through the first protocol layer device connected to the PDCP layer device are discarded), the first for transmitting data to the source base station. Lower layers (e.g., RLC layer devices) that are the first protocol layer devices for releasing the lower layers (e.g., RLC layer devices or MAC layer devices), which are protocol layer devices of, and transmitting data to the source base station From the first data (e.g. PDCP SDU) for which successful delivery is not confirmed from, the COUNT value (or PDCP) allocated to before re-establishment of PDCP (or before satisfying the third condition or before the RRC message is indicated) Serial number), a new header or data compression procedure is performed by applying the security key or header compression (or data compression) protocol context corresponding to the target base station to the data in ascending order, and the integrity procedure or encryption procedure is performed again. The PDCP header is configured and transmitted to a lower layer device, which is a second protocol layer device for transmission to a target base station, to perform retransmission or transmission. That is, cumulative retransmission is performed from the first data that has not been successfully delivered. As another method, when performing retransmission in the above, target only data for which successful delivery has not been confirmed from lower layers (e.g., RLC layer devices), which are the first protocol layer devices for transmitting data to the source base station. It is also possible to perform selective retransmission by transferring to a lower layer device, which is a second protocol layer device for transmission to the base station. Alternatively, the transmission or retransmission operation may be performed by releasing lower layers (eg, RLC layer devices or MAC layer devices), which are the first protocol layer devices for transmitting data to the source base station.

6. If the user data compression procedure (e.g., Uplink data compression) is configured in the terminal, the terminal may initialize a buffer for the user data compression procedure for the source base station or the target base station (pre-set information in another way ( If there is a Pre-defined dictionary), the buffer can be initialized with the dictionary information). In addition, the user data compression setting for the source base station may be released or the buffer may be released.

When a higher layer device (for example, an RRC layer device) requests the 4-2 embodiment of the PDCP layer device procedure for a certain bearer or satisfies the third condition, the receiving PDCP layer device of the terminal implements 4-2 An example is performed, and in detail, one or two or more of the following plurality of procedures may be performed.

One. If there are data received from lower layer devices (eg PDCP PDUs) due to re-establishment of lower layer devices (eg, RLC layer devices), processing is performed.

2. Since data transmission/reception is not interrupted and data will be continuously received from the source base station or the target base station, separate processing of data stored for UM DRBs is not required.

3. Since data transmission/reception is not interrupted and data will be continuously received from the source base station or the target base station, window variables (for example, RX_NEXT and RX_DELIV) are not set as initial values for the AM DRB or UM DRBs.

4. A new security key and encryption algorithm received and stored from an upper layer device (eg, an RRC layer device) may be applied to the PDCP layer device of the second bearer for the target base station and applied to data. In addition, if downlink data will no longer be received from the source base station, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station before receiving the new security key and encryption algorithm from the higher layer device It can also be released or discarded. As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be released for the uplink and kept for the downlink and applied to the received downlink data. . As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be discarded or released when the connection with the source base station (for example, receiving downlink data) is completely released. In addition, it can be continuously applied to data received or transmitted from the source base station before the connection with the source base station is completely released.

5. A new security key and an integrity verification algorithm received and stored from an upper layer device (eg, an RRC layer device) may be applied to the PDCP layer device of the second bearer for the target base station and applied to data. Also, if downlink data will no longer be received from the source base station, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station before receiving the new security key and integrity verification algorithm from the higher layer device. May be released or discarded. As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be released for the uplink and kept for the downlink and applied to the received downlink data. . As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be discarded or released when the connection with the source base station (for example, receiving downlink data) is completely released. In addition, it can be continuously applied to data received or transmitted from the source base station before the connection with the source base station is completely released.

6. When receiving the PDCP status report, the current data transmission/reception status (eg, whether data has been successfully received) with the source base station or the target base station may be read and reflected in data transmission or retransmission. For example, transmission or retransmission may not be performed on data for which successful delivery is confirmed.

7. If the user data compression procedure (e.g., Uplink data compression) is configured in the terminal, the terminal may initialize a buffer for the user data compression procedure for the source base station or the target base station (pre-set information in another way ( If there is a Pre-defined dictionary), the buffer can be initialized with the dictionary information). In addition, the user data compression setting for the source base station may be released or the buffer may be released.

In the above, the third condition may be one of the following conditions.

- When the terminal performs a random access procedure to the target base station through the layer devices 1j-21 of the second bearer and receives a random access response

- When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

- When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits data for the first time through the PUCCH or PUSCH uplink transmission resource

- When the base station sets a separate timer as an RRC message to the terminal, and the timer expires

* The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response from the target base station is received, or the handover is completed to the target base station. It may be started when a message is transmitted or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

-After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed. When confirmed by MAC layer device (HARQ ACK) or RLC layer device (RLC ACK)

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

- When the terminal receives an indication to switch the uplink from the target base station to the target base station (eg, an RRC message (eg, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When the terminal receives an indication to switch the uplink from the source base station to the target base station (eg, an RRC message (eg, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When the terminal receives an instruction to release the connection with the source base station from the target base station (eg, an RRC message (eg, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When the terminal receives an instruction to release the connection with the source base station from the source base station (for example, an RRC message (for example, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When the terminal releases the connection with the source base station and releases the first protocol layer devices

- If the terminal does not receive downlink data for a predetermined time from the source base station

- When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or uplink to the terminal When a link transmission resource is first indicated

* For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

** When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed, so the allocated in the random access response message Alternatively, when the included or indicated first uplink transmission resource is received, it may be determined that the third condition is satisfied.

* If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

** The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a random access response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using uplink transmission resources, and when a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal randomly accesses the target base station. Since the procedure can be considered to have been successfully completed, the UE monitors the PDCCH afterwards, and when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE, or the third condition is determined for the first time. You can judge that you are satisfied. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It can be judged that the condition of 3 is satisfied.

- If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

* If the handover command message contains uplink transmission resources for the target base station,

** When the terminal transmits message 3 (e.g., a handover complete message or an RRCReconfigurationComplete message) as an uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, a random access procedure It may be determined that is successfully completed and it may be determined that the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

* If the handover command message does not contain uplink transmission resources for the target base station

** When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the terminal, or when the uplink transmission resource is used, message 3 (e.g., a handover completion message Alternatively, if the RRCReconfigurationComplete message) is transmitted and a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) is received from the base station, it may be determined that the random access procedure has been successfully completed, and the first condition may be satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

If the third condition is not satisfied, the third condition can be checked while continuing to perform the existing procedure.

In the following of the present invention, a fifth embodiment of a PDCP layer device procedure that supports a handover procedure for minimizing data interruption time proposed in the present invention is proposed.

In the fifth embodiment of the PDCP layer device procedure proposed by the present invention, specific operations of a transmitting PDCP entity and a receiving PDCP entity are as follows. The fifth embodiment may be referred to as a PDCP continue procedure (PDCP continue) and may be referred to as another name. In addition, the fifth embodiment may be composed of a 5-1 embodiment and a 5-2 embodiment.

In the fifth embodiment of the PDCP layer device procedure of the present invention, lower PDCP layer devices (1k-21, 1k-22) in the PDCP layer device structure as shown in FIG. 1K are provided with different header compression protocol contexts ( For example, based on ROHC context), each header compression procedure may be performed, and each encryption procedure may be performed using a different security key.

Specifically, the first lower PDCP layer device 1k-21 performs a header compression procedure on data (eg, PDCP SDU) received from an upper layer based on the first header compression protocol context (eg, ROHC context). Applicable, and the data may be encrypted using a first security key (a security key set from a source base station or a target base station). In addition, the second lower PDCP layer device (1k-22) applies a header compression procedure to data (eg PDCP SDU) received from an upper layer based on the second header compression protocol context (eg, ROHC context). The data can be encrypted using a second security key (a security key set by the source base station or the target base station). The two lower PDCP layer devices may reduce data processing time by performing a header compression procedure and an encryption procedure in parallel, and may reduce data interruption time that may occur during handover.

In the fifth embodiment of the PDCP layer device procedure of the present invention, the lower PDCP layer devices 1k-21 and 1k-22 in the PDCP layer device structure as shown in FIG. 1K use different security keys for received data. Each decryption procedure may be performed, and each header decompression procedure may be performed with different header compression protocol contexts (eg, ROHC context).

Specifically, the first lower PDCP layer device 1k-21 performs a header decompression procedure on data (eg, PDCP SDU) received from the lower layer based on the first header compression protocol context (eg, ROHC context). May be applied, and the data may be decrypted using a first security key (a security key set from a source base station or a target base station). In addition, the second lower PDCP layer device (1k-22) performs a header decompression procedure on the data received from the lower layer (eg, PDCP SDU) based on the second header compression protocol context (eg, ROHC context). Applicable, and the data can be decrypted using a second security key (a security key set by the source base station or the target base station). The two lower PDCP layer devices may reduce data processing time by performing a header decompression procedure and a decoding procedure in parallel, and may reduce a data interruption time that may occur during handover.

In the above-described PDCP layer device structure, if a higher layer device (for example, an RRC layer device) requests an embodiment 5-1 of the PDCP layer device procedure for a certain bearer, or the terminal sends a handover command message or an RRCReconfiguration message. When received, if the 5-1 embodiment of the PDCP layer device procedure is indicated by an indicator, the transmitting PDCP layer device may perform one or two or more of the following procedures. As another method, if there is an indication in the handover command message to apply the fourth embodiment or the fifth embodiment proposed in the present invention in handover, one or two or more of the plurality of procedures of the following embodiment 3-1 Can perform.

1. In order to minimize the data interruption time, the window variable (eg TX_NEXT) is not initialized for the UM DRBs because data transmission will continue to be performed to the source base station.

2. If a handover command message is received from the source base station, since the RRC message will no longer be transmitted and received with the source base station, the window state variable (eg TX_NEXT) can be set as an initial value for the SRBs or for the source base station. SRBs can be released. In addition, for SRBs of the second bearer of the target base station, a window state variable (eg, TX_NEXT) may be set as an initial value.

3. If a handover command message is received from the source base station, all stored data (for example, PDCP SDUs or PDCP PDUs) are discarded for SRBs because the RRC message will no longer be transmitted and received with the source base station. (Because they are RRC messages that were generated to be transmitted to the source base station, discarded in order not to transmit to the target base station) As another method, if the UE fails to handover to the target base station by maintaining the SRB connection with the source base station, the source base station Transmission delay due to handover failure can be reduced by transmitting a handover failure message, an RRC connection re-establishment message, or an RRC connection recovery request message to the SRB of. As another method, when maintaining the SRB connection with the source base station in the above, the data stored in the SRB (PDCP SDU or PDCP PDu) is discarded, and the window state variable (for example, TX_NEXT) is set as an initial value. When transmitting a handover failure message, an RRC connection re-establishment message, or an RRC connection recovery request message to the SRB, it is possible to prevent a PDCP serial number gap from occurring.

4. It is possible to store and prepare a new security key and encryption algorithm received from an upper layer device (eg, RRC layer device), and a PDCP layer device (eg, a second lower level device) of a second bearer for the target base station. PDCP layer device) and can be applied to data later. In addition, the old security key and encryption algorithm used before receiving the new security key and encryption algorithm from the higher layer device continues to the PDCP layer device (for example, the first lower PDCP layer device) of the first bearer for the source base station. Apply and apply to your data.

5. It is possible to store and prepare a new security key and integrity protection algorithm received from an upper layer device (eg, an RRC layer device), and a PDCP layer device (eg, a second bearer) for the target base station. It can be applied to lower PDCP layer devices) and applied to data later. In addition, the old security key and integrity protection algorithm used before receiving the new security key and integrity protection algorithm from the upper layer device is the PDCP layer device of the first bearer for the source base station (for example, the first lower PDCP layer device). Can continue to apply to and apply to data.

6. If necessary, set, or instructed or always, the PDCP status report can be transmitted to the source base station to report the current data transmission/reception status (eg, whether data has been successfully received).

7. If the user data compression procedure (e.g., Uplink data compression) is configured in the terminal, the terminal may initialize a buffer for the user data compression procedure for the source base station or the target base station (pre-set information in another way ( If there is a Pre-defined dictionary), the buffer can be initialized with the dictionary information). Alternatively, if there is no indication to continue using the buffer contents for the user data compression procedure, the buffer can be initialized.(Another way, if there is pre-defined dictionary, the buffer is initialized with the dictionary information. You may). In addition, user data compression settings for the target base station may be applied or the buffer may be initialized.

When a higher layer device (for example, an RRC layer device) requests the 5-1 embodiment of the PDCP layer device procedure for a certain bearer, or when the terminal receives a handover command message or an RRCReconfiguration message, the PDCP layer device procedure is proposed. If the 5-1 embodiment is indicated by the indicator, the receiving PDCP layer device may perform one or two or more of the following procedures. As another method, if there is an indication in the handover command message to apply the fourth embodiment or the fifth embodiment proposed in the present invention in handover, one or two or more of the plurality of procedures of the following embodiment 3-1 Can perform.

1. In the handover command message, if there is no indication to continue using the header compression protocol for each bearer of UM DRBs and AM DRBs, the PDCP layer device of the second bearer for the target base station (e.g., the second lower PDCP Layer device) initializes the header compression protocol, and starts in U (unidirectional) mode in an initialization and refresh (IR) state. If there is an indication to continue using the header compression protocol, the header compression protocol is continuously used by using the header compression protocol of the PDCP layer device of the first bearer for the source base station (for example, the lower PDCP layer device of the first). I can. Alternatively, a header decompression procedure may be performed. In addition, the PDCP layer device (eg, the first lower PDCP layer device) of the first bearer for the source base station may not initialize the header compression protocol and continue to use the header compression protocol context.

2. If a handover command message is received from the source base station, all stored data (for example, PDCP SDUs or PDCP PDUs) for SRBs are discarded because the source base station will no longer transmit and receive RRC messages. Discarded because they are RRC messages received from the base station). And if the reorder timer is running, you can stop it. Alternatively, SRBs for the source base station may be released. In addition, window variables (eg, RX_NEXT and RX_DELIV) for SRBs of the second bearer for the target base station may be set as initial values, and if the reorder timer is running, it may be stopped. In another way, by maintaining the SRB connection with the source base station, if the terminal fails to handover to the target base station, a handover failure message or an RRC connection re-establishment message or an RRC connection recovery request message is transmitted to the SRB of the source base station. Transmission delay due to handover failure can be reduced. As another method, when maintaining the SRB connection with the source base station above, the data stored in the SRB (PDCP SDU or PDCP PDu) is discarded, and the window state variable (for example, RX_NEXT) is set as an initial value to When transmitting a handover failure message, an RRC connection re-establishment message, or an RRC connection recovery request message to the SRB, it is possible to prevent a PDCP serial number gap from occurring.

3. Since data transmission/reception is not interrupted and data will be continuously received from the source base station or the target base station, separate processing of data stored for UM DRBs is not required.

4. If the reorder timer is running for SRBs, you can stop and reset the timer. For AM DRBs, a header for a PDCP layer device (for example, a second (or first) lower PDCP layer device) corresponding to a second (or first) bearer for a target (or source) base station If there is no indication to continue using the decompression protocol, a header decompression procedure is performed for stored data (eg, PDCP SDUs) using the existing header compression protocol context. Then you can initialize the header compression protocol context.

5. If there is no indication to continue using the header decompression protocol for UM DRBs and AM DRBs, a PDCP layer device corresponding to the second (or first) bearer for the target (or source) base station (for example, The downlink header decompression protocol is initialized for the second (or first) lower PDCP layer device), and starts in the U (uni-directional) mode in a no context (NC) state.

6. Do not set the window variables (eg RX_NEXT and RX_DELIV) as initial values for UM DRBs because data transmission/reception will not be interrupted and data will be continuously received from the source or target base station.

7. It is possible to store and prepare a new security key and encryption algorithm received from a higher layer device (for example, an RRC layer device), and apply it to the PDCP layer device of the second bearer for the target base station and to the data. Yes or can perform decryption. In addition, the old security key and encryption algorithm used before receiving the new security key and encryption algorithm from the higher layer device can be continuously applied to the PDCP layer device of the first bearer for the source base station and applied to the data or decryption is performed. can do.

8. It is possible to store and prepare a new security key and integrity protection algorithm received from a higher layer device (for example, an RRC layer device), and apply it to the PDCP layer device of the second bearer for the target base station and apply it to the data. Can or can perform integrity protection. In addition, the old security key and integrity protection algorithm used before receiving the new security key and integrity protection algorithm from the higher layer device can be applied continuously to the PDCP layer device of the first bearer for the source base station and applied to the data or integrity. Protection can be carried out.

9. When the PDCP status report is received, the current data transmission/reception status (eg, whether data has been successfully received) with the source base station or target base station is read, and data transmission or retransmission of the transmitting PDCP layer device to the source base station or target base station Can be reflected in. For example, transmission or retransmission may not be performed on data for which successful delivery is confirmed.

10. If the user data compression procedure (e.g., Uplink data compression) is configured in the terminal, the terminal may initialize a buffer for the user data compression procedure for the source base station or the target base station (pre-set information in another way ( If there is a Pre-defined dictionary), the buffer can be initialized with the dictionary information). Alternatively, if there is no indication to continue using the buffer contents for the user data compression procedure, the buffer can be initialized.(Another way, if there is pre-defined dictionary, the buffer is initialized with the dictionary information. You may). In addition, user data compression settings for the target base station may be applied or the buffer may be initialized.

If a higher layer device (e.g., an RRC layer device) requests embodiment 5-2 of the PDCP layer device procedure for a certain bearer or satisfies the third condition, the transmitting PDCP layer device of the terminal implements 5-2 An example is performed, and in detail, one or two or more of the following plurality of procedures may be performed.

1. In the handover command message, if there is no indication to continue using the header compression protocol for each bearer of UM DRBs and AM DRBs, the PDCP layer device of the second bearer for the target base station (e.g., the second lower PDCP Layer device) initializes the header compression protocol, and starts in U (Unidirectional) mode in the IR (Initialization and Refresh) state. If there is an indication to continue using the header compression protocol, the header compression protocol is continuously used by using the header compression protocol of the PDCP layer device of the first bearer for the source base station (for example, the lower PDCP layer device of the first). Can or can perform header decompression procedure.

2. A new security key and encryption algorithm received and stored from an upper layer device (eg, an RRC layer device) may be applied to the PDCP layer device of the second bearer for the target base station and applied to the data. Also, before receiving the new security key and encryption algorithm from the higher layer device, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station may be released or discarded. As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be released for the uplink and kept for the downlink and applied to the received downlink data. . As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be discarded or released when the connection with the source base station (for example, receiving downlink data) is completely released. In addition, it can be continuously applied to data received or transmitted from the source base station before the connection with the source base station is completely released.

3. A new security key and an integrity verification algorithm received and stored from a higher layer device (eg, an RRC layer device) may be applied to the PDCP layer device of the second bearer for the target base station and applied to the data. Also, before receiving the new security key and integrity verification algorithm from the higher layer device, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station may be released or discarded. As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be released for the uplink and kept for the downlink and applied to the received downlink data. . As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be discarded or released when the connection with the source base station (for example, receiving downlink data) is completely released. In addition, it can be continuously applied to data received or transmitted from the source base station before the connection with the source base station is completely released.

4. If necessary, set, or indicated or always, a PDCP status report can be transmitted to the source base station or the target base station to report the current data transmission/reception status (eg, whether data has been successfully received).

5. For UM DRBs (all previously stored PDCP PDUs are discarded), for data (eg PDCP SDUs) that have already been assigned a PDCP serial number but have not been delivered to a lower layer device (eg PDCP SDUs) For example, the data received from the SDAP layer device or the TCP/IP layer device) are considered, and data transmission is performed in the ascending order of the COUNT value (or PDCP serial number) allocated before the PDCP re-establishment. And it does not restart the data discard timer. Specifically, a header compression procedure is newly performed on the data (PDCP SDU), an integrity procedure or an encryption procedure is performed again, a PDCP header is configured and transmitted to a lower layer device.

6. For AM DRBs (all previously stored PDCP PDUs are discarded) from the first data (eg PDCP SDU) that has not been successfully delivered from lower layers (eg RLC layer devices). PDCP layer of the second bearer for the target base station in ascending order of the COUNT value (or PDCP serial number) allocated before PDCP re-establishment (or before satisfying the third condition or before the RRC message is indicated) The device newly performs a header compression procedure on the data, performs the integrity procedure or the encryption procedure again, configures the PDCP header and delivers it to the lower layer device to perform retransmission or transmission through the second bearer for the target base station. . That is, cumulative retransmission is performed from the first data that has not been successfully delivered. Alternatively, when retransmission is performed in the above, retransmission may be performed only on data for which successful delivery has not been confirmed from lower layers (eg, RLC layer devices). Alternatively, selective retransmission may be performed based on PDCP status report. More specifically, for AM DRBs (all the PDCP PDUs previously stored for transmission to the source base station through the first protocol layer device connected to the PDCP layer device are discarded), the first for transmitting data to the source base station. Lower layers (e.g., RLC layer devices) that are the first protocol layer devices for releasing the lower layers (e.g., RLC layer devices or MAC layer devices), which are protocol layer devices of, and transmitting data to the source base station From the first data (e.g. PDCP SDU) for which successful delivery is not confirmed from, the COUNT value (or PDCP) allocated to before re-establishment of PDCP (or before satisfying the third condition or before the RRC message is indicated) Serial number), a new header or data compression procedure is performed by applying the security key or header compression (or data compression) protocol context corresponding to the target base station to the data in ascending order, and the integrity procedure or encryption procedure is performed again. The PDCP header is configured and transmitted to a lower layer device, which is a second protocol layer device for transmission to a target base station, to perform retransmission or transmission. That is, cumulative retransmission is performed from the first data that has not been successfully delivered. As another method, when performing retransmission in the above, target only data for which successful delivery has not been confirmed from lower layers (e.g., RLC layer devices), which are the first protocol layer devices for transmitting data to the source base station. It is also possible to perform selective retransmission by transferring to a lower layer device, which is a second protocol layer device for transmission to the base station. Alternatively, the transmission or retransmission operation may be performed by releasing lower layers (eg, RLC layer devices or MAC layer devices), which are the first protocol layer devices for transmitting data to the source base station.

7. If the user data compression procedure (e.g., Uplink data compression) is configured in the terminal, the terminal may initialize a buffer for the user data compression procedure for the source base station or the target base station (pre-set information in another way ( If there is a Pre-defined dictionary), the buffer can be initialized with the dictionary information). In addition, the user data compression setting for the source base station may be released or the buffer may be released.

When a higher layer device (for example, an RRC layer device) requests the 5-2 embodiment of the PDCP layer device procedure for a certain bearer or satisfies the third condition, the receiving PDCP layer device of the terminal implements 5-2 An example is performed, and in detail, one or two or more of the following plurality of procedures may be performed.

1. If there are data (eg PDCP PDUs) received from lower layer devices due to re-establishment of lower layer devices (eg RLC layer devices), processing.

2. Since data transmission/reception will not be interrupted and data will be continuously received from the source base station or the target base station, separate processing of data stored for UM DRBs is not required.

3. Do not set the window variables (for example, RX_NEXT and RX_DELIV) as initial values for AM DRB or UM DRBs because data transmission/reception will not be interrupted and data will be continuously received from the source base station or the target base station.

4. A new security key and encryption algorithm received and stored from an upper layer device (eg, an RRC layer device) may be applied to the PDCP layer device of the second bearer for the target base station and applied to data. In addition, if downlink data will no longer be received from the source base station, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station before receiving the new security key and encryption algorithm from the higher layer device It can also be released or discarded. As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be released for the uplink and kept for the downlink and applied to the received downlink data. . As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be discarded or released when the connection with the source base station (for example, receiving downlink data) is completely released. In addition, it can be continuously applied to data received or transmitted from the source base station before the connection with the source base station is completely released.

5. A new security key and an integrity verification algorithm received and stored from an upper layer device (eg, an RRC layer device) may be applied to the PDCP layer device of the second bearer for the target base station and applied to the data. Also, if downlink data will no longer be received from the source base station, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station before receiving the new security key and integrity verification algorithm from the higher layer device. May be released or discarded. As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be released for the uplink and kept for the downlink and applied to the received downlink data. . As another method, the old security key and encryption algorithm applied to the PDCP layer device of the first bearer for the source base station can be discarded or released when the connection with the source base station (for example, receiving downlink data) is completely released. In addition, it can be continuously applied to data received or transmitted from the source base station before the connection with the source base station is completely released.

6. When the PDCP status report is received, the current data transmission/reception status (eg, whether data has been successfully received) with the source base station or the target base station can be read and reflected in data transmission or retransmission. For example, transmission or retransmission may not be performed on data for which successful delivery is confirmed.

7. If the user data compression procedure (e.g., Uplink data compression) is configured in the terminal, the terminal may initialize a buffer for the user data compression procedure for the source base station or the target base station (pre-set information in another way ( If there is a Pre-defined dictionary), the buffer can be initialized with the dictionary information). In addition, the user data compression setting for the source base station may be released or the buffer may be released.

In the above, the third condition may be one of the following conditions.

-When the terminal performs a random access procedure to the target base station through the layer devices 1j-21 of the second bearer and receives a random access response

-When the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station

-When the terminal completes the random access procedure to the target base station through the layer devices of the second bearer and transmits data for the first time through the PUCCH or PUSCH uplink transmission resource

-When the base station sets a separate timer to the terminal in an RRC message, and the timer expires

* The timer is when the terminal receives a handover command message from the source base station or starts random access to the target base station (when a preamble is transmitted), or when a random access response is received from the target base station or handover to the target base station. It may be started when transmitting a completion message or when data is first transmitted through a PUCCH or PUSCH uplink transmission resource.

-After the terminal performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, successful delivery of the handover completion message is performed. When confirmed by MAC layer device (HARQ ACK) or RLC layer device (RLC ACK)

-After the UE performs a random access procedure to the target base station through the layer devices of the second bearer, receives a random access response, constructs and transmits a handover completion message to the target base station, the uplink transmission resource is first sent from the target base station. When allocated or when an uplink transmission resource is first indicated

- When the terminal receives an indication to switch the uplink from the target base station to the target base station (eg, an RRC message (eg, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When the terminal receives an indication to switch the uplink from the source base station to the target base station (eg, an RRC message (eg, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When the terminal receives an instruction to release the connection with the source base station from the target base station (eg, an RRC message (eg, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When the terminal receives an instruction to release the connection with the source base station from the source base station (for example, an RRC message (for example, RRCReconfiguration message) or a MAC CE or RLC control PDU or PDCP control PDU

- When the terminal releases the connection with the source base station and releases the first protocol layer devices

- If the terminal does not receive downlink data for a predetermined time from the source base station

- When a specific condition is extended based on the above conditions, when the terminal successfully completes the random access procedure to the target base station through the layer devices of the second bearer, and is allocated the first uplink transmission resource from the target base station, or uplink to the terminal When a link transmission resource is first indicated

* For example, more specifically, if the UE receives a handover command message from the source base station and is instructed to random access to the target base station, the instructed random access is a contention free random access procedure (CFRA). ) (For example, if a preamble or a UE cell identifier (for example, C-RNTI) is assigned)

** When the terminal transmits a preamble designated in advance to the cell of the target base station and receives a random access response (RAR) message, it can be considered that the random access procedure has been successfully completed, so the allocated in the random access response message Alternatively, when the included or indicated first uplink transmission resource is received, it may be determined that the third condition is satisfied.

* If the UE receives a handover command message from the source base station and is instructed to random access to the target base station, if the commanded random access is a contention-based random access procedure (CBRA, Contention-Based Random Access) (e.g. For example, if a preamble or UE cell identifier (eg, C-RNTI) is not assigned in advance)

** The UE transmits a preamble (e.g., a random preamble) to the cell of the target base station, receives a random access response (RAR) message, and is assigned, included or indicated in the random access response message. When message 3 (e.g., a handover complete message) is transmitted using uplink transmission resources, and when a contention resolution MAC CE (MAC CE) indicating that contention has been resolved from the target base station is received, the terminal randomly accesses the target base station. Since the procedure can be considered to have been successfully completed, the UE monitors the PDCCH afterwards, and when the uplink transmission resource is received for the first time on the PDCCH corresponding to the C-RNTI of the UE, or the third condition is determined for the first time. You can judge that you are satisfied. As another method, when the size of the uplink transmission resource allocated in the random access response message is sufficient to transmit message 3 and the terminal can additionally transmit uplink data, it is determined that the uplink transmission resource is received for the first time and the second It can be judged that the condition of 3 is satisfied.

- If a handover method that does not require a random access procedure (RACH-less handover) is also indicated in the handover command message received by the terminal,

* If the handover command message contains uplink transmission resources for the target base station,

** When the terminal transmits message 3 (e.g., a handover complete message or an RRCReconfigurationComplete message) as an uplink transmission resource of the target base station and receives a terminal identifier confirmation MAC CE (UE Identity Confirmation MAC CE) from the base station, a random access procedure It may be determined that is successfully completed and it may be determined that the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

* If the handover command message does not contain uplink transmission resources for the target base station

** When the UE monitors the PDCCH for the target base station (or cell) and receives an uplink transmission resource through the PDCCH corresponding to the C-RNTI of the UE, or when the uplink transmission resource is used, message 3 (e.g., handover When a completion message or an RRCReconfigurationComplete message) is transmitted and a UE Identity Confirmation MAC CE (UE Identity Confirmation MAC CE) is received from the base station, it may be determined that the random access procedure has been successfully completed and the first condition is satisfied. As another method, it may be determined that the first condition is satisfied when the first uplink transmission resource is received through the PDCCH corresponding to the C-RNTI of the UE by monitoring the PDCCH after the random access procedure is successfully completed.

If the third condition is not satisfied, the third condition can be checked while continuing to perform the existing procedure.

In the embodiments of the PDCP layer device procedure proposed in the present invention, the upper PDCP layer device has a common header compression protocol context (for example, ROHC context) for data transmitted in the PDCP layer device structure as shown in FIG. And each of the lower PDCP layer devices 1k-21 and 1k-22 may be extended and applied to a structure in which each encryption procedure is performed using different security keys.

In addition, the embodiments of the PDCP layer device procedure proposed in the present invention, each lower PDCP layer device (1k-21, 1k-22) for the data received in the PDCP layer device structure as shown in Fig. It can be extended and applied to a structure in which each decoding procedure is performed by using and a higher PDCP layer device performs a header compression decompression procedure with a common header compression protocol context (eg, ROHC context).

A specific embodiment of the PDCP layer apparatus proposed in the present invention may perform different procedures according to the type of handover indicated in the handover command message received by the terminal as follows.

- If the handover type indicated in the handover command message received from the source base station indicates the first handover (for example, a general handover procedure),

* The terminal may perform the PDCP layer device according to the first embodiment of the present invention (for example, a PDCP layer device re-establishment procedure (PDCP re-establishment)).

- If the handover type indicated in the handover command message received from the source base station by the terminal indicates the second handover (for example, the handover method as in the fourth embodiment or the fifth embodiment proposed in the present invention) Occation,

* The terminal may perform the third, fourth, or fifth embodiment of the PDCP layer device proposed in the present invention (for example, a PDCP layer device continuation procedure (PDCP continue)).

In addition, in the above of the present invention, when the source base station instructs the terminal to perform a handover applying the embodiments proposed in the present invention, the source base station can start data forwarding to the target base station when the following fifth condition is satisfied. The fifth condition may mean that one or more of the following conditions are satisfied.

When receiving an indication that the terminal has successfully completed handover from the target base station

- When sending a handover command message to the terminal

- When transmitting a handover command message to the terminal and confirming successful delivery (HARQ ACK or NACK or RLC ACK or NACK) for the handover command message

- When the source base station receives an indication (for example, an RRC message (for example, an RRCReconfiguration message) or a MAC CE or RLC control PDU or a PDCP control PDU) from the terminal to release the connection with the source base station

- When the timer expires by transmitting a handover command message to the terminal and driving a predetermined timer

- When information about successful delivery of downlink data (HARQ ACK or NACK or RLC ACK or NACK) from the terminal is not received for a predetermined time

1M shows the structure of a terminal to which an embodiment of the present invention can be applied.

Referring to the drawing, the terminal includes a radio frequency (RF) processing unit (1m-10), a baseband, a processing unit (1m-20), a storage unit (1m-30), and a control unit (1m-40). do.

The RF processing unit 1m-10 performs a function of transmitting and receiving a signal through a wireless channel such as band conversion and amplification of a signal. That is, the RF processing unit (1m-10) up-converts the baseband signal provided from the baseband processing unit (1m-20) to an RF band signal and then transmits it through an antenna, and the RF band signal received through the antenna Is down-converted to a baseband signal. For example, the RF processing unit 1m-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital to analog convertor (DAC), an analog to digital convertor (ADC), and the like. I can. In the drawing, only one antenna is shown, but the terminal may include a plurality of antennas. In addition, the RF processing unit 1m-10 may include a plurality of RF chains. Furthermore, the RF processing unit 1m-10 may perform beamforming. For the beamforming, the RF processing unit 1m-10 may adjust a phase and a magnitude of signals transmitted and received through a plurality of antennas or antenna elements. In addition, the RF processing unit may perform MIMO, and may receive multiple layers when performing the MIMO operation. The RF processing unit 1m-10 may perform reception beam sweeping by appropriately setting a plurality of antennas or antenna elements under control of the controller, or adjust the direction and beam width of the reception beam so that the reception beam cooperates with the transmission beam. have.

The baseband processing unit 1m-20 performs a function of converting between a baseband signal and a bit string according to the physical layer standard of the system. For example, when transmitting data, the baseband processing unit 1m-20 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit 1m-20 restores a received bit stream through demodulation and decoding of the baseband signal provided from the RF processing unit 1m-10. For example, in the case of the OFDM (orthogonal frequency division multiplexing) method, when transmitting data, the baseband processing unit 1m-20 generates complex symbols by encoding and modulating a transmission bit stream, and subcarriers of the complex symbols After mapping to, OFDM symbols are constructed through an inverse fast Fourier transform (IFFT) operation and a cyclic prefix (CP) insertion. In addition, when receiving data, the baseband processing unit 1m-20 divides the baseband signal provided from the RF processing unit 1m-10 in units of OFDM symbols, and applies a fast Fourier transform (FFT) operation to subcarriers. After reconstructing the mapped signals, the received bit stream is restored through demodulation and decoding.

The baseband processing unit 1m-20 and the RF processing unit 1m-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 1m-20 and the RF processing unit 1m-10 may be referred to as a transmission unit, a reception unit, a transmission/reception unit, or a communication unit. Furthermore, at least one of the baseband processing unit 1m-20 and the RF processing unit 1m-10 may include a plurality of communication modules to support a plurality of different wireless access technologies. In addition, at least one of the baseband processing unit 1m-20 and the RF processing unit 1m-10 may include different communication modules to process signals of different frequency bands. For example, the different radio access technologies may include an LTE network, an NR network, and the like. In addition, the different frequency bands may include a super high frequency (SHF) (eg, 2.5GHz, 5Ghz) band, and a millimeter wave (eg, 60GHz) band.

The storage unit 1m-30 stores data such as a basic program, an application program, and setting information for the operation of the terminal. The storage unit 1m-30 provides stored data at the request of the control unit 1m-40.

The control unit 1m-40 controls overall operations of the terminal. For example, the control unit 1m-40 transmits and receives signals through the baseband processing unit 1m-20 and the RF processing unit 1m-10. In addition, the control unit 1m-40 writes and reads data in the storage unit 1m-40. To this end, the control unit 1m-40 may include at least one processor. For example, the control unit 1m-40 may include a communication processor (CP) that controls communication and an application processor (AP) that controls an upper layer such as an application program.

1N is a block diagram of a TRP in a wireless communication system to which an embodiment of the present invention can be applied.

As shown in the figure, the base station includes an RF processing unit (1n-10), a baseband processing unit (1n-20), a backhaul communication unit (1n-30), a storage unit (1n-40), and a control unit (1n-50). Consists of including.

The RF processing unit 1n-10 performs a function for transmitting and receiving a signal through a wireless channel such as band conversion and amplification of a signal. That is, the RF processing unit 1n-10 up-converts the baseband signal provided from the baseband processing unit 1n-20 to an RF band signal and transmits it through an antenna, and the RF band signal received through the antenna Downconverts to a baseband signal. For example, the RF processing unit 1n-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, and the like. In the drawing, only one antenna is shown, but the first access node may include a plurality of antennas. In addition, the RF processing unit 1n-10 may include a plurality of RF chains. Furthermore, the RF processing unit 1n-10 may perform beamforming. For the beamforming, the RF processing unit 1n-10 may adjust a phase and a magnitude of each of signals transmitted and received through a plurality of antennas or antenna elements. The RF processor may perform a downlink MIMO operation by transmitting one or more layers.

The baseband processing unit 1n-20 performs a function of converting between a baseband signal and a bit stream according to the physical layer standard of the first wireless access technology. For example, when transmitting data, the baseband processing unit 1n-20 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit 1n-20 restores a received bit stream through demodulation and decoding of the baseband signal provided from the RF processing unit 1n-10. For example, in the case of the OFDM scheme, when transmitting data, the baseband processing unit 1n-20 generates complex symbols by encoding and modulating a transmission bit stream, mapping the complex symbols to subcarriers, and then IFFT OFDM symbols are configured through calculation and CP insertion. In addition, when receiving data, the baseband processing unit 1n-20 divides the baseband signal provided from the RF processing unit 1n-10 in units of OFDM symbols, and reconstructs signals mapped to subcarriers through FFT operation. After that, the received bit stream is restored through demodulation and decoding. The baseband processing unit 1n-20 and the RF processing unit 1n-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 1n-20 and the RF processing unit 1n-10 may be referred to as a transmission unit, a reception unit, a transmission/reception unit, a communication unit, or a wireless communication unit.

The communication unit 1n-30 provides an interface for performing communication with other nodes in the network.

The storage unit 1n-40 stores data such as a basic program, an application program, and setting information for the operation of the main station. In particular, the storage unit 1n-40 may store information on bearers allocated to the connected terminal, measurement results reported from the connected terminal, and the like. In addition, the storage unit 1n-40 may store information that is a criterion for determining whether to provide or stop providing multiple connections to the terminal. In addition, the storage unit 1n-40 provides stored data according to the request of the control unit 1n-50.

The control unit 1n-50 controls overall operations of the main station. For example, the control unit 1n-50 transmits and receives a signal through the baseband processing unit 1n-20 and the RF processing unit 1n-10 or through the backhaul communication unit 1n-30. Further, the control unit 1n-50 writes and reads data in the storage unit 1n-40. To this end, the control unit 1n-50 may include at least one processor.

Claims (1)

In the control signal processing method in a wireless communication system,
Receiving a first control signal transmitted from a base station;
Processing the received first control signal; And
And transmitting a second control signal generated based on the processing to the base station.

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