KR20210039828A - Method of handling secondary cell during DAPS (dual active protocol stack) handover in the next communication systems - Google Patents

Abstract

The present invention relates to a communication technique that converges a 5G communication system with an IoT technology to support higher data rates after a 4G system and a system thereof. The present invention can be applied to intelligent services (eg, 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.

Description

Method and apparatus for handling a secondary cell during handover to which a dual activation protocol stack is applied in a next-generation mobile communication system {Method of handling secondary cell during DAPS (dual active protocol stack) handover in the next communication systems}

The present invention is characterized by providing a terminal and a base station operation in a 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, 5G communication systems include 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, evolved 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 5G systems, 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) are being 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, etc., is also emerging. In order to implement IoT, technological elements such as sensing technology, wired/wireless communication and network infrastructure, service interface technology, and security technology are required. , 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 machine type communication (MTC) are implemented by techniques such as beamforming, MIMO, and array antenna. There is. The application of a cloud radio access network (cloud RAN) as the big data processing technology described above can be said as an example of the convergence of 5G technology and IoT technology.

In the present invention, unlike a conventional handover operation in an NR system, a dual active protocol stack (DAPS) is applied at the source node and the target node when performing handover, and is connected to the source node and the target node at the same time. Data transmission and reception may be possible. In this case, there is a problem of how to handle the secondary cell (hereinafter referred to as SCell) set in the source node and the target node. If the existing procedure is followed, even if a corresponding auxiliary cell is configured, it is in an inactive state during a handover operation, and operates as an activated auxiliary cell when a separate activation signal is received. Accordingly, an object of the present invention is to provide a method of processing an auxiliary cell when performing a handover.

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 next-generation mobile communication system, when DAPS handover is performed by defining the processing method of auxiliary cells, in particular, when DAPS handover is performed, that is, when data transmission/reception is possible due to simultaneous connection between the source node and the target node, the source It is possible to support activation of the auxiliary cells of the node and the target node. Accordingly, it is possible to obtain advantages of data transmission and reception at a high data rate and stable data transmission and reception.

1A is a diagram illustrating a structure of an LTE system referred to for description of the present invention.
1B is a diagram showing a radio protocol structure in an LTE system referred to for description of the present invention.
1C is a diagram showing the structure of a next-generation mobile communication system to which the present invention is 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.
1E is a flowchart of a process of performing a general handover operation in a mobile communication system.
1fa, 1fb, and 1fc are diagrams for explaining a process of using a dual active protocol stack in a process of performing a handover.
1G is a flowchart of a process of performing a DAPS handover in the present invention.
FIG. 1H is a diagram illustrating a terminal operation for activating and managing a SCell in a source node and a target node when performing a DAPS handover proposed in the present invention.
1I is a diagram illustrating an operation of a base station for instructing and managing SCell configuration and activation when performing a DAPS handover proposed in the present invention.
1J is a block diagram showing the internal structure of a terminal to which the present invention is applied.
1K is a block diagram showing the configuration of a base station according to the present invention.

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 according to the intention or custom of users or operators. Therefore, the definition should be made based on the contents throughout the present specification. 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. Accordingly, 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, or modified terms and names based on them. However, the present invention is not limited by the terms and names, and may be equally applied to systems conforming to other standards. That is, as a system to which the present invention is applied, the entire mobile communication system, in particular, the LTE system and the NR system may be applied.

1A is a diagram illustrating a structure of an LTE system referred to for description of the present invention.

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 consists of a mobility management entity (MME, 1a-25) and a serving-gateway (S-GW, 1a-30). The user equipment (hereinafter referred to as UE or terminal) 1a-35 accesses the external network through the eNBs 1a-05 to 1a-20 and the S-GW 1a-30.

In FIG. 1A, the 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 performs scheduling is required, and the 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 a 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 a mobility management function 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 referred to for description of the present invention.

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), respectively in the terminal and the eNB, It consists of medium access control (MAC) (1b-15, 1b-30). PDCP (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 function (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 an 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 UE, 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 function

-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 transmits 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 is applied.

Referring to Figure 1c, as shown, the radio access network of the next-generation mobile communication system is a next-generation base station (new Radio Node B, hereinafter NR NB or NR gNB) (1c-10) and NR CN (new radio core network) (1c). -05). 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, since all user traffic is serviced through a shared channel, 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 existing LTE, it may have more than the existing maximum bandwidth, and an orthogonal frequency division multiplexing (hereinafter referred to as OFDM) may be used as a wireless access technology, and an additional beamforming technology may be applied. . In addition, an adaptive modulation & coding method (hereinafter referred to as AMC) is applied to determine a modulation scheme and a channel coding rate according to the channel state of the terminal. 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 a mobility management function for a terminal, and is connected to a plurality of base stations. In addition, the next-generation mobile communication system can be interworked 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 eNB (1c-30), which is an existing base station.

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 MACs (1d-15, 1d-30).

The main functions of the NR SDAPs 1d-01 and 1d-45 may include some of the following functions.

-Transfer of user plane data

-Mapping between a QoS flow and a DRB for both DL and UL for uplink and downlink

-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, for each bearer, or for each logical channel, and the SDAP header When is set, the UE uses the NAS QoS reflection configuration 1-bit indicator (NAS reflective QoS) and the AS QoS reflection configuration 1-bit indicator (AS reflective QoS) in the SDAP header to map the QoS flow of the uplink and downlink and the data bearer. 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 a 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 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 an RLC sequence number (SN) or a PDCP sequence number (SN). 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 the upper 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 the function of directly delivering RLC SDUs received from the lower layer to the upper layer regardless of the order. When received by being divided into SDUs, 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 (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 function

-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.

1E is a flowchart of a process of performing a handover operation in a mobile communication system.

The terminal 1e-05 may receive a predetermined RRC message including measurement configuration from the source cell 1e-10 (1e-25).

The terminal may measure the signal quality of the serving cell and neighboring cells using the measurement configuration information, and report the collected cell measurement information to the source cell periodically or when a set event occurs (1e-30). There is (1e-35).

The source cell may determine whether to trigger a general handover operation based on the reported cell measurement information (1e-40). For example, when Event A3 (Neighbor becomes offset better than SpCell) is satisfied and cell measurement information is reported, the source cell may determine a general handover.

If it is determined to trigger the general handover, the source cell may request the general handover to one target cell 1e-20 through a predetermined inter-node message (1e-45).

Upon receiving the request, the target cell may accept the request and transmit a message including handover configuration information necessary for the general handover operation to the source cell (1e-50).

The source cell stores handover configuration information and additional configuration information received from the target cell in a predetermined RRC message, and transmits the RRC message to the terminal (1e-55). The configuration information includes at least one of ID of the target cell, frequency information, configuration information required for a random access operation to the target cell (dedicated preamble information, dedicated radio resource information, etc.), transmission power information, and C-RNTI information used in the target cell. One can be included.

Upon receiving the handover configuration information, the terminal immediately starts a random access process to the target cell and drives a timer T304 (1e-60). At the same time, data transmission/reception with the serving cell is stopped. This is because the terminal has a single protocol stack.

The terminal transmits a preamble for a random access procedure (1e-65). The terminal may be provided with a dedicated preamble and may transmit the provided preamble. If the dedicated preamble is not provided, one of the preambles used in the contention basis can be transmitted.

Upon receiving the preamble, the target cell transmits a random access response message (RAR) to the terminal (1e-70).

The UE transmits msg3 to the target cell using UL grant information included in the RAR (1e-75). The msg3 may include an RRCConnectionReconfigurationComplete message in case of an LTE system and an RRCReconfigurationComplete message in case of an NR system. When the random access process is successfully completed, it is regarded that the general handover has been successfully completed, and the running timer T304 is stopped. If the general handover is not successfully completed until the T304 timer expires, it is regarded as handover failure and RLF is declared.

1fa, 1fb, and 1fc are diagrams for explaining a process of using a dual active protocol stack in a process of performing a handover.

When performing the general handover, the terminal stops data transmission and reception with the source cell when receiving the handover configuration information, and starts data transmission and reception with the target cell after the handover process is successful. Accordingly, an interruption time occurs during a time period in which the data transmission/reception cannot be performed. If the terminal has dual active protocol stacks, data transmission and reception with the source cell can be maintained during the time period. In the present invention, a handover in consideration of the terminal capability as described above is referred to as a dual active protocol stack (DAPS) handover.

When DAPS handover is configured, the UE can simultaneously receive downlink data from the source cell and the target cell. However, simultaneous uplink data transmission to the source cell and the target cell may be possible only when a predetermined condition is satisfied due to a lack of terminal transmission power or signal interference. In order to minimize the UE complexity, uplink data transmission during DAPS handover is possible for only one link, and uplink in which data transmission is performed may be switched from the source cell to the target cell at a specific time point.

At each major specific time point, the active state of the dual protocol stack corresponding to the source cell and the target cell and the terminal operation are different.

Before handover is performed (1f-05), the UE uses only the protocol stack corresponding to the source cell.

Before DAPS handover configuration information is provided to the terminal and RACH is performed on the target cell (1f-10), when the terminal receives DAPS handover configuration information through an RRCReconfiguration message, a protocol stack corresponding to the target cell can be configured. . However, the terminal still uses only the protocol stack corresponding to the source cell. Therefore, even if the protocol stack corresponding to the target cell is inactive, it is irrelevant.

During the RACH execution period (1f-15), when the RACH operation starts, at least the PHY layer and the MAC layer in the protocol stack corresponding to the target cell are activated to perform the RACH operation. At this time, the terminal still maintains data transmission/reception with the source cell.

When the time point (1f-20) that the UE transmits the HO success complete message to the target cell comes, the UE activates at least some functions of the PHY layer, the MAC layer, the RLC layer, and the PDCP layer in the protocol stack corresponding to the target cell. The HO success completion message, which is a radio bearer, can be processed. The terminal may transmit uplink data to the source cell at least before transmitting the HO success complete message to the target cell.

After the UE receives the RAR from the target cell (1f-25), the dual active protocol stack activates all of them. The UE maintains data transmission/reception with the source cell until a specific point in time arrives after RAR reception. In addition, the time point at which the UE can maintain the source cell and downlink data reception and the time point at which the uplink data transmission can be maintained may be different. The UE may transmit uplink data to the source cell until the HO success complete message is transmitted to the target cell, but downlink data reception is possible until thereafter.

After the UE releases the source cell (1f-30), the protocol stack corresponding to the source cell is also released. From then on, the UE uses only the protocol stack corresponding to the target cell.

1G is a flowchart of a process of performing a DAPS handover in the present invention.

The terminal (1g-02) switches to the connection mode with the source base station (1g-04) through an RRC establishment or RRC resume process (1g-12).

A terminal with DAPS handover support capability reports to the source base station that it supports DAPS handover. The base station sets the measurement configuration to the terminal by using an RRCReconfiguration message for the purpose of supporting mobility (1g-16).

When the measurement report event is triggered (1g-18), the terminal may report a measurement report to the base station (1g-20).

Upon receiving the measurement report, the source base station determines to perform handover with a specific neighbor base station based on the cell measurement information included in the measurement report (1g-22). Then, the source base station transmits a handover request message to the target base station 1g-06, and the target base station transmits a response message thereto to the source base station (1g-24).

The handover request message may include an indicator indicating that the terminal will perform DAPS handover. The response message includes configuration information required when the terminal accesses the target cell.

The source base station transmits handover configuration information and ReconfigurationWithSync to the terminal using RRCReconfiguration (1g-26). The handover configuration information includes an indicator indicating handover using DAPS. Further, the RRCReconfiguration may include configuration information for DAPS handover, and the configuration information may include bearer configuration information for configuring a dual protocol stack.

After receiving the indicator, the terminal maintains data transmission/reception with the source cell until a predetermined time point even after transmitting the initial preamble to the target cell (1g-28, 1g-34). That is, the UE can perform a random access procedure with a target cell using a protocol stack corresponding to the target cell using a dual protocol stack, and maintain data transmission/reception with a source cell using a protocol stack corresponding to the source cell. Terminal user data transmitted and received through the source cell is transmitted to the end user through the UPF (1g-08) (1g-30). The source cell may forward downlink data of the terminal to the target cell (1g-32). This is because the signal quality of the link with the source cell rapidly deteriorates, so that data transmission/reception may become difficult any more.

The terminal performs random access to the target cell (1g-36). The terminal transmits an RRCReconfiguratonComplete message to the target cell (1g-38). If the RRC message is successfully transmitted, it means that the handover to the target cell has been successfully completed.

The terminal performs uplink data transmission with the source cell until the RRC message is successfully transmitted. When the UE receives a UL grant (uplink scheduling information) from the target cell, it may switch uplink to the target cell. Upon receiving the RRCReconfigurationComplete message, the target cell may determine to release the connection between the terminal and the source cell (1g-40). The target cell requests the source cell to release the connection (1g-42). Upon receiving the request, the source cell stops transmitting and receiving data with the terminal. The source cell provides SN status transfer to the target cell (1g-44). The information is used to smoothly perform data transmission/reception with the terminal in the target cell.

The target cell instructs the terminal to release the connection with the source cell by using a predetermined RRC message (1g-46). Upon receiving the message, the terminal releases the connection with the source cell (1g-52), and transmits a response message to the message (1g-48). As another option, the terminal may implicitly release the connection with the source cell after a time when the RRCReconfigurationComplete message is successfully transmitted to the target cell or after a predetermined offset time. The target cell requests U-plane switching from the AMF (1g-10) (1g-54). Upon receiving the request, the AMF transmits an End Marker to the source cell (1g-56). The source cell releases the UE context for the UE (1g-58).

As described in Fig. 1g, in the present invention, a dual protocol stack is activated in the source cell and the target cell through DAPS handover, so that data is connected to both cells even in an operation in which the source cell and the target cell perform a handover operation. Make it possible to transmit and receive. In particular, in the present invention, when a corresponding DAPS handover is performed, the CA operation (data transmission/reception through SCell activation) set in the source node can be continuously performed. In addition, it is characterized in that the CA operation (data transmission/reception through SCell activation) can be performed even before the handover procedure is completed in the target node performing the DAPS handover.

Accordingly, in the present invention, main proposals for CA operation in a target node performing DAPS handover are summarized as follows. For detailed terminal operation, refer to the contents shown in FIG. 1H.

-A method of differential application of SCell handling according to the handover type.

-In normal HO, a method of deactivating SCells at the time of receiving the HO command, resetting MAC, and applying a new MAC-config.

-In DAPS HO, a method of applying the first operation at the time of receiving the HO command, the second operation at the time when UL switching occurs, and the third operation at the time of releasing the source.

-Meaning of DAPS HO support

-Source SCells are released at T3 (when the source cell is released) after maintaining the current state.

-TAG association of source and target cells

-BWP-timer handling

FIG. 1H is a diagram illustrating a terminal operation for activating and managing a SCell in a source node and a target node when performing a DAPS handover proposed in the present invention.

The terminal in the connected state may generate terminal capability information in response to a message requesting UE capability information from the base station in steps 1h-05 and report it to the base station. In particular, information including whether to support DAPS handover proposed in the present invention may be included in the terminal capability information.

If the corresponding DAPS handover support capability is the capability to support regardless of the frequency band, the indicator for the capability may exist 1 bit for each terminal, but if the DAPS handover support capability is for each frequency band or a combination of frequency bands ( If different for each band combination (hereinafter BC), an indicator 1 bit supporting DAPS handover may be included in the UE capability for each band or the UE capability for each band combination and signaled. That is, the DAPS handover support capability reporting method can be summarized as follows.

1. Display whether 1 bit is supported per terminal

2. Display whether 1 bit is supported for each band combination (or band)

-Supporting DAPS for a specific BC may mean that DAPS is supported when the BC currently being used in the source is the same as or a subset of the BC, and the BC used in the target is the same as or a subset of the BC.

-For example, if the terminal supports DAPS for BC of [B1, B2, B3], it is [[B1, B2, B3] -> [B1, B2, B3]], [[B1, B2, B3] -> [B2, B3]],… . It means that it supports handover such as. In this example, the specific band Bx may be a source band, and By may be a band at the target.

-In this case, the UE capability (MIMO layer, BW, power, etc.) indicated in the corresponding BC can be applied as it is, and separate reduced UE capability information for SCell configuration information of the source and target node applied during DAPS handover May be delivered additionally. That is, a new feature set combination different from the existing BC-related feature set combination (including reduced terminal capability for BC-based DAPS handover)

Thereafter, the terminal in the connected mode state may receive an RRC reconfiguration message from the current serving base station, and receive data transmission/reception and measurement-related settings in a corresponding serving cell. In step 1h-10, the UE performs measurement of neighboring cells based on measurement information on neighboring RAT/frequency/cells set by the base station, and serves measurement values for neighboring cells according to specific reporting conditions (periodic or event-based). Report to the cell.

Based on the measurement report, the base station may determine whether to handover and instruct the terminal to perform a handover command. That is, in step 1h-15, the UE may receive an RRC message including a handover command from the base station, and the type of handover in the RRC message is general handover (handover performed by an existing UE) or DAPS handover. It may include an indicator indicating that it is and setting information about it. As for the configuration information according to the handover type, configuration information for general handover and DAPS handover may be simultaneously transmitted. In this case, the DAPS handover is operated with priority, and if the operation fails, the normal hand Fallback by over operation. In addition, in the present invention, the following time state is defined and used to describe the operation of the terminal at the correct time point.

-State T1 (1h-15): When RRCReconfiguration message including handover command is received

-State T2 (1h-35): A time point at which UL switching is performed from a source to a target (for example, a time point at which a UL grant is received from a target cell)

-State T3 (1h-40): The point at which the source link is released (a command to explicitly release the source configuration is received from the target cell, or a preset timer expires and the terminal is released to autonomos)

In the following operation, when a DAPS handover is instructed, an operation of a terminal in which SCells are configured and activated in a source and a target to be operated will be described. This is referred to as the first DAPS handover operation.

In step 1h-20, the UE checks which handover type is indicated by the RRCReconfiguration message including the handover command received in step 1h-15. For reference, the handover command corresponds to a case in which setting information on the target sPCell is provided through the ReconfigurationWithSync IE included in the RRCReconfiguration message.

If, when a general handover is instructed, the terminal performs a SCell addition/modification command based on the configured information, and follows the SCell release setting when there is an SCell release setting. In this case, the SCells indicated in the SCell release may be the index of the source cell, the UE releases the corresponding SCell configuration, and the SCell configuration information indicated in the SCell addition/modification command is SCell configuration information in the target node. In the case of a general handover, even if the SCell configuration information in the target node is provided in the handover command, the initial state of the corresponding SCell is deactivated (inactive). In addition, while a handover is instructed, random access to a target cell is performed, and a handover operation is performed, the link with the source cell is disconnected.

When DAPS handover is indicated in step 1h-20 (for example, there is an indicator indicating DAPS handover in the ReconfigurationWithSync IE, or there is an associated configuration information IE), the terminal is sent to the source SCells indicated in step 1h-30. Source SCells that have been released for and have not been released can maintain their state even after the DAPS HO indication. That is, data transmission/reception is performed by being connected to source cells even during a handover operation. When there is an addition/modification setting for the target SCell, it is applied and the corresponding SCells are switched to the initial setting state (deactivate or activate or limited activate).

Features at this stage are as follows

-Add target SCells while maintaining existing SCells.

-The SCells of the source are named as the source SCell group, and the SCells newly set in State T1 are named as the target SCell group.

-Source SCells maintain their current state when HO is indicated and then release to State T3.

-Target SCells are newly added according to SCellToAddModLIst in the RRC message.

-SCellToReleaseList is IE for source cell group

-SCellToAddModLIst is IE for target cell group.

-Or, it is possible to introduce a separate IE for addition to the target cell group SCell

-Source SCells and Target SCells have different SCellIndex

In addition, the operation according to the configuration information for the SCells of the target cell group may be performed in two steps. That is, SCell configuration information applied while DAPS handover is performed and SCell configuration information applied when only a target node is connected after the handover is completed may be provided at the same time. In this case, the SCell configuration information during DAPS handover may be configured to provide limited terminal performance and have full terminal performance after handover. Likewise, configuration information of source SCells during DAPS handover operation may be additionally provided as limited for limited terminal performance. For reference, target SCells may be activated to an initial value when DAPS handover is set up (or limited activation), deactivated initially, but may be activated after receiving L2 signaling (SCell activate MAC CE).

In steps 1h-35, after performing random access to the target sPCell according to the handover configuration, the UE switches uplink transmission to the target cell when receiving an uplink grant (UL grant) from the corresponding cell. Even at this time, data reception is performed by being simultaneously connected from the source cell and the target cell, and uplink transmission is switched to the target cell. However, ACK/NACK transmission and RLC retransmission for reception from the previous source can still be performed with the source. This step defines the time state as State T2.

In step 1h-40, the UE receives an RRCReconfiguration message notifying that the handover has been completed from the target cell, and the RRC message includes not only cell configuration information (sPCell, SCell) at the target node, but also SCells at the source node. You can receive release instructions. This is a method of explicitly instructing the release of previous source SCells, and as an alternative method, the UE can autonomously release the corresponding SCell configuration according to the expiration of the SCell release timer operation. That is, the SCell release timer value may be provided to the RRCReconfiguration message including DAPS handover configuration information in step 1h-15, and the terminal operates the timer after receiving the RRC message, and when the timer expires, the source SCell Release them. If the DAPS handover fails, the timer is stopped and a fallback to the source node is performed, or a general handover may be restarted. In addition, the timer may be designated as a default value to the terminal rather than an RRC message.

If the DAPS handover first operation is shown through the RRC configuration parameter, it can be summarized as follows.

The second DAPS handover operation is defined as an operation of processing a timing advance group (TAG) in SCells at a source and a target when DAPS handover is performed. The basic SCell configuration/activation related operation follows the DAPS handover first operation described above, and in this description, only additional parts related to the TAG will be described. The method proposed in this operation can be summarized as follows.

1. Separate management/maintenance of source TAGs and target TAGs

2. Source SCells are managed according to the source TAG configuration, and are not affected even when a DAPS HO command is received.

3. Target SCells are TAG configured according to the tag-Id indicated in the newly configured ServingCellConfig

■ SCell setting indicated by SCellAddModList

■ Or, SCell setting indicated by a separate IE for the target cell

Serving cell identity and TAG identity in the second operation of the DAPS handover are allocated according to the following principles.

Identity of the remaining serving cells except for a specific serving cell is consistently allocated to all serving cells regardless of source serving cells and target serving cells. For example, if serving cell identity 1 is assigned to a source serving cell, serving cell identity 1 cannot be used for a target serving cell. As for the serving cell identity of a specific serving cell (SpCell), the same value of 0 is assigned to the source serving cell and the target serving cell.

The TAG identity targeting the source serving cells and the TAG identity targeting the target serving cells may overlap each other. That is, the TAG identity needs to be consistent only for serving cells in a predetermined serving cell group. For example, source tag 0 is a tag that includes source PCell, and target tag 0 is a tag that includes target PCell. The terminal autonomously releases the source TAGs in State T3 and releases the source SCells.

If the second DAPS handover operation is shown through the RRC configuration parameter, it can be summarized as follows.

The third DAPS handover operation is defined as an operation of setting and processing a bandwidth part (BWP) at a source and a target when DAPS handover is performed.

In order to operate DAPS handover in the initial stage, the BWPs of the source serving cells and the target serving cells may need to be aligned with each other. That is, it is because the burden on the RF capability of the terminal can be reduced, and the corresponding DAPS handover can be performed only in a limited situation. In this case, the terminal stops the bwp-timer in the time period T1 to T3 so that the BWP does not autonomously switch during DAPS handover. For reference, during the period, the source base station informs the target base station of the current active BWP configuration information (such as active bwp frequency domain configuration information for each serving cell) through an inter-node message. The target base station may determine configuration information of initial BWPs so that initial BWPs of serving cells overlap with active BWPs of source.

1I is a diagram illustrating an operation of a base station for instructing and managing SCell configuration and activation when performing a DAPS handover proposed in the present invention.

In steps 1i-05, the base station may deliver an RRC message (UECapabilityEnquiry) requesting terminal capability information to a connected terminal, and receives a UECapabilityInformation message in response thereto. The UE capability information message includes an indicator or UE capability information indicating whether the UE supports DAPS handover. The detailed method has been described in Fig. 1h-05.

In step 1i-10, the base station may instruct the UE in a connected state to measure neighbor cells, and receive a measurement report from the UE in response thereto.

In step 1i-15, the base station can determine whether to handover based on the measured values of the neighboring cell and the serving cell received. In this step, the source base station delivers an inter-node message for the handover request to the target base station, Receive a response message accordingly. The response message (inter-node message) includes handover configuration information in the target base station, and the information is transparently transmitted from the source base station to the terminal. In this step, the source base station and the target base station can provide/share negotiation or assistance information on what configuration the terminal will operate with during DAPS handover, and determine configuration information in each base station accordingly. The content may include UE capability information and UE capability information (number of MIMO layers, BW, power) limited in the DAPS, which may be in the form of an assistance message applied to each BC or to the entire UE. In addition, configuration information (RB-config, AS-Config, DRX configuration, PHR configuration, measurement configuration, etc.) set in the source base station may be included.

In step 1i-25, the source base station transmits an RRCReconfiguration message to the terminal, thereby performing a DAPS handover operation. That is, after the delivery of the corresponding message, the terminal is simultaneously connected to the source base station and the target base station according to the determined DAPS handover operation, and the limited CA operation can be performed even during handover through the configured SCell. For detailed terminal operation, refer to the description in FIG. 1H.

In step 1i-30, the base station may receive a message indicating that the handover has been completed from the target base station after a specific time has elapsed, and then release the connection with the terminal. Or, if the corresponding handover fails, it falls back to the original configuration and maintains the connection state with the terminal. In the above step, when the target base station transmits the RRCReconfiguration message indicating that the handover has been completed to the terminal, it may include an indicator to release the SCell configuration information connected to the source base station to the terminal and release the connection. Thereafter, the handover is completed between the target base station and the terminal to maintain a connection state and perform a general data transmission/reception procedure.

1J is a block diagram showing the internal structure of a terminal to which the present invention is applied.

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

The RF processing unit 1j-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 1j-10 up-converts the baseband signal provided from the baseband processing unit 1j-20 to an RF band signal, and then transmits it through an antenna, and an RF band signal received through the antenna. Is down-converted to a baseband signal. For example, the RF processing unit 1j-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 1j-10 may include a plurality of RF chains. Furthermore, the RF processing unit 1j-10 may perform beamforming. For the beamforming, the RF processing unit 1j-10 may adjust a phase and a magnitude of each of signals transmitted/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 baseband processing unit 1j-20 performs a function of converting between a baseband signal and a bit stream according to the physical layer standard of the system. For example, when transmitting data, the baseband processing unit 1j-20 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit 1j-20 restores a received bit stream through demodulation and decoding of the baseband signal provided from the RF processing unit 1j-10. For example, in the case of the OFDM (orthogonal frequency division multiplexing) method, when transmitting data, the baseband processing unit 1j-20 generates complex symbols by encoding and modulating a transmission bit stream, and subcarriers 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 1j-20 divides the baseband signal provided from the RF processing unit 1j-10 in units of OFDM symbols, and applies a fast Fourier transform (FFT) operation to subcarriers. After restoring the mapped signals, the received bit stream is restored through demodulation and decoding.

The baseband processing unit 1j-20 and the RF processing unit 1j-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 1j-20 and the RF processing unit 1j-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 1j-20 and the RF processing unit 1j-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 1j-20 and the RF processing unit 1j-10 may include different communication modules to process signals of different frequency bands. For example, the different wireless access technologies may include a wireless LAN (eg, IEEE 802.11), a cellular network (eg, LTE), and the like. In addition, the different frequency bands may include a super high frequency (SHF) (eg, 2.NRHz, NRhz) band, and a millimeter wave (eg, 60GHz) band.

The storage unit 1j-30 stores data such as a basic program, an application program, and setting information for the operation of the terminal. In particular, the storage unit 1j-30 may store information related to a second access node performing wireless communication using a second wireless access technology. In addition, the storage unit 1j-30 provides stored data according to the request of the control unit 1j-40.

The controller 1j-40 controls overall operations of the terminal. For example, the control unit 1j-40 transmits and receives signals through the baseband processing unit 1j-20 and the RF processing unit 1j-10. In addition, the control unit 1j-40 writes and reads data in the storage unit 1j-40. To this end, the control unit 1j-40 may include at least one processor. For example, the controller 1j-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.

1K is a block diagram showing the configuration of a base station according to the present invention.

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

The RF processing unit 1k-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 1k-10 up-converts the baseband signal provided from the baseband processing unit 1k-20 into an RF band signal, and then transmits it through an antenna, and an RF band signal received through the antenna. Is down-converted to a baseband signal. For example, the RF processing unit 1k-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 1k-10 may include a plurality of RF chains. Furthermore, the RF processing unit 1k-10 may perform beamforming. For the beamforming, the RF processing unit 1k-10 may adjust a phase and a magnitude of each of signals transmitted/received through a plurality of antennas or antenna elements. The RF processing unit may perform a downlink MIMO operation by transmitting one or more layers.

The baseband processing unit 1k-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 1k-20 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit 1k-20 restores a received bit stream through demodulation and decoding of the baseband signal provided from the RF processing unit 1k-10. For example, in the case of the OFDM scheme, when transmitting data, the baseband processor 1k-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 1k-20 divides the baseband signal provided from the RF processing unit 1k-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 1k-20 and the RF processing unit 1k-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 1k-20 and the RF processing unit 1k-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 backhaul communication unit 1k-30 provides an interface for performing communication with other nodes in the network. That is, the backhaul communication unit 1k-30 converts a bit stream transmitted from the main station to another node, for example, an auxiliary base station, a core network, etc., into a physical signal, and converts the physical signal received from the other node into a bit. Convert to heat.

The storage unit 1k-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 1k-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 1k-40 may store information that is a criterion for determining whether to provide multiple connections to the terminal or to stop. In addition, the storage unit 1k-40 provides stored data according to the request of the control unit 1k-50.

The control unit 1k-50 controls overall operations of the main station. For example, the control unit 1k-50 transmits and receives signals through the baseband processing unit 1k-20 and the RF processing unit 1k-10 or through the backhaul communication unit 1k-30. In addition, the control unit 1k-50 writes and reads data in the storage unit 1k-40. To this end, the control unit 1k-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.

Images