KR20200115328A - Method and apparatus for handover in a next generation mobile communication system - Google Patents

Abstract

The present invention relates to a communication technique for fusing a 5G communication system with the IoT technology for supporting a higher data transmission rate than that of the 4G communication system, and a system thereof. The present invention is applicable to intelligence services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car or connected car, health care, digital education, retail, security and safety-related services, etc. In addition, according to the present invention, the method of operating by a source node in a wireless communication system comprises the steps of: transmitting a handover request message including a conditional handover-related target cell identifier to a target node; receiving, from the target node, a handover request response message including a handover command message including setting information of the target cell for the conditional handover; and transmitting, to a terminal, a radio resource control (RRC) resetting message including the handover command message and the condition information for the conditional handover. The method and the apparatus for handover in the next-generation mobile communication system are able to prevent a node dependency from being destroyed.

Description

Method and device for handover in next-generation mobile communication system {METHOD AND APPARATUS FOR HANDOVER IN A NEXT GENERATION MOBILE COMMUNICATION SYSTEM}

The present disclosure relates to operation of a terminal and a base station in a mobile communication system. The present disclosure relates to a method and apparatus for handover in a next generation mobile communication system. In addition, the present disclosure relates to a handover command signaling method and apparatus for conditional handover in a next generation mobile communication system. In addition, the present disclosure relates to a method and apparatus for performing beam-based handover in a wireless 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, a 5G communication system or a pre-5G communication system is called a Beyond 4G Network communication system or an LTE system and a Post LTE system. 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, which are 5G communication technologies. will be. 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.

With the development of wireless communication systems, a method for controlling activation of a plurality of RLC layer devices in a system supporting a high-reliability low-delay service is required.

An embodiment of the present disclosure aims to provide a method and apparatus for handover in a next-generation mobile communication system.

In addition, an embodiment of the present disclosure proposes a method of making a conditional handover command transmitted from a network to perform conditional handover and signaling of a terminal and a network, a source base station and a target base station, so that the source node determines the handover condition to the terminal. The purpose of this is to propose an inter-node signaling system that can prevent the destruction of node dependence that can occur when it is delivered directly to the node, and signals success and failure for each cell during a multi-target cell handover.

In addition, an embodiment of the present disclosure is to provide a method and apparatus for performing a beam-based terminal autonomous handover in a wireless communication system.

In addition, according to an embodiment of the present disclosure, from the moment when the beam configuration information of the contention free random access resource that can be set during the conditional handover of the terminal receives the conditional handover command, the conditional handover is performed. When the possibility of change until the execution time is high, it is intended to solve the problem of performing contention-based random access (contention-based random access or contention-based random access) without performing contention-free random access.

According to an embodiment of the present disclosure, there is provided a method performed by a source node in a wireless communication system, the method comprising: transmitting a handover request message including a conditional handover-related target cell identifier to a target node; Receiving a handover request response message including a handover command message including configuration information of a target cell for conditional handover from the target node; It may provide a method comprising the step of transmitting to the terminal a radio resource control (RRC) reconfiguration message including the handover command message and condition information for the conditional handover.

In addition, according to an embodiment of the present disclosure, in a source node of a wireless communication system, a handover request message including a conditional handover-related target cell identifier is transmitted to a transmission/reception unit and a target node through the transmission/reception unit, and the target node A handover request response message including a handover command message including configuration information of a target cell for conditional handover is received from the transceiver, and includes the handover command message and condition information for the conditional handover. It is possible to provide a source node, characterized in that controlling to transmit a radio resource control (RRC) reconfiguration message to the terminal through the transceiver.

In addition, according to an embodiment of the present disclosure, a method performed by a target node in a wireless communication system may include: receiving a handover request message including a conditional handover-related target cell identifier from a source node; And transmitting a handover request response message including a handover command message including configuration information of a target cell for conditional handover to the source node, and for the handover command message and the conditional handover. It is possible to provide a method characterized in that a radio resource control (RRC) reconfiguration message including condition information is transmitted from the source node to the terminal.

In addition, according to an embodiment of the present disclosure, there is provided a target node of a wireless communication system, comprising: a transceiver; And a handover request message including a target cell identifier related to conditional handover from a source node through the transceiver, and a handover command message including configuration information of a target cell for conditional handover to the source node. A control unit for controlling to transmit a handover request response message through the transceiver, and a radio resource control (RRC) reconfiguration message including condition information for the handover command message and the conditional handover is transmitted from the source node to the terminal It is possible to provide a target node characterized in that it is transmitted to.

An embodiment of the present disclosure proposes a method of adding a conditional handover condition to a handover command to increase performance or maintain node dependency. In addition, an embodiment of the present disclosure proposes an inter node message that signals a handover preparation request to multiple target cells and a handover setting result value for target cells selected from a target node, and is used as a signaling system for a single target cell. It eliminates time and resource inefficiency due to repeated signals.

An embodiment of the present disclosure creates a condition based on beam-based intensity information that was not considered in the existing handover among conditions of conditional handover, and is used with the existing cell-based handover to perform content-free random access. It is possible to perform conditional handover to the target cell in.

According to an embodiment of the present disclosure, a method and apparatus for handover in a next-generation mobile communication system may be provided. In addition, according to an embodiment of the present disclosure, a method and apparatus for signaling a handover command for conditional handover in a next generation mobile communication system may be provided.

Through the present disclosure, when transmitting a conditional handover command to a terminal, the source base station can achieve temporal efficiency by transmitting the handover command message received from the target base station without decoding, or instead of destroying the node dependency, the inter node signaling can be reduced. In addition, when performing conditional handover to multiple target cells, time and resources are prepared in preparation for sending and receiving handover inter node message signaling to a single target cell by indicating a cell capable of performing handover between the target node and the source node. It increases efficiency.

In addition, according to an embodiment of the present disclosure, it is possible to efficiently perform beam-based handover in a wireless communication system.

In addition, according to an embodiment of the present disclosure, when performing conditional handover in a next-generation mobile communication system, by adding or separately operating a beam strength-based condition in addition to a cell strength-based condition, the conditional handover may be set by a target base station. Handover can be performed to a target cell that can use content-free random access. In addition, when performing a conditional handover, contention-free random access can be performed to increase a handover success probability, and an additional procedure due to contention-based random access can be reduced.

1 is a diagram illustrating a structure of an LTE system according to an embodiment of the present disclosure.
2 is a diagram illustrating a radio protocol structure of an LTE system according to an embodiment of the present disclosure.
3 is a diagram illustrating a structure of a next-generation mobile communication system according to an embodiment of the present disclosure.
4 is a diagram illustrating a radio protocol structure of a next-generation mobile communication system according to an embodiment of the present disclosure.
5 is a diagram illustrating a configuration of a terminal according to an embodiment of the present disclosure.
6 is a diagram illustrating a configuration of a base station according to an embodiment of the present disclosure.
FIG. 7 is a diagram illustrating a process of determining a conditional handover in a source node, transmitting a condition to a corresponding target node, and generating a handover command in the target node according to an embodiment of the present disclosure.
8 is a diagram illustrating a process of directly transmitting a condition for conditional handover to a terminal from a source node according to an embodiment of the present disclosure.
9 is a diagram illustrating an operation of adding control information for a source node to a conditional handover command generated from a target node in a source node according to an embodiment of the present disclosure.
10 is a diagram illustrating an operation of adding multiple cells to one conditional handover scene when preparing conditional handover for multiple cells in a source node according to an embodiment of the present disclosure.
11 is a diagram illustrating an operation of adding one cell to one conditional handover scene when preparing conditional handover for multiple cells in a source node according to an embodiment of the present disclosure.
FIG. 12 is a diagram illustrating an operation of adding multi-target cell information to RRC Reconfiguration information according to an embodiment of the present disclosure.
13 is a diagram illustrating a signal flow in a process of performing conditional handover when only a beam level condition is given to a terminal without a cell level condition, corresponding to embodiments 2-1 and 2-2 according to an embodiment of the present disclosure. It is a drawing.
14 illustrates a signal flow in a process of performing conditional handover when a cell level condition and a beam level condition are both given to a terminal, corresponding to embodiments 2-3 and 2-4 according to an embodiment of the present disclosure. It is a drawing showing.
15 is a diagram illustrating a signal flow in a process of performing conditional handover when a CFRA setting according to an embodiment of the present disclosure is used as a beam level condition setting.
16 is a diagram illustrating an operation of performing conditional handover in a terminal considering beam level and cell level conditions according to an embodiment of the present disclosure.

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

For the same reason, some components in the accompanying drawings are exaggerated, omitted, or schematically illustrated. In addition, the size of each component does not fully reflect the actual size. The same reference numerals are assigned to the same or corresponding components in each drawing.

Advantages and features of the present disclosure, and a method of achieving them will be apparent with reference to the embodiments described below in detail together with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below, but may be implemented in a variety of different forms, only the present embodiments make the disclosure of the disclosure complete, and common knowledge in the technical field to which the disclosure belongs. It is provided to completely inform the scope of the disclosure to those who have, and the present disclosure is only defined by the scope of the claims. The same reference numerals refer to the same components throughout the specification.

In this case, it will be appreciated that each block of the flowchart diagrams and combinations of the flowchart diagrams may be executed by computer program instructions. Since these computer program instructions can be mounted on the processor of a general purpose computer, special purpose computer or other programmable data processing equipment, the instructions executed by the processor of the computer or other programmable data processing equipment are described in the flowchart block(s). It creates a means to perform functions. These computer program instructions can also be stored in computer-usable or computer-readable memory that can be directed to a computer or other programmable data processing equipment to implement a function in a particular way, so that the computer-usable or computer-readable memory It is also possible to produce an article of manufacture containing instruction means for performing the functions described in the flowchart block(s). Computer program instructions can also be mounted on a computer or other programmable data processing equipment, so that a series of operating steps are performed on a computer or other programmable data processing equipment to create a computer-executable process to create a computer or other programmable data processing equipment. It is also possible for instructions to perform processing equipment to provide steps for executing the functions described in the flowchart block(s).

In addition, each block may represent a module, segment, or part of code that contains one or more executable instructions for executing the specified logical function(s). In addition, it should be noted that in some alternative execution examples, functions mentioned in blocks may occur out of order. For example, two blocks shown in succession may in fact be executed substantially simultaneously, or the blocks may sometimes be executed in reverse order depending on the corresponding function.

In this case, the term'~ unit' used in this embodiment refers to software or hardware components such as FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit), and'~ unit' performs certain roles. do. However,'~ part' is not limited to software or hardware. The'~ unit' may be configured to be in an addressable storage medium, or may be configured to reproduce one or more processors. Thus, as an example,'~ unit' refers to components such as software components, object-oriented software components, class components and task components, processes, functions, properties, and procedures. , Subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, database, data structures, tables, arrays, and variables. The components and functions provided in the'~ units' may be combined into a smaller number of elements and'~ units', or may be further divided into additional elements and'~ units'. In addition, components and'~ units' may be implemented to play one or more CPUs in a device or a security multimedia card. Also, in an embodiment, the'~ unit' may include one or more processors.

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 disclosure is not limited to the terms described later, and other terms referring to objects having an equivalent technical meaning may be used.

For convenience of description below, this disclosure uses terms and names defined in the 3GPP 3rd Generation Partnership Project Long Term Evolution (LTE) standard. However, the present disclosure is not limited by the terms and names, and may be equally applied to systems conforming to other standards.

1 is a diagram illustrating a structure of an LTE system according to an embodiment of the present disclosure.

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

In FIG. 1, ENBs 1-05 to 1-20 may correspond to an existing node B of the UMTS system. The ENB is connected to the UE (1-35) through a radio channel and can perform 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, can be serviced through a shared channel. Accordingly, there is a need for a device for scheduling by collecting state information such as a buffer state, an available transmit power state, and a channel state of the UEs, and the ENBs 1-05 to 1-20 may be responsible for this. One ENB can typically control multiple cells. For example, in order to implement a transmission rate of 100 Mbps, the LTE system may use orthogonal frequency division multiplexing (OFDM) in a 20 MHz bandwidth as a radio access technology. In addition, an adaptive modulation and coding (AMC) scheme for determining a modulation scheme and a channel coding rate according to a channel state of the terminal may be applied. The S-GW 1-30 is a device that provides a data bearer, and may create or remove a data bearer under the control of the MME 1-25. The MME is a device responsible for various control functions as well as a mobility management function for a terminal, and can be connected to a plurality of base stations.

2 is a diagram illustrating a radio protocol structure of an LTE system according to an embodiment of the present disclosure.

Referring to Figure 2, the radio protocol of the LTE system is a packet data convergence protocol (Packet Data Convergence Protocol, PDCP) (2-05, 2-40), radio link control (Radio Link Control, RLC) ( 2-10, 2-35), medium access control (MAC) (2-15, 2-30). PDCP may be in charge of operations such as IP header compression/restore. The main functions of PDCP can be 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 (RLC) (2-10, 2-35) can perform ARQ operations by reconfiguring a PDCP packet data unit (PDU) to an appropriate size. Main RLC The functions can be 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 2-15 and 2-30 are connected to various RLC layer devices configured in one terminal, and may perform an operation of multiplexing RLC PDUs to MAC PDUs and demultiplexing RLC PDUs from MAC PDUs. The main functions of MAC can be 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 (2-20, 2-25) 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. You can do that.

3 is a diagram illustrating a structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

3, the radio access network of the next-generation mobile communication system (hereinafter referred to as NR or 2g) includes a next-generation base station (New Radio Node B, hereinafter referred to as NR gNB or NR base station) 3-10 and a next-generation radio core network (New Radio Core). Network, NR CN) (3-05). Next-generation radio user equipment (New Radio User Equipment, NR UE or terminal) 3-15 may access an external network through NR gNB 3-10 and NR CN 3-05.

In FIG. 3, the NR gNB 3-10 may correspond to an Evolved Node B (eNB) of an existing LTE system. The NR gNB is connected to the NR UE (3-15) through a radio channel, and can provide a service superior to that of the existing Node B. In a next-generation mobile communication system, all user traffic can be serviced through a shared channel. Accordingly, there is a need for a device for scheduling by collecting state information such as a buffer state, an available transmit power state, and a channel state of the UEs, and the NR NB 3-10 may be responsible for this. One NR gNB can control multiple cells. In the next-generation mobile communication system, in order to implement ultra-high-speed data transmission compared to the current LTE, a bandwidth greater than the current maximum bandwidth may be applied. In addition, an orthogonal frequency division multiplexing (OFDM) technique may be used as a radio access technique to additionally incorporate a beamforming technique. In addition, an adaptive modulation and coding method (hereinafter referred to as AMC) for determining a modulation scheme and a channel coding rate according to a channel state of the terminal may be applied. The NR CN (3-05) may perform functions such as mobility support, bearer setup, and QoS setup. The NR CN (3c-05) is a device responsible for various control functions as well as a mobility management function for a terminal, and can be connected to a plurality of base stations. In addition, the next-generation mobile communication system can be linked with the existing LTE system, and the NR CN (3c-05) can be connected to the MME (3-25) through a network interface. The MME 3c-25 may be connected to the eNB 3-30, which is an existing base station.

4 is a diagram illustrating a radio protocol structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

4, radio protocols of the next-generation mobile communication system include NR Service Data Adaptation Protocol (SDAP) (4-01, 4-45) and NR PDCP (4-05, respectively) in a terminal and an NR base station. 4-40), NR RLC (4-10, 4-35), NR MAC (4-15, 4-30).

The main functions of NR SDAP (4-01, 4-45) 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 SDAP layer devices, the UE uses a radio resource control (RRC) message for each PDCP layer device, bearer or logical channel, whether to use the header of the SDAP layer device or whether to use the functions of the SDAP layer device. Can be set. When the SDAP header is set, the terminal includes a non-access layer (Non-Access Stratum, NAS) QoS (Quality of Service) reflection configuration 1-bit indicator (NAS reflective QoS) and an access layer (Access Stratum, AS) QoS of the SDAP header. With the reflection configuration 1-bit indicator (AS reflective QoS), it is possible to instruct the UE to update or reconfigure mapping information for the uplink and downlink QoS flows and data bearers. The SDAP header may include QoS flow ID information indicating QoS. QoS information can be used as data processing priority, scheduling information, etc. to support smooth service.

The main functions of NR PDCP (4-05, 4-40) 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 description, the reordering function of the NR PDCP device may refer to a function of reordering PDCP PDUs received from a lower layer in order based on a PDCP sequence number (SN). The reordering function of the NR PDCP device may include a function of transmitting data to an upper layer in the order of reordering, or may include a function of directly delivering data without considering the order, and the order is rearranged and lost. It may include a function to record the lost PDCP PDUs, may include a function to report the status of the lost PDCP PDUs to the sender, and may include a function to request retransmission of the lost PDCP PDUs. have.

The main functions of the NR RLC (4-10, 4-35) 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 description, in-sequence delivery of the NR RLC device may mean a function of sequentially delivering RLC SDUs received from a lower layer to an upper layer. When one RLC SDU is originally divided into several RLC SDUs and received, the in-sequence delivery function of the NR RLC device may include a function of reassembling and delivering the same.

In-sequence delivery of the NR RLC device may include a function of rearranging 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. have.

In-sequence delivery of the NR RLC device may include a function of sequentially delivering only RLC SDUs up to before the lost RLC SDU to a higher layer when there is a lost RLC SDU.

In-sequence delivery of the NR RLC device may include a function of sequentially delivering all RLC SDUs received before the timer starts to an upper layer if a predetermined timer expires even if there is a lost RLC SDU. have.

In-sequence delivery of the NR RLC device may include a function of sequentially delivering all RLC SDUs received so far to an upper layer if a predetermined timer expires even if there is a lost RLC SDU.

The NR RLC device may process RLC PDUs in an order of reception regardless of the sequence number (Out-of sequence delivery) and transmit them to the NR PDCP device.

When the NR RLC device receives a segment, it may receive segments stored in a buffer or to be received at a later time, reconfigure it into one complete RLC PDU, and then transmit it to the NR PDCP device.

The NR RLC layer may not include a concatenation function, and may perform a function in the NR MAC layer or may be replaced with a multiplexing function of the NR MAC layer.

In the above description, out-of-sequence delivery of the NR RLC device may mean a function of directly delivering RLC SDUs received from a lower layer to an upper layer regardless of the order. Out-of-sequence delivery of the NR RLC device may include a function of reassembling and delivering when one RLC SDU is originally divided into multiple RLC SDUs and received. Out-of-sequence delivery of the NR RLC device may include a function of storing the RLC SN or PDCP SN of the received RLC PDUs, arranging the order, and recording the lost RLC PDUs.

The NR MACs 4-15 and 4-30 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 (4-20, 4-25) channel-codes and modulates upper layer data, makes it into OFDM symbols, and transmits it to the wireless channel, or demodulates and channel-decodes the OFDM symbol received through the radio channel to the upper layer. You can perform the transfer operation.

5 is a diagram illustrating a configuration of a terminal according to an embodiment of the present disclosure.

Referring to FIG. 5, the terminal includes a radio frequency (RF) processing unit 5-10, a baseband processing unit 5-20, a storage unit 5-30, and a control unit 5-40. can do. In addition, the control unit 5-40 may further include a multiple connection processing unit 5-42.

The RF processing unit 5-10 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 5-10 up-converts the baseband signal provided from the baseband processing unit 5-20 to an RF band signal and 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 5-10 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 5-10 may include a plurality of RF chains. Further, the RF processing unit 5-10 may perform beamforming. For the beamforming, the RF processing unit 5-10 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 5-20 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 5-20 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit 5-20 restores a received bit sequence through demodulation and decoding of the baseband signal provided from the RF processing unit 5-10. For example, in the case of the OFDM (orthogonal frequency division multiplexing) scheme, when transmitting data, the baseband processing unit 5-20 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 5-20 divides the baseband signal provided from the RF processing unit 5-10 in units of OFDM symbols, and maps them to subcarriers through fast Fourier transform (FFT). After restoring the received signals, the received bit stream is restored through demodulation and decoding.

The baseband processing unit 5-20 and the RF processing unit 5-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 5-20 and the RF processing unit 5-10 may be referred to as a transmission unit, a reception unit, a transmission/reception unit, a transceiver, or a communication unit. Furthermore, at least one of the baseband processing unit 5-20 and the RF processing unit 5-10 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 5-20 and the RF processing unit 5-10 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 5-30 stores data such as a basic program, an application program, and setting information for the operation of the terminal. In particular, the storage unit 5-30 may store information related to a second access node that performs wireless communication using a second wireless access technology. In addition, the storage unit 5-30 provides stored data according to the request of the control unit 5-40.

The controller 5-40 controls overall operations of the terminal. For example, the control unit 5-40 transmits and receives signals through the baseband processing unit 5-20 and the RF processing unit 5-10. Further, the control unit 5-40 writes and reads data in the storage unit 5-40. To this end, the control unit 5-40 may include at least one processor. For example, the controller 5-40 may include a communication processor (CP) that controls communication and an application processor (AP) that controls an upper layer such as an application program.

In addition, according to an embodiment of the present disclosure, the control unit 5-40 transmits a handover request message including a target cell identifier related to conditional handover to a target node through the transmission/reception unit, and performs conditional handover from the target node. A handover request response message including a handover command message including configuration information of a target cell for the transmission/reception unit is received, and a radio resource (RRC) including condition information for the handover command message and the conditional handover is received. control) It is possible to control to transmit a reset message to the terminal through the transmission and reception unit.

The condition information may be determined by the source node. The handover command message is transmitted through an RRC container, and the source may not modify configuration information of the target cell included in the handover command message. The handover request response message may include cell identification information of a target cell for the conditional handover, and the handover command message may include a delta setting based on source configuration information. The RRC reconfiguration message includes information for one or a plurality of cells for the conditional handover, and the condition information is based on a measurement identity consisting of a measurement object and a report configuration. Can be set.

6 is a diagram illustrating a configuration of a base station according to an embodiment of the present disclosure.

Referring to FIG. 6, the base station includes an RF processing unit 6-10, a baseband processing unit 6-20, a backhaul communication unit 6-30, a storage unit 6-40, and a control unit 6-50. Can include. The control unit 6-50 may further include a multiple connection processing unit 6-52. The base station may be an NR base station.

The RF processing unit 6-10 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 6-10 up-converts the baseband signal provided from the baseband processing unit 6-20 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 6-10 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 6-10 may include a plurality of RF chains. Furthermore, the RF processing unit 6-10 may perform beamforming. For the beamforming, the RF processing unit 6-10 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 6-20 performs a function of converting between a baseband signal and a bit string according to the physical layer standard of the first wireless access technology. For example, when transmitting data, the baseband processing unit 6-20 generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the baseband processing unit 6-20 restores a received bit stream through demodulation and decoding of the baseband signal provided from the RF processing unit 6-10. For example, in the case of the OFDM scheme, when transmitting data, the baseband processing unit 6-20 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 6-20 divides the baseband signal provided from the RF processing unit 6-10 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 6-20 and the RF processing unit 6-10 transmit and receive signals as described above. Accordingly, the baseband processing unit 6-20 and the RF processing unit 6-10 may be referred to as a transmission unit, a reception unit, a transmission/reception unit, a transceiver, a communication unit, or a wireless communication unit.

The backhaul communication unit 6-30 provides an interface for performing communication with other nodes in the network. That is, the backhaul communication unit 6-30 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 6-40 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 6-40 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 6-40 may store information that is a criterion for determining whether to provide multiple connections to the terminal or stop. In addition, the storage unit 6-40 provides stored data according to the request of the control unit 6-50.

The controller 6-50 controls overall operations of the main station. For example, the control unit 6-50 transmits and receives signals through the baseband processing unit 6-20 and the RF processing unit 6-10 or through the backhaul communication unit 6-30. Further, the control unit 6-50 writes and reads data in the storage unit 6-40. To this end, the controller 6-50 may include at least one processor.

In addition, according to an embodiment of the present disclosure, the controller 6-50 receives a handover request message including a target cell identifier related to conditional handover from a source node through the transmission/reception unit, and conditional handover to the source node. It is possible to control to transmit a handover request response message including a handover command message including configuration information of a target cell for transmission through the transceiver.

A radio resource control (RRC) reconfiguration message including the handover command message and condition information for the conditional handover may be transmitted from the source node to the terminal. The condition information may be determined by the source node. The handover command message is transmitted through an RRC container, and configuration information of the target cell included in the handover command message may not be modified by the source node. The handover request response message may include cell identification information of a target cell for the conditional handover, and the handover command message may include a delta setting based on source configuration information. The RRC reconfiguration message includes information for one or a plurality of cells for the conditional handover, and the condition information is based on a measurement identity consisting of a measurement object and a report configuration. Can be set.

<First embodiment>

FIG. 7 is a diagram illustrating a process of determining a conditional handover in a source node, transmitting a condition to a corresponding target node, and generating a handover command in the target node according to an embodiment of the present disclosure. In this case, together with the condition, the resource setting valid time is also transmitted to the corresponding target cell, and may be added to the conditional handover command and transmitted to the terminal.

Referring to FIG. 7, the communication system may include a terminal (UE), a source node (SN), and a target node (TN). The source node may determine a conditional handover (CHO) (710). After determining the conditional handover in the source node, the source node determines the corresponding target cell and transmits the HO preparation inter node message to the target node operating the target cell (720). In this case, the source node may transmit condition information to be applied to each target cell by putting it in the message. The HO preparation inter node message may be a handover request message.

The target node finally determines a candidate target cell in consideration of the possibility of handover application to target cells given from the source node, and generates a handover command message with a setting value to be applied during handover in the corresponding cells (730). At this time, for each candidate target cell, handover performance condition information transmitted to the source base station may be added. Or, if necessary, information that has been modified to this condition can be added.

This handover command message may be delivered through a handover request ack message that is an Xn message (740). In this case, the handover command message is one RRC message, and may be included in the Xn message in the form of an octet string and transmitted to the source node. As configuration information in the target cell that may be included in the handover command message, CFRA resources (e.g. for all wide/ cell specific beams, given delay between CHO configuration and execution), PCell (dedicated and common) configuration, T304 (to guard actual CHO execution phase i.e. started after condition is met), radioBearerConfig, RLC bearerConfig, MAC config, measConfig. And the like, and these can be included as a container for each target cell within one conditional handover, or a conditional handover command is created for each target cell and the corresponding information is included therein. This information is applicable to all cases of FIGS. 7, 8, 9, 10, and 11.

In addition, this (conditional) handover command message is a delta signal based on the source configuration information of the terminal at the moment this command message is delivered to the terminal. Accordingly, when the terminal receives the handover command, the newly added information is used in the target cell by overwriting, erasing, or replacing the contents of the conditional handover command message with respect to the terminal's own current configuration information. In another embodiment, the handover command message may be a delta signal based on conditional handover configuration information of the target cell previously transmitted to the terminal for each target cell. In this case, the terminal updates the configuration information for the target cell by overwriting the newly received configuration information based on the configuration information previously received for the specific target cell, or erasing or replacing the existing configuration information. This operation is also applicable to all cases of FIGS. 7, 8, 9, 10, and 11.

In the case of creating each octet string for multiple cells, a specific factor in each octet string can have the same value for each cell. In this case, for simplicity of the signal, a specific factor is another factor in the octet string list entry. May have the same indication as. A specific parameter of a specific target cell marked with this mark can refer to the value of the corresponding parameter of another cell in the octet string list.

The source node may transmit the handover command message of the octet string received from the target node as an RRC Reconfiguration message to the UE without separate decoding (750). The RRC reconfiguration message may include dedicated resource configuration information of each candidate target cell and condition information that is a basis for determining conditional handover. The terminal receiving the message starts a measurement operation according to the added condition and determines whether the condition is satisfied. When this condition is satisfied, the UE performs conditional handover to the target cell that satisfies the condition.

8 is a diagram illustrating a process of directly transmitting a condition for conditional handover to a terminal from a source node according to an embodiment of the present disclosure. In this case, together with the condition, the valid time for resource setting in the corresponding target cell may also be directly transmitted to the terminal.

Referring to FIG. 8, the communication system may include a terminal (UE), a source node (SN), and a target node (TN). The source node may determine a conditional handover (CHO) (810). After determining the conditional handover in the source node, the target cell is determined, and the HO preparation inter node message is transmitted to the target node operating the target cell (820). In this case, the source node does not deliver condition information to be applied to each target cell by putting it in the message.

The target node finally determines a candidate target cell by considering the possibility of handover application to target cells given from the source node, and generates a handover command message with a setting value to be applied when handover is applied in the corresponding cells (830). This handover command message may be delivered through a handover request ack message, which is an Xn message (840). In this case, the handover command message is one RRC message, and may be included in the Xn message in the form of an octet string and transmitted to the source node.

The source node may determine each target cell by decoding the handover command message of the octet string received from the target node, and add a condition for conditional handover to the target cell for each cell (850). The source node adds a condition for conditional handover for each cell and then transmits the RRC Reconfiguration message to the UE through the encoding process again (860). The RRC reconfiguration message may include dedicated resource configuration information of each candidate target cell and condition information that is a basis for determining conditional handover.

The terminal receiving the RRC reconfiguration message starts a measurement operation according to the added condition and determines whether the condition is satisfied. When this condition is satisfied, the UE can perform conditional handover to a target cell that satisfies the condition.

In various embodiments of the present invention, it has been described that the source node transmits an RRC reconfiguration message to the terminal, but this corresponds to an example of an RRC message, and other RRC messages may be used. In addition, when the radio access technology (RAT) of the source node of the present invention is LTE, the RRC message may be an RRC connection reconfiguration message.

9 is a diagram illustrating an operation of adding control information for a source node to a conditional handover command generated from a target node in a source node according to an embodiment of the present disclosure. In this case, together with the condition, the resource setting valid time is also transmitted to the corresponding target cell, and may be added to a conditional handover command, or a source node may be added to a separate field and transmitted to the terminal.

Referring to FIG. 9, the communication system may include a terminal (UE), a source node (SN), and a target node (TN). The source node may determine a conditional handover (CHO) (910). After determining the conditional handover in the source node, the target cell is determined, and the HO preparation inter node message is transmitted to the target node operating the target cell (920). The HO preparation inter node message may be a handover request message. At this time, the source node does not deliver condition information to be applied to each target cell by putting it in this message.

The target node finally determines a candidate target cell in consideration of the possibility of handover application to target cells given from the source node, and generates a handover command message with a setting value to be applied when handover in the cells (930). The handover command message is transmitted through a handover request ack message, which is an Xn message (940). In this case, the handover command message is one RRC message, and may be included in the Xn message in the form of an octet string and transmitted to the source node. In this case, if there is a multi-target cell, it may be included in the Xn message in the form of a list of octet strings.

Apart from the handover command message of the above octet string received from the target node, the source node may add information controlled by the source node to a separate field from the octet string (950). In this process, the octet string received from the target cell is not decoded, and the condition to perform conditional handover and other information for controlling the terminal from the source node are added to a separate field. Since the Octet string is not decoded, the source node does not modify the handover command message received from the target node or the information included in the handover command message. Information that can be entered in a separate field may be information that requires reconfiguration in the current source cell, not conditional handover configuration, or common condition information for all or some group target cells. Alternatively, the source node may transmit a conditional handover condition to the target node, and the target node may create a conditional handover command including the condition, make it an octet string, and pass it back to the source node. In this case, the conditional handover condition may not be included in a separate field for information controlled by the source node mentioned above, and configuration information for terminal configuration may be entered in the current source node.

The source node uses the field as an octet string and a separate information element and transmits the field as an integrated RRC Reconfiguration message to the UE through an encoding process (960). This RRC reconfiguration message may include dedicated resource configuration information of each or a specific group of candidate target cells, condition information that is a basis for determining conditional handover, and terminal configuration information required in a current source cell irrespective of conditional handover. . The terminal receiving the message applies the terminal configuration required in the source cell, and updates and stores the configuration information in the target cell for conditional handover. Further, a measurement operation according to a condition for the added conditional handover can be started, and a determination can be made whether the condition is satisfied. When the above condition is satisfied, the terminal may perform conditional handover to a target cell that satisfies the condition.

Table 1 below shows an example of the ASN.1 code of the RRCReconfiguration message created in this way.

RRCReconfig msg ::= seq{
sn_Control_part SN_control,
tn_HO_CMD octect string{Handover Command},
}

SN_control is control information of the terminal separately added by the source node, and condition information for handover may be included in this information. tn_HO_CMD is a handover command octet string for conditional handover received from the target node.

In all the embodiments of FIGS. 7, 8, and 9, a single target node requests multiple target cells for conditional handover. In this case, multiple target cells in the target cell global ID field of the HANDOVER REQUEST message transmitted through the Xn interface. You must add a CGI for Table 2 below shows the contents of the target cell global ID field in the HANDOVER REQUEST message. A plurality of global CGI information of each target cell may be added to the target cell global ID field using the current target node ID and the ID of the target cell operated in the target node. In addition, the handover request message may include conditional handover information or conditional handover indication information.

IE/Group Name Presence Range IE type and reference semantics description Criticality Assigned Criticality Target Cell Global ID M 9.2.3.25 includes either an E-UTRA CGI or an NR CGI YES reject

The target node receiving the message may perform admission control and dedicated resource allocation for each target cell.

10 is a diagram illustrating an operation of adding multiple cells to one conditional handover scene when preparing conditional handover for multiple cells in a source node according to an embodiment of the present disclosure.

Referring to FIG. 10, the communication system may include a terminal (UE), a source node (SN), and a target node (TN). The source node may determine a conditional handover (CHO) (1010). The source node may request the target node to prepare for handover for multiple target cells (1020). The source node may transmit a handover preparation message (handover preparation INM message) including conditions for each cell or group of cells to the target node.

When the target node makes a handover command for the target cell, it is possible to make a handover command for each target cell instead of a single handover command (1030). Each handover command is an octet string, and may be included as a separate octet string in the HANDOVER REQUEST ACKNOWLEDGE message transmitted from the target node to the source node (1040). Accordingly, the target NG-GAN node to source NG-RAN node transparent container field below may have a separate octet string through indexes of candidate target cells or target cell global IDs determined by each target node. To this end, the determined index list of target cells or the target cell CGI list may be added to the HANDOVER REQUEST ACKNOWLEDGE message, and the trans parent container field below may include multiple octet strings in the order of the corresponding list.

IE/Group Name Presence Range IE type and reference Sematics description Criticality Assigned Criticality Target NG-RAN node To Source NG-RAN node Transparent Container M OCTET STRING Either includes the HandoverCommand message as defined in subclause 10.2.2 of TS 36.331 [14], if the target NG-RAN node is an ng-eNB, or the HandoverCommand message as defined in subclause 11.2.2 of TS 38.331 [10], if the target NG-RAN node is a gNB. YES ignore

Also, in this case, the condition for each target cell can be entered into each handover command.

The source node may generate an RRC reconfiguration message including each handover command received from the target node and transmit it to the terminal (1050). In this case, the source node does not need to decode the handover command received from the target node.

11 is a diagram illustrating an operation of adding one cell to one conditional handover scene when preparing conditional handover for multiple cells in a source node according to an embodiment of the present disclosure.

Referring to FIG. 11, the communication system may include a terminal (UE), a source node (SN), and a target node (TN). The source node may determine a conditional handover (CHO) (1110). The source node requests the target node to prepare handover for multiple target cells (1120). The source node may transmit a handover preparation message (handover preparation INM message) including conditions for each cell or group of cells to the target node.

When creating a handover command for a target cell, the target node may be created by putting dedicated configuration information for multiple candidate target cells and handover condition configuration information in one handover command (1130). In this case, information on a plurality of target cells is included in the handover command message, but since it is expressed as one octet string, it is not known which target cell has been selected as a candidate target cell in the HANDOVER REQUEST ACKNOWLEDGE Xn message.

The target node may transmit a handover command message marked as a single octet string to the Xn message to the source node (1140). The source node transmits an RRC Reconfiguration message including this handover command message to the terminal without decoding (1150).

FIG. 12 is a diagram illustrating an operation regarding a field to add multi-target cell information to RRC Reconfiguration information according to an embodiment of the present disclosure.

Referring to FIG. 12, when one handover command message enters the RRC Reconfiguration message given to the UE, if this message is made of information on multiple candidate target cells, options for detailed locations for setting conditions may be provided. have. The first option is that the handover command message is included in the SpcellConfig IE, but located outside reconfigWithSync. The second option is to include the handover command message in reconfigWithSync iE, but outside spcellConfigCommon. The third option is to place the handover command message in the spcellConfigCommon IE. As a last option, the handover command message is located in cellGroupConfig and outside SpcellConfig. In particular, in this case, it can be located inside the measConfig IE, in which case, each condition can be displayed with a candidate target cell ID, that is, a physical cell ID or a CGI.

As another configuration method, dedicated resource configuration information for each candidate target cell can be listed in multiple at the SpcellConfig level by including target cell id information in SpcellConfig. Alternatively, by including the target cell id information in the reconfigWithSync level, multiple listings may be made at the reconfigWithSync level. In the latter case, dedicated configuration information of each target cell is put in reconfigWithSync, and common configuration information for a cell can be located outside reconfigWithSync of SpcellConfig without a target cell id. Alternatively, configuration information dedicated to each target cell may be delivered to SpcellConfigCommon by using the target cell id. Alternatively, by adding a target cell id to SpcellConfigDedicated inside SpcellConfig and outside reconfigWithSync, dedicated resource configuration information of the target cell may be delivered to the terminal.

In another embodiment, there may be various methods of signaling a condition to be included in the RRCReconfiguration message. Each method is necessary in order to reduce the overhead of the signal. For the current source cell and each target cell or a specific target cell group, the following options are possible.

-Opt1, signals measObject and reportConfig that fulfill each condition.

-Opt2. Refers to the measObject id currently used in the source spcell cell and signals a separate reportConfig. -Opt3. As a measObject, it signals a target cell id (CGI or physical cell id) to which the corresponding condition is applied and a separate reportConfig.

-Opt4. As a measObject, the target cell id (CGI or physical cell id) to which the corresponding condition is applied and the reportConfig id currently used in the source cell can be signaled, or the reportConfg id currently used in the source cell is signaled and only the configuration information to be changed is added. I can make it.

-Opt5. By signaling the measurement id currently used in the spcell and resetting the subfields existing in the measObject and reportConfig, it is possible to signal a field changed in the currently used configuration.

-Opt6. Without the measurement id signal currently used in spcell, the measurement object and report configuration used when reporting to add the target cell to which each condition is applied is used as a basis, and only the subfields of the measurement object and report configuration are reconfigured. Signal. The terminal recognizes this changed setting as a delta setting and applies it to measurement and condition evaluation for CHO performance conditions.

The parts that can be changed in the above options include, for example, an event type or an offset value used in each event type, a threshold value of a serving cell and a target cell, an offset value for each frequency, an offset value for each cell, and measurement of a serving and target cell. It may be a frequency to be performed, subcarrier spacing information, SMTC information, reference signal type, the maximum number of RSs or the number of beams required for beam consolidation, a threshold value of reception intensity for each beam for determining each measurement beam.

In the case of FIGS. 7, 8, 9, 10, and 11, when the terminal receives an RRCReconfiguration message, and when the source cell condition is included, the RRCReconfigurationComplete message is always transmitted to the source node. If only conditional handover-related configuration is included, when the terminal receives the reconfiguration message, the complete message may not be delivered. Instead, when a condition is triggered and conditional handover is started, a complete message can be transmitted to the target cell when the connection is successfully performed to the target cell.

13 is a signal flow diagram when only a beam level condition is given to a terminal without a cell level condition, corresponding to embodiments 2-1 and 2-2 according to an embodiment of the present disclosure. Referring to FIG. 13, a source node (serving base station) may determine to perform a conditional handover (CHO) (1305). Thereafter, the source node may send a message requesting preparation for conditional handover to the target node (1310). A message requesting preparation for conditional handover may include an indication of a handover message for conditional handover. In addition, the message for requesting preparation for conditional handover may include cell id and beam-based condition setting for a candidate cell for conditional handover.

Upon receiving the message requesting preparation for conditional handover, the target node determines whether conditional handover can be performed on the target cell indicated by the serving node, and sends a conditional handover command message by putting dedicated resource configuration information to be used in the target cell. Can be generated (1315). In addition, the conditional handover command message may include beam level condition setting information for candidate target cells capable of performing conditional handover. The target node may transmit the generated conditional handover command message to the source node (1320).

The source node may transmit the conditional handover command received from the target node to the terminal as an RRCReconfiguration message (1325). If the source node did not transmit the beam level setting condition information to the target node during the previous handover preparation process, the beam level setting condition may not be included in the handover command message. In this case, the source node directly The beam level setting condition applied to them may be added to the RRCReconfiguration message and transmitted to the terminal.

Upon receiving the RRCReconfiguration message, the UE starts measuring the intensity of the beams set in the source cell and each target cell with respect to the beams set for setting the beam level condition, and may evaluate whether the measured intensity of the beams satisfies the beam level condition (1330 , 1335, 1340).

If there is a target cell that satisfies the transmitted beam level condition while measuring the intensity of the beams, the terminal may perform conditional handover to the target cell that satisfies the beam level condition (1345). The terminal may perform random access to the target cell selected by performing conditional handover (1350).

According to the 2-1 embodiment, the serving base station (source node) may transmit configuration for conditional handover to the terminal. In this case, the serving base station may set a beam intensity-based event condition for each candidate target cell or a candidate target cell group to be a handover target. As the configuration information of the beam intensity-based condition, specific beams of a serving cell, that is, beam indexes of N Synchronization Signal Blocks (SSBs) or Channel State Information Reference Signals (CSI-RS) and/or specific beams of M corresponding target cells, That is, the index of SSB or CSI-RS may be given to the terminal. In addition, an evaluation condition for comparing the beams of the serving cell and the beams of the target cell may be given to the UE. As a unit of strength of each beam, RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), RSSI (Received Signal Strength Indicator), or Rs-SINR (Reference Signal Signal-to-Interference-and-Noise Ratio) is considered. Can be. When the above-described beam information is given to the terminal, the terminal can start measuring the beam and determine whether the measured beam satisfies the evaluation condition. If the beam of the target cell satisfies the given condition, the UE may perform handover to the target cell that satisfies the condition.

As the beam intensity evaluation condition, there may be an A1 type. As a parameter related to the A1 type, a threshold value to be compared with a beam intensity value may be set in the terminal. Given the N beam indexes, event type information, and threshold values of the serving cell, the UE measures the reception intensity of the N beams set in the serving cell, and the average value of the intensity of the N beams of the serving cell, If the minimum value of the intensity or the maximum value of the intensity of N beams is greater than a given threshold value, it may be considered that the A1 event is satisfied.

As another beam intensity evaluation condition, there may be an A2 type. As a parameter related to the A2 type, a threshold value to be compared with a beam intensity value may be set in the terminal. Given the N beam indexes, event type information, and threshold values of the serving cell, the UE measures the reception intensity of the N beams set in the serving cell, and the average value of the intensity of the N beams of the serving cell, If the minimum value of the intensity or the maximum value of the intensity of N beams is less than a given threshold value, it may be considered that the A2 event is satisfied.

As another beam intensity evaluation condition, there may be an A3 type. As a parameter related to the A3 type, an offset value for comparing the beam strength of the serving cell and the beam strength of the target cell may be set to the UE. Given the beam index of the serving cell, the beam index of the target cell, event type information, and the offset value, the UE measures the reception strength of the N set beams of the serving cell and the M set beams of the target cell, If the average value of the intensity of the N beams is smaller than the average value of the intensity of the M beams of the target cell by an offset, the A3 event may be considered to be satisfied. Alternatively, the UE has the minimum value of the intensity of the N beams of the serving cell less than the minimum value of the intensity of the M beams of the target cell by an offset, or the maximum value of the intensity of the N beams of the serving cell is the M beams of the target cell. If the intensity is smaller by offset than the maximum value, it can be considered that the A3 event is satisfied. Alternatively, the UE may consider that the A3 event is satisfied if the maximum value of the intensity of the N beams of the serving cell is less than the minimum value of the intensity of the M beams of the target cell by an offset.

As another beam intensity evaluation condition, there may be an A4 type. As a parameter related to the A4 type, a threshold value to be compared with a beam intensity value may be set in the terminal. When the index of the M beams of the target cell, event type information, and the threshold value are given, the UE measures the reception intensity of the M beams set in the target cell, and the average value or M beams of the M beams of the target cell If the minimum value or the maximum value among the intensities of the fields is greater than a given threshold value, it can be considered that the A4 event is satisfied.

As another beam intensity evaluation condition, there may be an A5 type. As parameters related to the A5 type, a threshold value to be compared with a beam intensity value of a serving cell and a threshold value to be compared with a beam intensity value of a target cell may be set in the terminal. When the terminal is given the index of the N beams of the serving cell, the threshold for the serving cell, the index of the M beams of the target cell, the threshold for the target cell, and event type information, the reception strength of the set N beams of the serving cell By measuring, the average value of the intensity of the N beams of the serving cell, the maximum value of the intensity of the N beams, or the minimum value of the intensity of the N beams is less than the threshold value for the serving cell, and reception of the M beams set in the target cell When the intensity is measured and the average value of the intensity of the M beams of the target cell, the minimum value of the intensity of the M beams, or the maximum value of the intensity of the M beams is greater than a given threshold value, it may be considered that the A5 event is satisfied.

As parameters related to the aforementioned A1 to A5 types, parameters related to the A3 type may include a measurement object specific offset and a serving cell specific offset of a serving cell, and these parameter values are in the serving cell portion of the aforementioned A3 type offset. Can be added. In addition, the parameters related to the A3 type may also include a measurement object specific offset and a target cell specific offset of the target cell, and these parameter values may be added to the target cell portion of the aforementioned A3 type offset. In addition, the parameters related to the A4 type may include the measurement object specific offset and the target cell specific offset of the target cell, and these parameter values are added to the value portion of the target beams to be compared with the threshold value of the A4 type mentioned above. Can be used. The parameters related to the A5 type may include the measurement object specific offset and the target cell specific offset of the target cell, and these parameter values are added to the value of the target beams to compare the size with the threshold for the A5 type target cell mentioned above. Can be used for

According to the 2-2 embodiment, the serving base station may transmit configuration for conditional handover to the terminal. In this case, the serving base station may set a beam intensity-based event condition to the terminal for each candidate target cell or a candidate target cell group to be a handover target. As the configuration information of the beam intensity-based condition, the number of beams N to be considered for the event determination condition in the serving cell, and/or the number of beams M to be considered for the event determination condition in the target cell may be given to the terminal. At this time, configuration information on what the RS (Reference Signal) type of each beam to be considered in the serving cell and/or the target cell may be transmitted to the UE. The configuration information on what the RS type is, may be information indicating that the RS type of each beam is SSB or CSI-RS. In addition, an evaluation condition for comparing the beams of the serving cell and the beams of the target cell may be given to the UE. As a unit of the intensity of each beam, RSRP, RSRQ, RSSI, or Rs-SINR may be considered. When the above-described information on the number of beams is given to the terminal, the terminal may start measuring all the beams corresponding to the corresponding RS type, and determine whether the measured beam satisfies the evaluation condition. If the beam of the target cell satisfies the given condition, the UE may perform handover to the target cell that satisfies the condition.

As the beam intensity evaluation condition, there may be an A1 type. As a parameter related to the A1 type, a threshold value to be compared with a beam intensity value may be set in the terminal. Given the N value of the serving cell, event type information, and threshold, the UE measures the reception intensity of all beams of the serving cell, and the intensity of the N beams with the largest reception intensity among the measured beams of the serving cell. If the average value of, the minimum of the intensity of the N beams having the highest reception intensity, or the maximum value of the intensity of the N beams having the largest reception intensity is greater than a given threshold, the A1 event may be considered to be satisfied.

As another beam intensity evaluation condition, there may be an A2 type. As a parameter related to the A2 type, a threshold value to be compared with a beam intensity value may be set in the terminal. When the N value of the serving cell, event type information, and threshold value are given, the UE measures the reception intensity of all beams of the serving cell, and the average of the intensity of the N beams with the largest reception intensity among the measured serving cell beams. If the value, the minimum of the intensity of the N beams having the highest reception intensity, or the maximum value of the intensity of the N beams having the largest reception intensity is less than a given threshold, the A2 event may be considered to be satisfied.

As another beam intensity evaluation condition, there may be an A3 type. As a parameter related to the A3 type, an offset value for comparing the beam strength of the serving cell and the beam strength of the target cell may be set to the UE. Given the number of beams N of the serving cell, the number of beams M of the target cell, event type information, and offset values, the UE measures and measures the reception strength of all beams of the serving cell and all beams of the target cell. If the average value of the intensity of the N beams with the largest reception intensity among the beams of one serving cell is less than the average intensity of the M beams with the largest reception intensity among the measured target cell beams, the A3 event is considered to be satisfied. I can. Alternatively, the terminal has a minimum value of the intensity of the N beams having the highest reception intensity of the serving cell by an offset less than the minimum value of the intensity of the M beams having the largest reception intensity of the target cell, or N having the largest reception intensity of the serving cell. If the maximum value of the intensity of the beams is smaller by an offset than the maximum value of the intensity of the M beams having the largest reception intensity of the target cell, the A3 event may be considered to be satisfied. Alternatively, the UE may consider that the A3 event is satisfied if the maximum value of the intensity of the N beams having the largest reception intensity of the serving cell is less than the minimum value of the intensity of the M beams having the largest reception intensity of the target cell.

As another beam intensity evaluation condition, there may be an A4 type. As a parameter related to the A4 type, a threshold value to be compared with a beam intensity value may be set in the terminal. Given the M-value event type information and the threshold value of the target cell, the UE measures the reception intensity of all beams of the target cell, and the average value of the M beams with the largest reception intensity among the measured beams of the target cell, reception intensity If the minimum value among the M beams having the largest reception intensity or the maximum value among the M beams having the largest reception intensity is greater than a given threshold, event A4 may be considered to be satisfied.

As another beam intensity evaluation condition, there may be an A5 type. As parameters related to the A5 type, a threshold value to be compared with a beam intensity value of a serving cell and a threshold value to be compared with a beam intensity value of a target cell may be set in the terminal. Given the N value of the serving cell, the serving cell threshold, the target cell M value, the target cell threshold, and event type information, the UE measures the reception strength of all beams of the serving cell and measures the measured serving cell. Among the beams, the average value of the intensity of the N beams having the highest reception intensity, the maximum value of the intensity of the N beams having the largest reception intensity, or the minimum value of the intensity of the N beams having the largest reception intensity is less than the serving cell threshold. Small, by measuring the reception intensity of all the beams of the target cell, the average value of the intensity of the M beams with the largest reception intensity among the measured beams of the target cell, the minimum value of the intensity of the M beams with the largest reception intensity, or the reception intensity If the maximum value of the intensities of the M beams having the largest is greater than a given threshold, it may be considered that the A5 event is satisfied.

As parameters related to the aforementioned A1 to A5 types, parameters related to the A3 type may include a measurement object specific offset of a serving cell and a specific offset of a serving cell, and these parameter values are the serving cell portion of the A3 type offset mentioned above. Can be added to In addition, parameters related to the A3 type may also include measurement object specific offset and target cell specific offset of the target cell, and these parameter values may be added to the target cell portion of the A3 type offset mentioned above. In addition, the parameters related to the A4 type may include a measurement object specific offset and a target cell specific offset of the target cell, and these parameter values are added to the value portion of the target beams to be compared with the threshold of the A4 type mentioned above. Can be used. The parameters related to the A5 type may include the measurement object specific offset and the target cell specific offset of the target cell, and these parameter values are added to the value of the target beams to compare the size with the threshold for the A5 type target cell mentioned above. Can be used for

14 is a signal flow diagram when a cell-level condition and a beam-level condition are both given to a terminal corresponding to embodiments 2-3 and 2-4 according to an embodiment of the present disclosure. Referring to FIG. 14, the source node may determine to perform a conditional handover (CHO) (1405). Thereafter, the source node may send a message requesting preparation for conditional handover to the target node (1410). A message requesting preparation for conditional handover may include an indication of a handover message for conditional handover. In addition, in a message requesting preparation for conditional handover, a cell id for a candidate cell for conditional handover and a cell and beam-based condition setting may be entered.

Upon receiving the message requesting preparation for conditional handover, the target node determines whether conditional handover can be performed on the target cell indicated by the serving node, and sends a conditional handover command message by putting dedicated resource configuration information to be used in the target cell. Can be created (1415). Also, the conditional handover command message may include cell level and beam level condition setting information for candidate target cells capable of performing conditional handover. The target node may transmit the generated conditional handover command message to the source node (1420).

The source node may transmit the conditional handover command received from the target node to the terminal as an RRCReconfiguration message (1425). If the source node did not deliver the cell and beam level setting condition information to the target node during the previous handover preparation process, the cell and beam level setting condition may not be included in the handover command message. In this case, the source node directly Cell and beam level configuration conditions applied to each candidate target node may be added to the RRCReconfiguration message and transmitted to the UE.

The terminal receiving the RRCReconfiguration message may start measuring the intensity of beams configured for the cell and beam level conditions for each candidate target cell and the source cell, and evaluate whether the measured intensity of the beams satisfies the cell and beam level conditions. (1430, 1435, 1440).

If there is a target cell that satisfies the previously delivered cell level condition while measuring the intensity of the beams, the terminal determines whether the target cell that satisfies the cell level condition again satisfies the beam level condition set for the target cell, and if the beam If a target cell that satisfies the level condition exists, conditional handover may be performed to the target cell (1445). The UE may perform random access to the target cell selected by performing conditional handover (1450).

According to the 2-3rd embodiment, the serving base station may transmit configuration for conditional handover to the terminal. In this case, the serving base station may simultaneously set a cell strength-based condition and a beam strength-based condition for each handover target candidate target cell or a candidate target cell group. Cell strength-based conditions are settings related to beam consolidation (RS type, threshold for determining the reception strength of each beam, the maximum number of beams to be considered for cell strength among beams exceeding the threshold, etc.) and A1, A2 in LTE and NR standards. , A3, A4, A5, A6 events and measurement object information and report configuration information for determining the corresponding event may be included. Separately, the serving base station may set a beam intensity-based event condition to the terminal. As configuration information of a beam intensity-based condition, specific beams of a serving cell, that is, beam indexes of N synchronization signal blocks (SSBs) or channel state information reference signals (CSI-RS) and/or specific beams of M corresponding target cells, That is, the index of SSB or CSI-RS may be given to the terminal. In addition, an evaluation condition for comparing the beams of the serving cell and the beams of the target cell may be given to the UE. As a unit of the intensity of each beam, RSRP, RSRQ, RSSI, or Rs-SINR may be considered. When the above-described beam information is given to the terminal, the terminal can start measuring the beam and determine whether the measured beam satisfies the evaluation condition.

If, for the cell strength-based condition and the beam strength-based condition, the target cell satisfies the cell strength-based condition given in the conditional handover configuration information, and the beam strength condition given to the target cell for the target cell is also satisfied, the UE Handover can be performed to a target cell that satisfies both conditions. The measurement of the cell and beam intensity may be performed when condition setting information based on the corresponding cell and beam intensity is given. If there are a plurality of target cells that satisfy the cell strength-based condition at the same time, the UE may preferentially perform handover to a target cell that satisfies a given beam strength-based condition among target cells that satisfy the cell strength-based condition.

As the beam intensity evaluation condition, there may be an A1 type. As a parameter related to the A1 type, a threshold value to be compared with a beam intensity value may be set in the terminal. Given the N beam indexes, event type information, and threshold values of the serving cell, the UE measures the reception intensity of the N beams set in the serving cell, and the average value of the intensity of the N beams of the serving cell, If the minimum value among the intensities or the maximum among the intensities of the N beams is greater than a given threshold value, it may be considered that the A1 event is satisfied.

As another beam intensity evaluation condition, there may be an A2 type. As a parameter related to the A2 type, a threshold value to be compared with a beam intensity value may be set in the terminal. Given the N beam indexes, event type information, and threshold values of the serving cell, the UE measures the reception intensity of the set N beams of the serving cell, and the average value of the intensity of the N beams of the serving cell, N beams If the minimum value of the intensity of the beams or the maximum value of the intensity of N beams is less than a given threshold value, it may be considered that the A2 event is satisfied.

As another beam intensity evaluation condition, there may be an A3 type. As a parameter related to the A3 type, an offset value for comparing the beam strength of the serving cell and the beam strength of the target cell may be set to the UE. Given the beam index of the serving cell, the beam index of the target cell, event type information, and the offset value, the UE measures the reception strength of the N set beams of the serving cell and the M set beams of the target cell, If the average value of the N beams is less than the average value of the M beams of the target cell by an offset, the A3 event may be considered to be satisfied. Alternatively, the UE has the minimum value of the intensity of the N beams of the serving cell less than the minimum value of the intensity of the M beams of the target cell by an offset, or the maximum value of the intensity of the N beams of the serving cell is the M beams of the target cell. If the intensity is smaller by offset than the maximum value, it can be considered that the A3 event is satisfied. Alternatively, the UE may consider that the A3 event is satisfied when the maximum value of the intensity of the N beams of the serving cell is less than the minimum value of the intensity of the M beams of the target cell by an offset.

As another beam intensity evaluation condition, there may be an A4 type. As a parameter related to the A4 type, a threshold value to be compared with a beam intensity value may be set in the terminal. Given the index of the M beams of the target cell, event type information, and the threshold value, the UE measures the reception intensity of the M beams set in the target cell, and the average value of the M beams of the target cell, M If the minimum value among the intensity values of the beams and the maximum value among the intensity values of M beams are greater than a given threshold value, it may be considered that the A4 event is satisfied.

As another beam intensity evaluation condition, there may be an A5 type. As parameters related to the A5 type, a threshold value to be compared with a beam intensity value of a serving cell and a threshold value to be compared with a beam intensity value of a target cell may be set in the terminal. When the terminal is given the index of the N beams of the serving cell, the threshold for the serving cell, the index of the M beams of the target cell, the threshold for the target cell, and event type information, the reception strength of the set N beams of the serving cell Is measured, the average value of the N beams of the serving cell, the maximum value of the N beams, or the minimum value of the N beams is less than the threshold value for the serving cell, and the reception intensity of the M beams set in the target cell is measured, and the target If the average value of the intensity of the M beams of the cell, the minimum value of the intensity of the M beams, or the maximum value of the intensity of the M beams is greater than a given threshold value, it may be considered that the A5 event is satisfied.

As parameters related to the aforementioned A1 to A5 types, parameters related to the A3 type may include a measurement object specific offset of a serving cell and a specific offset of a serving cell, and these parameter values are in the serving cell portion of the aforementioned A3 type offset. Can be added. In addition, parameters related to the A3 type may also include measurement object specific offset and target cell specific offset of the target cell, and these parameter values may be added to the target cell portion of the A3 type offset mentioned above. In addition, parameters related to the A4 type may include measurement object specific offset and target cell specific offset of the target cell, and these parameter values are added to the value portion of the target beams (eg, beams set to be measured in the target cell). It can be used for size comparison with the threshold of the A4 type mentioned above. The parameters related to the A5 type may include the measurement object specific offset and the target cell specific offset of the target cell, and these parameter values are added to the value of the target beams to compare the size with the threshold for the A5 type target cell mentioned above. Can be used for

As an example of the above-described third embodiment, in a handover preparation process in each target cell, contention-free random access is performed using dedicated random access configuration information for specific beams of the target cell. (contention free random access) operation can be performed. The configuration information for the contention-free random access operation includes an index of a beam capable of transmitting a contention free rach preamble, contention free preamble information to be used in the corresponding beam, time/frequency information used for preamble transmission in the corresponding beam, and among the beams. When a beam whose intensity exceeds a specific threshold value exists, threshold value information to be considered when performing contention-free random access may be included. The target cell for which conditional handover preparation is requested may set a contention-free random access resource to specific beams, and transmit a cell-based condition and a beam strength-based condition for the target cell to the corresponding conditional handover command to the terminal. have. Alternatively, by receiving the information of the target cell, the source cell may transmit cell-based and beam strength-based conditions to the terminal. The beam-based condition information may be as follows. For each target cell, as a beam strength-based condition, the A4 type evaluation condition and the index information of the beam configured to transmit the contention free random access preamble as index information of the M beams of the target cell to be used for the A4 type evaluation to the UE , As a threshold value of the A4 type, a threshold value to be evaluated for a beam when performing contention-free random access may be informed to the terminal. In this case, the UE evaluates a cell-based condition and selects a target cell that satisfies the A4 type beam strength-based condition among cells for which contention free random access is set among cells that satisfy the cell-based condition to perform conditional handover. It is possible to select first and perform conditional handover to one of the cells.

According to the 2-4 embodiment, the serving base station may transmit the configuration for conditional handover to the terminal. In this case, the serving base station may simultaneously set a cell strength-based condition and a beam strength-based condition for each handover target candidate target cell or a candidate target cell group. Cell strength-based conditions are set related to beam consolidation (RS type, threshold for determining the reception strength of each beam, the maximum number of beams to be considered for cell strength among beams exceeding the threshold, etc.) and in LTE and NR standards. The A1, A2, A3, A4, A5, and A6 events and measurement object information and report configuration information for determining the corresponding event may be included. Separately, the serving base station may set a beam intensity-based event condition to the terminal. As the configuration information of the beam intensity-based condition, the number N of beams to be considered in the event determination condition in the serving cell, and/or the number M of beams to be considered in the event determination condition in the target cell may be given to the UE. At this time, configuration information on what the RS (Reference Signal) type of each beam to be considered in the serving cell and/or the target cell may be transmitted to the UE. The configuration information on what the RS type is, may be information indicating that the RS type of each beam is SSB or CSI-RS. In addition, an evaluation condition for comparing the beams of the serving cell and the beams of the target cell may be given to the UE. As a unit of the intensity of each beam, RSRP, RSRQ, RSSI, or Rs-SINR may be considered. When the above-described information on the number of beams is given to the terminal, the terminal may start measuring all the beams corresponding to the corresponding RS type, and determine whether the measured beam satisfies the evaluation condition.

If, for the cell strength-based condition and the beam strength-based condition, the target cell satisfies the cell strength-based condition given in the conditional handover configuration information, and the beam strength condition given to the target cell for the target cell is also satisfied, the UE Handover can be performed to a target cell that satisfies both conditions. The measurement of the cell and beam intensity may be performed when condition setting information based on the corresponding cell and beam intensity is given. If there are a plurality of target cells that satisfy the cell strength-based condition at the same time, the UE may preferentially perform handover to a target cell that satisfies a given beam strength-based condition among target cells that satisfy the cell strength-based condition.

As the beam intensity evaluation condition, there may be an A1 type. As a parameter related to the A1 type, a threshold value to be compared with a beam intensity value may be set in the terminal. When the N value of the serving cell, event type information, and threshold value are given, the UE measures the reception intensity of all beams of the serving cell, and receives the average value of the N beams with the largest reception intensity among the measured beams of the serving cell. If the minimum value of the intensity of the N beams having the largest intensity or the maximum value of the intensity of the N beams having the largest reception intensity is greater than a given threshold, it may be considered that the A1 event is satisfied.

As another beam intensity evaluation condition, there may be an A2 type. As a parameter related to the A2 type, a threshold value to be compared with a beam intensity value may be set in the terminal. When the N value of the serving cell, event type information, and threshold value are given, the UE measures the reception intensity of all beams of the serving cell, and the average value of the intensity of the N beams having the largest reception intensity among the measured serving cell beams If the minimum value of the intensity of the N beams having the highest reception intensity or the maximum value of the intensity of the N beams having the largest reception intensity is less than a given threshold, the A2 event may be considered to be satisfied.

As another beam intensity evaluation condition, there may be an A3 type. As a parameter related to the A3 type, an offset value for comparing the beam strength of the serving cell and the beam strength of the target cell may be set to the UE. Given the number of beams N of the serving cell, the number of beams M of the target cell, event type information, and an offset value, the UE measures the reception strength of all beams of the serving cell and all beams of the target cell, and the measured serving cell If the average value of the intensity of the N beams having the largest reception intensity among the beams of is less than the average value of the M-beams having the largest reception intensity among the measured beams of the target cell, the A3 event may be considered to be satisfied. Alternatively, the terminal has a minimum value of the intensity of the N beams having the highest reception intensity of the serving cell by an offset less than the minimum value of the intensity of the M beams having the largest reception intensity of the target cell, or N having the largest reception intensity of the serving cell. If the maximum value of the intensity of the beams is less than the maximum value of the intensity of the M beams having the largest reception intensity of the target cell by an offset, the A3 event may be considered to be satisfied. Alternatively, the UE may consider that the A3 event is satisfied when the maximum value of the intensity of the N beams having the largest reception intensity of the serving cell is less than the minimum value of the intensity of the M beams having the largest reception intensity of the target cell.

As another beam intensity evaluation condition, there may be an A4 type. As a parameter related to the A4 type, a threshold value to be compared with a beam intensity value may be set in the terminal. When the M value of the target cell, event type information, and threshold value are given, the UE measures the reception intensity of all beams of the target cell, and the average of the intensity of the M beams having the largest reception intensity among the measured beams of the target cell If the value, the minimum of the M beams having the highest reception intensity, or the maximum of the M beams having the highest reception intensity is greater than a given threshold, the A4 event may be considered to be satisfied.

As another beam intensity evaluation condition, there may be an A5 type. As parameters related to the A5 type, a threshold value to be compared with a beam intensity value of a serving cell and a threshold value to be compared with a beam intensity value of a target cell may be set in the terminal. Given the N value of the serving cell, the serving cell threshold, the target cell M value, the target cell threshold, and event type information, the UE measures the reception strength of all beams of the serving cell and measures the measured serving cell. Among the beams, the average value of the intensity of the N beams having the highest reception intensity, the maximum value of the intensity of the N beams having the largest reception intensity, or the minimum value of the intensity of the N beams having the largest reception intensity is less than the serving cell threshold. It is small, by measuring the reception intensity of all the beams of the target cell, the average value of the intensity of the M beams having the largest reception intensity among the measured beams of the target cell, the minimum value of the intensity of the M beams having the largest reception intensity, or reception If the maximum value among the M beams having the largest intensity is greater than a given threshold value, it may be considered that the A5 event is satisfied.

As parameters related to the aforementioned A1 to A5 types, parameters related to the A3 type may include a measurement object specific offset and a serving cell specific offset of the serving cell, and these parameter values are the serving cell portion of the A3 type offset mentioned above. Can be added to In addition, parameters related to the A3 type may also include measurement object specific offset and target cell specific offset of the target cell, and these parameter values may be added to the target cell portion of the A3 type offset mentioned above. In addition, parameters related to the A4 type may include a measurement object specific offset and a target cell specific offset of the target cell, and these parameter values are added to the value portion of the target beams to be compared with the threshold value of the A4 type mentioned above. Can be used. The parameters related to the A5 type may also include the measurement object specific offset and the target cell specific offset of the target cell, and these parameter values are added to the value of the target beams to compare the size with the threshold for the A5 type target cell mentioned above. Can be used for

When a cell strength-based condition and a beam strength-based condition are simultaneously given to the conditional handover command or configuration information, when there are multiple cells satisfying the cell strength-based condition, 1) a beam level condition for each cell If there is no or is not satisfied, the UE may perform conditional handover according to the implementation of the UE or in the order of cells having a high reception strength of the beam of the target cell. Or 2) When there is a cell that satisfies the beam level condition for each cell, the UE may perform conditional handover to the cell. Or 3) When there are a plurality of cells satisfying the beam level condition for each cell, the terminal may perform conditional handover according to the implementation of the terminal or in the order of cells having a high reception strength of the beam of the target cell.

As another embodiment, an indication to consider the contention free RACH (CFRA) configuration as a beam level condition may be delivered to the terminal in an RRCReconfiguration message carrying a conditional handover command. That is, when the terminal receives an indication to consider the CFRA configuration as a beam level condition for a specific target cell or target cell group, the terminal performs cell and beam measurement, and then there are multiple target cells that satisfy the cell level condition. In this case, CFRA configuration for the target cell (ie, SSB/CSI-Rs id indicating a beam to be considered for beam strength, RSRP threshold, etc.) may be considered as a beam-based condition of the target cell. That is, if even one of the beams for determining the CFRA operation condition of a given target cell exceeds the given RSRP threshold, the corresponding target cell may be considered to satisfy the beam level condition. If there are multiple cells satisfying the beam level condition, the UE performs handover to a cell with the highest cell level reception strength among cells satisfying the beam level condition, or selects a cell to perform conditional handover as a method of implementing the UE. You can choose.

15 is a signal flow diagram of a process of performing conditional handover when a CFRA setting according to an embodiment of the present disclosure is used as a beam level condition setting. Referring to FIG. 15, the source node may determine to perform a conditional handover (1505). Thereafter, the source node may send a message requesting preparation for conditional handover to the target node (1510). A message requesting preparation for conditional handover may include an indication of a handover message for conditional handover. In addition, in a message requesting preparation for conditional handover, a cell id for a candidate cell for conditional handover and a cell and beam-based condition setting may be entered.

Upon receiving the message requesting preparation for conditional handover, the target node determines whether conditional handover can be performed on the target cell indicated by the serving node, and sends a conditional handover command message by putting dedicated resource configuration information to be used in the target cell. Can be generated (1515). Also, the conditional handover command message may include cell level and beam level condition setting information for candidate target cells capable of performing conditional handover. If CFRA setting information is configured for a specific target cell, the conditional handover command message indicates that instead of including the beam level condition setting information, the CFRA setting information for the target cell is used instead of the beam level condition setting information. (indication) may be included. The target node may transmit the generated conditional handover command message to the source node (1520).

The source node may transmit the conditional handover command received from the target node to the terminal as an RRCReconfiguration message (1525). If the source node did not deliver the cell and beam level setting condition information to the target node during the previous handover preparation process, the cell and beam level setting condition may not be included in the handover command message. In this case, the source node directly Cell and beam level configuration conditions applied to each candidate target node may be added to the RRCReconfiguration message and transmitted to the UE.

The terminal receiving the RRCReconfiguration message may start measuring the intensity of beams configured for the cell and beam level conditions for each candidate target cell and the source cell, and evaluate whether the measured intensity of the beams satisfies the cell and beam level conditions. (1530, 1535, 1540). If there is an indication in the conditional handover command message delivered through the RRCReconfiguration message that the beam level condition setting information is replaced with the CFRA setting information, the terminal is the threshold value of rsrpThresh for the beams set as the monitoring beam set in the CFRA. It may be evaluated whether an event of the A4 type to which is applied (that is, when the maximum value among the intensity of beams set in the target cell exceeds the rsrpThresh threshold value) is satisfied.

If there is a target cell that satisfies the previously delivered cell level condition while measuring the intensity of the beams, the UE uses the beam level condition (CFRA as the beam level condition) that the target cell that satisfies the cell level condition is set to the target cell again. When there is an indication, it is determined whether the A4 type event) is satisfied, and if there is a target cell that satisfies the beam level condition, conditional handover may be performed to the target cell (1545). The UE may perform random access to the target cell selected by performing conditional handover (1550).

16 is a diagram illustrating an operation of performing conditional handover in a terminal in consideration of beam level and cell level conditions according to an embodiment of the present disclosure. When the terminal receives a conditional handover (CHO) command (1605), it is possible to check whether the received command includes only a cell level condition or a beam level condition (1610). If the conditional handover command includes only the cell level condition, the UE may perform signal strength measurement for reference signals set for cell level reception strength measurement for each candidate target cell and serving cell. (1615). If a cell that satisfies the cell-level condition is found during signal strength measurement (1620), the UE may perform conditional handover to the cell (1625). If the conditional handover command includes a beam level condition together with a cell level condition (1630), the UE performs a reference signal (RS) and beam level strength measurement for measuring the cell level strength set for the candidate target cell and the source cell. The strength of the RS for can be measured (1635). If the cell-level condition is satisfied (1640), the terminal may check whether a given beam level condition of each cell is satisfied by targeting only cells in which the cell-level condition is satisfied (1645). If there is a cell that satisfies the beam level condition, the UE may select one of the corresponding cells and perform conditional handover (1650). If the cell level condition is satisfied, but there is no cell that satisfies the beam level condition, the UE may perform conditional handover by selecting one of the target cells that satisfy the cell level condition (1655). If the conditional handover command does not include a cell-level condition or a beam-level condition, the terminal may only perform reconfiguration of the terminal using other reconfiguration information (1660).

The methods according to the embodiments described in the claims or specification of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. One or more programs stored in a computer-readable storage medium are configured to be executable by one or more processors in an electronic device (device). The one or more programs include instructions that cause the electronic device to execute methods according to embodiments described in the claims or specification of the present disclosure.

These programs (software modules, software) include random access memory, non-volatile memory including flash memory, read only memory (ROM), and electrically erasable programmable ROM. (EEPROM: Electrically Erasable Programmable Read Only Memory), magnetic disc storage device, Compact Disc-ROM (CD-ROM), Digital Versatile Discs (DVDs), or other types of It may be stored in an optical storage device or a magnetic cassette. Alternatively, it may be stored in a memory composed of a combination of some or all of them. In addition, a plurality of configuration memories may be included.

In addition, the program is accessed through a communication network such as the Internet, Intranet, LAN (Local Area Network), WLAN (Wide LAN), or SAN (Storage Area Network), or a communication network composed of a combination thereof. It may be stored in an (access) attachable storage device. Such a storage device may access a device performing an embodiment of the present disclosure through an external port. In addition, a separate storage device on the communication network may access a device performing an embodiment of the present disclosure.

In the specific embodiments of the present disclosure described above, components included in the present disclosure are expressed in the singular or plural according to the specific embodiments presented. However, the singular or plural expression is selected appropriately for the situation presented for convenience of description, and the present disclosure is not limited to the singular or plural constituent elements, and even constituent elements expressed in plural are composed of the singular or in the singular. Even the expressed constituent elements may be composed of pluralities.

In addition, the embodiments disclosed in the present specification and the drawings are merely provided with specific examples for easy explanation and understanding of the contents of the present disclosure, and are not intended to limit the scope of the present disclosure. Therefore, the scope of the present disclosure should be construed that all changes or modified forms derived based on the technical features of the present disclosure in addition to the embodiments disclosed herein are included in the scope of the present disclosure.

Claims (20)

In a method performed by a source node in a wireless communication system,
Transmitting a handover request message including a target cell identifier related to conditional handover to a target node;
Receiving a handover request response message including a handover command message including configuration information of a target cell for conditional handover from the target node;
And transmitting a radio resource control (RRC) reconfiguration message including condition information for the handover command message and the conditional handover to the terminal. The method of claim 1,
And the condition information is determined by the source node. The method of claim 1,
The handover command message is delivered through an RRC container,
And the source does not modify configuration information of the target cell included in the handover command message. The method of claim 1,
The handover request response message includes cell identification information of a target cell for the conditional handover,
Wherein the handover command message includes a delta setting based on source setting information. The method of claim 1,
The RRC reconfiguration message includes information for one or a plurality of cells for the conditional handover,
The condition information is set based on a measurement identity consisting of a measurement object and a report configuration. In the source node of the wireless communication system,
A transceiver; And
A hand that transmits a handover request message including a target cell identifier related to conditional handover to a target node through the transceiver, and includes a handover command message including configuration information of a target cell for conditional handover from the target node An over request response message is received through the transceiver, and a radio resource control (RRC) reset message including condition information for the handover command message and the conditional handover is controlled to be transmitted to the terminal through the transceiver. Source node. The method of claim 6,
The source node, characterized in that the condition information is determined by the source node. The method of claim 6,
The handover command message is delivered through an RRC container,
The source node, wherein the source does not modify configuration information of the target cell included in the handover command message. The method of claim 6,
The handover request response message includes cell identification information of a target cell for the conditional handover,
Wherein the handover command message includes a delta setting based on source setting information. The method of claim 6,
The RRC reconfiguration message includes information for one or a plurality of cells for the conditional handover,
The condition information is a source node, characterized in that it is set based on a measurement identity (measurement identity) consisting of a measurement object (measurement object) and report configuration (report configuration). In a method performed by a target node in a wireless communication system,
Receiving a handover request message including a target cell identifier related to conditional handover from a source node; And
Transmitting a handover request response message including a handover command message including configuration information of a target cell for conditional handover to the source node,
A method characterized in that the handover command message and a radio resource control (RRC) reconfiguration message including condition information for the conditional handover is transmitted from the source node to the terminal. The method of claim 11,
And the condition information is determined by the source node. The method of claim 11,
The handover command message is delivered through an RRC container,
The method of claim 1, wherein the setting information of the target cell included in the handover command message is not modified by the source node. The method of claim 11,
The handover request response message includes cell identification information of a target cell for the conditional handover,
Wherein the handover command message includes a delta setting based on source setting information. The method of claim 11,
The RRC reconfiguration message includes information for one or a plurality of cells for the conditional handover,
The condition information is set based on a measurement identity consisting of a measurement object and a report configuration. In the target node of the wireless communication system,
A transceiver; And
A hand that receives a handover request message including a target cell identifier related to conditional handover from a source node through the transceiver, and includes a handover command message including configuration information of a target cell for conditional handover to the source node Including a control unit for controlling to transmit an over request response message through the transmission and reception unit,
A target node, wherein a radio resource control (RRC) reconfiguration message including the handover command message and condition information for the conditional handover is transmitted from the source node to the terminal. The method of claim 16,
The condition information is determined by the source node. The method of claim 16,
The handover command message is delivered through an RRC container,
The target node, wherein the setting information of the target cell included in the handover command message is not modified by the source node. The method of claim 16,
The handover request response message includes cell identification information of a target cell for the conditional handover,
Wherein the handover command message includes a delta setting based on source setting information. The method of claim 16,
The RRC reconfiguration message includes information for one or a plurality of cells for the conditional handover,
The condition information is set based on a measurement identity consisting of a measurement object and a report configuration.

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