KR20230000767A - Apparatus and method for performing a handover in a wireless communication system - Google Patents

Abstract

The present disclosure relates to a 5G (5^th generation) or pre-5G (5^th generation) communication system to support higher data rates after a 4G (4^th generation) communication system such as long-term evolution (LTE). According to various embodiments of the present disclosure, a method of operating a network node in a wireless communication system comprises processes of: receiving conditional handover configuration information or receiving DU configuration information before performing handover; and applying the DU configuration information when performing conditional handover. The present disclosure provides a method and device for performing handover using conditional handover settings when a combined node of backhaul and access haul performs handover in a wireless communication system.

Description

APPARATUS AND METHOD FOR PERFORMING A HANDOVER IN A WIRELESS COMMUNICATION SYSTEM

The present disclosure generally relates to a wireless communication system, and more particularly, to a method and apparatus for performing handover using conditional handover configuration when a joint node of a back haul and an access hole performs handover in a wireless communication system. It is about.

Efforts are being made to develop an improved ^5th generation ( ^5G ) communication system or a pre-5G communication system in order to meet the growing demand for wireless data traffic after the commercialization of a 4th generation (4G) communication system. For this reason, the 5G communication system or pre-5G communication system has been called a Beyond 4G Network communication system or a Post LTE system.

In order to achieve a high data rate, the 5G communication system is being considered for implementation in a mmWave band (eg, a 60 gigabyte (60 GHz) band). In order to mitigate the path loss of radio waves and increase the propagation distance of radio waves in the ultra-high frequency band, beamforming, massive MIMO, and Full Dimensional MIMO (FD-MIMO) are used in 5G communication systems. ), array antenna, analog beam-forming, and large scale antenna technologies are being discussed.

In addition, to improve the network of the system, in the 5G communication system, an evolved small cell, an advanced small cell, a cloud radio access network (cloud RAN), and an ultra-dense network , Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, CoMP (Coordinated Multi-Points), and reception interference cancellation etc. are being developed.

In addition, in the 5G system, Advanced Coding Modulation (ACM) methods such as FQAM (Hybrid Frequency Shift Keying and Quadrature Amplitude Modulation) and SWSC (Sliding Window Superposition Coding) and advanced access technology FBMC (Filter Bank Multi Carrier) ), Non Orthogonal Multiple Access (NOMA), and Sparse Code Multiple Access (SCMA) are being developed.

Based on the above discussion, the present disclosure provides a method and apparatus for performing handover using conditional handover configuration when a joint node of a back hall and an access hall performs handover in a wireless communication system. do.

According to various embodiments of the present disclosure, in a method of operating a network node in a wireless communication system, a process of receiving conditional handover setting information or receiving DU setting information prior to performing a handover, and performing conditional handover A method including a process of applying DU configuration information is provided.

According to various embodiments of the present disclosure, an apparatus of a network node in a wireless communication system includes a transceiver and at least one processor, wherein the at least one processor performs reception of conditional handover configuration information or prior to performing handover. An apparatus configured to receive DU configuration information and apply the DU configuration information when performing conditional handover is provided.

Apparatus and method according to various embodiments of the present disclosure may provide a method and apparatus for performing handover using a conditional handover setting when a handover node of a back hall and an access hall performs handover in a wireless communication system. .

Effects obtainable in the present disclosure are not limited to the effects mentioned above, and other effects not mentioned may be clearly understood by those skilled in the art from the description below. will be.

1 shows the structure of a wireless communication system according to an embodiment of the present disclosure.
2 illustrates a radio protocol structure of a wireless communication system according to an embodiment of the present disclosure.
3 shows the structure of a wireless communication system according to an embodiment of the present disclosure.
4 illustrates a radio protocol structure of a wireless communication system according to an embodiment of the present disclosure.
5 illustrates a structure of a terminal in a wireless communication system according to an embodiment of the present disclosure.
6 illustrates a structure of a base station in a wireless communication system according to an embodiment of the present disclosure.
7 illustrates a migration process of an IAB node in a wireless communication system.
8 illustrates a process of receiving and applying DU and BAP configuration information after accessing a target parent node when conditional handover is applied to IAB migration in a wireless communication system according to an embodiment of the present disclosure.
9 illustrates a process of transferring DU and BAP configuration information through an RRC signal when conditional handover is applied to IAB migration in a wireless communication system according to an embodiment of the present disclosure.
10 illustrates a process of transferring DU and BAP configuration information through an F1AP signal when conditional handover is applied to IAB migration in a wireless communication system according to an embodiment of the present disclosure.
11 illustrates a process of transmitting RRCReconfiguration using an RRC signal in a wireless communication system according to an embodiment of the present disclosure.
12 illustrates a process of transmitting RRCReconfiguration using an F1-AP in a wireless communication system according to an embodiment of the present disclosure.

Terms used in the present disclosure are only used to describe a specific embodiment, and may not be intended to limit the scope of other embodiments. Singular expressions may include plural expressions unless the context clearly dictates otherwise. Terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by one of ordinary skill in the art described in this disclosure. Among the terms used in the present disclosure, terms defined in general dictionaries may be interpreted as having the same or similar meanings as those in the context of the related art, and unless explicitly defined in the present disclosure, ideal or excessively formal meanings. not be interpreted as In some cases, even terms defined in the present disclosure cannot be interpreted to exclude embodiments of the present disclosure.

In various embodiments of the present disclosure described below, a hardware access method is described as an example. However, since various embodiments of the present disclosure include technology using both hardware and software, various embodiments of the present disclosure do not exclude software-based access methods.

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, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present disclosure, the detailed description will be omitted. In addition, terms to be described later are terms defined in consideration of functions in the present disclosure, which may vary according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout this specification.

A term used in the following description to identify a connection node, a term referring to network entities, a term referring to messages, a term referring to an interface between network entities, and a term referring to various types of identification information. Etc. are illustrated for convenience of description. Accordingly, the present disclosure is not limited to the terms described below, and other terms denoting objects having equivalent technical meanings may be used.

For convenience of description below, the present disclosure uses terms and names defined in the 3GPP LTE (3rd Generation Partnership Project Long Term Evolution) standard. However, the present disclosure is not limited by the above terms and names, and may be equally applied to systems conforming to other standards. In the present disclosure, eNB may be used interchangeably with gNB for convenience of description. That is, a base station described as an eNB may indicate a gNB. Also, the term terminal may refer to cell phones, NB-IoT devices, sensors, as well as other wireless communication devices.

Advantages and features of the present disclosure, and methods for achieving them, will become clear with reference to embodiments described below in detail in conjunction with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below and may be implemented in various different forms, only the present embodiments make the disclosure of the present disclosure complete, and the common knowledge in the art to which the present disclosure belongs It is provided to fully inform the possessor of the scope of the disclosure, and the disclosure is only defined by the scope of the claims. Like reference numbers designate like elements throughout the specification.

At this time, it will be understood that each block of the process flow chart diagrams and combinations of the flow chart diagrams can be performed by computer program instructions. These computer program instructions may be embodied in a processor of a general purpose computer, special purpose computer, or other programmable data processing equipment, so that the instructions executed by the processor of the computer or other programmable data processing equipment are described in the flowchart block(s). It creates means to perform functions. These computer program instructions may also be stored in a computer usable or computer readable memory that can be directed to a computer or other programmable data processing equipment to implement functionality in a particular way, such that the computer usable or computer readable memory The instructions stored in are also capable of producing an article of manufacture containing instruction means that perform the functions described in the flowchart block(s). The computer program instructions can also be loaded on a computer or other programmable data processing equipment, so that a series of operational steps are performed on the computer or other programmable data processing equipment to create a computer-executed process to generate computer or other programmable data processing equipment. Instructions for performing processing equipment may also provide steps for performing the functions described in the flowchart block(s).

Additionally, each block may represent a module, segment, or portion of code that includes one or more executable instructions for executing specified logical function(s). It should also be noted that in some alternative implementations it is possible for the functions mentioned in the blocks to occur out of order. For example, it is possible that two blocks shown in succession may in fact be performed substantially concurrently, or that the blocks may sometimes be performed in reverse order depending on their function.

At this time, the term '~unit' used in this embodiment means 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. '~bu' may be configured to be in an addressable storage medium and may be configured to reproduce one or more processors. Therefore, 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, databases, data structures, tables, arrays, and variables. Functions provided within components and '~units' may be combined into smaller numbers of components and '~units' or further separated into additional components and '~units'. In addition, components and '~units' may be implemented to play one or more CPUs in a device or a secure multimedia card. Also, in the embodiment, '~ unit' may include one or more processors.

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

A term used in the following description to identify a connection node, a term referring to network entities, a term referring to messages, a term referring to an interface between network entities, and a term referring to various types of identification information. Etc. are illustrated for convenience of description. Accordingly, the present disclosure is not limited to the terms described below, and other terms referring to objects having equivalent technical meanings may be used. For example, in the following description, a terminal may refer to a MAC entity in a terminal that exists for each Master Cell Group (MCG) and Secondary Cell Group (SCG), which will be described later.

Hereinafter, a base station is a subject that performs resource allocation of a terminal, and may be at least one of a gNode B, an eNode B, a Node B, a base station (BS), a wireless access unit, a base station controller, or a node on a network. The terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smart phone, a computer, or a multimedia system capable of performing communication functions. Of course, it is not limited to the above example.

In particular, the present disclosure is applicable to 3GPP NR (5th generation mobile communication standard). In addition, the present disclosure provides intelligent services (e.g., smart home, smart building, smart city, smart car or connected car, health care, digital education, retail, security and safety related services) based on 5G communication technology and IoT related technology. etc.) can be applied. In the present disclosure, eNB may be used interchangeably with gNB for convenience of description. That is, a base station described as an eNB may indicate a gNB. In addition, the term terminal may refer to mobile phones, NB-IoT devices, sensors, as well as other wireless communication devices.

The wireless communication system has moved away from providing voice-oriented services in the early days and, for example, 3GPP's HSPA (High Speed Packet Access), LTE (Long Term Evolution or E-UTRA (Evolved Universal Terrestrial Radio Access)), LTE-Advanced (LTE-A), LTE-Pro, 3GPP2's High Rate Packet Data (HRPD), UMB (Ultra Mobile Broadband), and IEEE's 802.16e, a broadband wireless network that provides high-speed, high-quality packet data services. evolving into a communication system.

As a representative example of a broadband wireless communication system, in an LTE system, an Orthogonal Frequency Division Multiplexing (OFDM) method is employed in downlink (DL), and Single Carrier Frequency Division Multiplexing (SC-FDMA) in uplink (UL). ) method is used. Uplink refers to a radio link in which a terminal (UE; User Equipment or MS; Mobile Station) transmits data or control signals to a base station (eNode B or BS; Base Station), and downlink refers to a radio link in which a base station transmits data or control signals to a terminal. A radio link that transmits signals. The multiple access method as described above distinguishes data or control information of each user by allocating and operating time-frequency resources to carry data or control information for each user so that they do not overlap each other, that is, so that orthogonality is established. .

As a future communication system after LTE, that is, a 5G communication system, since it should be able to freely reflect various requirements such as users and service providers, a service that satisfies various requirements at the same time must be supported. Services considered for the 5G communication system include Enhanced Mobile BroadBand (eMBB), massive Machine Type Communication (mMTC), Ultra Reliability Low Latency Communication (URLLC), etc. there is

According to some embodiments, eMBB may aim to provide a data transmission rate that is more improved than that supported by existing LTE, LTE-A, or LTE-Pro. For example, in a 5G communication system, an eMBB must be able to provide a peak data rate of 20 Gbps in downlink and a peak data rate of 10 Gbps in uplink from the perspective of one base station. In addition, the 5G communication system may need to provide a user perceived data rate while providing a maximum transmission rate. In order to satisfy these requirements, the 5G communication system may require improvement of various transmission and reception technologies, including a more advanced Multi Input Multi Output (MIMO) transmission technology. In addition, while signals are transmitted using a maximum 20MHz transmission bandwidth in the 2GHz band currently used by LTE, the 5G communication system uses a frequency bandwidth wider than 20MHz in a frequency band of 3 to 6GHz or 6GHz or higher to meet the requirements of the 5G communication system. data transfer rate can be satisfied.

At the same time, mMTC is being considered to support application services such as Internet of Things (IoT) in 5G communication systems. In order to efficiently provide the Internet of Things, mMTC may require support for large-scale terminal access within a cell, improved terminal coverage, improved battery time, and reduced terminal cost. Since the Internet of Things is attached to various sensors and various devices to provide communication functions, it must be able to support a large number of terminals (eg, 1,000,000 terminals/km2) in a cell. In addition, due to the nature of the service, terminals supporting mMTC are likely to be located in shadow areas that are not covered by cells, such as the basement of a building, so a wider coverage than other services provided by the 5G communication system may be required. A terminal supporting mMTC must be composed of a low-cost terminal, and since it is difficult to frequently replace a battery of the terminal, a very long battery life time such as 10 to 15 years may be required.

Finally, in the case of URLLC, as a cellular-based wireless communication service used for a specific purpose (mission-critical), remote control for robots or machinery, industrial automation, It can be used for services used in unmanned aerial vehicles, remote health care, and emergency alerts. Therefore, communications provided by URLLC may need to provide very low latency (ultra-low latency) and very high reliability (ultra-reliability). For example, a service supporting URLLC must satisfy an air interface latency of less than 0.5 milliseconds, and at the same time may have a requirement of a packet error rate of 10-5 or less. Therefore, for the service supporting URLLC, the 5G system must provide a transmit time interval (TTI) that is smaller than that of other services, and at the same time, design that allocates wide resources in the frequency band to secure the reliability of the communication link. items may be requested.

The three services considered in the aforementioned 5G communication system, that is, eMBB, URLLC, and mMTC, can be multiplexed and transmitted in one system. At this time, different transmission/reception techniques and transmission/reception parameters may be used between services in order to satisfy different requirements of each service. However, the above-mentioned mMTC, URLLC, and eMBB are only examples of different service types, and the service types to which the present disclosure is applied are not limited to the above-mentioned examples.

In addition, although the embodiments of the present disclosure are described below using LTE, LTE-A, LTE Pro, or 5G (or NR, next-generation mobile communication) systems as examples, other communication systems having a similar technical background or channel type are also subject to the present disclosure. An embodiment of may be applied. In addition, the embodiments of the present disclosure can be applied to other communication systems through some modification within a range that does not greatly deviate from the scope of the present disclosure as judged by a skilled person with technical knowledge.

According to various embodiments of the present disclosure, when a backhaul and access hall combination node needs to move a connection to another parent node according to mobility or channel conditions in a wireless communication system, a mobile termination (MT) part establishes a connection by an existing handover operation. However, the DU (distributed unit) included in the same IAB node must receive new configuration through the new parent node. At this time, the DU cannot operate until the new configuration is applied, and child IAB nodes or accessing terminals connected to this IAB node may not receive service from the network.

According to various embodiments of the present disclosure, when the migrating IAB node performs handover, when receiving configuration information through RRC before handover, information for configuring DUs is also received, or before handover can be received Through this, when performing the handover of the MT part, it is possible to apply the configuration information of the previously delivered DU.

According to various embodiments of the present disclosure, DU configuration is performed by receiving DU configuration information prior to reception of conditional handover configuration information or performing handover in a wireless communication system and applying DU configuration information when conditional handover is performed. Existing data service delay time due to reception and application after RRC connection can be reduced.

1 shows the structure of a wireless communication system according to an embodiment of the present disclosure. Specifically, FIG. 1 shows the structure of a 4G LTE system.

Referring to FIG. 1, as shown, the radio access network of the LTE system includes a next-generation base station (Evolved Node B, hereinafter ENB, Node B or base station) 105, 110, 115, and 120 and a mobility management entity (Mobility Management Entity, MME) 125 and S-GW 130 (Serving-Gateway). A user equipment (UE or terminal) 135 may access an external network through the ENBs 105 to 120 and the S-GW 130 .

In FIG. 1, ENBs 105 to 120 may correspond to existing Node Bs of the UMTS system. The ENB is connected to the UE 135 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 Internet protocol can be serviced through a shared channel. Accordingly, a device for performing scheduling by collecting status information such as buffer status, available transmit power status, and channel status of UEs may be needed, and ENBs 105 to 120 may be in charge of this. One ENB can typically control multiple cells. For example, in order to implement a transmission rate of 100 Mbps, an LTE system may use orthogonal frequency division multiplexing (OFDM) as a radio access technology in a 20 MHz bandwidth, for example. In addition, the ENB may apply an Adaptive Modulation & Coding (AMC) method that determines a modulation scheme and a channel coding rate according to the channel condition of the terminal. The S-GW 130 is a device that provides a data bearer, and can create or remove a data bearer under the control of the MME 125 . The MME is a device in charge of various control functions as well as a mobility management function for a terminal, and may be connected to a plurality of base stations.

2 illustrates a radio protocol structure of a wireless communication system according to an embodiment of the present disclosure. Specifically, FIG. 2 shows a radio protocol structure of a 4G LTE system.

Referring to FIG. 2, the radio protocols of the LTE system include Packet Data Convergence Protocol (PDCP) 205 and 240 and Radio Link Control (RLC) 210 and 235 in the terminal and ENB, respectively. , medium access control (MAC) (215, 230) and physical (Physical, PHY) devices (or layers) (220, 225). Of course, it is not limited to the above example, and may include fewer or more devices than the above example.

According to an embodiment of the present disclosure, PDCP may be in charge of operations such as IP header compression/restoration. The main functions of PDCP can be summarized as follows. Of course, it is not limited to the following examples.

- Header compression and decompression: ROHC (RObust Header Compression) only

- Transfer of user data

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

- 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)

- Ciphering and deciphering

- Timer-based SDU discard in uplink.

According to an embodiment, the radio link control (RLC) units 210 and 235 may perform an ARQ operation by reconstructing a PDCP packet data unit (PDU) into an appropriate size. The main functions of RLC can be summarized as follows. Of course, it is not limited to the following examples.

- 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

According to an embodiment, the MACs 215 and 230 are connected to several RLC layer devices configured in one terminal, and may perform operations of multiplexing RLC PDUs to MAC PDUs and demultiplexing RLC PDUs from MAC PDUs. The main functions of MAC can be summarized as follows. Of course, it is not limited to the following examples.

- 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

- 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 (Padding)

According to an embodiment, the physical layers 220 and 225 channel-code and modulate higher-layer data, convert OFDM symbols into OFDM symbols, and transmit them through a radio channel, or demodulate OFDM symbols received through a radio channel and channel-decode the higher-layer data. You can perform the forwarding operation. Of course, it is not limited to the above examples.

3 shows the structure of a wireless communication system according to an embodiment of the present disclosure. Specifically, FIG. 3 shows the structure of a 5G NR system.

Referring to FIG. 3, the radio access network of the next-generation mobile communication system (hereinafter referred to as NR or 5g) includes a next-generation base station (New Radio Node B, hereinafter referred to as NR gNB or NR base station) 310 and a next-generation radio core network (New Radio Core Network, NR CN) (305). A next-generation radio user equipment (New Radio User Equipment, NR UE or terminal) 315 can access an external network through the NR gNB 310 and the NR CN 305 .

In FIG. 3 , the NR gNB 310 may correspond to an evolved Node B (eNB) of an existing LTE system. The NR gNB 310 is connected to the NR UE 315 through a radio channel and can provide superior service to the existing Node B. In a next-generation mobile communication system, all user traffic can be serviced through a shared channel. Accordingly, a device for performing scheduling by collecting status information such as buffer status, available transmission power status, and channel status of UEs may be required, and the NR NB 310 may be in charge of this. One NR gNB 310 may control a plurality of cells. In a next-generation mobile communication system, a bandwidth higher than the current maximum bandwidth may be applied in order to implement high-speed data transmission compared to current LTE. In addition, orthogonal frequency division multiplexing (OFDM) can be used as a radio access technology, and beamforming technology can be additionally used.

In addition, according to some embodiments, the NR gNB determines a modulation scheme and a channel coding rate according to the channel condition of the terminal. Adaptive Modulation & Coding (AMC) scheme this may apply. The NR CN 305 may perform functions such as mobility support, bearer setup, and QoS setup. The NR CN 305 is a device in charge of various control functions as well as a mobility management function for a terminal, and may be connected to a plurality of base stations. In addition, the next-generation mobile communication system can be interworked with the existing LTE system, and the NR CN can be connected to the MME 325 through a network interface. The MME may be connected to the eNB 330, which is an existing base station.

4 illustrates a radio protocol structure of a wireless communication system according to an embodiment of the present disclosure. Specifically, FIG. 4 shows the radio protocol structure of the NR system.

Referring to FIG. 4, the radio protocols of the next-generation mobile communication system include NR Service Data Adaptation Protocol (SDAP) 401 and 445, NR PDCP 405 and 440, and NR RLC ( 410 and 435), NR MACs 415 and 430 and NR PHYs 420 and 425 devices (or layers). Of course, it is not limited to the above example, and may include fewer or more devices than the above example.

According to one embodiment, the main functions of the NR SDAPs 401 and 445 may include some of the following functions. However, it is not limited to the following examples.

- Transfer of user plane data

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

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

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

For the SDAP layer device, the UE uses a Radio Resource Control (RRC) message for each PDCP layer device, each bearer, or each logical channel, whether to use the header of the SDAP layer device or whether to use the function of the SDAP layer device can be set. In addition, when the SDAP header is set in the SDAP layer device, the terminal sets the Non-Access Stratum (NAS) Quality of Service (QoS) reflection setting 1-bit indicator (NAS reflective QoS) of the SDAP header and the access layer (Access Stratum) Stratum, AS) With a 1-bit QoS reflection setting indicator (AS reflective QoS), the terminal may be instructed to update or reset mapping information for uplink and downlink QoS flows and data bearers. According to some embodiments, the SDAP header may include QoS flow ID information indicating QoS. According to some embodiments, QoS information may be used as data processing priority and scheduling information to support smooth service.

According to one embodiment, the main functions of the NR PDCPs 405 and 440 may include some of the following functions. However, it is not limited to the following examples.

- 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

- PDCP PDU reordering for reception

- Duplicate detection of lower layer SDUs

- Retransmission of PDCP SDUs

- 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 forwarding data to a higher layer in the rearranged order, or may include a function of directly forwarding data without considering the order, and rearranging the order may cause loss It may include a function of recording lost PDCP PDUs, a function of reporting the status of lost PDCP PDUs to the transmitting side, and a function of requesting retransmission of lost PDCP PDUs. there is.

According to some embodiments, main functions of the NR RLCs 410 and 435 may include some of the following functions. However, it is not limited to the following examples.

- 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

- Error detection function (Protocol error detection)

- RLC SDU discard function (RLC SDU discard)

- RLC re-establishment

In the above description, the in-sequence delivery function of the NR RLC device may refer to a function of sequentially delivering RLC SDUs received from a lower layer to an upper layer. Originally, when one RLC SDU is 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 them.

The in-sequence delivery function 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), and rearranging the order results in loss It may include a function of recording lost RLC PDUs, a function of reporting the status of lost RLC PDUs to the transmitting side, and a function of requesting retransmission of lost RLC PDUs. there is.

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

In-sequence delivery of the NR RLC device, if a predetermined timer expires even if there is a lost RLC SDU, all RLC SDUs received before the timer starts can be sequentially delivered to the upper layer. there is.

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

The NR RLC device may process RLC PDUs in the order in which they are received regardless of the order of sequence numbers (out-of sequence delivery) and deliver 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 later, reconstruct 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, the out-of-sequence delivery of the NR RLC device may mean a function of immediately delivering RLC SDUs received from a lower layer to an upper layer regardless of order. Out-of-sequence delivery of the NR RLC device may include a function of reassembling and delivering, when originally one RLC SDU is divided into several RLC SDUs and received. The out-of-sequence delivery function of the NR RLC device may include a function of storing RLC SNs or PDCP SNs of received RLC PDUs and arranging the order to record lost RLC PDUs.

According to some embodiments, the NR MACs 415 and 430 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. However, it is not limited to the following examples.

- Mapping between logical channels and transport channels

- Multiplexing/demultiplexing of MAC SDUs

- Scheduling information reporting

- 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 (Padding)

The NR PHY layers 420 and 425 channel-code and modulate higher-layer data, make OFDM symbols and transmit them through a radio channel, or demodulate OFDM symbols received through a radio channel, channel-decode, and transmit the data to a higher layer. can be done Of course, it is not limited to the above examples.

5 illustrates a structure of a terminal in a wireless communication system according to an embodiment of the present disclosure.

Referring to FIG. 5 , a terminal may include a radio frequency (RF) processing unit 510, a baseband processing unit 520, a storage unit 530, and a control unit 540. In addition, the control unit 540 may further include a multiple connection processing unit 542 . Of course, it is not limited to the above example, and the terminal may include fewer or more configurations than the configuration shown in FIG. 5 .

The RF processing unit 510 may perform functions for transmitting and receiving signals through a wireless channel, such as band conversion and amplification of signals. That is, the RF processor 510 up-converts the baseband signal provided from the baseband processor 520 into an RF band signal, transmits the signal through an antenna, and down-converts the RF band signal received through the antenna into a baseband signal. can do. For example, the RF processor 510 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a digital to analog converter (DAC), an analog to digital converter (ADC), and the like. Of course, it is not limited to the above example. In FIG. 5, only one antenna is shown, but the terminal may include a plurality of antennas. Also, the RF processor 510 may include a plurality of RF chains. Also, the RF processor 510 may perform beamforming. For beamforming, the RF processor 510 may adjust the phase and magnitude of signals transmitted and received through a plurality of antennas or antenna elements. In addition, the RF processing unit 510 may perform Multi Input Multi Output (MIMO), and may receive several layers when performing the MIMO operation.

The baseband processing unit 520 performs a conversion function between a baseband signal and a bit stream according to the physical layer standard of the system. For example, during data transmission, the baseband processing unit 520 generates complex symbols by encoding and modulating a transmission bit stream. Also, when receiving data, the baseband processing unit 520 may demodulate and decode the baseband signal provided from the RF processing unit 510 to restore the received bit stream. For example, in the case of orthogonal frequency division multiplexing (OFDM), during data transmission, the baseband processing unit 520 generates complex symbols by encoding and modulating a transmission bit stream, maps the complex symbols to subcarriers, and then , constructs OFDM symbols through inverse fast Fourier transform (IFFT) operation and cyclic prefix (CP) insertion. In addition, when receiving data, the baseband processor 520 divides the baseband signal provided from the RF processor 510 into OFDM symbol units, restores signals mapped to subcarriers through fast Fourier transform (FFT), and then , the received bit stream can be restored through demodulation and decoding.

The baseband processing unit 520 and the RF processing unit 510 transmit and receive signals as described above. The baseband processing unit 520 and the RF processing unit 510 may be referred to as a transmitter, a receiver, a transceiver, or a communication unit. Furthermore, at least one of the baseband processing unit 520 and the RF processing unit 510 may include a plurality of communication modules to support a plurality of different wireless access technologies. Also, at least one of the baseband processing unit 520 and the RF processing unit 510 may include different communication modules to process signals of different frequency bands. For example, different radio 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, 60 GHz) band. The terminal may transmit and receive signals with the base station using the baseband processing unit 520 and the RF processing unit 510, and the signal may include control information and data.

The storage unit 530 stores data such as basic programs for operation of the terminal, application programs, and setting information. In particular, the storage unit 530 may store information related to a second access node performing wireless communication using the second wireless access technology. And, the storage unit 530 provides the stored data according to the request of the control unit 540. The storage unit 530 may include a storage medium such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD, or a combination of storage media. Also, the storage unit 530 may be composed of a plurality of memories.

The controller 540 controls overall operations of the terminal. For example, the controller 540 transmits and receives signals through the baseband processor 520 and the RF processor 510 . Also, the control unit 540 writes and reads data in the storage unit 540 . To this end, the controller 540 may include at least one processor. For example, the control unit 540 may include a communication processor (CP) that controls communication and an application processor (AP) that controls upper layers such as application programs. Also, at least one component in the terminal may be implemented as one chip. According to an embodiment of the present disclosure, the control unit 540 may control each component of the terminal to transmit and receive control information in the IAB system. A method of operating a terminal according to an embodiment of the present disclosure will be described in more detail below.

6 illustrates a structure of a base station in a wireless communication system according to an embodiment of the present disclosure.

Referring to FIG. 6 , a base station may include an RF processing unit 610, a baseband processing unit 620, a backhaul communication unit 630, a storage unit 640, and a control unit 650. In addition, the control unit 650 may further include a multi-connection processing unit 652. Of course, it is not limited to the above example, and the base station may include fewer or more configurations than the configuration shown in FIG. 6 .

The RF processing unit 610 may perform functions for transmitting and receiving signals through a wireless channel, such as band conversion and amplification of signals. That is, the RF processor 610 upconverts the baseband signal provided from the baseband processor 620 into an RF band signal, transmits the signal through an antenna, and downconverts the RF band signal received through the antenna into a baseband signal. do. For example, the RF processor 610 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, and the like. In FIG. 6 , only one antenna is shown, but the RF processing unit 610 may include a plurality of antennas. Also, the RF processor 610 may include a plurality of RF chains. Also, the RF processor 610 may perform beamforming. For beamforming, the RF processing unit 610 may adjust the phase and size of signals transmitted and received through a plurality of antennas or antenna elements. The RF processor 610 may perform a downlink MIMO operation by transmitting one or more layers.

The baseband processing unit 620 may perform a conversion function between a baseband signal and a bit stream according to the physical layer standard of the first wireless access technology. For example, during data transmission, the baseband processing unit 620 may generate complex symbols by encoding and modulating a transmission bit stream. Also, when receiving data, the baseband processing unit 620 may demodulate and decode the baseband signal provided from the RF processing unit 610 to restore the received bit stream. For example, when data is transmitted according to the OFDM scheme, the baseband processing unit 620 generates complex symbols by encoding and modulating a transmission bit stream, maps the complex symbols to subcarriers, performs IFFT operation and CP insertion Configures OFDM symbols through. In addition, when receiving data, the baseband processing unit 620 divides the baseband signal provided from the RF processing unit 610 into OFDM symbol units, restores signals mapped to subcarriers through FFT operation, and demodulates and decodes the signals. The received bit string can be restored through The baseband processing unit 620 and the RF processing unit 610 may transmit and receive signals as described above. Accordingly, the baseband processing unit 620 and the RF processing unit 610 may be referred to as a transmission unit, a reception unit, a transmission/reception unit, a communication unit, or a wireless communication unit. The base station may transmit and receive signals with the terminal using the baseband processing unit 620 and the RF processing unit 610, and the signal may include control information and data.

The backhaul communication unit 630 provides an interface for communicating with other nodes in the network. That is, the backhaul communication unit 630 may convert a bit string transmitted from the main base station to another node, for example, a secondary base station, a core network, etc. into a physical signal, and convert a physical signal received from another node into a bit string. there is. The backhaul communication unit 630 may be included in the communication unit.

The storage unit 640 stores data such as basic programs for operation of the base station, application programs, and setting information. The storage unit 640 may store information about a bearer allocated to a connected terminal, measurement results reported from the connected terminal, and the like. In addition, the storage unit 640 may store information that is a criterion for determining whether to provide or stop multiple connections to the terminal. And, the storage unit 640 provides the stored data according to the request of the control unit 650. The storage unit 640 may include a storage medium such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD, or a combination of storage media. Also, the storage unit 640 may be composed of a plurality of memories. According to some embodiments, the storage unit 640 may store a program for performing the buffer status reporting method according to the present disclosure.

The controller 650 controls overall operations of the base station. For example, the control unit 650 transmits and receives signals through the baseband processing unit 620 and the RF processing unit 610 or through the backhaul communication unit 630 . Also, the control unit 650 writes and reads data in the storage unit 640 . To this end, the controller 650 may include at least one processor. Also, at least one configuration of the base station may be implemented with one chip.

According to an embodiment of the present disclosure, the controller 650 may control each configuration of the base station to transmit and receive control information in the IAB system according to an embodiment of the present disclosure. A method of operating a base station according to an embodiment of the present disclosure will be described in more detail below.

7 illustrates a migration process of an IAB node in a wireless communication system.

The embodiment of FIG. 7 shows legacy IAB node migration. The embodiment of FIG. 7 shows the IAB topology adaptation call flow of 3GPP TS 38.401.

The embodiment of FIG. 7 illustrates a case of intra donor migration. The following items explain the operation for each step.

In step 701, the IAB-MT performing the migration transmits a MeasurementReport message to the source parent node IAB-DU. The Measurement Report is based on the Measurement configuration previously received by the IAB-MT from the IAB-donor-CU. (migrating IAB-MT sends a MeasurementReport message to the source parent node IAB-DU. This report is based on a Measurement Configuration the migrating IAB-MT received from the IAB-donor-CU before.)

In step 702, the source parent node IA-DU transmits a UL RRC MESSAGE TRANSFER message to the IAB-donor-CU to forward the received MeasurementReport. (The source parent node IAB-DU sends an UL RRC MESSAGE TRANSFER message to the IAB-donor-CU to convey the received MeasurementReport.)

In step 703, the IAB-donor-CU creates a UE context for migration of the IAB-MT and transmits a UE CONTEXT SETUP REQUEST message to the target parent node IAB-DU to configure one or more bearers. (The IAB-donor-CU sends a UE CONTEXT SETUP REQUEST message to the target parent node IAB-DU to create the UE context for the migrating IAB-MT and set up one or more bearers. These bearers can be used by the migrating IAB -MT for its own signaling, and, optionally, data traffic.)

In step 704, the target parent node IAB-DU responds to the IAB-donor-CU with a UE CONTEXT SETUP RESPONSE message. (The target parent node IAB-DU responds to the IAB-donor-CU with a UE CONTEXT SETUP RESPONSE message.)

In step 705, the IAB-donor-CU transmits a UE CONTEXT MODIFICATION REQUEST message to the source parent node IAB-DU. The UE CONTEXT MODIFICATION REQUEST message includes the generated RRCReconfiguration message. The RRCReconfiguration message includes the basic BH RLC channel and basic BAP Routing ID configuration for UL F1-C/non-F1 traffic mapping of the target path. The RRCReconfiguration message may include an additional BH RLC channel. This step may also include assignment of routable TNL address(es) through the target IAB-donor-DU. The new TNL address(es) may be included in the RRCReconfiguration message as a replacement for the RNL address(es) routable through the source IAB-donor-DU. If an IPsec tunnel board is used to protect F1 and non-F1 traffic, the assigned TNL address is the external IP address. When using IAB-donor-DU with the same source path and target path, TNL address replacement is not required. The transmission action indicator of the UE CONTEXT MODIFICATION REQUEST message indicates to stop data transmission to the migrating IAB-node. (The IAB-donor-CU sends a UE CONTEXT MODIFICATION REQUEST message to the source parent node IAB-DU, which includes a generated RRCReconfiguration message. The RRCReconfiguration message includes a default BH RLC channel and a default BAP Routing ID configuration for UL F1- C/non-F1 traffic mapping on the target path.It may include additional BH RLC channels.This step may also include allocation of TNL address(es) that is (are) routable via the target IAB-donor-DU.The new TNL address(es) may be included in the RRCReconfiguration message as a replacement for the TNL address(es) that is (are) routable via the source IAB-donor-DU.In case IPsec tunnel mode is used to protect the F1 and non- F1 traffic, the allocated TNL address is outer IP address.The TNL address replacement is not necessary if the source and target paths use the same IAB-donor-DU.The Transmission Action Indicator in the UE CONTEXT MODIFICATION REQUEST message indicates to stop the data transmission to the migrating IAB -node.)

In step 706, the source parent node IAB-DU forwards the received RRCReconfiguration message to the migrating IAB-MT. (The source parent node IAB-DU forwards the received RRCReconfiguration message to the migrating IAB-MT.)

In step 707, the source parent node IAB-DU responds to the IAB-donor-CU with a UE CONTEXT MODIFICATION RESPONSE message. (The source parent node IAB-DU responds to the IAB-donor-CU with the UE CONTEXT MODIFICATION RESPONSE message.)

In step 708, a random access procedure is performed in the target parent node IAB-DU. (A Random Access procedure is performed at the target parent node IAB-DU.)

In step 709, the migrating IAB-MT responds to the target parent node IAB-DU with an RRCReconfigurationComplete message. (The migrating IAB-MT responds to the target parent node IAB-DU with an RRCReconfigurationComplete message.)

In step 710, the target parent node IAB-DU transmits a UL RRC MESSAGE TRANSFER message to the IAB-donor-CU to deliver the received RRCReconfigurationComplete message. In addition, an uplink packet can be transmitted to the migrating IAB-MT, which is delivered to the IAB-donor-CU through the target parent node IAB-DU. These UL packets belong to the IAB-MT's own signal and, optionally, data traffic. (The target parent node IAB-DU sends an UL RRC MESSAGE TRANSFER message to the IAB-donor-CU to convey the received RRCReconfigurationComplete message. Also, uplink packets can be sent from the migrating IAB-MT, which are forwarded to the IAB- donor-CU through the target parent node IAB-DU. These UL packets belong to the IAB-MT's own signaling and, optionally, data traffic.)

In step 711, the IAB-donor-CU performs BH RLC on the target path between the target parent IAB-node and the target IAB-donor-DU as well as DL mapping of the target IAB-donor-DU for migration to the target path of the IAB node. Configure channel and BAP-sublayer routing entries. This configuration may be performed immediately after an initial step, for example, step 703 . The IAB-donor-CU may configure an additional BH RLC channel for the migrating IAB-MT through an RRC message. (The IAB-donor-CU configures BH RLC channels and BAP-sublayer routing entries on the target path between the target parent IAB-node and target IAB-donor-DU as well as DL mappings on the target IAB-donor-DU for the migrating IAB-node's target path. These configurations may be performed at an earlier stage, e.g. immediately after step 3. The IAB-donor-CU may establish additional BH RLC channels to the migrating IAB-MT via RRC message.)

In step 712, the F1-C connection is switched to use the new TNL address of the migrating IAB-node, and the IAB-donor-CU updates UL BH information related to each GTP-tunnel to the migrating IAB-node. This step may also update the UL FTEID and DL FTEID associated with each GTP-tunnel. All F1-U tunnels are switched to use the migrating IAB node's new TNL address. This step may provide updated UP configuration for F1-U tunnels of multiple connected UEs or child IAB-MTs using UE-independent signaling on E1 and/or F1 interfaces. The IAB-donor-CU may also update UL BH information related to non-UP traffic. Implementations must avoid potential race conditions. That is, conflicting configurations should not be simultaneously performed using UE-related and non-UE-related procedures. (12. The F1-C connections are switched to use the migrating IAB-node's new TNL address(es), IAB-donor-CU updates the UL BH information associated to each GTP-tunnel to migrating IAB-node. This step may also update UL FTEID and DL FTEID associated to each GTP-tunnel. All F1-U tunnels are switched to use the migrating IAB-node's new TNL address(es). This step may use non-UE associated signaling in E1 and/or F1 interface to provide updated UP configuration for F1-U tunnels of multiple connected UEs or child IAB-MTs. The IAB-donor-CU may also update the UL BH information associated with non-UP traffic. Implementation must ensure the avoidance of potential race conditions, i.e. no conflicting configurations are concurrently performed using UE-associated and non-UE-associated procedures.)

In step 713, the IAB-donor-CU sends a UE CONTEXT RELEASE COMMAND message to the source parent node IAB-DU. (13. The IAB-donor-CU sends a UE CONTEXT RELEASE COMMAND message to the source parent node IAB-DU.)

In step 714, the source parent node IAB-DU releases the context of the migrating IAB-MT and responds to the IAB-donor-CU with a UE CONTEXT RELEASE COMPLETE message. (14. The source parent node IAB-DU releases the migrating IAB-MT's context and responds to the IAB-donor-CU with a UE CONTEXT RELEASE COMPLETE message.)

In step 715, the IAB-donor-CU releases the BH RLC channel and BAP-sublayer routing entries in the source path between the source parent IAB-node and the source IAB-donor-DU. (15. The IAB-donor-CU releases BH RLC channels and BAP-sublayer routing entries on the source path between source parent IAB-node and source IAB-donor-DU.)

8 illustrates a process of receiving and applying DU and BAP configuration information after accessing a target parent node when conditional handover is applied to IAB migration in a wireless communication system according to an embodiment of the present disclosure.

The embodiment of FIG. 8 applies RRC CHO. IAB-related information is not prefetched. That is, only genuine CHO procedures are applied.

In step 801, the migrating IAB-MT transmits a MeasurementReport message to the source parent node IAB-DU. The MeasurementReport message is based on the Measurement Configuration previously received by the migrating IAB-MT from the IAB-donor-CU. (One. migrating IAB-MT sends a MeasurementReport message to the source parent node IAB-DU. This report is based on a Measurement Configuration the migrating IAB-MT received from the IAB-donor-CU before.)

In step 802, the source parent node IAB-DU transmits a UL RRC MESSAGE TRANSFER message to iab-DONOR-cu to deliver the received MeasurementReport. (2. The source parent node IAB-DU sends an UL RRC MESSAGE TRANSFER message to the IAB-donor-CU to convey the received MeasurementReport.)

In step 802-1, the IAB donor CU may determine conditional handover based on the given measurementReport. In this process, the target parent IAB node operating the target cell can be determined.

In step 803, the AB-donor-CU transmits a UE CONTEXT SETUP REQUEST message to the target parent node IAB-DU to create a UE context for migrating IAB-MT and establish one or more bearers. These bearers can be used by the migrating IAB-MT for its own signaling and optionally data traffic. (3. The IAB-donor-CU sends a UE CONTEXT SETUP REQUEST message to the target parent node IAB-DU to create the UE context for the migrating IAB-MT and set up one or more bearers. These bearers can be used by the migrating IAB-MT for its own signaling, and, optionally, data traffic.)

In step 803-1, a conditional handover indicator may be included in the UE CONTEXT SETUP REQUEST message.

In step 804, the target parent node IAB-DU responds to the IAB-donor-CU with a UE CONTEXT SETUP RESPONSE message. (4. The target parent node IAB-DU responds to the IAB-donor-CU with a UE CONTEXT SETUP RESPONSE message.)

In step 805, the IAB-donor-CU transmits a UE CONTEXT MODIFICATION REQUEST message to the source parent node IAB-DU including the generated RRCReconfiguration message. When IPsec tunnel mode is used to protect F1 and non-F1 traffic, the assigned TNL address is the external IP address. When using IAB-donor-DU with the same source path and target path, TNL address replacement is not required. The Transmission Action Indicator of the UE CONTEXT MODIFICATION REQUEST message indicates to stop data transmission to the migrating IAB node. (5. The IAB-donor-CU sends a UE CONTEXT MODIFICATION REQUEST message to the source parent node IAB-DU, which includes a generated RRCReconfiguration message. In case IPsec tunnel mode is used to protect the F1 and non-F1 traffic, the allocated TNL address is outer IP address. The TNL address replacement is not necessary if the source and target paths use the same IAB-donor-DU. The Transmission Action Indicator in the UE CONTEXT MODIFICATION REQUEST message indicates to stop the data transmission to the migrating IAB-node.)

In step 805-1, additionally, the RRCReconfiguration message may include conditional information on performing conditional handover for the target cell on the target parent IAB node, and configuration information to be applied in the target cell. As the configuration information, the RRCReconfiguration message, which is an octet string, includes a basic BH RLC channel and basic BAP routing ID configuration for UL F1-C/non-F1 traffic mapping in a target route. Additional BH RLC channels may be included. This step may also include assignment of TNL address(es) routable through the target IAB-Donor-DU. The new TNL address(es) may be included in the RRCReconfiguration message as an octet string includes a default BH RLC channel and a default BAP Routing as a substitute for the TNL address(es) routable through the source IAB-donor-DU. ID configuration for UL F1-C/non-F1 traffic mapping on the target path.It may include additional BH RLC channels.This step may also include allocation of TNL address(es) that is (are) routable via the target IAB-donor -DU.The new TNL address(es) may be included in the RRCReconfiguration message as a replacement for the TNL address(es) that is (are) routable via the source IAB-donor-DU.)

In step 806, the source parent node IAB-DU transfers the received RRCReconfiguration message to the migrating IAB-MT. (6. The source parent node IAB-DU forwards the received RRCReconfiguration message to the migrating IAB-MT.)

RRCReconfiguration includes CondReconfig information. Configure the primary BH RLC channel and primary BAP routing ID for mapping UL F1-C/non-F1 traffic on the destination route (can be additional BH RLC channels) TNL address(s) routable through the destination IAB-donor-DU ) may be included in the RRCReconfiguration message. The new TNL address may be included in the RRCReconfiguration message instead of the TNL address. (es) Can be routed through the source IAB-donor-DU.

In step 806-1, the RRCReconfiguration message includes conditional handover conditions and setting information, and the setting information may be the RRCReconfiguration message in the form of an octet string mentioned in step 805-1. Upon receiving this information, the migrating IAB node stores the conditional handover condition and configuration information and starts condition evaluation.

In step 807, the source parent node IAB-DU responds to the IAB-donor-CU with a UE CONTEXT MODIFICATION RESPONSE message. (7. The source parent node IAB-DU responds to the IAB-donor-CU with the UE CONTEXT MODIFICATION RESPONSE message.)

In step 807-1, if a given condition is satisfied at any moment, the migrating IAB node applies the configuration and performs handover to the target parent IAB node corresponding to the condition.

In step 808, a random access procedure is performed in the target parent node IAB-DU. (8. A Random Access procedure is performed at the target parent node IAB-DU.)

In step 809, the migrating IAB-MT responds to the target parent node IAB-DU with an RRCReconfigurationComplete message. (9. The migrating IAB-MT responds to the target parent node IAB-DU with an RRCReconfigurationComplete message.)

In step 810, the target parent node IAB-DU transmits a UL RRC MESSAGE TRANSFER message to the IAB-donor-CU to deliver the received RRCReconfigurationComplete message. In addition, uplink packets can be transmitted in the migrating IAB-MT, which are delivered to the IAB-donor-CU through the target parent node IAB-DU. These UL packets are bound to the IAB-MT's own signals and optionally data traffic. (10. The target parent node IAB-DU sends an UL RRC MESSAGE TRANSFER message to the IAB-donor-CU to convey the received RRCReconfigurationComplete message. Also, uplink packets can be sent from the migrating IAB-MT, which are forwarded to the IAB-donor-CU through the target parent node IAB-DU. These UL packets belong to the IAB-MT's own signaling and, optionally, data traffic.)

In step 811, the IAB-donor-CU maps the DL of the target IAB-donor-DU to the target path of the migrating IAB node as well as the BH RLC channel and the target path between the target parent IAB-node and the target IAB-donor-DU. Configure BAP sublayer routing entries. This configuration may be performed at an initial stage, for example immediately after step 803. The IAB-donor-CU may establish an additional BH RLC channel for the migrating IAB-MT through an RRC message. (11. The IAB-donor-CU configures BH RLC channels and BAP-sublayer routing entries on the target path between the target parent IAB-node and target IAB-donor-DU as well as DL mappings on the target IAB-donor-DU for the migrating IAB-node's target path. These configurations may be performed at an earlier stage, e.g. immediately after step 3. The IAB-donor-CU may establish additional BH RLC channels to the migrating IAB-MT via RRC message.)

Depending on the embodiment, an update may be performed according to a target path immediately after step 811 of step 803 . And, when the MT finally accesses the target cell, it can transmit the setting to the migrating node through the UE context mode.

In step 812, the F1-C connection is switched to use the new TNL address of the migrating IAB-node, and the IAB-donor-CU updates UL BH information related to each GTP-tunnel to the migrating IAB-node. This step may also update the UL FTEID and DL FTEID associated with each GTP tunnel. All F1-U tunnels are switched to use the migrating IAB node's new TNL address. This step may provide updated UP configuration for F1-U tunnels of multiple connected UEs or child IAB-MTs using UE-independent signaling on E1 and/or F1 interfaces. The IAB-donor-CU may also update UL BH information related to non-UP traffic. Implementations must avoid potential race conditions. That is, conflicting configurations should not be simultaneously performed using UE-related and non-UE-related procedures. (12. The F1-C connections are switched to use the migrating IAB-node's new TNL address(es), IAB-donor-CU updates the UL BH information associated to each GTP-tunnel to migrating IAB-node. This step may also update UL FTEID and DL FTEID associated to each GTP-tunnel. All F1-U tunnels are switched to use the migrating IAB-node's new TNL address(es). This step may use non-UE associated signaling in E1 and/or F1 interface to provide updated UP configuration for F1-U tunnels of multiple connected UEs or child IAB-MTs. The IAB-donor-CU may also update the UL BH information associated with non-UP traffic. Implementation must ensure the avoidance of potential race conditions, i.e. no conflicting configurations are concurrently performed using UE-associated and non-UE-associated procedures.)

In step 813, the IAB-donor-CU sends a UE CONTEXT RELEASE COMMAND message to the source parent node IAB-DU. (13. The IAB-donor-CU sends a UE CONTEXT RELEASE COMMAND message to the source parent node IAB-DU.)

In step 814, the source parent node IAB-DU releases the context of the migrating IAB-MT and responds to the IAB-donor-CU with a UE CONTEXT RELEASE COMPLETE message. (14. The source parent node IAB-DU releases the migrating IAB-MT's context and responds to the IAB-donor-CU with a UE CONTEXT RELEASE COMPLETE message.)

In step 815, the IAB-donor-CU releases the BH RLC channel and BAP-sublayer routing entries in the source path between the source parent IAB-node and the source IAB-donor-DU. (15. The IAB-donor-CU releases BH RLC channels and BAP-sublayer routing entries on the source path between source parent IAB-node and source IAB-donor-DU.)

The above embodiment shows the case of intra donor migration. In the above operation when inter donor migration is considered, steps 803 and 804 occur between the target parent IAB node under the target donor CU and the target donor CU. Step 809 is transmitted from the migrating IAB node to the target parent IAB node under target donor Cu. Step 810 is transferred from the target parent IAB node under the target donor CU to the target donor CU. Steps 811 and 812 refer to the target parent IAB node below the target donor CU, application of settings on its path, and DU's F1 association.

9 illustrates a process of transferring DU and BAP configuration information through an RRC signal when conditional handover is applied to IAB migration in a wireless communication system according to an embodiment of the present disclosure.

The embodiment of FIG. 9 illustrates a process in which DU/BAP configuration is performed through RRC signaling.

In step 901, the migrating IAB-MT transmits a MeasurementReport message to the source parent node IAB-DU. The MeasurementRport is based on the Measurement Configuration previously received by the migrating IAB-MT from the IAB-donor-CU. (One. migrating IAB-MT sends a MeasurementReport message to the source parent node IAB-DU. This report is based on a Measurement Configuration the migrating IAB-MT received from the IAB-donor-CU before.)

In step 902, the source parent node IAB-DU transmits a UL RRC MESSAGE TRANSFER message to the IAB-donor-CU to forward the received MeasurementReport. (2. The source parent node IAB-DU sends an UL RRC MESSAGE TRANSFER message to the IAB-donor-CU to convey the received MeasurementReport.)

In step 902-1, the IAB donor CU may determine conditional handover based on the given measurementReport. In this process, the target parent IAB node operating the target cell can be determined.

In step 903, the IAB-donor-CU creates a UE context for migrating IAB-MT and transmits a UE CONTEXT SETUP REQUEST message to the target parent node IAB-DU to configure one or more bearers. These bearers can be used for their own signaling in the migrating IAB-MT and optionally for data traffic. (3. The IAB-donor-CU sends a UE CONTEXT SETUP REQUEST message to the target parent node IAB-DU to create the UE context for the migrating IAB-MT and set up one or more bearers. These bearers can be used by the migrating IAB-MT for its own signaling, and, optionally, data traffic.)

In step 903-1, a conditional handover indicator may be included in the UE CONTEXT SETUP REQUEST message.

In step 904, the target parent node IAB-DU responds to the IAB-donor-CU with a UE CONTEXT SETUP RESPONSE message. (4. The target parent node IAB-DU responds to the IAB-donor-CU with a UE CONTEXT SETUP RESPONSE message.)

In step 905, the IAB-donor-CU transmits a UE CONTEXT MODIFICATION REQUEST message to the source parent node IAB-DU including the generated RRCReconfiguration message. When IPsec tunnel mode is used to secure F1 and non-F1 traffic, the assigned TNL address is the external IP address. If the IAB-donor-DU with the same source path and target path is used, TNL address replacement is not required. The Transmission Action Indicator of the UE CONTEXT MODIFICATION REQUEST message indicates to stop data transmission to the migrating IAB node. (5. The IAB-donor-CU sends a UE CONTEXT MODIFICATION REQUEST message to the source parent node IAB-DU, which includes a generated RRCReconfiguration message. In case IPsec tunnel mode is used to protect the F1 and non-F1 traffic, the allocated TNL address is outer IP address. The TNL address replacement is not necessary if the source and target paths use the same IAB-donor-DU. The Transmission Action Indicator in the UE CONTEXT MODIFICATION REQUEST message indicates to stop the data transmission to the migrating IAB-node.)

In step 905-1, additionally, the RRCReconfiguration message may include condition information for performing conditional handover for a target cell on the target parent IAB node, and configuration information to be applied in the target cell. As the configuration information, the RRCReconfiguration message, which is an octet string, includes a basic BH RLC channel and basic BAP routing ID configuration for UL F1-C/non-F1 traffic mapping in a target route. Additional BH RLC channels may be included. This step may also include assignment of routable TNL address(es) through the target IAB-donor-DU. The new TNL address(es) may be included in the RRCReconfiguration message as a replacement for the routable TNL address(es) through the source IAB-donor-DU. (RRCReconfiguration message as an octet string includes a default BH RLC channel and a default BAP Routing ID configuration for UL F1-C/non-F1 traffic mapping on the target path. It may include additional BH RLC channels. This step may also include allocation of TNL address(es) that is (are) routable via the target IAB-donor-DU. The new TNL address(es) may be included in the RRCReconfiguration message as a replacement for the TNL address(es) that is (are) routable via the source IAB-donor-DU.)

In step 905-2, the RRCReconfiguration message mentioned in step 905-1 above may include, in addition to the condition information and configuration information, information necessary for configuring DUs and BAPs after accessing the associated target cell. This information is information created by an IAB donor CU (in case of intra donor CU migration) or a target IAB donor CU (in case of inter donor CU migration), and can be signaled in conjunction with a conditional setup id or target cell id.

For example, you can have the following hierarchy.

RRCReconfiguration

ConditionalReconfiguration IE

condReconfigId

Condition

RRCReconfig

DU/BAP config (F1AP message format below in octet string, associated with condReconfig Id)

That is, these configuration information can be expressed as an octet string as an F1AP message, and can be associated with a configuration id of conditional handover given in RRC or a target cell identifier. Information included in this setting may be DU setting, BAP config information, and IAB UP setting information.

The BAP configuration information can be BH RLC channels and BAP sublayer routing entries (BH RLC channels and BAP-sublayer routing entries on the target path) of the target path, and the information included in the BAP Mapping Configuration message on the F1-AP signal It can be.

The IAB UP configuration information can be parameters including UL mapping configuration and the UL/DL UP TNL information, and is included in the IAB UP Configuration Update message on the F1-AP signal. Information may be included.

DU configuration information may be information included in the gNB-DU Resource Configuration message on the F1-AP.

The above information includes the parent node after receiving a positive response from the target parent IAB node after step 4 in the IAB donor CU (in case of intra-donor migration) or target IAB donor CU (in case of inter-donor migration). When the CU-CP (F1-AP) determines the above contents in consideration of the topology and resource usage situation, configures the message on the F1-AP, and delivers it to the RRC on the CU, the RRC on the CU relates to the conditional handover in RRCReconfiguration in step 905. It can be included in configuration information.

In step 906, the source parent node IAB-DU transfers the received RRCReconfiguration message to the migrating IAB-MT. (6. The source parent node IAB-DU forwards the received RRCReconfiguration message to the migrating IAB-MT.)

RRCReconfiguration includes CondReconfig information. Configure the primary BH RLC channel and primary BAP routing ID for mapping UL F1-C/non-F1 traffic on the destination route (can be additional BH RLC channels) TNL address(s) routable through the destination IAB-donor-DU ) may be included in the RRCReconfiguration message. The new TNL address may be included in the RRCReconfiguration message instead of the TNL address. (es) Can be routed through the source IAB-donor-DU. And DU constitutes preconfiguration of RRC information (i.e., genuine CHO) and DU-specific information (BH RLC channel, BAP path, and mapping rules in the migrating IAB node). This is not for all configuration updates along the target path.

RRCReconfiguration has F1AP msg field. The Migrating IAB node delivers the F1AP configuration information message related to the target cell to the DU when the CHO condition is satisfied or when handover is completed to the corresponding cell.

In step 906-1, the RRCReconfiguration message includes conditional handover condition and setting information. The configuration information may be an RRCReconfiguration message in the form of an octet string mentioned in step 905-1. Upon receiving this information, the migrating IAB node stores the conditional handover condition and configuration information and starts condition evaluation.

In step 907, the source parent node IAB-DU responds to the IAB-donor-CU with a UE CONTEXT MODIFICATION RESPONSE message. (7. The source parent node IAB-DU responds to the IAB-donor-CU with the UE CONTEXT MODIFICATION RESPONSE message.)

In step 907-1, if a given condition is satisfied at any moment, the migrating IAB node applies the configuration and performs handover to the target parent IAB node corresponding to the condition.

In step 907-2, if the DU/BAP setting information associated with the target cell to which the MT of the migrating IAB node is handing over has already been received in step 907-1, the MT part of the DU/BAP setting information is the DU of the IAB node. parts can be passed on. As a specific point in time, it may be when the condition for the target cell to be handed over is satisfied, when the handover is performed because the condition is satisfied, or when the handover is performed and RRCReconfigurationComplete is transmitted.

The DU of the migrating IAB node receiving this information can apply the received configuration information.

In step 908, a random access procedure is performed in the target parent node IAB-DU. (8. A Random Access procedure is performed at the target parent node IAB-DU.)

In step 909, the migrating IAB-MT responds to the target parent node IAB-DU with an RRCReconfigurationComplete message. (9. The migrating IAB-MT responds to the target parent node IAB-DU with an RRCReconfigurationComplete message.)

In step 910, the target parent node IAB-DU transmits a UL RRC MESSAGE TRANSFER message to the IAB-donor-CU to deliver the received RRCReconfigurationComplete message. Also, uplink packets can be transmitted from the migrating IAB-MT, which are delivered to the IAB-donor-CU through the target parent node IAB-DU. 10. These UL packets belong to IAB-MT's own signal and optionally data traffic. The target parent node IAB-DU sends an UL RRC MESSAGE TRANSFER message to the IAB-donor-CU to convey the received RRCReconfigurationComplete message. Also, uplink packets can be sent from the migrating IAB-MT, which are forwarded to the IAB-donor-CU through the target parent node IAB-DU. These UL packets belong to the IAB-MT's own signaling and, optionally, data traffic.

In step 911, the IAB-donor-CU maps the DL of the target IAB-donor-DU to the target IAB-donor-DU as well as the BH RLC channel and the target path between the target parent IAB-node and the target IAB-donor-DU. Configure BAP-sublayer routing entries. Destination path of the migrating IAB node. This configuration may be performed immediately after an initial step, for example, step 903 . The IAB-donor-CU may establish an additional BH RLC channel for the migrating IAB-MT through an RRC message. (11. The IAB-donor-CU configures BH RLC channels and BAP-sublayer routing entries on the target path between the target parent IAB-node and target IAB-donor-DU as well as DL mappings on the target IAB-donor-DU for the migrating IAB-node's target path. These configurations may be performed at an earlier stage, e.g. immediately after step 3. The IAB-donor-CU may establish additional BH RLC channels to the migrating IAB-MT via RRC message.

Depending on the embodiment, an update may be performed according to a target path immediately after step 911 of step 903 . And, when the MT finally accesses the target cell, it can transmit the setting to the migrating node through the UE context mode. However, in the case of CHO, it is impossible to perform an update according to the target path immediately after step 903. This is because the actual migration has not yet been performed, and we do not know when it will be performed. Therefore, it is possible to give the setting of step 911 to the migrating node itself in advance, but it is difficult to perform the update along the target path in advance.

In step 912, the F1-C connection is switched to use the new TNL address of the migrating IAB-node and the IAB-donor-CU updates the UL BH information related to each GTP-tunnel to the migrating IAB-node. This step may also update the UL FTEID and DL FTEID associated with each GTP tunnel. All F1-U tunnels are switched to use the migrating IAB node's new TNL address. This step may use non-UE related signaling on E1 and/or F1 interfaces to provide updated UP configuration for F1-U tunnels of multiple connected UEs or chid IAB-MTs. The IAB-donor-CU may also update UL BH information related to non-UP traffic. Implementations must avoid potential race conditions. That is, conflicting configurations should not be simultaneously performed using UE-related and non-UE-related procedures. (12. The F1-C connections are switched to use the migrating IAB-node's new TNL address(es), IAB-donor-CU updates the UL BH information associated to each GTP-tunnel to migrating IAB-node. This step may also update UL FTEID and DL FTEID associated to each GTP-tunnel. All F1-U tunnels are switched to use the migrating IAB-node's new TNL address(es). This step may use non-UE associated signaling in E1 and/or F1 interface to provide updated UP configuration for F1-U tunnels of multiple connected UEs or child IAB-MTs. The IAB-donor-CU may also update the UL BH information associated with non-UP traffic. Implementation must ensure the avoidance of potential race conditions, i.e. no conflicting configurations are concurrently performed using UE-associated and non-UE-associated procedures.)

In step 913, the IAB-donor-CU transmits a UE CONTEXT RELEASE COMMAND message to the source parent node IAB-DU. (13. The IAB-donor-CU sends a UE CONTEXT RELEASE COMMAND message to the source parent node IAB-DU.)

In step 914, the source parent node IAB-DU releases the context of the migrating IAB-MT and responds to the IAB-donor-CU with a UE CONTEXT RELEASE COMPLETE message. (14. The source parent node IAB-DU releases the migrating IAB-MT's context and responds to the IAB-donor-CU with a UE CONTEXT RELEASE COMPLETE message.)

In step 915, the IAB-donor-CU releases the BH RLC channel and BAP-sublayer routing entries in the source path between the source parent IAB-node and the source IAB-donor-DU. (15. The IAB-donor-CU releases BH RLC channels and BAP-sublayer routing entries on the source path between source parent IAB-node and source IAB-donor-DU.)

10 illustrates a process of transferring DU and BAP configuration information through an F1AP signal when conditional handover is applied to IAB migration in a wireless communication system according to an embodiment of the present disclosure.

In the embodiment of FIG. 10, DU/BAP configuration is performed through F1AP together with reference to CHO configuration.

In step 1001, the migrating IAB-MT transmits a MeasurementReport message to the source parent node IAB-DU. The MeasurementRport is based on the Measurement Configuration previously received by the migrating IAB-MT from the IAB-donor-CU. (One. migrating IAB-MT sends a MeasurementReport message to the source parent node IAB-DU. This report is based on a Measurement Configuration the migrating IAB-MT received from the IAB-donor-CU before.)

In step 1002, the source parent node IAB-DU transmits the UL RRC MESSAGE TRANSFER message to the IAB-donor-CU to deliver the received MeasurementReport. (2. The source parent node IAB-DU sends an UL RRC MESSAGE TRANSFER message to the IAB-donor-CU to convey the received MeasurementReport.)

In step 1002-1, the IAB donor CU may determine conditional handover based on the given measurementReport. In this process, the target parent IAB node operating the target cell can be determined.

In step 1003, the IAB-donor-CU creates a UE context for migrating IAB-MT and transmits a UE CONTEXT SETUP REQUEST message to the target parent node IAB-DU to configure one or more bearers. These bearers can be used for their own signaling in the migrating IAB-MT and optionally for data traffic. (3. The IAB-donor-CU sends a UE CONTEXT SETUP REQUEST message to the target parent node IAB-DU to create the UE context for the migrating IAB-MT and set up one or more bearers. These bearers can be used by the migrating IAB-MT for its own signaling, and, optionally, data traffic.)

In step 1003-1, a conditional handover indicator may be included in the UE CONTEXT SETUP REQUEST message.

In step 1004, the target parent node IAB-DU responds to the IAB-donor-CU with a UE CONTEXT SETUP RESPONSE message. (4. The target parent node IAB-DU responds to the IAB-donor-CU with a UE CONTEXT SETUP RESPONSE message.)

In step 1005, the IAB-donor-CU transmits a UE CONTEXT MODIFICATION REQUEST message to the source parent node IAB-DU including the generated RRCReconfiguration message. When IPsec tunnel mode is used to secure F1 and non-F1 traffic, the assigned TNL address is the external IP address. If the IAB-donor-DU with the same source path and target path is used, TNL address replacement is not required. The Transmission Action Indicator of the UE CONTEXT MODIFICATION REQUEST message indicates to stop data transmission to the migrating IAB node. (5. The IAB-donor-CU sends a UE CONTEXT MODIFICATION REQUEST message to the source parent node IAB-DU, which includes a generated RRCReconfiguration message. In case IPsec tunnel mode is used to protect the F1 and non-F1 traffic, the allocated TNL address is outer IP address. The TNL address replacement is not necessary if the source and target paths use the same IAB-donor-DU. The Transmission Action Indicator in the UE CONTEXT MODIFICATION REQUEST message indicates to stop the data transmission to the migrating IAB-node.)

In step 1005-1, additionally, the RRCReconfiguration message may include conditional information on performing conditional handover for a target cell on the target parent IAB node, and configuration information to be applied in the target cell. As the configuration information, the RRCReconfiguration message, which is an octet string, includes a basic BH RLC channel and basic BAP routing ID configuration for UL F1-C/non-F1 traffic mapping in a target route. Additional BH RLC channels may be included. This step may also include assignment of routable TNL address(es) through the target IAB-donor-DU. The new TNL address(es) may be included in the RRCReconfiguration message as a replacement for the routable TNL address(es) through the source IAB-donor-DU. (RRCReconfiguration message as an octet string includes a default BH RLC channel and a default BAP Routing ID configuration for UL F1-C/non-F1 traffic mapping on the target path. It may include additional BH RLC channels. This step may also include allocation of TNL address(es) that is (are) routable via the target IAB-donor-DU. The new TNL address(es) may be included in the RRCReconfiguration message as a replacement for the TNL address(es) that is (are) routable via the source IAB-donor-DU.)

In step 1005-2, the IAB donor CU (in case of intra-donor migration) or the target IAB donor CU (in case of inter-donor migration) creates the RRCReconfiguration message mentioned in step 1005-1 and transmits it in step 1005. , After accessing the conditional handover target cell using the topology information of the target parent IAb node, information necessary for DU and BAP configuration can be delivered to the migrating IAB node through a separate F1-AP message. This information may include BAP/DU configuration information and conditional configuration id or target cell id information of a given conditional handover on the current RRC associated therewith. The DU of the Migrating IAB node can store the BAP/DU setting information by dividing it by target cell or by conditional handover setting id.

Information included in this BAP/DU setting may be DU setting, BAP config information, and IAB UP setting information.

The BAP configuration information may be BH RLC channels and BAP-sublayer routing entries on the target path information, or information included in a BAP Mapping Configuration message on an F1-AP signal.

The IAB UP configuration information may be parameters including UL mapping configuration and the UL/DL UP TNL information, and may be information included in an IAB UP Configuration Update message on the F1-AP signal.

DU configuration information may be information included in the gNB-DU Resource Configuration message on the F1-AP.

The donor CU must synchronize conditional handover configuration information on RRC with DU/BAP configuration information for the corresponding target cell. That is, when a specific conditional handover configuration is added/modified/removed through an RRC message, related DU/BAP configuration information can be equally added/modified/removed through an F1-AP message.

In step 1006, the source parent node IAB-DU transfers the received RRCReconfiguration message to the migrating IAB-MT. (6. The source parent node IAB-DU forwards the received RRCReconfiguration message to the migrating IAB-MT.)

RRCReconfiguration includes CondReconfig information. Configure the primary BH RLC channel and primary BAP routing ID for mapping UL F1-C/non-F1 traffic on the destination route (can be additional BH RLC channels) TNL address(s) routable through the destination IAB-donor-DU ) may be included in the RRCReconfiguration message. The new TNL address may be included in the RRCReconfiguration message instead of the TNL address. (es) Can be routed through the source IAB-donor-DU. And DU constitutes preconfiguration of RRC information (i.e., genuine CHO) and DU-specific information (BH RLC channel, BAP path, and mapping rules in the migrating IAB node). This is not for all configuration updates along the target path.

After CHO configuration, F1AP configuration information for the corresponding candidate target cell is delivered as an F1AP message. The migrating IAB node delivers the condReconfigID related to the original cell to the DU when the CHO condition is satisfied or when the HO is completed with the corresponding cell.

In step 1006-1, the RRCReconfiguration message includes conditional handover conditions and setting information, and the setting information may be the RRCReconfiguration message in the form of an octet string mentioned in step 1005-1. Upon receiving this information, the migrating IAB node stores the conditional handover condition and configuration information and starts condition evaluation.

In step 1007, the source parent IAB-DU responds to the IAB-donor-CU with a UE CONTEXT MODIFICATION RESPONSE message. (7. The source parent node IAB-DU responds to the IAB-donor-CU with the UE CONTEXT MODIFICATION RESPONSE message.)

In step 1007-1, if a given condition is satisfied at any moment, the migrating IAB node applies the configuration and performs handover to the target parent IAB node corresponding to the condition.

In step 1007-2, the migrating IAB MT may transmit conditional configuration id or target cell id information to perform conditional handover to the migrating IAB DU. As a specific point in time, it may be when the condition for the target cell to be handed over is satisfied, when the handover is performed because the condition is satisfied, or when the handover is performed and RRCReconfigurationComplete is transmitted. The DU of the migrating IAB node receiving this information can apply DU/BAP configuration information matching the received conditional configuration ID or target cell ID.

In step 1008, a random access procedure is performed in the target parent node IAB-DU. (8. A Random Access procedure is performed at the target parent node IAB-DU.)

In step 1009, the migrating IAB-MT responds to the target parent node IAB-DU with an RRCReconfigurationComplete message. (9. The migrating IAB-MT responds to the target parent node IAB-DU with an RRCReconfigurationComplete message.)

In step 1010, the target parent node IAB-DU transmits a UL RRC MESSAGE TRANSFER message to IAB-donor-CU in order to deliver the received RRCReconfigurationComplete message. In addition, uplink packets can be transmitted from the migrating IAB-MT, which are delivered to the IAB-donor-CU through the target parent node IAB-DU. These UL packets belong to the IAB-MT's own signal and optionally to data traffic. (10. The target parent node IAB-DU sends an UL RRC MESSAGE TRANSFER message to the IAB-donor-CU to convey the received RRCReconfigurationComplete message. Also, uplink packets can be sent from the migrating IAB-MT, which are forwarded to the IAB-donor-CU through the target parent node IAB-DU. These UL packets belong to the IAB-MT's own signaling and, optionally, data traffic.)

In step 1011, the IAB-donor-CU not only maps the DL of the target IAB-donor-DU to the target of the migrating IAB node, but also maps the BH RLC channel and BAP to the target path between the target parent IAB-node and the target IAB-donor-DU. Configure sublayer routing entries. This configuration may be performed immediately after an initial step, for example, step 1003 . The IAB-donor-CU may establish an additional BH RLC channel for the migrating IAB-MT through an RRC message. (11. The IAB-donor-CU configures BH RLC channels and BAP-sublayer routing entries on the target path between the target parent IAB-node and target IAB-donor-DU as well as DL mappings on the target IAB-donor-DU for the migrating IAB-node's target path. These configurations may be performed at an earlier stage, e.g. immediately after step 3. The IAB-donor-CU may establish additional BH RLC channels to the migrating IAB-MT via RRC message.)

Depending on the embodiment, step 1011 may be updated immediately after step 1003 according to the target path. And, when the MT finally accesses the target cell, it can transmit the setting to the migrating node through the UE context mode. However, in the case of CHO, it is impossible to perform update according to the target path immediately after step 1003. This is because the actual migration has not yet been performed, and we do not know when it will be performed. Therefore, it is possible to give the migrating node itself the settings in step 1011 in advance, but it is difficult to perform an update along the target path in advance. In step 1012, the F1-C connection is switched to use the new TNL address of the migrating IAB-node. IAB-donor-CU updates UL BH information related to each GTP-tunnel to the migrating IAB-node. This step may also update the UL FTEID and DL FTEID associated with each GTP tunnel. All F1-U tunnels are switched to use the migrating IAB node's new TNL address. This step may provide updated UP configuration for F1-U tunnels of multiple connected UEs or child IAB-MTs using UE-independent signaling on E1 and/or F1 interfaces. The IAB-donor-CU may also update UL BH information related to non-UP traffic. Implementations must avoid potential race conditions. That is, conflicting configurations using UE-related and non-UE-related procedures must be prevented from being performed at the same time. (12. The F1-C connections are switched to use the migrating IAB-node's new TNL address(es), IAB-donor-CU updates the UL BH information associated to each GTP-tunnel to migrating IAB-node. This step may also update UL FTEID and DL FTEID associated to each GTP-tunnel. All F1-U tunnels are switched to use the migrating IAB-node's new TNL address(es). This step may use non-UE associated signaling in E1 and/or F1 interface to provide updated UP configuration for F1-U tunnels of multiple connected UEs or child IAB-MTs. The IAB-donor-CU may also update the UL BH information associated with non-UP traffic. Implementation must ensure the avoidance of potential race conditions, i.e. no conflicting configurations are concurrently performed using UE-associated and non-UE-associated procedures.)

In step 1013, the IAB-donor-CU transmits a UE CONTEXT RELEASE COMMAND message to the source parent node IAB-DU. (13. The IAB-donor-CU sends a UE CONTEXT RELEASE COMMAND message to the source parent node IAB-DU.)

In step 1014, the source parent node IAB-DU releases the context of the migrating IAB-MT and responds to the IAB-donor-CU with a UE CONTEXT RELEASE COMPLETE message. (14. The source parent node IAB-DU releases the migrating IAB-MT's context and responds to the IAB-donor-CU with a UE CONTEXT RELEASE COMPLETE message.)

In step 1015, the IAB-donor-CU releases the BH RLC channel and BAP-sublayer routing entries in the source path between the source parent IAB-node and the source IAB-donor-DU. (15. The IAB-donor-CU releases BH RLC channels and BAP-sublayer routing entries on the source path between source parent IAB-node and source IAB-donor-DU.)

In another embodiment, the BAP/DU configuration information may be given even in a normal handover operation regardless of the conditional handover of the migrating IAB MT. In this case, since one target cell rather than multiple target cells is determined, in the above-described embodiment of FIG. 9 or 10, the RRC signal (the embodiment of FIG. 9) or the F1-AP signal (FIG. Example of), BAP/DU configuration information may be transmitted in advance. In this case, association with the conditional setting id or target cell id is not required.

In detail, in the embodiment of FIG. 9, if BAP/DU configuration information included in RRCReconfiguration is given to the migrating IAB MT, if the IAB MT performs a handover or transmits RRCReconfigurationComplete, the corresponding BAP/DU configuration information is sent to the DU can be forwarded to In this case, the DU may apply the received configuration information.

In the case of the embodiment of FIG. 10, the Bap/DU configuration information given to the F1-AP can be given to the DU without association with a separate conditional configuration id or target cell id, and when the migrating IAB MT performs handover or transmits RRCReconfigurationComplete In this case, the DU can be notified through a separate indicator, and in this case, the DU can apply the corresponding setting.

An example of another case is when a child node is connected to the migrating IAB node. In this case, the application of the RRCReconfiguration message including BAP/DU is not considered simply. It can be divided into a case of transmitting DU/BAP configuration information and the RRCRecongiruation message including it to the IAB node MT to be directly applied using an RRC signal, and a case of transmitting to the parent node of the IAB node to be directly applied using F1-AP. . In the case of direct application using RRC, RRCReconfiguration can be applied when a separate indicator is received from the parent node. On the other hand, when F1-AP is used, the child node can apply the received RRCReconfiguration at the time when the parent node transfers the RRCReconfiguration message to the child node.

11 illustrates a process of transmitting RRCReconfiguration using an RRC signal in a wireless communication system according to an embodiment of the present disclosure.

In the case of signaling using an RRC signal, after the donor CU determines migration and obtains configuration information from the target cell (after step 904 in the embodiment of FIG. 9 or after step 1004 in the embodiment of FIG. 10) , transfers BAP/DU configuration information to child nodes of the migrating IAB node using RRC messages first. After transferring the above configuration to all descendant IAB nodes (ie, IAB nodes of all children/grand children, etc. under the migrating IAB node), the donor CU can transmit a handover command, that is, RRCReconfiguration, to the migrating IAB node. According to this message, the migrating IAB node may perform handover and transmit an RRCReconfigurationComplete message to the target parent node.

When the migrating IAB node applies the received RRCReconfiguration, when the migrating IAB node performs handover, when the migrating IAB node performs synchronous and random access operation, when the migrating IAB node sends an RRCReconfigurationComplete message, or when the migrating IAB node performs handover When the over is successfully completed, the migrating IAB node sends a separate indicator to the child nodes of the migrating IAB node. The child IAB node receiving this indicator applies the BAP/DU configuration included in the RRCReconfiguration while applying the previously received RRCReconfiguration. And as a response, the RRCReconfigurationComplete message is delivered to the parent node of the child node, that is, the node that delivered the indication. The indicator may be a BAP control PDU, or may be a MAC CE or physical layer DCI.

From the point of view of the IAB node, if BAP/DU configuration information exists in the received RRCReconfiguration message or if there is an indicator indicating a separate delayed RRCReconfiguration, RRCReconfiguration is not applied immediately upon receipt, but the indication is received from the parent node. In this case, the received RRCReconfiguration setting can be applied and also the BAP/DU setting included inside can be applied. It performs application of RRCReconfiguration setting, and if it has its own child node, it can send the same indication to the child node. If the migrating IAB node performs conditional handover, the BAP/DU configuration and RRCReconfiguration including it received by all descendant IAB nodes from the donor node are linked to the conditional handover configuration id or target cell id, and the above indicator may include conditional configuration id or target cell id. Upon receiving the indicator including the conditional configuration id or target cell id, the IAB node applies configuration information associated with the conditional configuration id or target cell id among RRCReconfiguration and BAP/DU configuration information stored therein.

12 illustrates a process of transmitting RRCReconfiguration using an F1-AP in a wireless communication system according to an embodiment of the present disclosure.

In the case of signaling using the F1-AP, after the donor CU determines migration and obtains configuration information from the target cell (after step 904 in the embodiment of FIG. 9 or after step 1004 in the embodiment of FIG. 10 ) ), the RRCReconfiguration message including the BAP/DU configuration information is delivered to the parent node of the child node of the migrating IAB node using the F1-AP message first. This message is stored in the DU part of the received IAB node. After the parent IAB node of all descendant IAB nodes (ie, IAB nodes of all child/grand children, etc. under the migrating IAB node) receives the message, the donor CU can transfer a handover command, that is, RRCReconfiguration, to the migrating iab node. there is. According to this message, the migrating IAB node may perform handover and transmit an RRCReconfigurationComplete message to the target parent node.

When the migrating IAB node applies the received RRCReconfiguration, when the migrating IAB node performs handover, when the migrating IAB node performs synchronous and random access operation, when the migrating IAB node transmits an RRCReconfigurationComplete message, or when the migrating IAB node performs handover When the over is successfully completed, the migrating IAB node forwards the RRCReconfiguration message it received and saved in the DU part to the child node of the migrating IAB node. The child IAB node receiving this message applies the BAP/DU configuration included in the RRCReconfiguration while applying the previously received RRCReconfiguration. And as a response to this, it delivers the RRCReconfigurationComplete message to its parent node, that is, the node that delivered the RRCReconfiguration.

From the point of view of the IAB node, if the F1-AP message includes an indicator to delay delivery of the RRCReconfiguration message included therein, the DU of the IAB node transmits RRCReconfiguratoin to its child node immediately upon receiving the F1-AP message Instead, you can save it, receive RRCReconfiguration from your parent IAB node, and transmit RRCReconfiguration to your child node at the time of applying it. If the migrating IAB node performs conditional handover, the BAP/DU configuration and RRCReconfiguration including it received by the parent node of all descendant IAB nodes are linked to the conditional handover id or target cell id, and the migrating IAB When a node performs conditional handover, conditional configuration id or target cell id information of the target to be performed can be delivered to each child node through RRCReconfiguration. Based on this information, the IAB node receiving this message can send an RRCREconfiguration message that also includes conditional configuration id or target cell id information to its child node.

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 for execution by one or more processors in an electronic 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.

Such programs (software modules, software) may include random access memory, non-volatile memory including flash memory, read only memory (ROM), and electrically erasable programmable ROM. (electrically erasable programmable read only memory (EEPROM), magnetic disc storage device, compact disc-ROM (CD-ROM), digital versatile discs (DVDs), or other It can be stored on optical storage devices, magnetic cassettes. Alternatively, it may be stored in a memory composed of a combination of some or all of these. In addition, each configuration memory may be included in multiple numbers.

In addition, the program is provided through a communication network such as the Internet, an intranet, a local area network (LAN), a wide area network (WAN), or a storage area network (SAN), or a communication network consisting of a combination thereof. It can be stored on an attachable storage device that can be accessed. Such a storage device may be connected to a device performing an embodiment of the present disclosure through an external port. In addition, a separate storage device on a communication network may be connected to a device performing an embodiment of the present disclosure.

In the specific embodiments of the present disclosure described above, components included in the disclosure are expressed in singular or plural numbers according to the specific embodiments presented. However, the singular or plural expressions are selected appropriately for the presented situation for convenience of explanation, and the present disclosure is not limited to singular or plural components, and even components expressed in plural are composed of the singular number or singular. Even the expressed components may be composed of a plurality.

Meanwhile, in the detailed description of the present disclosure, specific embodiments have been described, but various modifications are possible without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the described embodiments and should not be defined by the scope of the claims described below as well as those equivalent to the scope of these claims.

Claims (2)

In the method of operating a network node in a wireless communication system,
Receiving conditional handover configuration information or receiving DU configuration information prior to performing handover;
Including the process of applying DU configuration information when performing conditional handover,
method.
In the device of a network node in a wireless communication system,
transceiver; and
includes at least one processor;
The at least one processor,
Receiving conditional handover configuration information or receiving DU configuration information prior to performing handover;
Configured to apply DU configuration information when performing conditional handover,
Device.

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