KR20210120767A - Apparatus and method for failure recovery of master cell group in intergrated access and backhaul system - Google Patents

Abstract

The present invention relates to a communication technique that combines a 5G communication system with an IoT technology to support higher data rates after a 4G system and a system thereof. The present invention can be applied to intelligent services (eg, smart home, smart building, smart city, smart car or connected car, healthcare, digital education, retail business, security and safety related services, etc.) based on a 5G communication technology and an IoT-related technology. The present invention provides a method for operating forward information necessary for reconnection to a network of a terminal part in a radio access backhaul combination system.

Description

Apparatus and method for failure recovery of a master cell group in an access backhaul combined system {APPARATUS AND METHOD FOR FAILURE RECOVERY OF MASTER CELL GROUP IN INTERGRATED ACCESS AND BACKHAUL SYSTEM}

The present invention provides a method of operating forward information necessary for reconnection to a network of a terminal part in a radio access backhaul combination system.

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

On the other hand, the Internet is evolving from a human-centered connection network where humans create and consume information to an Internet of Things (IoT) network that exchanges and processes information between distributed components such as objects. Internet of Everything (IoE) technology, which combines big data processing technology through connection with cloud servers, etc. with IoT technology, is also emerging. In order to implement IoT, technology elements such as sensing technology, wired and wireless communication and network infrastructure, service interface technology, and security technology are required. , M2M), and MTC (Machine Type Communication) are being studied. In the IoT environment, an intelligent IT (Internet Technology) service that collects and analyzes data generated from connected objects and creates new values in human life can be provided. IoT is a field of smart home, smart building, smart city, smart car or connected car, smart grid, health care, smart home appliance, advanced medical service, etc. can be applied to

Accordingly, various attempts are being made to apply the 5G communication system to the IoT network. For example, in technologies such as sensor network, machine to machine (M2M), and MTC (Machine Type Communication), 5G communication technology is implemented by techniques such as beam forming, MIMO, and array antenna. there will be The application of a cloud radio access network (cloud RAN) as the big data processing technology described above is an example of the convergence of 5G technology and IoT technology.

IAB (integrated access and backhaul) is a type of relay node in which one node operates as a mobile terminal (MT or terminal or User Equipment; UE) to an upper IAB node, and serves as a base station to a lower IAB node. Concept. For example, the node collects the uplink traffic from the lower IAB node and the uplink traffic of a general terminal accessing itself, and delivers it to the upper IAB node as uplink traffic, and then re-transmits the downlink traffic from the core network. It can serve as downlink traffic to its own subordinate IAB node, or to a general terminal accessing itself as downlink traffic. IAB refers to a system of a topology consisting of a node and the node in which access and backhaul communication operations are combined by one node performing the operation of communicating with the upper IAB node and the operation of communicating with the lower IAB node and the terminal in the above process. can do. A node directly connected to the core network is defined as an IAB donor, and the IAB donor does not have an upper IAB node and can be connected to the core network using an IP address system.

In the present invention, in a wireless communication system consisting of multiple hops of IAB nodes, when a node in the middle occurs a recognizable failure in the RRC layer including a radio connection failure, the donor base station notifies the fact of the failure, and a subsequent command from the network accordingly By receiving, we propose a method of reconnecting to a network more efficiently.

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

According to an embodiment of the present invention, in a system consisting of multiple hops of IAB nodes, when a middle node fails recognizable in the RRC layer, including radio connection failure, it notifies the donor base station of the failure, and from the resulting network By receiving a later command of , it is possible to reconnect to the network more efficiently.

In addition, according to an embodiment of the present invention, if radio connection failure occurs or after RRC release or re-establishment is performed, if information on cells connected to the existing IAB donor is provided, the terminal will return to the network later. When accessing, reconnection is performed to the cell connected to the possible existing IAB donor, and there is no additional overhead of the terminal and the base station due to PDCP lossless transmission and security refresh, so that the network is reconnected more efficiently can do.

1 is a diagram illustrating the structure of an existing LTE system.
2 is a diagram illustrating a radio protocol structure of an existing LTE system.
3 is a diagram illustrating a structure of a next-generation mobile communication system to which the present invention can be applied.
4 is a diagram illustrating a radio protocol structure of a next-generation mobile communication system to which the present invention can be applied.
5 is a diagram illustrating a terminal device according to embodiments of the present invention.
6 is a diagram illustrating a base station apparatus according to embodiments of the present invention.
7 is a diagram illustrating a case of MCG failure through RLF detection in an SA situation.
8 is a diagram illustrating a case of MCG failure through RLF notification in an SA situation.
9 is a diagram illustrating a case of SCG failure through RLF detection in an SA situation.
10 is a diagram illustrating a case of SCG failure through RLF notification in an SA situation.
11 is a diagram illustrating a case of SCG failure through RLF detection in an NSA situation.
12A is a diagram illustrating a case of SCG failure through RLF notification in an NSA situation.
12B is a diagram illustrating a case in which RLF recovery failure notification due to SCG release is transmitted.
13A is a flowchart illustrating a cell selection operation for a mobile terminal (MT) to access an IAB node included in the same donor gNB during connection re-establishment.
13B is a diagram illustrating a case in which an MT receives an indicator related to a current donor gNB/CU in an RRC message when an IAB network is combined.
FIG. 13c is a diagram illustrating a case in which the MT receives information on cell IDs accessible under the current donor gNB/CU in an RRC message when combining the IAB network.
14 is a flowchart illustrating a cell selection operation for the MT not to access its lower IAB node during connection re-establishment.

In describing embodiments in the present specification, descriptions of technical contents that are well known in the technical field to which the present invention pertains and are not directly related to the present invention will be omitted. This is to more clearly convey the gist of the present invention without obscuring the gist of the present invention by omitting unnecessary description.

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

Advantages and features of the present invention, and a method for achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

At this time, it will be understood that each block of the flowchart diagrams and combinations of the flowchart diagrams may 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, such that the instructions performed by the processor of the computer or other programmable data processing equipment are not described in the flowchart block(s). It creates a means to perform functions. These computer program instructions may also be stored in a computer-usable or computer-readable memory that may direct a computer or other programmable data processing equipment to implement a function in a particular manner, and thus the computer-usable or computer-readable memory. It is also possible that the instructions stored in the flow chart block(s) produce an article of manufacture containing instruction means for performing the function described in the flowchart block(s). The computer program instructions may also be mounted on a computer or other programmable data processing equipment, such that a series of operational steps are performed on the computer or other programmable data processing equipment to create a computer-executed process to create a computer or other programmable data processing equipment. It is also possible that instructions for performing the processing equipment 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 also possible for the functions recited in blocks to occur out of order. For example, two blocks shown one after another may in fact be performed substantially simultaneously, or it is possible that the blocks are sometimes performed in the reverse order according to the corresponding function.

At this time, the term '~ unit' used in this embodiment means software or hardware components such as FPGA or ASIC, and '~ unit' performs certain roles. However, '-part' is not limited to software or hardware. The '~ unit' may be configured to reside on an addressable storage medium or may be configured to refresh one or more processors. Thus, as an example, '~' denotes components such as software components, object-oriented software components, class components, and task components, and processes, functions, properties, and procedures. , subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functions provided in the components and '~ units' may be combined into a smaller number 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 secure multimedia card.

Hereinafter, the operating principle of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related well-known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, the terms described below are terms defined in consideration of functions in the present invention, which may vary according to intentions or customs of users and operators. Therefore, the definition should be made based on the content throughout this specification.

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

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

According to an embodiment of the present invention, when communication between the core network and terminals is made in a topology consisting of multiple hops of the IAB node, the access point of the core network may be the IAB donor node. This donor node includes a centralized unit (CU) and controls the control of the distributed unit (DU) and the operation related to data transmission/reception to the terminal through the DU. In the case of a terminal part (mobile terminal; MT or terminal or User Equipment; UE) of an intermediate IAB node or a terminal receiving service from an IAB node, when a connection fails, the reason for a problem in the MCG or SCG link is reported to the network. At this time, not only the reason for detecting the existing radio link failure (RLF), but also information indicating that the parent IAB node is disconnected from the network. have. Through this, the network knows that the parent IAB node of the IAB node that reported the failure also has a problem, and can instruct the movement (mobility) to an IAB node other than the corresponding parent IAB node when selecting a cell. In addition, in the cell selection process of the IAB node after failure, a white list that allows only IAB nodes under the same donor gNB to be reselected, and a black list of cell selection for the purpose of preventing selection of its own descendant IAB node (black list) can be introduced.

1 is a diagram illustrating the structure of an existing LTE system.

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

In FIG. 1 , ENBs 1-05 to 1-20 may correspond to the existing Node Bs of the UMTS system. The ENB may be connected to the UEs 1-35 through a radio channel and may perform a more complex role than the existing Node B. In the LTE system, all user traffic including real-time services such as Voice over IP (VoIP) through the Internet protocol may be serviced through a shared channel. Accordingly, there is a need for an apparatus for scheduling by collecting status information such as buffer status, available transmission power status, and channel status of UEs, and the ENBs 1-05 to 1-20 can be in charge of this. One ENB can usually control multiple cells. For example, in order to implement a transmission rate of 100 Mbps, the LTE system may use, for example, Orthogonal Frequency Division Multiplexing (OFDM) as a radio access technology in a 20 MHz bandwidth. In addition, an Adaptive Modulation & Coding (AMC) method for determining a modulation scheme and a channel coding rate according to the channel state of the terminal may be applied. The S-GW 1-30 is a device that provides a data bearer, and may create or remove a data bearer according to the control of the MME 1-25. The MME is a device in charge of various control functions as well as a mobility management function for the UE, and can be connected to a plurality of base stations.

2 is a diagram illustrating a radio protocol structure of an existing LTE system.

2, the radio protocol of the LTE system is packet data convergence protocol (PDCP) (2-05, 2-40), radio link control (RLC) ( 2-10, 2-35) and Medium Access Control (MAC) (2-15, 2-30). The PDCP may be in charge of operations such as IP header compression/restore. The main functions of PDCP can be summarized as follows.

- Header compression and decompression (ROHC only)

- Transfer of user data

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

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

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

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

- Encryption and decryption function (Ciphering and deciphering)

- Timer-based SDU discard in uplink.

The radio link control (RLC) 2-10, 2-35 may reconfigure a PDCP packet data unit (PDU) to an appropriate size to perform an ARQ operation or the like. The main functions of RLC can be summarized as follows.

- Data transfer function (Transfer of upper layer PDUs)

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

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

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

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

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

- 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 function (RLC re-establishment)

The MACs 2-15 and 2-30 may be connected to several RLC layer devices configured in one terminal, and may perform operations of multiplexing RLC PDUs into MAC PDUs and demultiplexing RLC PDUs from MAC PDUs. The main functions of MAC can be summarized as follows.

- Mapping function (Mapping between logical channels and transport channels)

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

- Scheduling information reporting function (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

The physical layer (2-20, 2-25) channel-codes and modulates upper layer data, creates OFDM symbols and transmits them over a radio channel, or demodulates and channel-decodes OFDM symbols received through the radio channel and transmits them to higher layers action can be made.

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

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

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

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

Referring to FIG. 4, radio protocols of the next-generation mobile communication system are NR Service Data Adaptation Protocol (SDAP) (4-01, 4-45), NR PDCP (4-05, 4-40), NR RLC (4-10, 4-35), and NR MAC (4-15, 4-30).

The main functions of the NR SDAPs 4-01 and 4-45 may include some of the following functions.

- transfer of user plane data

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

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

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

The main function of the NR PDCP (4-05, 4-40) may include some of the following functions.

- Header compression and decompression (ROHC only)

- Transfer of user data

- In-sequence delivery of upper layer PDUs

- Out-of-sequence delivery of upper layer PDUs

- Order reordering function (PDCP PDU reordering for reception)

- Duplicate detection of lower layer SDUs

- Retransmission of PDCP SDUs

- Encryption and decryption function (Ciphering and deciphering)

- Timer-based SDU discard in uplink.

In the above description, the reordering function of the NR PDCP device may refer to a function of reordering PDCP PDUs received from a lower layer in order based on a PDCP sequence number (SN). The reordering function of the NR PDCP device may include a function of delivering data to a higher layer in the rearranged order, or may include a function of directly passing data without considering the order, and may be lost by reordering It may include a function of recording the PDCP PDUs that have been lost, may include a function of reporting a status on the lost PDCP PDUs to the transmitting side, and may include a function of requesting retransmission of the lost PDCP PDUs. have.

The main function of the NR RLC (4-10, 4-35) may include some of the following functions.

- Data transfer function (Transfer of upper layer PDUs)

- In-sequence delivery of upper layer PDUs

- Out-of-sequence delivery of upper layer PDUs

- ARQ function (Error Correction through ARQ)

- Concatenation, segmentation and reassembly of RLC SDUs

- Re-segmentation of RLC data PDUs

- Reordering of RLC data PDUs

- Duplicate detection

- Protocol error detection

- RLC SDU discard function (RLC SDU discard)

- RLC re-establishment function (RLC re-establishment)

In the above description, in-sequence delivery of the NR RLC device may refer to a function of sequentially delivering RLC SDUs received from a lower layer to a higher layer. When one RLC SDU is originally divided into several RLC SDUs and received, the in-sequence delivery function of the NR RLC device may include a function of reassembling it and delivering it.

In-sequence delivery of the NR RLC device may include a function of rearranging the received RLC PDUs based on an RLC sequence number (SN) or a PDCP sequence number (SN), and may be lost by rearranging the order It may include a function of recording the lost RLC PDUs, a function of reporting a status on the lost RLC PDUs to the transmitting side, and a function of requesting retransmission of the lost RLC PDUs. have.

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

The in-sequence delivery function of the NR RLC device may include a function of sequentially delivering all RLC SDUs received before the timer starts to a higher layer if a predetermined timer expires even if there are lost RLC SDUs. have.

In-sequence delivery of the NR RLC device may include a function of sequentially delivering all received RLC SDUs to a higher layer if a predetermined timer expires even if there are lost RLC SDUs.

The NR RLC device may process RLC PDUs in the order in which they are received and deliver them to the NR PDCP device regardless of the sequence number (Out-of sequence delivery).

When the NR RLC device receives a segment, it may receive segments stored in the buffer or to be received later, reconstruct it into one complete RLC PDU, and then deliver 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 function of the NR RLC device may refer to a function of directly delivering RLC SDUs received from a lower layer to a higher layer regardless of an order. The out-of-sequence delivery function of the NR RLC device may include a function of reassembling and delivering when one RLC SDU is originally divided into several RLC SDUs and received. Out-of-sequence delivery of the NR RLC device may include a function of storing the RLC SN or PDCP SN of the received RLC PDUs, sorting the order, and recording the lost RLC PDUs.

The NR MACs 4-15 and 4-30 may be connected to several NR RLC layer devices configured in one terminal, and the main function of the NR MAC may include some of the following functions.

- Mapping function (Mapping between logical channels and transport channels)

- Multiplexing/demultiplexing of MAC SDUs

- Scheduling information reporting function (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

The NR PHY layer (4-20, 4-25) channel-codes and modulates the upper layer data, makes an OFDM symbol and transmits it to the radio channel, or demodulates and channel-decodes the OFDM symbol received through the radio channel to the upper layer. You can perform a forwarding action.

5 is a diagram illustrating a terminal device according to embodiments of the present invention.

Referring to the drawings, the terminal may include a radio frequency (RF) processing unit 5-10, a baseband processing unit 5-20, a storage unit 5-30, and a control unit 5-40. can

The RF processing unit 5-10 may perform a function for transmitting and receiving a signal through a wireless channel, such as band conversion and amplification of the signal. For example, the RF processor 5-10 up-converts the baseband signal provided from the baseband processor 5-20 into an RF band signal, transmits it through an antenna, and receives the RF signal through the antenna. A band signal can be down-converted to a baseband signal. For example, the RF processing unit 5-10 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), etc. can In the figure, only one antenna is shown, but the terminal may include a plurality of antennas. In addition, the RF processing unit 5-10 may include a plurality of RF chains. Furthermore, the RF processing unit 5-10 may perform beamforming. For the beamforming, the RF processing unit 5-10 may adjust the phase and magnitude of each of the signals transmitted and received through a plurality of antennas or antenna elements. In addition, the RF processing unit may perform MIMO, and may receive multiple layers when performing MIMO operation.

The baseband processing unit 5-20 may perform a function of converting between a baseband signal and a bit stream according to a physical layer standard of a system. For example, when transmitting data, the baseband processing unit 5-20 may generate complex symbols by encoding and modulating a transmitted bit stream. Also, when receiving data, the baseband processing unit 5-20 may restore a received bit stream by demodulating and decoding the baseband signal provided from the RF processing unit 5-10. For example, when transmitting data according to an orthogonal frequency division multiplexing (OFDM) scheme, the baseband processing unit 5-20 encodes and modulates a transmission bit stream to generate complex symbols, and convert the complex symbols to subcarriers. After mapping to , OFDM symbols can be configured through inverse fast Fourier transform (IFFT) operation and cyclic prefix (CP) insertion. In addition, upon data reception, the baseband processing unit 5-20 divides the baseband signal provided from the RF processing unit 5-10 into OFDM symbol units, and maps them to subcarriers through fast Fourier transform (FFT). After restoring the received signals, the received bit stream can be restored through demodulation and decoding.

The baseband processing unit 5-20 and the RF processing unit 5-10 may transmit and receive signals as described above. Accordingly, the baseband processing unit 5-20 and the RF processing unit 5-10 may be referred to as a transmitter, a receiver, a transceiver, or a communication unit. Furthermore, at least one of the baseband processing unit 5-20 and the RF processing unit 5-10 may include a plurality of communication modules to support a plurality of different wireless access technologies. In addition, at least one of the baseband processing unit 5-20 and the RF processing unit 5-10 may include different communication modules to process signals of different frequency bands. For example, the different wireless access technologies may include a wireless LAN (eg, IEEE 802.11), a cellular network (eg, LTE), and the like. In addition, the different frequency bands may include a super high frequency (SHF) (eg, 2.NRHz, NRhz) band and a millimeter wave (eg, 60GHz) band.

The storage unit 5-30 may store data such as a basic program, an application program, and setting information for the operation of the terminal. In particular, the storage unit 5-30 may store information related to a second access node that performs wireless communication using a second wireless access technology. In addition, the storage unit 5-30 may provide stored data according to the request of the control unit 5-40.

The controller 5-40 may control overall operations of the terminal. For example, the control unit 5-40 may transmit and receive signals through the baseband processing unit 5-20 and the RF processing unit 5-10. In addition, the control unit 5-40 can write and read data in the storage unit 5-40. To this end, the control unit 5-40 may include at least one processor. For example, the controller 5-40 may include a communication processor (CP) that controls for communication and an application processor (AP) that controls an upper layer such as an application program.

6 is a diagram illustrating a base station apparatus according to embodiments of the present invention.

As shown in the figure, the base station includes an RF processing unit 6-10, a baseband processing unit 6-20, a backhaul communication unit 6-30, a storage unit 6-40, and a control unit 6-50. It may be composed of

The RF processing unit 6-10 may perform a function for transmitting and receiving a signal through a wireless channel, such as band conversion and amplification of the signal. For example, the RF processor 6-10 up-converts the baseband signal provided from the baseband processor 6-20 into an RF band signal, transmits it through an antenna, and receives the RF signal through the antenna. A band signal can be down-converted to a baseband signal. For example, the RF processing unit 6-10 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, and the like. Although only one antenna is shown in the drawing, the first access node may include a plurality of antennas. In addition, the RF processing unit 6-10 may include a plurality of RF chains. Furthermore, the RF processing unit 6-10 may perform beamforming. For the beamforming, the RF processing unit 6-10 may adjust the phase and magnitude of each of the signals transmitted and received through a plurality of antennas or antenna elements. The RF processing unit may perform a downlink MIMO operation by transmitting one or more layers.

The baseband processing unit 6-20 may perform a function of converting between a baseband signal and a bit stream according to the physical layer standard of the first radio access technology. For example, when transmitting data, the baseband processing unit 6-20 may generate complex symbols by encoding and modulating a transmitted bit stream. Also, when receiving data, the baseband processing unit 6-20 may restore a received bit stream by demodulating and decoding the baseband signal provided from the RF processing unit 6-10. For example, in the OFDM scheme, when transmitting data, the baseband processing unit 6-20 generates complex symbols by encoding and modulating a transmitted bit stream, maps the complex symbols to subcarriers, and then IFFT OFDM symbols can be configured through operation and CP insertion. Also, upon data reception, the baseband processing unit 6-20 divides the baseband signal provided from the RF processing unit 6-10 into OFDM symbol units, and restores signals mapped to subcarriers through FFT operation. After that, the received bit stream can be restored through demodulation and decoding. The baseband processing unit 6-20 and the RF processing unit 6-10 may transmit and receive signals as described above. Accordingly, the baseband processing unit 6-20 and the RF processing unit 6-10 may be referred to as a transmitter, a receiver, a transceiver, a communication unit, or a wireless communication unit.

The backhaul communication unit 6-30 may provide an interface for performing communication with other nodes in the network. For example, the backhaul communication unit 6-30 converts a bit string transmitted from the main base station to another node, for example, an auxiliary base station, a core network, etc. into a physical signal, and a physical signal received from the other node. can be converted to a bit string.

The storage unit 6-40 may store data such as a basic program, an application program, and setting information for the operation of the main station. In particular, the storage unit 6-40 may store information on a bearer assigned to an accessed terminal, a measurement result reported from the accessed terminal, and the like. In addition, the storage unit 6-40 may store information serving as a criterion for determining whether to provide or stop multiple connections to the terminal. In addition, the storage unit 6-40 may provide stored data according to the request of the control unit 6-50.

The controller 6-50 may control overall operations of the main station. For example, the control unit 6-50 may transmit/receive a signal through the baseband processing unit 6-20 and the RF processing unit 6-10 or through the backhaul communication unit 6-30. In addition, the control unit 6-50 can write and read data in the storage unit 6-40. To this end, the control unit 6-50 may include at least one processor.

7 is a diagram illustrating a case of master cell group failure (MCG failure) through RLF detection in a stand-alone (SA) situation.

In FIG. 7, it can be assumed that IAB nodes 1 and 2 are connected to the CU of the donor node through an arbitrary relay link.

Node 3 is an IAB node, and may have node 1 as a parent node of an MCG link and node 2 as a parent node of a Secondary Cell Group (SCG) link. When the mobile terminal (MT) of Node 3 detects the RLF of the MCG link, the operation of processing the RLF is shown. At this time, when the MCG link becomes RLF, the MT indicates that the T310 timer expires or the RLC layer indicates that maximum retransmission is performed, and the MAC indicates a random access problem. It may include at least one of the cases. When the MT detects the RLF in the MCG link, the MT of the IAB node 3 may perform at least one of the following operations.

- Stop the transmission on the master cell group (Master Cell Group, MCG). In this case, the target may be any Signaling Radio Bearer (SRB), Data Radio Bearer (DRB), and a backhaul RLC channel/egress backhaul RLC channel.

- Reset the MCG MAC. If there is an RLC SDU or PDU that has failed to be transmitted, it can be transmitted again to the SCG RLC stack without MAC reset.

- Update the routing entry of the IAB node. In this case, a specific operation may be performed by removing a routing entry having a failed MCG link as an egress link in the Backhaul Adaptation Protocol (BAP) entity, and replacing it with an SCG link when SCG is configured.

- The MCGFailureInformation message can be transmitted to the donor CU through the parent node through SRB 3 or split SRB1. In this case, as a cause value, it may be set to one of T310 timer expiration, RLC maximum retransmission arrival, and random access channel (RACH) problem occurrence. In addition, the corresponding message may include a measurement result value of a serving cell and a measurement result of a neighboring cell existing at a frequency corresponding to the measurement object set in the MCG. In addition, the measurement result of the serving cells existing in the frequency corresponding to the measurement object set in the SCG and the measurement result of the neighboring cell may be included. It can also include routing information used by the BAP layer at the time of failure. In this case, the routing information may include an egress link and a next hop ID mapped to each routing ID, and may also include BH RLC channel mapping information used at this time.

- When transmitting the message, if PDCP duplication is configured, the MT transmits the message through split SRB1 without changing the primary path. If not, change the primary path. If the MT transmits the message to SRB3, it may be transmitted directly to SRB3 without encapsulating the ULInformationTransfer-MRDC message and delivering it. In this regard, the MN (master node) may deliver the RRCReconfiguration or RRCrelease message to the received SRB. Similarly, when received through SRB3, the RRC message can be directly transmitted without separately using a message that encapsulates the MRDC message, such as DLInformationTransfer-MRDC. Upon receiving this message, the MT applies the corresponding RRC message.

- In another embodiment, after the MT delivers the message to the network, in addition to the RRC message (eg, RRCReconfiguration / RRCrelease) to be applied to the MT by the network, the message delivered to the MT part of the parent node corresponding to the failed MCG link. may include. This message may also be an RRC reconfiguration or RRC release message. The MT receives this message, for example, an RRC message to be applied to the MT and a set of RRC messages to be applied to the parent node on the MCG side from the network, and then before applying the RRC message needed for it, the parent node corresponding to the MCG link. You can separate the message to be applied to and deliver it first. In this case, the control packet of the BAP layer may be used or an Uplink Dedicated Control Channel (UL-DCCH) may be used. After delivering this message, the MT may apply the RRC message to be applied to it. After the MCG parent node receives the message it needs from the MT of the child node, the MT of the node can apply it.

- Send the above message and start the timer. If the MT does not receive the RRC message until the timer expires, the MT may perform RRC re-establishment.

According to an embodiment, the IAB node 3 700 may perform RLF detection of the IAB node 1 710 ( S700 ). IAB node 3 (700) may perform the MCGFaliureInformation Procedure (S705). The MCGFaliureInformation Procedure may include at least one of the following operations.

- TX suspension on MCG (egress BH RLC channel, SRB, DRB)

- Reset MCG MAC

- Routing entry update

- Transmission of MCGFaliureInformation (cause: legacy RLF)

- Start T316 if configured and not running before

The IAB node 3 700 may transmit the MCGFaliureInformation message to the IAB node 2 720 through split SRB1 or SRB3 (no encapsulation) (S710). The IAB node 2 720 may transmit the MCGFaliureInformation message to the donor CU 730 as BH traffic (S715). The donor CU 730 may perform Identify node 1 cannot be reached from node 3 (S720). The donor CU 730 may transmit an RRC message corresponding to the MCGFaliureInformation as BH traffic to the IAB node 2 720 (S725). IAB node 2 720 may transmit RRCReconfiguration/RRCRelease on split SRB1 or SRB3 (no encapsulation) to IAB node 3 700 (S730).

The RRCReconfiguration message transmitted in step S730 may include information for recovery when the IAB connection fails. For example, the RRCReconfiguration message may include an IP address to be used after reconnection in the DU part of the corresponding IAB node. In addition, the RRCRelease message may include a PCI (physical cell ID) included in the IAB node to be used for cell measurement and cell selection in IDLE mode. When the IAB node 3 (700) receives the IP address in the RRCReconfiguration message, the received IAB node 3 (700) converts the IP address to the IP layer destination address of the DU without an additional IP address request operation after connection. Can be used. Through this, the IAB node 3 700 can exchange the control signal and user plane signal of F1 in the IP layer with the CU and DU of the donor node. When the IAB node 3 (700) receives the PCI to be used for cell selection in the RRCRelease message, the received IAB node 3 (700) selects only the corresponding cell when selecting the cell in IDLE mode. condition can be considered.

8 is a diagram illustrating a case of MCG failure through RLF notification (notification) in an SA situation.

In FIG. 8, it can be assumed that IAB nodes 1 and 2 are connected to the CU of the donor node through an arbitrary relay link.

Node 3 is an IAB node, and has node 1 as the parent node of the MCG link and node 2 as the parent node of the SCG link. Node 3 has node 5 as a child node and can serve an MCG link. Node 4 may serve the SCG link of Node 5. When the mobile terminal (MT) of the node 3 detects the RLF of the MCG link, the node 3 may perform an RRC connection re-establishment operation. When this re-establishment fails, node 3 may deliver an RLF recovery failure notification to a child node. The MT of the child node that has received this notification may consider that RLF has occurred in the received link. In FIG. 8, since node 3 is an MN in node 5, which is a child node, the MT of node 5 considers that RLF has occurred in the MCG link.

For example, when an IAB node receives an RLF recovery failure notification from its parent node, it may consider that RLF has occurred in the corresponding link. Accordingly, when a notification is received from the MCG, an MCG failure information operation can be performed, and when a notification is received from the SCG, an SCG failure information operation can be performed. MCG failure information may perform at least one of the following operations.

- Stop the transmission on the MCG. In this case, the target may be all SRBs, DRBs, and backhaul RLC channels/egress backhaul RLC channels.

- Reset the MCG MAC. If there is an RLC SDU or PDU that has failed to be transmitted, it can be transmitted again to the SCG RLC stack without MAC reset.

- Update the routing entry of the IAB node. In this case, as a specific operation, a routing entry having a failed MCG link as an egress link in the BAP entity may be removed, and if SCG is configured, it may be replaced with an SCG link.

- The MCGFailureInformation message can be transmitted to the parent node of the SCG side through SRB 3 or split SRB1. In this case, the cause value may be set to a value indicating a state in which the parent node that has transmitted the notification, for example, the MN has lost its connection to the parent node or the network. Unlike the general RLF report, the corresponding message may not include the measurement result value of the serving cell and the measurement result of the neighboring cell existing in the frequency corresponding to the measurement object set in the MCG. In addition, the measurement result of the serving cells existing in the frequency corresponding to the measurement object set in the SCG and the measurement result of the neighboring cell may not be included. It may include routing information used in the BAP layer at the time of failure. In this case, the routing information may include an egress link and a next hop ID mapped to each routing ID, and may also include BH RLC channel mapping information used at this time.

- When transmitting the message, if PDCP duplication is configured, the MT does not change the primary path and transmits it through split SRB1. If not, change the primary path. If the MT transmits the message to SRB3, it may directly transmit the message to SRB3 without encapsulating it in the ULInformationTransfer-MRDC message. In this regard, the MN (master node) may deliver the RRCReconfiguration or RRCrelease message to the received SRB. Similarly, when received through SRB3, the RRC message can be directly transmitted without separately using a message that encapsulates the MRDC message, such as DLInformationTransfer-MRDC. Upon receiving this message, the MT applies the corresponding RRC message.

- In another embodiment, after the MT delivers the message to the network, in addition to the RRC message (eg, RRCReconfiguration / RRCrelease) to be applied to the MT by the network, the message delivered to the MT part of the parent node corresponding to the failed MCG link. may include. This message may also be an RRC reconfiguration or RRC release message. The MT receives this message, for example, an RRC message to be applied to the MT and a set of RRC messages to be applied to the parent node on the MCG side from the network, and then before applying the RRC message needed for it, the parent node corresponding to the MCG link. You can separate the message to be applied to and deliver it first. In this case, the control packet of the BAP layer may be used or the UL-DCCH may be used. After delivering this message, the MT may apply the RRC message to be applied to it. After the MCG parent node receives the message it needs from the MT of the child node, the MT of the node can apply it.

- Send the above message and start the timer. If the MT does not receive the RRC message until the timer expires, the MT may perform RRC re-establishment.

According to an embodiment, when the IAB node 3 810 fails RRC re-establishment, the IAB node 5 800 may receive an RLF recovery failure indication from the IAB node 3 810 (S800). IAB node 5 (800) may perform the MCGFaliureInformation Procedure (S805). The MCGFaliureInformation Procedure may include at least one of the following operations.

- TX suspension on MCG (egress BH RLC channel, SRB, DRB)

- Reset MCG MAC

- Routing entry update

- Transmission of MCGFaliureInformation (cause: failure_on_parent)

- Start T316 if configured and not running before

When the RRC re-establishment fails, the IAB node 3 810 may shut down in the case of DU after transmitting an RLF recovery failure indication, and may be switched to the IDLE mode in case of MT (S810). The shut down may mean stopping all signal transmission and stopping UL/DL transmission and reception. The IAB node 5 800 may transmit the MCGFaliureInformation message to the IAB node 4 820 through split SRB1 or SRB3 (no encapsulation) (S815). The IAB node 4 820 may transmit BH traffic including the MCGFaliureInformation message to the donor CU 830 (S820). The donor CU 830 may perform Identify node 1, 2 cannot be reached from node 3, and node 3 has no connection with CU (S825). The donor CU 830 may transmit BH traffic to the IAB node 4 820 (S830). The IAB node 4 820 may transmit an RRCReconfiguration/RRCRelease message to the IAB node 5 800 through split SRB1 or SRB3 (no encapsulation) (S835).

The RRCReconfiguration message transmitted in step S835 may include information for recovery when the IAB connection fails. For example, the RRCReconfiguration message may include an IP address to be used after reconnection in the DU part of the corresponding IAB node. In addition, the RRCRelease message may include a PCI (physical cell ID) included in the IAB node to be used for cell measurement and cell selection in IDLE mode. When the IAB node 5 (800) receives the IP address in the RRCReconfiguration message, the received IAB node 5 (800) converts the IP address to the IP layer destination address of the DU without an additional IP address request operation after resuming the connection. can be used as Through this, the IAB node 5 800 may exchange the control signal and user plane signal of F1 in the IP layer with the CU and DU of the donor node. When the IAB node 5 (800) receives the PCI to be used for cell selection in the RRCRelease message, the received IAB node 5 (800) selects only the corresponding cell when selecting the cell in IDLE mode. condition can be considered.

9 is a diagram illustrating a case of SCG failure through RLF detection in an SA situation.

In FIG. 9, it can be assumed that IAB nodes 1 and 2 are connected to the CU of the donor node through an arbitrary relay link.

Node 3 is an IAB node, and has node 1 as the parent node of the MCG link and node 2 as the parent node of the SCG link. Node 3 has node 5 as a child node and can serve an MCG link. Node 4 may serve the SCG link of Node 5. When the mobile terminal (MT) of the node 3 detects the RLF of the SCG link, the node 3 may perform the SCG failure information operation. The SCG failure information may perform at least one of the following operations.

- Stop the transmission on the SCG. In this case, the target may be all SRBs, DRBs, and backhaul RLC channels/egress backhaul RLC channels.

- Reset the SCG MAC. If there is an RLC SDU or PDU that has failed transmission, it can be transmitted again to the MCG RLC stack without MAC reset.

- Update the routing entry of the IAB node. In this case, as a specific operation, a routing entry having a failed SCG link as an egress link in the BAP entity may be removed and replaced with an MCG link.

- The SCGFailureInformation message can be transmitted to the donor CU through the parent node through SRB 1. In this case, the cause value may be a cause value of a general RLF such as expiration of the t310 timer, reaching the maximum RLC retransmission, or occurrence of a RACH problem. The corresponding message includes the measurement result value of the serving cell and the measurement result of the neighboring cell existing in the frequency corresponding to the measurement object set in the SCG, the measurement result of the serving cell existing in the frequency corresponding to the measurement object set in the SCG, and the measurement of the neighboring cell. Results may be included. It may include routing information used in the BAP layer at the time of failure. In this case, the routing information may include an egress link and a next hop ID mapped to each routing ID, and may also include BH RLC channel mapping information used at this time.

According to an embodiment, the IAB node 3 900 may perform RLF detection of the IAB node 2 910 ( S900 ). IAB node 3 (900) may perform the SCGFaliureInformation Procedure (S905). The SCGFaliureInformation Procedure may include at least one of the following operations.

- TX suspension on SCG (egress BH RLC channel, SRB, DRB)

- Reset SCG MAC

- Routing entry update

- Transmission of SCGFaliureInformation (cause: legacy RLF)

The IAB node 3 900 may transmit the SCGFaliureInformation message to the IAB node 1 915 through SRB1 (S910). The IAB node 1 915 may transmit BH traffic to the donor CU 9200 (S915). The donor CU 920 may transmit BH traffic to the IAB node 1 915 (S920). The IAB node 1 915 may transmit an RRCReconfiguration message to the IAB node 3 900 through SRB1 (S925).

The RRCReconfiguration message transmitted in step S925 may include information for recovery when the IAB connection fails. For example, the RRCReconfiguration message may include an IP address to be used after reconnection in the DU part of the corresponding IAB node. When the IAB node 3 (900) receives the IP address in the RRCReconfiguration message, the received IAB node 3 (900) converts the IP address to the IP layer destination address of the DU without an additional IP address request operation after resuming the connection. can be used as Through this, the IAB node 3 900 may exchange the control signal and user plane signal of F1 in the IP layer with the CU and DU of the donor node.

10 is a diagram illustrating a case of SCG failure through RLF notification in an SA situation.

In FIG. 10, it can be assumed that IAB nodes 1 and 2 are connected to the CU of the donor node through an arbitrary relay link.

Node 4 is an IAB node, and has node 1 as the parent node of the MCG link and node 2 as the parent node of the SCG link. Node 4 has node 5 as a child node and can serve an SCG link. Node 3 may serve the MCG link of Node 5. When node 4 fails re-establishment, an RLF recovery failure notification may be delivered to a child node. The MT of the child node that has received this notification may consider that RLF has occurred in the received link. When node 5 receives an RLF recovery failure notification from node 4 of the SCG link, node 5 may perform an SCG failure information operation. SCG failure information may perform at least one of the following operations.

- Stop the transmission on the SCG. In this case, the target may be all SRBs, DRBs, and backhaul RLC channels/egress backhaul RLC channels.

- Reset the SCG MAC. If there is an RLC SDU or PDU that has failed transmission, it can be transmitted again to the MCG RLC stack without MAC reset.

- Update the routing entry of the IAB node. In this case, as a specific operation, a routing entry having a failed SCG link as an egress link in the BAP entity may be removed and replaced with an MCG link.

- The SCGFailureInformation message can be transmitted to the parent node of the MCG link through SRB 1. In this case, the cause value may be set to a value indicating a state in which the parent node that has transmitted the notification, for example, the SN has lost its connection to the parent node or the network. In the corresponding message, the measurement result value of the serving cell and the measurement result of the neighboring cell existing in the frequency corresponding to the measurement object set in the SCG, the measurement result of the serving cell existing in the frequency corresponding to the measurement object set in the MCG, and the measurement of the neighboring cell Results may not be included. Instead, it may include routing information used by the BAP layer at the time of failure. In this case, the routing information may include an egress link and a next hop ID mapped to each routing ID, and may also include BH RLC channel mapping information used at this time.

According to an embodiment, the IAB node 5 (1000) may receive an RLF recovery failure indication from the IAB node 4 (1010) (S1000). IAB node 5 (1000) may perform the SCGFailureinformation Procedure (S1005). The SCGFailureinformation Procedure may include at least one of the following operations.

- TX suspension on SCG (egress BH RLC channel, SRB, DRB)

- Reset SCG MAC

- Routing entry update

- Transmission of SCGFailureinformation(cause: failure_on_parent)

IAB node 5 (1000) may transmit an SCGFailureinformation message to IAB node 3 (1020) through SRB1 (S1010). The IAB node 3 1020 may transmit BH traffic to the donor CU 1030 (S1015). The donor CU 1030 may transmit BH traffic to the IAB node 3 1020 (S1020). The IAB node 3 1020 may transmit an RRCReconfiguration message to the IAB node 5 1000 through SRB1 (S1025).

The RRCReconfiguration message transmitted in step S1025 may include information for recovery when the IAB connection fails. For example, the RRCReconfiguration message may include an IP address to be used after reconnection in the DU part of the corresponding IAB node. When the IAB node 5 (1000) receives the IP address in the RRCReconfiguration message, the received IAB node 5 (1000) converts the IP address to the IP layer destination address of the DU without an additional IP address request operation after resuming the connection. can be used as Through this, the IAB node 5 (1000) can exchange the control signal and user plane signal of F1 in the IP layer with the CU and DU of the donor node.

11 is a diagram illustrating a case of SCG failure through RLF detection in a Non-Stand Alone (NSA) situation.

In FIG. 11, IAB nodes 1 and 2 are the MCG link using LTE RAT as the MN as the eNB and the SCG link using the NR RAT as the SN as the donor gNB. In this case, when RLF is detected in the SCG link, the MT of the IAB node may perform the SCG failure information operation.

SCG failure information may perform at least one of the following operations.

- Stop the transmission on the SCG. In this case, the target may be all SRBs, DRBs, and backhaul RLC channels/egress backhaul RLC channels.

- Reset the SCG MAC. If there is an RLC SDU or PDU that has failed transmission, it can be transmitted again to the MCG RLC stack without MAC reset.

- Update the routing entry of the IAB node. In this case, as a specific operation, a routing entry having a failed SCG link as an egress link in the BAP entity may be removed and replaced with an MCG link.

- The SCGFailureInformation message can be transmitted to the parent node of the MCG link through SRB 1. In this case, the cause value may be occurrence factors of general RLF detection, for example, T310 timer expiration, RLC maximum retransmission arrival, RACH problem occurrence, and the like. In the corresponding message, the measurement result value of the serving cell and the measurement result of the neighboring cell existing in the frequency corresponding to the measurement object set in the SCG, the measurement result of the serving cell existing in the frequency corresponding to the measurement object set in the MCG, and the measurement of the neighboring cell Results may be included. It may include routing information used in the BAP layer at the time of failure. In this case, the routing information may include an egress link and a next hop ID mapped to each routing ID, and may also include BH RLC channel mapping information used at this time.

According to an embodiment, the IAB node 1 1100 may perform RLF detection of the donor CU 1110 ( S1100 ). IAB node 1 (1100) may perform the SCGFailureInformation Procedure (S1105). The SCGFaliureInformation Procedure may include at least one of the following operations.

- TX suspension on SCG (egress BH RLC channel, SRB, DRB)

- Reset SCG MAC

- Routing entry update

- Transmission of SCGFaliureInformation (cause: legacy RLF cause)

The IAB node 1 1100 may transmit the SCGFaliureInformation message to the eNB 1120 through SRB1 (S1110). The eNB 1120 may transmit BH traffic to the Donor-gNB CU 1130 (S1115). Donor-gNB CU 1130 may transmit BH traffic to eNB 1120 (S1120). The eNB 1120 may transmit an RRCReconfiguration message to the IAB node 1 1100 through SRB1 (S1125).

The RRCReconfiguration message transmitted in step S1125 may include information for recovery when the IAB connection fails. For example, the RRCReconfiguration message may include an IP address to be used after reconnection in the DU part of the corresponding IAB node. When the IAB node 1 (1100) receives the IP address in the RRCReconfiguration message, the received IAB node 1 (1100) converts the IP address to the IP layer destination address of the DU without an additional IP address request operation after resuming the connection. can be used as Through this, the IAB node 1 1100 can exchange the control signal and user plane signal of F1 in the IP layer with the CU and DU of the donor node.

12A is a diagram illustrating a case of SCG failure through RLF notification in an NSA situation.

In FIG. 12A, IAB nodes 1 and 2 are the MCG link using LTE RAT as the MN as the eNB and the SCG link using the NR RAT as the SN as the donorgNB in an ENDC situation. In this case, when RLF is detected in the MCG link or MCG failure recovery fails, RRC connection re-establishment can be performed. If this re-establishment fails, the IAB node delivers the RLF recovery failure notification to the child node. can do. The child node receiving this notification may perform the SCG failure information operation in the MT.

SCG failure information may perform at least one of the following operations.

- Stop the transmission on the SCG. In this case, the target may be all SRBs, DRBs, and backhaul RLC channels/egress backhaul RLC channels.

- Reset the SCG MAC. If there is an RLC SDU or PDU that has failed transmission, it can be transmitted again to the MCG RLC stack without MAC reset.

- Update the routing entry of the IAB node. In this case, as a specific operation, a routing entry having a failed SCG link as an egress link in the BAP entity may be removed and replaced with an MCG link.

- The SCGFailureInformation message can be transmitted to the parent node of the MCG link through SRB 1. In this case, the cause value may be set to a value indicating a state in which the parent node that has transmitted the notification, for example, the SN has lost its connection to the parent node or the network. In the corresponding message, the measurement result value of the serving cell and the measurement result of the neighboring cell existing in the frequency corresponding to the measurement object set in the SCG, the measurement result of the serving cell existing in the frequency corresponding to the measurement object set in the MCG, and the measurement of the neighboring cell Results may not be included. It may include routing information used in the BAP layer at the time of failure. In this case, the routing information may include an egress link and a next hop ID mapped to each routing ID, and may also include BH RLC channel mapping information used at this time.

According to an embodiment, there may be an RRE failure in Node 1 1210 (S1200). Node 1 (1210) may transmit an RLF recovery failure indication to IAB node 2 (1200) (S1205). IAB node 2 (1200) may perform the SCGFailureInformation Procedure (S1210). The SCGFaliureInformation Procedure may include at least one of the following operations.

- TX suspension on SCG (egress BH RLC channel, SRB, DRB)

- Reset SCG MAC

- Release BAP entity

- Transmission of SCGFaliureInformation (cause: failure_on_parent)

The IAB node 2 1200 may transmit the SCGFaliureInformation message to the eNB 1220 through SRB1 (S1215). The eNB 1220 may transmit BH traffic to the donor CU 1230 (S1220). The donor CU 1230 may transmit BH traffic to the eNB 1220 (S1225). The eNB 1120 may transmit an RRCReconfiguration message to the IAB node 2 1200 through SRB1 (S1230).

The RRCReconfiguration message transmitted in step S1230 may include information for recovery when the IAB connection fails. For example, the RRCReconfiguration message may include an IP address to be used after reconnection in the DU part of the corresponding IAB node. When the IAB node 2 1200 receives the IP address in the RRCReconfiguration message, the received IAB node 2 1200 converts the IP address to the IP layer destination address of the DU without an additional IP address request operation after resuming the connection. can be used as Through this, the IAB node 2 1200 may exchange the control signal and user plane signal of F1 in the IP layer with the CU and DU of the donor node.

In another embodiment, after the IAB node transmits the SCGFailureInformation to the MN, a separate timer may be operated. If the MT does not receive the NR RRC message during the timer, the IAB node may perform an RRC re-establishment operation.

12B is a diagram illustrating a case in which RLF recovery failure notification due to SCG release is transmitted.

As the MT sends SCGFailureInformation to the MN and requests SCG release from the donor gNB, when the MN requests NR SCG release, the MT receiving the message transmits the RLF recovery failure notification to the child node before the MT releases the SCG. can The child node that has received this notification can perform the SCG failure information operation again. In this case, too, the cause value may be a value due to the absence of network connection of the parent node corresponding to the SN. The SCG failure information may include cell measurement values of the MO configured in the SN measured by the MT and cell measurement values of the MO configured in the MN. In this case, as another embodiment, when the IAB node receives the RLF recovery failure notification, it may perform handover to a previously defined target cell. Before performing handover, the gNB CU may signal a specific target cell candidate group to the IAB node through RRCReconfiguration. This signal may include conditions for performing handover to the corresponding candidate target cell and configuration information to be used in the corresponding target cell.

According to an embodiment, there may be an RRE failure in Node 1 1210 (S1235). Node 1 1210 may transmit an RLF recovery failure indication to IAB node 2 1200 (S1240). IAB node 2 (1200) may perform the SCGFailureInformation Procedure (S1245). The SCGFaliureInformation Procedure may include at least one of the following operations.

- TX suspension on SCG (egress BH RLC channel, SRB, DRB)

- Reset SCG MAC

- Release BAP entity

- Transmission of SCGFaliureInformation (cause: failure_on_parent)

The IAB node 2 1200 may transmit the SCGFaliureInformation message to the eNB 1220 through SRB1 (S1250). The eNB 1220 may transmit BH traffic to the donor CU 1230 (S1255). It may be a Found no alternative case in the donor CU 1230 (S1260). The donor CU 1230 may transmit BH traffic to the eNB 1220 (S1265). The eNB 1120 may transmit an SCG Release message to the IAB node 2 1200 through SRB1 (S1270). IAB node 2 (1200) may transmit an RLF recovery failure indication to the IAB node 3 (1240) (S1275). IAB node 2 (1200) may perform RRC release (S1280). IAB node 3 (1240) may perform the SCGFailureInformation Procedure (S1285). For example, it may be SCGFailureInformation(cause: failure_on_parent).

13A is a flowchart illustrating a cell selection operation for a mobile terminal (MT) to access an IAB node included in the same donor gNB during connection re-establishment.

Once the IAB node performs re-establishment for some reason, it may be necessary to first perform a cell selection process. When selecting a cell, cell information belonging to the corresponding IAB node is delivered to the IAB MT to select an IAB node connected to the same donor gNB or CU as the donor gNB or CU accessed in the previous connection state.

Specifically, the transmitted information may be the gNB ID or donor CU ID of the donor gNB, or list information of the physical cell id (PCI) or cell global id (CGI) of cells currently connected to the gNB and the CU. have.

The method of delivery may vary depending on the information being delivered. As a method of delivery, when configured in the IAB network as an IAB MT, the donor gNB's gNB ID, CU ID, or PCI or CGI information of the cells currently connected to the CU is delivered as an RRC reconfiguration or RRCsetup message from the donor CU upon initial connection. can be If the gNB id/CU id is given to the IAB, DUs of all IAB nodes currently connected to the donor gNB may broadcast the current donor gNB id/CU id as SIB information. In this case, when the MT acquires a corresponding SIB when selecting a cell, compares the gNB/CU id stored by the MT and the id being broadcast, and if they are the same, the cell selection can be continued. In another case, when the MT is also configured in the IAB network, the list of cells may be received from the donor CU in an RRC reconfiguration or RRCSetup message upon initial access. In this case, when the MT performs cell search or detection for reselection, the PCI existing in the list may be preferentially selected based on the PCI value. After that, the final selection may be completed by additionally determining whether it is suitable using the existing cell selection metric.

According to an embodiment, when the MT acquires the id of the donor gNB or donor CU from the network, cell selection may be started (S1300) and cell detection may be performed (S1305). The MT may measure the quality of the detected cell (S310). For example, cell quality can be measured through SSB. After that, it is possible to read SIB1 to acquire a factor value required for selection. At the same time, the donor gNB/CU id present in SIB X read additionally from SIB 1 or thereafter may be acquired (S1315). With the acquired information, it can be determined whether the cell selection criteria of the corresponding cell are satisfied, whether the corresponding cell has an IAB-support indicator, and whether the corresponding cell is the same node as the donor gNB/CU to which it was previously accessed (S1320). If all are satisfied, the MT may complete the selection of the corresponding cell (S1325).

13B is a diagram illustrating a case in which an MT receives an indicator related to a current donor gNB/CU in an RRC message when an IAB network is combined.

In FIG. 13b , the MT receives an indicator related to the current donor gNB/CU as an RRC message when combining the IAB network, and then receives the gNB/CU ID through the SIB after cell detection when performing re-establishment. In cell suitability evaluation, if If it is the same gNB/CU ID as that previously accessed, if the remaining suitability criteria and IAB support are satisfied, cell selection can be performed with the corresponding IAB node.

According to an embodiment, the child node MT 1310 may transmit an RRCsetupRequest to the parent IAB node 1320 (S1330). The parent IAB node 1320 may transmit BH traffic including the RRCsetupRequest message to the donor CU 1330 (S1332). The donor CU 1330 may transmit BH traffic including an RRC message in response to the RRCsetupRequest message to the parent IAB node 1320 (S1334). The parent IAB node 1320 may transmit the RRCsetup message to the child node MT 1310 including the donor gNB/CU ID (S1336). The child node MT 1310 may transmit RRCsetupComplete to the parent IAB node 1320 (S1338). Alternatively, the parent IAB node 1320 may transmit the donor gNB/CU ID including the donor gNB/CU ID in the RRCreconfiguration message to the child node MT 1310 (S1340). In response to the RRCreconfiguration message, the child node MT 1310 may transmit RRCreconfigurationComplete to the parent IAB node 1320 (S1342). Thereafter, the child node MT 1310 may perform RRC re-establishment (S1344). Childe node MT 1310 may perform cell detection/measure (S1346) and receive SIB X including donor gNB/CU ID from the selected cell 1300 (S1348). Childe node MT 1310 may perform Evaluation of cell selection (S1350). The Evaluation of cell selection may be performed using at least one of the following included in the received SIB X.

- Use S criteria to evaluate S criteria

- Assess IAB support using an IAB-support indication

- Using gNB/CU ID to evaluate whether the selected cell corresponds to the same gNB/CU

13c is a diagram illustrating a case in which the MT receives information on cell IDs accessible under the current donor gNB/CU in an RRC message when the MT is combined with the IAB network.

In FIG. 13c , the MT receives information on cell IDs (eg, PCI, CGI) that can be accessed under the current donor gNB/CU as an RRC message when the MT is combined with the IAB network, and then the cell is detected when the re-establishment is performed. If it corresponds to the accessible cells, after receiving SIB1, if the remaining suitability criteria and IAB support are satisfied, cell selection can be performed with the corresponding IAB node.

The donor gNB/CU ID or possible cell id is included in the RRC release message or RRCrelease with suspend, so that when the MT enters the Inactive or Idle state, the same operation is performed during cell selection and reselection. can For example, it can be used as a suitability condition when selecting/reselecting a cell.

According to an embodiment, the child node MT 1310 may transmit an RRCsetupRequest message to the parent IAB node 1320 (S1360). The parent IAB node 1320 may transmit BH traffic including the RRCsetupRequest message to the donor CU 1330 (S1362). The donor CU 1330 may transmit an RRC message corresponding to the RRCsetupRequest message to the parent IAB node 1320 through BH traffic (S1364). The parent IAB node 1320 may include the available cell list in the RRCsetup message and transmit it to the child node MT 1310 (S1366). The child node MT 1310 may transmit RRCsetupComplete to the parent IAB node 1320 (S1368). The parent IAB node 1320 may transmit the RRCreconfiguration message including the available cell list to the child node MT 1310 (S1370). The child node MT 1310 may transmit RRCreconfigurationComplete to the parent IAB node 1320 (S1372). Thereafter, the child node MT 1310 may perform RRC re-establishment (S1374). Childe node MT 1310 may perform Cell detection/measure (S1376) and receive the SSB of the detected cell to perform Check PCI, if PCI is in available cell list, further receive SIB1 (S1378). When PCI is included in the list, the Chile node MT 1310 may receive SIB 1 from the Selected cell 1300 (S1380). The Childe node MT 1310 may perform Evaluation of cell selection (S1382). ).The Evaluation of cell selection can be performed using at least one of the following.

- S criteria

- IAB-support

14 is a flowchart illustrating a cell selection operation for the MT not to access its lower IAB node during connection re-establishment.

14 is an operation for not performing cell selection to a cell of its own lower IAB node during re-establishment of the MT. In this case, the MT may receive cell information of its own lower IAB nodes from the donor CU. When receiving corresponding cell information through an RRC setup or RRC reconfiguration message upon initial access, when the MT performs cell selection (S1400), cell detection may be performed (S1405). MT can measure the quality of detected cells. For example, the SSB may be measured (S1410). From the point in time when PCI can be identified, it can be determined whether the corresponding cell is a cell in the blacklist or not. For example, a blacklist may be checked at the corresponding frequency (1415). If it is a cell that exists in the blacklist, you can exclude the cell from cell selection, detect another cell, and perform cell selection. If the cell does not exist in the blacklist, the rest of the cell suitability check can be performed. For example, the MT may receive SIB 1 (S1420). The cell suitability check may, for example, determine whether the S criterion is satisfied or whether there is an IAB-support indicator (S1425). If both are satisfied, the MT may complete the selection of the corresponding cell (S1430).

The available cell list may be included in the RRC release message as well as the RRC setup/reconfiguration message. Therefore, when the MT goes to the idle mode or operates in the inactive mode, it is possible to determine whether the corresponding cell is included in the black list during cell selection and reselection and exclude it from selection.

Embodiments of the present invention disclosed in the present specification and drawings are merely provided for specific examples in order to easily explain the technical contents of the present invention and help the understanding of the present invention, and are not intended to limit the scope of the present invention. It will be apparent to those of ordinary skill in the art to which the present invention pertains that other modifications based on the technical spirit of the present invention can be implemented in addition to the embodiments disclosed herein.

Claims (1)

A control signal processing method in a wireless communication system, comprising:
Receiving a first control signal transmitted from the base station;
processing the received first control signal; and
and transmitting a second control signal generated based on the processing to the base station.

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