Method and apparatus for controlling wireless relay operation

Abstract

The present disclosure provides a technology for controlling a wireless relay operation and provides a method and an apparatus, wherein a method by which a wireless access backhaul (WAB) node performs an integration operation comprises the steps of: performing an RRC connection setup procedure with a WAB-mobile terminal (MT) serving gNB, to perform an operation of setting up a WAB-MT of a WAB node; configuring, by operations, administration, and management (OAM), a WAB-gNB of the WAB node; and performing, by the WAB-gNB of the WAB node, an NG connection setup operation with a core network entity.

Description

Method for controlling wireless relay operation and device therefor

[0001] The present disclosure relates to a technique for controlling a WAB node performing an NR-based wireless relay function.

[0002] In wireless communication systems, relay technology has been used to expand cell coverage by using additional network nodes.

[0003] Therefore, the relay technology to which the conventional LTE technology is applied supported data transmission at the IP packet level of the relay node, and only one relay node was configured to transmit IP packets between the terminal and the base station.

[0004] In other words, relay technology applied to existing LTE technology only offered single-hop relay functionality for simple service provision, and most configurations were dictated by static Operations, Administration, and Management (OAM). Consequently, multi-hop relays could not be configured.

[0005] In addition, when attempting to support multi-hop relaying through conventional LTE technology, data could not be distinguished and processed through multiple relay nodes, and signaling and data processing above the IP layer had the problem of increasing delay.

[0006] To solve these problems, IAB (Integrated Access and Backhaul) technology was proposed, but its limited structure and functionality limited its ability to support various use cases.

[0007] The present disclosure seeks to provide a technique for controlling wireless relay operation.

[0008] In one aspect, the present embodiments may provide a method for a WAB (Wireless Access Backhaul) node to perform an integration operation, the method including a step of performing an operation of setting up a WAB-MT (WAB-Mobile Terminal) of the WAB node by performing an RRC connection setup procedure with a WAB-MT serving base station, a step of configuring a WAB-base station (WAB-gNB) of the WAB node by OAM (Operations, administration and management), and a step of performing an NG connection setup operation by the WAB-base station of the WAB node with a core network entity.

[0009] In another aspect, the present embodiments may provide a WAB node device including a WAB (Wireless Access Backhaul) node that performs an integration operation, performs an operation of setting up a WAB-MT (WAB-Mobile Terminal) of the WAB node by performing an RRC connection setup procedure with a WAB-MT serving base station, configures a WAB-base station (WAB-gNB) of the WAB node by OAM (Operations, administration and management), and a control unit that performs an NG connection setup operation with a core network entity, a receiving unit that receives a signal from a WAB-MT serving base station, a terminal and a core network entity, and a transmitting unit that transmits a signal to the WAB-MT serving base station, the terminal and the core network entity.

[0010] The present disclosure may provide a technique for controlling wireless relay operation.

[0011] FIG. 1 is a schematic diagram illustrating the structure of an NR wireless communication system to which the present embodiment can be applied.

[0012] FIG. 2 is a drawing for explaining a frame structure in an NR system to which the present embodiment can be applied.

[0013] FIG. 3 is a diagram for explaining a resource grid supported by a wireless access technology to which the present embodiment can be applied.

[0014] FIG. 4 is a diagram for explaining a bandwidth part supported by a wireless access technology to which the present embodiment can be applied.

[0015] FIG. 5 is a diagram illustrating an example of a synchronization signal block in a wireless access technology to which the present embodiment can be applied.

[0016] FIG. 6 is a diagram for explaining a random access procedure in a wireless access technology to which the present embodiment can be applied.

[0017] Figure 7 is a drawing for explaining CORESET.

[0018] FIG. 8 and FIG. 9 are diagrams illustrating an IAB structure according to one embodiment.

[0019] FIG. 10 is a diagram illustrating a parent node and child node relationship for an IAB node according to one embodiment.

[0020] Fig. 11 is a diagram for explaining the operation of a WAB node according to one embodiment.

[0021] FIG. 12 is a diagram illustrating the functional structure of a WAB node according to one embodiment.

[0022] FIG. 13 is a drawing for explaining an example of a wireless relay structure according to one embodiment.

[0023] FIG. 14 is a drawing for explaining another example of a wireless relay structure according to one embodiment.

[0024] Fig. 15 is a diagram showing the configuration of a WAB node according to another embodiment.

[0025] Hereinafter, some embodiments of the present disclosure will be described in detail with reference to exemplary drawings. When adding reference numerals to components in each drawing, identical components may have the same numerals as much as possible even if they are shown in different drawings. In addition, when describing the present embodiments, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the technical idea of ​​the present invention, the detailed description may be omitted. When "includes," "has," "consists of," etc. are used in this specification, other parts may be added unless "only" is used. When a component is expressed in the singular, it may include a case in which the plural is included unless specifically stated otherwise.

[0026] Additionally, terms such as first, second, A, B, (a), (b), etc. may be used to describe components of the present disclosure. These terms are only intended to distinguish the components from other components, and the nature, order, sequence, or number of the components are not limited by the terms.

[0027] In a description of the positional relationship of components, when it is described that two or more components are "connected," "combined," or "connected," it should be understood that the two or more components may be directly "connected," "combined," or "connected," but that the two or more components may also be further "interposed" with another component to be "connected," "combined," or "connected." Here, the other component may be included in one or more of the two or more components that are "connected," "combined," or "connected" to each other.

[0028] In the description of the temporal flow relationship related to components, operation methods, or manufacturing methods, for example, when the temporal or flow relationship is described as “after”, “following”, “next to”, “before”, etc., it may also include cases where it is not continuous, unless “immediately” or “directly” is used.

[0029] Meanwhile, when numerical values ​​or corresponding information (e.g., levels, etc.) for components are mentioned, even without separate explicit description, the numerical values ​​or corresponding information may be interpreted as including an error range that may occur due to various factors (e.g., process factors, internal or external impact, noise, etc.).

[0030] The wireless communication system in this specification refers to a system for providing various communication services such as voice, data packets, etc. using wireless resources, and may include a terminal, a base station, or a core network.

[0031] The embodiments disclosed below can be applied to wireless communication systems using various wireless access technologies. For example, the embodiments can be applied to various wireless access technologies such as CDMA (code division multiple access), FDMA (frequency division multiple access), TDMA (time division multiple access), OFDMA (orthogonal frequency division multiple access), SC-FDMA (single carrier frequency division multiple access), or NOMA (non-orthogonal multiple access). In addition, the wireless access technology may not only refer to a specific access technology, but also to each generation of communication technologies established by various communication agreement organizations such as 3GPP, 3GPP2, WiFi, Bluetooth, IEEE, and ITU. For example, CDMA can be implemented with wireless technologies such as UTRA (universal terrestrial radio access) or CDMA2000. TDMA can be implemented with wireless technologies such as GSM (global system for mobile communications) / GPRS (general packet radio service) / EDGE (enhanced data rates for GSM evolution). OFDMA can be implemented in wireless technologies such as IEEE (Institute of Electrical and Electronics Engineers) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, and E-UTRA (evolved UTRA). IEEE 802.16m is an evolution of IEEE 802.16e and provides backward compatibility with systems based on IEEE 802.16e.UTRA is part of UMTS (universal mobile telecommunications system). 3GPP (3rd generation partnership project) LTE (long term evolution) is part of E-UMTS (evolved UMTS) that uses E-UTRA (evolved-UMTSterrestrial radio access), employing OFDMA in the downlink and SC-FDMA in the uplink. Thus, the present embodiments can be applied to currently disclosed or commercialized wireless access technologies, as well as wireless access technologies currently under development or to be developed in the future.

[0032] Meanwhile, the term "terminal" in this specification is a comprehensive concept that refers to a device that includes a wireless communication module that performs communication with a base station in a wireless communication system, and should be interpreted as a concept that includes not only UE (User Equipment) in WCDMA, LTE, NR, HSPA, and IMT-2020 (5G or New Radio), but also MS (Mobile Station), UT (User Terminal), SS (Subscriber Station), and wireless device in GSM. In addition, the terminal may be a user portable device such as a smartphone depending on the usage type, and in a V2X communication system, it may mean a vehicle, a device including a wireless communication module in the vehicle, etc. In addition, in the case of a Machine Type Communication system, it may mean an MTC terminal, M2M terminal, URLLC terminal, etc. that is equipped with a communication module to perform machine type communication.

[0033] The base station or cell in this specification refers to an end that communicates with a terminal in terms of a network, and includes various coverage areas such as Node-B, eNB (evolved Node-B), gNB (gNode-B), LPN (Low Power Node), Sector, Site, various types of antennas, BTS (Base Transceiver System), Access Point, Point (e.g., Transmission Point, Reception Point, Transmission / Reception Point), Relay Node, Mega Cell, Macro Cell, Micro Cell, Pico Cell, Femto Cell, RRH (Remote Radio Head), RU (Radio Unit), and Small Cell. In addition, a cell may mean including a BWP (Bandwidth Part) in the frequency domain. For example, a serving cell may mean an Activation BWP of a terminal.

[0034] Since the various cells listed above have a base station that controls one or more cells, the base station can be interpreted in two meanings. 1) It can be a device itself that provides a mega cell, macro cell, micro cell, pico cell, femto cell, or small cell in relation to a wireless area, or 2) it can indicate the wireless area itself. In 1), all devices that provide a given wireless area are controlled by the same entity or that interact to cooperatively configure the wireless area are all indicated as a base station. Depending on how the wireless area is configured, a point, a transceiver point, a transmission point, a reception point, etc. can be an embodiment of a base station. In 2), the wireless area itself that receives or transmits a signal from the perspective of a user terminal or a neighboring base station can also be indicated as a base station.

[0035] In this specification, a cell may mean a component carrier having coverage of a signal transmitted from a transmission / reception point or a transmission / reception point itself.

[0036] Uplink (UL, or uplink) refers to a method of transmitting and receiving data from a terminal to a base station, and downlink (DL, or downlink) refers to a method of transmitting and receiving data from a base station to a terminal. Downlink may refer to communication or a communication path from multiple transmission / reception points to a terminal, and uplink may refer to communication or a communication path from a terminal to multiple transmission / reception points. In this case, in the downlink, the transmitter may be part of the multiple transmission / reception points, and the receiver may be part of the terminal. In addition, in the uplink, the transmitter may be part of the terminal, and the receiver may be part of the multiple transmission / reception points.

[0037] Uplink and downlink transmit and receive control information through control channels such as PDCCH (Physical Downlink Control CHannel) and PUCCH (Physical Uplink Control CHannel), and transmit and receive data by configuring data channels such as PDSCH (Physical Downlink Shared CHannel) and PUSCH (Physical Uplink Shared CHannel). Hereinafter, the situation in which signals are transmitted and received through channels such as PUCCH, PUSCH, PDCCH, and PDSCH is also expressed in the form of 'transmitting and receiving PUCCH, PUSCH, PDCCH, and PDSCH.'

[0038] For clarity of explanation, the technical idea of ​​this invention is described below mainly with reference to the 3GPP LTE / LTE-A / NR (New RAT) communication system, but the technical features of this invention are not limited to the communication system.

[0039] After researching 4G (4th-Generation) communication technology, 3GPP develops 5G (5th-Generation) communication technology to meet the requirements of the next-generation wireless access technology of the ITU-R. Specifically, 3GPP develops LTE-A pro, which is an enhancement of LTE-Advanced technology to meet the requirements of the ITU-R, as a 5G communication technology, and NR, a new communication technology separate from 4G communication technology. Both LTE-A pro and NR refer to 5G communication technology, and in the following, 5G communication technology will be explained with NR as the focus, unless a specific communication technology is specified.

[0040] The operating scenario in NR defines various operation scenarios by adding considerations for satellites, automobiles, and new verticals to the existing 4G LTE scenario, and in terms of service, it supports the eMBB (Enhanced Mobile Broadband) scenario, the mMTC (Massive Machine Communication) scenario that has high terminal density but is deployed over a wide area and requires low data rate and asynchronous access, and the URLLC (Ultra Reliability and Low Latency) scenario that requires high responsiveness and reliability and can support high-speed mobility.

[0041] To meet these scenarios, NR introduces a wireless communication system that incorporates new waveform and frame structure technologies, low latency technologies, support for ultra-high frequency bands (mmWave), and forward compatibility technologies. In particular, NR systems offer various technological changes in terms of flexibility to ensure forward compatibility. The key technical features of NR are described below with reference to the drawings.

[0042] <NR 시스템 일반>

[0043] Figure 1 is a schematic diagram illustrating the structure of an NR system to which the present embodiment can be applied.

[0044] Referring to Fig. 1, the NR system is divided into 5GC (5G Core Network) and NR-RAN parts, and the NG-RAN is composed of gNBs and ng-eNBs that provide user plane (SDAP / PDCP / RLC / MAC / PHY) and control plane (RRC) protocol termination for UE (User Equipment). gNBs or gNBs and ng-eNBs are interconnected via the Xn interface. gNBs and ng-eNBs are each connected to the 5GC via the NG interface. The 5GC can be configured to include an AMF (Access and Mobility Management Function) that is responsible for the control plane such as terminal access and mobility control functions, and an UPF (User Plane Function) that is responsible for the control function for user data. NR includes support for both frequency bands below 6 GHz (FR1, Frequency Range 1) and frequency bands above 6 GHz (FR2, Frequency Range 2).

[0045] gNB refers to a base station that provides NR user plane and control plane protocol termination to terminals, and ng-eNB refers to a base station that provides E-UTRA user plane and control plane protocol termination to terminals. The base station described in this specification should be understood to encompass both gNB and ng-eNB, and may also be used to refer to gNB or ng-eNB separately as needed.

[0046] <NR 웨이브 폼,뉴머롤러지 및 프레임 구조>

[0047] NR uses the CP-OFDM waveform with a cyclic prefix for downlink transmission, and CP-OFDM or DFT-s-OFDM for uplink transmission. OFDM technology is easily combined with MIMO (Multiple Input Multiple Output) and offers the advantages of high spectral efficiency and low-complexity receivers.

[0048] Meanwhile, in NR, the requirements for data rates, latency, and coverage differ across the three scenarios mentioned above. Therefore, it is necessary to efficiently satisfy these requirements across the frequency bands that comprise any NR system. To this end, technologies have been proposed to efficiently multiplex radio resources based on multiple different numerologies.

[0049] Specifically, the NR transmission numerator is determined based on the sub-carrier spacing and the cyclic prefix (CP), and is changed exponentially using the μ value as an exponent value of 2 based on 15 kHz, as shown in Table 1 below.

[0050] μsubcarrier intervalCyclic prefixSupported for dataSupported for synch015NormalYesYes130NormalYesYes260Normal, ExtendedYesNo3120NormalYesYes4240NormalNoYes

[0051] As shown in Table 1 above, the numerology of NR can be divided into five types according to the subcarrier spacing. This is different from the fixed 15 kHz subcarrier spacing of LTE, one of the 4G communication technologies. Specifically, the subcarrier spacing used for data transmission in NR is 15, 30, 60, and 120 kHz, and the subcarrier spacing used for synchronization signal transmission is 15, 30, 120, and 240 kHz. In addition, the extended CP is applied only to the 60 kHz subcarrier spacing. Meanwhile, the frame structure in NR is defined as a 10 ms frame consisting of 10 subframes of the same length of 1 ms. One frame can be divided into 5 ms half frames, and each half frame contains 5 subframes. In the case of a 15 kHz subcarrier spacing, one subframe consists of one slot, and each slot consists of 14 OFDM symbols. FIG. 2 is a diagram for explaining the frame structure in an NR system to which the present embodiment can be applied.

[0052] Referring to Fig. 2, a slot is fixedly composed of 14 OFDM symbols in the case of a normal CP, but the length of the slot in the time domain may vary depending on the subcarrier spacing. For example, in the case of a numerology with a 15 kHz subcarrier spacing, a slot is composed of 1 ms in length, which is the same length as a subframe. In contrast, in the case of a numerology with a 30 kHz subcarrier spacing, a slot is composed of 14 OFDM symbols, but two slots may be included in one subframe with a length of 0.5 ms. In other words, subframes and frames are defined with fixed time lengths, while slots are defined by the number of symbols, and their time lengths may vary depending on the subcarrier spacing.

[0053] Meanwhile, NR defines slots as the basic scheduling unit and also introduces mini-slots (or sub-slots, or non-slot-based scheduling) to reduce transmission delay in the wireless section. Using wider subcarrier spacing reduces transmission delay in the wireless section by shortening the length of each slot inversely. Mini-slots (or sub-slots) are designed to efficiently support URLLC scenarios and allow scheduling in units of 2, 4, or 7 symbols.

[0054] Furthermore, unlike LTE, NR defines uplink and downlink resource allocation at the symbol level within a single slot. To reduce HARQ delay, a slot structure was defined that allows HARQ ACK / NACK to be transmitted directly within the transmission slot. This slot structure is referred to as a self-contained structure and will be described in detail.

[0055] NR is designed to support a total of 256 slot formats, of which 62 are used in 3GPP Rel-15. It also supports a common frame structure that configures FDD or TDD frames through various combinations of slots. For example, it supports a slot structure in which all symbols in a slot are set to downlink, a slot structure in which all symbols are set to uplink, and a slot structure in which downlink and uplink symbols are combined. NR also supports data transmission being distributed and scheduled across one or more slots. Therefore, a base station can use a slot format indicator (SFI) to inform a UE whether a slot is a downlink slot, an uplink slot, or a flexible slot. The base station can indicate the slot format by indicating an index of a table configured through UE-specific RRC signaling using the SFI, and can also indicate it dynamically through DCI (Downlink Control Information) or statically or semi-statically through RRC.

[0056] <NR 물리 자원 >

[0057] In relation to physical resources in NR, antenna ports, resource grids, resource elements, resource blocks, and bandwidth parts are considered.

[0058] Antenna ports are defined such that the channel through which a symbol on an antenna port is carried can be inferred from the channel through which another symbol on the same antenna port is carried. Two antenna ports are said to be quasi co-located (QC / QCL) if the large-scale properties of the channel through which a symbol on one antenna port is carried can be inferred from the channel through which a symbol on the other antenna port is carried. Here, the large-scale properties include one or more of delay spread, Doppler spread, frequency shift, average received power, and received timing.

[0059] FIG. 3 is a diagram for explaining a resource grid supported by a wireless access technology to which the present embodiment can be applied.

[0060] Referring to Figure 3, a resource grid may exist for each numeral, as NR supports multiple numerals on the same carrier. Furthermore, resource grids may exist based on antenna ports, subcarrier spacing, and transmission direction.

[0061] A resource block (RB) consists of 12 subcarriers and is defined solely in the frequency domain. Furthermore, a resource element (RE) consists of one OFDM symbol and one subcarrier. Therefore, as shown in Figure 3, the size of a single RB can vary depending on the subcarrier spacing. NR also defines "Point A," which serves as a common reference point for the RB grid, as well as common RBs and virtual RBs.

[0062] FIG. 4 is a diagram for explaining a bandwidth part supported by a wireless access technology to which the present embodiment can be applied.

[0063] Unlike LTE, where the carrier bandwidth is fixed at 20 MHz, NR sets the maximum carrier bandwidth from 50 MHz to 400 MHz for each subcarrier interval. Therefore, it is not assumed that all terminals will use the entire carrier bandwidth. Accordingly, NR allows terminals to designate bandwidth parts (BWPs) within the carrier bandwidth, as illustrated in Figure 4. Furthermore, bandwidth parts are associated with a single numerology, consist of a subset of consecutive common resource blocks, and can be dynamically activated over time. Each terminal is configured with up to four bandwidth parts for both the uplink and downlink, and data is transmitted and received using the bandwidth parts activated at a given time.

[0064] In the case of a paired spectrum, the uplink and downlink bandwidth parts are set independently, and in the case of an unpaired spectrum, the downlink and uplink bandwidth parts are set in pairs so that they can share a center frequency to prevent unnecessary frequency re-tuning between downlink and uplink operations.

[0065] <NR 초기 접속>

[0066] In NR, a terminal performs cell search and random access procedures to connect to a base station and perform communication.

[0067] Cell search is a procedure in which a terminal synchronizes to the cell of a corresponding base station, obtains a physical layer cell ID, and obtains system information using the synchronization signal block (SSB) transmitted by the base station.

[0068] FIG. 5 is a diagram illustrating an example of a synchronization signal block in a wireless access technology to which the present embodiment can be applied.

[0069] Referring to FIG. 5, SSB is composed of a primary synchronization signal (PSS) and a secondary synchronization signal (SSS), each occupying 1 symbol and 127 subcarriers, and a PBCH spanning 3 OFDM symbols and 240 subcarriers.

[0070] The terminal receives SSB by monitoring SSB in the time and frequency domain.

[0071] SSB can be transmitted up to 64 times in 5ms. Multiple SSBs are transmitted in different transmission beams within 5ms, and the terminal performs detection assuming that SSBs are transmitted every 20ms based on a specific beam used for transmission. The number of beams that can be used for SSB transmission within 5ms can increase as the frequency band increases. For example, up to 4 SSB beams can be transmitted below 3GHz, up to 8 in the frequency band between 3GHz and 6GHz, and up to 64 different beams can be used for SSB transmission in the frequency band above 6GHz.

[0072] SSB contains two symbols in one slot, and the starting symbol and number of repetitions within the slot are determined as follows depending on the subcarrier spacing.

[0073] Meanwhile, unlike SS in conventional LTE, SSB is not transmitted at the center frequency of the carrier bandwidth. This means that SSB can be transmitted even in locations other than the center of the system bandwidth, and when supporting wideband operation, multiple SSBs can be transmitted in the frequency domain. Accordingly, the terminal monitors SSB using the synchronization raster, which is a candidate frequency location for monitoring SSB. The carrier raster, which is the center frequency location information of the channel for initial access, and the synchronization raster are newly defined in NR. The synchronization raster has a wider frequency interval than the carrier raster, which can support the terminal's fast SSB search.

[0074] A UE can obtain the MIB through the PBCH of the SSB. The MIB (Master Information Block) includes the minimum information required for the UE to receive the remaining system information (RMSI, Remaining Minimum System Information) broadcast by the network. In addition, the PBCH may include information on the position of the first DM-RS symbol in the time domain, information for the UE to monitor SIB1 (e.g., SIB1 numerology information, information related to SIB1 CORESET, search space information, PDCCH-related parameter information, etc.), offset information between the common resource block and the SSB (the absolute position of the SSB within the carrier is transmitted through SIB1), etc. Here, the SIB1 numerology information is also applied equally to some messages used in the random access procedure for the UE to access the base station after completing the cell search procedure. For example, the numerology information of SIB1 may be applied to at least one of messages 1 to 4 for the random access procedure.

[0075] The aforementioned RMSI may refer to SIB1 (System Information Block 1), and SIB1 is broadcast periodically (e.g., every 160 ms) in the cell. SIB1 contains information necessary for the UE to perform the initial random access procedure and is periodically transmitted via PDSCH. In order for the UE to receive SIB1, it must receive numerology information used for SIB1 transmission and CORESET (Control Resource Set) information used for SIB1 scheduling via PBCH. The UE checks scheduling information for SIB1 using SI-RNTI in CORESET and acquires SIB1 on PDSCH according to the scheduling information. The remaining SIBs, excluding SIB1, may be transmitted periodically or upon request of the UE.

[0076] FIG. 6 is a diagram for explaining a random access procedure in a wireless access technology to which the present embodiment can be applied.

[0077] Referring to FIG. 6, once cell search is complete, the terminal transmits a random access preamble for random access to the base station. The random access preamble is transmitted via the PRACH. Specifically, the random access preamble is transmitted to the base station via the PRACH, which consists of consecutive radio resources in a specific slot that is periodically repeated. Generally, when a terminal initially accesses a cell, a contention-based random access procedure is performed, and when performing random access for beam failure recovery (BFR), a non-contention-based random access procedure is performed.

[0078] The terminal receives a random access response to the transmitted random access preamble. The random access response may include a random access preamble identifier (ID), an UL Grant (uplink radio resource), a temporary C-RNTI (Temporary Cell - Radio Network Temporary Identifier), and a TAC (Time Alignment Command). Since one random access response may include random access response information for one or more terminals, the random access preamble identifier may be included to indicate which terminal the included UL Grant, temporary C-RNTI, and TAC are valid for. The random access preamble identifier may be an identifier for the random access preamble received by the base station. The TAC may be included as information for the terminal to adjust uplink synchronization. The random access response may be indicated by a random access identifier on the PDCCH, i.e., an RA-RNTI (Random Access - Radio Network Temporary Identifier).

[0079] Upon receiving a valid random access response, the terminal processes the information contained in the random access response and performs scheduled transmission to the base station. For example, the terminal applies TAC and stores a temporary C-RNTI. Furthermore, using the UL Grant, the terminal transmits data stored in its buffer or newly generated data to the base station. In this case, information that identifies the terminal must be included.

[0080] Finally, the terminal receives a downlink message for contention resolution.

[0081] <NR CORESET>

[0082] The downlink control channel in NR is transmitted in a CORESET (Control Resource Set) with a length of 1 to 3 symbols, and transmits uplink / downlink scheduling information, SFI (Slot format Index), and TPC (Transmit Power Control) information.

[0083] To ensure system flexibility, NR introduced the CORESET concept. CORESET (Control Resource Set) refers to time-frequency resources for downlink control signals. A terminal can decode control channel candidates using one or more search spaces within the CORESET time-frequency resources. A QCL (Quasi CoLocation) assumption is established for each CORESET, which is used to inform the characteristics of analog beam direction in addition to the delay spread, Doppler spread, Doppler shift, and average delay assumed by the conventional QCL.

[0084] Figure 7 is a drawing for explaining CORESET.

[0085] Referring to Figure 7, a CORESET can exist in various forms within the carrier bandwidth within a single slot, and in the time domain, a CORESET can consist of up to three OFDM symbols. In addition, a CORESET is defined as a multiple of six resource blocks up to the carrier bandwidth in the frequency domain.

[0086] The first CORESET is indicated via the MIB as part of the initial bandwidth part configuration, allowing the terminal to receive additional configuration and system information from the network. After establishing a connection with the base station, the terminal can receive and configure one or more CORESET information via RRC signaling.

[0087] In this specification, the terms frequency, frame, subframe, resource, resource block, region, band, subband, control channel, data channel, synchronization signal, various reference signals, various signals or various messages related to NR (New Radio) may be interpreted in the past or present meaning or in various meanings used in the future.

[0088] The present disclosure relates to a technique for controlling the operation of a wireless relay based on PDU session backhaul. In particular, a relay integration operation providing PDU session backhaul is proposed.

[0089] Integrated Access and Backhaul (IAB)

[0090] The IAB node enables wireless relaying in NG-RAN. The relaying node, referred to as the IAB-node, supports access and backhauling via NR. The terminating node of NR backhauling on the network side is referred to as the IAB-donor, which represents a gNB with additional functionality to support IAB.

[0091] FIG. 8 and FIG. 9 are drawings illustrating an IAB structure to which the present embodiment can be applied.

[0092] As shown in Fig. 8, the IAB node can support a stand-alone mode. Alternatively, as shown in Fig. 9, the IAB node can also support a non-stand-alone mode. The IAB node supports the gNB-DU functionality, as defined in 3GPP TS 38.401, to terminate the NR access interface (NR Uu) to UEs and next-hop IAB nodes, and to terminate the F1 protocol to the gNB-CU functionality, as defined in TS 38.401, on the IAB-donor. The IAB-node DU can also be referred to as IAB-DU. In addition to the gNB-DU functionality, the IAB-node also supports a subset of the UE functionality referred to as IAB-MT, which includes, e.g., physical layer, layer-2, RRC and NAS functionality to connect to the gNB-DU of another IAB-node or the IAB-donor, to connect to the gNB-CU on the IAB-donor, and to the core network.

[0093] FIG. 10 is a diagram illustrating a parent node and child node relationship for a mobile IAB node according to one embodiment.

[0094] Referring to FIG. 10, a mobile IAB node provides NR access links to UEs and NR backhaul links to parent nodes. Furthermore, the mobile IAB node can perform physical mobility across a wireless network area. The mobile IAB node includes a mobile IAB-MT and a mobile IAB-DU, and supports the same functionality as the IAB, with the exception of some features. (Mobile IAB introduces the mobile IAB-node, which is a RAN node that provides NR access links to UEs and an NR backhaul link to a parent node, and that can conduct physical mobility across the RAN area.) The mobile IAB-node includes a mobile IAB-MT and a mobile IAB-DU. Mobile IAB supports the same functionality as IAB unless explicitly specified.)

[0095] In this way, mobile IAB can support node mobility compared to IAB while providing wireless access and backhaul to base stations. However, mobile IAB nodes can only be supported in limited areas of wireless networks that support a separate base station architecture. This makes it difficult to support diverse use cases, such as wireless access for onboard terminals in aircraft, helicopters, and other devices via onboard gNBs in remote areas with limited sky visibility, backhauling via TN and NTN, and backhauling between the access PLMN and backhaul PLMN.

[0096] In this way, it was difficult to support use cases such as backhauling between different PLMNs through the existing mobile IAB that supports wireless relaying between terminals and base stations.

[0097] The present disclosure proposes a method and device for providing a wireless relay based on a PDU session backhaul. In particular, the present disclosure provides a method and device for integrating a wireless relay based on a PDU session backhaul.

[0098] Hereinafter, a relay provision method based on 5GS / NR technology is described. However, this is for convenience of explanation, and the present disclosure can also be applied through any system / radio access technology (e.g., 6G). This embodiment includes the contents of information elements and operations specified in the NR / 5GS standard (e.g., MAC standard TS 38.321, NR RRC standard TS 38.331, system architecture standard TS 23.501, etc.). Even if the terminal operation contents related to the definition of the corresponding information element are not included in this specification, the corresponding contents specified in the standard may be included in the present disclosure.

[0099] Any of the functions described below are defined as individual terminal capabilities (UE radio capabilities or UE core network capabilities). Any of the functions can be transmitted by the terminal to the base station / core network entity (e.g., AMF / SMF) via signaling. Alternatively, any of the functions can be combined / combined to define the corresponding terminal capabilities and transmitted by the terminal to the base station / core network entity via signaling.

[0100] The base station may transmit / instruct the terminal via an RRC message, indicating whether to allow / support / configure any function or combination of functions described below. For example, this may be instructed to the terminal prior to or concurrently with the configuration / application of the function / combination of functions. This RRC message may be broadcast via system information. Alternatively, it may be instructed to the terminal via a dedicated RRC message.

[0101] The base station may transmit / instruct the terminal via an RRC message information to restrict / control any of the functions described below. For example, the base station may indicate a prohibit timer for the relevant function. The terminal may start / restart the prohibit timer before or upon initiating the relevant function. While the timer is running, the terminal may be restricted / controlled from initiating / executing the relevant function.

[0102] The embodiments and corresponding functions described below can be performed individually and independently. It is apparent that the embodiments and functions described below can be implemented by combining or combining any of the embodiments, and this is also included within the scope of the present disclosure.

[0103] Any information described below may be traffic characteristic information (e.g., expected value / average, deviation, standard deviation minimum, maximum, etc.) statistically / empirically obtained / calculated / derived from a terminal / network. Accordingly, any information included in this specification may represent one or more of the average (expected value), minimum, maximum, and standard deviation values. This is for convenience of explanation, and all information in this specification may be used as statistical information. Alternatively, it may be information pre-configured in the terminal / network or provisioned via OAM / application server / application function / UDM.

[0104] The present disclosure describes specific operations by which a WAB node performs integration.

[0105] In this specification, the term "WAB node" refers to a relay node that provides wireless relay based on PDU session backhaul. This term is used for convenience of explanation and is not limited to this term.

[0106] Furthermore, WAB nodes differ from the aforementioned IAB nodes in terms of the functions they perform. For example, due to their structure, mobile IAB nodes can only support a limited area of ​​wireless networks that support a base station separation structure. Therefore, mobile IAB nodes have difficulty supporting various use cases, such as wireless access to onboard terminals in aircraft, helicopters, etc., via onboard gNBs, backhauling via TN and NTN, and backhauling between the access PLMN and backhaul PLMN. In other words, the existing mobile IAB, which supports wireless relaying between terminals and base stations, has difficulty supporting use cases such as backhauling between different PLMNs.

[0107] To address these issues, the present disclosure describes the operation of a WAB node that provides wireless relay based on PDU session backhaul. Specifically, this embodiment focuses on wireless relay integration technology based on PDU session backhaul. However, the present disclosure is not limited thereto, and various operations of the WAB node are also proposed.

[0108] In this specification, WAB-base station or WAB-gNB refers to a gNB function defined in TS 38.300, which provides an NR access interface to the UE. WAB-MT may refer to a WAB node function that terminates the Uu interface to the BH-RAN node using the procedures and operations specified for the UE. It corresponds to the MWAB-UE function defined in TS 23.501. WAB node: refers to an NG-RAN node that includes WAB-MT and WAB-gNB functions.

[0109] Fig. 11 is a diagram for explaining the operation of a WAB node according to one embodiment.

[0110] Referring to FIG. 11, a method for a WAB (Wireless Access Backhaul) node to perform an integration operation may include a step of performing an operation for setting up a WAB-MT (WAB-Mobile Terminal) of the WAB node by performing an RRC connection setup procedure with a WAB-MT serving base station (S1100).

[0111] As described above, a WAB node is a relay node that provides wireless relay based on PDU session backhaul. For example, a WAB node may include a WAB-base station that provides an NR Uu interface for one or more terminals and a WAB-MT that terminates the NR Uu interface toward a WAB-MT serving base station. The WAB-base station configures an NR Uu interface with one or more terminals that communicate with the WAB node and acts as a base station for the terminals. The WAB-MT connects to the WAB-MT serving base station as a terminal and relays communication between the terminals and the WAB-MT serving base station.

[0112] The WAB node sets up the WAB-MT within the WAB node at step S1100.

[0113] For example, the step (S1100) of performing an operation of setting up WAB-MT may further include a step of performing authentication with a core network entity that provides a service to WAB-MT, and the step of WAB-MT establishing one or more PDU sessions with the core network entity.

[0114] At step S1100, the WAB node can set up the WAB-MT within the WAB node by performing the RRC connection setup procedure with the BH-RAN-Node. Once the WAB-MT is set up, it can perform authentication with the BH-5GC. After the WAB-MT performs authentication, it can establish one or more PDU sessions for backhauling. That is, the aforementioned core network entity can be the backhaul-5GC serving the WAB-MT.

[0115] For example, one or more PDU sessions may be established for backhauling data other than user plane data during the control plane backhaul setup process. One or more PDU sessions may be performed after the WAB node successfully completes authentication with the core network entity that provides services to the WAB-MT.

[0116] For example, one or more PDU sessions can be established between the WAB-MT and the WAB-MT UPF. During the control plane backhaul setup phase (or during WAB node integration), a backhaul can be set up to carry non-user plane data / traffic (non-UP traffic). The control plane backhaul setup can be performed during the WAB-MT setup phase.

[0117] A method for a WAB (Wireless Access Backhaul) node to perform an integration operation may include a step of configuring a WAB-base station (WAB-gNB) of the WAB node by OAM (Operations, administration and management) (S1110).

[0118] For example, a WAB node configures a WAB base station after setting up a WAB-MT. The WAB base station is configured through OAM. For example, a WAB node configures a WAB base station through OAM with information from AMF to serve one or more terminals. The WAB base station is service-authenticated by SeGW through OAM. Through this, a WAB base station is configured in the WAB node.

[0119] The method by which a WAB (Wireless Access Backhaul) node performs an integration operation may include a step in which a WAB-base station of the WAB node performs an NG connection setup operation with a core network entity (S1120).

[0120] Once a WAB base station is configured, the WAB node can perform NG connection setup operations with the core network entity through the WAB base station. Alternatively, the WAB base station can initiate TNL setup between one or more terminal serving AMFs that access or will access the WAB base station.

[0121] Meanwhile, the WAB-base station of the WAB node may further include a step of setting up an Xn interface with the WAB-MT serving base station after the step (S1120) of performing an NG connection setup operation. Here, the WAB-MT serving base station may be co-located with the WAB-base station of the WAB node.

[0122] Through the above operations, the WAB node can integrate the WAB node to set up a WAB-MT within the WAB node and configure a WAB-base station to perform relay operations.

[0123] FIG. 12 is a diagram illustrating the functional structure of a WAB node according to one embodiment.

[0124] Referring to Figure 12, the WAN node is configured with a WAB-gNB (WAB-base station) and a WAB-MT. The WAB-gNB provides a Uu interface to the terminal. The WAB-MT configures an NR Uu interface with the BH-gNB (WAB-MT serving base station) and establishes a BH PDU session with the BH-5GC. The BH PDU session is a PDU session for transmitting NG-C / NG-U interface traffic of the WAB-gNB.

[0125] Additionally, the WAB-gNB establishes an Xn-C / Xn-U over BH PDU session with a neighboring NG-RAN node. The Xn-C / Xn-U over BH PDU session carries the Xn-C / Xn-U interface traffic of the MWAB-gNB through the BH PDU session.

[0126] Additionally, WAB-gNB can also configure 5GC and NG-C / NG-U over BH PDU sessions of the terminal. The NG-C / NG-U over BH PDU sessions forward the NG-C / NG-U interface traffic of WAB-gNB through the BH PDU sessions.

[0127] Below, more diverse embodiments of the operation and structure of the aforementioned WAB are described.

[0128] PDU Session backhaul (backhaul PDU session) provision structure

[0129] Fig. 13 is a diagram illustrating an example of a wireless relay structure according to one embodiment. Fig. 14 is a diagram illustrating another example of a wireless relay structure according to one embodiment.

[0130] Below, the PDU session backhauling method is first described with reference to FIGS. 13 and 14.

[0131] 5GC supports the PDU Connectivity service, which provides PDU exchange between a UE and a data network (DN) identified by a DNN. The PDU connectivity service is supported through a PDU session established upon request from the UE. A PDU session is an association between the UE and a data network that provides a PDU connectivity service. PDU session types can be classified as IPv4, IPv6, IPv4v6, Ethernet, and Unstructured. A PDU session is established at the UE's request using NAS SM (Session Management) signaling exchanged over the N1 interface between the UE and the SMF, and is modified / released upon UE / 5GC request. Upon request from an application server, 5GC can trigger a specific application within the UE. Upon receiving the trigger message, the UE can pass it to the identified application within the UE. The identified application within the UE can establish a PDU session.

[0132] PDU session backhauling can be provided via a wireless relay. Here, PDU session backhauling refers to providing backhaul to terminals that have wireless access to the relay node using a PDU session. For convenience of explanation, this is referred to below as PDU session backhaul or backhaul PDU session. This is for convenience of explanation and may be referred to by any other name.

[0133] Hereinafter, a relay providing PDU session backhaul is referred to as WAB (Wireless Access Backhaul). This is for convenience of explanation and can be replaced with any other name. WAB can be defined as a node supporting NR access and PDU session backhaul. For example, WAB can provide wireless access to a terminal (or terminate a wireless access interface) through WAB-CU / WAB-base station functions. WAB can terminate an N3 interface between the base station (WAB-gNB in ​​FIG. 13 / FIG. 14) and the UPF serving the terminal (UE serving UPF in FIG. 13 / FIG. 14) through WAB-base station / WAB-gNB functions. It can provide wireless access to a terminal (UE in FIG. 13 / FIG. 14) (or terminate a wireless access interface). WAB can provide PDU session backhaul (or terminate PDU session backhaul interface / link) via WAB-MT / WAB-UE function.

[0134] The 5GC (e.g., UE serving AMF, UE serving UPF) / PLMN serving a UE and the 5GC (e.g., WAB-MT serving AMF, WAB-MT serving UPF) / PLMN serving a WAB-MT / WAB-UE co-located with the WAB-base station accessed by the UE may be the same PLMN or different PLMNs.

[0135] For example, a WAB can be deployed within a single operator / PLMN. The UE, WAB, WAB-MT serving base station, WAB-MT serving UPF, and the UE's serving UPF can all be established within the same PLMN. The WAB base station can broadcast a PLMN ID identical to the PLMN ID of the PLMN to which the WAB-MT / WAB-UE is connected.

[0136] As another example, a WAB can be deployed within more than one operator / PLMN. The WAB-MT serving base station, the WAB-MT serving UPF, and the UE's serving UPF can be established through different PLMNs. The WAB base station can broadcast a PLMN ID that differs from the PLMN ID of the PLMN to which the WAB-MT / WAB-UE is connected via wireless access.

[0137] The WAB may service PDU sessions for one or more terminals (e.g., UE PDU session in FIG. 13) via PDU session backhaul (e.g., WAB-MT PDU session backhaul between WAB-MT and WAB serving UPF in FIG. 13).

[0138] For example, a PDU connectivity service can be provided by linking one / each PDU session created for each terminal to a single WAB-MT PDU session. For example, a PDU session of a terminal and a WAB-MT PDU session can be linked through a 1:1 mapping. Through this, a PDU connectivity service can be provided by setting up a linked WAB-MT PDU session that conforms to the QoS rules provided by the 5GC of the terminal for the terminal.

[0139] However, if this is applied, the number of terminals / PDU sessions that can support relaying through WAB may be limited. The maximum number of PDU sessions provided by the current 5G system standard is 15. Therefore, if the existing standard is used, the maximum number of PDU sessions that can support relaying through WAB is 15. If only one PDU session is provided to each terminal, the maximum number of terminals that can support relaying through WAB is 15. To solve this, the maximum number of PDU sessions can be set to 15 or more (e.g., one of 31, 65, 127, and 255) for WAB-MT and core network nodes that support WAB-MT (e.g., WAB-MT support AMF / SMF / UPF).

[0140] The PDU session ID can be distinguished and indicated using bits 1-5, 1-6, 1-7, and 1-8 of the 8-bit PDU session identity field included in the NAS message (e.g. NAS standard L3 message). Alternatively, the maximum number of PDU sessions can be set to 15 or more (e.g. 511 or more) for WAB-MT and core network nodes supporting WAB-MT (e.g. WAB-MT support AMF / SMF / UPF). In addition to the 8-bit PDU session identity field included in the NAS message (e.g. NAS standard L3 message) (or by setting the PDU session identity using bits 5-8 in the PDU session identity field), any field included in the NAS message can be additionally used to distinguish and indicate the PDU session ID.

[0141] As another example, one or more PDU sessions (e.g., the maximum number is M) created for each terminal can be linked to a single WAB-MT PDU session to provide a PDU connectivity service. For example, a PDU session of a terminal and a WAB-MT PDU session can be linked through an M-to-1 mapping. Through this, a WAB-MT PDU session linked to the terminal can be set up to suit the QoS rules provided by the terminal's 5GC, thereby providing a PDU connectivity service.

[0142] As another example, during the PDU session setup / modification of a terminal, the WAB-base station can receive session management context / information for the PDU session of that terminal from the SMF serving that terminal. The SM context may include one or more of the following information: PDU Session ID, QFI(s), QoS Profile(5QI, ARP, etc.), CN Tunnel information(transport layer information(IP address, GTP-TEID) of terminal-serving UPF), S-NSSAI, N1 SM container (PDU Session Establishment Accept ([QoS Rule(s) and QoS Flow level QoS parameters]) transmitted to the terminal. Here, the QoS Rule includes QFI of the QoS flow, packet filter set (e.g., Source / destination IP address or IPv6 prefix, Source / destination port number, Protocol ID of the protocol above IP / Next header type, TOS, etc.), precedence value. Through this, the UE can extract the IP address, port number, protocol ID, and TOS for the QoS flow transmitted and received by the UE. The UE-serving UPF establishes an N3 tunnel with the WAB-base station. The UE-serving UPF The WAB base station can receive transport layer information (IP address, GTP-TEID). The WAB node can know GTP-U tunnel information (Source / destination IP address, Source / destination port number, Protocol ID) between the WAB base station and the UE serving UPF.The WAB base station can set up / modify the PDU session of the WAB-MT to map the PDU session of the corresponding terminal to the PDU session (PDU session backhaul) of the WAB-MT (to map the QoS flow(s) included in the PDU session of the corresponding terminal to the QoS flow(s) included in the PDU session of the WAB-MT).

[0143] The WAB-MT may include one or more pieces of information among a PDU session ID, a packet filter, and a QFI in a NAS message for establishing a PDU session (or the WAB-MT may include one or more pieces of information among a PDU session ID, a packet filter, and a QFI in a NAS message for modifying a PDU session). The packet filter may include GTP-U tunnel information (Source / destination IP address, Source / destination port number, Protocol ID) between the WAB-base station and the UE serving UPF. Through this, the WAB-base station may map the PDU session of the corresponding UE to the PDU session of the WAB-MT (PDU session backhaul, backhaul PDU session) (map QoS flow(s) included in the PDU session of the corresponding UE to QoS flow(s) included in the PDU session of the WAB-MT).

[0144] WAB-MT can receive N1 SM container (PDU Session Establishment Accept ([QoS Rule(s) and QoS Flow level QoS parameters])) during PDU session setup / modification of WAB-MT. WAB can extract IP address, port number, protocol ID, TOS for QoS flow transmitted / received by WAB-MT through PDU session backhaul. Information about the corresponding QoS flows can be information set based on GTP-U tunnel information between WAB-base station and UE serving UPF.

[0145] WAB Node Integration / Setup / Configuration Procedure

[0146] To provide wireless relaying based on PDU session backhaul, wireless relay integration / setup / configuration based on PDU session backhaul must be performed. For this purpose, integration / setup / configuration procedures for WAB nodes need to be defined.

[0147] After the integration / setup / configuration procedure for the WAB node, services to the terminal (e.g. wireless relaying, relaying via PDU session backhaul) can be initiated through the WAB node.

[0148] The integrated procedure for a WAB node may consist of one or more of the steps of WAB-MT setup, control plane data / traffic link / session / channel / tunnel / backhaul setup / configuration, and WAB-base station setup. Here, control plane data / traffic link / session / channel / tunnel / backhaul setup / configuration may represent the step of setting up / establishing a link / session / channel / tunnel / backhaul for carrying data / traffic other than user plane data / traffic to and / or from the WAB / WAB node / WAB-MT / WAB-base station. This is for convenience of explanation and may be changed to any other name (e.g., backhaul PDU session setup, default backhaul PDU session setup, backhaul link / interface setup, default backhaul link / interface setup).

[0149] For example, in the WAB-MT setup phase, the WAB-MT of a WAB node can connect to the network in a similar / identical manner to a terminal. The WAB-MT can perform an RRC connection setup / establishment procedure with the WAB-MT serving base station. The WAB-MT can perform authentication with the core network. The core network can set up / establish a terminal context for the WAB-MT with the base station that the WAB-MT wirelessly accesses (referred to as the WAB-MT serving base station for convenience of explanation). A radio bearer can be added / set up / configured between the WAB-MT and the WAB-MT serving base station. One or more PDU sessions can be established between the WAB-MT and the WAB-MT UPF. OAM connectivity / connection can be established using the PDU sessions of the WAB-MT.

[0150] In this way, the WAB-MT setup step may perform one or more of the following operations: setup / establishment of an RRC connection with the WAB-MT serving base station, core network authentication / authorization / authorization, terminal context setup in the core network and / or the WAB-MT serving base station, addition / setup / configuration of a radio bearer between the WAB-MT and the WAB-MT serving base station, establishment of a PDU session of the WAB-MT, and establishment of OAM connectivity / connection of the WAB-MT.

[0151] As another example, during the control plane data / traffic link / session / channel / tunnel / backhaul setup / establishment phase (or during WAB node integration), a link / session / channel / tunnel / backhaul may be setup / established to carry non-user plane data / traffic (non-UP traffic). The link / session / channel / tunnel / backhaul may be setup / established as the default link / session / channel / tunnel / backhaul to carry non-user plane data / traffic (non-UP traffic). The default link / session / channel / tunnel / backhaul can carry N2 / NGAP traffic between the WAB-base station and the core network (e.g. UE serving AMF) of the UE (accessing the WAB-base station) [or non-N3 user plane data traffic between the WAB-base station and the UPF of the UE (accessing the WAB-base station)].

[0152] As another example, the default link / session / channel / tunnel / backhaul can be provided using a specific PDU session (or a specific backhaul PDU session) between the WAB-MT and the WAB-MT UPF. For this purpose, the PDU session setup procedure of the WAB-MT can be performed. Indication information for this can be defined and included in the setup request / confirmation message of the procedure. For example, information indicating whether the default PDU session backhaul is performed can be defined. Alternatively, for the default PDU session backhaul, a specific value can be defined for any PDU session sub-parameter (PDU session ID, S-NSSAI, UE aggregate maximum bit rate, UE slice maximum bit rate list, QFI, QoS flow level QoS parameter (5QI, Allocation and Retention Priority, GBR QoS Flow Information), UP TNL information) and the corresponding value can be set for the corresponding parameter to distinguish it.

[0153] As another example, the default link / session / channel / tunnel / backhaul can be provided by modifying the pre-established PDU session (or existing backhaul PDU session) between the WAB-MT and the WAB-MT UPF. To this end, the PDU session modification procedure of the WAB-MT can be performed. Instructions for this can be defined and included in the modification request / confirmation message for the procedure.

[0154] As another example, the default link / session / channel / tunnel / backhaul can be established between the WAB / WAB-node / WAB-MT / WAB-base station and the AMF (e.g. UE serving AMF) serving the UE that accesses / will access the WAB-base station, if the AMF is a WAB-supporting AMF.

[0155] As another example, the default link / session / channel / tunnel / backhaul can be established between the WAB / WAB node / WAB-MT / WAB-base station and the AMF serving the WAB-MT (e.g., WAB-MT serving AMF), if the AMF is a WAB-supporting AMF.

[0156] As another example, the default link / session / channel / tunnel / backhaul may be established between the WAB / WAB-base station / WAB-MT and any gateway (e.g. Security gateway, UPF: user plane function) for connecting to the AMF serving the UE accessing / will accessing the WAB-base station. For example, a security gateway may be provided between the UPF of the WAB-MT and the core network of the UE accessing / will accessing the WAB-base station. In such a case, the step of establishing a security tunnel (based on security credentials) between the WAB / WAB-base station / WAB-MT and the security gateway may be included.

[0157] As another example, the control plane data / traffic link / session / channel / tunnel / backhaul setup / establishment step may include one or more of TNL setup between the WAB-base station and the AMF of the terminal accessing / to access the WAB-base station, NG setup (N2 interface setup) setup.

[0158] As another example, for TNL configuration, the WAB base station can exchange control plane transport layer information (e.g., WAB base station CP transport layer information, AMF CP transport layer information) with the terminal serving AMF. The control plane transport layer information can include one or more of the endpoint IP address and port number.

[0159] As another example, the control plane data / traffic link / session / channel / tunnel / backhaul setup / establishment step may include one or more of TNL information exchange / configuration / establishment for a security gateway to connect to the AMF of a terminal accessing / to access the WAB-base station, security parameter exchange / configuration / establishment, and security tunnel establishment.

[0160] As another example, in the WAB-base station setup phase, the WAB-base station of the WAB node may be configured via OAM. As another example, in the WAB-base station setup phase, the WAB-base station of the WAB node may perform one or more of N3 setup / configuration between the WAB-base station and the UPF of the terminal that will access / will access the WAB-base station, TNL setup, and backhaul PDU session setup / modification between the WAB-base station and the UPF of the terminal that will access / will access the WAB-base station.

[0161] As another example, during the WAB-base station setup phase, the WAB-base station can initiate TNL setup, NG setup (N2 interface setup) between the WAB-base station and the terminal serving AMF that accesses / will access the WAB-base station.

[0162] As another example, during the WAB base station setup phase, the WAB base station may exchange control plane transport layer information (e.g., WAB base station CP transport layer information, AMF CP transport layer information) with the terminal serving AMF to configure TNL. The control plane transport layer information may include one or more of the endpoint IP address and port number.

[0163] As another example, you can use the default link / session / channel / tunnel / backhaul set for TNL configuration.

[0164] As another example, during NG setup, the WAB-base station may include in the NG setup request message one or more of the following information: identifier of the co-located WAB-MT (e.g. AMF UE NGAP ID, IP-address, S-TMSI, C-RNTI, control plane transport layer information, ...), identifier of the WAB-base station (e.g. gNB-ID, global gNB ID, AMF UE NGAP ID, control plane transport layer information, ...), identifier of the WAB-MT serving base station (e.g. gNB-ID, control plane transport layer information), WAB-MT serving UPF identifier, UE serving AMF identifier (e.g. GUAMI (PLMN ID, AMF region ID, AMF Set ID, AMF Pointer), identifier of any gateway (e.g. security gateway, user plane function) to connect to the AMF (or control plane transport layer information). The UE serving AMF may include one or more of the following information: identifier of the co-located WAB-MT (e.g. AMF UE NGAP ID, IP-address, S-TMSI, The NG Setup response message may include one or more of the following information: C-RNTI, control plane transport layer information, ...), identifier of WAB-base station (e.g. gNB-ID, global gNB ID, AMF UE NGAP ID, control plane transport layer information, ...), WAB-MT serving base station identifier (e.g. gNB-ID, control plane transport layer information), WAB-MT serving UPF identifier, UE serving AMF identifier (e.g. GUAMI (PLMN ID, AMF region ID, AMF Set ID, AMF Pointer), identifier of any gateway (e.g. security gateway, user plane function) for connecting to AMF (or control plane transport layer information).An AMF that supports WAB may include information indicating that the AMF supports WAB (e.g., WAB-supported). The NG Setup response message may include information indicating that the AMF supports WAB (e.g., WAB-supported). If the NG Setup response message includes such information, the WAB-base station may store the information and allow the WAB-MT to use it for AMF selection.

[0165] As another example, after NG setup and / or backhaul PDU session establishment / modification, the WAB node can start serving the terminal (accessing the WAB base station).

[0166] As another example, the NG setup phase may be included in the control plane data / traffic link / session / channel / tunnel / backhaul setup / establishment phase.

[0167] As another example, control plane data / traffic link / session / channel / tunnel / backhaul setup / configuration may be included in either the WAB-MT setup phase or the WAB-base station setup phase.

[0168] As another example, during the integration / setup / configuration procedure for the WAB node (or during one of the WAB-MT setup phase, the control plane data / traffic link / session / channel / tunnel / backhaul setup / establishment phase, and the WAB-base station setup phase), a signaling radio bearer may be added / configured between the WAB-MT and the WAB-MT serving base station for backhauling / relaying the control plane data of the UE that accesses / will access the WAB-base station. The WAB node may receive control plane data (e.g. NAS messages) from the UE that wirelessly accesses the WAB-base station. The WAB node may transmit the corresponding control plane message to the AMF of the UE (e.g. UE serving AMF). The corresponding control plane message may be transmitted via the NG / N2 interface (NGAP message) between the WAB-base station and the UE serving AMF. The physical path along which the control plane message is actually transmitted and received may be WAB-Base Station == WAB-MT == WAB-MT Serving Base Station == WAB-MT Serving UPF == UE Serving AMF. The control plane data may be provided with QoS processing that is distinct from user plane data.

[0169] As another example, control plane data (e.g., NAS messages) received from a terminal accessing the WAB base station wirelessly via the default link / session / channel / tunnel / backhaul can be transmitted. A default signaling radio bearer, a default logical channel, and a default RLC channel can be configured between the WAB-MT and the WAB-MT serving base station, which are mapped / associated with the default link / session / channel / tunnel / backhaul.

[0170] As another example, control plane data (e.g., NAS messages) received from a terminal accessing the WAB base station wirelessly via a default link / session / channel / tunnel / backhaul can be transmitted. A default data radio bearer, a default logical channel, and a default RLC channel can be configured between the WAB-MT and the WAB-MT serving base station, which are mapped / associated with the default link / session / channel / tunnel / backhaul. This allows the WAB node to transmit the corresponding control plane message via a specific data radio bearer.

[0171] As another example, control plane data (e.g., NAS messages) received from a terminal accessing a WAB base station wirelessly can be forwarded via a signaling radio bearer for backhauling / relaying between the WAB-MT and the WAB-MT serving base station. The WAB-MT serving base station can map the radio bearer to a specific QoS flow and transmit it to the WAB-MT UPF. To provide this function, one or more of a default / specific signaling radio bearer, an NG tunnel, and a QoS flow (or QFI) can be defined.

[0172] As another example, the default link / session / channel / tunnel / backhaul for transmitting control plane data (e.g. NAS messages) received from terminals accessing the WAB base station wirelessly can be mapped / associated with the default signaling radio bearer, default NG tunnel, and default QoS flow.

[0173] As another example, control plane data (e.g., NAS messages) received from a terminal accessing a WAB base station wirelessly can be forwarded via a data radio bearer for backhauling / relaying between the WAB-MT and the WAB-MT serving base station. The WAB-MT serving base station can map the radio bearer to a specific QoS flow and transmit it to the WAB-MT UPF. To provide this function, one or more of a default / specific data radio bearer, an NG tunnel, and a QoS flow (or QFI) can be defined.

[0174] As another example, the default link / session / channel / tunnel / backhaul for transmitting control plane data (e.g. NAS messages) received from terminals accessing the WAB base station wirelessly can be mapped / associated with the default data radio bearer, default NG tunnel, and default QoS flow.

[0175] As another example, when a terminal accesses a WAB base station and sets up / modifies a PDU session for the terminal, the WAB / WAB node / WAB-MT / WAB base station can perform relaying by mapping / linking the user data of the terminal accessing the WAB base station to a PDU session backhaul (or backhaul PDU session).

[0176] As another example, the backhaul PDU session mapping for user data of a terminal accessing a WAB-base station may be included in one of the steps of WAB-MT setup, control plane data / traffic link / session / channel / tunnel / backhaul setup / configuration, or WAB-base station setup, which are included in the integrated procedure for the WAB node. For example, it may be included in WAB-base station setup.

[0177] As another example, PDU session backhaul mapping / association for user data of terminals accessing WAB-base station can be included in the integrated procedure for WAB node as a separate step from WAB-MT setup, control plane data / traffic link / session / channel / tunnel / backhaul setup / configuration, and WAB-base station setup.

[0178] As another example, a radio bearer for backhauling / relaying can be added / configured between the WAB-MT and the WAB-MT serving base station. The WAB node can receive user plane data from a terminal that wirelessly accesses the WAB-base station. The WAB node can transmit the user plane data to the UPF (e.g., UE serving UPF) of the terminal. The user data can be transmitted through the N3 interface (GTP-U) between the WAB-base station and the UPF of the terminal. The physical path along which the user data is actually transmitted and received can be WAB-base station == WAB-MT == WAB-MT serving base station == WAB-MT serving UPF == UE serving UPF. The user plane data can be QoS-processed according to the characteristics of the user plane data.

[0179] User plane data received from a terminal accessing a WAB base station wirelessly can be forwarded via a data radio bearer for backhauling / relaying between the WAB-MT and the WAB-MT serving base station. The WAB-MT serving base station can map the radio bearer to an appropriate QoS flow and transmit it to the WAB-MT UPF.

[0180] During the PDU session setup / modification procedure of a terminal accessing a WAB base station, the WAB base station can receive PDU session resource setup / modification request information from the AMF (UE serving AMF) of the terminal. The PDU session resource setup / modification request information includes PDU session ID, S-NSSAI, UE aggregate maximum bit rate, UE slice maximum bit rate list, QFI, QoS flow level QoS parameters (5QI, Allocation and Retention Priority, GBR QoS Flow Information), UP TNL information, etc.

[0181] If there is a PDU session backhaul to be mapped / associated based on one or more pieces of information included in a PDU session resource setup / modification request of a terminal accessing the WAB-base station received by the WAB-base station, the WAB-base station can map / associate the PDU session of the terminal to the PDU session backhaul. Otherwise, the WAB-MT can establish / modify a PDU session (or PDU session backhaul) through the PDU session establishment / modification procedure. The WAB-base station can map / associate the PDU session of the terminal to the PDU session backhaul.

[0182] A PDU session (or PDU session backhaul), data radio bearer, NG tunnel, and QoS flow (or QFI) for QoS flow backhauling / relaying can be established / modified based on one or more pieces of information included in a PDU session resource setup / modification request of a terminal accessing a WAB-base station received by the WAB-base station through the PDU session setup / modification procedure of the WAB-MT.

[0183] As another example, OAM connectivity setup can be performed using the PDU session of WAB-MT. WAB-MT can select a WAB-MT serving base station based on indication information (e.g., WAB support indication information) received via system information. To indicate WAB capabilities, WAB-MT can include WAB-node indication information in the RRCSetupComplete message. This can help the WAB-MT serving base station select a WAB-supporting AMF.

[0184] Additional embodiments according to the present disclosure are described below. The following embodiments may be combined in any combination with the embodiments described above.

[0185] The cell coverage provided by the WAB-MT serving base station accessed by the WAB / WAB-MT co-located with the WAB base station may be greater than the cell coverage provided by the WAB base station. As the terminal accessing the WAB base station moves, a handover from the WAB base station cell to the WAB-MT serving base station cell may be provided for the terminal.

[0186] For example, an Xn interface may be set up / established between a WAB-base station and a WAB / WAB-MT serving base station co-located with the WAB-base station during the integration / setup / establishment procedure for the WAB node (or at one of the steps of WAB-MT setup, PDU session backhaul (or backhaul PDU session, or backhaul link) setup, or WAB-base station setup included in the integration / setup / establishment procedure for the WAB node).

[0187] An Xn interface can be set up / configured between a WAB-base station and a WAB / WAB-MT serving base station co-located with the WAB-base station.

[0188] As another example, the Xn setup procedure can be initiated by the WAB base station. The WAB base station can send an Xn setup request message to the WAB-MT serving base station accessed by the WAB / WAB-MT co-located with the WAB base station. The WAB base station can receive an Xn setup response message from the WAB-MT serving base station accessed by the WAB / WAB-MT co-located with the WAB base station.

[0189] If the WAB-MT serving base station cannot accept the setup, the WAB-MT serving base station can respond with an Xn Setp failure message with an appropriate cause value.

[0190] As another example, the Xn setup procedure can be initiated by a WAB-MT serving base station accessed by a WAB / WAB-MT co-located with the WAB-base station. The WAB-MT serving base station accessed by the WAB / WAB-MT co-located with the WAB-base station can transmit an Xn setup request message to the WAB-base station. The WAB-MT serving base station accessed by the WAB / WAB-MT co-located with the WAB-base station can receive an Xn setup response message from the WAB-base station.

[0191] If the WAB-base station cannot accept the setup, the WAB-base station can respond with an Xn Setp failure message with an appropriate cause value.

[0192] As another example, the Xn setup request message and / or the Xn setup response message may include information to indicate that the corresponding Xn setup is an Xn setup for a WAB-supporting cell. Or, the cell provided by the corresponding base station may include WAB-supporting indication information.

[0193] As another example, the Xn setup procedure may be included in one of the steps of the WAB-MT setup, control plane data / traffic link / session / channel / tunnel / backhaul setup / establishment, and WAB-base station setup, which are included in the integrated procedure for the WAB node.

[0194] A WAB / WAB node / WAB-base station / WAB-MT can reduce uplink scheduling delay by proactively signaling uplink scheduling requests and / or BSRs of terminals accessing the WAB / WAB node / WAB-base station as a WAB-MT serving base station.

[0195] For example, a WAB-MT serving base station can be defined as a WAB parent node for WAB / WAB node / WAB-base station / WAB-MT.

[0196] As another example, the WAB / WAB node / WAB-base station may transmit a pre-emptive BSR to the WAB-MT serving base station based on the SR / BSR received from the terminal(s) accessing the WAB / WAB node / WAB-base station and / or the uplink grant provided to the terminal(s).

[0197] As another example, in WAB / WAB node / WAB-base station / WAB-MT, preemptive BSR can be triggered when an uplink grant is provided to a terminal by the WAB-base station and / or when the WAB-base station receives a BSR from a terminal. The mapping / association between the logical channels / logical channel groups included in the BSR received by the WAB-base station and the logical channels / logical channel groups included in the preemptive BSR transmitted by the WAB-MT can be utilized, for example, by the WAB / WAB node / WAB-base station / WAB-MT considering the corresponding QoS rule, QoS profile, and QoS parameter during the backhaul PDU session setup / modification process.

[0198] As another example, a preemptive BSR may transmit the total amount of data expected to reach a WAB-MT co-located to that WAB / WAB node / WAB-base station when the preemptive BSR is triggered, in the buffer size per that logical channel group.

[0199] As another example, a preemptive BSR can be transmitted by mapping the logical channel group-specific buffer size of the BSR received by the WAB / WAB node / WAB-base station when the preemptive BSR is triggered to the logical channel group-specific buffer size to be transmitted by the co-located WAB-MT.

[0200] As described above, the present disclosure can effectively provide relay integration for wireless relaying based on PDU session backhaul.

[0201] Fig. 15 is a diagram showing the configuration of a WAB node according to another embodiment.

[0202] Referring to FIG. 15, a WAB (Wireless Access Backhaul) node (1500) performing an integration operation may perform an operation of setting up a WAB-MT (WAB-Mobile Terminal) of the WAB node by performing an RRC connection setup procedure with a WAB-MT serving base station, configure a WAB-base station (WAB-gNB) of the WAB node by OAM (Operations, administration and management), and may include a control unit (1510) in which the WAB-base station of the WAB node performs an NG connection setup operation with a core network entity, a receiving unit (1530) for receiving signals from the WAB-MT serving base station, terminals and core network entities, and a transmitting unit (1520) for transmitting signals to the WAB-MT serving base station, terminals and core network entities.

[0203] A WAB node is a relay node that provides wireless relay based on PDU session backhaul. For example, a WAB node may include a WAB-base station that provides an NR Uu interface to one or more terminals and a WAB-MT that terminates the NR Uu interface toward a WAB-MT serving base station. The WAB-base station configures an NR Uu interface with one or more terminals that communicate with the WAB node and acts as a base station for the terminals. The WAB-MT connects to the WAB-MT serving base station as a terminal and relays communication between the terminals and the WAB-MT serving base station.

[0204] The control unit (1510) sets up the WAB-MT within the WAB node.

[0205] For example, the control unit (1510) performs authentication with a core network entity that provides services to WAB-MT, and WAB-MT can establish one or more PDU sessions with the core network entity.

[0206] The control unit (1510) can set up the WAB-MT within the WAB node by performing an RRC connection setup procedure with the BH-RAN-Node. Once the WAB-MT is set up, the control unit (1510) can perform authentication with the BH-5GC. After the WAB-MT performs authentication, the WAB-MT can establish one or more PDU sessions for backhauling. That is, the aforementioned core network entity can be the backhaul-5GC serving the WAB-MT.

[0207] For example, one or more PDU sessions may be established for backhauling data other than user plane data during the control plane backhaul setup process. One or more PDU sessions may be performed after the WAB node successfully completes authentication with the core network entity that provides services to the WAB-MT.

[0208] For example, one or more PDU sessions can be established between the WAB-MT and the WAB-MT UPF. During the control plane backhaul setup phase (or during WAB node integration), a backhaul can be set up to carry non-user plane data / traffic (non-UP traffic). The control plane backhaul setup can be performed during the process of setting up the WAB-MT.

[0209] The control unit (1510) configures the WAB base station after setting up the WAB-MT. The WAB base station is configured through OAM. For example, the control unit (1510) configures the WAB base station through OAM with AMF information to provide service to one or more terminals. The WAB base station is service-authenticated by the SeGW through OAM. Through this, the WAB base station is configured in the WAB node.

[0210] When a WAB base station is configured, the control unit (1510) can perform a core network entity and NG connection setup operation through the WAB base station. Alternatively, the WAB base station can initiate TNL setup between one or more terminal serving AMFs that access or will access the WAB base station.

[0211] Meanwhile, the control unit (1510) can set up the WAB-MT serving base station and the Xn interface after performing the NG connection setup operation. That is, the control unit (1510) can perform the NG connection setup operation and set up the WAB-MT serving base station and the Xn interface. Here, the WAB-MT serving base station may be co-located with the WAB-base station of the WAB node.

[0212] Through the above operations, the WAB node can integrate the WAB node to set up a WAB-MT within the WAB node and configure a WAB-base station to perform relay operations.

[0213] In addition, the control unit (1510) controls the overall operation of the WAB node (1500) according to the wireless relay operation required to perform the aforementioned embodiment.

[0214] The transmitter (1520) and receiver (1530) are used to transmit and receive signals, messages, and data necessary to perform the aforementioned embodiment with a terminal, a serving base station, and a core network entity.

[0215] The above-described embodiments may be supported by standard documents disclosed in at least one of the wireless access systems, IEEE 802, 3GPP, and 3GPP2. That is, steps, components, and parts not described in the present embodiments to clearly illustrate the technical concepts herein may be supported by the above-described standard documents. Furthermore, all terms disclosed in this specification may be explained by the above-described standard documents.

[0216] The embodiments described above may be implemented through various means. For example, the embodiments may be implemented through hardware, firmware, software, or a combination thereof.

[0217] In the case of hardware implementation, the method according to the present embodiments may be implemented by one or more ASICs (Application Specific Integrated Circuits), DSPs (Digital Signal Processors), DSPDs (Digital Signal Processing Devices), PLDs (Programmable Logic Devices), FPGAs (Field Programmable Gate Arrays), processors, controllers, microcontrollers, or microprocessors.

[0218] When implemented using firmware or software, the methods according to the present embodiments may be implemented in the form of devices, procedures, or functions that perform the functions or operations described above. The software code may be stored in a memory unit and executed by a processor. The memory unit may be located within or outside the processor and may exchange data with the processor using various known means.

[0219] Additionally, terms such as "system," "processor," "controller," "component," "module," "interface," "model," or "unit" as described above may generally refer to a computer-related entity, such as hardware, a combination of hardware and software, software, or software in execution. For example, the aforementioned components may be, but are not limited to, a process driven by a processor, a processor, a controller, a control processor, an object, a thread of execution, a program, and / or a computer. For example, both an application running on a controller or a processor and the controller or the processor may be components. One or more components may be within a process and / or thread of execution, and the components may be located on a single device (e.g., a system, a computing device, etc.) or distributed across two or more devices.

[0220] The above description is merely an illustrative example of the technical idea of ​​the present disclosure, and those skilled in the art to which the present disclosure pertains will appreciate that various modifications and variations can be made without departing from the essential characteristics of the technical idea of ​​the present disclosure. In addition, the present embodiments are not intended to limit the technical idea of ​​the present disclosure but rather to explain it, and therefore the scope of the technical idea of ​​the present disclosure is not limited by these embodiments. The scope of protection of the present disclosure should be interpreted by the claims below, and all technical ideas within a scope equivalent thereto should be interpreted as being included within the scope of the rights of the present disclosure.

[0221]

[0222] CROSS-REFERENCE TO RELATED APPLICATION

[0223] This patent application claims priority under 35 USC §119(a) to Korean Patent Application No. 10-2024-0040700, filed in Korea on March 25, 2024, and Korean Patent Application No. 10-2025-0037031, filed in Korea on March 24, 2025, the entire contents of which are incorporated herein by reference. In addition, this patent application claims priority in countries other than the United States for the same reasons, the entire contents of which are incorporated herein by reference.

Claims

1. In the method in which the WAB (Wireless Access Backhaul) node performs integration operation, A step of performing an operation of setting up a WAB-MT (WAB-Mobile Terminal) of a WAB node by performing an RRC connection setup procedure with a WAB-MT serving base station; A step of configuring the WAB-base station (WAB-gNB) of the above WAB node by OAM (Operations, administration and management); and A method comprising a step of the WAB base station of the above WAB node performing an NG connection setup operation with a core network entity.

2. In paragraph 1, The above WAB node is, A method for providing wireless relay based on PDU session backhaul, which is a relay node.

3. In paragraph 1, The above WAB node is, A method comprising: a WAB-base station providing an NR Uu interface for one or more terminals; and a WAB-MT terminating an NR Uu interface toward the WAB-MT serving base station.

4. In paragraph 1, The steps for performing the above WAB-MT setup operation are: A method for performing authentication with a core network entity that provides services to the WAB-MT, and for the WAB-MT to establish one or more PDU sessions with the core network entity.

5. In paragraph 4, One or more of the above PDU sessions, A method set up for backhauling that carries data excluding user plane data during the control plane backhaul setup process.

6. In paragraph 4, One or more of the above PDU sessions, A method performed after the above WAB node successfully completes authentication with a core network entity providing services to WAB-MT.

7. In paragraph 1, The WAB base station of the above WAB node is, A method further comprising, after the step of performing the above NG connection setup operation, the step of setting up the WAB-MT serving base station and the Xn interface.

8. In paragraph 7, The above WAB-MT serving base station is, A method of co-locating the above WAB node with the above WAB base station.

9. In the WAB (Wireless Access Backhaul) node performing integration operations, A control unit that performs an operation of setting up a WAB-MT (WAB-Mobile Terminal) of a WAB node by performing an RRC connection setup procedure with a WAB-MT serving base station, configures a WAB-base station (WAB-gNB) of the WAB node by OAM (Operations, administration and management), and causes the WAB-base station of the WAB node to perform an NG connection setup operation with a core network entity; A receiving unit that receives signals from the WAB-MT serving base station, terminal, and core network entity; and A WAB node including a transmitter for transmitting a signal to the WAB-MT serving base station, terminal, and core network entity.

10. In paragraph 9, The above WAB node is, WAB node, a relay node that provides wireless relay based on PDU Session backhaul.

11. In paragraph 9, The above WAB node is, A WAB node comprising the WAB-base station providing an NR Uu interface for one or more terminals and the WAB-MT terminating an NR Uu interface toward the WAB-MT serving base station.

12. In paragraph 9, The above control unit, A WAB node that performs authentication with a core network entity that provides services to the WAB-MT, and sets up the WAB-MT by establishing one or more PDU sessions with the core network entity.

13. In paragraph 12, One or more of the above PDU sessions, A WAB node set up for backhauling that carries data excluding user plane data during the control plane backhaul setup process.

14. In paragraph 12, The above control unit, A WAB node that establishes one or more PDU sessions after the WAB node successfully completes authentication with a core network entity that provides services to WAB-MT.

15. In paragraph 9, The above control unit, A WAB node that performs the above NG connection setup operation and sets up an Xn interface with the WAB-MT serving base station.

16. The above WAB-MT serving base station, A WAB node co-located with the WAB base station of the above WAB node.

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