Method and apparatus for releasing PC5 relay radio link control channel

Abstract

A method and apparatus for releasing a PC5 relay radio link control channel. In an embodiment, a relay user equipment establishes first and second PC5 radio resource control connections with first and second remote user equipment. The relay user equipment transmits a configuration of a first PC5 relay radio link control channel associated with an end-to-end side link data radio bearer established between the first remote user equipment and a second remote user equipment to the first remote user equipment. In addition, the relay user equipment receives a destination identity of the second remote user equipment from the first remote user equipment to indicate that the end-to-end PC5 connection is released or failed. If there is no other end-to-end sidelink data radio bearer associated with the first PC5 relay radio link control channel, the relay user equipment transmits a first list of sidelink radio link control channels to be released to the first remote user equipment, the first list containing an identity of the first PC5 relay radio link control channel.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 567,044, filed on March 19, 2024, the entire disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates generally to wireless communication networks, and more particularly, to methods and apparatus for releasing a PC5 relay Radio Link Control (RLC) channel configured to a remote User Equipment (UE) in a wireless communication system. Background Art

[0004] With the rapidly growing demand for transferring large amounts of data to and from mobile communication devices, traditional mobile voice communication networks have evolved into networks that use Internet Protocol (IP) data packets. This IP packet communication can provide IP-based voice, multimedia, multicast, and on-demand communication services to users of mobile communication devices.

[0005] An exemplary network architecture is the Evolved Universal Terrestrial Radio Access Network (E-UTRAN). The E-UTRAN system can provide high data throughput to enable the aforementioned IP-based voice and multimedia services. Currently, the 3GPP standards organization is discussing new radio technologies for the next generation (e.g., 5G). Consequently, changes to the current body of 3GPP standards are currently being submitted and considered to evolve and complete the 3GPP standards. Summary of the Invention

[0006] A method and apparatus for relaying user equipment (UE) are disclosed. In one embodiment, the relay UE establishes a first PC5 radio resource control (RRC) connection with a first remote UE. The relay UE further establishes a second PC5 RRC connection with a second remote UE. The relay UE also transmits a first RRC reconfiguration sidelink message to the first remote UE, wherein the first RRC reconfiguration sidelink message includes a configuration of a first PC5 relay radio link control (RLC) channel associated with at least one end-to-end sidelink data radio bearer (DRB) established between the first remote UE and the second remote UE. In addition, the relay UE receives a PC5 RRC message from the first remote UE, wherein the PC5 RRC message includes a destination identity of the second remote UE to indicate an end-to-end PC5 connection release or failure. In addition, if there are no other end-to-end sidelink DRBs associated with the first PC5 relay RLC channel, the relay UE transmits a second RRC reconfiguration sidelink message to the first remote UE, wherein the second RRC reconfiguration sidelink message includes a first list of sidelink RLC channels to be released, and the first list includes the identity of the first PC5 relay RLC channel. The relay UE also releases the first PC5 relay RLC channel after receiving a first RRC reconfiguration complete sidelink message from the first remote UE. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 The drawing shows a wireless communication system according to an exemplary embodiment.

[0008] Figure 2 is a block diagram of a transmitter system (also referred to as an access network) and a receiver system (also referred to as a user equipment or UE) according to an exemplary embodiment.

[0009] Figure 3 is a functional block diagram of a communication system according to an exemplary embodiment.

[0010] Figure 4 According to an exemplary embodiment Figure 3 Functional block diagram of the program code.

[0011] Figure 5 This is a reproduction of Figure 16.12.2.2-1 of 3GPP TS 38.300 V18.0.0.

[0012] Figure 6 This is a reproduction of Figure 16.12.2.2-2 of 3GPP TS 38.300 V18.0.0.

[0013] Figure 7 This is a reproduction of Figure 16.12.7-1 of 3GPP TS 38.300 V18.0.0.

[0014] Figure 8 It is 3GPP R2-2402042 Figure 5 .8.9.1.1-1 reappearance.

[0015] Figure 9 It is 3GPP R2-2402042 Figure 5 .8.9.8.1-1 reappearance.

[0016] Figure 10 It is 3GPP R2-2402042 Figure 5 .8.9.8.1-1 reappearance.

[0017] Figure 11 A PC5 RRC connection for inter-UE relay according to an exemplary embodiment is shown.

[0018] Figure 12 It is shown that a plurality of source remote UEs communicate with a plurality of target remote UEs via a relay UE according to an exemplary embodiment.

[0019] Figure 13 An end-to-end PC5 connection release or failure is shown according to an exemplary embodiment.

[0020] Figure 14 is a flow chart according to an exemplary embodiment. DETAILED DESCRIPTION

[0021] The exemplary wireless communication systems and devices described below employ wireless communication systems that support broadcast services. Wireless communication systems are widely deployed to provide various types of communications, such as voice, data, etc. These systems can be based on code division multiple access (CDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), 3GPP Long Term Evolution (LTE) radio access, 3GPP Long Term Evolution Advanced (LTE-A), 3GPP2 Ultra Mobile Broadband (UMB), WiMax, 3GPP New Radio (NR), or some other modulation technology.

[0022] In particular, the exemplary wireless communication systems and devices described below may be designed to support one or more standards, such as those provided by a consortium named “3rd Generation Partnership Project,” referred to herein as 3GPP, including: TS 38.300 V18.0.0, “NR; NR and NG-RAN Overall Description; Stage 2 (Release 18)”; R2-2402042, “RRC Calibration for Rel-18 SL Relay Enhancements,” Huawei and HiSilicon; and TS 38.331 V18.0.0, “NR; Radio Resource Control (RRC) Protocol Specification (Release 18).” The standards and documents listed above are hereby expressly incorporated by reference in their entirety.

[0023] Figure 1 1 shows a multiple access wireless communication system according to an embodiment of the present invention. An access network 100 (AN) includes multiple antenna groups, one including 104 and 106, another including 108 and 110, and another including 112 and 114. Figure 1 In FIG, only two antennas are shown for each antenna group, however, more or fewer antennas may be utilized for each antenna group. Access terminal 116 (AT) communicates with antennas 112 and 114, where antennas 112 and 114 transmit information to AT 116 via forward link 120 and receive information from AT 116 via reverse link 118. Access terminal 122 communicates with antennas 106 and 108, where antennas 106 and 108 transmit information to AT 122 via forward link 126 and receive information from AT 122 via reverse link 124. In an FDD system, communication links 118, 120, 124, and 126 may utilize different frequencies for communication. For example, forward link 120 may utilize a different frequency than that utilized by reverse link 118.

[0024] Each group of antennas and / or the area in which they are designed to communicate is often referred to as a sector of the access network. In an embodiment, the antenna groups are each designed to communicate with access terminals in a sector of the area covered by the access network 100.

[0025] In communications over forward links 120 and 126, the transmit antennas of access network 100 may utilize beamforming to improve the signal-to-noise ratio of the forward links for the different access terminals 116 and 122. Furthermore, an access network that uses beamforming to transmit to access terminals randomly dispersed throughout the coverage area of ​​the access network may cause less interference to access terminals in neighboring cells than an access network that transmits to all of its access terminals via a single antenna.

[0026] An access network (AN) may be a fixed station or base station for communicating with a terminal and may also be referred to as an access point, a Node B, a base station, an enhanced base station, an evolved Node B (eNB), a network node, a network, or some other terminology. An access terminal (AT) may also be referred to as a user equipment (UE), a wireless communication device, a terminal, an access terminal, or some other terminology.

[0027] Figure 2 2 is a simplified block diagram of an embodiment of a transmitter system 210 (also referred to as an access network) and a receiver system 250 (also referred to as an access terminal (AT) or user equipment (UE)) in a MIMO system 200. At the transmitter system 210, traffic data for a number of data streams is provided from a data source 212 to a transmit (TX) data processor 214.

[0028] In one embodiment, each data stream is transmitted through a respective transmit antenna. TX data processor 214 formats, codes, and interleaves the traffic data for each data stream based on a particular coding scheme selected for that data stream to provide coded data.

[0029] The coded data for each data stream may be multiplexed with pilot data using OFDM techniques. The pilot data is typically a known data pattern that is processed in a known manner and may be used at the receiver system to estimate the channel response. The multiplexed pilot and coded data for each data stream is then modulated (i.e., symbol mapped) based on a particular modulation scheme selected for that data stream (e.g., BPSK, QPSK, M-PSK, or M-QAM) to provide modulation symbols. Instructions executed by processor 230 may determine the data rate, coding, and modulation for each data stream.

[0030] The modulation symbols for all data streams are then provided to a TX MIMO processor 220, which may further process the modulation symbols (e.g., for OFDM). The TX MIMO processor 220 then converts the N T The modulation symbol stream is provided to N Ttransmitters (TMTR) 222a through 222t. In certain embodiments, TX MIMO processor 220 applies beamforming weights to the symbols of the data streams and to the antenna from which the symbol is being transmitted.

[0031] Each transmitter 222 receives and processes a respective symbol stream to provide one or more analog signals, and further conditions (eg, amplifies, filters, and upconverts) the analog signals to provide a modulated signal suitable for transmission over the MIMO channel. T The antennas 224a to 224t transmit N signals from transmitters 222a to 222t. T a modulated signal.

[0032] At the receiver system 250, N R The transmitted modulated signals are received by each antenna 252a through 252r and the received signal from each antenna 252 is provided to a respective receiver (RCVR) 254a through 254r. Each receiver 254 conditions (e.g., filters, amplifies, and downconverts) a respective received signal, digitizes the conditioned signal to provide samples, and further processes the samples to provide a corresponding "received" symbol stream.

[0033] RX data processor 260 then extracts the N R The receiver 254 receives and processes N R received symbol streams to provide N T The RX data processor 260 then demodulates, deinterleaves, and decodes each detected symbol stream to recover the traffic data for the data stream. The processing by the RX data processor 260 is complementary to that performed by the TX MIMO processor 220 and the TX data processor 214 at the transmitter system 210.

[0034] Processor 270 periodically determines which precoding matrix to use (discussed below). Processor 270 formulates a reverse link message comprising a matrix index portion and a rank value portion.

[0035] The reverse link message may include various types of information regarding the communication link and / or the received data stream. The reverse link message is then processed by the TX data processor 238 (which also receives traffic data for a number of data streams from the data source 236), modulated by the modulator 280, conditioned by the transmitters 254a through 254r, and transmitted back to the transmitter system 210.

[0036] At transmitter system 210, the modulated signal from receiver system 250 is received by antenna 224, conditioned by receiver 222, demodulated by demodulator 240, and processed by RX data processor 242 to extract the reverse link message transmitted by receiver system 250. Processor 230 then determines which precoding matrix to use to determine the beamforming weights and then processes the extracted message.

[0037] Go to Figure 3 , this figure shows an alternative simplified functional block diagram of a communication device according to one embodiment of the present invention. Figure 3 As shown, the communication device 300 in the wireless communication system can be used to implement Figure 1 UE (or AT) 116 and 122 in or Figure 1 The base station (or AN) 100 in the wireless communication system is preferably an NR system. The communication device 300 may include an input device 302, an output device 304, a control circuit 306, a central processing unit (CPU) 308, a memory 310, a program code 312, and a transceiver 314. The control circuit 306 executes the program code 312 in the memory 310 through the CPU 308, thereby controlling the operation of the communication device 300. The communication device 300 can receive signals input by the user through the input device 302 (for example, a keyboard or a keypad), and can output images and sounds through the output device 304 (for example, a monitor or a speaker). The transceiver 314 is used to receive and transmit wireless signals, pass the received signals to the control circuit 306, and wirelessly output the signals generated by the control circuit 306. The communication device 300 in the wireless communication system can also be used to implement Figure 1 AN 100 in.

[0038] Figure 4 According to one embodiment of the present invention Figure 3 . In this embodiment, program code 312 includes an application layer 400, a layer 3 portion 402, and a layer 2 portion 404, and is coupled to a layer 1 portion 406. Layer 3 portion 402 generally performs radio resource control. Layer 2 portion 404 generally performs link control. Layer 1 portion 406 generally performs physical connectivity.

[0039] The 3GPP Stage 2 specification for Release 18 (TS 38.300) specifies Layer 2 Inter-UE (L2 U2U) relay as follows:

[0040] 16.12 Sidelink Relay

[0041] 16.12.1 Overview

[0042] Sidelink relays are introduced to support the 5G ProSe UE-to-Network Relay (U2N Relay) functionality (specified in TS 23.304

[48] ) to provide connectivity to the network for U2N remote UEs. Both L2 and L3 U2N relay architectures are supported. The L3 U2N relay architecture is transparent to the serving NG-RAN of the U2N relay UE, with the difference being the control of the sidelink resources. The detailed architecture and procedures for L3 U2N relay can be found in TS 23.304

[48] .

[0043] The U2N relay UE shall be in RRC_CONNECTED to perform relaying of unicast data.

[0044] For L2 U2N relay operation, the following RRC state combinations are supported:

[0045] - Both the L2 U2N relay UE and the L2 U2N remote UE should be in RRC_CONNECTED to perform transmission / reception of relayed unicast data; and

[0046] - The L2 U2N relay UE can be in RRC_IDLE, RRC_INACTIVE or RRC_CONNECTED as long as all L2 U2N remote UEs connected to the L2 U2N relay UE are in RRC_INACTIVE or RRC_IDLE.

[0047] A single unicast link is established between one L2 U2N relay UE and one L2 U2N remote UE. Traffic from the NG-RAN to the L2 U2N remote UE via the given L2 U2N relay UE and traffic from the L2 U2N relay UE should be separated in different Uu RLC channels.

[0048] For L2 U2N relay, the L2 U2N remote UE may only be configured to use resource allocation mode 2 (as specified in 5.7.2 and 16.9.3.1) for relaying data.

[0049] Sidelink relay is introduced to support the 5G ProSe inter-UE relay (U2U relay) functionality (specified in TS 23.304

[48] ), providing connectivity between U2U remote UEs. Both L2 and L3 U2U relay architectures are supported. The L3 U2U relay architecture is transparent to the AS layer of the U2U relay UE. The detailed architecture and procedures for L3 U2U relay can be found in TS 23.304

[48] .

[0050] A U2U Relay UE shall support the U2U Relay functionality as specified in TS 23.304

[48] to provide coverage extension for sidelink transmission between two U2U Remote UEs. For coverage extension, a U2U Remote UE may communicate with a peer U2U Remote UE that is not reachable within the sidelink coverage area.

[0051] The U2U relay UE and the U2U remote UE can be in any RRC state. The U2U relay UE and the U2U remote UE can be in the coverage of different cells or out of coverage. The U2U relay UE and the U2U remote UE support two sidelink resource allocation modes, namely, Mode 1 and Mode 2. For U2U relay, the NR sidelink is supported between the U2U relay UE and the U2U remote UE. After the NR sidelink is established between the U2U relay UE and the U2U remote UE, an end-to-end PC5 unicast link connection establishment is performed between the U2U remote UEs. Only unicast is supported between the U2U relay UE and the U2U remote UE.

[0052] […]

[0053] 16.12.2.2 L2 Inter-UE Relay

[0054] The protocol stacks for the user plane and control plane of the L2 U2U relay architecture are shown in Figures 16.12.2.2-1 and 16.12.2.2-2. The SRAP sublayer is located above the RLC sublayer for the CP and UP at the two PC5 interfaces. Sidelink SDAP, PDCP, and RRC terminate between the two L2 U2U remote UEs (i.e., end-to-end), while SRAP, RLC, MAC, and PHY terminate at each hop of the PC5 link.

[0055] [Figure 16.12.2.2-1 of 3GPP TS 38.300 V18.0.0 entitled "User plane protocol stack for L2 inter-UE relay" is reproduced as Figure 5 ]

[0056] [Figure 16.12.2.2-2 of 3GPP TS 38.300 V18.0.0 entitled "Control plane protocol stack for L2 inter-UE relay" is reproduced as Figure 6 ]

[0057] For L2 inter-UE relay, the SRAP sublayer at the L2 U2U remote UE:

[0058] - The SRAP sublayer at the L2 U2U remote UE performs bearer mapping between end-to-end PC5 radio bearers (SL-SRB or SL-DRB) of the L2 U2U remote UE at each hop of the PC5 relay RLC channel between the L2 U2U remote UE and the L2 U2U relay UE.

[0059] -For traffic transmitted from an L2 U2U remote UE to an L2 U2U relay UE, different end-to-end PC5 radio bearers (SL-SRB or SL-DRB) destined for the same peer L2 U2U remote UE and / or different peer L2 U2U remote UEs may be multiplexed into the same PC5 relay RLC channel between the L2 U2U remote UE and the L2 U2U relay UE.

[0060] - For traffic received at an L2 U2U remote UE, the same PC5 relay RLC channel from one L2 U2U relay UE may be demultiplexed to different end-to-end PC5 radio bearers (SL-SRB or SL-DRB) to the same peer L2 U2U remote UE and / or different peer L2 U2U remote UEs.

[0061] The SRAP sublayer at the L2 U2U Remote UE supports identification of both the peer L2 U2U Remote UE and itself. Local IDs are assigned by the L2U2U Relay UE to both L2 U2U Remote UEs for identification purposes. One of the two Local IDs identifies the L2 U2U Remote UE, and the other identifies the peer L2 U2U Remote UE. The local ID of the peer L2 U2U Remote UE and the local ID of the L2U2U Remote UE, along with the corresponding L2 ID of the peer L2 U2U Remote UE, are delivered to the L2 U2U Remote UE by the L2 U2U Relay UE. The identity information of the end-to-end PC5 radio bearer and the two local IDs are included in the SRAP header, enabling the peer L2U2U Remote UE to associate received packets for a specific PDCP entity with the correct end-to-end PC5 radio bearer for the L2 U2U Remote UE.

[0062] For L2 inter-UE relay, the SRAP sublayer at the L2 U2U relay UE:

[0063] - The SRAP sublayer at the L2 U2U Relay UE determines the egress PC5 Relay RLC channel based on a mapping of end-to-end PC5 radio bearers and egress PC5 Relay RLC channels for a specific pair between the L2 U2U Remote UE and the peer L2 U2U Remote UE.

[0064] -For ingress traffic received from one / multiple L2 U2U remote UEs at an L2 U2U relay UE, different end-to-end PC5 radio bearers (SL-SRB or SL-DRB) of the same L2 U2U remote UE and / or the same / different end-to-end PC5 radio bearers (SL-SRB or SL-DRB) of the L2 U2U remote UE may be multiplexed into the same egress PC5 relay RLC channel between the L2 U2U relay UE and the peer L2 U2U remote UE.

[0065] […]

[0066] 16.12.7 Control Plane Procedures for L2 U2U Relay

[0067] The L2 U2U remote UE needs to establish an end-to-end SL-SRB / DRB with the peer L2 U2U remote UE before user plane data transmission.

[0068] The following high-level connection establishment procedure in Figure 16.12.7-1 applies to both L2 U2U relay UE and L2U2U remote UE:

[0069] [Figure 16.12.7-1 of 3GPP TS 38.300 V18.0.0 entitled "Procedure for L2 U2U Remote UE Connection Establishment" is reproduced as Figure 7 ]

[0070] 1. The L2 U2U remote UE, the L2 U2U relay UE and the peer L2 U2U remote UE perform a discovery procedure or an integrated discovery procedure.

[0071] 2a. The L2 U2U remote UE establishes / modifies a PC5-RRC connection with the selected L2 U2U relay UE (ie as specified in TS 23.304

[48] ).

[0072] 2b. The L2 U2U Relay UE establishes / modifies a PC5-RRC connection with the peer L2 U2U Remote UE (ie as specified in TS 23.304

[48] ).

[0073] 3. The L2 U2U relay UE allocates two local IDs, which are delivered to each L2 U2U remote UE via an RRCReconfigurationSidelink message: one local ID for identifying the L2 U2U remote UE, and the other local ID for identifying the peer L2 U2U remote UE. When the local IDs are delivered, the L2 ID of the peer L2 U2U remote UE is also delivered to the U2U remote UE for association between the local ID and the L2 ID of the peer U2U remote UE.

[0074] 4. An L2 U2U remote UE establishes an end-to-end PC5-RRC connection with its peer L2 U2U remote UE via an L2 U2U relay UE. For end-to-end connection establishment, fixed indices (i.e., 0 / 1 / 2 / 3) are defined for end-to-end SL-SRB 0 / 1 / 2 / 3, respectively, and a specific PC5 relay RLC channel configuration is used on each hop. Sidelink UE capabilities are exchanged between L2 U2U remote UEs via PC5-RRC (e.g., SL-SRB3) messages.

[0075] 5. The L2 U2U remote UE sends all QoS attribute sets for the end-to-end QoS flow to the L2 U2U relay UE via PC5-RRC.

[0076] 6. The L2 U2U relay UE performs QoS splitting only for PDBs.

[0077] Note: It is up to the L2 U2U relay UE implementation to decide how to split the PDB.

[0078] 7. The L2 U2U relay UE sends the split QoS value (ie, PDB) to the L2 U2U remote UE via PC5-RRC message.

[0079] 8. The L2 U2U Remote UE or the L2 U2U Remote UE's serving gNB derives the PDCP and SDAP configuration for the end-to-end SL-DRB and provides the reception-related portion of the configuration to the peer L2 U2U Remote UE using an End-to-End RRCReconfigurationSidelink message. The end-to-end bearer ID for the SL-SRB and SL-DRB is used as input for L2 U2U Relay encryption and decryption at PDCP.

[0080] 9a. The L2 U2U remote UE or the serving gNB of the L2 U2U remote UE derives the first-hop configuration for the SL-DRB (e.g., PC5 relay RLC channel configuration) and provides the configuration related to reception on the first hop (i.e., Rx by the relay UE) to the L2 U2U relay UE using a per-hop RRCReconfigurationSidelink message.

[0081] 9b. The L2 U2U relay UE or the L2 U2U relay UE's serving gNB derives the second-hop configuration (e.g., PC5 relay RLC channel configuration) for each SL-DRB and provides the configuration related to receiving packets on the second hop (i.e., RX by the peer remote UE) to the peer L2 U2U remote UE using a per-hop RRCReconfigurationSidelink message.

[0082] 10. The L2 U2U remote UE and the peer L2 U2U remote UE transmit or receive data via the L2 U2U relay UE.

[0083] 3GPP R2-2402042 is a change request (CR) related to L2 U2U relay on top of Release 18 RRC specification (TS 38.331). The following content related to L2 U2U relay is quoted from 3GPP TS 38.331 with modifications from 3GPP R2-2402042:

[0084] 5.8.9.1 Sidelink RRC Reconfiguration

[0085] 5.8.9.1.1 Overview

[0086] [3GPP R2-2402042 titled "Sidelink RRC reconfiguration, successful" Figure 5 .8.9.1.1-1 is reproduced as Figure 8 ]

[0087] […]

[0088] The purpose of this procedure is to modify the PC5-RRC connection, such as establishing / modifying / releasing sidelink DRB or additional sidelink RLC bearer or PC5 relay RLC channel, adding / modifying / releasing sidelink carrier, (re)configuring NR sidelink measurement and reporting, (re)configuring sidelink CSI reference signal resources, (re)configuring CSI reporting delay bound, (re)configuring sidelink DRX, (re)configuring delay bound for SL inter-UE coordinated reporting and indicating SFN-DFN offset.

[0089] In the following cases, the UE may initiate the sidelink RRC reconfiguration procedure and perform the operations in clause 5.8.9.1.2 on the corresponding PC5-RRC connection:

[0090] - in case of L2 U2U relay operation, the release of sidelink DRBs associated with a peer UE or L2 U2U relay UE and peer L2 U2U remote UE, as specified in clause 5.8.9.1a.1;

[0091] - in case of L2 U2U relay operation, establishment of sidelink DRBs associated with a peer UE or L2 U2U relay UE and a peer L2 U2U remote UE, as specified in clause 5.8.9.1a.2;

[0092] - modification of parameters contained in the SLRB-Config for the sidelink DRB associated with the peer UE, as specified in clause 5.8.9.1a.2;

[0093] - Release of additional sidelink RLC bearers associated with the peer UE, as specified in clause 5.8.9.1a.5;

[0094] - Establishment of additional sidelink RLC bearers associated with the peer UE, as specified in clause 5.8.9.1a.6;

[0095] - modify the parameters contained in the SL-RLC-BearerConfig of the additional sidelink RLC bearer associated with the peer UE, as specified in clause 5.8.9.1a.6;

[0096] - Release the PC5 relay RLC channels for L2 U2N / U2U relay UE and remote UE as specified in clause 5.8.9.7.1;

[0097] - Establishing PC5 relay RLC channels for L2 U2N / U2U relay UE and remote UE as specified in clause 5.8.9.7.2;

[0098] - Modify the parameters contained in SL-RLC-ChannelConfigPC5 of the PC5 relay RLC channel for L2 U2N / U2U relay UEs and remote UEs as specified in clause 5.8.9.7.2;

[0099] - Release of the sidelink carrier associated with the peer UE, as specified in clause 5.8.9.1b.1;

[0100] - the addition of a sidelink carrier associated with a peer UE, as specified in clause 5.8.9.1b.2;

[0101] - modification of the sidelink carrier associated with the peer UE, as specified in clause 5.8.9.1b.2;

[0102] - (Re)configure the peer UE to perform NR sidelink measurements and reporting.

[0103] - (Re)configuration of sidelink CSI reference signal resources and CSI reporting delay bounds;

[0104] - (re)configuration of a peer UE to perform sidelink DRX;

[0105] - (Re)configuration of delay bounds for coordinated reporting between SL UEs;

[0106] - (Re)configuration of Local UE ID pairs for an L2 U2U Remote UE and its peer L2 U2U Remote UE by an L2 U2U Relay UE.

[0107] - A response to a request for SFN-DFN offset from an L2 U2N remote UE in a RemoteUEInformationSidelink message;

[0108] - Change in the value of SFN-DFN offset at the L2 U2N relay UE.

[0109] NOTE: It is up to the L2 U2N Relay UE implementation to determine when the value of the SFN-DFN offset has changed to such an extent that an update needs to be sent to the L2 U2N Remote UE.

[0110] In RRC_CONNECTED, the UE applies the NR sidelink communication parameters provided in RRCReconfiguration (if present). In RRC_IDLE or RRC_INACTIVE, the UE applies the NR sidelink communication parameters provided in system information (if present). For other cases, the UE applies the NR sidelink communication parameters provided in SidelinkPreconfigNR (if present). When the UE performs a state transition between the above three cases, after obtaining the new configuration, the UE applies the NR sidelink communication parameters provided in the new state. Before obtaining the new configuration, the UE continues to apply the NR sidelink communication parameters provided in the old state.

[0111] 5.8.9.1.2 Actions Related to the Transmission of the RRCReconfigurationSidelink Message

[0112] The UE shall set the content of the RRCReconfigurationSidelink message as follows:

[0113] […]

[0114] 1> If the UE acts as an L2 U2U relay UE and if a procedure is initiated to configure a local ID pair to a connected L2 U2U remote UE:

[0115] 2> If a local ID pair is to be assigned or modified for end-to-end PC5 connection, and if the PC5-RRC connection with this L2U2U remote UE and the per-hop PC5-RRC connection with its peer L2 U2U remote UE are successfully established:

[0116] Include the entry in sl-LocalID-PairToAddModList and set the fields as follows:

[0117] 4> set sl-RemoteUE-L2Identity to the source L2 ID of this L2 U2U remote UE according to the association between user information and L2 ID as specified in TS 23.304

[65] , and set sl-RemoteUE-LocalIdentity to include the new local UE ID assigned to this L2 U2U remote UE in SL-SRAP-ConfigPC5 (if needed);

[0118] 4> set sl-PeerRemoteUE-L2Identity to the destination L2 ID of the peer L2 U2U remote UE according to the association between user information and L2 ID as specified in TS 23.304

[65] , and set sl-PeerRemoteUE-LocalIdentity to include the new local UE ID assigned to the peer L2 U2U remote UE in SL-SRAP-ConfigPC5 (if needed);

[0119] 2> Otherwise, if the local ID pair is to be released for use in an end-to-end PC5 connection:

[0120] 3> include an entry in sl-LocalID-PairToReleaseList, where the value of SL-DestinationIdentity is set to the destination L2 ID of the peer L2 U2U remote UE;

[0121] 1> if the UE acts as an L2 U2U remote UE (i.e., Tx UE and is in RRC_IDLE or RRC_INACTIVE or out of coverage), and if a procedure is initiated to add / modify the first-hop PC5 relay RLC channel of the end-to-end sidelink DRB to a connected L2 U2U relay UE (i.e., Rx UE) based on the configuration in SIB12 or SidelinkPreconfigNR; or

[0122] 1> If the UE acts as an L2 U2U relay UE (i.e., Tx UE) and is in RRC_IDLE or RRC_INACTIVE or out of coverage, and if a procedure is initiated to add / modify a second-hop PC5 relay RLC channel to a connected L2 U2U remote UE (i.e., Rx UE) based on the configuration in SIB12 or SidelinkPreconfigNR:

[0123] 2> To establish a PC5 relay RLC channel:

[0124] 3> Assign a new RLC channel ID and set sl-RLC-ChannelID-PC5 in SL-RLC-ChannelConfigPC5 to include the new RLC channel ID;

[0125] 3> Assign a new logical channel identity for the logical channel to be associated with the PC5 relay RLC channel and set sl-MAC-LogicalChannelConfigPC5 in SL-RLC-ChannelConfigPC5 to contain the new logical channel identity;

[0126] 2> If the UE is in RRC_IDLE or RRC_INACTIVE:

[0127] 3> Set the SL-RLC-ChannelConfigPC5 contained in sl-RLC-ChannelToAddModListPC5 according to the SL-RLC-BearerConfig derived based on the per-hop QoS of the end-to-end SLRB according to SIB12;

[0128] 2> Otherwise, if the UE is out of coverage:

[0129] 3> Set the SL-RLC-ChannelConfigPC5 contained in sl-RLC-ChannelToAddModListPC5 according to the SL-RLC-BearerConfig derived based on the per-hop QoS of the SLRB according to SidelinkPreconfigNR;

[0130] 1> if the UE acts as an L2 U2U remote UE (i.e., Tx UE) and is in RRC_IDLE or RRC_INACTIVE or out of coverage, and initiates a procedure according to clause 5.8.9.7.1 to release the first-hop PC5 relay RLC channel of the end-to-end side link DRB to a connected L2 U2U relay UE (i.e., Rx UE); or

[0131] 1> If the UE acts as an L2 U2U relay UE (i.e., Tx UE) and is in RRC_IDLE or RRC_INACTIVE or out of coverage, and initiates a procedure according to clause 5.8.9.7.1 to release the second-hop PC5 relay RLC channel of the end-to-end side link DRB to the connected L2 U2U remote UE (i.e., Rx UE):

[0132] 2> Set the SL-RLC-ChannelID corresponding to the PC5 relay RLC channel in sl-RLC-ChannelToReleaseListPC5;

[0133] NOTE 3: If the UE is in RRC_IDLE or in RRC_INACTIVE or out of coverage, how to merge the split per-flow QoS on the first / second hop into the per-SLRB level QoS derived for RLC channel configuration depends on the UE implementation.

[0134] The UE shall submit an RRCReconfigurationSidelink message to lower layers for transmission.

[0135] 5.8.9.1.3UE receives RRCReconfigurationSidelink

[0136] The UE shall perform the following actions after receiving RRCReconfigurationSidelink:

[0137] […]

[0138] 1> If RRCReconfigurationSidelink contains sl-RLC-ChannelToReleaseListPC5:

[0139] 2> for each SL-RLC-ChannelID value contained in sl-RLC-ChannelToReleaseListPC5 as part of the current UE-side link configuration;

[0140] 3>Perform the PC5 relay RLC channel release procedure according to clause 5.8.9.7.1;

[0141] 1> If RRCReconfigurationSidelink contains sl-RLC-ChannelToAddModListPC5:

[0142] 2> For each sl-RLC-ChannelID-PC5 value contained in sl-RLC-ChannelToAddModListPC5 that is not part of the current UE-side link configuration:

[0143] 3>Perform the PC5 relay RLC channel addition procedure according to clause 5.8.9.7.2;

[0144] 2> For each sl-RLC-ChannelID-PC5 value contained in sl-RLC-ChannelToAddModListPC5 as part of the current UE side link configuration:

[0145] 3>Perform the PC5 relay RLC channel modification procedure according to clause 5.8.9.7.2;

[0146] […]

[0147] 1> If the RRCReconfigurationSidelink message contains sl-LocalID-PairToReleaseList or sl-LocalID-PairToAddModList:

[0148] 2> configure the SRAP entity to perform NR sidelink L2 U2U relay operations accordingly for end-to-end PC5 connectivity to peer L2 U2U remote UEs as defined in TS 38.351

[65] ;

[0149] […]

[0150] 5.8.9.1a.1.1 Sidelink DRB Release Conditions

[0151] For NR sidelink communications, sidelink DRB release is initiated in the following cases:

[0152] 1> For multicast, broadcast, and unicast, if the slrb-Uu-ConfigIndex (if present) of the sidelink DRB is included in the sl-RadioBearerToReleaseList in the sl-ConfigDedicatedNR; or

[0153] 1> For multicast and broadcast, if no sidelink QoS flow with data indicated by upper layers is mapped to a sidelink DRB for transmission, the sidelink QoS flow is (re)configured by receiving SIB12 or SidelinkPreconfigNR; or

[0154] 1> for multicast, broadcast, and unicast, if the SL-RLC-BearerConfigIndex (if present) of the associated RLC entity for the sidelink DRB (i.e., including the additional sidelink RLC bearers, if applicable) is contained in the sl-RLC-BearerToReleaseList / sl-RLC-BearerToReleaseListSizeExt in the sl-ConfigDedicatedNR; or

[0155] 1> for unicast, if no sidelink QoS flow with data indicated by upper layers is mapped to the sidelink DRB for transmission, the sidelink QoS flow is (re)configured by receiving SIB12 or SidelinkPreconfigNR, and if no sidelink QoS flow is mapped to the sidelink DRB, the sidelink QoS flow is (re)configured by receiving RRCReconfigurationSidelink with data; or

[0156] 1> for unicast, if the SLRB-PC5-ConfigIndex (if present) of the sidelink DRB is included in slrb-ConfigToReleaseList in RRCReconfigurationSidelink or if sl-ResetConfig is included in RRCReconfigurationSidelink; or

[0157] 1> for unicast, when the corresponding PC5-RRC connection is released due to detection of sidelink RLF according to clause 5.8.9.3; or

[0158] 1> For unicast, when the corresponding PC5-RRC connection is released due to a request from upper layers according to clause 5.8.9.5; or

[0159] 1> For L2 U2U trunking operation, when the corresponding end-to-end PC5 connection failure / release is detected according to clause 5.8.9.3a or 5.8.9.3b; or

[0160] 1> For L2 U2U relay operation, if no sidelink QoS flow indicated by the source L2 U2U remote UE is mapped to an end-to-end sidelink DRB for transmission when the UE acts as a L2 U2U relay UE.

[0161] 5.8.9.1a.1.2 Sidelink DRB Release Operation

[0162] For each sidelink DRB for which the sidelink DRB release conditions are met as in clause 5.8.9.1a.1.1, a UE capable of NR sidelink communication that is configured by upper layers to perform NR sidelink communication shall:

[0163] 1> for multicast and broadcast; or

[0164] 1> For unicast, if the sidelink DRB release is triggered after receiving the RRCReconfigurationSidelink message; or

[0165] 1> For unicast, after receiving the RRCReconfigurationCompleteSidelink message, if the sidelink DRB release is triggered due to the configuration received in sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR or indicated by upper layers, then:

[0166] 2> Release the PDCP entity used for NR sidelink communication associated with the sidelink DRB;

[0167] 2> If the SDAP entity used for NR sidelink communication associated with this sidelink DRB is configured as:

[0168] 3> Indicate the release of the sidelink DRB to the SDAP entity associated with this sidelink DRB (TS 37.324

[24] , clause 5.3.3);

[0169] 2> Release the SDAP entity (if any) that does not have an associated sidelink DRB as specified in TS 37.324

[24] clause 5.1.2 for NR sidelink communication;

[0170] 1> for multicast and broadcast; or

[0171] 1> For unicast, after receiving the RRCReconfigurationCompleteSidelink message, if the sidelink DRB release is triggered due to the configuration received in sl-ConfigDedicatedNR:

[0172] 2> For each sl-RLC-BearerConfigIndex included in the received sl-RLC-BearerToReleaseList / sl-RLC-BearerToReleaseListSizeExt as part of the current UE-side link configuration:

[0173] 3> Release the RLC entity and corresponding logical channel used for NR sidelink communication, where the NR sidelink communication is associated with sl-RLC-BearerConfigIndex.

[0174] 1> For unicast, if the sidelink DRB release is triggered by receiving an RRCReconfigurationSidelink message; or

[0175] 1> For unicast, after receiving the RRCReconfigurationCompleteSidelink message, if the sidelink DRB release is triggered due to the configuration received in SIB12, SidelinkPreconfigNR or indicated by upper layers:

[0176] 2> Release the RLC entity and corresponding logical channel used for NR sidelink communication associated with the sidelink DRB;

[0177] 2> Perform the Sidelink UE Information procedure for unicast in clause 5.8.3 when needed.

[0178] 1> If a sidelink radio link failure is detected for a particular destination:

[0179] 2> Release the PDCP entity, RLC entity and logical channels of the sidelink SRB for a specific destination.

[0180] 1> If the sidelink DRB is an end-to-end sidelink DRB in L2 U2U relay operation:

[0181] 2> If there are no other end-to-end side link DRBs associated with this RLC channel, perform PC5 relay RLC channel release according to 5.8.9.7.1;

[0182] 2> If the UE acts as a source L2 U2U remote / relay UE and is in RRC_CONNECTED:

[0183] 3> reconfigure the SRAP entity for the sidelink DRB according to the sl-SRAP-ConfigU2U received in the sl-ConfigDedicatedNR (if included);

[0184] 2> Otherwise if the UE acts as a source L2 U2U remote UE / relay and is in RRC_IDLE or RRC_INACTIVE:

[0185] 3> Reconfigure the SRAP entity for the sidelink DRB derived based on the configuration received in SIB12;

[0186] 2> Otherwise if the UE acts as a source L2 U2U remote / relay UE and is out of coverage:

[0187] 3> Reconfigure the SRAP entity for the sidelink DRB derived based on the configuration received in SidelinkPreconfigNR;

[0188] 5.8.9.1a.2.1 Sidelink DRB Addition / Modification Conditions

[0189] For NR sidelink communications, sidelink DRB addition is initiated only in the following cases:

[0190] 1> if any sidelink QoS flow is (re)configured by sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR and will be mapped to a sidelink DRB that is not established; or

[0191] 1> If any sidelink QoS flow is (re)configured by RRCReconfigurationSidelink and will be mapped to an unestablished sidelink DRB;

[0192] 1> if any sidelink QoS flow is (re)configured by the source L2 U2U remote UE and mapped to an end-to-end sidelink DRB for transmission when the UE acts as an L2 U2U relay UE;

[0193] For NR sidelink communications, sidelink DRB modification is initiated only in the following cases:

[0194] 1> If, for an established sidelink DRB, any of the sidelink DRB-related parameters are changed via sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR, or RRCReconfigurationSidelink;

[0195] 5.8.9.1a.2.2 Sidelink DRB Add / Modify Operation

[0196] For a sidelink DRB for which the sidelink DRB addition conditions are met as in clause 5.8.9.1a.2.1, an NR sidelink capable UE configured by upper layers to perform NR sidelink communication shall:

[0197] 1> for multicast and broadcast; or

[0198] 1> For unicast, if the sidelink DRB addition is triggered due to the reception of an RRCReconfigurationSidelink message; or

[0199] 1> For unicast, after receiving the RRCReconfigurationCompleteSidelink message, if the sidelink DRB addition is triggered due to the configuration received in sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR or indicated by upper layers, then:

[0200] 2> If there is no SDAP entity for NR sidelink communication associated with the destination and broadcast type of the sidelink DRB:

[0201] 3> Establishing the SDAP entity for NR sidelink communication as specified in TS 37.324

[24] clause 5.1.1;

[0202] 2> (Re)configure the SDAP entity according to the sl-SDAP-ConfigPC5 received in RRCReconfigurationSidelink or the sl-SDAP-Config received in sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR associated with the sidelink DRB;

[0203] 2> establish a PDCP entity for NR sidelink communication and configure it according to the sl-PDCP-ConfigPC5 received in RRCReconfigurationSidelink or the sl-PDCP-Config received in sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR associated with the sidelink DRB;

[0204] 2> For per-hop sidelink DRB (i.e., the UE is performing NR sidelink communication with a peer UE):

[0205] 3> Establish an RLC entity for NR sidelink communication and configure it according to the sl-RLC-ConfigPC5 received in RRCReconfigurationSidelink or the sl-RLC-Config received in sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR associated with the sidelink DRB;

[0206] 3> If this procedure is due to receiving an RRCReconfigurationSidelink message:

[0207] 4> Configure the MAC entity with the logical channel according to the sl-MAC-LogicalChannelConfigPC5 received in RRCReconfigurationSidelink associated with the sidelink DRB and perform the Sidelink UE Information procedure in clause 5.8.3 for unicast if required;

[0208] 3> Otherwise, if this procedure is due to receipt of an RRCReconfigurationCompleteSidelink message, then:

[0209] 4> Configure the MAC entity with the logical channel associated with the sidelink DRB according to the sl-MAC-LogicalChannelConfig received in sl-ConfigDedicatedNR, SIB12, and SidelinkPreconfigNR;

[0210] 3> Otherwise (i.e., for multicast / broadcast):

[0211] 4> Configure the MAC entity with the logical channel associated with the sidelink DRB according to the sl-MAC-LogicalChannelConfig received in sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR, and assign a new LCID to this logical channel.

[0212] 2> For end-to-end side link DRB (i.e., UE acts as L2 U2U remote UE):

[0213] 3> If the UE is in RRC_CONNECTED:

[0214] 4> Associate this end-to-end side link DRB with the PC5 RLC channel indicated by sl-EgressRLC-ChannelPC5 contained in sl-ConfigDedicatedNR received from RRCReconfiguration;

[0215] 3> Otherwise, if the UE is in RRC_IDLE or RRC_INACTIVE:

[0216] 4> Based on the configuration in SIB12, the PC5 RLC channel exported through the per-SLRB QoS profile of this end-to-end side link DRB is regarded as an egress PC5 relay RLC channel;

[0217] 4> Associate this end-to-end side link DRB with the PC5 RLC channel and configure the mapping to the SRAP;

[0218] 3> Otherwise, if the UE is out of coverage:

[0219] 4> Based on the configuration in SidelinkPreconfigNR, the PC5 RLC channels exported through the per-SLRB QoS profile of this end-to-end side link DRB are considered as egress PC5 relay RLC channels;

[0220] 4> Associate this end-to-end side link DRB with the PC5 RLC channel and configure the mapping to the SRAP;

[0221] NOTE 1: When the sidelink DRB addition is due to the configuration of RRCReconfigurationSidelink, it is up to the UE implementation to select the sidelink DRB configuration that transmits the parameters of the sidelink DRB as needed from the received sl-ConfigDedicatedNR (if in RRC_CONNECTED), SIB12 (if in RRC_IDLE / INACTIVE), SidelinkPreconfigNR (if not in coverage) with the same RLC mode as configured in RRCReconfigurationSidelink.

[0222] For a sidelink DRB for which the sidelink DRB modification conditions are met as in clause 5.8.9.1a.2.1, an NR sidelink capable UE configured by upper layers to perform NR sidelink communication shall:

[0223] 1> for multicast and broadcast; or

[0224] 1> For unicast, if the sidelink DRB modification is triggered by receiving an RRCReconfigurationSidelink message; or

[0225] 1> For unicast, after receiving the RRCReconfigurationCompleteSidelink message, if the sidelink DRB modification is triggered due to the configuration received in sl-ConfigDedicatedNR, SIB12 or SidelinkPreconfigNR:

[0226] 2> Reconfigure the SDAP entity of the sidelink DRB according to the sl-SDAP-ConfigPC5 received in RRCReconfigurationSidelink or the sl-SDAP-Config received in sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR (if included);

[0227] 2> reconfigure the PDCP entity for the sidelink DRB according to the sl-PDCP-ConfigPC5 received in RRCReconfigurationSidelink or the sl-PDCP-Config received in sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR (if included);

[0228] 2> Reconfigure the RLC entity of the sidelink DRB according to the sl-RLC-ConfigPC5 received in RRCReconfigurationSidelink or the sl-RLC-Config received in sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR (if included);

[0229] 2> Reconfigure the logical channels of the sidelink DRB according to the sl-MAC-LogicalChannelConfigPC5 received in RRCReconfigurationSidelink or the sl-MAC-LogicalChannelConfig received in sl-ConfigDedicatedNR, SIB12, SidelinkPreconfigNR (if included);

[0230] 2> For end-to-end side link DRB (i.e., UE acts as L2 U2U remote UE):

[0231] 3> If the UE is in RRC_CONNECTED:

[0232] 4> Reconfigure the SRAP entity for the sidelink DRB according to the sl-SRAP-ConfigU2U received in the sl-ConfigDedicatedNR (if included);

[0233] 3> Otherwise, if the UE is in RRC_IDLE or RRC_INACTIVE:

[0234] 4> Reconfigure the SRAP entity for the sidelink DRB derived based on the configuration received in SIB12;

[0235] 3> Otherwise, if the UE is out of coverage:

[0236] 4> Reconfigure the SRAP entity for the sidelink DRB derived based on the configuration received in SidelinkPreconfigNR.

[0237] […]

[0238] 5.8.9.3 Sidelink Radio Link Failure Related Actions

[0239] The UE shall:

[0240] 1> after an indication from the sidelink RLC entity that the maximum number of retransmissions for a particular destination has been reached; or

[0241] 1> after the expiry of the T400 for a specific destination; or

[0242] 1> after an indication from the MAC entity that the maximum number of consecutive HARQ DTXs for a particular destination has been reached; or

[0243] 1> after an integrity check failure indication from the sidelink PDCP entity for SL-SRB2 or SL-SRB3 for a specific destination; or

[0244] 1> Following an indication of consistent sidelink LBT failure for all RB sets for a specific destination from the MAC entity:

[0245] 2> Consider a sidelink radio link failure detected for this destination;

[0246] 2> Release the DRB for this destination (if any) according to clause 5.8.9.1a.1;

[0247] 2> Release the SRB for this destination according to clause 5.8.9.1a.3;

[0248] 2> Release the PC5 relay RLC channel for this destination (if configured) according to clause 5.8.9.7.1;

[0249] 2> discard the configuration related to NR sidelink communication of this destination;

[0250] 2> Reset the sidelink-specific MAC for this destination, except for end-to-end PC5 connections in L2 U2U relay operation;

[0251] 2> Consider releasing the PC5-RRC connection for the destination;

[0252] 2> Indicates the release of the PC5-RRC connection to the upper layer for this destination (i.e., PC5 is unavailable);

[0253] 2> If the UE is in RRC_CONNECTED:

[0254] 3> If the UE acts as a L2 U2N remote UE for the destination, then:

[0255] 4> If MP is configured:

[0256] 5> Initiate the indirect path fault information procedure as specified in 5.7.3c;

[0257] 4> Otherwise:

[0258] 5> Initiate the RRC connection re-establishment procedure as specified in 5.3.7.

[0259] 3> Otherwise:

[0260] 4> Perform the sidelink UE information for NR sidelink communication procedures as specified in 5.8.3.3;

[0261] 2> If the UE acts as an L2 U2U relay UE for identifying the destination of a connected L2 U2U remote UE:

[0262] 3> Consider end-to-end PC5 connection failure for end-to-end PC5 connection established through each hop PC5 link with L2 U2U remote UE;

[0263] 3> Send NotificationMessageSidelink to the peer L2 U2U remote UE of the end-to-end PC5 connection as per 5.8.9.10.

[0264] 3> Initiate actions related to the end-to-end PC5 connection failure as specified in 5.8.9.3b;

[0265] 2> If the UE acts as an L2 U2U remote UE for the destination of the L2 U2U relay UE identifying the connection:

[0266] 3> Consider end-to-end PC5 connection failure for end-to-end PC5 connection over each hop PC5 link established with L2 U2U relay UE;

[0267] 3> Initiate actions related to the end-to-end PC5 connection failure as specified in 5.8.9.3a;

[0268] NOTE: It is up to the UE implementation to decide whether and how to indicate to upper layers the maintenance of the keep-alive procedure

[55] .

[0269] 5.8.9.3a Actions related to end-to-end PC5 connection failures performed by L2 U2U remote UE

[0270] A UE acting as an NR sidelink L2 U2U remote UE shall:

[0271] 1> upon detection of an end-to-end PC5 connectivity failure due to a per-hop PC5 link failure, in accordance with clause 5.8.9.3; or

[0272] 1> Upon detection of an end-to-end PC5 connectivity failure due to the release of a per-hop PC5 link, in accordance with clause 5.8.9.5; or

[0273] 1>After the T400 of the end-to-end PC5 connection expires; or

[0274] 1> after an integrity check failure indication from the sidelink PDCP entity for SL-SRB2 or SL-SRB3 of the end-to-end PC5 connection; or

[0275] 1> According to clause 5.8.9.10.4, upon detection of end-to-end PC5 connectivity failure due to receipt of a NotificationMessageSidelink indicating PC5 RLF from an L2 U2U relay UE for a specific destination based on the received sl-DestinationIdentityRemoteUE:

[0276] 2> Release the end-to-end DRB for this end-to-end PC5 connection according to clause 5.8.9.1a.1;

[0277] 2> Release the end-to-end SRB used for this end-to-end PC5 connection according to clause 5.8.9.1a.3;

[0278] 2> discard the end-to-end NR side link communication related configuration for this end-to-end PC5 connection, including the SRAP configuration;

[0279] 2> For this end-to-end PC5 connection, the end-to-end PC5-RRC connection is considered to be released;

[0280] 2>Indicates the release of the end-to-end PC5-RRC connection to the upper layer;

[0281] 2> If the end-to-end PC5 connection failure is due to T400 expiration or SL-SRB2 or SL-SRB3 integrity check failure:

[0282] 3> According to 5.8.9.8.2, the RemoteUEInformationSidelink message is sent to the L2 relay UE in the middle of the end-to-end PC5 connection;

[0283] 5.8.9.3b End-to-end PC5 connection failure / release related actions performed by L2 U2U relay UE

[0284] A UE acting as an NR sidelink L2 U2U relay UE shall:

[0285] 1> after detecting an end-to-end PC5 connectivity failure due to a per-hop PC5 link failure, in accordance with clause 5.8.9.3; or

[0286] 1> after detecting an end-to-end PC5 connectivity failure due to the release of a per-hop PC5 link, in accordance with clause 5.8.9.5; or

[0287] 1> According to clause 5.8.9.8.3, based on the received sl-DestinationIdentityRemoteUE after receiving RemoteUEInfomationSidelink indicating end-to-end connection release or failure for a specific destination:

[0288] 2> The end-to-end DRB used for this end-to-end PC5 connection is considered to be released;

[0289] 2> The end-to-end SRB used for this end-to-end PC5 connection is considered to be released;

[0290] 2> Discard the end-to-end NR side link communication configuration for this end-to-end PC5 connection, including end-to-end SRB / DRB related configuration, QoS related configuration, and SRAP configuration;

[0291] […]

[0292] 5.8.9.5 Actions related to PC5-RRC connection release requested by upper layers

[0293] The UE initiates the procedure when upper layers request the release of the PC5-RRC connection as specified in TS 24.587

[57] or TS 24.554

[72] . The UE should not initiate the procedure for power saving purposes.

[0294] The UE shall:

[0295] 1> If the upper layer requests the release of the PC5-RRC connection for a specific destination:

[0296] 2> discard the configuration related to NR sidelink communication of this destination;

[0297] Release the DRB for this destination (if configured) according to clause 5.8.9.1a.1.

[0298] 2> Release the SRB for this destination according to clause 5.8.9.1a.3;

[0299] 2> Release the PC5 relay RLC channel (if configured) according to clause 5.8.9.7.1;

[0300] 2> Reset the sidelink specific MAC for this destination, except for end-to-end PC5-RRC connections in L2 U2U relay operation.

[0301] 2> Consider releasing the PC5-RRC connection for the destination;

[0302] 2> If the UE acts as an L2 U2U remote UE and this destination identifies the connected L2 U2U relay UE:

[0303] 3> Consider end-to-end PC5 connection failure for end-to-end PC5 connection over each hop PC5 link established with L2 U2U relay UE;

[0304] 3> Initiate actions related to the end-to-end PC5 connection failure as specified in 5.8.9.3a;

[0305] 2> If the UE acts as an L2 U2U relay UE and this destination identifies the connected L2 U2U remote UE:

[0306] 3> Consider end-to-end PC5 connection failure for end-to-end PC5 connection established through each hop PC5 link with L2 U2U remote UE;

[0307] 3> Send NotificationMessageSidelink message to peer L2U2U remote UE for end-to-end PC5 connection according to 5.8.9.10;

[0308] 3> Initiate actions related to the end-to-end PC5 connection failure as specified in 5.8.9.3b;

[0309] 5.8.9.5a Actions related to end-to-end PC5-RRC connection release performed by L2 U2U remote UE

[0310] A UE acting as a sidelink L2 U2U remote UE shall:

[0311] 1> If the end-to-end PC5-RRC connection release is requested by upper layers as specified in TS 23.304

[65] :

[0312] 2> discard the NR sidelink communication related configuration used for this end-to-end PC5-RRC connection, including the SRAP configuration;

[0313] 2> Release the end-to-end DRB (if configured) used for this end-to-end PC5-RRC connection according to clause 5.8.9.1a.1;

[0314] 2> Release the end-to-end SRB used for this end-to-end PC5-RRC connection according to clause 5.8.9.1a.3;

[0315] 2> for this end-to-end PC5-RRC connection, the end-to-end PC5-RRC connection is considered to be released;

[0316] 2> According to 5.8.9.8.2, the RemoteUEInformationSidelink message is sent to the L2 relay UE in the middle of the end-to-end PC5 connection;

[0317] […]

[0318] 5.8.9.7.1 PC5 Relay RLC Channel Release

[0319] The UE shall:

[0320] 1> If the PC5 relay RLC channel release is triggered after receiving the RRCReconfigurationSidelink message; or

[0321] 1> After receiving the RRCReconfigurationCompleteSidelink message, if the PC5 relay RLC channel release is triggered due to the configuration received in sl-ConfigDedicatedNR:

[0322] 2> For each SL-RLC-ChannelID in the sl-RLC-ChannelToReleaseList received in the sl-ConfigDedicatedNR within the RRCReconfiguration, or for each SL-RLC-ChannelID included in the received sl-RLC-ChannelToReleaseListPC5 as part of the current UE-side link configuration:

[0323] 3> Release the RLC entity and the corresponding logical channel associated with SL-RLC-ChannelID;

[0324] 1> If the PC5 relay RLC channel release is triggered by an end-to-end DRB release as specified in 5.8.9.1a.1.2:

[0325] 2> Release the RLC entity and the corresponding logical channel;

[0326] 1> If PC5 relay RLC channel release is triggered by upper layers for a specific destination as specified in 5.8.9.5 or due to sidelink RLF as specified in 5.8.9.3:

[0327] 2> Release the RLC entity and the corresponding logical channel associated with the SL-RLC-ChannelID of the specific destination;

[0328] 5.8.9.7.2 PC5 Relay RLC Channel Addition / Modification

[0329] After establishing a PC5-RRC connection between the L2 U2N relay UE and the L2 U2N remote UE, the L2U2N relay UE shall:

[0330] 1> If the SRAP entity has not yet been established, establish the SRAP entity as specified in TS 38.351

[66] ;

[0331] 1> Apply the RLC-specific configuration of SL-RLC0 as specified in clause 9.1.1.4:

[0332] 1> If the L2 U2N relay UE is in RRC_IDLE / INACTIVE state, the RLC preset configuration of SL-RLC1 as defined in clause 9.2.4 applies;

[0333] After a PC5-RRC connection is established between two UEs for L2 U2U relay operation, the UEs shall:

[0334] 1> If the SRAP entity has not yet been established, establish the SRAP entity as specified in TS 38.351

[66] ;

[0335] 1> Apply the RLC-specific configuration of SL-U2U-RLC as specified in clause 9.1.1.4;

[0336] For L2 U2U relay operation in RRC_IDLE / RRC_INACTVE or out of coverage, PC5 relay RLC channel addition / modification may be triggered due to the addition / modification / release of end-to-end SL DRBs. The source L2 U2U remote UE and L2 U2U relay UE derive the corresponding PC5 relay RLC channels based on SIB12 / pre-configuration as follows:

[0337] -The source L2 U2U remote UE derives the configuration of the PC5 relay RLC channel (i.e., the first-hop PC5 relay RLC channel) between the L2 U2U source remote UE and the L2U2U relay UE by aggregating the split QoS profile of the first hop into a per-SLRB level QoS profile for each end-to-end SL DRB, and considering the SL-RLC-Config (linked to the SL-RadioBearerConfig matching the per-SLRB level QoS profile) as the first-hop RLC channel configuration.

[0338] -By aggregating the split QoS profiles of the second hop into a per-SLRB-level QoS profile for each end-to-end SL DRB, and considering the SL-RLC-Config (linked to the SL-RadioBearerConfig matching the per-SLRB-level QoS profile) as the second-hop RLC channel configuration, the L2U2U relay UE derives the configuration of the PC5 relay RLC channel (i.e., the second-hop PC5 relay RLC channel) between the L2 U2U relay UE and the target L2U2U source remote UE.

[0339] The UE shall:

[0340] 1> If the PC5 relay RLC channel addition / modification is triggered by receiving an RRCReconfigurationSidelink message; or

[0341] 1> After receiving the RRCReconfigurationCompleteSidelink message, if PC5 relay RLC channel addition / modification is triggered due to the configuration received in sl-ConfigDedicatedNR; or

[0342] 1> After receiving the RRCReconfigurationCompleteSidelink message, if PC5 relay RLC channel addition / modification is triggered for the end-to-end sidelink DRB based on the configuration in SIB12 or SidelinkPreconfigNR:

[0343] 2> if the current configuration contains a PC5 relay RLC channel with the received sl-RLC-ChannelID or sl-RLC-ChannelID-PC5; or

[0344] 2> If the configuration in SIB12 or SidelinkPreconfigNR has been updated, derive the PC5 relay RLC channel based on the configuration:

[0345] 3> Reconfigure the sidelink RLC entity according to the received sl-RLC-Config or sl-RLC-ConfigPC5;

[0346] 3> Reconfigure the sidelink MAC entity with the logical channel according to the received sl-MAC-LogicalChannelConfig or sl-MAC-LogicalChannelConfigPC5;

[0347] 2> Otherwise (PC5 relay RLC channel with received sl-RLC-ChannelID or sl-RLC-ChannelID-PC5 has not been configured before):

[0348] 3> Establish a sidelink RLC entity according to the received sl-RLC-Config (in sl-ConfigDedicatedNR or SIB12 or SidelinkPreconfigNR) or sl-RLC-ConfigPC5;

[0349] 3> Configure the sidelink MAC entity with the logical channel according to the received sl-MAC-LogicalChannelConfig or sl-MAC-LogicalChannelConfigPC5.

[0350] […]

[0351] 5.8.9.8 Remote UE Information

[0352] 5.8.9.8.1 Overview

[0353] [3GPP R2-2402042 titled "Remote UE Information" Figure 5 .8.9.8.1-1 is reproduced as Figure 9 ]

[0354] This procedure is used by an L2 U2N remote UE in RRC_IDLE / RRC_INACTIVE to notify required SIBs / posSIBs, provide paging related information to a connected L2 U2N relay UE, request SFN-DFN offset from a connected L2 U2N relay UE, and trigger an L2 U2N relay UE in RRC_IDLE / RRC_INACTIVE to enter RRC_CONNECTED during indirect path addition / change in MP operation. This procedure is also used by an L2 U2U remote UE to send end-to-end PC5 connection release / failure related information to an L2 U2U relay UE.

[0355] This procedure is used by an L2 U2N remote UE in RRC_CONNECTED to request an SFN-DFN offset from a connected L2 U2N relay UE.

[0356] NOTE: L2 U2N remote UE does not require MIB.

[0357] 5.8.9.8.2 Actions related to the delivery of RemoteUEInformationSidelink message

[0358] When entering RRC_IDLE or RRC_INACTIVE, or when any of the information in RemoteUEInformationSidelink changes while in RRC_IDLE or RRC_INACTIVE, the L2U2N remote UE shall:

[0359] 1> If the UE has SIB request information to provide (e.g. the UE has not previously stored a valid version of the SIB according to clause 5.2.2.2.1 among one or several required SIBs according to clause 5.2.2.1 and the requested SIB has not been indicated to the L2 U2N relay UE in the RemoteUEInformationSidelink message):

[0360] 2> Include sl-RequestedSIB-List in RemoteUEInformationSidelink to indicate the requested SIB;

[0361] 1> If the UE has not stored a valid version according to clause 5.2.2.2.1 of one or several posSIBs that the UE needs for positioning operations and has not previously indicated the requested posSIBs to the L2 U2N relay UE in a RemoteUEInformationSidelink message, and the connected L2 U2N relay UE sets posSIB-ForwardingSupported to supported:

[0362] 2> Include sl-RequestedPosSIB-List in RemoteUEInformationSidelink to indicate the requested posSIB;

[0363] 1> If the UE requires SFN-DFN offset based on a request from upper layers and the connected L2U2N relay UE sets sfn-DFN-OffsetSupported to supported:

[0364] 2> Set sl-SFN-DFN-OffsetRequested to true;

[0365] 1> If the UE has paging related information to provide (for example, the UE has not previously sent sl-PagingInfo-RemoteUE in the RemoteUEInformationSidelink message to the L2U2N relay UE), then sl-PagingInfo-RemoteUE is set as follows:

[0366] 2> If the L2 U2N remote UE is in RRC_IDLE:

[0367] 3> Include ng-5G-S-TMSI in sl-PagingIdentityRemoteUE;

[0368] 3> If the UE-specific DRX cycle is configured by upper layers, set sl-PagingCycleRemoteUE to the value of the UE-specific Uu DRX cycle configured by upper layers;

[0369] 2> Else if L2 U2N remote UE is in RRC_INACTIVE:

[0370] 3> Include ng-5G-S-TMSI and fullI-RNTI in sl-PagingIdentityRemoteUE;

[0371] 3> If the UE-specific DRX cycle is configured by upper layers,

[0372] 4> Set sl-PagingCycleRemoteUE to the minimum value of the UE-specific Uu DRX cycle (configured by upper layers and configured by RRC);

[0373] 3> Otherwise:

[0374] 4> Set sl-PagingCycleRemoteUE to the value of the UE-specific DRX cycle configured via RRC;

[0375] 1> Submit the RemoteUEInformationSidelink message to the lower layer for transmission;

[0376] When entering RRC_CONNECTED, if the L2 U2N remote UE has sent sl-RequestedSIB-List, sl-RequestedPosSIB-List and / or sl-PagingInfo-RemoteUE, the L2U2N remote UE shall:

[0377] 1> If previously requested, set sl-RequestedSIB-List to the value release;

[0378] 1> If previously requested, set sl-RequestedPosSIB-List to the value released;

[0379] 1> If it has been sent previously, set sl-PagingInfo-RemoteUE to the value released;

[0380] 1> Submit the RemoteUEInformationSidelink message to the lower layer for transmission;

[0381] After any required change of SFN-DFN offset while in RRC_CONNECTED, the L2 U2N remote UE shall:

[0382] 1> If the UE requires SFN-DFN offset based on a request from upper layers and the connected L2U2N relay UE sets sfn-DFN-OffsetSupported to supported:

[0383] 2> Set sl-SFN-DFN-OffsetRequested to true;

[0384] 1> Submit the RemoteUEInformationSidelink message to the lower layer for transmission;

[0385] A L2 U2N remote UE in RRC_CONNECTED state shall:

[0386] 1> If the UE is configured with sl-IndirectPathAddChange set to SET and is not configured with split SRB1 with replication:

[0387] 2> include connectionForMP;

[0388] 2> Submit the RemoteUEInformationSidelink message to the lower layer for transmission;

[0389] L2 U2U remote UE shall:

[0390] 1>After the end-to-end PC5-RRC connection is released; or

[0391] 1> After an end-to-end PC5-RRC connection failure due to T400 expiration or SL-SRB2 or SL-SRB3 integrity check failure:

[0392] 2> include sl-DestinationIdentityRemoteUE-r18;

[0393] 2> Submit the RemoteUEInformationSidelink message to the lower layer for transmission;

[0394] 5.8.9.8.3 L2 U2N / U2U relay UE receives RemoteUEInformationSidelink message The L2 U2N relay UE shall:

[0395] 1> If RemoteUEInformationSidelink contains sl-PagingInfo-RemoteUE:

[0396] 2> if the UE is in RRC_CONNECTED on an active BWP, where the configured common search space includes pagingSearchSpace; or

[0397] 2> If the UE is in RRC_IDLE or RRC_INACTIVE:

[0398] 3> If sl-PagingInfo-RemoteUE is set to settings:

[0399] 4> Monitor paging messages at the paging occasion of the L2 U2N remote UE calculated based on the sl-PagingIdentityRemoteUE and sl-PagingCycleRemoteUE contained in sl-PagingInfo-RemoteUE;

[0400] 3> Otherwise (sl-PagingInfo-RemoteUE is set to release):

[0401] 4> Stop monitoring paging messages during the paging period of the L2 U2N remote UE;

[0402] 4> Release the paging information received in sl-PagingInfo-RemoteUE;

[0403] 2> Otherwise (UE is in RRC_CONNECTED on an active BWP without configured pagingSearchSpace):

[0404] 3> If sl-PagingInfo-RemoteUE is set to settings:

[0405] 4> Include the received sl-PagingIdentityRemoteUE in the SidelinkUEInformationNR message and perform sidelink UE information transmission according to 5.8.3;

[0406] 3> Otherwise (sl-PagingInfo-RemoteUE is set to release):

[0407] 4> According to 5.8.3, initiate the transmission of the SidelinkUEInformationNR message to release the sl-PagingIdentityRemoteUE in the SidelinkUEInformationNR message;

[0408] 4> Release the paging information received in sl-PagingInfo-RemoteUE;

[0409] 1> If RemoteUEInformationSidelink contains sl-RequestedSIB-List:

[0410] 2> If sl-RequestedSIB-List is set to set:

[0411] 3> If the L2 U2N relay UE has not stored a valid version of the SIB indicated in the sl-RequestedSIB-List:

[0412] 4>According to 5.2.2, obtain the system information indicated in sl-RequestedSIB-List;

[0413] 3>Perform Uu message delivery procedures according to 5.8.9.9;

[0414] 2> If sl-RequestedSIB-List is set to release:

[0415] 3> Release the receive SIB request in sl-RequestedSIB-List;

[0416] 1> If RemoteUEInformationSidelink contains sl-RequestedPosSIB-List:

[0417] 2> If sl-RequestedPosSIB-List is set to set:

[0418] 3> If the L2 U2N relay UE has not stored a valid version of the posSIB indicated in the sl-RequestedPosSIB-List:

[0419] 4>According to 5.2.2, obtain the positioning system information indicated in sl-RequestedPosSIB-List;

[0420] 3>Perform Uu message delivery procedures according to 5.8.9.9;

[0421] 2> If sl-RequestedPosSIB-List is set to release:

[0422] 3> Release the received posSIB requests in sl-RequestedPosSIB-List.

[0423] 1> If RemoteUEInformationSidelink contains connectionForMP:

[0424] 2> If the L2 U2N relay UE is in RRC_IDLE:

[0425] 3> Initiate RRC connection establishment as specified in 5.3.3;

[0426] 2> Otherwise if the L2 U2N relay UE is in RRC_INACTIVE:

[0427] 3> Initiate RRC connection recovery as specified in 5.3.13;

[0428] L2 U2U relay UE shall:

[0429] 1> If RemoteUEInformationSidelink contains sl-DestinationIdentityRemoteUE:

[0430] 2> consider the end-to-end PC5 connection release for the end-to-end PC5 connection between the L2 U2U remote UE and the peer L2 U2U remote UE identified by sl-DestinationIdentityRemoteUE;

[0431] 2> Initiate end-to-end PC5 connection failure / release related actions as specified in 5.8.9.3b;

[0432] […]

[0433] 5.8.9.10 Notification Message

[0434] 5.8.9.10.1 Overview

[0435] [3GPP R2-2402042 titled "Notification Messages in Sidelink" Figure 5 .8.9.8.1-1 is reproduced as Figure 10 ]

[0436] This procedure is used by a U2N Relay UE to send notifications to a connected U2N Remote UE, or by a L2 U2U Relay UE to send notifications to a L2 U2U Remote UE for an end-to-end PC5 connection when the conditions as specified in 5.8.9.10.2 are met for another hop between the L2 U2U Relay UE and the peer L2 U2U Remote UE.

[0437] 5.8.9.10.2 Initiation

[0438] The relay UE may initiate the procedure when one of the following conditions is met:

[0439] 1> If the UE acts as a U2N relay UE:

[0440] 2> after the Uu RLF as specified in 5.3.10;

[0441] 2>After receiving RRCReconfiguration containing reconfigurationWithSync;

[0442] 2>After cell reselection;

[0443] 2> after an RRC connection failure of the L2 U2N relay UE including an RRC Connection Reject as specified in 5.3.3.5 and 5.3.13.10, and after T300 expires as specified in 5.3.3.7 and RRC recovers the failure as specified in 5.3.13.5;

[0444] 1> If the UE acts as an L2 U2U relay UE:

[0445] 2> After detecting PC5 RLF for another hop between the L2 U2U relay UE and the L2 U2U remote UE as specified in 5.8.9.3;

[0446] 2> After the PC5-RRC connection for each hop link between the L2 U2U relay UE and the L2 U2U remote UE is released as specified in 5.8.9.5;

[0447] 5.8.9.10.3 Actions related to the delivery of NotificationMessageSidelink messages

[0448] The relay UE shall set the indication type as follows:

[0449] 1> If the UE acts as a U2N relay UE:

[0450] 2> If the UE initiates the transmission of the NotificationMessageSidelink message due to Uu RLF:

[0451] 3> Set indicationType to relayUE-Uu-RLF;

[0452] 2> Otherwise, if the UE initiates the transmission of the NotificationMessageSidelink message due to synchronous reconfiguration:

[0453] 3> Set indicationType to relayUE-HO;

[0454] 2> Otherwise, if the UE initiates the transmission of the NotificationMessageSidelink message due to cell reselection:

[0455] 3> Set indicationType to relayUE-CellReselection;

[0456] 2> If the UE initiates the transmission of the NotificationMessageSidelink message due to a Uu RRC connection establishment / recovery failure:

[0457] 3> Set indicationType to relayUE-Uu-RRC-Failure;

[0458] 2>Submit the NotificationMessageSidelink message to the lower layer for transmission.

[0459] 1> If the UE acts as an L2 U2U relay UE:

[0460] 2> If the UE initiates the transmission of NotificationMessageSidelink message due to PC5 RLF with L2 U2U remote UE:

[0461] 2> If the UE initiates the transmission of the NotificationMessageSidelink message due to the release of the PC5-RRC connection of each hop link between the L2 U2U relay UE and the L2 U2U remote UE:

[0462] 3> Set sl-IndicationType to relayUE-PC5-RLF;

[0463] 3> Set sl-DestinationIdentityRemoteUE to the associated destination of the L2 U2U remote UE;

[0464] 3>Submit the NotificationMessageSidelink message to the lower layer for transmission;

[0465] 5.8.9.10.4 Actions related to the reception of NotificationMessageSidelink messages

[0466] After receiving the NotificationMessageSidelink, the remote UE shall:

[0467] 1> If the UE acts as a U2N remote UE:

[0468] 2> If indicationType is included:

[0469] 3> If the UE is an L2 U2N remote UE in RRC_CONNECTED:

[0470] 4> If MP is configured and MCG transmission is not suspended (i.e., direct path);

[0471] 5>If indicationType is relayUE-HO;

[0472] 6> Pause indirect path transmission;

[0473] 5> Otherwise:

[0474] 6> Initiate the indirect path failure information procedure as specified in 5.7.3c to report the indirect path failure;

[0475] 4> Otherwise if T301 is not running, initiate the RRC connection re-establishment procedure as specified in 5.3.7;

[0476] 3> Otherwise (the UE is a L3 U2N remote UE or L2 U2N remote UE in RRC_IDLE or RRC_INACTIVE):

[0477] 4> If you decide to release the PC5-RRC connection with the U2N relay UE:

[0478] 5> Instruct the upper layer to trigger the release of PC5 unicast link;

[0479] 4> Otherwise (i.e., maintain PC5 RRC connection):

[0480] 5> If the UE is an L2 U2N remote UE and indicationType is relayUE-HO or relayUE-CellReselection:

[0481] 6> Consider cell reselection;

[0482] NOTE 1: For L3 U2N remote UE or L2 U2N remote UE in RRC_IDLE or RRC_INACTIVE, it is up to the remote UE implementation to decide whether to release or maintain the PC5 unicast link.

[0483] NOTE 2: If the L2 U2N remote UE has not released the PC5 unicast link on the source side during the indirect-to-direct path handover, i.e., while T304 is running, it may ignore the NotificationMessageSidelink.

[0484] 1> If the UE acts as an L2 U2U remote UE:

[0485] 2> If sl-IndicationType is relayUE-PC5-RLF:

[0486] 3> Indicate the PC5 RLF received from the L2 U2U relay UE to the upper layers of the indicated L2 U2U remote UE based on the received sl-DestinationIdentityRemoteUE;

[0487] 3> consider end-to-end PC5 connection failure for the end-to-end PC5 connection over each hop of the PC5 link between the L2 U2U relay UE and the L2 U2U remote UE identified by sl-DestinationIdentityRemoteUE;

[0488] 3> Perform the actions related to the end-to-end PC5 connection failure as specified in 5.8.9.3a;

[0489] NOTE 3: Following the PC5 RLF indication received from the U2U relay UE, upper layers are reached on whether to trigger U2U relay reselection and whether to maintain or release the PC5 link with the U2U relay UE.

[0490] […]

[0491] Inter-UE (U2U) relay was introduced into 3GPP Release 18, where a relay UE is used to support communication between two remote UEs when they cannot communicate directly with each other due to being out of radio coverage. The relay UE needs to establish a PC5 RRC connection (or PC5 unicast link) with each of the source remote UE (e.g., the first PC5 hop) and the target remote UE (e.g., the second PC5 hop). In addition, an end-to-end PC5 RRC connection can be established between the two remote UEs for Layer 2 (L2) U2U relay, such as Figure 11 , which illustrates a PC5 RRC connection for inter-UE relay according to an exemplary embodiment.

[0492] In addition, a single source remote UE can communicate with multiple target remote UEs via the same relay UE. In this case, the PC5 RRC connection between the source remote UE and the relay UE can be shared by multiple end-to-end PC5 RRC connections between the source remote UE and multiple target remote UEs. Furthermore, multiple source remote UEs can communicate with a single target remote UE via the same relay UE, and the PC5 RRC connection between the target remote UE and the relay UE can be shared by multiple end-to-end PC5 RRC connections between the multiple source remote UEs and the target remote UEs. Figure 12 It is shown that a plurality of source remote UEs communicate with a plurality of target remote UEs via a relay UE according to an exemplary embodiment.

[0493] For an L2 remote UE connected to another L2 remote UE via an L2 relay UE, the end-to-end QoS requirements for relay services between peer L2 remote UEs can be met by corresponding QoS control for the PC5 RRC connection between the L2 source remote UE and the L2 relay UE (i.e., first-hop PC5 QoS control) and QoS control for the PC5 RRC connection between the L2 relay UE and the L2 target remote UE (i.e., second-hop PC5 QoS control).

[0494] To achieve this, the source remote UE and the target remote UE may first negotiate the end-to-end QoS requirements for the new PC5 QoS flow. Then, the source remote UE may provide the end-to-end QoS requirements (e.g., QoS profile) to the relay UE (e.g., via a UE Information Request sidelink message) so that the relay UE can split the packet delay budget (PDB) into one packet delay budget (PDB) value for the first hop and another PDB value for the second hop. The relay UE may then provide the split PDB value of the first hop to the source remote UE (e.g., via a UE information response sidelink message), so that the source remote UE (i.e., Tx UE) may determine the end-to-end (E2E) SL DRB configuration and PC5 relay RLC channel configuration (for transmitting data packets for the PC5 QoS flow for the target remote UE to the relay UE via the first hop) based at least on the split PDB value received from the relay UE, and may then provide the receive (Rx) RLC parameters of the PC5 relay RLC channel configuration to the relay UE (i.e., Rx UE) via an RRC reconfiguration sidelink message, so that the relay UE may receive data packets of the PC5 QoS flow from the source remote UE on the PC5 relay RLC channel. In addition, the relay UE (i.e., Tx UE) can determine another PC5 relay RLC channel configuration for the second hop based on another split PDB value of the second hop (e.g., per-SLRB QoS profile), and then provide the Rx RLC parameters of the PC5 relay RLC channel configuration to the target remote UE (i.e., Tx UE) via another RRC reconfiguration sidelink message, so as to forward the data packets of the PC5 QoS flow to the target remote UE on the PC5 relay RLC channel through the second hop.

[0495] Essentially, different E2E SL-DRBs destined for the same target remote UE or different target remote UEs can be multiplexed by the source remote UE onto the same PC5 relay RLC channel for transmission. Therefore, the end-to-end PC5 radio bearer ID (E2E SL DRB ID), the local UE ID of the source remote UE, and the local UE ID of the target remote UE are included in the header of the SRAP PDU (used to transmit a data packet) to enable the relay UE to determine the egress PC5 relay RLC channel to use for forwarding the data packet, and also to enable the target remote UE to associate received data packets for a specific PDCP entity with the correct E2E SL DRB for the target remote UE. To support this, for each target remote UE, the source remote UE needs to maintain a mapping between the E2E SL DRB and the egress PC5 relay RLC channel over the first hop between the source remote UE and the relay UE. Furthermore, for each source-target remote UE pair, the relay UE needs to maintain a mapping between the E2E SL DRB and the egress PC5 relay RLC channel over the second hop between the relay UE and the target remote UE. The local UE ID of the remote UE can be assigned by the relay UE. Figure 16.12.7-1 of 3GPP TS 38.300 V18.0.0 (reproduced as Figure 7 ) illustrates the above concept.

[0496] According to clause 5.8.9.8.1 of 3GPP R2-2402042, an L2 U2U remote UE shall send a RemoteUEInformationSidelink message to an L2 U2U relay UE following an end-to-end PC5-RRC connection release or end-to-end PC5-RRC connection failure due to T400 expiration or integrity check failure of SL-SRB2 or SL-SRB3. The RemoteUEInformationSidelink message may include an sl-DestinationIdentityRemoteUE indicating the peer L2 U2U remote UE following the end-to-end PC5 connection release or failure. In response to receiving this message, the L2 U2U relay UE shall consider an end-to-end PC5 connection release for the end-to-end PC5 connection between the L2 U2U remote UE and the peer L2 U2U remote UE identified by sl-DestinationIdentityRemoteUE and initiate end-to-end PC5 connection failure / release related actions as specified in clause 5.8.9.3b. According to clause 5.8.9.3b, the L2 U2U relay UE shall consider the end-to-end DRB for this end-to-end PC5 connection released upon receipt of the RemoteUEInformationSidelink message, which shall then trigger a sidelink DRB release as specified in clause 5.8.9.1a.1.1. When the end-to-end DRB is released, if there are no other end-to-end sidelink DRBs associated with the PC5 relay RLC channel associated with the released end-to-end DRB, the L2 U2U relay UE shall perform a PC5 relay RLC channel release for this PC5 relay RLC channel according to clause 5.8.9.7.1. As described in clause 5.8.9.7.1, the L2 U2U relay UE shall release the RLC entity and corresponding logical channels associated with the PC5 relay RLC channel.

[0497] It is possible that when an end-to-end PC5-RRC connection release or failure occurs, the PC5 RRC connection between the L2 U2U remote UE and the L2 U2U relay UE may still be good (or available) for operation. In this case, it is inappropriate for the L2 U2U relay UE to suddenly release the PC5 relay RLC channel used for transmission from the L2 U2U relay UE to the L2 U2U remote UE without notifying the L2 U2U remote UE, because only the relay UE knows the SL DRB-to-PC5 relay RLC channel mapping of the PC5 relay RLC channel used for transmission from the L2 U2U relay UE to the L2 U2U remote UE, and therefore the L2 U2U remote UE needs to rely on the notification of the L2 U2U relay UE for releasing the PC5 relay RLC channel.

[0498] In other words, the L2 U2U relay UE is required to send an RRCReconfigurationSidelink message to the L2 U2U remote UE to notify the L2 U2U remote UE to release the PC5 relay RLC channel. The L2 U2U relay UE should then release the PC5 relay RLC channel after receiving the RRCReconfigurationCompleteSidelink message from the L2 U2U remote UE. Similarly, if there are no other end-to-end sidelink DRBs associated with the PC5 relay RLC channel used for transmission from the L2 U2U relay UE to the peer L2 U2U remote UE, the relay UE may do the same for this PC5 relay RLC channel, allowing the peer L2 U2U remote UE to correspondingly release the PC5 relay RLC channel associated with the released end-to-end DRB. Figure 13 An example of the above concept is shown with respect to the release or failure of an end-to-end PC5 connection according to an exemplary embodiment.

[0499] Figure 14 14 is a flow chart 1400 for a relay user equipment (UE). In step 1405, the relay UE establishes a first PC5 radio resource control (RRC) connection (or PC5 radio link) with a first remote UE. In step 1410, the relay UE establishes a second PC5 RRC connection with a second remote UE. In step 1415, the relay UE transmits a first RRC reconfiguration sidelink message to the first remote UE, wherein the first RRC reconfiguration sidelink message includes a configuration of a first PC5 relay radio link control (RLC) channel associated with at least one end-to-end sidelink data radio bearer (DRB) established between the first remote UE and the second remote UE. In step 1420, the relay UE receives a PC5 RRC message from the first remote UE, wherein the PC5 RRC message includes a destination identity of the second remote UE to indicate an end-to-end PC5 connection release or failure. In step 1425, if there are no other end-to-end sidelink DRBs associated with the first PC5 relay RLC channel, the relay UE transmits a second RRC reconfiguration sidelink message to the first remote UE, wherein the second RRC reconfiguration sidelink message includes a first list of sidelink RLC channels to be released, and the first list includes the identity of the first PC5 relay RLC channel. In step 1430, the relay UE releases the first PC5 relay RLC channel after receiving the first RRC reconfiguration complete sidelink message from the first remote UE.

[0500] In one embodiment, the relay UE may transmit a third RRC reconfiguration sidelink message to the second remote UE, wherein the third RRC reconfiguration sidelink message includes the configuration of a second PC5 relay RLC channel associated with at least one end-to-end sidelink DRB established between the first remote UE and the second remote UE. If there are no other end-to-end sidelink DRBs associated with the second PC5 relay RLC channel, the relay UE may transmit a fourth RRC reconfiguration sidelink message to the second remote UE, wherein the fourth RRC reconfiguration sidelink message includes a second list of sidelink RLC channels to be released, and the second list includes the identity of the second PC5 relay RLC channel. The relay UE may release the second PC5 relay RLC channel after receiving the second RRC reconfiguration complete sidelink message from the second remote UE. The relay UE may support the first remote UE communicating with the second remote UE via the relay UE.

[0501] In one embodiment, the PC5 RRC message may be a Remote UE Information Sidelink message. The destination identity may be the Layer 2 identity of the second remote UE. The end-to-end PC5 connection release may occur due to a request from an upper layer in the first remote UE. The end-to-end PC5 connection failure may occur due to T400 expiration or an integrity check failure of SL-SRB2 or SL-SRB3 in the first remote UE. Additionally, the relay UE may be a Layer 2 inter-UE relay UE.

[0502] Return Reference Figure 3 and 4, in an exemplary embodiment from the perspective of a relay UE. The relay UE 300 includes program code 312 stored in a memory 310. The CPU 308 may execute the program code 312 to enable the relay UE to: (i) establish a first PC5 RRC connection or PC5 radio link with a first remote UE, (ii) establish a second PC5 RRC connection with a second remote UE, (iii) transmit a first RRC reconfiguration sidelink message to the first remote UE, wherein the first RRC reconfiguration sidelink message includes a configuration of a first PC5 relay RLC channel associated with at least one end-to-end sidelink DRB established between the first remote UE and the second remote UE, (iv) receive a PC5 RRC message from the first remote UE, wherein the PC5 The RRC message includes a destination identity of the second remote UE to indicate an end-to-end PC5 connection release or failure, (v) if there are no other end-to-end sidelink DRBs associated with the first PC5 relay RLC channel, transmitting a second RRC reconfiguration sidelink message to the first remote UE, wherein the second RRC reconfiguration sidelink message includes a first list of sidelink RLC channels to be released, and the first list includes the identity of the first PC5 relay RLC channel, and (vi) releasing the first PC5 relay RLC channel after receiving the first RRC reconfiguration complete sidelink message from the first remote UE. In addition, the CPU 308 can execute the program code 312 to perform all of the above actions and steps or other actions and steps described herein.

[0503] Various aspects of the present disclosure have been described above. It should be understood that the teachings herein can be implemented in a wide variety of forms, and any specific structure, function, or both disclosed herein are merely representative. Based on the teachings herein, those skilled in the art will appreciate that the aspects disclosed herein can be implemented independently of any other aspects, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement a device or practice a method. In addition, other structures, functionality, or structures and functionality other than or different from the one or more aspects described herein can be used to implement such a device or practice such a method. As examples of some of the above concepts, in some aspects, parallel channels can be established based on pulse repetition frequency. In some aspects, parallel channels can be established based on pulse position or offset. In some aspects, parallel channels can be established based on time hopping sequences. In some aspects, parallel channels can be established based on pulse repetition frequency, pulse position or offset, and time hopping sequences.

[0504] Those skilled in the art will understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0505] Those skilled in the art will further appreciate that the various illustrative logical blocks, modules, processors, components, circuits, and algorithm steps described in connection with the various aspects disclosed herein may be implemented as electronic hardware (e.g., a digital implementation, an analog implementation, or a combination of the two, which may be designed using source decoding or some other technique), various forms of program or design code incorporating instructions (which, for convenience, may be referred to herein as "software" or "software modules"), or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art may implement the described functionality in different ways for each specific application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

[0506] In addition, the various illustrative logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented within or performed by an integrated circuit ("IC"), an access terminal, or an access point. The IC may include a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, electrical components, optical components, mechanical components, or any combination thereof designed to perform the functions described herein, and may execute code or instructions residing within the IC, external to the IC, or both. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0507] It should be understood that any specific order or hierarchy of steps in any disclosed process is an example of a sample approach. It should be understood that based on design preferences, the specific order or hierarchy of steps in a process can be rearranged while remaining within the scope of the present disclosure. The accompanying method claims present elements of the various steps in a sample order and are not intended to be limited to the specific order or hierarchy presented.

[0508] The steps of the methods or algorithms described in conjunction with the various aspects disclosed herein can be implemented directly in hardware, in software modules executed by a processor, or in a combination of the two. The software modules (e.g., containing executable instructions and associated data) and other data can reside in a data storage device, such as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of computer-readable storage medium known in the art. A sample storage medium can be coupled to a machine such as a computer / processor (for convenience, the machine may be referred to herein as a "processor") so that the processor can read information (e.g., code) from the storage medium and write information to the storage medium. The sample storage medium can be integrated with the processor. The processor and storage medium can reside in an ASIC. The ASIC can reside in a user device. In an alternative, the processor and storage medium can reside in the user device as discrete components. In addition, in some aspects, any suitable computer program product can include a computer-readable medium that includes code related to one or more of the various aspects of the present disclosure. In some aspects, the computer program product can include packaging materials.

[0509] Although the present invention has been described in conjunction with various aspects, it will be understood that the invention is capable of further modification. This application is intended to cover any variations, uses, or adaptations of the invention that generally follow the principles of the invention and include such departures from the present disclosure as come within the scope of known and customary practice in the art to which the invention pertains.

Claims

1. A method for relaying user equipment, characterized in that: The method comprises: The relay user equipment establishes a first PC5 radio resource control connection with the first remote user equipment; The relay user equipment establishes a second PC5 radio resource control connection with the second remote user equipment; the relay user equipment transmitting a first radio resource control reconfiguration sidelink message to the first remote user equipment, wherein the first radio resource control reconfiguration sidelink message includes a configuration of a first PC5 relay radio link control channel associated with at least one end-to-end sidelink data radio bearer established between the first remote user equipment and the second remote user equipment; The relay user equipment receives a PC5 radio resource control message from the first remote user equipment, wherein the PC5 radio resource control message includes a destination identity of the second remote user equipment to indicate an end-to-end PC5 connection release or failure; if there are no other end-to-end sidelink data radio bearers associated with the first PC5 relay radio link control channel, the relay user equipment transmitting a second radio resource control reconfiguration sidelink message to the first remote user equipment, wherein the second radio resource control reconfiguration sidelink message includes a first list of sidelink radio link control channels to be released, and the first list includes an identity of the first PC5 relay radio link control channel; and The relay user equipment releases the first PC5 relay radio link control channel after receiving a first radio resource control reconfiguration complete sidelink message from the first remote user equipment.

2. The method according to claim 1, characterized in that The method further comprises: The relay user equipment transmits a third radio resource control reconfiguration sidelink message to the second remote user equipment, wherein the third radio resource control reconfiguration sidelink message includes a configuration of a second PC5 relay radio link control channel associated with at least one end-to-end sidelink data radio bearer established between the first remote user equipment and the second remote user equipment.

3. The method according to claim 2, characterized in that If there are no other end-to-end sidelink data radio bearers associated with the second PC5 relay radio link control channel, the relay user equipment transmits a fourth radio resource control reconfiguration sidelink message to the second remote user equipment, wherein the fourth radio resource control reconfiguration sidelink message includes a second list of sidelink radio link control channels to be released, and the second list includes the identity of the second PC5 relay radio link control channel.

4. The method according to claim 3, characterized in that The relay user equipment releases the second PC5 relay radio link control channel after receiving a second radio resource control reconfiguration complete sidelink message from the second remote user equipment.

5. The method according to claim 1, wherein The relay user equipment supports the first remote user equipment to communicate with the second remote user equipment via the relay user equipment.

6. The method according to claim 1, characterized in that The PC5 radio resource control message is a remote user equipment information side link message.

7. The method according to claim 1, characterized in that The destination identity is a layer 2 identity of the second remote user equipment.

8. The method according to claim 1, characterized in that The end-to-end PC5 connection release occurs due to an upper layer request in the first remote user equipment.

9. The method according to claim 1, characterized in that The end-to-end PC5 connection failure occurs due to expiration of T400 in the first remote user equipment or failure of integrity check of SL-SRB2 or SL-SRB3.

10. The method according to claim 1, characterized in that The relay user equipment is a layer 2 inter-user equipment relay user equipment.

11. A relay user equipment, characterized in that: The relay user equipment includes: control circuit; a processor installed in the control circuit; and a memory installed in the control circuit and operatively coupled to the processor; wherein the processor is configured to execute program code stored in the memory to: establishing a first PC5 radio resource control connection with a first remote user equipment; establishing a second PC5 radio resource control connection with a second remote user equipment; transmitting a first radio resource control reconfiguration sidelink message to the first remote user equipment, wherein the first radio resource control reconfiguration sidelink message includes a configuration of a first PC5 relay radio link control channel associated with at least one end-to-end sidelink data radio bearer established between the first remote user equipment and the second remote user equipment; receiving a PC5 radio resource control message from the first remote user equipment, wherein the PC5 radio resource control message includes a destination identity of the second remote user equipment to indicate an end-to-end PC5 connection release or failure; if there are no other end-to-end sidelink data radio bearers associated with the first PC5 relay radio link control channel, transmitting a second radio resource control reconfiguration sidelink message to the first remote user equipment, wherein the second radio resource control reconfiguration sidelink message includes a first list of sidelink radio link control channels to be released, and the first list includes an identity of the first PC5 relay radio link control channel; and The first PC5 relay radio link control channel is released after receiving a first radio resource control reconfiguration complete sidelink message from the first remote user equipment.

12. The relay user equipment according to claim 11, characterized in that The processor is further configured to execute program code stored in the memory to: transmitting a third radio resource control reconfiguration sidelink message to the second remote user equipment, wherein the third radio resource control reconfiguration sidelink message includes a configuration of a second PC5 relay radio link control channel associated with at least one end-to-end sidelink data radio bearer established between the first remote user equipment and the second remote user equipment.

13. The relay user equipment according to claim 12, characterized in that: If there are no other end-to-end sidelink data radio bearers associated with the second PC5 relay radio link control channel, the relay user equipment transmits a fourth radio resource control reconfiguration sidelink message to the second remote user equipment, wherein the fourth radio resource control reconfiguration sidelink message includes a second list of sidelink radio link control channels to be released, and the second list includes the identity of the second PC5 relay radio link control channel.

14. The relay user equipment according to claim 13, characterized in that: The relay user equipment releases the second PC5 relay radio link control channel after receiving a second radio resource control reconfiguration complete sidelink message from the second remote user equipment.

15. The relay user equipment according to claim 11, characterized in that: The relay user equipment supports the first remote user equipment to communicate with the second remote user equipment via the relay user equipment.

16. The relay user equipment according to claim 11, characterized in that The PC5 radio resource control message is a remote user equipment information side link message.

17. The relay user equipment according to claim 11, characterized in that The destination identity is a layer 2 identity of the second remote user equipment.

18. The relay user equipment according to claim 11, characterized in that: The end-to-end PC5 connection release occurs due to an upper layer request in the first remote user equipment.

19. The relay user equipment according to claim 11, characterized in that The end-to-end PC5 connection failure occurs due to expiration of T400 in the first remote user equipment or failure of integrity check of SL-SRB2 or SL-SRB3.

20. The relay user equipment according to claim 11, characterized in that The relay user equipment is a layer 2 inter-user equipment relay user equipment.

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