Method and device for connecting to another remote user device via a relay user device

Abstract

The present invention discloses a method and apparatus for connecting to another remote user equipment via a relay user equipment. The method includes a first user equipment connecting to a second user equipment via a relay user equipment, wherein a first PC5 unicast link is established between the first user equipment and the relay user equipment. The method further includes the first user equipment transmitting a link modification request message to the relay user equipment, wherein the link modification request message includes third user information of a third user equipment. The method further includes the first user equipment receiving a link modification acceptance message from the relay user equipment.

Description

Technical Field

[0001] The present disclosure generally relates to wireless communication networks, and more particularly, to methods and apparatuses for connecting to another remote UE via a relay UE in a wireless communication system. Background Art

[0002] With the rapid growth in the demand for delivering large amounts of data to and from mobile communication devices, traditional mobile voice communication networks have evolved into networks that communicate Internet Protocol (IP) data packets. Such IP data packet communication can provide IP-borne voice, multimedia, multicast, and on-demand communication services to users of mobile communication devices.

[0003] 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 above-mentioned IP-borne voice and multimedia services. Currently, the 3GPP standards organization is discussing next-generation (e.g., 5G) new radio technologies. Therefore, changes to the current body of the 3GPP standards are currently being submitted and considered to evolve and complete the 3GPP standards. Summary of the Invention

[0004] The present invention discloses a method and apparatus for connecting to another User Equipment (UE). In one embodiment, the method includes a first UE connecting to a second UE via a relay UE, wherein a first PC5 unicast link is established between the first UE and the relay UE. The method further includes the first UE transmitting a link modification request message to the relay UE, wherein the link modification request message includes third user information of a third UE. The method further includes the first UE receiving a link modification acceptance message from the relay UE. Brief Description of the Drawings

[0005] Figure 1 A diagram showing a wireless communication system according to an exemplary embodiment;

[0006] Figure 2 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;

[0007] Figure 3 A functional block diagram of a communication system according to an exemplary embodiment;

[0008] Figure 4 According to an exemplary embodiment Figure 3Functional block diagram of the program code;

[0009] Figure 5 is the Figure 6 .8.2.1-1 reproduction;

[0010] Figure 6 is the Figure 6 .8.2.2-1 reproduction;

[0011] Figure 7 is the Figure 5 .2.1.4-1 reproduction;

[0012] Figure 8 is the Figure 6 .3.3.1-1 reproduction;

[0013] Figure 9 is the Figure 6 .3.3.4-1 reproduction;

[0014] Figure 10 is the Figure 5 .1-1 reproduction;

[0015] Figure 11 is the Figure 5 .2-1 reproduction;

[0016] Figure 12 is the Figure 5 .5.1-1 reproduction;

[0017] Figure 13 is the Figure 5 .5.1-2 reproduction;

[0018] Figure 14 is the Figure 5 .8.9.1.1-1 reproduction;

[0019] Figure 15 is the Figure 5 .8.9.1.1-2 reproduction;

[0020] Figure 16is a diagram according to an exemplary embodiment;

[0021] Figure 17 is a message transfer diagram according to an exemplary embodiment;

[0022] Figure 18 is a message transfer diagram according to an exemplary embodiment;

[0023] Figure 19 is a message transfer diagram according to an exemplary embodiment;

[0024] Figure 20 is a flowchart according to an exemplary embodiment. Detailed implementation manners

[0025] The exemplary wireless communication systems and devices described below employ a wireless communication system that supports broadcast services. Wireless communication systems are widely deployed to provide various types of communications, such as voice, data, etc. These systems may 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 techniques.

[0026] Specifically, the exemplary wireless communication systems and devices described below may be designed to support one or more standards, such as those provided by the consortium named "Third Generation Partnership Project" and referred to herein as 3GPP, including: TR23.752 V17.0.0, "Study on System Enhancements for Proximity-based Services (ProSe) in 5G System (5GS) (Release 17)"; TS 23.287 V16.2.0, "Architectural Enhancements for 5G System (5GS) to Support Vehicle-to-Everything (V2X) Services (Release 16)"; TR 38.836 V17.0.0, "Study on NR Sidechain Relay (Release 17)"; and TS 38.331 V16.4.1, "NR; Radio Resource Control (RRC) Protocol Specification (Release 17)". The standards and documents listed above are hereby expressly incorporated herein by reference in their entirety.

[0027] Figure 1 FIG. 4 shows a multi-access wireless communication system according to an embodiment of the present invention. The access network 100 (AN) includes a plurality of antenna groups, where one antenna group includes 104 and 106, another antenna group includes 108 and 110, and yet another antenna group includes 112 and 114. In Figure 1 FIG. 4, only two antennas are shown for each antenna group, but each antenna group may utilize more or fewer antennas. The access terminal (AT) 116 communicates with antennas 112 and 114, where antennas 112 and 114 transmit information to the access terminal 116 via the forward link 120 and receive information from the access terminal 116 via the reverse link 118. The access terminal (AT) 122 communicates with antennas 106 and 108, where antennas 106 and 108 transmit information to the access terminal (AT) 122 on the forward link 126 and receive information from the access terminal (AT) 122 on the reverse link 124. In an FDD system, the communication links 118, 120, 124, and 126 may use different frequencies for communication. For example, the forward link 120 may use a different frequency from the reverse link 118.

[0028] Each antenna group and / or the area in which the antenna group is designed to communicate is often referred to as a sector of the access network. In an embodiment, each antenna group is designed to communicate with access terminals in a sector of the area covered by the access network 100.

[0029] In communications via the forward links 120 and 126, the transmit antennas of the access network 100 may utilize beamforming to improve the signal-to-noise ratio of the forward links of different access terminals 116 and 122. Additionally, compared to an access network that transmits to all its access terminals via a single antenna, an access network that uses beamforming to transmit to access terminals randomly dispersed in its coverage area causes less interference to access terminals in adjacent cells.

[0030] An access network (AN) can be a fixed station or base station for communicating with terminals, and can also be referred to as an access point, Node B, base station, enhanced base station, evolved Node B (eNB), network node, network, or some other term. An access terminal (AT) can also be referred to as a user equipment (UE), wireless communication device, terminal, access terminal, or some other term.

[0031] Figure 2 FIG. 200 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 several data streams is provided from a data source 212 to a transmit (TX) data processor 214.

[0032] In one embodiment, each data stream is transmitted via a respective transmit antenna. The TX data processor 214 formats, encodes, and interleaves the traffic data of the data stream based on a particular encoding scheme selected for each data stream to provide encoded data.

[0033] The encoded data of each data stream can be multiplexed with pilot data using OFDM techniques. Pilot data is typically a known data pattern that is processed in a known manner and can be used at the receiver system to estimate the channel response. The multiplexed pilot and encoded data for each data stream are then modulated (i.e., symbol mapped) based on a particular modulation scheme selected for the data stream (e.g., BPSK, QPSK, M-PSK, or M-QAM) to provide modulated symbols. The data rate, encoding, and modulation for each data stream can be determined by instructions executed by a processor 230.

[0034] Next, the modulation symbols of all data streams are provided to the TX MIMO processor 220, which may further process the modulation symbols (e.g., for OFDM). The TX MIMO processor 220 then provides N T streams of modulation symbols to N T transmitters (TMTRs) 222a through 222t. In some embodiments, the TX MIMO processor 220 applies beamforming weights to the symbols of the data stream and to the antennas from which the symbols are being transmitted.

[0035] Each transmitter 222 receives and processes the corresponding symbol stream to provide one or more analog signals, and further conditions (e.g., amplifies, filters, and upconverts) the analog signals to provide a modulated signal suitable for transmission via the MIMO channel. The N T modulated signals from transmitters 222a through 222t are then transmitted from N T antennas 224a through 224t, respectively.

[0036] At the receiver system 250, the transmitted modulated signals are received by N R antennas 252a through 252r, and the signals received from each antenna 252 are provided to a corresponding receiver (RCVR) 254a through 254r. Each receiver 254 conditions (e.g., filters, amplifies, and downconverts) the corresponding received signal, digitizes the conditioned signal to provide samples, and further processes the samples to provide a corresponding "received" symbol stream.

[0037] The RX data processor 260 then receives and processes the N R received symbol streams from the N R receivers 254 based on specific receiver processing techniques to provide N T "detected" symbol streams. The RX data processor 260 then demodulates, deinterleaves, and decodes each detected symbol stream to recover the traffic data of the data stream. The processing performed by the RX data processor 260 is complementary to the processing performed by the TX MIMO processor 220 and the TX data processor 214 at the transmitter system 210.

[0038] The processor 270 periodically determines which precoding matrix to use (discussed below). The processor 270 formulates a reverse link message that includes a matrix index portion and a rank value portion.

[0039] Reverse link messages can include various types of information related to the communication link and / or the received data stream. Subsequently, the reverse link messages are processed by the TX data processor 238 for service data that also receives several data streams from the data source 236, modulated by the modulator 280, conditioned by the transmitters 254a to 254r, and transmitted back to the transmitter system 210.

[0040] At the transmitter system 210, the modulated signal from the receiver system 250 is received through the antenna 224, conditioned by the receiver 222, demodulated by the demodulator 240, and processed by the RX data processor 242 to extract the reverse link message transmitted through the receiver system 250. Subsequently, the processor 230 determines which precoding matrix to use to determine the beamforming weights and then processes the extracted message.

[0041] Steering Figure 3 , this figure shows an alternative simplified functional block diagram of a communication device according to an embodiment of the present invention. As Figure 3 shown, the UE (or AT) 116 and 122 in Figure 1 or the base station (or AN) 100 in Figure 1 can be implemented using the communication device 300 in a wireless communication system, and the wireless communication system is preferably an NR system. The communication device 300 can include an input device 302, an output device 304, a control circuit 306, a central processing unit (CPU) 308, a memory 310, 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 (e.g., a keyboard or keypad) and can output images and sounds through the output device 304 (e.g., a listener or speaker). The transceiver 314 is used to receive and transmit wireless signals, deliver the received signals to the control circuit 306, and wirelessly output the signals generated by the control circuit 306. The AN 100 in Figure 1 can also be implemented using the communication device 300 in a wireless communication system.

[0042] Figure 4 is a simplified block diagram of the program code 312 shown in Figure 3 according to an embodiment of the present invention. In this embodiment, the program code 312 includes an application layer 400, a layer 3 part 402, and a layer 2 part 404, and is coupled to a layer 1 part 406. The layer 3 part 402 generally performs radio resource control. The layer 2 part 404 generally performs link control. The layer 1 part 406 generally performs physical connection.

[0043] 3GPP TR 23.752 proposes to support inter-UE relay and related solutions for subsequent releases (e.g., Release 17 / 18) as follows:

[0044] 5.4 Key Issue #4: Support for inter-UE relay

[0045] 5.4.1 General description

[0046] This key issue aims to support inter-UE relay, including support for in-coverage and out-of-coverage operations.

[0047] At least the following aspects need to be considered in the possible solutions:

[0048] - How to (re-)select nearby inter-UE relay UEs?

[0049] - Can the network control inter-UE relay operations and how can it control inter-UE relay operations, including at least how to:

[0050] - Authorize an inter-UE relay, e.g., authorize a UE as an inter-UE relay?

[0051] - Authorize a remote UE to access the inter-UE relay?

[0052] - Provide visibility of the source / destination UEs and the inter-UE relay to the network for purposes such as charging?

[0053] - How to establish a connection between the source UE and the destination UE via the inter-UE relay?

[0054] - How to provide an end-to-end QoS framework to meet QoS requirements (e.g., data rate, reliability, latency)?

[0055] - How to enhance the system architecture to provide security protection for the relay connection?

[0056] - How to provide a mechanism for path change, e.g., in the case of an inter-UE relay change?

[0057] Note 1: Coordination with the RAN WG is required to participate in the NG-RAN.

[0058] Note 2: Coordination with SA WG3 is required for security aspects.

[0059] […]

[0060] 6.8 Solution #8: Inter-UE relay selection without relay discovery

[0061] 6.8.1 Description

[0062] When the source UE wants to communicate with the target UE, it will first try to discover the target UE by sending a direct communication request or request message with the target UE information. If the source UE cannot reach the target UE directly, then it will try to discover an inter-UE relay to reach the target UE, which may also trigger the relay to discover the target UE. To be more efficient, this solution tries to integrate target UE discovery with inter-UE relay discovery and selection, including two alternatives:

[0063] - Alternative 1: Inter-UE relay discovery and selection can be integrated into the unicast link establishment procedure as described in Section 6.3.3 of TS 23.287 [5].

[0064] - Alternative 2: Inter-UE relay discovery and selection is integrated into the Model B direct discovery procedure.

[0065] It is proposed to add a new field in the direct communication request or request message to indicate whether a relay can be used in the communication. The field can be called relay_indication. When a UE wants to broadcast a direct communication request or request message, it indicates in the message whether an inter-UE relay can be used. For Release 17, it is assumed that the indicated value is limited to single-hop.

[0066] When an inter-UE relay receives a direct communication request or request message with the relay_indication set, it shall decide whether to forward the message (i.e., modify the message and broadcast the message in its vicinity) according to, for example, the relay service code (if any), the application ID, the authorization policy (e.g., relay for a specific ProSe service), the current traffic load of the relay, the radio conditions between the source UE and the relay UE, etc.

[0067] It may be the case that multiple inter-UE relays can be used to reach the target UE, or the target UE can also directly receive the direct communication request or request message from the source UE. The target UE can choose which one to reply to according to, for example, the signal strength, the local policy (e.g., the traffic load of the inter-UE relay), the relay service code (if any), or the operator policy (e.g., always prefer direct communication or only use some specific inter-UE relays).

[0068] The source UE can receive responses from multiple inter-UE relays and can also directly receive responses from the target UE. The source UE selects the communication path according to, for example, the signal strength or the operator policy (e.g., always prefer direct communication or only use some specific inter-UE relays).

[0069] 6.8.2 Procedures

[0070] 6.8.2.1 Inter-UE relay discovery and selection integrated into the unicast link establishment procedure (Alternative 1)

[0071] [The title of 3GPP TR 23.752 V17.0.0 is "5G ProSe UE-to-UE Relay Selection (Alternative 1)"] Figure 6 .8.2.1-1 is reproduced as Figure 5

[0072] Figure 6 .8.2.1-1 describes the procedure of the proposed method.

[0073] 0. Authorize the UE to use the services provided by the UE-to-UE relay. Authorize the UE-to-UE relay to provide services for relaying traffic between UEs. Authorization and parameter provisioning can use the solution of KI#8, such as Sol#36. When the UE / relay registers to the network, authorization can be performed. Security-related parameters can be provisioned so that the UE and the relay can authenticate each other's authorization when needed.

[0074] 1. UE-1 wants to establish a unicast communication with UE-2, and the communication can be through a direct link with UE-2 or via a UE-to-UE relay. Then, UE-1 broadcasts a direct communication request with relay_indication enabled. The message will be received by Relay-1 and Relay-2. If UE-2 is near UE-1, the message can also be received by UE-2. UE-1 includes source UE information, target UE information, application ID, and relay service code (if any). If UE-1 does not want to involve a relay in the communication, it will deactivate relay_indication.

[0075] Note 1: The data type of relay_indication can be determined in Phase 3. The details of the direct communication request / accept message will be determined in Phase 3.

[0076] 2. Relay-1 and Relay-2 decide to participate in the procedure. They broadcast a new direct communication request message in their vicinity without enabling relay_indication. If a relay receives this message, it will just discard the message. When a relay broadcasts a direct communication request message, it includes the source UE information, target UE information, and relay UE information (e.g., relay UE ID) in the message, and uses the L2 address of the relay as the source layer 2 ID. The relay maintains the association between the source UE information (e.g., source UE L2 ID) and the new direct communication request.

[0077] 3. UE-2 receives the direct communication requests from Relay-1 and Relay-2. If UE-2 is within the communication range of UE-1, UE-2 can also directly receive the direct communication request message from UE-1. ​

[0078] 4. UE-2 selects Relay-1 and replies with a direct communication acceptance message. If UE-2 receives a direct communication request directly from UE-1, then it may choose to establish a direct communication link by sending the direct communication acceptance message directly to UE-1. After receiving the direct communication acceptance, the inter-UE relay retrieves the source UE information stored in step 2 and sends the direct communication acceptance message to the source UE with its relay UE information added to the message.

[0079] After step 4, UE-1 and UE-2 respectively establish PC5 links with the selected inter-UE relay.

[0080] Note 2: The security between UE1 and Relay-1 and between Relay-1 and UE-2 is performed before Relay-1 and UE-2 send the direct communication acceptance message. The details of the authentication / security establishment procedure are determined by SA WG3. If there already exists a PC5 link between the source (or target) UE and the relay available for relay services, then the security establishment procedure may be skipped.

[0081] 5. UE-1 receives the direct communication acceptance message from Relay-1. UE-1 selects a path according to, for example, policies (e.g., always choose the direct path if possible), signal strength, etc. If UE-1 receives a direct communication acceptance / response message request acceptance directly from UE-2, then it may choose to set up a direct PC5 L2 link with UE-2 as described in section 6.3.3 of TS 23.287 [5], and then skip step 6.

[0082] 6a. For the L3 inter-UE relay case, UE-1 and UE-2 complete the establishment of the communication link via the selected inter-UE relay. The link setup information may vary according to the type of relay (e.g., L2 or L3 relay). Then, UE-1 and UE-2 may communicate via the relay. Regarding the IP address assignment of the source / remote UE, the address may be assigned by the relay or by the UE itself (e.g., link-local IP address) as defined in section 6.3.3 of TS 23.287 [5].

[0083] 6b. For the layer 2 inter-UE relay case, the source UE and the target UE may set up an end-to-end PC5 link via the relay. UE-1 sends a unicast E2E direct communication request message to UE-2 via Relay-1, and UE-2 responds to UE-1 with a unicast E2E direct communication request message via Relay-1. Relay-1 forwards the message based on the identity information of UE-1 / UE-2 in the adaptation layer.

[0084] Note 3: How Relay-1 can forward the message based on the identity information of UE-1 / UE-2 in the adaptation layer needs to cooperate with RAN2 during the normative phase.

[0085] Note 4: For relaying or path selection, the source UE may set a timer after sending a direct communication request to collect corresponding response messages before making a decision. Similarly, the target UE may also set a timer after receiving the first copy of the direct communication request / message to collect multiple copies of messages from different paths before making a decision.

[0086] Note 5: When the UE receives a message from an inter-UE relay for the first time, the UE needs to verify whether the relay is authorized as an inter-UE relay. Similarly, the inter-UE relay may also need to verify whether the UE is authorized to use the relay service. The verification details and how to ensure communication between two UEs through the inter-UE relay will be defined by SA WG3.

[0087] 6.8.2.2 Integration of inter-UE relay discovery and selection into the Model B direct discovery procedure (Alternative 2)

[0088] Figure 6 The procedure for Model B of inter-UE relay discovery is depicted in 6.8.2.2-1, and the discovery / selection procedure is separated from hop-by-hop and end-to-end link establishment.

[0089] [The title of 3GPP TR 23.752 V17.0.0 is "5G ProSe Inter-UE Relay Selection (Alternative 2) (5G ProSe UE-to-UE relay selection (Alternative 2))"] Figure 6 6.8.2.2-1 is reproduced as Figure 6

[0090] 1. UE-1 broadcasts a discovery request message carrying UE-1 information, target UE information (UE-2), application ID, relay service code (if any), and UE-1 may also indicate that relay_indication is enabled.

[0091] 2. Upon receiving the discovery request, the candidate relay UE-R broadcasts a discovery request carrying UE-1 information, UE-R information, and target UE information. The relay UE-R uses the L2 address of the relay as the source layer 2 ID.

[0092] 3. The target UE-2 responds to the discovery message. If UE-2 receives the discovery request message in step 1, then in step 3b, UE-2 responds to the discovery response with UE-1 information and UE-2 information. If UE-2 does not receive the discovery request in step 2, then in step 3a, UE-2 responds to the discovery response message with UE-1 information, UE-R information, and UE-2 information.

[0093] ​4. When receiving a discovery response in step 3a, UE-R sends a discovery response with UE-1 information, UE-R information, and UE-2 information. If more than one candidate relay UE responds to the discovery response message, then UE-1 can select a relay UE based on, for example, an implementation plan or link eligibility.

[0094] 5. The source UE and the target UE may need to establish a PC5 link with the relay before communicating with each other. If a PC5 link already exists between UE-1 that can be used for relaying and UE-R, then step 5a can be skipped. If a PC5 link already exists between UE-2 that can be used for relaying and UE-R, then step 5b can be skipped.

[0095] 6a. The same as step 6a described in Section 6.8.2.1.

[0096] 6b. For layer 2 inter-UE relaying, send the E2E unicast direct communication request message from UE1 to the selected relay via each hop link (established in step 5a) and the adaptation layer information that identifies the peer UE (UE3) as the destination. The inter-UE relay forwards the E2E message based on the identity information of the peer UE in the adaptation layer. The initiator (UE1) knows the adaptation layer information that identifies the peer UE (UE3) after the discovery procedure. UE3 responds in the same way with an E2E unicast direct communication acceptance message.

[0097] Note 1: For the layer 2 inter-UE relaying case, whether step 5b is executed before step 6b or triggered during step 6b will be determined in the normative phase.

[0098] Note 2: How Relay-1 can forward messages based on the identity information of UE-1 / UE-2 in the adaptation layer needs to cooperate with RAN2 during the normative phase.

[0099] 6.8.3 Impact on Services, Entities, and Interfaces

[0100] Impact on UEs supporting new relay-related functions.

[0101] 3GPP TS 23.287 stipulates the unicast mode V2X communication via the PC5 reference point, layer 2 link establishment via the PC5 reference point, link identifier update, and layer 2 link modification as follows:

[0102] 5.2.1.4 Unicast Mode Communication via the PC5 Reference Point

[0103] The NR-based PC5 reference point only supports the unicast communication mode. Figure 5 .2.1.4-1 shows an example of a PC5 unicast link.

[0104] The title of 3GPP TS 23.287 V16.2.0 is "Example of PC5 Unicast Links" Figure 5 .2.1.4-1 is reproduced as Figure 7

[0105] When V2X communication is performed via a PC5 unicast link, the following principles apply:

[0106] - The PC5 unicast link between two UEs allows V2X communication between one or more pairs of peer V2X services among these UEs. All V2X services using the same PC5 unicast link in a UE use the same application layer ID.

[0107] Note 1: Due to privacy, the application layer ID may change over time as described in Sections 5.6.1.1 and 6.3.3.2. This does not cause the reconstruction of the PC5 unicast link. The UE triggers a link identifier update procedure as specified in Section 6.3.3.2.

[0108] - A PC5 unicast link supports one or more V2X service types (e.g., PSID or ITS-AID) if these V2X service types are associated with at least the peer application layer ID pair of this PC5 unicast link. For example, as Figure 5 shown in.2.1.4-1, UE A and UE B have two PC5 unicast links, one between peer application layer ID 1 / UE A and application layer ID 2 / UE B and one between peer application layer ID 3 / UE A and application layer ID 4 / UE B.

[0109] Note 2: It is not required that the source UE knows whether different target application layer IDs on different PC5 unicast links belong to the same target UE.

[0110] - The PC5 unicast link uses a single network layer protocol, such as IP or non-IP, to support V2X communication.

[0111] - As specified in Section 5.4.1, the PC5 unicast link supports a per-flow QoS model.

[0112] When the application layer in a UE initiates data transfer for a V2X service that requires a unicast communication mode via the PC5 reference point:

[0113] - If a pair of peer application layer IDs and the network layer protocol of this PC5 unicast link are the same as those required by the application layer in the UE for this V2X service, then the UE will reuse the existing PC5 unicast link and modify the existing PC5 unicast link as specified in Section 6.3.3.4 to add this V2X service; otherwise ​

[0114] - The UE shall trigger the establishment of a new PC5 unicast link as specified in Section 6.3.3.1.

[0115] After successfully establishing the PC5 unicast link, UE A and UE B shall use the same pair of layer 2 IDs for subsequent PC5-S signaling message exchanges and V2X service data transmissions, as specified in Section 5.6.1.4. The V2X layer of the transmitting UE indicates to the AS layer whether the transmission is for PC5-S signaling messages (i.e., direct communication request / accept, link identifier update request / response, disconnection request / response, link modification request / accept) or V2X service data.

[0116] For each PC5 unicast link, the UE shall self-assign different PC5 link identifiers that uniquely identify the PC5 unicast link in the UE during the lifetime of the PC5 unicast link. Each PC5 unicast link is associated with a unicast link profile that contains:

[0117] - The V2X service type (e.g., PSID or ITS-AID); and

[0118] - The application layer ID and layer 2 ID of UE A; and

[0119] - The application layer ID and layer 2 ID of UE B; and

[0120] - The network layer protocol used on the PC5 unicast link; and

[0121] - For each V2X service type, a set of PC5 QoS flow identifiers (PC5 QoS Flow Identifier, PFI). Each PFI is associated with QoS parameters (i.e., PQI).

[0122] For privacy reasons, the application layer ID and layer 2 ID may change during the lifetime of the PC5 unicast link as described in Sections 5.6.1.1 and 6.3.3.2, and if so, the unicast link profile shall be updated accordingly. The UE uses the PC5 link identifier to indicate the PC5 unicast link to the V2X application layer, so the V2X application layer can identify the corresponding PC5 unicast link even if there are more than one unicast links associated with a V2X service type (e.g., for the same V2X service type, the UE establishes multiple unicast links with multiple UEs).

[0123] After a layer 2 link modification of the established PC5 unicast link as specified in Section 6.3.3.4 or a layer 2 link identifier update as specified in Section 6.3.3.2, the unicast link profile shall be updated accordingly.

[0124] V2X service information and QoS information are carried in PC5-S signaling messages and exchanged between two UEs as specified in Section 6.3.3. Based on the replacement information, the PFI is used to identify the V2X service. When the receiving UE receives V2X service data through the established PC5 unicast link, the receiving UE determines the appropriate V2X service based on the PFI to forward the received V2X service data to the upper layer.

[0125] After receiving the indication to release the PC5-RRC connection due to RLF from the AS layer, the V2X layer in the UE locally releases the PC5 unicast link associated with this PC5-RRC connection. The AS layer uses the PC5 link identifier to indicate the PC5 unicast link for releasing the PC5-RRC connection.

[0126] When the PC5 unicast link has been released as specified in Section 6.3.3.3, the V2X layer of each UE for the PC5 unicast link notifies the AS layer that the PC5 unicast link has been released. The V2X layer uses the PC5 link identifier to indicate the released unicast link.

[0127] […]

[0128] 5.6.1.4 Identifiers for Unicast Mode V2X Communication via the PC5 Reference Point

[0129] For unicast mode V2X communication via the PC5 reference point, the destination layer 2 ID used depends on the communication peer. The layer 2 ID of the communication peer identified by the application layer ID can be discovered during the establishment of the PC5 unicast link, or be known to the UE via a previous V2X communication (e.g., an existing or previous unicast link to the same application layer ID), or obtained from an application layer service notification. The initial signaling for establishing the PC5 unicast link can use a preset destination layer 2 ID associated with the V2X service type (e.g., PSID / ITS-AID) configured for the establishment of the PC5 unicast link, as specified in Section 5.1.2.1. During the PC5 unicast link establishment procedure, the layer 2 ID is exchanged and shall be used for future communication between the two UEs, as specified in Section 6.3.3.1.

[0130] The application layer ID is associated with one or more V2X applications within the UE. If the UE has more than one application layer ID, from the perspective of the peer UE, each application layer ID of the same UE can be regarded as the application layer ID of a different UE.

[0131] Since the V2X application layer does not use the layer 2 ID, the UE maintains a mapping between the application layer ID and the source layer 2 ID used for the PC5 unicast link. This allows the source layer 2 ID to be changed without interrupting the V2X application.

[0132] When the application layer ID changes, if the link is used for V2X communication with the changed application layer ID, the source layer 2 ID of the PC5 unicast link shall change.

[0133] Based on the privacy configuration as specified in Section 5.1.2.1, updating the new identifier of the source UE to the peer UE for the established unicast link may cause the peer UE to change its layer 2 ID and optionally its IP address / prefix (if IP communication is used as defined in Section 6.3.3.2).

[0134] A UE may establish multiple PC5 unicast links with a peer UE and use the same or different source layer 2 IDs for these PC5 unicast links.

[0135] […]

[0136] 6.3.3.1 Establishing a layer 2 link via the PC5 reference point

[0137] To perform unicast mode V2X communication via the PC5 reference point, the UE is configured with the relevant information as described in Section 5.1.2.1.

[0138] Figure 6 .3.3.1-1 shows the layer 2 link establishment procedure for unicast mode V2X communication via the PC5 reference point.

[0139] [The title of 3GPP TS 23.287 V16.2.0 is “Layer-2 link establishment

[0140] procedure)” Figure 6 .3.3.1-1 is reproduced as Figure 8

[0141] 1. The UE determines the destination layer 2 ID for signaling reception for PC5 unicast link establishment, as specified in Section 5.6.1.4. The destination layer 2 ID is configured with the UE, as specified in Section 5.1.2.1.

[0142] 2. The V2X application layer in UE-1 provides application information for PC5 unicast communication. The application information includes the V2X service type of the V2X application (e.g., PSID or ITS-AID) and the application layer ID of the initiating UE. The application information may include the application layer ID of the target UE.

[0143] The V2X application layer in UE-1 may provide V2X application requirements for this unicast communication. As specified in Section 5.4.1.4, UE-1 determines the PC5 QoS parameters and PFI.

[0144] ​If UE-1 decides to reuse an existing PC5 unicast link as specified in Section 5.2.1.4, UE triggers a layer 2 link modification procedure as specified in Section 6.3.3.4.

[0145] 3. UE-1 sends a direct communication request message to initiate a unicast layer 2 link establishment procedure. The direct communication request message contains:

[0146] - Source user information: the application layer ID of the initiating UE (i.e., the application layer ID of UE-1).

[0147] - If the V2X application layer provides the application layer ID of the target UE in step 2, the following information is included:

[0148] - Target user information: the application layer ID of the target UE (i.e., the application layer ID of UE-2).

[0149] - V2X service information: information about the V2X service for which the layer 2 link establishment is requested (e.g., PSID or ITS-AID).

[0150] - Security information: information for establishing security.

[0151] Note 1: The security information and the necessary protection for the source user information and the target user information are defined by SA WG3.

[0152] As specified in Sections 5.6.1.1 and 5.6.1.4, the source layer 2 ID and the destination layer 2 ID for sending the direct communication request message are determined. The destination layer 2 ID can be a broadcast or unicast layer 2 ID. When using a unicast layer 2 ID, the target user information shall be included in the direct communication request message.

[0153] UE-1 sends the direct communication request message via PC5 broadcast or unicast using the source layer 2 ID and the destination layer 2 ID.

[0154] 4. The security of UE-1 is established as follows:

[0155] 4a. If the target user information is included in the direct communication request message, the target UE, i.e., UE-2 responds by establishing security with UE-1.

[0156] 4b. If the target user information is not included in the direct communication request message, the UEs interested in using the notified V2X service via the PC5 unicast link with UE-1 respond by establishing security with UE-1.

[0157] Note 2: The signaling for the security procedure is defined by SA WG3.

[0158] When security protection is enabled, UE-1 sends the following information to the target UE:

[0159] - If using IP communication:

[0160] - IP address configuration: For IP communication, this link requires IP address configuration, and the IP address configuration indicates one of the following values:

[0161] - "IPv6 router", if only the IPv6 address allocation mechanism is supported by the initiating UE, i.e., acting as an IPv6 router; or

[0162] - "IPv6 address allocation not supported", if the IPv6 address allocation mechanism is not supported by the initiating UE.

[0163] - Link-local IPv6 address: A link-local IPv6 address formed locally based on RFC 4862

[21] , if UE-1 does not support the IPv6 IP address allocation mechanism, i.e., the IP address configuration indicates "IPv6 address allocation not supported".

[0164] - QoS information: Information about the PC5 QoS flow. For each PC5 QoS flow, the PFI and the corresponding PC5 QoS parameters (i.e., PQI and conditionally other parameters such as MFBR / GFBR, etc.).

[0165] As specified in Sections 5.6.1.1 and 5.6.1.4, determine the source layer 2 ID for the security establishment process. The destination layer 2 ID is set to the source layer 2 ID of the received direct communication request message.

[0166] After receiving the security establishment process message, for the signaling and data traffic of this unicast link, UE-1 obtains the layer 2 ID of the peer UE for future communication.

[0167] 5. The target UE that has successfully established security with UE-1 sends a direct communication acceptance message to UE-1:

[0168] 5a. (UE-oriented layer 2 link establishment) If the direct communication request message contains the target user information, and if the application layer ID for UE-2 matches, the target UE, i.e., UE-2 responds with a direct communication acceptance message.

[0169] 5b. (V2X service-oriented layer 2 link establishment) If the direct communication request message does not contain the target user information, the UE interested in using the notified V2X service responds to the request by sending a direct communication acceptance message (UE-2 and UE-4 in Figure 6 .3.3.1-1).

[0170] The direct communication received message contains:

[0171] - Source user information: The application layer ID of the UE that sends the direct communication received message.

[0172] - QoS information: Information about the PC5 QoS flow. For each PC5 QoS flow, the PFI requested by UE-1 and the corresponding PC5 QoS parameters (i.e., PQI and conditionally other parameters, such as MFBR / GFBR, etc.).

[0173] - If IP communication is used:

[0174] - IP address configuration: For IP communication, this link requires IP address configuration, and the IP address configuration indicates one of the following values:

[0175] - "IPv6 router", if the IPv6 address allocation mechanism is supported by the target UE, i.e., acting as an IPv6 router; or

[0176] - "Does not support IPv6 address allocation", if the IPv6 address allocation mechanism is not supported by the target UE.

[0177] - Link-local IPv6 address: The link-local IPv6 address formed locally based on RFC 4862

[21] , if the target UE does not support the IPv6 IP address allocation mechanism, i.e., the IP address configuration indicates "does not support IPv6 address allocation", and UE-1 includes the link-local IPv6 address in the direct communication request message. The target UE shall include a non-conflicting link-local IPv6 address.

[0178] If two UEs (i.e., the initiating UE and the target UE) are selected to use the link-local IPv6 address, they will deactivate the duplicate address detection defined in RFC 4862

[21] .

[0179] Note 3: When the initiating UE or the target UE indicates support for the IPv6 router, the corresponding address configuration process will be implemented after the layer 2 link is established, and the link-local IPv6 address will be ignored.

[0180] The V2X layer of the UE that establishes the PC5 unicast link will allocate the PC5 link identifier for the unicast link and pass the PC5 unicast link-related information down to the AS layer. The information related to the PC5 unicast link includes layer 2 ID information (i.e., the source layer 2 ID and the destination layer 2 ID). This enables the AS layer to maintain the PC5 link identifier and the PC5 unicast link-related information.

[0181] 6. Transmit V2X service data through the established unicast link as follows:

[0182] Provide the PC5 link identifier, PFI, and V2X service data to the AS layer.

[0183] Optionally, additionally provide layer 2 ID information (i.e., source layer 2 ID and destination layer 2 ID) to the AS layer.

[0184] Note 4: The UE implementation provides the layer 2 ID information to the AS layer.

[0185] UE-1 sends V2X service data using the source layer 2 ID (i.e., the layer 2 ID of UE-1 for this unicast link) and the destination layer 2 ID (i.e., the layer 2 ID of the peer UE for this unicast link).

[0186] Note 5: The PC5 unicast link is bidirectional, so the peer UE of UE-1 can send V2X service data to UE-1 through the unicast link with UE-1.

[0187] […]

[0188] 6.3.3.4 Layer 2 Link Modification for Unicast Links

[0189] Figure 6 .3.3.4-1 shows the layer 2 link modification procedure for unicast links. This procedure is used for:

[0190] - Add a new V2X service to an existing PC5 unicast link.

[0191] - Remove a V2X service from an existing PC5 unicast link.

[0192] - Add a new PC5 QoS flow to an existing PC5 unicast link.

[0193] - Modify an existing PC5 QoS flow in an existing PC5 unicast link.

[0194] - Remove an existing PC5 QoS flow from an existing PC5 unicast link.

[0195] [The content titled "Layer-2 link modification procedure" in 3GPP TS 23.287 V16.2.0 Figure 6 .3.3.4-1 is reproduced as Figure 9

[0196] 0. UE-1 and UE-2 have a unicast link established as described in Section 6.3.3.1.

[0197] ​1. The V2X application layer in UE-1 provides application information for PC5 unicast communication. The application information includes the V2X service type of the V2X application (e.g., PSID or ITS-AID) and the application layer ID of the initiating UE. The application information may include the application layer ID of the target UE. If UE-1 decides to reuse an existing PC5 unicast link as specified in Section 5.2.1.4 and thus decides to modify the unicast link established with UE-2, then UE-1 sends a link modification request to UE-2.

[0198] The link modification request message includes:

[0199] a) To add a new V2X service to an existing PC5 unicast link:

[0200] - V2X service information: Information about the V2X service to be added (e.g., PSID or ITS-AID).

[0201] - QoS information: Information about the PC5 QoS flow for each V2X service to be added. For each PC5 QoS flow, PFI and the corresponding PC5 QoS parameters (i.e., PQI and conditionally other parameters such as MFBR / GFBR, etc.).

[0202] b) To remove a V2X service from an existing PC5 unicast link:

[0203] - V2X service information: Information about the V2X service to be removed (e.g., PSID or ITS-AID).

[0204] c) To add a new PC5 QoS flow to an existing PC5 unicast link:

[0205] - V2X service information: Information about the V2X service for which a new QoS flow needs to be added (e.g., PSID or ITS-AID).

[0206] - QoS information: Information about the PC5 QoS flow to be modified. For each PC5 QoS flow, PFI and the corresponding PC5 QoS parameters (i.e., PQI and conditionally other parameters such as MFBR / GFBR, etc.).

[0207] d) To modify a PC5 QoS flow in an existing PC5 unicast link:

[0208] - QoS information: Information about the PC5 QoS flow to be modified. For each PC5 QoS flow, PFI and the corresponding PC5 QoS parameters (i.e., PQI and conditionally other parameters such as MFBR / GFBR, etc.).

[0209] e) To remove the PC5 QoS flow in the existing PC5 unicast link:

[0210] - PFI.

[0211] 2. UE-2 responds with a link modification acceptance message.

[0212] The link modification acceptance message contains:

[0213] - For the cases a), c) and d) described in step 1:

[0214] - QoS information: Information about the PC5 QoS flow. For each PC5 QoS flow, the PFI and the corresponding PC5 QoS parameters (i.e., PQI and optionally other parameters such as MFBR / GFBR, etc.).

[0215] The V2X layer of each UE provides information about the unicast link modification to the AS layer. This enables the AS layer to update the context related to the modified unicast link.

[0216] 3GPP TS 38.836 specifies the sidelink-based UE-to-UE relay as follows:

[0217] 5 Sidelink-based UE-to-UE relay

[0218] 5.1 Scenarios, assumptions and requirements

[0219] UE-to-UE relay enables the extension of the coverage range and power saving for sidelink transmissions between two sidelink UEs. The coverage scenarios considered in this study are as follows:

[0220] 1) All UEs (source UE, relay UE, destination UE) are within the coverage area.

[0221] 2) All UEs (source UE, relay UE, destination UE) are outside the coverage area.

[0222] 3) Partial coverage, where at least one of the UEs (source UE, relay UE, destination UE) involved in the relay is within the coverage area and at least one of the UEs involved in the relay is outside the coverage area.

[0223] RAN2 aims to find a common solution for both in-coverage and out-of-coverage situations. For UE-to-UE relay, the scenario where UEs can be within the coverage areas of different cells is supported.

[0224] Figure 5 .1-1 shows the scenarios considered for UE-to-UE relay. In Figure 5 .1-1, the coverage area means that the source / destination UE and / or the UE-to-UE relay UE is within the coverage area and can access the network over Uu.

[0225] [From 3GPP TS 38.836 V17.0.0, titled "Scenarios for UE-to-UE Relay (where the coverage status is not shown)"]

[0226] (Scenarios for UE-to-UE Relay(where the coverage status is not shown)) Figure 5 .1-1 is reproduced as Figure 10

[0228] Regarding the PC5 sidelink assumptions for the NR between the remote UE and the UE-to-UE relay.

[0229] Without considering the cross-RAT configuration / control of the source UE, UE-to-UE relay, and destination UE, i.e., the eNB / ng-eNB does not control / configure the NR source UE, target UE, or UE-to-UE relay UE. For UE-to-UE relay, this study focuses on the unicast data traffic between the source UE and the destination UE.

[0230] Configuring / scheduling the UE (source UE, destination UE, or UE-to-UE relay UE) by the SN to perform NR sidelink communication is out of the scope of this study.

[0231] For UE-to-UE relay, it is assumed that the remote UE has an end-to-end connection through the role of only a single relay UE at a given time.

[0232] Once the PC5 link is established between the source UE, UE-to-UE relay, and destination UE, data relay between the source UE and the destination UE can occur.

[0233] No restrictions are assumed on the RRC state of any UE involved in UE-to-UE relay.

[0234] During the mobility in this release, the requirement for service continuity is only for UE-to-network relay, not for UE-to-UE relay.

[0235] 5.2 Discovery

[0236] Supports Model A and Model B discovery models as defined in Section 5.3.1.2 of TS 23.303 [3] for UE-to-UE relay, and can support the integrated PC5 unicast link establishment procedure based on SA2 conclusions. Figure 5 .2-1 describes the protocol stack of the discovery message. [From 3GPP TS 38.836 V17.0.0, titled "Protocol Stack of Discovery Message for UE-to-UE Relay"] Figure 5.2-1 is reproduced as Figure 11

[0237] When triggered by the upper layer, the relay UE or the remote UE is allowed to transmit discovery messages.

[0238] Both the remote UE and the relay UE can rely on pre-configuration, unless the relevant radio configuration is provided by the network via system information or dedicated signaling.

[0239] The resource pool for transmitting discovery messages can be shared or separated from the resource pool for data transmission.

[0240] - For both the shared resource pool and the separated resource pool, a new LCID is introduced for discovery messages, i.e., the discovery messages are carried by a new SL SRB.

[0241] - Within the separated resource pool, discovery messages are equally processed with each other during the LCP procedure.

[0242] 5.3 Relay Selection (Re-selection) Criteria and Procedures

[0243] The baseline solution for relay selection (re-selection) is as follows:

[0244] Radio measurements at the PC5 interface are considered part of the relay selection (re-selection) criteria.

[0245] - The remote UE uses at least the radio signal strength measurement of the sidelink discovery message to evaluate whether the PC5 link quality of the relay UE meets the relay selection and re-selection criteria.

[0246] - When the remote UE is connected to the relay UE, it can use SL-RSRP measurements on the sidelink unicast link to evaluate whether the PC5 link quality of the relay UE meets the relay re-selection criteria.

[0247] Additional details regarding PC5 radio measurement criteria, for example, in the case of no transmission on the sidelink unicast link, can be discussed in the WI phase. If the remote UE has a PC5-RRC connection with the relay UE, how to perform RSRP measurements based on the RSRP of the discovery message and / or SL-RSRP can be determined in the WI phase.

[0248] For relay selection (re-selection), the remote UE compares the PC5 radio measurements of the relay UE with the thresholds configured by the gNB or pre-configured. The remote UE also needs to consider the higher layer criteria for relay selection (re-selection), but the details can be left for SA2 to decide. Relay selection (re-selection) can be triggered by the upper layer of the remote UE.

[0249] ​If the NR side - link signal strength of the current side - link relay is lower than a (pre - configured) threshold, then relay reselection shall be triggered. Also, if the remote UE detects an RLF of the PC5 link with the current relay UE, then relay reselection can be triggered.

[0250] The above baseline for relay selection (reselection) applies to L2 and L3 relay solutions. Additional AS layer criteria can be considered in the WI phase for L2 and L3 UE - to - UE relay solutions.

[0251] For relay selection (reselection), when the remote UE has multiple suitable relay UE candidates that meet all AS layer and higher layer criteria and the remote UE needs to select a relay UE by itself, it is determined by the UE implementation which relay UE to select.

[0252] As obtained in TR 23.752, Solution #8 and Solution #50 in TR 23.752 are considered as baseline solutions for L2 and L3 UE - to - UE relay reselection, and Solution #8 and Solution #11 in TR 23.752 are considered as baseline solutions for L3 UE - to - UE relay selection.

[0253] 5.4 Relay / Remote UE Authorization

[0254] RAN2 concludes that the authorization of both the relay UE and the remote UE has no RAN2 impact.

[0255] 5.5 Layer 2 Relay

[0256] 5.5.1 Architecture and Protocol Stack

[0257] For the L2 UE - to - UE relay architecture, except for the fact that the termination points are two remote UEs, the protocol stack is similar to that of L2 UE - to - network relay. The protocol stacks for the user plane and control plane of the L2 UE - to - UE relay architecture are described in Figure 5 .5.1 - 1 and Figure 5 .5.1 - 2.

[0258] An adaptation layer is supported on the second PC5 link (i.e., the PC5 link between the relay UE and the destination UE) for L2 UE - to - UE relay. For L2 UE - to - UE relay, the adaptation layer is placed on the RLC sub - layer for CP and UP on the second PC5 link. The side - link SDAP / PDCP and RRC terminate between the two remote UEs, while the RLC, MAC, and PHY terminate in each PC5 link.

[0259] [3GPP TS 38.836 V17.0.0, titled "Userplane Protocol Stack for L2 UE - to - UE Relay"

[0260] "protocol stack for L2 UE-to-UE Relay)" Figure 5 .5.1-1 is reproduced as Figure 12

[0261] [In 3GPP TS 38.836 V17.0.0, the section titled "Control plane protocol stack for L2 UE-to-UE Relay"

[0262] "protocol stack for L2 UE-to-UE Relay)" Figure 5 .5.1-2 is reproduced as Figure 13

[0263] For the first hop of L2 UE-to-UE relay:

[0264] - The first-hop PC5 adaptation layer between the remote UE SL radio bearer and the first-hop PC5 RLC channel supports N:1 mapping for relay.

[0265] - The adaptation layer on the first PC5 hop between the source remote UE and the relay UE supports identification of traffic destined for different destination remote UEs.

[0266] For the second hop of L2 UE-to-UE relay:

[0267] - The second-hop PC5 adaptation layer can be used to support the bearer mapping between the incoming RLC channel on the first PC5 hop and the outgoing RLC channel on the second PC5 hop at the relay UE.

[0268] - The PC5 adaptation layer supports N:1 bearer mapping between multiple incoming PC5 RLC channels on the first PC5 hop and one outgoing PC5 RLC channel on the second PC5 hop, and supports the remote UE identification function.

[0269] For L2 UE-to-UE relay:

[0270] - The identity information of the remote UE end-to-end radio bearer is included in the adaptation layer in the first and second PC5 hops.

[0271] - Additionally, the identity information of the source remote UE and / or the destination remote UE is candidate information to be included in the adaptation layer, which will be determined in the WI phase.

[0272] 5.5.2 QoS

[0273] The QoS handling for L2 UE-to-UE relay is affected by the upper layer, such as Solution #31 in TR 23.752 studied by SA2.

[0274] ​​5.5.3 Security

[0275] As described in section 6.9.1.2 (solution #9) of TR 23.752, in the case of L2 UE - to - UE relay, security is established at the PDCP layer in an end - to - end manner between UE1 and UE2. Confirmation from SA3 is required in terms of security.

[0276] 5.5.4 Control Plane Procedures

[0277] RAN2 takes the SA2 solution in TR 23.752 [6] as the baseline. Other RAN2 impacts (if any) can be discussed in the WI phase.

[0278] 3GPP TS 38.331 specifies the sidelink RRC reconfiguration for NR sidelink communication as follows:

[0279] 5.8.9.1 Sidelink RRC Reconfiguration

[0280] 5.8.9.1.1 Overview

[0281] [What is titled "Sidelink RRC reconfiguration, successful" in 3GPP TS 38.331 V16.1.0 Figure 5 .8.9.1.1 - 1 is reproduced as Figure 14

[0282] [What is titled "Sidelink RRC reconfiguration, failure" in 3GPP TS 38.331 V16.1.0 Figure 5 .8.9.1.1 - 2 is reproduced as Figure 15

[0283] The purpose of this procedure is to modify the PC5 - RRC connection, such as establishing / modifying / releasing sidelink DRBs, configuring NR sidelink measurements and reports, configuring sidelink CSI reference signal resources and CSI reporting latency bounds.

[0284] In the following cases, the UE can initiate the sidelink RRC reconfiguration procedure and perform the operations in subsection 5.8.9.1.2 on the corresponding PC5 - RRC connection:

[0285] - Release the sidelink DRB associated with the peer UE, as specified in subsection 5.8.9.1a.1;

[0286] - Establish the sidelink DRB associated with the peer UE, as specified in subsection 5.8.9.1a.2; ​​

[0287] - Modify the parameters in the SLRB-Config that are included in the sidelink DRB associated with the peer UE, as specified in Subsection 5.8.9.1.5a.2;

[0288] - Configuration of the peer UE for performing NR sidelink measurements and reporting.

[0289] - Configuration of sidelink CSI reference signal resources and CSI reporting latency bounds.

[0290] In RRC_CONNECTED, the UE applies the NR sidelink communication parameters provided in RRCReconfiguration (if any). In RRC_IDLE or RRC_INACTIVE, the UE applies the NR sidelink communication parameters provided in the system information (if any). For other cases, the UE applies the NR sidelink communication parameters provided in SidelinkPreconfigNR (if any). 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.

[0291] Key Issue #4 in 3GPP TR 23.752 describes the support for UE-to-UE relay in the next release (i.e., Release 17 / 18), which means that in cases where two UEs cannot communicate directly with each other, relay can be used to support communication between these two UEs. It is speculated that UE-to-UE relay requires establishing a PC5 unicast link with each of the source UE (i.e., the first PC5 hop) and the target UE (i.e., the second PC5 hop), such that the integrated PC5 unicast link between the source UE and the target UE can support relevant ProSe services, as Figure 16 shown.

[0292] In 3GPP TS 38.836 Figure 5 .5.1-1 (reproduced as Figure 12 ) and Figure 5 .5.1-2 (reproduced as Figure 13)Describe the protocol stacks of the user plane and control plane of the L2 UE - to - UE relay architecture, which includes an adaptation layer to support multiple source UEs communicating with one target UE via UE - to - UE relay and to support one source UE communicating with multiple target UEs via UE - to - UE relay. 3GPP TS38.836 further specifies that the header of the adaptation layer protocol data unit (PDU) of the first and second PC5 hops contains the identity information of the end - to - end radio bearer (remote UE). Additionally, the identity information of the source remote UE and / or the destination remote UE are candidate information to be included in the header of the adaptation layer PDU, which will be determined in the upcoming WI phase.

[0293] Presumably, when transmitting the adaptation layer PDU, the source UE may need to include information (e.g., the local identity / identifier (ID) of the target UE) in the header of the PDU to identify the target UE, so that the UE - to - UE relay can forward the service data unit (SDU) contained in the PDU to the target UE on the right - hand - side link radio link control (RLC) bearer (or logical channel) in the second PC5 hop, because separate side - link RLC bearers can be established between the UE - to - UE relay and different target UEs for communication. In addition to the identity information of the target UE, the ID of the end - to - end radio bearer included by the source UE in the header can also be used by the UE - to - UE relay to determine the side - link RLC bearer. The header may not need to include information to identify the source UE. On the other hand, the UE - to - UE relay may need to include information (e.g., the local ID of the source UE) to identify the source UE in the header of the adaptation layer PDU sent to the target UE, so that the target UE can deliver the PDU contained in the PDU to the right - hand - side link PDCP entity, because separate side - link PDCP entities are established in the target UE for different source UEs. The end - to - end radio bearer ID can also be included in the header of the adaptation layer PDU by the UE - to - UE relay. The header may not need to include information to identify the target UE. Figure 17 Illustrate an example of the above concept.

[0294] To meet the above concepts, a remote UE needs to know the local ID of another remote UE for the adaptation layer when communicating with the other remote UE via an inter-UE relay, and the inter-UE relay needs to know the local IDs of these two remote UEs. The remote UE does not seem to need to know its own local ID. Additionally, each local ID of other remote UEs associated with a relevant remote UE can be unique within the scope of the relevant remote UE. It is also possible that each local ID of a remote UE can be unique within the scope of the inter-UE relay. Since the inter-UE relay needs to know the local IDs of two paired remote UEs, a possible solution is for the inter-UE relay to assign or allocate a local ID to each remote UE and then provide the local ID of one remote UE to the other remote UE. Alternatively, one remote UE can assign or allocate a local ID to the other remote UE and then provide it to the inter-UE relay. In this case, the inter-UE relay needs to maintain the associated local ID of each remote UE.

[0295] Basically, each remote UE can maintain the UE context of another remote UE that communicates with it via an inter-UE relay to support the relay operation. The UE context can include an upper layer ID (e.g., the application layer ID of the UE), a local ID, and an application / service ID. In other words, the association between the upper layer ID and the local ID is maintained in each remote UE to support the relay operation. The inter-UE relay can also maintain the UE context of each remote UE. In addition to the upper layer ID (e.g., the application layer ID of the UE), the local ID, and the application / service ID, the UE context in the inter-UE relay can also include the layer 2 ID of the relevant remote UE. The upper layer ID of the UE can be the application layer ID of the UE, which is not the layer 2 ID.

[0296] For a possible solution, inter-UE relay may assign or allocate a local ID to each remote UE and then provide the local ID of one remote UE to the other remote UE during the integrated unicast link establishment procedure with the two paired remote UEs. In one embodiment, the inter-UE relay may transmit the local ID to the remote UE in a direct communication request message or a direct communication acceptance message. More specifically, after receiving a direct communication request message from a source remote UE, the inter-UE relay includes the local ID of the source remote UE in another direct communication request message and transmits it to the target remote UE. Both direct communication request messages may also include the upper layer ID of the source remote UE (e.g., the application layer ID of the UE) and the upper layer ID of the target remote UE (e.g., the application layer ID of the UE). And after receiving a direct communication acceptance message from the target remote UE, the inter-UE relay includes the local ID of the target remote UE in another direct communication acceptance message and transmits it to the source remote UE. Both direct communication acceptance messages may also include the upper layer ID of the target remote UE (e.g., the application layer ID of the UE). Considering that there may be multiple source remote UEs, the direct communication acceptance message or both direct communication acceptance messages from the target remote UE may also include the upper layer ID of the source remote UE. After the two remote UEs obtain the local ID of the other remote UE, data exchange on the user plane and message exchange on the control plane via the inter-UE relay can be initiated. Figure 18 Describe the above solution.

[0297] After a unicast link between the inter-UE relay and the remote UE has been established, it is also possible for the inter-UE relay to provide the local ID of another remote UE to the remote UE. The local ID may be transmitted in a PC5-S message (e.g., a link identifier update request message, a link modification request message), a sidelink RRC message (e.g., an RRC reconfiguration sidelink message), or a sidelink MAC control element (to be specified). In addition to the local ID, the PC5-S message, the sidelink RRC message, or the sidelink MAC control element may also include the upper layer ID of another remote UE (e.g., the application layer ID of the UE) for associating the local ID with the upper layer ID of another remote UE.

[0298] After a remote UE (UE1) is connected to another remote UE (UE2) via an inter-UE relay, data (or traffic) from one remote UE can be forwarded by the inter-UE relay to the other remote UE. It is possible that the remote UE may want to further connect to another remote UE (UE3) via the same inter-UE relay UE. It is not clear how this can be achieved.

[0299] Since a PC5 unicast link has been established between the remote UE and the relay between UEs to support data communication between these two remote UEs, a possible solution to the above problem is that the remote UE initiates a layer 2 link modification procedure to the relay between UEs, so that the relay between UEs can further establish another PC5 unicast link with another remote UE. The relay between UEs can directly initiate a PC5 unicast link establishment procedure to another remote UE, or can first initiate a discovery procedure to discover another remote UE before initiating the PC5 unicast link establishment procedure. A security establishment procedure can be performed between the relay between UEs and another remote UE during the PC5 unicast link establishment procedure. After the above procedures have been completed, the remote UE can further initiate an end-to-end link establishment procedure to another remote UE via the relay between UEs to establish end-to-end security between the remote UE and another remote UE. However, the end-to-end link establishment can be optional.

[0300] In one embodiment, the link modification request message for initiating the layer 2 link modification procedure transmitted by the remote UE to the relay between UEs may include the user information of another remote UE (target user information). The link modification request message may also include the user information of the remote UE (source user information), the Relay Service Code (RSC), and / or Quality of Service (QoS) information 1. In response to receiving the link modification request message, the relay between UEs may initiate a discovery procedure to discover another remote UE or directly initiate a PC5 unicast link establishment procedure to another remote UE.

[0301] The discovery request message for initiating the discovery procedure transmitted by the relay between UEs to another remote UE may include the user information of another remote UE (target user information). The discovery request message may also include the user information of the remote UE (source user information), the user information of the relay between UEs, and / or the Relay Service Code (RSC). In response, another remote UE may reply with a discovery response message.

[0302] A direct communication request message for initiating a PC5 unicast link establishment procedure transmitted from an inter-UE relay to another remote UE may include the user information of the remote UE (source user information) and the user information of another remote UE (destination user information). The direct communication request message may also include the user information of the inter-UE relay, a Relay Service Code (RSC), security information 1, and / or QoS information 1. In response, the other remote UE may reply with a direct communication acceptance message. When receiving the direct communication acceptance message from the other remote UE, the inter-UE relay may transmit a link modification acceptance message to the remote UE. The link modification acceptance message may include the user information of the remote UE (source user information), the user information of another remote UE (destination user information), a Relay Service Code (RSC), and / or QoS information 2.

[0303] The Relay Service Code (RSC) is a parameter for identifying the service requested by the source remote UE (when initiating a connection to the destination remote UE). The QoS information 2 may be different from the QoS information 1, and it may be generated by the other remote UE at least based on the QoS information 1 from the source remote UE. Figure 19 Describe the above solution.

[0304] Figure 20 Flowchart 2000 for illustrating a method for connecting to another UE. In step 2005, a first UE connects to a second UE via a relay UE, where a first PC5 unicast link is established between the first UE and the relay UE. In step 2010, the first UE transmits a link modification request message to the relay UE, where the link modification request message includes the third user information of a third UE. In step 2015, the first UE receives a link modification acceptance message from the relay UE.

[0305] In one embodiment, a second PC5 unicast link may be established between the relay UE and the second UE. The link modification request message may include the first user information of the first UE, a Relay Service Code (RSC), and / or first Quality of Service (QoS) information. The link modification acceptance message may include the first user information of the first UE, the third user information of the third UE, an RSC, and / or second Quality of Service (QoS) information. The second QoS information may be generated by the third UE at least based on the first QoS information.

[0306] In one embodiment, a first UE may initiate an end-to-end unicast link establishment procedure to a third UE via a relay UE. A link modification request message may be transmitted using the layer 2 identity / identifier (ID) of the first UE and the layer 2 ID of the relay UE. A link modification acceptance message may be received using the layer 2 ID of the first UE and the layer 2 ID of the relay UE.

[0307] Return to reference Figure 3 and Figure 4 and, in an exemplary embodiment of the first UE, the first UE 300 includes program code 312 stored in a memory 310. The CPU 308 may execute the program code 312 to enable the first UE to perform the following operations: (i) connect to a second UE via a relay UE, wherein a first PC5 unicast link is established between the first UE and the relay UE; (ii) transmit a link modification request message to the relay UE, wherein the link modification request message includes third user information of a third UE; and (iii) receive a link modification acceptance message from the relay UE. In addition, the CPU 308 may execute the program code 312 to perform all of the actions and steps described above or other actions and steps described herein.

[0308] Various aspects of the present disclosure have been described above. It should be understood that the teachings herein may 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 should understand that the aspects disclosed herein may be implemented independently of any other aspect, and two or more of these aspects may be combined in various ways. For example, any number of the aspects set forth herein may be used to implement an apparatus or practice a method. Additionally, this apparatus may be implemented or this method may be practiced using other structures, functions, or a combination of structures and functions in addition to or different from one or more of the aspects set forth herein. As examples of some of the above concepts, in some aspects, parallel channels may be established based on pulse repetition frequency. In some aspects, parallel channels may be established based on pulse position or offset. In some aspects, parallel channels may be established based on time-hopping sequences. In some aspects, parallel channels may be established based on pulse repetition frequency, pulse position or offset, and time-hopping sequences.

[0309] Those skilled in the art will appreciate that any of a variety of different technologies and techniques may be used to represent information and signals. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or any combination thereof.

[0310] Those of ordinary skill in the art will further appreciate that the various illustrative logical blocks, modules, processors, components, circuits, and algorithm steps described in connection with the aspects disclosed herein can be implemented as electronic hardware (e.g., digital implementations, analog implementations, or combinations thereof, which can be designed using source coding or some other technique), various forms of program or design code incorporating instructions (which may be referred to herein, for convenience, as "software" or "software modules"), or combinations of both. To clearly illustrate this interchangeability of hardware and software, 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 upon the particular application and design constraints imposed on the overall system. Those of ordinary skill in the art may implement the described functionality in different ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

[0311] In addition, the various illustrative logical blocks, modules, and circuits described in connection with the aspects disclosed herein can 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, outside the IC, or in both cases. The general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, e.g., 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.

[0312] It should be understood that any particular order or hierarchy of steps in any disclosed process is an example of an exemplary method. It should be understood that, based on design preferences, the particular order or hierarchy of steps in a process can be rearranged while remaining within the scope of the present disclosure. The appended method claims present the elements of the various steps in an exemplary order, and are not intended to be limited to the specific order or hierarchy presented.

[0313] The steps of a method or algorithm described in connection with the various aspects disclosed herein may be implemented directly in hardware, in a software module executed by a processor, or in a combination of the two. Software modules (e.g., including executable instructions and associated data) and other data may reside in a data memory, 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. An example storage medium may be coupled to a machine such as a computer / processor (for convenience, the machine may be referred to herein as a "processor") such that the processor can read information (e.g., code) from the storage medium and write information to the storage medium. The example storage medium may be integral with the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user device. In an alternative, the processor and the storage medium may reside as discrete components in a user device. Additionally, in some aspects, any suitable computer program product may include a computer-readable medium that includes code associated with one or more aspects of the present disclosure. In some aspects, the computer program product may include packaging material.

[0314] Although the invention has been described in connection with various aspects, it is to 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 known and customary practice within the art to which the invention pertains.

Claims

1. A method for connecting to another user device, characterized in that, Comprising: A first user equipment is connected to a second user equipment via a relay user equipment, wherein a first PC5 unicast link is established between the first user equipment and the relay user equipment; The first user equipment transmits a link modification request message to the relay user equipment, wherein the link modification request message contains third user information of a third user equipment; The first user equipment receives a link modification acceptance message from the relay user equipment; and The first user equipment is connected to the third user equipment via the relay user equipment.

2. The method according to claim 1, wherein A second PC5 unicast link is established between the relay user equipment and the second user equipment.

3. The method according to claim 1, wherein The link modification request message contains first user information of the first user equipment, a relay service code, or first quality of service information.

4. The method according to claim 3, wherein The link modification acceptance message contains the first user information of the first user equipment, the third user information of the third user equipment, the relay service code, or second quality of service information.

5. The method according to claim 4, wherein The second quality of service information is generated by the third user equipment at least based on the first quality of service information.

6. The method according to claim 1, wherein Further comprising: The first user equipment initiates an end-to-end unicast link establishment procedure to the third user equipment via the relay user equipment.

7. The method according to claim 1, characterized in that, The link modification request message is transmitted using the layer 2 identity of the first user equipment and the layer 2 identity of the relay user equipment.

8. The method according to claim 7, characterized in that, The link modification acceptance message is received using the layer 2 identity of the first user equipment and the layer 2 identity of the relay user equipment.

9. A first user equipment, characterized in that, Comprising: A 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: Connect to a second user equipment via a relay user equipment, wherein a first PC5 unicast link is established between the first user equipment and the relay user equipment; Transmit a link modification request message to the relay user equipment, wherein the link modification request message contains third user information of a third user equipment; Receive a link modification acceptance message from the relay user equipment; And Connect to the third user equipment via the relay user equipment.

10. The first user equipment according to claim 9, characterized in that, A second PC5 unicast link is established between the relay user equipment and the second user equipment.

11. The first user equipment according to claim 9, characterized in that, The link modification request message contains first user information of the first user equipment, a relay service code, or first quality of service information.

12. The first user equipment according to claim 11, characterized in that, The link modification acceptance message contains the first user information of the first user equipment, the third user information of the third user equipment, the relay service code, or second quality of service information.

13. The first user equipment according to claim 12, wherein The second quality of service information is generated by the third user equipment at least based on the first quality of service information.

14. The first user equipment according to claim 9, characterized in that, The processor is further configured to execute program code stored in the memory to: initiate an end-to-end unicast link establishment procedure to the third user equipment via the relay user equipment.

15. The first user equipment according to claim 10, wherein Transmit the link modification request message using the layer 2 identity of the first user equipment and the layer 2 identity of the relay user equipment.

16. The first user equipment according to claim 15, characterized in that, Receive the link modification acceptance message using the layer 2 identity of the first user equipment and the layer 2 identity of the relay user equipment.

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