Method and apparatus for sidelink relay

Abstract

The invention relates to a method and equipment for sidelink relay. An embodiment of the present disclosure provides a user equipment (UE) comprising: a transceiver; and a processor coupled to the transceiver. The processor is configured to: establish a first PC5 Radio Resource Control (RRC) connection for a first hop between a first UE and a relay UE, wherein a second PC5 RRC connection for a second hop between the relay UE and a second UE is established; and establishing, via the relay UE, a third PC5 RRC connection of an end-to-end PC5 link between the first UE and the second UE.

Description

Technical Field

[0001] This disclosure relates to wireless communication, and more particularly to methods and apparatus for side link (SL) relay. Background Technology

[0002] For example, SL communication includes New Radio (NR) SL communication and Vehicle-to-Everything (V2X) SL communication, and supports direct communication between User Equipment (UE) and UE. SL communication between two UEs can be performed via the PC5 interface. SL transmission and reception via the PC5 interface are supported both within and outside network coverage (e.g., next-generation (NG) radio access network (RAN) coverage).

[0003] To further explore coverage extension for SL-based communications, UE-to-UE (U2U) relay (also referred to as SL relay in this paper) can be applied. U2U relay scenarios may involve new problems to be solved. Summary of the Invention

[0004] According to embodiments of this disclosure, a first UE may include: a transceiver; and a processor coupled to the transceiver, wherein the processor is configured to: establish a first PC5 radio resource control (RRC) connection at a first hop between the first UE and a relay UE, wherein a second PC5 RRC connection at a second hop between the relay UE and a second UE is established; and a third PC5 RRC connection of an end-to-end PC5 link between the first UE and the second UE is established via the relay UE.

[0005] In some embodiments, the first UE is configured with a first value for a timer for reconfiguration of the first PC5 RRC connection and a second value for a timer for reconfiguration of the third PC5 RRC connection.

[0006] In some embodiments, the processor is further configured to declare a failure of the third PC5 RRC connection upon at least one of the following: the timer for reconfiguration of the third PC5 RRC connection expires, wherein the timer for reconfiguration of the third PC5 RRC connection is started when the first UE transmits an RRC reconfiguration message containing end-to-end PC5 configuration information to the second UE; an RRC reconfiguration failure message is received from the second UE; an SL radio link failure (RLF) is detected on the first hop; the signal strength on the first hop is lower than a first threshold; or a notification message or release message is received from the relay UE, the notification message or the release message indicating that an SL RLF is detected on the second hop, or the signal strength on the second hop is lower than a second threshold.

[0007] In some embodiments, the processor is further configured to immediately release the third PC5 RRC connection upon declaring the failure of the third PC5 RRC connection.

[0008] In some embodiments, the processor is further configured to transmit information indicating the failure of the third PC5 RRC connection to the base station (BS) via the transceiver.

[0009] In some embodiments, the information indicating the failure of the third PC5 RRC connection includes the reason for the failure.

[0010] In some embodiments, the value of the cause of failure includes: end-to-end RLF, end-to-end configuration failure, SL RLF on the first hop, low signal strength on the first hop, SL RLF on the second hop, or low signal strength on the second hop.

[0011] In some embodiments, the processor is further configured to maintain the configuration of the third PC5 RRC connection and initiate the recovery of the third PC5 RRC connection upon declaration of the failure of the third PC5 RRC connection.

[0012] In some embodiments, the processor is further configured to release the third PC5 RRC connection when a recovery timer expires, wherein the recovery timer is started immediately after the recovery of the third PC5 RRC connection is initiated or the failure of the third PC5 RRC connection is declared.

[0013] In some embodiments, in order to maintain the configuration of the third PC5 RRC connection, the processor is configured to instruct the upper layer to maintain a keep-alive procedure for the end-to-end PC5 link.

[0014] In some embodiments, the processor is further configured to determine, after establishing the third PC5 RRC connection, whether to use a Layer 2 identifier (ID) or a local ID in the sidelink relay adaptation protocol (SRAP) header of the first and second hops.

[0015] In some embodiments, when the processor determines that the local ID should be used in the SRAP header of the first hop and the second hop, the processor is configured to: assign the local ID to the first UE and the second UE respectively, or inform the relay UE to assign the local ID to the first UE and the second UE respectively.

[0016] In some embodiments, the processor is further configured to receive, via the transceiver and from the relay UE, an indication to use a Layer 2 ID in the SRAP headers of the first hop and the second hop, or the local IDs of the first UE and the second UE, respectively.

[0017] In some embodiments, the processor is configured to receive the local IDs of the first UE and the second UE respectively via the transceiver and from the BS.

[0018] Another embodiment of this disclosure provides a BS. The BS may include a transceiver and a processor coupled to the transceiver, wherein the processor is configured to transmit end-to-end PC5 configuration information of a PC5 RRC connection of an end-to-end PC5 link between a first UE and a second UE via the transceiver.

[0019] In some embodiments, the processor is configured to receive information indicating a failure of the PC5 RRC connection from the first UE via the transceiver, wherein the information indicates at least one of the following: a timer for reconfiguring the PC5 RRC connection expires; the first UE receives an RRC reconfiguration failure message from the second UE; an SL RLF is detected at a first hop between the first UE and the relay UE; the signal strength at the first hop is lower than a first threshold; an SL RLF is detected at a second hop between the relay UE and the second UE; or the signal strength at the second hop is lower than a second threshold.

[0020] In some embodiments, when the PC5 RRC connection is established, the processor is further configured to determine whether to use a Layer 2 ID or a local ID in the SRAP header of the first hop between the first UE and the relay UE and the second hop between the relay UE and the second UE.

[0021] In some embodiments, where the processor determines that the local ID should be used in the SRAP header of the first hop and the second hop, the processor is configured to assign the local ID to the first UE and the second UE respectively, and transmit the local ID to the first UE and / or the second UE via the transceiver.

[0022] Another embodiment of this disclosure provides a relay UE. The relay UE may include a transceiver and a processor coupled to the transceiver, wherein the processor is configured to: establish a first PC5 RRC connection at a first hop between a first UE and the relay UE; establish a second PC5 RRC connection at a second hop between a second UE and the relay UE; and transmit data units received from the first UE to the second UE.

[0023] In some embodiments, the processor is further configured to assign the local ID in response to receiving an indication from the first UE to assign a local ID to be used in the SRAP headers of the first hop and the second hop.

[0024] In some embodiments, the processor is further configured to determine whether to use a Layer 2 ID or a local ID in the SRAP headers of the first hop and the second hop.

[0025] In some embodiments, where the processor determines that the Layer 2 ID should be used in the SRAP header of the first hop and the second hop, the processor is configured to transmit an indication of the determination to the first UE and the second UE via the transceiver.

[0026] In some embodiments, where the processor determines that the local ID should be used in the SARP header of the first hop and the second hop, the processor is configured to assign the local ID to the first UE and the second UE, respectively.

[0027] Another embodiment of this disclosure provides a method performed by a first UE. The method may include: establishing a first PC5 RRC connection at a first hop between the first UE and a relay UE, wherein a second PC5 RRC connection at a second hop between the relay UE and a second UE is established; and establishing a third PC5 RRC connection of an end-to-end PC5 link between the first UE and the second UE via the relay UE.

[0028] Another embodiment of this disclosure provides a method performed by a BS. The method may include transmitting end-to-end PC5 configuration information for a PC5 RRC connection of an end-to-end PC5 link between a first UE and a second UE.

[0029] Another embodiment of this disclosure provides a method performed by a relay UE. The method may include: establishing a first PC5 RRC connection at a first hop between a first UE and the relay UE; establishing a second PC5 RRC connection at a second hop between a second UE and the relay UE; and transmitting data units received from the first UE to the second UE. Attached Figure Description

[0030] To describe the advantages and features of this application, the description of the application is presented with reference to specific embodiments illustrated in the accompanying drawings. These drawings depict only exemplary embodiments of the application and should therefore not be construed as limiting the scope of the application.

[0031] Figure 1 The illustrations depict schematic diagrams of exemplary wireless communication systems according to some embodiments of the present disclosure.

[0032] Figure 2 The diagram illustrates a flowchart of an exemplary method for SL relay according to some embodiments of the present disclosure.

[0033] Figure 3 The diagram illustrates a flowchart of an exemplary method for SL relay according to some other embodiments of this disclosure.

[0034] Figure 4 The diagram illustrates a flowchart of an exemplary method for SL relay according to some other embodiments of this disclosure.

[0035] Figure 5 The illustrations are simplified block diagrams illustrating exemplary devices according to some embodiments of the present disclosure. Detailed Implementation

[0036] The detailed description of the accompanying drawings is intended to illustrate the presently preferred embodiments of the invention and is not intended to represent the only form in which the invention can be practiced. It should be understood that the same or equivalent functions may be implemented by different embodiments intended to be covered within the spirit and scope of the invention.

[0037] Although operations are depicted in a specific order in the diagrams, those skilled in the art will recognize that it is not necessary to perform such operations in the shown specific order or sequential order, or to perform all the illustrated operations; sometimes one or more operations may be skipped. Furthermore, the diagrams may schematically depict one or more instance processes in the form of flowcharts. However, other undepicted operations may be incorporated into the schematically illustrated instance processes. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the illustrated operations. In certain situations, multitasking and parallel processing may be advantageous.

[0038] Reference will now be made in detail to some embodiments of this disclosure, examples of which are illustrated in the accompanying drawings. To facilitate understanding, embodiments are provided under specific network architectures and new service scenarios (e.g., 3GPP Long Term Evolution (LTE), LTE-A, 3GPP 4G, 3GPP 5G NR, 3GPP Release 16 and later, etc.). Please consider that all embodiments of this disclosure are applicable to similar technical problems as network architectures and new service scenarios evolve; furthermore, the terminology used in this disclosure may be changed without affecting the principles of this disclosure.

[0039] Figure 1 This is a schematic diagram illustrating an exemplary wireless communication system 100 according to some embodiments of this application.

[0040] refer to Figure 1 The wireless communication system 100 may include a BS 101 and a number of UEs (e.g., UE 102a, UE 102b, and UE 102c). Although only one BS 101 and three UEs are shown for simplicity, it should be considered that, according to some other embodiments of this application, the wireless communication system 100 may include any number of BSs or UEs.

[0041] The wireless communication system 100 is compatible with any type of network capable of transmitting and receiving wireless communication signals. For example, the wireless communication system 100 is compatible with: wireless communication networks, cellular telephone networks, time division multiple access (TDMA) based networks, code division multiple access (CDMA) based networks, orthogonal frequency division multiple access (OFDMA) based networks, LTE networks, 3GPP based networks, 3GPP 5G networks, satellite communication networks, high-altitude platform networks, and / or other communication networks.

[0042] BS101 may also be referred to as an access point, access terminal, base station, macro cell, node B, enhanced node B (eNB), next-generation node B (gNB), home node B, relay node, or device, or may be described using other terms used in this technical field. BS101 is typically part of a radio access network that may include a controller communicatively coupled to BS101.

[0043] The UEs (e.g., UE 102a, UE 102b, and UE 102c) within the wireless communication system 100 may include computing devices such as desktop computers, laptop computers, personal digital assistants (PDAs), tablet computers, smart TVs (e.g., TVs connected to the Internet), set-top boxes, game consoles, security systems (including security cameras), in-vehicle computers, network devices (e.g., routers, switches, and modems), etc. According to some embodiments of this disclosure, the UE may include portable wireless communication devices, smartphones, cellular phones, flip phones, devices with a subscriber identity module, personal computers, selective call receivers, or any other devices capable of transmitting and receiving communication signals on a wireless network. In some embodiments of this disclosure, the UEs within the wireless communication system 100 may include wearable devices such as smartwatches, fitness trackers, optical head-mounted displays, etc. Furthermore, each of the UEs within the wireless communication system 100 may be referred to as a subscriber unit, mobile device, mobile station, user, terminal, mobile terminal, wireless terminal, fixed terminal, subscriber station, user terminal, or device, or described using other terms used in this art.

[0044] BS101 can be distributed across a geographical area. When a UE (e.g., UE 102a, UE 102b, or UE 102c) is within the coverage area of ​​BS101, the UE can transmit information or data to and receive control information or data from BS101, for example, via an LTE or NR Uu interface. In some cases, UEs located outside the coverage area of ​​BS101 can communicate with BS101 via one or more relay UEs.

[0045] Two UEs can perform SL communication with each other via a PC5 interface. In some cases, a UE can communicate with another UE via a direct link between them. In other cases, a UE can communicate with another UE via one or more relay UEs. That is, a UE can establish an end-to-end (e2e) PC5 link PC5 RRC connection with another UE via at least one relay UE. For example, such as Figure 1As shown, UE 102a can establish an end-to-end PC5 RRC connection with UE 102b via UE 102c. To achieve this, a first PC5 RRC connection of a direct link between UE 102a and UE 102c can be established, and a second PC5 RRC connection of a direct link between UE 102c and UE 102b can be established. Then, an end-to-end PC5 RRC connection of an end-to-end PC5 link between UE 102a and UE 102b can be established, and UE 102c can act as a relay UE and transmit data units received from one of UE 102a and UE 102b to the other UE. Each of UE 102a and UE 102b can be referred to as a remote UE, meaning that it communicates with the other UE via a relay UE. In the communication direction from UE 102a to UE 102b, the direct link between UE 102a and UE 102c can be called the first hop, and the direct link between UE 102c and UE 102b can be called the second hop, such as... Figure 1 As shown in the image.

[0046] For the sake of simplicity, Figure 1 The example illustrations shown illustrate a single UE-to-UE relay scenario, where only one relay UE (e.g., UE 102c) is used for an end-to-end PC5 link PC5 RRC connection between two UEs (e.g., UE 102a and UE 102b). Consider also supporting multi-hop (more than one hop) UE-to-UE relay scenarios, where more relay UEs are used for an end-to-end PC5 link PC5 RRC connection between two UEs.

[0047] Figure 2 The diagram illustrates a flowchart of an exemplary method 200 for SL relay according to some embodiments of the present disclosure. Figure 2 The method 200 illustrated herein can be performed by at least three entities (e.g., remote UE1 (e.g., UE 102a or UE 102b), remote UE2 (e.g., UE 102b or UE 102a), and relay UE (e.g., UE 102c)). Although method 200 is illustrated at the system level, those skilled in the art will understand that the method implemented in the three entities can be implemented individually and incorporated into other devices with similar functionality. It should also be considered that method 200 may include additional steps not shown. Furthermore, it should be considered that method 200 can be extended to multi-hop UE-to-UE relay scenarios.

[0048] In step 201, the remote UE1 and the relay UE can establish a first PC5 RRC connection at the first hop between them.

[0049] In step 202, the relay UE and the remote UE2 can establish a second PC5 RRC connection at a second hop. Step 202 can occur after, before, or simultaneously with step 201.

[0050] In step 203, after establishing the first PC5 RRC connection and the second PC5 RRC connection, remote UE1 and remote UE2 can establish a third PC5 RRC connection of the end-to-end PC5 link between them via the relay UE.

[0051] In step 204, after establishing a third PC5 RRC connection between remote UE1 and remote UE2, some configurations can be exchanged between remote UE1 and remote UE2. For example, remote UE1 can transmit an RRC reconfiguration message transparent to the relay UE to remote UE2 via the relay UE. In some embodiments, the RRC reconfiguration message may carry end-to-end PC5 configuration information (or parameters). In some embodiments, the end-to-end PC5 configuration information may include end-to-end Service Data Adaptation Protocol (SDAP) and Packet Data Convergence Protocol (PDCP) configuration parameters associated with a Quality of Service (QoS) profile.

[0052] In some embodiments, end-to-end PC5 configuration information may be pre-configured to remote UE1. This may mean that the end-to-end PC5 configuration information may be hard-wired to remote UE1 or stored on the subscriber identity module (SIM) or universal subscriber identity module (USIM) card of remote UE1, so that remote UE1 can obtain the end-to-end PC5 configuration information within remote UE1. In some embodiments, for example, when remote UE1 is within the coverage area of ​​BS (e.g., BS101), remote UE1 may receive end-to-end PC5 configuration information from BS.

[0053] In some embodiments, the remote UE1 is configured with a first value for a first timer for reconfiguration of a first PC5 RRC connection and a second value for a second timer for reconfiguration of a third PC5 RRC connection. In some embodiments, the first value may be different from the second value. For example, the second value may be greater than the first value, considering that the third PC5 RRC connection involves more hops than the first PC5 RRC connection. In some embodiments, both the first and second timers may be T400 as defined in the 3GPP standard document. In some other embodiments, the first timer may be T400, while the second timer may be a different timer.

[0054] In some embodiments, the second value is associated with the number of relay UEs involved in a third PC5 RRC connection of an end-to-end PC5 link between remote UE1 and remote UE2. For example, remote UE1 may be configured with a timer value #1 for reconfiguration of a PC5 RRC connection involving only one relay UE, a timer value #2 for reconfiguration of a PC5 RRC connection involving two relay UEs, and a timer value #3 for reconfiguration of a PC5 RRC connection involving three relay UEs; these values ​​may be different from each other.

[0055] When remote UE1 transmits an RRC reconfiguration message for the third PC5 RRC connection, it can start a second timer.

[0056] In step 205, remote UE1 can receive a response from remote UE2 via relay UE.

[0057] In the case where the response is an RRC reconfiguration complete message, the configuration between remote UE1 and remote UE2 is successful. Upon receiving the RRC reconfiguration complete message, remote UE1 can immediately stop the second timer. Then, data can be transmitted from remote UE1 to remote UE2.

[0058] In the case where the response is an RRC reconfiguration failure message, configuration between remote UE1 and remote UE2 has failed. Upon receiving the RRC reconfiguration failure message, remote UE1 may immediately stop the second timer and declare a failure of the third PC5RRC connection. In this case, the failure can be attributed to an end-to-end configuration failure.

[0059] In some embodiments, remote UE1 may not receive any response from remote UE2 before the second timer expires. Then, after the second timer expires, remote UE1 may immediately declare a failure of the third PC5 RRC connection. In this case, the failure can be attributed to an end-to-end RRC failure.

[0060] Figure 3 The diagram illustrates a flowchart of an exemplary method 300 for SL relay according to some embodiments of the present disclosure.

[0061] Figure 3The method 300 illustrated herein can be performed by at least four entities (e.g., remote UE1 (e.g., UE 102a or UE 102b), remote UE2 (e.g., UE 102b or UE 102a), relay UE (e.g., UE 102c), and BS (e.g., BS 101)). Although method 300 is illustrated at the system level, those skilled in the art will understand that the method implemented in the four entities can be implemented individually and incorporated into other devices with similar functionality. It should also be considered that method 300 may include additional steps not shown. Furthermore, it should be considered that method 300 can be extended to multi-hop UE-to-UE relay scenarios.

[0062] Steps 301, 302, and 303 can be the same as steps 201, 202, and 203, respectively. That is, in step 301, a first PC5 RRC connection can be established at the first hop between remote UE1 and the relay UE; in step 302, a second PC5 RRC connection can be established at the second hop between the relay UE and remote UE2; and in step 303, after establishing the first and second PC5 RRC connections, a third PC5 RRC connection can be established for the end-to-end PC5 link between remote UE1 and remote UE2. After establishing the third PC5 RRC connection between remote UE1 and remote UE2, some configurations can be exchanged between them. For example, remote UE1 can transmit an RRC reconfiguration message, as described above.

[0063] In step 304, the remote UE1 may declare a failure of the third PC5 RRC connection if at least one of the following occurs:

[0064] • The timer used for reconfiguration of the third PC5 RRC connection (e.g., the second timer described above) expires;

[0065] • Received an RRC reconfiguration failure message from remote UE2;

[0066] • SL RLF was detected at the first hop;

[0067] • The signal strength at the first hop is lower than the first threshold; or

[0068] • A notification message or release message is received from the relay UE, the notification message or the release message indicating that an SL RLF is detected at the second hop, or the signal strength at the second hop is lower than a second threshold.

[0069] Please consider that in cases where more relay UEs are involved in the third PC5 RRC connection, there will be more situations that cause remote UE1 to declare the failure of the third PC5 RRC connection.

[0070] A SL RLF is detected at a hop (e.g., first hop, second hop, etc.) if at least one of the following conditions is met:

[0071] • Receive an indication from the SL Radio Link Control (RLC) entity indicating the maximum number of retransmissions that have been made to a specific destination;

[0072] • The timer for PC5 RRC reconfiguration at a specific destination has expired;

[0073] • Receive an indication from the Media Access Control (MAC) entity indicating the maximum number of consecutive Hybrid Automatic Repeat Request (HARQ) discontinuous transmissions (DTX) that have reached a specific destination; or

[0074] • Receive an integrity check failure indication from the SL PDCP entity related to a sidelink signaling radio bearer (SL-SRB)2 or SL-SRB3 for a specific destination.

[0075] In step 305, after declaring the failure of the third PC5 RRC connection, the remote UE1 may release the third PC5 RRC connection. In some embodiments, after declaring the failure of the third PC5 RRC connection, the remote UE1 may immediately further release the configuration of the third PC5 RRC connection. For example, the remote UE1 may perform at least one of the following operations:

[0076] • Release the end-to-end data radio bearer (DRB) associated with remote UE2;

[0077] • Release the end-to-end signaling radio bearer (SRB) associated with remote UE2;

[0078] • Release the PC5 trunk RLC channel at the first hop (if configured);

[0079] • Discard the NR-side walkway communication configuration related to the first hop;

[0080] • Reset the lateral MAC address of the first hop;

[0081] • Consider releasing the end-to-end PC5 RRC connection of remote UE2;

[0082] • Indicate to the upper layer of remote UE2 the release of the end-to-end PC5 RRC connection (i.e., the end-to-end PC5 RRC connection is unavailable).

[0083] Although not shown, remote UE2 can also release the third PC5 RRC connection and the configuration of the third PC5 RRC connection in a similar manner.

[0084] After releasing the third PC5 RRC connection, the remote UE2 can perform a relay reselection procedure to establish a new end-to-end PC5 RRC connection with the remote UE2.

[0085] In some embodiments, where the remote UE1 is within the coverage area of ​​the BS, in step 306, after declaring the failure of the third PC5 RRC connection, the remote UE1 may transmit information indicating the failure of the third PC5 RRC connection to the BS. For example, the remote UE1 may transmit SL UE information containing information indicating the failure. The information may include the reason for the failure. The failure information may be one of e2e RLF, e2e configuration failure, RLF on the first hop, low signal strength on the first hop, sidelink RLF on the second hop, or low signal strength on the second hop. For example, the information may be a parameter sl-Failure defined as the following:

[0086] sl-Failure enumeration {

[0087] e2e RLF, e2e configuration failure, RLF on the first hop, low signal strength on the first hop, sidelink RLF on the second hop, low signal strength on the second hop

[0088] }

[0089] Each value can represent a reason for failure, as follows:

[0090] • e2e RLF: The timer for reconfiguration of the third PC5 RRC connection (e.g., the second timer described above) has expired;

[0091] • e2e configuration failure: Received an RRC reconfiguration failure message from remote UE2;

[0092] • RLF on the first hop: SL RLF detected on the first hop;

[0093] • Low signal strength at the first hop: The signal strength at the first hop is lower than the first threshold;

[0094] • Side Link RLF on the second hop: SL RLF on the second hop was detected; and

[0095] • Low signal strength at the second hop: The signal strength at the second hop is lower than the second threshold.

[0096] Please consider that in scenarios involving more relay UEs in a third PC5 RRC connection, sl-Failure may have more possible values.

[0097] Figure 4The diagram illustrates a flowchart of an exemplary method 400 for SL relay according to some embodiments of the present disclosure.

[0098] Figure 4 The method 400 illustrated herein can be performed by at least three entities (e.g., remote UE1 (e.g., UE 102a or UE 102b), remote UE2 (e.g., UE 102b or UE 102a), and relay UE (e.g., UE 102c)). Although method 400 is illustrated at the system level, those skilled in the art will understand that the method implemented in the three entities can be implemented individually and incorporated into other devices with similar functionality. It should also be considered that method 400 may include additional steps not shown. Furthermore, it should be considered that method 400 can be extended to multi-hop UE-to-UE relay scenarios.

[0099] Steps 401, 402, and 403 can be the same as steps 201, 202, and 203, respectively. That is, in step 401, a first PC5 RRC connection can be established at the first hop between remote UE1 and the relay UE; in step 402, a second PC5 RRC connection can be established at the second hop between the relay UE and remote UE2; and in step 403, after establishing the first and second PC5 RRC connections, a third PC5 RRC connection can be established for the end-to-end PC5 link between remote UE1 and remote UE2. After establishing the third PC5 RRC connection between remote UE1 and remote UE2, some configurations can be exchanged between them. For example, remote UE1 can transmit an RRC reconfiguration message, as described above.

[0100] In step 404, when a specific condition occurs (e.g., at least one condition described above with respect to step 304), the remote UE1 may declare a failure of the third PC5 RRC connection, but it continues to maintain the configuration of the third PC5 RRC connection; this is permitted because the configuration of the third PC5 RRC connection is transparent to the relay UE. In some embodiments, where the remote UE1 is within the coverage area of ​​the BS, after declaring the failure of the third PC5 RRC connection, the remote UE1 may transmit information indicating the failure of the third PC5 RRC connection to the BS, as described above with respect to step 306.

[0101] In step 405, remote UE1 may execute a recovery procedure (i.e., initiate the recovery of the third PC5 RRC connection) to reselect a candidate relay UE to re-establish the PC5 RRC connection of the end-to-end PC5 link between remote UE1 and remote UE2 by reusing the configuration of the third PC5 RRC connection; this helps to save signaling overhead and improve process efficiency.

[0102] To maintain the configuration of the third PC5 RRC connection, remote UE1 can instruct the upper layer to maintain a keep-alive procedure for the end-to-end PC5 link between remote UE1 and remote UE2, so that the end-to-end PC5 link between remote UE1 and remote UE2 will not be released even when the timer for the keep-alive procedure expires.

[0103] In some embodiments, remote UE1 may be configured with a recovery timer. Upon declaring a failure of the third PC5 RRC connection or initiating the recovery of the third PC5 RRC connection, remote UE1 may immediately start the recovery timer. When a candidate relay UE is selected or a PC5 RRC connection to a candidate relay UE is established, remote UE1 may stop the recovery timer. Upon expiration of the recovery timer, remote UE1 may release the third PC5 RRC connection. The configuration of the third PC5 RRC connection is also immediately released after the recovery timer expires.

[0104] After establishing an end-to-end PC5 RRC connection between the first remote UE and the second remote UE, SRAP packets can be transmitted from the first remote UE to the second remote UE via at least one relay UE. The SRAP header for each hop may contain an ID associated with both the first and second remote UEs. For example, this ID may be a Layer 2 ID or a local ID. A Layer 2 ID may contain 24 bits, while a local ID may contain fewer bits than a Layer 2 ID. It is necessary to determine which ID to use in the SRAP header for each hop.

[0105] In some embodiments, the first remote UE may decide which ID to use in the SRAP header of the hop.

[0106] If the first remote UE decides to use the Layer 2 ID in the SRAP header of the hop, then no further switching configuration is required.

[0107] If the first remote UE decides to use a local ID in the SRAP header of a hop, it can assign local IDs to both the first and second remote UEs, and transmit the assigned local IDs to at least one of the second remote UE and the relay UE. Alternatively, the first remote UE can inform the relay UE to assign local IDs to both the first and second remote UEs; and then the relay UE can assign local IDs to both the first and second remote UEs and transmit the local IDs to both.

[0108] In some embodiments, the relay UE may decide which ID to use in the SRAP header of the hop.

[0109] If a relay UE decides to use a Layer 2 ID in the SRAP header of a hop, it can transmit an indication to the first remote UE and the second remote UE to indicate that it will use a Layer 2 ID in the SRAP header of the hop.

[0110] If a relay UE decides to use a local ID in the SRAP header of a hop, it can assign local IDs to the first remote UE and the second remote UE respectively, and transmit the assigned local IDs to the first remote UE and the second remote UE.

[0111] In some embodiments, where the first remote UE is within the coverage area of ​​the BS, the BS may determine which ID to use in the SRAP header of the hop.

[0112] If the BS decides to use the Layer 2 ID in the SRAP header of the hop, then no further switching configuration is required.

[0113] If the BS decides to use a local ID in the SRAP header of a hop, it can assign local IDs to both the first and second remote UEs. The BS can transmit the assigned local IDs to the first and / or second remote UEs (any remote UE within the BS's coverage area). If one of the first and second remote UEs is within the BS's coverage area while the other is outside, the UE within the coverage area can forward the received local IDs to the UE outside the coverage area.

[0114] Figure 5 The illustration shows a simplified block diagram of an exemplary device 500 according to some embodiments of the present disclosure.

[0115] like Figure 5 As shown, an instance of device 500 may include at least one processor 501 and at least one transceiver 502 coupled to the processor 501. Device 500 may be a remote UE, a relay UE, a BS, or any other device with similar functionality.

[0116] Although elements such as transceiver 502 and processor 501 are described in the singular in this figure, please consider the plural unless explicitly stated otherwise. In some embodiments of this disclosure, transceiver 502 may be divided into two devices, such as a receiving circuitry system and a transmitting circuitry system. In some embodiments of this disclosure, device 500 may further include input devices, memory, and / or other components.

[0117] In some embodiments of this disclosure, device 500 may be a remote UE. Transceiver 502 and processor 501 may interact with each other to perform operations of the remote UE, such as regarding Figures 2 to 4As described in any of the embodiments described in this disclosure or other embodiments described herein. For example, processor 501 may be configured to: establish a first PC5 RRC connection at a first hop between a remote UE and a relay UE, and establish a third PC5 RRC connection of an end-to-end PC5 link between a remote UE and a second remote UE via the relay UE, wherein a second PC5 RRC connection at a second hop between the relay UE and the second remote UE is established.

[0118] In some embodiments of this disclosure, device 500 may be a BS (Browser / Server). Transceiver 502 and processor 501 may interact with each other to perform BS operations, such as regarding... Figures 2 to 4 As described in any of the embodiments described in this disclosure or other embodiments described herein. For example, processor 501 may be configured to transmit end-to-end PC5 configuration information of the PC5 RRC connection of the end-to-end PC5 link between the first remote UE and the second remote UE via transceiver 502.

[0119] In some embodiments of this disclosure, device 500 may be a relay UE. Transceiver 502 and processor 501 may interact with each other to perform operations of the relay UE, such as regarding... Figures 2 to 4 As described in any of the embodiments described in this disclosure or other embodiments described herein. For example, processor 501 may be configured to: establish a first PC5 RRC connection at a first hop between a first remote UE and a relay UE; establish a second PC5 RRC connection at a second hop between a second remote UE and a relay UE; and transmit data units received from the first remote UE to the second remote UE.

[0120] In some embodiments of this disclosure, device 500 may further include at least one non-transitory computer-readable medium.

[0121] For example, in some embodiments of this disclosure, a non-transitory computer-readable medium may store computer-executable instructions thereon to cause processor 501 to perform any of the methods described above with respect to a UE (e.g., a remote UE or a relay UE). For example, when executed, the computer-executable instructions may cause processor 501 to interact with transceiver 502 to perform operations of the UE, such as those described regarding... Figures 2 to 4 As described in any of the embodiments or other embodiments described in this disclosure.

[0122] In some embodiments of this disclosure, a non-transitory computer-readable medium may store computer-executable instructions thereon to cause processor 501 to perform any of the methods described above with respect to the BS. For example, when executed, the computer-executable instructions may cause processor 501 to interact with transceiver 502 to perform operations of the BS, such as those described above. Figures 2 to 4 Or as described in other embodiments described in this disclosure.

[0123] The methods disclosed herein can be implemented on a programmable processor. However, the controller, flowcharts, and modules can also be implemented on general-purpose or special-purpose computers, programmable microprocessors or microcontrollers and peripheral integrated circuit elements, integrated circuits, hardware electronics or logic circuits (e.g., discrete element circuits), programmable logic devices, and the like. Generally speaking, any device having a finite state machine capable of implementing the flowcharts shown in the figures can be used to implement the processing functions of this disclosure.

[0124] Although this disclosure has been described through specific embodiments, it will be apparent to those skilled in the art that many alternatives, modifications, and variations will be understood. For example, various components of the embodiments may be interchanged, added, or substituted in other embodiments. Furthermore, not all elements shown in each figure are essential for the operation of the disclosed embodiments. For example, those skilled in the art will be able to make and use the teachings of this disclosure by simply employing elements of independent technical solutions. Therefore, the embodiments of this disclosure set forth herein are intended to be illustrative rather than restrictive. Various changes may be made without departing from the spirit and scope of this disclosure.

[0125] In this disclosure, relational terms such as "first," "second," etc., are used only to distinguish one entity or action from another, and do not necessarily require or imply any actual relationship or order between these entities or actions. The terms "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements does not only include those elements, but may include other elements not expressly listed or inherent to the process, method, article, or apparatus. The prefixes "a" (a, an), etc., preceding an element do not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element without further constraints. Furthermore, the term "another" is defined as at least a second or more. As used herein, the terms "including," "having," etc., are defined as "including."

Claims

1. A first user equipment (UE), comprising: transceiver; and A processor, coupled to the transceiver and configured to: Establish a first PC5 Radio Resource Control (RRC) connection at the first hop between the first UE and the relay UE, wherein a second PC5 RRC connection is established at the second hop between the relay UE and the second UE; and A third PC5 RRC connection is established via the relay UE to establish an end-to-end PC5 link between the first UE and the second UE.

2. The first UE according to claim 1, wherein the first UE is configured with a first value of a timer for reconfiguration of the first PC5 RRC connection and a second value of a timer for reconfiguration of the third PC5 RRC connection.

3. The first UE according to claim 2, wherein the processor is further configured to declare a failure of the third PC5 RRC connection upon at least one of the following: The timer for reconfiguring the third PC5 RRC connection expires, wherein the timer for reconfiguring the third PC5 RRC connection is started when the first UE transmits an RRC reconfiguration message containing end-to-end PC5 configuration information to the second UE; Receives an RRC reconfiguration failure message from the second UE; A sidelink radio link failure (RLF) was detected on the first hop. The signal strength at the first hop is lower than the first threshold; or The relay UE receives a notification message or a release message, the notification message or the release message indicating that an SL RLF is detected on the second hop, or that the signal strength on the second hop is lower than a second threshold.

4. The first UE according to claim 3, wherein the processor is further configured to immediately release the third PC5 RRC connection upon declaration of the failure of the third PC5 RRC connection.

5. The first UE according to claim 3, wherein the processor is further configured to transmit information indicating the failure of the third PC5 RRC connection to the base station BS via the transceiver.

6. The first UE according to claim 5, wherein the information indicating the failure of the third PC5 RRC connection includes the reason for the failure.

7. The first UE according to claim 6, wherein the value of the cause of failure includes: End-to-end RLF, End-to-end configuration failed. SL RLF at the first hop point The low signal strength at the first hop point SL RLF at the second hop, or The low signal strength at the second hop.

8. The first UE according to claim 3, wherein the processor is further configured to: Upon declaring the failure of the third PC5 RRC connection, maintain the configuration of the third PC5 RRC connection and initiate the recovery of the third PC5 RRC connection.

9. The first UE according to claim 8, wherein the processor is further configured to: The third PC5 RRC connection is released when the recovery timer expires, wherein the recovery timer is started immediately after the recovery of the third PC5 RRC connection is initiated or the failure of the third PC5 RRC connection is declared.

10. The first UE of claim 8, wherein, in order to maintain the configuration of the third PC5 RRC connection, the processor is configured to: The upper layer is instructed to maintain a keep-alive procedure for the end-to-end PC5 link.

11. The first UE of claim 1, wherein the processor is further configured to determine, after establishing the third PC5 RRC connection, whether to use a Layer 2 identifier ID or a local ID in the sidelink relay adaptation protocol SRAP header of the first hop and the second hop.

12. The first UE of claim 11, wherein in the case where the processor determines to use the local ID in the SRAP header of the first hop and the second hop, the processor is configured to: Assign the local ID to the first UE and the second UE respectively; or The relay UE is instructed to assign the local ID to both the first UE and the second UE.

13. The first UE of claim 1, wherein the processor is further configured to receive, via the transceiver and from the relay UE: Indicates the use of Layer 2 ID in the SRAP headers of the first hop and the second hop; or The local IDs of the first UE and the second UE, respectively.

14. The first UE according to claim 1, wherein the processor is configured to: The transceiver receives the local IDs of the first UE and the second UE from the BS.

15. A base station (BS), comprising: transceiver; and A processor, coupled to the transceiver and configured to: The transceiver transmits end-to-end PC5 configuration information of the PC5 Radio Resource Control (RRC) connection of the end-to-end PC5 link between the first user equipment (UE) and the second UE.

16. The BS of claim 15, wherein the processor is configured to receive information indicating a failure of the PC5 RRC connection from the first UE via the transceiver, and wherein the information indicates at least one of the following: The timer for reconfiguring the PC5 RRC connection has expired; The first UE receives an RRC reconfiguration failure message from the second UE; A sidelink radio link failure (RLF) was detected at the first hop between the first UE and the relay UE; The signal strength at the first hop is lower than the first threshold; SL RLF was detected at the second hop between the relay UE and the second UE; or The signal strength at the second hop is lower than the second threshold.

17. The BS of claim 15, wherein, in the case where the PC5 RRC connection is established, the processor is further configured to determine whether to use a Layer 2 identifier ID or a local ID in the sidelink trunk adaptation protocol SRAP header at the first hop between the first UE and the trunk UE and the second hop between the trunk UE and the second UE.

18. The BS of claim 17, wherein in the case where the processor determines to use the local ID in the SRAP header of the first hop and the second hop, the processor is configured to: The local IDs are assigned to the first UE and the second UE respectively; and The local ID is transmitted to the first UE and / or the second UE via the transceiver.

19. A relay user equipment (UE), comprising: transceiver; and A processor, coupled to the transceiver and configured to: Establish a first PC5 radio resource control (RRC) connection at the first hop between the first UE and the relay UE; Establish a second PC5 RRC connection at the second hop point between the second UE and the relay UE; and The data unit received from the first UE will be transmitted to the second UE.

20. The relay UE of claim 19, wherein the processor is further configured to: In response to receiving an indication from the first UE to assign a local identifier ID to be used in the sidelink relay adaptation protocol SRAP header at the first hop and the second hop, the local ID is assigned.

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