Path switching for UE-to-UE relay communications

Abstract

A wireless communication method for use in a first wireless terminal is disclosed. The method comprises: receiving, from a first wireless network node, a sidelink (SL) measurement configuration associated with a user-to-user relay for a first wireless terminal and a second wireless terminal; and sending a measurement report to the first wireless network node based on the measurement configuration.

Description

[0001] This document relates generally to wireless communications, and in particular to sidelink (SL) communications, particularly in fifth generation communications.

[0002] With the development of wireless multimedia services, the demand for high data rates and good user experience continues to increase, resulting in higher requirements for the system capacity and coverage of conventional cellular networks. On the other hand, due to application scenarios such as public safety, social networks, near-field data sharing, and local advertising, the demand for proximity services is also increasing. Traditionally, cellular networks using base stations as the center may have obvious limitations in supporting high data rates and proximity services. In order to meet such requirements, device-to-device (D2D) communication technology is proposed. By applying D2D communication technology, the burden on cellular networks can be reduced, the power consumption of user equipment (UE) can be reduced, the data rate can be increased, and the robustness of network infrastructure can be improved. Therefore, the demand for high data rates and proximity services is greatly met. In this context, D2D communication technology is also called proximity service (ProSe) or side link (SL) communication, where the interface between UEs is called PC5 interface.

[0003] In order to support a wider range of applications and services (e.g., indoor relay communication, smart agriculture, smart factories, public safety, etc.), sidelink-based relay communication can be used to extend coverage and improve power consumption. For example, sidelink-based communication can be applied to Figure 1 Two application scenarios are shown:

[0004] 1) UE to Network Relay (Mode 1): This type of relay is used for UEs in weak coverage areas / no coverage areas. Figure 1 In the example, UE1 in a weak coverage area / no coverage area is allowed to communicate with the network (e.g., base station) via UE2 under the coverage of the network. UE-to-network relay can help network operators expand the coverage of the network and increase the capacity of the network. Note that in Figure 1 In the example, UE1 may be referred to as a remote UE, and UE2 may be referred to as a UE-to-network relay.

[0005] 2) UE-to-UE relay (Mode 2): For emergency scenarios where the network is not functioning properly (e.g., earthquake) or to extend the sidelink communication range, UEs may be allowed to communicate with each other via (one or more) relay UEs. For example, Figure 1 UE3 and UE4 in the example communicate with each other via UE5 or multiple relay UEs. UE5 may be referred to as a UE-to-UE (U2U) relay.

[0006] Regarding U2U relay, when the source UE (e.g. Figure 1 UE3 in the example) and the target UE (e.g. Figure 4 When the source UE and the target UE4) are within the SL communication range of each other, the source UE can communicate directly with the target UE. Due to the movement of the source UE and / or the target UE, the source UE may not be able to communicate directly with the target UE, and it is necessary to find and search for a U2U relay for relaying data between the source UE and the target UE. That is, the communication path between the source UE and the target UE can be switched from a direct SL to a U2U relay link (e.g., an indirect SL). In addition, the communication path between the source UE and the target UE can be switched from a U2U relay link to a direct SL. For U2U relay-related technologies, it is necessary to consider how to perform path switching and how to ensure data service continuity during path switching.

[0007] This document relates to methods, systems, and devices for path switching for SL communications, and in particular to methods, systems, and devices for path switching for U2U relay communications.

[0008] The present disclosure relates to a wireless communication method used in a first wireless terminal. The method includes:

[0009] receiving, from the first radio network node, a sidelink SL measurement configuration associated with a user-to-user relay for the first wireless terminal and the second wireless terminal, and

[0010] A measurement report is sent to the first radio network node based on the measurement configuration.

[0011] Various embodiments may preferably implement the following features:

[0012] Preferably, the SL measurement configuration comprises at least one of: at least one threshold used in a measurement reporting event, a filtering criterion for filtering measurement reports triggered by a measurement reporting event, or a measurement quantity associated with user-to-user relaying.

[0013] Preferably, the measurement report event includes at least one of the following: the link quality of the direct SL between the first wireless terminal and the second wireless terminal is lower than a first threshold; the link quality of the direct SL between the first wireless terminal and the second wireless terminal is lower than a second threshold, and the link quality of the first hop between the first user-to-user relay candidate and the first wireless terminal is greater than a third threshold; the link quality of the first hop between the second user-to-user relay candidate and the first wireless terminal is greater than a fourth threshold; the link quality of the first hop between the third user-to-user relay candidate and the first wireless terminal and the link quality of the second hop between the third user-to-user relay candidate and the second wireless terminal are greater than a fifth threshold; the link quality of the first hop and the second hop of the indirect SL is lower than a sixth threshold, wherein the first hop is between the first wireless terminal and a user-to-user relay serving the indirect SL for the first wireless terminal and the second wireless terminal, and the second hop is between the second wireless terminal and the user-to-user relay serving the indirect SL for the first wireless terminal and the second wireless terminal; or the link quality of the direct SL between the first wireless terminal and the second wireless terminal is greater than a seventh threshold.

[0014] Preferably, the filtering criteria include at least one of the following: an eighth threshold, which is configured to filter out the fourth user-to-user relay candidate if the link quality of the first hop between the fourth user-to-user relay candidate and the first wireless terminal is lower than the eighth threshold; or a ninth threshold, which is configured to filter out the fifth user-to-user relay candidate if the link quality of the second hop between the fifth user-to-user relay candidate and the second wireless terminal is lower than the ninth threshold.

[0015] Preferably, the SL measurement configuration is associated with an identifier ID of the second wireless terminal.

[0016] Preferably, the wireless communication method further comprises: receiving, from the first wireless network node, a path switching configuration indicating a path switching toward an indirect SL, the indirect SL being between the first wireless terminal and the second wireless terminal and being served by the third wireless terminal,

[0017] Preferably, the path switch configuration includes at least one of the following: an ID of the second wireless terminal, an ID of the third wireless terminal, or a timer value of a path switch timer associated with the path switch.

[0018] Preferably, the wireless communication method further comprises: starting a path switching timer when the path switching configuration is received.

[0019] Preferably, the wireless communication method also includes: stopping the path switching timer when at least one of the following occurs: when a first PC5 link between the first wireless terminal and the third wireless terminal and a second PC5 link between the third wireless terminal and the second wireless terminal are established; successfully sending a radio resource control RRC reconfiguration SL message to the third wireless terminal; receiving a PC5 radio link control response from the third wireless terminal; receiving an RRC reconfiguration completion SL message from the third wireless terminal; receiving a packet data convergence protocol PDCP response from the second wireless terminal; receiving an end-to-end direct communication response from the second wireless terminal via the third wireless terminal from the third wireless terminal; successfully sending an end-to-end Layer 2 link modification request message to the third wireless terminal, or receiving an end-to-end Layer 2 link modification acceptance message from the third wireless terminal.

[0020] Preferably, when the path switching timer expires, the method further comprises at least one of the following: initiating a relay reselection process, or sending information of path switching failure to the first radio network node.

[0021] Preferably, the wireless communication method also includes: sending information to the first wireless network node, the information including at least one of the following: a path switching failure indication, a PC5 link establishment failure indication, the ID of the second wireless terminal, an indication of the first hop between the first wireless terminal and the third wireless terminal, or an indication of the second hop between the third wireless terminal and the second wireless terminal.

[0022] Preferably, the wireless communication method further comprises: receiving a failure report from the third wireless terminal, the failure report indicating a failure in establishing the PC5 link between the third wireless terminal and the second wireless terminal.

[0023] Preferably, the wireless communication method also includes at least one of the following: sending an end-to-end PC5 RRC reconfiguration message indicating PDCP data recovery to the second wireless terminal; sending an end-to-end PC5 RRC message indicating PDCP reconstruction to the second wireless terminal; receiving an end-to-end PC5 RRC reconfiguration message indicating PDCP data recovery from the second wireless terminal; receiving an end-to-end PC5 RRC message indicating PDCP reconstruction from the second wireless terminal; receiving a SL configuration from the first wireless network node, the SL configuration including at least one of the following: an indication of PDCP data recovery for the SL between the first wireless terminal and the second wireless terminal, an indication of PDCP data recovery for each end-to-end SL data radio bearer DRB of the SL between the first wireless terminal and the second wireless terminal, an indication of PDCP reconstruction for the SL between the first wireless terminal and the second wireless terminal, or an indication of PDCP reconstruction for each end-to-end SL DRB of the SL between the first wireless terminal and the second wireless terminal; or performing PDCP data recovery or PDCP reconstruction after a path switch toward an indirect SL, which is between the first wireless terminal and the second wireless terminal and is served by a third wireless terminal.

[0024] Preferably, the wireless communication method further comprises: receiving information of the second wireless terminal from a third wireless terminal.

[0025] Preferably, the information of the second wireless terminal includes at least one of the following: radio resource control status, serving cell information, or out-of-coverage indication.

[0026] Preferably, the wireless communication method further comprises: sending information of the second wireless terminal to the first wireless network node,

[0027] Preferably, the information of the second wireless terminal includes at least one of the following: radio resource control status, serving cell information, or out-of-coverage indication.

[0028] Preferably, the wireless communication method further includes: sending a measurement configuration including the ID of the second wireless terminal to a third wireless terminal serving the indirect SL between the first wireless terminal and the second wireless terminal.

[0029] Preferably, the first radio network node sends the SL information to a third radio network node serving the second wireless terminal.

[0030] Preferably, the SL related information is (sent / generated) based on the SL measurement report and the information of the second wireless terminal received from the first wireless terminal UE.

[0031] Preferably, the SL-related information includes at least one of the following: the ID of the first wireless terminal, the ID of the second wireless terminal, a list of user-to-user relay candidates, the selected user-to-user relay, the RRC state of each user-to-user relay candidate, the PC5 link quality between the first wireless terminal and each user-to-user relay candidate, or the PC5 link quality between each user-to-user relay candidate and the second wireless terminal.

[0032] Preferably, the first radio network node receives from the third radio network node a selected user-to-user relay for the first wireless terminal and the second wireless terminal (to relay data transmissions between them).

[0033] The present disclosure relates to a wireless communication method used in a third wireless terminal, the method comprising: receiving a side link SL configuration associated with a user-to-user relay between a first wireless terminal and a second wireless terminal from a wireless network node serving the third wireless terminal, and establishing a first PC5 link with the first wireless terminal and establishing a second PC5 link with the second wireless terminal based on the SL configuration.

[0034] Various embodiments may preferably implement the following features:

[0035] Preferably, the SL configuration includes at least one of the following: a user-to-user relay indication, at least one identifier ID associated with the first wireless terminal and the second wireless terminal, a bearer mapping associated with an end-to-end SL radio bearer SLRB to a PC5 radio link control RLC channel of a first hop on an indirect SL, wherein the first hop is between a third wireless terminal and the first wireless terminal, and the indirect SL is between the first wireless terminal and the second wireless terminal and passes through the third wireless terminal, or a bearer mapping associated with an end-to-end SL SLRB to a PC5 RLC channel of a second hop on the indirect SL, wherein the second hop is between the third wireless terminal and the second wireless terminal, and the indirect SL is between the first wireless terminal and the second wireless terminal and passes through the third wireless terminal.

[0036] Preferably, the bearer mapping includes at least one of the following: end-to-end SLRB ID, PC5 RLC channel ID of the first hop, PC5 RLC channel ID of the second hop, ingress PC5 RLC channel ID, egress PC5 RLC channel ID, PC5 RLC channel ID between the first wireless terminal and the third wireless terminal, or PC5 RLC channel ID between the third wireless terminal and the second wireless terminal.

[0037] Preferably, the wireless communication method further comprises: sending a failure report indicating a failure in establishing the second PC5 link to the first wireless terminal.

[0038] Preferably, the wireless communication method further comprises: sending information of the second wireless terminal to the first wireless terminal, wherein the information comprises at least one of the following: radio resource control status, serving cell information, or out-of-coverage indication.

[0039] Preferably, the wireless communication method further comprises: receiving a measurement configuration including an ID of the second wireless terminal from the first wireless terminal.

[0040] The present disclosure relates to a wireless communication method used in a first wireless network node, the method comprising: sending a side link SL measurement configuration associated with a user-to-user relay for the first wireless terminal and a second wireless terminal to a first wireless terminal, and receiving a measurement report associated with the SL measurement configuration from the first wireless terminal.

[0041] Various embodiments may preferably implement the following features:

[0042] Preferably, the SL measurement configuration comprises at least one of: at least one threshold used in a measurement reporting event, a filtering criterion for filtering measurement reports triggered by a measurement reporting event, or a measurement quantity associated with user-to-user relaying.

[0043] Preferably, the measurement report event includes at least one of the following: the link quality of the direct SL between the first wireless terminal and the second wireless terminal is lower than a first threshold; the link quality of the direct SL between the first wireless terminal and the second wireless terminal is lower than a second threshold, and the link quality of the first hop between the first user-to-user relay candidate and the first wireless terminal is greater than a third threshold; the link quality of the first hop between the second user-to-user relay candidate and the first wireless terminal is greater than a fourth threshold; the link quality of the first hop between the third user-to-user relay candidate and the first wireless terminal and the link quality of the second hop between the third user-to-user relay candidate and the second wireless terminal are greater than a fifth threshold; the link quality of the first hop and the second hop of the indirect SL is lower than a sixth threshold, wherein the first hop is between the first wireless terminal and a user-to-user relay serving the indirect SL for the first wireless terminal and the second wireless terminal, and the second hop is between the second wireless terminal and the user-to-user relay serving the indirect SL for the first wireless terminal and the second wireless terminal; or the link quality of the direct SL between the first wireless terminal and the second wireless terminal is greater than a seventh threshold.

[0044] Preferably, the filtering criteria include at least one of the following: an eighth threshold, which is configured to filter out the fourth user-to-user relay candidate if the link quality of the first hop between the fourth user-to-user relay candidate and the first wireless terminal is lower than the eighth threshold; or a ninth threshold, which is configured to filter out the fifth user-to-user relay candidate if the link quality of the second hop between the fifth user-to-user relay candidate and the second wireless terminal is lower than the ninth threshold.

[0045] Preferably, the SL measurement configuration is associated with an identifier ID of the second wireless terminal.

[0046] Preferably, the wireless communication method further comprises: sending a path switching configuration indicating a path switching toward an indirect SL to the first wireless terminal, the indirect SL being between the first wireless terminal and the second wireless terminal and being served by the third wireless terminal,

[0047] Preferably, the path switching configuration includes at least one of the following: an ID of the second wireless terminal, an ID of the third wireless terminal, or a timer value of a path switching timer used for path switching.

[0048] Preferably, the wireless communication method also includes: receiving information from the first wireless terminal, the information including at least one of the following: a path switching failure indication, a PC5 link establishment failure indication, an ID of the second wireless terminal, an indication of the first hop between the first wireless terminal and the third wireless terminal, or an indication of the second hop between the second wireless terminal and the third wireless terminal.

[0049] Preferably, the wireless communication method also includes: sending a SL configuration to the first wireless terminal, the SL configuration including at least one of: an indication of Packet Data Convergence Protocol PDCP data recovery for the SL between the first wireless terminal and the second wireless terminal, an indication of PDCP data recovery for each end-to-end SL data radio bearer DRB of the SL between the first wireless terminal and the second wireless terminal, an indication of PDCP reconstruction for the SL between the first wireless terminal and the second wireless terminal, or an indication of PDCP reconstruction for each end-to-end SL DRB of the SL between the first wireless terminal and the second wireless terminal.

[0050] Preferably, the wireless communication method further comprises: sending to the third wireless terminal an SL configuration associated with the user-to-user relay between the first wireless terminal and the second wireless terminal,

[0051] Preferably, the third wireless terminal is selected as a user-to-user relay for the first wireless terminal and the second wireless terminal based on the measurement report.

[0052] Preferably, the SL configuration includes at least one of the following: a user-to-user relay indication, an ID of the first wireless terminal, an ID of the second wireless terminal, a bearer mapping associated with an end-to-end SL radio bearer SLRB to a PC5 radio link control RLC channel of a first hop on an indirect SL, wherein the first hop is between a third wireless terminal and the first wireless terminal, and the indirect SL is between the first wireless terminal and the second wireless terminal and passes through the third wireless terminal, or a bearer mapping associated with an end-to-end SL SLRB to a PC5 RLC channel of a second hop on the indirect SL, wherein the second hop is between the third wireless terminal and the second wireless terminal, and the indirect SL is between the first wireless terminal and the second wireless terminal and passes through the third wireless terminal.

[0053] Preferably, the bearer mapping includes at least one of the following: end-to-end SLRB ID, PC5 RLC channel ID of the first hop, PC5 RLC channel ID of the second hop, ingress PC5 RLC channel ID, egress PC5 RLC channel ID, PC5 RLC channel ID between the first wireless terminal and the third wireless terminal, or PC5 RLC channel ID between the third wireless terminal and the second wireless terminal.

[0054] Preferably, the wireless communication method further comprises: sending SL relay assistance information associated with the third wireless terminal to the second wireless network node,

[0055] Preferably, the third wireless terminal is selected as a user-to-user relay for the first wireless terminal and the second wireless terminal based on the measurement report.

[0056] Preferably, the third wireless terminal is served by the second wireless network node.

[0057] Preferably, the SL relay assistance information includes at least one of the following: service cell information of the third wireless terminal, the ID of the third wireless terminal, the ID of the first wireless terminal, the ID of the second wireless terminal, bearer mapping between the SL signaling radio bearer SRB and the PC5 RLC channel, mapping between the SL data radio bearer DRB and at least one quality of service QoS flow, bearer mapping between the SL DRB and the PC5 RLC channel, a packet delay budget PDB associated with each PC5 RLC channel, a PDB associated with each SL DRB, a control plane indication for each PC5 RLC channel, or a channel configuration for each PC5 RLC channel.

[0058] Preferably, the wireless communication method further includes: receiving information of the second wireless terminal from the first wireless terminal.

[0059] Preferably, the information of the second wireless terminal includes at least one of the following: radio resource control status, serving cell information, or out-of-coverage indication.

[0060] The present disclosure relates to a wireless communication method used in a second wireless network node, the method comprising: receiving side link SL relay assistance information associated with a third wireless terminal selected as a user-to-user relay for a first wireless terminal and a second wireless terminal from a first wireless network node, and sending an SL configuration associated with the user-to-user relay between the first wireless terminal and the second wireless terminal to the third wireless terminal.

[0061] Various embodiments may preferably implement the following features:

[0062] Preferably, the SL relay assistance information includes at least one of the following: service cell information of the third wireless terminal, an identifier ID of the third wireless terminal, an ID of the first wireless terminal, an ID of the second wireless terminal, a bearer mapping between the SL signaling radio bearer SRB and the PC5 RLC channel, a mapping between the SL data radio bearer DRB and at least one quality of service QoS flow, a bearer mapping between the SL DRB and the PC5 RLC channel, a packet delay budget PDB associated with each PC5 RLC channel, a PDB associated with each SL DRB, a control plane indication for each PC5 RLC channel, or a channel configuration for each PC5 RLC channel.

[0063] Preferably, the SL configuration includes at least one of the following: a user-to-user relay indication, an ID of the first wireless terminal, an ID of the second wireless terminal, a bearer mapping associated with an end-to-end SL radio bearer SLRB to a PC5 radio link control RLC channel of a first hop on an indirect SL, wherein the first hop is between a third wireless terminal and the first wireless terminal, and the indirect SL is between the first wireless terminal and the second wireless terminal and passes through the third wireless terminal, or a bearer mapping associated with an end-to-end SL SLRB to a PC5 RLC channel of a second hop on the indirect SL, wherein the second hop is between the third wireless terminal and the second wireless terminal, and the indirect SL is between the first wireless terminal and the second wireless terminal and passes through the third wireless terminal.

[0064] Preferably, the bearer mapping includes at least one of the following: end-to-end SLRB ID, PC5 RLC channel ID of the first hop, PC5 RLC channel ID of the second hop, ingress PC5 RLC channel ID, egress PC5 RLC channel ID, PC5 RLC channel ID between the first wireless terminal and the third wireless terminal, or PC5 RLC channel ID between the third wireless terminal and the second wireless terminal.

[0065] The present disclosure relates to a first wireless terminal, the first wireless terminal comprising:

[0066] A communication unit is configured to receive a side link SL measurement configuration associated with a user-to-user relay for a first wireless terminal and a second wireless terminal from a first wireless network node, and send a measurement report to the first wireless network node based on the measurement configuration.

[0067] Various embodiments may preferably implement the following features:

[0068] Preferably, the first wireless terminal further includes: a processor, wherein the processor is configured to execute any one of the aforementioned wireless communication methods.

[0069] The present disclosure relates to a third wireless terminal, the third wireless terminal comprising:

[0070] a communication unit configured to receive, from a radio network node serving a third wireless terminal, a side link SL configuration associated with a user-to-user relay between the first wireless terminal and the second wireless terminal, and

[0071] A processor is configured to establish a first PC5 link with the first wireless terminal and establish a second PC5 link with the second wireless terminal based on the SL configuration.

[0072] Various embodiments may preferably implement the following features:

[0073] Preferably, the processor is further configured to execute any one of the aforementioned wireless communication methods.

[0074] The present disclosure relates to a first radio network node, the first radio network node comprising:

[0075] A communication unit configured to send a sidelink SL measurement configuration associated with a user-to-user relay for the first wireless terminal and a second wireless terminal to a first wireless terminal, and receive a measurement report associated with the SL measurement configuration from the first wireless terminal.

[0076] Various embodiments may preferably implement the following features:

[0077] Preferably, the first radio network node further comprises: a processor, wherein the processor is configured to perform operations according to any one of the aforementioned wireless communication methods.

[0078] The present disclosure relates to a second radio network node, the second radio network node comprising:

[0079] A communication unit, the communication unit being configured to: receive side link SL relay assistance information associated with a third wireless terminal selected as a user-to-user relay for a first wireless terminal and a second wireless terminal from a first wireless network node, and send an SL configuration associated with the user-to-user relay between the first wireless terminal and the second wireless terminal to the third wireless terminal.

[0080] Various embodiments may preferably implement the following features:

[0081] Preferably, the second radio network node further includes: a processor, wherein the processor is configured to execute any one of the aforementioned wireless communication methods.

[0082] The present disclosure relates to a computer program product, which includes a computer-readable program medium code stored thereon. When the code is executed by a processor, the processor is caused to implement any one of the wireless communication methods described above.

[0083] The exemplary embodiments disclosed herein are intended to provide features that will become apparent by reference to the following description when taken in conjunction with the accompanying drawings. According to various embodiments, exemplary systems, methods, devices, and computer program products are disclosed herein. However, it should be understood that these embodiments are presented by way of example and not limitation, and it will be apparent to those of ordinary skill in the art who have read this disclosure that various modifications may be made to the disclosed embodiments while remaining within the scope of this disclosure.

[0084] Therefore, the present disclosure is not limited to the exemplary embodiments and applications described and illustrated herein. In addition, the specific order and / or hierarchy of steps in the methods disclosed herein are merely exemplary approaches. Based on design preferences, the specific order or hierarchy of steps of the disclosed methods or processes can be rearranged while remaining within the scope of the present disclosure. Therefore, it will be understood by those of ordinary skill in the art that the methods and techniques disclosed herein present various steps or actions in a sample order, and unless otherwise expressly provided, the present disclosure is not limited to the specific order or hierarchy presented.

[0085] The above and other aspects and their embodiments are described in more detail in the drawings, the description and the claims.

[0086] Figure 1 A schematic diagram showing a scenario of sidelink relay communication.

[0087] Figure 2A and Figure 2B A schematic diagram of a direct side link and an indirect side link according to an embodiment of the present disclosure is shown.

[0088] Figure 3A schematic diagram of a signaling process according to an embodiment of the present disclosure is shown.

[0089] Figure 4 A schematic diagram of SL measurement configuration and reporting according to an embodiment of the present disclosure is shown.

[0090] Figure 5 FIG. 4 is a schematic diagram showing a path switching from an indirect SL to a direct SL according to an embodiment of the present disclosure.

[0091] Figure 6 FIG. 4 is a schematic diagram showing a path switching from an indirect SL to another indirect SL according to an embodiment of the present disclosure.

[0092] Figure 7 An example of a schematic diagram of a wireless terminal according to an embodiment of the present disclosure is shown.

[0093] Figure 8 An example of a schematic diagram of a wireless network node according to an embodiment of the present disclosure is shown.

[0094] Figures 9 to 12 is a flowchart of a method according to an embodiment of the present disclosure.

[0095] In the present disclosure, at least one of X, Y and Z may represent at least one X and / or at least one Y and / or at least one Z, wherein each of X, Y and Z may be a condition, a criterion, a threshold value, a measurement quantity, etc.

[0096] Figure 2A and Figure 2B FIG. 1 shows a schematic diagram of path switching according to an embodiment of the present disclosure. Figure 2A In the example, the (communication) path between the source UE (e.g., UE1) and the target UE (e.g., UE2) can be switched from direct SL (i.e., the two UEs communicate directly with each other) to indirect SL (i.e., the two UEs communicate with each other via a U2U relay UE), and vice versa. Figure 2A As shown, in the present disclosure, the link / path between UE1 and the U2U relay UE is referred to as the first hop (of the indirect SL). In addition, in the present disclosure, the link / path between UE2 and the U2U relay UE is referred to as the second hop (of the indirect SL).

[0097] In the present disclosure, the first hop may be equivalent to the first PC5 hop.

[0098] In the present disclosure, the second hop may be equivalent to the second PC5 hop.

[0099] In the present disclosure, a PC5 link may be equivalent to a PC5 unicast link or a unicast link.

[0100] Based on the direction of data transmission, the links between UE1 and the U2U relay UE and between UE2 and the U2U relay UE may be called different names. Figure 2B In the embodiment shown in the upper part (a), data is sent from UE1 to UE2. That is, in this embodiment, UE1 is the source UE, and UE2 is the target UE. In this embodiment, for the U2U relay UE, the link between UE1 and the U2U relay UE is called an ingress link, and the link between UE2 and the U2U relay UE is called an egress link. Figure 2B In the embodiment shown in the lower part (b), data is sent from UE2 to UE1. In this embodiment, for the U2U relay UE, the link between UE1 (i.e., the target UE) and the U2U relay UE is called an egress link, and the link between UE2 (the source UE) and the U2U relay UE is called an ingress link. Generally, for a UE, an egress link is an outbound link (i.e., data is sent to the outbound link), and an ingress link is an inbound link (i.e., data is received from the inbound link).

[0101] Notice, Figure 2A and Figure 2B UE1 and UE2 in the figure represent random UEs and can be used with Figure 1 Different from those shown.

[0102] In particular, during the path switching from a direct link to an indirect link, the PC5 link between the source UE and the target UE can remain unchanged. The E2E (end-to-end) PC5SDAP / PDCP (Service Data Adaptation Protocol / Packet Data Convergence Protocol) and RRC (Radio Resource Control) terminated at the source UE and the target UE can also remain unchanged. When the path is switched from a direct SL to an indirect SL, the direct PC5 RLC bearer (e.g., the PC5 RLC bearer / PC5 RLC channel at the direct SL) is released, and data transmission is transferred to the PC5 RLC bearer of the indirect SL. Service continuity is ensured by PDCP data recovery or PDCP reconstruction. In the present disclosure, the PC5 RLC bearer can be equivalent to the PC5 RLC channel.

[0103] Figure 3 FIG. 1 is a schematic diagram showing a signaling process according to an embodiment of the present disclosure. Figure 3In the embodiment of the present invention, the source UE and the target UE communicate with each other via a direct SL (step 300). If the link quality of the direct SL (i.e., the direct PC5 link) deteriorates, the source UE can find a U2U relay UE (the relay UE can reach both the source UE and the target UE) to forward the SL service between the source UE and the target UE (step 301). If multiple candidate relay UEs are found, the source UE can autonomously select (or based on some (pre-) configured criteria) the relay UE (step 302). Next, the source UE can establish a PC5 link with the selected U2U relay UE, which can trigger the relay UE to establish a PC5 link with the target UE (steps 304 and 305). In steps 304 and 305, QoS (quality of service) splitting can be performed by the relay UE and the source side PC5 QoS is sent to the source UE. After completing the PC5 link establishment on each hop (i.e., the first hop and the second hop), a PC5 RLC bearer for sending E2E SL DRBs (data radio bearers) on each hop can be established. The SL data transmission between the source UE and the target UE is transferred to the indirect SL forwarded by the relay UE (step 306). After or simultaneously with steps 304, 305 and 306, the source UE may initiate an E2E PC5 RRC reconfiguration forwarded by the relay UE to release the direct PC5 RLC bearer on the direct SL (step 307).

[0104] In some embodiments, path switching from direct SL to indirect SL may include SL measurement configuration and reporting over the Uu interface.

[0105] Figure 4 FIG. 1 is a schematic diagram showing a SL measurement configuration and report according to an embodiment of the present disclosure. Figure 4 In the embodiment, if the source UE is in an RRC connected state, the source UE may receive a SL measurement configuration for U2U relay measurement from its serving gNB (i.e., gNB1), and the source UE may report the result of the relay measurement to the serving gNB (steps 401 and 402). Based on the measurement report, gNB1 may select a (U2U) relay UE for the source UE, and notify the source UE of the selected relay UE (e.g., the L2 ID (Layer 2 Identifier) ​​of the relay UE). The SL measurement configuration may include (one or more) thresholds and / or measurement quantities associated with (one or more) SL measurement reporting events and / or one or more filtering criteria for the SL measurement report.

[0106] In an embodiment, the SL measurement configuration may be configured for each destination / target UE.

[0107] In an embodiment, the SL measurement report event(s) may be / include at least one of the following events:

[0108] 1) The link quality of the direct SL (link quality between the source UE and the target UE, SL-RSRP (SL reference signal received power) or SD-RSRP (SL discovery reference signal received power)) is lower than the threshold TH1.

[0109] In this event, SL-RSRP may be measured as the measurement quantity.

[0110] In this event, SD-RSRP may be measured (only) if SL-RSRP is not available.

[0111] 2) The link quality of the direct SL is lower than a threshold TH2, and the link quality of the first (PC5) hop of the candidate indirect SL (link quality, SD-RSRP or SL-RSRP between the source UE and the candidate relay UE) is greater than a threshold TH3.

[0112] In event (2), SD-RSRP may be measured as the link quality of the candidate indirect SL.

[0113] In event (2), if SL-RSRP is available, SL-RSRP is used as the link quality.

[0114] 3) The link quality of the first hop of the candidate indirect SL is greater than the threshold TH4.

[0115] 4) The link quality of the second hop of the candidate indirect SL is greater than the threshold TH5.

[0116] 5) The link qualities of the first hop and the second hop of the candidate indirect SL are both greater than the threshold TH6.

[0117] 6) Any combination of the above events (1) to (5).

[0118] In an embodiment, the link quality in events (1) to (6) may be SL-RSRP or SD-RSRP. In addition, the threshold may be a threshold for SL-RSRP or SD-RSRP.

[0119] In an embodiment, in a combination of two or more of the above events (1) to (5), the thresholds used in the combined events may be the same or different.

[0120] In an embodiment, the filtering criteria is / includes threshold(s) that filters out (eg, removes) U2U relay candidates having a link quality less than / below a threshold.

[0121] For example, the one or more filtering criteria for the SL measurement report may include at least one of the following:

[0122] 1) A threshold TH7 associated with filtering out a candidate indirect SL if the link quality of the second hop of the candidate indirect SL is lower than the threshold TH7.

[0123] 2) A threshold TH8 associated with filtering out a candidate indirect SL if the link quality of the first hop of the candidate indirect SL is lower than the threshold TH8.

[0124] 3) Maximum number of candidate relay UEs.

[0125] 4) A priority threshold associated with filtering out a candidate indirect SL if the priority or weight of a measurement reporting event associated with (reporting) the candidate indirect SL is lower than the priority threshold.

[0126] In an embodiment, if any measurement reporting event is met / occurred, the (one or more) measurement reporting events that occur may trigger the source UE to report the corresponding SL measurement results. The SL measurement results may be reported for each destination / target UE. In addition, the source UE may filter the measurement results for reporting according to one or more filtering criteria (if configured). In particular, the SL measurement report may include at least one of the following: destination / target UE ID, link quality of the direct SL with the destination / target UE, candidate relay UE ID (e.g., L2 ID, C-RNTI, local ID of the candidate relay UE), serving cell of the candidate relay UE (e.g., NCGI, NCI, PCI), link quality of the first hop of the candidate relay UE (link quality between the source UE and the candidate relay UE), or link quality of the second hop of the candidate relay UE (link quality between the candidate relay UE and the target UE). In an embodiment, the source UE may obtain / receive the link quality of the second hop of the candidate relay UE from the discovery message sent by the candidate relay UE.

[0127] In some embodiments, the path switch from direct SL to indirect SL may include configuration from the gNB to the source UE.

[0128] In an embodiment, after receiving the measurement report from the source UE, gNB1 may select a relay UE for the source UE and send a path switch configuration to the source UE. In particular, the path switch configuration may include at least one of the following: a destination / target UE ID, an ID of the selected relay UE (e.g., an L2 ID of the relay UE), or a timer value for a path switch timer used in the path switch. In an embodiment, the source UE starts the path switch timer upon / after receiving the path switch configuration from gNB1. In an embodiment, the source UE may stop the path switch timer in at least one of the following cases:

[0129] 1) When the PC5 links between the source UE and the relay UE and between the relay UE and the target UE are successfully established.

[0130] For example, when a direct communication response is received from the relay UE, wherein after the relay UE receives the direct communication response from the target UE, the relay UE sends a direct communication response message to the source UE.

[0131] 2) Successfully send the RRCReconfigurationSidelink message to the relay UE.

[0132] For example: when a PC5 RLC response is received from the relay UE.

[0133] 3) RRCReconfigurationCompleteSidelink is successfully received from the relay UE.

[0134] 4) E2ERRCReconfigurationSidelink / RRCReconfigurationCompleteSidelink is successfully sent or received to / from the relay UE.

[0135] 5) Receive a PDCP response from the target UE.

[0136] 6) An E2E direct communication response forwarded by the relay UE is received from the target UE.

[0137] 7) Successfully sending / receiving an E2E L2 Link Modification Request / L2 Link Modification Accept message to / from the relay UE.

[0138] When the path switch timer expires, the source UE may initiate relay reselection or report the path switch failure to gNB1. In an embodiment, the source UE may reuse the SL configuration failure as a path switch failure. In addition, the SL configuration from gNB1 to the source UE may also include an indication to release the direct PC5 RLC bearer of the target UE.

[0139] Upon receiving the path switching configuration from the gNB, the source UE may initiate a PC5 link establishment with the selected relay UE, which may further trigger another PC5 link establishment between the selected relay UE and the target UE.

[0140] In an embodiment, the PC5 link establishment between the source UE and the relay UE may fail. In this embodiment, the source UE may report the path switching failure or PC5 link establishment failure to the gNB immediately or after the path switching timer expires (i.e., when the path switching timer expires). In an embodiment, the report information for the path switching failure or PC5 link establishment failure may include / indicate at least one of the following: path switching failure (indication), PC5 link establishment failure (indication), target UE ID, first hop indication, or second hop indication. For example, the target UE ID may be used to indicate that the path switching failure or PC5 link establishment failure occurs between the source UE and the indicated UE (i.e., the target UE). The first hop indication is configured to indicate that the path switching failure or PC5 link establishment failure occurs between the first hop (between the source UE and the U2U relay UE). The second hop indication is configured to indicate that the path switching failure or PC5 link establishment failure occurs between the second hop (between the target UE and the U2U relay UE).

[0141] In an embodiment, the PC5 link establishment between the relay UE and the target UE may fail. Under such conditions, the relay UE may notify the source UE of the PC5 link establishment failure with the target UE. For example, the information for the failure may include the target UE ID and / or the PC5 link establishment failure indication. Upon receiving the information from the relay UE, the source UE may report the failure between the relay UE and the target UE to the gNB1 immediately or after the path switching timer expires. For example, the report information may include at least one of the following: target UE ID, relay UE ID, PC5 link establishment failure indication, or second hop indication.

[0142] In some embodiments, path switching from direct SL to indirect SL may involve configuration from the gNB to the selected relay UE.

[0143] In an embodiment, the selected relay UE is in an RRC connected state under the same gNB as the source UE (i.e., gNB1). After selecting the relay UE, gNB1 may send SL-related configurations to the relay UE. In particular, the SL-related configurations may include at least one of the following: U2U relay indication, ID of the source-destination UE pairing (e.g., L2 ID of the source UE, L2 ID of the target UE), PC5 RLC bearer configuration between the source UE and the relay UE, PC5 RLC bearer configuration between the relay UE and the target UE, or bearer mapping configuration between the E2E SLRB to the first-hop and second-hop PC5 RLC bearers on the indirect SL. In an embodiment, the bearer mapping configuration may include at least one of the following: E2E SLRB ID, first-hop PC5 RLC channel ID, second-hop PC5 RLC channel ID, ingress PC5 RLC channel ID, egress PC5 RLC channel ID, PC5 RLC channel ID between the source UE and the relay UE, or PC5 RLC channel ID between the relay UE and the target UE.

[0144] In an embodiment, a SL measurement configuration may be configured to a relay UE. Based on the SL measurement configuration, the relay UE measures both the PC5 link quality of the first hop and the second hop, and reports the SL measurement results. In particular, the SL measurement report may include at least one of the following: a peer UE ID (e.g., the L2 ID of the source UE or the L2 ID of the target UE), or a PC5 link quality between the peer UE and the relay UE.

[0145] In some embodiments, the path switch from direct SL to indirect SL may include coordination between the gNBs of the source UE, relay UE, and target UE.

[0146] In an embodiment, the relay UE is in an RRC connected state under a gNB (e.g., gNB2) different from the source UE's gNB1. In this embodiment, gNB1 may send SL relay assistance information to gNB2 to allow gNB2 to configure the relay UE (once or more). The SL relay assistance information may include at least one of the following: service cell information of the relay UE, relay UE identity (L2 ID of the relay UE), L2 ID of the source UE, L2 ID of the target UE, SL SRB to PC5 RLC channel mapping (e.g., each SL SRB ID is mapped to a PC5 RLC channel ID), SL DRB to QoS flow mapping (e.g., for each SL DRB ID, a QFI mapped to the SL DRB and a QoS profile for each QFI), SL DRB to PC5 RLC channel mapping (e.g., each SLSRB ID is mapped to a PC5 RLC channel ID), PDB associated with the PC5 RLC channel, PDB associated with the SL DRB, control plane indication of the PC5RLC channel (e.g., indicating that the PC5 RLC channel is used to send control plane services or to send a specific SLSRB ID), or PC5 RLC channel configuration (e.g., for each PC5 RLC channel ID, RLC and logical channel configuration). SL relay assistance information can be sent via non-UE associated Xn messages, such as Xn establishment request, NG-RAN node configuration update, mobility change request, access and mobility indication message, and (one or more) other newly defined Xn messages.

[0147] In an embodiment, if gNB2 allows the relay UE to act as a relay for source-target UE pairing upon / after receiving SL relay assistance information from gNB1, gNB2 may send a response message to gNB1. The response message may include at least one of the following: a relay UE ID, or an L2 ID of the associated source UE and target UE. In this embodiment, gNB2 may send a configuration to the relay UE, wherein the configuration may include at least one of the following: an L2 ID of the source UE and target UE pairing, a mapping of SL DRBs and PC5 RLC channels between the source UE and the relay UE, a mapping of SL DRBs and PC5 RLC channels between the relay UE and the target UE, or a PC5 RLC channel configuration.

[0148] In an embodiment, if gNB1 intends to select a relay UE for pairing the source UE and the target UE after receiving a measurement report from the source UE, gNB1 may need to know whether / how it can communicate with the gNB of the target UE (e.g., gNB3), and coordinate with gNB3 to select the relay UE (or notify gNB3 of the selected relay UE). In this embodiment, the source UE may need to know the target UE information, such as the RRC state of the target UE and / or the serving cell information and / or the out-of-coverage indication of the target UE, and report the target UE information to gNB1. The source UE may report the target UE information to gNB1 in the SL measurement report or the SL UE information. In an embodiment, the source UE may obtain the target UE information from the discovery message(s) of the target UE or the discovery message(s) of the relay UE.

[0149] In an embodiment, if the target UE is in an RRC connected state, gNB1 may send SL related information to gNB3 based on the SL measurement report from the source UE and the target UE information. The SL related information may include at least one of the following: L2 ID of the source UE, L2 ID of the target UE, a list of candidate relay UEs, selected relay UEs, RRC state of each candidate / selected relay UE, PC5 link quality between the source UE and each candidate relay UE, or PC5 link quality between each candidate relay UE and the target UE. gNB3 may respond to gNB1 with the relay UE selected for the source-target UE pairing.

[0150] In some embodiments, service continuity may need to be considered during path switching from direct SL to indirect SL.

[0151] In an embodiment, the logical channel ID (LCID) of each E2E SL DRB at the direct SL (e.g., the LSB5 bits of the LCID) may be continuously used as the SL security input in the indirect SL. If the SL security input is not changed / reconfigured, PDCP data recovery may be performed. If SL security is changed / reconfigured (e.g., a fictitious bearer ID / LCID for each E2E SL DRB is included in the E2E PC5 RRC reconfiguration or a fictitious bearer ID / LCID is included in the adaptation layer header or the PDCP header), PDCP reestablishment may be performed. During PDCP data recovery or PDCP reestablishment, data transmission through the direct SL / E2E SL DRB is performed via the indirect SL to send data at each hop via the use of the PC5 RLC bearer.

[0152] In an embodiment, the source UE may indicate PDCP data resumption or PDCP re-establishment to the target UE via an E2E PC5 RRC reconfiguration / message. In another embodiment, the source UE may receive a PDCP data resumption indication or a PDCP re-establishment indication from the target UE via an E2E PC5 RRC message. In yet another embodiment, the sidelink configuration from the gNB to the source UE may include at least one of: an indication of PDCP data resumption for SL (per UE), an indication of PDCP data resumption for E2E SL DRB (per SL DRB), an indication of PDCP re-establishment for SL, or an indication of PDCP re-establishment for E2E SL DRB. When the path switches from direct SL to indirect SL, the source UE may perform PDCP data resumption or PDCP re-establishment by default. That is, the source UE may resend packets (PDCP SDU / PDU) on the indirect SL that have not been confirmed to be successfully delivered by a layer lower than the PDCP layer of the direct SL.

[0153] In an example, the SL path between two UEs may be switched from indirect SL to direct SL.

[0154] In some embodiments, a source UE (e.g., UE1) communicates with a target UE (e.g., UE2) via a U2U relay UE. If UE1 / UE2 detects that the PC5 link quality between UE1 / UE2 and the relay UE has deteriorated, UE1 and / or UE2 may initiate relay reselection / path switching. In an embodiment, UE1 may be interested in the link quality of the second hop. Under such conditions, the source UE may configure the relay UE to measure the PC5 link quality of the second hop and report the measurement results to obtain the link quality of the second hop. In these embodiments, the measurement mechanism / signaling may need to indicate the destination / target UE ID to be measured and / or the destination / target UE ID of the measurement results.

[0155] In some embodiments of a path switch from an indirect SL to a direct SL, if the source UE is in an RRC connected state, the source UE may receive a SL measurement configuration for (one or more) U2U relay measurements from its serving gNB, and report the results of (one or more) U2U relay measurements to gNB1 (i.e., the gNB serving the source UE). Based on the measurement report, gNB1 may determine to instruct the source UE to switch the path to direct SL. The SL measurement configuration may include (one or more) thresholds and / or measurement quantities associated with (one or more) SL measurement reporting events and / or one or more filtering criteria for SL measurement reports.

[0156] In an embodiment, the SL measurement reporting event(s) may include at least one of the following:

[0157] 1) The link quality of the first hop of the serving indirect SL (eg, the link quality, SL-RSRP or SD-RSRP between the source UE and the current serving relay UE) is lower than a threshold TH9.

[0158] Note that SL-RSRP may be measured as a measurement quantity. In an embodiment, SD-RSRP may be measured as a measurement quantity (only) if SL-RSRP is not available.

[0159] 2) The link quality of the direct SL is greater than the threshold TH10.

[0160] 3) The link quality of the first hop serving the indirect SL is lower than a threshold TH11, and the link quality of the direct SL is greater than a threshold TH12, where the threshold TH11 and the threshold TH12 may be the same or different.

[0161] 4) The link quality of the first hop of the service indirect SL is lower than the threshold TH13, and the link quality of the second hop of the service indirect SL (for example, the link quality between the current service relay UE1 and the target UE) is lower than the threshold TH14, where the threshold TH13 and the threshold TH14 can be the same or different.

[0162] 5) The link quality of the first hop of the indirect service SL is lower than the threshold TH15, the link quality of the second hop of the indirect service SL is lower than the threshold TH16, and the link quality of the direct SL is greater than the threshold TH17, where the threshold TH15, the threshold TH16 and the threshold TH17 can be the same or different.

[0163] 6) Any combination of the above events to generate new events.

[0164] In an embodiment, SL-RSRP is measured as the measurement quantity in (one or more) SL measurement reporting events. In an embodiment, SD-RSRP is measured as the measurement quantity in (one or more) SL measurement reporting events only if SL-RSRP is not available.

[0165] In embodiments where two or more SL measurement reporting events are combined (eg, when a source UE communicates with a target UE via a U2U relay), the thresholds used in the SL measurement reporting events may be the same or different.

[0166] In an embodiment, after receiving the SL measurement report from the source UE, the gNB may instruct the source UE to perform a path switch to the direct SL. For example, the gNB may send a configuration to the source UE, wherein the configuration may include at least one of the following: an indication of a path switch to the direct SL, a direct PC5 RLC bearer associated with the E2E SL DRB, or a timer value of a path switch timer.

[0167] In an embodiment, the UE starts the path switch timer when receiving a configuration indicating a path switch from gNB1. The stop condition of the path switch timer may be at least one of the following:

[0168] 1) A L2 Link / ID Modification Request message is successfully sent to the target UE in direct SL (eg, a PC5 RLC Acknowledge is received from the target UE).

[0169] 2) Successfully receive the L2 Link / ID Modification Accept message from the target UE.

[0170] When the path switch timer expires, the UE may report a path switch failure (or a SL RLF indication or a SL configuration failure indication) to the network and / or initiate relay reselection.

[0171] In an embodiment, upon receiving the gNB configuration, the source UE may initiate a PC5 RRC reconfiguration with the target UE (specified SL-SRB3, timer 400) to establish a direct PC5 RLC bearer for the SL DRB.

[0172] Figure 5 FIG. 4 is a schematic diagram showing a path switching from an indirect SL to a direct SL according to an embodiment of the present disclosure.

[0173] In step 500, the source UE and the target UE communicate via a U2U relay UE (ie, indirect SL).

[0174] In step 501, if UE1 / UE2 detects that the PC5 link quality between UE1 / UE2 and the relay UE deteriorates, the source UE and / or the target UE may initiate relay reselection / path switching to switch from the indirect SL to the direct SL. Alternatively, the source UE may receive a path switching indication for the path switching from the indirect SL to the direct SL from the serving gNB.

[0175] In step 502, the source UE performs direct PC5 RRC reconfiguration with the target UE to configure a direct PC5 RLC channel for the SL DRB.

[0176] In step 503, the source UE and the U2U relay UE perform PC5 RRC reconfiguration to release the related PC5 RLC channel or bearer mapping on the first hop.

[0177] In step 503, the source UE and the U2U relay UE perform PC5 RRC reconfiguration to release the related PC5 RLC channel or bearer mapping on the first hop.

[0178] In step 504, the target UE and the U2U relay UE perform PC5 RRC reconfiguration to release the relevant PC5 RLC channel or bearer mapping on the second hop.

[0179] In step 505, the source UE communicates with the target UE via direct SL.

[0180] In an example, the SL path between two UEs may be switched from an indirect SL (eg, SL1) to another indirect SL (eg, SL2).

[0181] In some embodiments, during the path switch, the extended PC5 link between the source UE and the target UE may remain unchanged. The E2E PC5 SDAP / PDCP and RRC terminated at the source UE and the target UE may also remain unchanged. When the path is switched from the indirect SL1 to the indirect SL2, the first hop PC5 RLC bearer and the second hop PC5 RLC bearer on the indirect SL1 are released, and the data transmission is transferred to the PC5 RLC bearer of the indirect SL2.

[0182] Figure 6 FIG. 4 is a schematic diagram showing a path switching from an indirect SL to another indirect SL according to an embodiment of the present disclosure.

[0183] In steps 600 and 601, the source UE communicates with the target UE via the U2U relay UE 3. If the source UE / target UE detects that the link quality of PC5 toward the relay UE 3 deteriorates, the source UE / target UE may find other candidate relay UEs. If multiple candidate relay UEs are found, the source UE / target UE may select a candidate relay UE (e.g., relay UE 4).

[0184] If the source UE / target UE is in RRC connected state, it may receive SL measurement configuration for U2U relay measurement from its serving gNB and report the result of relay measurement to the gNB. The SL measurement configuration may include thresholds and / or measurement quantities related to SL measurement reporting events and / or filtering criteria for SL measurement reporting. The SL measurement reporting event may be at least one of the following:

[0185] 1) The link quality of the first hop of the indirect SL (the source UE and the current serving relay UE (i.e. Figure 6 The link quality, SL-RSRP or SD-RSRP) between the relay UE3) in the relay is lower than the threshold TH18.

[0186] In an embodiment, as a baseline, SL-RSRP is measured as the measurement quantity.

[0187] In an embodiment, SD-RSRP is measured as the measurement quantity (only) if SL-RSRP is not available.

[0188] 2) Link quality of the first hop of the candidate indirect SL (source UE and candidate relay UE (e.g. Figure 6 The link quality, SD-RSRP or SL-RSRP) between the relay UE4) in the relay is greater than the threshold TH19.

[0189] 3) The link quality of the first hop of the serving indirect SL is lower than a threshold TH20, and the link quality of the first hop of the candidate indirect SL is greater than a threshold TH21, where the threshold TH20 and the threshold TH21 may be the same or different.

[0190] 4) The link quality of the first hop of the service indirect SL and the link quality of the second hop of the service indirect SL are lower than a threshold TH22.

[0191] 5) The link quality of the first hop of the candidate indirect SL and the link quality of the second hop of the candidate indirect SL are greater than a threshold value TH23.

[0192] 6) The link quality of the first hop of the serving indirect SL and the link quality of the second hop of the serving indirect SL are lower than a threshold TH24, and the link quality of the first hop of the candidate indirect SL and the link quality of the second hop of the candidate indirect SL are greater than a threshold TH25, where threshold TH24 and threshold TH25 may be the same or different.

[0193] 7) The link quality of the second hop of the service indirect SL (the link quality between the current service relay UE3 and the target UE) is lower than the threshold TH26.

[0194] 8) The link quality of the second hop of the candidate indirect SL is greater than the threshold TH27.

[0195] 9) Any combination of the above events to generate new events.

[0196] In embodiments where two or more SL measurement reporting events are combined (eg, when a source UE communicates with a target UE via a U2U relay), the thresholds used in the SL measurement reporting events may be the same or different.

[0197] In an embodiment, the filtering criteria is / includes threshold(s) that filters out (eg, removes) U2U relay candidates having a link quality less than / below a threshold.

[0198] For example, the one or more filtering criteria for the SL measurement report may include at least one of the following:

[0199] 1) A threshold TH28 associated with filtering out a candidate indirect SL if the link quality of the second hop of the candidate indirect SL is lower than the threshold TH28.

[0200] 2) A threshold value TH29 associated with filtering out a candidate indirect SL if the link quality of the first hop of the candidate indirect SL is lower than a threshold value TH27.

[0201] 3) Maximum number of candidate relay UEs.

[0202] 4) A priority threshold associated with filtering out a candidate indirect SL if the priority or weight of a measurement reporting event associated with (reporting) the candidate indirect SL is lower than the priority threshold.

[0203] Based on the measurement report, the gNB1 of the source UE may select a relay UE for the source UE and notify the source UE of the selected relay UE (e.g., the L2 ID of relay UE4). That is, gNB1 may send a path switching configuration to the source UE. The path switching configuration may refer to the path switching configuration discussed above and will not be discussed here for the sake of brevity.

[0204] In an embodiment, if the selected relay UE is under the same gNB1 as the source UE and is in an RRC connected state, gNB1 may send SL-related configurations to the selected relay UE4 for preparation of path switching. The path switching configuration may refer to the aforementioned SL-related configurations and will not be discussed here for the sake of brevity.

[0205] In steps 602 and 603, the source UE and the target UE respectively establish PC5 links with the selected target relay UE 4. PC5 RRC reconfiguration is performed between the source UE and the relay UE 4 and between the relay UE 4 and the target UE to configure the PC5 RLC channel for the E2E SL DRB on each hop (i.e., the first hop between the source UE and the relay UE 4 and the second hop between the target UE and the relay UE 4).

[0206] In step 604, E2E PC5 RRC reconfiguration may be performed between the source UE and the target UE to reconfigure the E2ESL DRB (eg, configure a fictitious LCID for SL security input, add / modify / release E2E SL DRB, etc.).

[0207] In step 605, the source UE may release the bearer mapping between the E2E SL DRB and the first hop PC5 RLC channel (between the source UE and the relay UE3). If there is no relay service mapped to the PC5 RLC channel (between the source UE and the relay UE3), the PC5 RRC reconfiguration may be performed to release the PC5 RLC channel. If there is no relay service between the source UE and the relay UE3, the PC5 link may be released. The relay UE3 may release the bearer mapping of the E2E SL DRB / first hop PC5 RLC channel / entry PC5 RLC channel and the second hop PC5 RLC channel / egress PC5 RLC channel (between the relay UE3 and the target UE). If there is no relay service mapped to the PC5 RLC channel (between the relay UE3 and the target UE), the PC5 RRC reconfiguration may be performed to release the PC5 RLC channel. If there is no relay service between the relay UE3 and the target UE, the PC5 link may be released.

[0208] In step 606, the data is transferred from the source relay link to the target relay link. Note that PDCP data resumption or PDCP re-establishment may be performed based on an indication (e.g., from the serving gNB or from a peer UE).

[0209] Figure 7 A schematic diagram of a wireless terminal 70 according to an embodiment of the present disclosure is provided. The wireless terminal 70 may be a user equipment (UE), a mobile phone, a laptop computer, a tablet computer, an e-book, or a portable computer system, and is not limited thereto. The wireless terminal 70 may include a processor 700 (such as a microprocessor or an application specific integrated circuit (ASIC)), a storage unit 710, and a communication unit 720. The storage unit 710 may be any data storage device that stores a program code 712 accessed and executed by the processor 200. Embodiments of the storage unit 712 include, but are not limited to, a subscriber identity module (SIM), a read-only memory (ROM), a flash memory, a random-access memory (RAM), a hard disk, and an optical data storage device. The communication unit 720 may be a transceiver, and is used to send and receive signals (e.g., messages or packets) according to the processing results of the processor 700. In an embodiment, the communication unit 720 communicates with the communication unit 720 via Figure 7 At least one antenna 722 is shown for transmitting and receiving signals.

[0210] In an embodiment, the storage unit 710 and the program code 712 may be omitted, and the processor 700 may include a storage unit having stored program code.

[0211] The processor 700 may implement any of the steps of the exemplary embodiments on the wireless terminal 70 , for example, by executing the program code 712 .

[0212] The communication unit 720 may be a transceiver. Alternatively or additionally, the communication unit 720 may combine a transmitting unit and a receiving unit, both of which are respectively configured to send signals to and receive signals from a wireless network node (eg, a base station).

[0213] Figure 8 A schematic diagram of a radio network node 80 according to an embodiment of the present disclosure is provided. The radio network node 80 may be a satellite, a base station (BS), a network entity, a mobility management entity (MME), a serving gateway (S-GW), a packet data network (PDN) gateway (P-GW), a radio access network (RAN) node, a next generation RAN (NG-RAN) node, a gNB, an eNB, a gNB central unit (gNB-CU), a gNB distributed unit (gNB-DU), a data network, a core network, or a radio network controller (RNC), and is not limited here. In addition, the wireless communication node 80 may include (execute) at least one network function, such as an access and mobility management function (AMF), a session management function (SMF), a user plane function (UPF), a policy control function (PCF), an application function (AF), etc. The radio network node 80 may include a processor 800 (such as a microprocessor or an ASIC), a storage unit 810, and a communication unit 820. The storage unit 810 may be any data storage device that stores program code 812 accessed and executed by the processor 800. Examples of the storage unit 810 include, but are not limited to, a SIM, a ROM, a flash memory, a RAM, a hard disk, and an optical data storage device. The communication unit 820 may be a transceiver and is used to send and receive signals (e.g., messages or packets) according to the processing results of the processor 800. In an example, the communication unit 820 communicates via Figure 8 At least one antenna 822 is shown for transmitting and receiving signals.

[0214] In an embodiment, the storage unit 810 and the program code 812 may be omitted. The processor 800 may include a storage unit having stored program code.

[0215] The processor 800 may implement any of the steps described in the exemplary embodiments on the radio network node 80 , for example via executing the program code 812 .

[0216] The communication unit 820 may be a transceiver. Alternatively or additionally, the communication unit 820 may combine a transmitting unit and a receiving unit, both of which are respectively configured to transmit and receive signals to and from a wireless terminal (eg, a user equipment or another wireless network node).

[0217] Fig. 9 A flow chart of a method according to an embodiment of the present disclosure is shown. Fig. 9 The method shown may be used in a first wireless terminal (e.g., UE or source UE) and includes the following steps:

[0218] Step 901: Receive, from a first radio network node, a SL measurement configuration associated with a U2U relay for a first wireless terminal and a second wireless terminal.

[0219] Step 902: Send a measurement report to a first radio network node based on the measurement configuration.

[0220] exist Fig. 9 In an embodiment, a first wireless terminal receives a SL measurement configuration from a first wireless network node (e.g., a serving gNB of the first wireless terminal). The SL measurement configuration is associated with a U2U relay. More specifically, the SL measurement configuration is associated with a U2U relay between the first wireless terminal and a second wireless terminal (e.g., another UE or a target UE). The SL measurement configuration may be configured for any second wireless terminal. Alternatively, the SL measurement configuration may be configured for a specific second wireless terminal. That is, the SL measurement configuration may be configured for each second wireless terminal. Based on the SL measurement configuration, the first wireless terminal sends a measurement report to the first wireless network node.

[0221] In an embodiment, the SL measurement configuration comprises at least one of the following:

[0222] - the threshold(s) used in the measurement reporting event,

[0223] - one or more filter criteria for filtering measurement reports triggered by a measurement report event, or

[0224] - Measurement quantities associated with U2U relaying.

[0225] In an embodiment, the measurement reporting event comprises at least one of the following:

[0226] - the link quality of the direct SL between the first wireless terminal and the second wireless terminal is lower than a first threshold,

[0227] - the link quality of the direct SL between the first wireless terminal and the second wireless terminal is lower than a second threshold, and the link quality of the first hop between the first U2U relay candidate and the first wireless terminal is greater than a third threshold,

[0228] - the link quality of the first hop between the second U2U relay candidate and the first wireless terminal is greater than a fourth threshold,

[0229] - the link quality of a first hop between the third U2U relay candidate and the first wireless terminal and the link quality of a second hop between the third U2U relay candidate and the second wireless terminal are greater than a fifth threshold,

[0230] - the link quality of a first hop and a second hop of the indirect SL is lower than a sixth threshold, wherein the first hop is between the first wireless terminal and a U2U relay serving the indirect SL for the first wireless terminal and the second wireless terminal, and the second hop is between the second wireless terminal and the U2U relay serving the indirect SL for the first wireless terminal and the second wireless terminal, or

[0231] - The link quality of the direct SL between the first wireless terminal and the second wireless terminal is greater than a seventh threshold.

[0232] In an embodiment, the filtering criteria is / includes threshold(s) that filters out (eg, removes) U2U relay candidates having a link quality less than / below a threshold.

[0233] For example, the one or more filtering criteria include at least one of the following:

[0234] - an eighth threshold value, the eighth threshold value being configured to / used to filter out the fourth U2U relay candidate if the link quality of the first hop between the fourth U2U relay candidate and the first wireless terminal is lower than the eighth threshold value, or

[0235] - a ninth threshold value configured to filter out the fifth U2U relay candidate if the link quality of the second hop between the fifth U2U relay candidate and the second wireless terminal is lower than the ninth threshold value.

[0236] In an embodiment, the SL measurement configuration is associated with (eg, configured for) an ID of the second wireless terminal (eg, an L2 ID or a local UE ID).

[0237] In an embodiment, the first wireless terminal may receive a path switching configuration from the first wireless network node. The path switching configuration may indicate a path switching toward an indirect SL, which is between the first wireless terminal and the second wireless terminal and is served by a third wireless terminal (e.g., a U2U relay UE). For example, the path switching configuration includes at least one of the following:

[0238] - the ID of the second wireless terminal,

[0239] - the ID of the third wireless terminal, or

[0240] - The timer value of the path switch timer associated with the path switch.

[0241] In an embodiment, the first wireless terminal may start the path switch timer when / upon receiving the path switch configuration.

[0242] In an embodiment, the first wireless terminal may stop the path switch timer upon at least one of the following events:

[0243] - when a first PC5 link between the first wireless terminal and the third wireless terminal and a second PC5 link between the third wireless terminal and the second wireless terminal are established,

[0244] - successfully sending an RRC Reconfiguration SL message to a third wireless terminal,

[0245] - receiving a PC5 radio link control response from a third wireless terminal,

[0246] - receiving an RRC reconfiguration complete SL message from a third wireless terminal,

[0247] - receiving a PDCP response (message) from the second wireless terminal,

[0248] - receiving, from the third wireless terminal, an E2E direct communication response from the second wireless terminal via the third wireless terminal,

[0249] - successfully sending an E2E L2 Link Modification Request message to a third wireless terminal, or

[0250] - An E2E L2 Link Modification Accept message is received from the third wireless terminal.

[0251] In an embodiment, when the path switch timer expires, the first wireless terminal may initiate a relay reselection process.Alternatively or additionally, when the path switch timer expires, the first wireless terminal may send information of path switch failure to the first radio network node.

[0252] In an embodiment, the first wireless network node may send information including / indicating at least one of the following to the first wireless network node: a path switching failure indication, a PC5 link establishment failure indication, an ID of the second wireless terminal, an indication of the first hop between the first wireless terminal and the third wireless terminal, or an indication of the second hop between the third wireless terminal and the second wireless terminal. In an embodiment, the ID of the second wireless terminal is used to indicate that the path switching failure or the PC5 link establishment failure occurs between the first wireless terminal (e.g., the source UE) and the indicated second wireless terminal (e.g., the target UE). In an embodiment, the first hop indication is configured to indicate that the path switching failure or the PC5 link establishment failure occurs between the first hop (between the first wireless terminal and the third wireless terminal). In an embodiment, the second hop indication is configured to indicate that the path switching failure or the PC5 link establishment failure occurs between the second hop (between the second wireless terminal and the third wireless terminal).

[0253] In an embodiment, the first wireless terminal may receive a failure report from the third wireless terminal. The failure report indicates a failure of PC5 link establishment between the third wireless terminal and the second wireless terminal.

[0254] In an embodiment, the first wireless terminal sends an E2EPC5 RRC reconfiguration message indicating PDCP data resumption to the second wireless terminal.

[0255] In an embodiment, the first wireless terminal sends an E2E PC5RRC message indicating PDCP re-establishment to the second wireless terminal.

[0256] In an embodiment, the first wireless terminal receives an E2EPC5 RRC reconfiguration message indicating PDCP data resumption from the second wireless terminal.

[0257] In an embodiment, the first wireless terminal receives an E2E PC5RRC message indicating PDCP re-establishment from the second wireless terminal.

[0258] In an embodiment, a first wireless terminal receives a SL configuration from a first wireless network node. The SL configuration may include at least one of: an indication of PDCP data recovery for the SL between the first wireless terminal and the second wireless terminal, an indication of PDCP data recovery for each E2ESL DRB of the SL between the first wireless terminal and the second wireless terminal, an indication of PDCP reestablishment for the SL between the first wireless terminal and the second wireless terminal, or an indication of PDCP reestablishment for each E2E SL DRB of the SL between the first wireless terminal and the second wireless terminal.

[0259] In an embodiment, the first wireless terminal performs PDCP data recovery or PDCP re-establishment after a path switch toward an indirect SL between the first wireless terminal and the second wireless terminal and served (completed) by a third wireless terminal.

[0260] In an embodiment, the first wireless terminal receives information associated with the second wireless terminal from the third wireless terminal.The information associated with the second wireless terminal may include at least one of: RRC state, serving cell information, or out-of-coverage indication.

[0261] In an embodiment, the first wireless terminal sends information associated with the second wireless terminal to the first radio network node. The information associated with the second wireless terminal may include at least one of the following: RRC state, serving cell information, or out-of-coverage indication.

[0262] In an embodiment, the first wireless terminal sends a measurement configuration including the ID of the second wireless terminal to the third wireless terminal. The third wireless terminal serves an indirect SL between the first wireless terminal and the second wireless terminal. That is, the third wireless terminal is a U2U relay for the first wireless terminal and the second wireless terminal.

[0263] Fig.10 A flow chart of a method according to an embodiment of the present disclosure is shown. Fig.10 The method shown may be used in a third wireless terminal (e.g., a relay UE, a U2U relay UE), and includes the following steps:

[0264] Step 1001: Receive a SL configuration associated with a U2U relay between a first wireless terminal and a second wireless terminal from a wireless network node serving a third wireless terminal.

[0265] Step 1002: Establish a first PC5 link with a first wireless terminal and establish a second PC5 link with a second wireless terminal based on the SL configuration.

[0266] exist Fig.10 In the embodiment of the present invention, a third wireless terminal may be selected to serve an indirect SL between a first wireless terminal (e.g., a source UE) and a second wireless terminal (e.g., a target UE). The third wireless terminal may receive a SL configuration from its serving wireless network node. Note that the serving wireless network node of the third wireless terminal may be the same as or different from the serving wireless network node of the first wireless terminal. Based on the SL configuration, the third wireless terminal establishes a first PC5 link (i.e., the first hop of the indirect SL) with the first wireless terminal and a second PC5 link (i.e., the second hop of the indirect SL) with the second wireless terminal, respectively.

[0267] In an embodiment, the SL configuration includes at least one of the following:

[0268] -U2U relay indication,

[0269] - the ID of the first wireless terminal,

[0270] - the ID of the second wireless terminal,

[0271] - an ID of the pairing of the first wireless terminal and the second wireless terminal,

[0272] - the bearer mapping associated with the E2E SL SLRB to the PC5 RLC channel of the first hop on the indirect SL,

[0273] or

[0274] - Bearer mapping associated with the E2E SL SLRB to the PC5 RLC channel of the second hop on the indirect SL.

[0275] In an embodiment, the bearer mapping includes at least one of the following: E2E SLRB ID, PC5 RLC channel ID of the first hop, PC5 RLC channel ID of the second hop, ingress PC5 RLC channel ID, egress PC5 RLC channel ID, PC5 RLC channel ID between the first wireless terminal and the third wireless terminal, or PC5 RLC channel ID between the third wireless terminal and the second wireless terminal.

[0276] In an embodiment, the third wireless terminal sends a failure report to the first wireless terminal indicating a failure to establish the second PC5 link.

[0277] In an embodiment, the third wireless terminal sends the information of the second wireless terminal to the first wireless terminal. The information of the second wireless terminal includes at least one of the following: RRC state, serving cell information, or out-of-coverage indication.

[0278] In an embodiment, the third wireless terminal may receive a measurement configuration including an ID of the second wireless terminal from the first wireless terminal.

[0279] Fig.11 A flow chart of a method according to an embodiment of the present disclosure is shown. Fig.11 The method shown may be used in a first radio network node (e.g., a BS / gNB / RAN of a source UE) and comprises the following steps:

[0280] Step 1101: Send a SL measurement configuration associated with a U2U relay for the first wireless terminal and a second wireless terminal to a first wireless terminal.

[0281] Step 1102: Receive a measurement report associated with the SL measurement configuration from a first wireless terminal.

[0282] exist Fig.11 In an embodiment, the first wireless network node may send a SL measurement configuration associated with a U2U relay for a first wireless terminal and a second wireless terminal. In an embodiment, the SL measurement configuration may be configured for each second wireless terminal. Alternatively, the SL measurement configuration may be configured for any second wireless terminal that communicates with the first wireless terminal via (directly or indirectly) a SL.

[0283] In an embodiment, the SL measurement configuration comprises at least one of the following:

[0284] - at least one threshold used in measuring reporting events,

[0285] - filter criteria to filter measurement reports triggered by a measurement report event, or

[0286] - Measurement quantities related to U2U relaying.

[0287] In an embodiment, the measurement reporting event comprises at least one of the following:

[0288] - the link quality of the direct SL between the first wireless terminal and the second wireless terminal is lower than a first threshold,

[0289] - the link quality of the direct SL between the first wireless terminal and the second wireless terminal is lower than a second threshold, and the link quality of the first hop between the first U2U relay candidate and the first wireless terminal is greater than a third threshold,

[0290] - the link quality of the first hop between the second U2U relay candidate and the first wireless terminal is greater than a fourth threshold, - the link quality of the first hop between the third U2U relay candidate and the first wireless terminal and the link quality of the second hop between the third U2U relay candidate and the second wireless terminal are greater than a fifth threshold,

[0291] - the link quality of a first hop and a second hop of the indirect SL is lower than a sixth threshold, wherein the first hop is between the first wireless terminal and a U2U relay serving the indirect SL for the first wireless terminal and the second wireless terminal, and the second hop is between the second wireless terminal and the U2U relay serving the indirect SL for the first wireless terminal and the second wireless terminal, or

[0292] - The link quality of the direct SL between the first wireless terminal and the second wireless terminal is greater than a seventh threshold.

[0293] In an embodiment, the filtering criteria include at least one of the following:

[0294] - an eighth threshold value, the eighth threshold value being configured to / used to filter out the fourth U2U relay candidate if the link quality of the first hop between the fourth U2U relay candidate and the first wireless terminal is lower than the eighth threshold value, or

[0295] - a ninth threshold value configured to filter out the fifth U2U relay candidate if the link quality of the second hop between the fifth U2U relay candidate and the second wireless terminal is lower than the ninth threshold value.

[0296] In an embodiment, the SL measurement configuration is associated with an ID of the second wireless terminal (eg, L2 ID or local UE ID).

[0297] In an embodiment, the first wireless terminal may receive a path switching configuration from the first wireless network node. The path switching configuration may indicate a path switching toward an indirect SL, which is between the first wireless terminal and the second wireless terminal and is served by a third wireless terminal (e.g., a U2U relay UE). For example, the path switching configuration may include at least one of the following:

[0298] - the ID of the second wireless terminal,

[0299] - the ID of the third wireless terminal, or

[0300] - The timer value of the path switch timer associated with the path switch.

[0301] In an embodiment, a first wireless network node receives information from a first wireless terminal, the information including at least one of the following: a path switching failure indication, a PC5 link establishment failure indication, an ID of a second wireless terminal, an indication of a first hop between the first wireless terminal and a third wireless terminal, or an indication of a second hop between the second wireless terminal and a third wireless terminal. In an embodiment, the ID of the second wireless terminal is used to indicate that a path switching failure or a PC5 link establishment failure occurs between the first wireless terminal (e.g., a source UE) and an indicated second wireless terminal (e.g., a target UE). In an embodiment, the first hop indication is configured to indicate that a path switching failure or a PC5 link establishment failure occurs between the first hop (between the first wireless terminal and the third wireless terminal). In an embodiment, the second hop indication is configured to indicate that a path switching failure or a PC5 link establishment failure occurs between the second hop (between the second wireless terminal and the third wireless terminal).

[0302] In an embodiment, a first wireless network node sends a SL configuration to a first wireless terminal. The SL configuration (sent to the first wireless terminal) includes at least one of the following: an indication of PDCP data recovery for the SL between the first wireless terminal and the second wireless terminal, an indication of PDCP data recovery for each E2E SL DRB of the SL between the first wireless terminal and the second wireless terminal, an indication of PDCP reestablishment for the SL between the first wireless terminal and the second wireless terminal, or an indication of PDCP reestablishment for each E2E SL DRB of the SL between the first wireless terminal and the second wireless terminal.

[0303] In an embodiment, the first radio network node may send a SL configuration associated with a U2U relay between the first and second wireless terminals to a third wireless terminal. For example, the third wireless terminal may be selected as a U2U relay for the first and second wireless terminals (based on the measurement report).

[0304] In an embodiment, the SL configuration (sent to the third wireless terminal) comprises at least one of the following: - a U2U relay indication,

[0305] - the ID of the first wireless terminal,

[0306] - the ID of the second wireless terminal,

[0307] - an ID of the pairing of the first wireless terminal and the second wireless terminal,

[0308] - a bearer mapping associated with the E2E SLRB to a PC5 RLC channel of a first hop on an indirect SL, wherein the first hop is between the third wireless terminal and the first wireless terminal, and the indirect SL is between the first wireless terminal and the second wireless terminal and passes through the third wireless terminal, or

[0309] - Bearer mapping associated with the E2E SL SLRB to the PC5 RLC channel of the second hop on the indirect SL, wherein the second hop is between the third wireless terminal and the second wireless terminal, and the indirect SL is between the first wireless terminal and the second wireless terminal and passes through the third wireless terminal.

[0310] In an embodiment, the bearer mapping includes at least one of the following: E2E SLRB ID, PC5 RLC channel ID of the first hop, PC5 RLC channel ID of the second hop, ingress PC5 RLC channel ID, egress PC5 RLC channel ID, PC5 RLC channel ID between the first wireless terminal and the third wireless terminal, or PC5 RLC channel ID between the third wireless terminal and the second wireless terminal.

[0311] In an embodiment, the first wireless network node sends SL relay assistance information associated with the third wireless terminal to the second wireless network node (serving the third wireless terminal). In this embodiment, the third wireless terminal can be selected as a U2U relay for the first wireless terminal and the second wireless terminal (e.g., based on the measurement report).

[0312] In an embodiment, the SL relay assistance information includes at least one of the following:

[0313] - serving cell information of the third wireless terminal,

[0314] - ID of the third wireless terminal,

[0315] - the ID of the first wireless terminal,

[0316] - the ID of the second wireless terminal,

[0317] - Bearer mapping between SL signalling radio bearers SRB and PC5 RLC channels,

[0318] - a mapping between a SL Data Radio Bearer DRB and at least one QoS Flow,

[0319] -Bearer mapping between SL DRB and PC5 RLC channels,

[0320] - the packet delay budget PDB associated with each PC5 RLC channel,

[0321] - the PDB associated with each SL DRB,

[0322] - a control plane indication for each PC5 RLC channel, or

[0323] - Channel configuration for each PC5 RLC channel.

[0324] In an embodiment, the first radio network node may receive information of the second wireless terminal from the first wireless terminal. The information of the second wireless terminal may include at least one of the following: RRC state, serving cell information, or out-of-coverage indication.

[0325] In an embodiment, the first wireless network node may send SL related information to a third wireless network node serving the second wireless terminal, for example, to negotiate / determine which U2U relay UE should be selected. The SL related information is sent / generated based on the SL measurement report and the information of the second wireless terminal received from the first wireless terminal UE. For example, the SL related information may include at least one of the following: the (L2) ID of the first wireless terminal, the (L2) ID of the second wireless terminal, a list of U2U relay candidates, the selected U2U relay, the RRC state of each U2U relay candidate, the PC5 link quality between the first wireless terminal and each U2U relay candidate, or the PC5 link quality between each U2U relay candidate and the second wireless terminal.

[0326] In an embodiment, the first radio network node may receive from the third radio network node a selected relay wireless terminal for the first wireless terminal and the second wireless terminal (to relay data transmissions between them).

[0327] Fig.12 A flow chart of a method according to an embodiment of the present disclosure is shown. Fig.12 The method shown may be used in a second radio network node (e.g., BS, gNB, RAN (node)) and comprises the following steps:

[0328] Step 1201: Receive SL relay assistance information associated with a third wireless terminal selected as a U2U relay for a first wireless terminal and a second wireless terminal from a first wireless network node.

[0329] Step 1202: Send a SL configuration associated with the U2U relay between the first wireless terminal and the second wireless terminal to the third wireless terminal.

[0330] In this embodiment, the second radio network node receives SL relay assistance information associated with a third wireless terminal from the first radio network node. In this embodiment, the third wireless terminal is selected as a U2U relay for the first wireless terminal and the second wireless terminal. The third wireless terminal is served by the second radio network node.

[0331] In an embodiment, the SL relay assistance information includes at least one of the following:

[0332] - serving cell information of the third wireless terminal,

[0333] - ID of the third wireless terminal,

[0334] - the ID of the first wireless terminal,

[0335] - the ID of the second wireless terminal,

[0336] - Bearer mapping between SL signalling radio bearers SRB and PC5 RLC channels,

[0337] - a mapping between a SL Data Radio Bearer DRB and at least one QoS Flow,

[0338] -Bearer mapping between SL DRB and PC5 RLC channels,

[0339] - the packet delay budget PDB associated with each PC5 RLC channel,

[0340] - the PDB associated with each SL DRB,

[0341] - a control plane indication for each PC5 RLC channel, or

[0342] - Channel configuration for each PC5 RLC channel.

[0343] In an embodiment, the SL configuration (sent to the third wireless terminal) includes at least one of the following:

[0344] U2U relay indication,

[0345] at least one ID associated with the first wireless terminal and the second wireless terminal,

[0346] a bearer mapping associated with a PC5 RLC channel of an E2E SLRB to a first hop on an indirect SL, wherein the first hop is between the third wireless terminal and the first wireless terminal, and the indirect SL is between the first wireless terminal and the second wireless terminal and passes through the third wireless terminal, or

[0347] A bearer mapping associated with the E2E SL SLRB to a PC5 RLC channel of a second hop on an indirect SL, wherein the second hop is between a third wireless terminal and a second wireless terminal, and the indirect SL is between the first wireless terminal and the second wireless terminal and passes through the third wireless terminal.

[0348] In an embodiment, the bearer mapping includes at least one of the following: E2E SLRB ID, PC5 RLC channel ID of the first hop, PC5 RLC channel ID of the second hop, ingress PC5 RLC channel ID, egress PC5 RLC channel ID, PC5 RLC channel ID between the first wireless terminal and the third wireless terminal, or PC5 RLC channel ID between the third wireless terminal and the second wireless terminal.

[0349] Although various embodiments of the present disclosure have been described above, it should be understood that they are presented by way of example only and not by way of limitation. Similarly, various diagrams may depict example architectures or configurations, which are provided to enable those of ordinary skill in the art to understand the exemplary features and functions of the present disclosure. However, these personnel will understand that the present disclosure is not limited to the illustrated example architectures or configurations, but may be implemented using a variety of alternative architectures and configurations. In addition, as will be understood by those of ordinary skill in the art, one or more features of an embodiment may be combined with one or more features of another embodiment described herein. Therefore, the breadth and scope of the present disclosure should not be limited by any of the exemplary embodiments described above.

[0350] It should also be understood that any reference to an element using names such as "first," "second," etc., herein generally does not limit the quantity or order of those elements. Instead, these names may be used herein as a convenient means of distinguishing between two or more elements or element instances. Therefore, reference to a first element and a second element does not mean that only two elements can be utilized, or that the first element must precede the second element in some way.

[0351] In addition, those of ordinary skill in the art will understand that information and signals may be represented using any of a variety of different techniques and technologies. For example, data, instructions, commands, information, signals, bits, and symbols referenced in the above description may be represented by voltage, current, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0352] The skilled person will further recognize that any of the various illustrative logical blocks, units, processors, devices, circuits, methods, and functions described in conjunction with the aspects disclosed herein may be implemented by electronic hardware (e.g., digital implementations, analog implementations, or a combination of the two), firmware, various forms of programs or design codes containing instructions (for convenience, may be referred to herein as "software" or "software units"), or any combination of these technologies.

[0353] In order to clearly illustrate the interchangeability of such hardware, firmware and software, various illustrative components, blocks, units, circuits and steps have been generally described above in terms of their functionality. Whether such functionality is implemented as hardware, firmware or software or a combination of these technologies depends on the specific application and the design constraints imposed on the entire system. Skilled technicians can implement the described functionality in various ways for each specific application, but such implementation decisions will not result in departing from the scope of this disclosure. According to various embodiments, processors, devices, components, circuits, structures, machines, units, etc. can be configured to perform one or more functions described herein. As used herein with respect to a specific operation or function, the term "configured to" or "configured for" refers to a processor, device, component, circuit, structure, machine, unit, etc. that is physically constructed, programmed and / or arranged to perform a specific operation or function.

[0354] In addition, the technician will understand that the various illustrative logic blocks, units, devices, components and circuits described herein can be implemented or performed in an integrated circuit (IC), which can 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, or any combination thereof. The logic blocks, units and circuits may also include antennas and / or transceivers to communicate with various components within a network or within a device. The general-purpose processor may be a microprocessor, but in an alternative, the processor may be any conventional processor, controller or state machine. The processor may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a combination of multiple microprocessors, a combination of one or more microprocessors combined with a DSP core, or a combination of any other suitable configurations to perform the functions described herein. If implemented in software, the functions may be stored as one or more instructions or codes on a computer-readable medium. Therefore, the steps of the method or algorithm disclosed herein may be implemented as software stored on a computer-readable medium.

[0355] Computer-readable media include both computer storage media and communication media, which include any media that can enable a computer program or code to be transferred from one place to another. Storage media can be any available media accessed by a computer. By way of example and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage devices, or any other media that can be used to store desired program codes in the form of instructions or data structures and can be accessed by a computer.

[0356] In this document, the term "unit" as used herein refers to software, firmware, hardware, and any combination of these elements for performing the associated functions described herein. In addition, for the purpose of discussion, various units are described as discrete units; however, it will be apparent to one of ordinary skill in the art that two or more units can be combined to form a single module that performs associated functions according to embodiments of the present disclosure.

[0357] In addition, in embodiments of the present disclosure, memories or other storage devices and communication components may be used. It will be appreciated that, for clarity, the above description has described embodiments of the present disclosure with reference to different functional units and processors. However, it will be apparent that any suitable functional distribution between different functional units, processing logic elements, or processing domains may be used without departing from the present disclosure. For example, functionality described as being performed by a separate processing logic element or controller may be performed by the same processing logic element or controller. Therefore, references to specific functional units are only references to suitable devices for providing the described functionality, rather than indications of a strict logical or physical structure or organization.

[0358] Various modifications to the embodiments described in the present disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the scope of the claims. Therefore, the present disclosure is not intended to be limited to the embodiments shown herein, but should be given the broadest scope consistent with the novel features and principles disclosed herein, as set forth in the following claims.

Claims

1. A wireless communication method used in a first wireless terminal, the method comprising: receiving, from a first radio network node, a sidelink SL measurement configuration associated with a user-to-user relay for said first wireless terminal and a second wireless terminal, and A measurement report is sent to the first radio network node based on the measurement configuration.

2. The wireless communication method according to claim 1, wherein: The SL measurement configuration includes at least one of the following: measuring at least one threshold used in reporting events, filtering criteria for filtering the measurement reports triggered by the measurement report event, or A measurement quantity associated with the user-to-user relay.

3. The wireless communication method according to claim 2, wherein: The measurement report event includes at least one of the following: The link quality of the direct SL between the first wireless terminal and the second wireless terminal is lower than a first threshold, a link quality of a direct SL between the first wireless terminal and the second wireless terminal is lower than a second threshold, and a link quality of a first hop between a first user-to-user relay candidate and the first wireless terminal is greater than a third threshold, a link quality of a first hop between a second user-to-user relay candidate and the first wireless terminal is greater than a fourth threshold, a link quality of a first hop between a third user-to-user relay candidate and the first wireless terminal and a link quality of a second hop between the third user-to-user relay candidate and the second wireless terminal are greater than a fifth threshold, the link quality of a first hop and a second hop of the indirect SL is lower than a sixth threshold, wherein the first hop is between the first wireless terminal and a user-to-user relay serving the indirect SL for the first wireless terminal and the second wireless terminal, and the second hop is between the second wireless terminal and a user-to-user relay serving the indirect SL for the first wireless terminal and the second wireless terminal, or The link quality of the direct SL between the first wireless terminal and the second wireless terminal is greater than a seventh threshold.

4. The wireless communication method according to claim 2 or 3, wherein: The filtering criteria include at least one of the following: an eighth threshold, the eighth threshold being configured to filter out the fourth user-to-user relay candidate if the link quality of the first hop between the fourth user-to-user relay candidate and the first wireless terminal is lower than the eighth threshold, or A ninth threshold value, wherein the ninth threshold value is configured to filter out the fifth user-to-user relay candidate if the link quality of the second hop between the fifth user-to-user relay candidate and the second wireless terminal is lower than the ninth threshold value.

5. The wireless communication method according to any one of claims 1 to 4, wherein: The SL measurement configuration is associated with the identifier ID of the second wireless terminal.

6. The wireless communication method according to any one of claims 1 to 5, further comprising: receiving, from the first radio network node, a path switch configuration indicating a path switch toward an indirect SL between the first wireless terminal and the second wireless terminal and served by a third wireless terminal, The path switching configuration includes at least one of the following: the ID of the second wireless terminal, the ID of the third wireless terminal, or A timer value of a path switch timer associated with the path switch.

7. The wireless communication method according to claim 6, further comprising at least one of the following: When receiving the path switching configuration, starting the path switching timer, or The path switching timer is stopped when at least one of the following occurs: When a first PC5 link between the first wireless terminal and the third wireless terminal, and a second PC5 link between the third wireless terminal and the second wireless terminal are established, successfully sending a radio resource control RRC reconfiguration SL message to the third wireless terminal, receiving a PC5 radio link control response from said third wireless terminal, receiving an RRC reconfiguration complete SL message from the third wireless terminal, receiving a Packet Data Convergence Protocol (PDCP) response from the second wireless terminal, receiving, from the third wireless terminal, a peer-to-peer direct communication response from the second wireless terminal via the third wireless terminal, successfully sending an end-to-end layer 2 link modification request message to the third wireless terminal, or An end-to-end layer 2 link modification accept message is received from the third wireless terminal.

8. The wireless communication method according to claim 6 or 7, When the path switching timer expires, the method further includes at least one of the following: Initiate a relay reselection process, or Sending information on path switching failure to the first wireless network node.

9. The wireless communication method according to any one of claims 6 to 8, further comprising: Send information to the first wireless network node, the information including at least one of the following: a path switching failure indication, a PC5 link establishment failure indication, an ID of the second wireless terminal, an indication of a first hop between the first wireless terminal and the third wireless terminal, or an indication of a second hop between the third wireless terminal and the second wireless terminal.

10. The wireless communication method according to any one of claims 6 to 9, further comprising: A failure report is received from the third wireless terminal, the failure report indicating a failure of PC5 link establishment between the third wireless terminal and the second wireless terminal.

11. The wireless communication method according to any one of claims 6 to 10, further comprising at least one of the following: sending an end-to-end PC5 RRC reconfiguration message indicating PDCP data recovery to the second wireless terminal, sending an end-to-end PC5 RRC message indicating PDCP reestablishment to the second wireless terminal, receiving an end-to-end PC5 RRC reconfiguration message indicating PDCP data resumption from the second wireless terminal, receiving an end-to-end PC5 RRC message indicating PDCP re-establishment from the second wireless terminal, receiving a SL configuration from the first wireless network node, the SL configuration comprising at least one of: an indication of PDCP data resumption for the SL between the first wireless terminal and the second wireless terminal, an indication of PDCP data resumption for each end-to-end SL data radio bearer (DRB) of the SL between the first wireless terminal and the second wireless terminal, an indication of PDCP reestablishment for the SL between the first wireless terminal and the second wireless terminal, or an indication of PDCP reestablishment for each end-to-end SL DRB of the SL between the first wireless terminal and the second wireless terminal, or A PDCP data recovery or a PDCP re-establishment is performed after the path switch toward the indirect SL, the indirect SL being between the first wireless terminal and the second wireless terminal and being served by the third wireless terminal.

12. The wireless communication method according to any one of claims 1 to 11, further comprising: receiving information of the second wireless terminal from the third wireless terminal, The information of the second wireless terminal includes at least one of the following: radio resource control status, serving cell information, or out-of-coverage indication.

13. The wireless communication method according to any one of claims 1 to 12, further comprising: sending information of the second wireless terminal to the first wireless network node, The information of the second wireless terminal includes at least one of the following: radio resource control status, serving cell information, or out-of-coverage indication.

14. The wireless communication method according to any one of claims 1 to 13, further comprising: A measurement configuration including an ID of the second wireless terminal is sent to a third wireless terminal serving an indirect SL between the first wireless terminal and the second wireless terminal.

15. A wireless communication method used in a third wireless terminal, the method comprising: receiving, from a radio network node serving the third wireless terminal, a side link SL configuration associated with a user-to-user relay between the first wireless terminal and the second wireless terminal, and A first PC5 link is established with the first wireless terminal and a second PC5 link is established with the second wireless terminal based on the SL configuration.

16. The wireless communication method according to claim 15, wherein: The SL configuration includes at least one of the following: User-to-user relay indication, at least one identifier ID associated with the first wireless terminal and the second wireless terminal, a bearer mapping associated with an end-to-end SL radio bearer SLRB to a PC5 radio link control RLC channel of a first hop on an indirect SL, wherein the first hop is between the third wireless terminal and the first wireless terminal, and the indirect SL is between the first wireless terminal and the second wireless terminal and passes through the third wireless terminal, or A bearer mapping associated with an end-to-end SL SLRB to a PC5 RLC channel of a second hop on an indirect SL, wherein the second hop is between the third wireless terminal and the second wireless terminal, and the indirect SL is between the first wireless terminal and the second wireless terminal and passes through the third wireless terminal.

17. The wireless communication method according to claim 16, wherein: The bearer mapping includes at least one of the following: end-to-end SLRB ID, PC5 RLC channel ID of the first hop, PC5 RLC channel ID of the second hop, ingress PC5 RLC channel ID, egress PC5 RLC channel ID, PC5 RLC channel ID between the first wireless terminal and the third wireless terminal, or PC5 RLC channel ID between the third wireless terminal and the second wireless terminal.

18. The wireless communication method according to any one of claims 15 to 17, further comprising at least one of the following: sending a failure report to the first wireless terminal indicating a failure in establishing the second PC5 link, or Information of the second wireless terminal is sent to the first wireless terminal, wherein the information includes at least one of: a radio resource control state, serving cell information, or an out-of-coverage indication.

19. The wireless communication method according to any one of claims 15 to 18, further comprising: A measurement configuration including an ID of the second wireless terminal is received from the first wireless terminal.

20. A wireless communication method for use in a first wireless network node, the method comprising: sending to a first wireless terminal a sidelink SL measurement configuration associated with a user-to-user relay for said first wireless terminal and a second wireless terminal, and Receive a measurement report associated with the SL measurement configuration from the first wireless terminal.

21. The wireless communication method according to claim 20, wherein: The SL measurement configuration includes at least one of the following: measuring at least one threshold used in reporting events, filtering criteria for filtering the measurement reports triggered by the measurement report event, or A measurement quantity associated with the user-to-user relay.

22. The wireless communication method according to claim 21, wherein: The measurement report event includes at least one of the following: The link quality of the direct SL between the first wireless terminal and the second wireless terminal is lower than a first threshold, a link quality of a direct SL between the first wireless terminal and the second wireless terminal is lower than a second threshold, and a link quality of a first hop between a first user-to-user relay candidate and the first wireless terminal is greater than a third threshold, a link quality of a first hop between a second user-to-user relay candidate and the first wireless terminal is greater than a fourth threshold, a link quality of a first hop between a third user-to-user relay candidate and the first wireless terminal and a link quality of a second hop between the third user-to-user relay candidate and the second wireless terminal are greater than a fifth threshold, the link quality of a first hop and a second hop of the indirect SL is lower than a sixth threshold, wherein the first hop is between the first wireless terminal and a user-to-user relay serving the indirect SL for the first wireless terminal and the second wireless terminal, and the second hop is between the second wireless terminal and a user-to-user relay serving the indirect SL for the first wireless terminal and the second wireless terminal, or The link quality of the direct SL between the first wireless terminal and the second wireless terminal is greater than a seventh threshold.

23. The wireless communication method according to claim 21 or 22, wherein: The filtering criteria include at least one of the following: an eighth threshold, the eighth threshold being configured to filter out the fourth user-to-user relay candidate if the link quality of the first hop between the fourth user-to-user relay candidate and the first wireless terminal is lower than the eighth threshold, or A ninth threshold value, wherein the ninth threshold value is configured to filter out the fifth user-to-user relay candidate if the link quality of the second hop between the fifth user-to-user relay candidate and the second wireless terminal is lower than the ninth threshold value.

24. The wireless communication method according to any one of claims 20 to 23, wherein: The SL measurement configuration is associated with the identifier ID of the second wireless terminal.

25. The wireless communication method according to any one of claims 20 to 24, further comprising: sending a path switch configuration indicating a path switch toward an indirect SL between the first wireless terminal and the second wireless terminal and served by a third wireless terminal to the first wireless terminal, The path switching configuration includes at least one of the following: the ID of the second wireless terminal, the ID of the third wireless terminal, or A timer value of a path switch timer used for the path switch.

26. The wireless communication method according to claim 25, further comprising: Receive information from the first wireless terminal, the information including at least one of: a path switching failure indication, a PC5 link establishment failure indication, an ID of the second wireless terminal, an indication of a first hop between the first wireless terminal and the third wireless terminal, or an indication of a second hop between the second wireless terminal and the third wireless terminal.

27. The wireless communication method according to any one of claims 20 to 26, further comprising: A SL configuration is sent to the first wireless terminal, wherein the SL configuration includes at least one of: an indication of a Packet Data Convergence Protocol (PDCP) data recovery for the SL between the first wireless terminal and the second wireless terminal, an indication of a PDCP data recovery for each end-to-end SL data radio bearer (DRB) of the SL between the first wireless terminal and the second wireless terminal, an indication of a PDCP re-establishment of the SL between the first wireless terminal and the second wireless terminal, or an indication of a PDCP re-establishment of each end-to-end SL DRB of the SL between the first wireless terminal and the second wireless terminal.

28. The wireless communication method according to any one of claims 20 to 27, further comprising: sending a SL configuration associated with a user-to-user relay between the first wireless terminal and the second wireless terminal to a third wireless terminal, The third wireless terminal is selected as a user-to-user relay for the first wireless terminal and the second wireless terminal based on the measurement report.

29. The wireless communication method according to claim 28, wherein: The SL configuration includes at least one of the following: User-to-user relay indication, the ID of the first wireless terminal, the ID of the second wireless terminal, a bearer mapping associated with an end-to-end SL radio bearer SLRB to a PC5 radio link control RLC channel of a first hop on an indirect SL, wherein the first hop is between the third wireless terminal and the first wireless terminal, and the indirect SL is between the first wireless terminal and the second wireless terminal and passes through the third wireless terminal, or A bearer mapping associated with an end-to-end SL SLRB to a PC5 RLC channel of a second hop on an indirect SL, wherein the second hop is between the third wireless terminal and the second wireless terminal, and the indirect SL is between the first wireless terminal and the second wireless terminal and passes through the third wireless terminal.

30. The wireless communication method according to claim 29, wherein: The bearer mapping includes at least one of the following: end-to-end SLRB ID, PC5 RLC channel ID of the first hop, PC5 RLC channel ID of the second hop, ingress PC5 RLC channel ID, egress PC5 RLC channel ID, PC5 RLC channel ID between the first wireless terminal and the third wireless terminal, or PC5 RLC channel ID between the third wireless terminal and the second wireless terminal.

31. The wireless communication method according to any one of claims 20 to 27, further comprising: sending SL relay assistance information associated with the third wireless terminal to the second wireless network node, The third wireless terminal is selected as a user-to-user relay for the first wireless terminal and the second wireless terminal based on the measurement report, and is served by the second wireless network node.

32. The wireless communication method according to claim 31, wherein: The SL relay assistance information includes at least one of the following: The serving cell information of the third wireless terminal, the ID of the third wireless terminal, the ID of the first wireless terminal, the ID of the second wireless terminal, Bearer mapping between SL signaling radio bearers SRB and PC5 RLC channels, a mapping between a SL data radio bearer DRB and at least one quality of service QoS flow, Bearer mapping between SL DRB and PC5 RLC channels, The packet delay budget PDB associated with each PC5 RLC channel, The PDB associated with each SL DRB, Control plane indication for each PC5 RLC channel, or Channel configuration for each PC5 RLC channel.

33. The wireless communication method according to any one of claims 20 to 32, further comprising: receiving information of the second wireless terminal from the first wireless terminal, The information of the second wireless terminal includes at least one of the following: radio resource control status, serving cell information, or out-of-coverage indication.

34. A wireless communication method for use in a second wireless network node, the method comprising: receiving, from the first radio network node, sidelink (SL) relay assistance information associated with a third wireless terminal selected for user-to-user relay for the first wireless terminal and the second wireless terminal, and A SL configuration associated with the user-to-user relay between the first wireless terminal and the second wireless terminal is sent to the third wireless terminal.

35. The wireless communication method according to claim 34, wherein: The SL relay assistance information includes at least one of the following: The serving cell information of the third wireless terminal, an identifier ID of the third wireless terminal, the ID of the first wireless terminal, the ID of the second wireless terminal, Bearer mapping between SL signaling radio bearers SRB and PC5 RLC channels, a mapping between a SL data radio bearer DRB and at least one quality of service QoS flow, Bearer mapping between SL DRB and PC5 RLC channels, The packet delay budget PDB associated with each PC5 RLC channel, The PDB associated with each SL DRB, Control plane indication for each PC5 RLC channel, or Channel configuration for each PC5 RLC channel.

36. The wireless communication method according to claim 34 or 35, wherein: The SL configuration includes at least one of the following: User-to-user relay indication, the ID of the first wireless terminal, the ID of the second wireless terminal, a bearer mapping associated with an end-to-end SL radio bearer SLRB to a PC5 radio link control RLC channel of a first hop on an indirect SL, wherein the first hop is between the third wireless terminal and the first wireless terminal, and the indirect SL is between the first wireless terminal and the second wireless terminal and passes through the third wireless terminal, or A bearer mapping associated with an end-to-end SL SLRB to a PC5 RLC channel of a second hop on an indirect SL, wherein the second hop is between the third wireless terminal and the second wireless terminal, and the indirect SL is between the first wireless terminal and the second wireless terminal and passes through the third wireless terminal.

37. The wireless communication method according to claim 36, wherein: The bearer mapping includes at least one of the following: end-to-end SLRB ID, PC5 RLC channel ID of the first hop, PC5 RLC channel ID of the second hop, ingress PC5 RLC channel ID, egress PC5 RLC channel ID, PC5 RLC channel ID between the first wireless terminal and the third wireless terminal, or PC5 RLC channel ID between the third wireless terminal and the second wireless terminal.

38. A first wireless terminal, the first wireless terminal comprising: A communication unit, wherein the communication unit is configured to: receiving, from a first radio network node, a sidelink SL measurement configuration associated with a user-to-user relay for said first wireless terminal and a second wireless terminal, and A measurement report is sent to the first radio network node based on the measurement configuration.

39. The first wireless terminal according to claim 38, further comprising: A processor, wherein the processor is configured to execute the wireless communication method according to any one of claims 2 to 14.

40. A third wireless terminal, the third wireless terminal comprising: a communication unit configured to receive, from a radio network node serving the third wireless terminal, a side link SL configuration associated with a user-to-user relay between the first wireless terminal and the second wireless terminal, and A processor configured to establish a first PC5 link with the first wireless terminal and establish a second PC5 link with the second wireless terminal based on the SL configuration.

41. The third wireless terminal according to claim 40, wherein: The processor is further configured to perform the wireless communication method according to any one of claims 16 to 19.

42. A first wireless network node, the first wireless network node comprising: A communication unit, wherein the communication unit is configured to: sending to a first wireless terminal a sidelink SL measurement configuration associated with a user-to-user relay for said first wireless terminal and a second wireless terminal, and Receive a measurement report associated with the SL measurement configuration from the first wireless terminal.

43. The first radio network node according to claim 42, further comprising: A processor, wherein the processor is configured to execute the wireless communication method according to any one of claims 21 to 33.

44. A second wireless network node, the second wireless network node comprising: A communication unit, wherein the communication unit is configured to: receiving, from the first radio network node, sidelink (SL) relay assistance information associated with a third wireless terminal selected for user-to-user relay for the first wireless terminal and the second wireless terminal, and A SL configuration associated with a user-to-user relay between the first wireless terminal and the second wireless terminal is sent to the third wireless terminal.

45. The second radio network node according to claim 44, further comprising: A processor, wherein the processor is configured to execute the wireless communication method according to any one of claims 35 to 37.

46. ​​A computer program product comprising computer readable program medium code stored thereon, which, when executed by a processor, causes the processor to implement the wireless communication method according to any one of claims 1 to 37.

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