System and method for device-to-device relay communication

Abstract

The arrangements described herein relate to systems, methods, apparatuses and non-transitory computer readable media of a relay UE that provides a source ID of a source wireless communication device to a target UE for an end-to-end (E2E) unicast link between the source UE and the target UE. The relay UE provides the target ID of the target UE to the source UE for the E2E unicast link.

Description

Technical Field

[0001] The present disclosure generally relates to wireless communication, and more particularly, to Device-to-Device (D2D) relay communication and Sidelink (SL) communication. Background Art

[0002] SL communication refers to radio communication between two or more User Equipments (UEs). In this type of communication, two or more UEs that are geographically close to each other can communicate without being routed to a Base Station (BS) or a core network. Data transmission in SL communication is thus different from typical cellular network communication that includes sending data to the BS and receiving data from the BS. In SL communication, data is directly sent from a source UE to a target UE (or target UEs) through, for example, a unified air interface (e.g., the PC5 interface) without passing through the BS. Summary of the Invention

[0003] The example arrangements disclosed herein are intended to solve problems related to one or more difficulties presented in the prior art, and to provide additional features that will become apparent when the following detailed description is read in conjunction with the accompanying drawings. According to various arrangements, example systems, methods, devices, and computer program products are disclosed herein. However, it is understood that these arrangements are presented by way of example and not limitation, and it will be apparent to those of ordinary skill in the art who read this disclosure that various modifications can be made to the disclosed arrangements while remaining within the scope of this disclosure.

[0004] In some arrangements, a relay UE provides a source ID of a source wireless communication device to a target UE for an end-to-end (E2E) unicast link between the source UE and the target UE. The relay UE provides a target ID of the target UE to the source UE for the E2E unicast link.

[0005] The above and other aspects and their implementations are described in more detail in the drawings, the description, and the claims. Brief Description of the Drawings

[0006] The following describes various example arrangements of the present solution in detail with reference to the following figures or drawings. The drawings are provided for illustrative purposes only and merely depict example arrangements of the present solution to facilitate the reader's understanding of the present solution. Therefore, the drawings should not be considered as a limitation on the breadth, scope, or applicability of the present solution. It should be noted that these drawings are not necessarily drawn to scale for clarity and convenience of illustration..

[0007] Figure 1A is a schematic block diagram showing an example wireless communication system supporting SL communication according to various arrangements.

[0008] Figure 1B is a schematic block diagram showing an example wireless communication system supporting SL communication according to various arrangements.

[0009] Figure 2 A block diagram of an example base station (BS) and an example user equipment (UE) according to some arrangements is shown.

[0010] Figure 3 is a diagram showing a protocol stack of a user plane for a layer 2 (L2) UE-to-UE (U2U) relay architecture according to various arrangements.

[0011] Figure 4A is a diagram showing an example method for establishing an end-to-end (E2E) link between a source UE and a target UE via at least one relay UE according to various arrangements.

[0012] Figure 4B is a diagram showing an example method for establishing an E2E link between a source UE and a target UE via at least one relay UE according to various arrangements.

[0013] Figure 4C is a diagram showing an example method for establishing an E2E link between a source UE and a target UE via at least one relay UE according to various arrangements.

[0014] Figure 5 is a diagram showing an example method for establishing an E2E link between a source UE and a target UE via a relay UE according to various arrangements.

[0015] Figure 6 is a diagram showing an example method for transmitting a UE ID in an E2E link between a source UE and a target UE according to various arrangements.

[0016] Figure 7 is a diagram showing an example method for transmitting a UE ID in a first E2E link between a source UE and a target UE and a second E2E link between the source UE and the target UE according to various arrangements.

[0017] Figure 8 is a diagram showing an example method for transmitting a UE ID in an E2E link between a first UE and a second UE according to various arrangements.

[0018] Figure 9 is a diagram showing an example method for transmitting a UE ID in an E2E link between a first UE and a second UE according to various arrangements. Detailed Description

[0019] The following describes various exemplary arrangements of the present solution with reference to the accompanying drawings, so that those of ordinary skill in the art can make and use the present solution. It is obvious to those of ordinary skill in the art that after reading this disclosure, various changes or modifications can be made to the examples described herein without departing from the scope of the present solution. Therefore, the present solution is not limited to the exemplary arrangements and applications described and illustrated herein. In addition, the specific order or hierarchy of steps in the methods disclosed herein is merely an example method. Based on design preferences, the specific order or hierarchy of the steps of the disclosed method or process can be rearranged while remaining within the scope of the present solution. Therefore, those of ordinary skill in the art will understand that the methods and techniques disclosed herein present various steps or actions in an example order, and the present solution is not limited to the specific order or hierarchy presented unless otherwise expressly stated.

[0020] With the emergence of wireless multimedia services, users' demands for high data rates and user experience are increasing continuously, which poses higher requirements on the system capacity and coverage of traditional cellular networks. In addition, public safety, social networks, proximity data sharing, indoor relay communication, smart agriculture, smart factories, public safety, and local advertising have gradually expanded the demand for proximity services, which enable users to learn about and communicate with nearby users or objects. Traditional BS-centered cellular networks have limited high data rate capabilities and support for proximity services. SL is an adaptation and improvement of BS-centered communication technologies by allowing direct communication between two devices without going through the BS. For example, vehicles, robots, and consumer gadgets can create their own ad-hoc networks without directly using the radio access network as an intermediary.

[0021] The application of SL technology can meet the high data rate requirements for proximity services, relieve the burden on cellular networks, reduce the battery power consumption of UEs, and improve the robustness of network infrastructure, thus meeting the above requirements for high data rate services and proximity services. SL services can also be referred to as device-to-device (D2D) discovery and communication, proximity services (ProSe), unilateral communication, sidelink communication, SL discovery and communication, and so on. An example of the interface between two UEs that facilitates SL communication is the PC5 interface.

[0022] In some arrangements, to support layer 2 (L2) user equipment to user equipment (U2U) relay communication, an adaptation layer is provided via both a first PC5 hop and a second PC5 hop. The adaptation header of the adaptation layer includes a bearer identifier (ID) that identifies the end-to-end SL radio bearer between the source UE and the target UE. In addition, at least one ID that can be mapped to the target UE is included in the adaptation header of the first hop between the source UE and the relay UE to identify the destination of the packet to the relay UE, and the ID that can be mapped to the source UE is included in the adaptation header of the second hop between the relay UE and the target UE to identify the source of the packet for the target UE. In the arrangements disclosed herein, the ID is mappable to the source / target UE, and it is not clear how the involved UE (source / target / relay UE) negotiates / allocates / obtains the ID mappable to the source / target UE and how to support U2U relay communication in a multi-hop scenario.

[0023] Figure 1A is a schematic block diagram showing an example wireless communication system 100a that supports SL communication according to various arrangements. In system 100a, BS 102 (e.g., a network-side communication node, a wireless communication node, etc.) may include a next-generation node B (gNB), an E-UTRAN node B (also referred to as an evolved node B, eNodeB, or eNB), a pico station, a femto station, a Transmission / Reception Point (TRP), an Access Point (AP), etc. Each of UEs 104a and 104b (e.g., a terminal-side node, a wireless communication device, etc.) may include a device such as a mobile device, a smart phone, a cellular phone, a Personal Digital Assistant (PDA), a tablet computer, a laptop computer, a wearable device, a vehicle with an in-vehicle communication system, etc. Figure 1A shows a user equipment to network (UE-to-Network, U2N) deployment scenario.

[0024] In Figure 1AAmong them, BS102 can provide wireless communication services to UEs within cell 101, and at least UE 104a is located in this cell. UE 104a can move or remain stationary within the coverage area of cell 101. UE 104a can communicate with BS102 via communication channel 103a. UEs 104a and 104b can communicate with each other via communication channel 103a. The communication channel 103a between UE 104a and BS102 can be implemented using an interface such as the Uu interface, which is also known as the Universal Mobile Telecommunication System (UMTS) air interface. The communication channel 103b between UEs 104a and 104b is a SL communication channel and can be implemented using an interface such as the PC5 interface. The SL communication interface is introduced to address high mobility speed and high-density applications, such as, for example, D2D communication, Vehicle-to-Vehicle (V2V) communication, Vehicle-to-Pedestrian (V2P) communication, Vehicle-to-Infrastructure (V2I) communication, Vehicle-to-Network (V2N) communication, and the like. In some instances, vehicle network communication modes can be collectively referred to as Vehicle-to-Everything (V2X) communication. BS102 is connected to the core network (CN) 108 via an external interface 107 (such as the Iu interface).

[0025] To improve the support for applications and services (e.g., in indoor relay communication, smart agriculture, smart factories, public safety, etc.), SL-based relay communication can be used to extend the coverage area and improve power consumption. In Figure 1AIn this case, a remote UE (e.g., UE 104b) may be in an area with weak or no coverage from BS102 and cell 101. Therefore, UE104b does not communicate directly with BS102 or CN 108, but instead uses the SL communication channel 103b and communicates indirectly with BS102 and CN 108 via a relay UE (e.g., UE104a). UE 104a may communicate directly with BS102 and CN 108 or communicate indirectly with BS102 and CN 108 via at least one other relay UE that can communicate directly with BS102 and CN 108. Thus, the coverage of the network is extended and the capacity of the network is increased. UE 104a is referred to as a U2N relay, and UE 104b is referred to as a remote UE. In an example where UE 104b is within the coverage of BS102 and cell 101, UE 104b may switch to a direct path, similar to communication channel 103a. Additionally, multipath relay may be supported. For example, a remote UE 104b within coverage is connected to CN 108 via both a direct path and an indirect path, thus improving reliability / robustness as well as throughput. A direct path refers to a path through which data is directly transmitted between UE 104b and BS102 via a direct communication channel. A direct path refers to a path that includes both a direct path (e.g., communication channel 103a) and at least one SL path (e.g., communication channel 103b) such that data from UE 104b is forwarded to BS102 via relay UE 104a.

[0026] Figure 1B is a schematic block diagram showing an example wireless communication system 100b that supports SL communication according to various arrangements. In system 100b, each of UE 106a, 106b, and 106c (e.g., a terminal-side node, a wireless communication device, etc.) may include a device such as a mobile device, a smart phone, a cellular phone, a PDA, a tablet computer, a laptop computer, a wearable device, a vehicle with an in-vehicle communication system, etc. Figure 1B shows a U2U deployment scenario.

[0027] In some scenarios, such as those involving disasters or emergencies, the cellular network (including CN 108 and BS102) may not function properly. To expand the coverage of SL communication, multi-hop relay using one or more UE devices may be implemented. As Figure 1BAs shown, UE 106a communicates with UE 106c via UE 106b. UE 106b can be referred to as a U2U relay device or a relay UE. The UEs 106a and 106c can be referred to as remote UEs. The communication channel 105a between UE 106a and 106B is a SL communication channel and can be implemented using an interface such as the PC5 interface. The communication channel 105b between UE 106b and 106C is a SL communication channel and can be implemented using an interface such as the PC5 interface.

[0028] Figure 2 A block diagram of an example BS202 and an example UE 204 is shown in accordance with some arrangements. BS202 is an example of BS102. UE 204 is an example of the UEs 104a, 104b, 106a, 106b, and 106c described herein, as well as any source UE, target UE, and relay UE.

[0029] BS202 includes a BS (base station) transceiver module 210, a BS antenna 212, a BS processor module 214, a BS memory module 216, and a network communication module 218, each module being coupled and interconnected with each other via a data communication bus 220 as needed. UE 204 includes a UE transceiver module 230, a UE antenna 232, a UE memory module 234, and a UE processor module 236, each module being coupled and interconnected with each other via a data communication bus 240 as needed. BS202 communicates with UE 204 via a communication channel, and this communication channel 250 can be any wireless channel or other medium suitable for transmitting data as described herein.

[0030] BS202 and UE 204 may also include any number of modules other than those Figure 2 shown. Those skilled in the art will understand that the various illustrative blocks, modules, circuits, and processing logics described in connection with the embodiments disclosed herein can be implemented in hardware, computer-readable software, firmware, or any practical combination thereof. For the sake of clarity in illustrating the interchangeability and compatibility of hardware, firmware, and software, the various illustrative components, blocks, modules, circuits, and steps are generally described in terms of their functions. Whether such a function is implemented as hardware, firmware, or software can depend on the particular application and the design constraints imposed on the overall system. Those familiar with the concepts described herein can implement such a function in a suitable manner for each particular application, but such implementation decisions should not be construed as limiting the scope of the present disclosure.

[0031] According to some embodiments, the UE transceiver 230 may be referred to herein as the UL transceiver 230, which includes a radio frequency (RF) transmitter and an RF receiver, each of the RF transmitter and the RF receiver including circuitry coupled to an antenna 232. A duplex switch (not shown) may alternately couple the UL transmitter or receiver to the UL antenna in a time-division duplex manner. Similarly, according to some embodiments, the BS transceiver 210 may be referred to herein as the downlink (DL) transceiver 210, which includes an RF transmitter and an RF receiver, each of the RF transmitter and the RF receiver including circuitry coupled to an antenna 212. The DL duplex switch may alternately couple the DL transmitter or receiver to the DL antenna 212 in a time-division duplex manner. The operations of the two transceiver modules 210 and 230 may be coordinated in time such that the UL receiver circuitry is coupled to the UL antenna 232 to receive transmissions over a wireless transmission link while the DL transmitter is coupled to the DL antenna 212. In some embodiments, there is tight time synchronization with a minimum guard time between changes in the duplex direction.

[0032] The UE transceiver 230 and the BS transceiver 210 are configured to communicate via a wireless data communication link and cooperate with a suitably configured RF antenna arrangement 212 / 232 capable of supporting a particular wireless communication protocol and modulation scheme. In some illustrative embodiments, the UE transceiver 230 and the BS transceiver 210 are configured to support industry standards such as Long-Term Evolution (LTE) and emerging 5G and 6G standards and the like. However, it should be understood that the present disclosure is not necessarily limited to the application of specific standards and related protocols. Instead, the UE transceiver 230 and the BS transceiver 210 may be configured to support alternative or additional wireless data communication protocols, including future standards or variants thereof. The UE transceivers 230 of different UEs 204 are configured to communicate via the SL wireless data communication link as described herein.

[0033] According to various embodiments, for example, BS202 can be an eNB, gNB, serving eNB, target eNB, femtocell, TRP, or pico cell, or another UE. In some embodiments, UE 204 can be various types of user equipment, such as a mobile phone, smartphone, PDA, tablet computer, laptop computer, wearable computing device, terminal, etc. Processor modules 214 and 236 can be implemented or realized with a general-purpose processor, content addressable memory, digital signal processor, application specific integrated circuit, field programmable gate array, any suitable programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, which are designed to perform the functions described herein. In this way, the processor can be implemented as a microprocessor, controller, microcontroller, state machine, etc. The processor can also be implemented as a combination of computing devices, for example, a combination of a digital signal processor and a microprocessor, multiple microprocessors, the combination of one or more microprocessors and digital signal processor cores, or any other such configuration.

[0034] In addition, the described methods related to the embodiments disclosed herein can be directly implemented in hardware, firmware, software modules executed by processor modules 214 and 236 respectively, or any practical combination thereof. Memory modules 216 and 234 can be implemented as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art. In this regard, memory modules 216 and 234 can be respectively coupled to processor modules 210 and 230, such that processor modules 210 and 230 can respectively read information from and write information to memory modules 216 and 234. Memory modules 216 and 234 can also be integrated into their respective processor modules 210 and 230. In some embodiments, memory modules 216 and 234 can each include a cache memory for storing temporary variables or other intermediate information during the execution of instructions to be respectively executed by processor modules 210 and 230. Memory modules 216 and 234 can also each include non-volatile memory for storing instructions to be respectively executed by processor modules 210 and 230.

[0035] The network communication module 218 represents the hardware, software, firmware, processing logic, and / or other components of the BS 202 that enable two-way communication between the BS transceiver 210 and other network components, as well as communication nodes configured to communicate with the BS 202, such as those associated with the CN 108. For example, the network communication module 218 may be configured to support Internet or WiMAX traffic. In a typical deployment, but not limited to, the network communication module 218 provides an 802.3 Ethernet interface such that the BS transceiver 210 can communicate with a traditional computer network based on Ethernet. In this manner, the network communication module 218 may include a physical interface for connecting to a computer network (e.g., a mobile switching center (MSC)). As used herein, the terms "configured for," "configured to," and their variants when used with respect to a specified operation or function refer to a physical construction programmed, formatted, and / or arranged of a device, component, circuit, structure, machine, signal, etc., to perform the specified operation or function.

[0036] The protocol stack of the L2 U2U relay architecture is similar to that of the L2 U2U relay, except that the termination points are two remote UEs. Figure 3It shows the protocol stack of the user plane 300 for the L2 U2U relay architecture according to various arrangements. As shown, the source UE (e.g., UE106a) has various protocol stacks, including the Internet Protocol (IP) layer, the PC5-Service Data Adaptation Protocol (SDAP) layer, the PC5-Packet Data Convergence Protocol (PDCP) layer, the adaptation (ADAPT) layer, the PC5-Radio Link Control (RLC) layer, the PC5-Media Access Control (MAC), and the PC5-Physical (PHY) layer. The U2U relay (e.g., UE 106b) includes an ADAPT layer coupled to the ADAPT layer of the source UE via the first RLC channel (e.g., the first PC5 link), a PC5-RLC layer coupled to the PC5-RLC layer of the source UE via the first RLC channel, a PC5-MAC layer coupled to the PC5-MAC layer of the source UE via the first RLC channel, a PC5-PHY layer coupled to the PC5-PHY layer of the source UE via the first RLC channel, an ADAPT layer coupled to the ADAPT layer of the target UE via the second RLC channel (e.g., the second PC5 link), a PC5-RLC layer coupled to the PC5-RLC layer of the target UE via the second RLC channel, a PC5-MAC layer coupled to the PC5-MAC layer of the target UE via the second RLC channel, and a PC5-PHY layer coupled to the PC5-PHY layer of the target UE via the second RLC channel. The target UE (e.g., UE 106c) includes an ADAPT layer, a PC5-RLC layer, a PC5-MAC layer, and a PC5-PHY layer.

[0037] The ADAPT layer is supported by the first PC5 link and the second PC5 link for L2 U2U relay. The first PC5 link refers to the PC5 link between the source UE and the relay UE. The second PC5 link refers to the PC5 link between the relay UE and the target UE. For L2 U2U relay, the ADAPT layer is configured above the RLC sublayer for the Control Plane (CP) and the User Plane (UP) above the second PC5 link. SL SDAP / PDCP and Radio Resource Control (RRC) terminate between the two remote UEs, while RLC, MAC, and PHY terminate in each PC5 link.

[0038] The adaptation header may include a bearer ID that identifies an end - to - end (E2E) SL radio bearer between a source UE (e.g., UE 106a) and a target UE (e.g., UE 106c). Additionally, in the adaptation header of the first hop (e.g., the first PC5 link or the first RLC channel), an ID that can be mapped to the target UE is included for the relay UE (e.g., UE 106b) to identify the destination of the packet. The ID that can be mapped to the source UE is included in the adaptation header of the second hop (e.g., the second PC5 link or the second RLC channel) for the target UE to identify the source of the packet.

[0039] For L2 U2U relay communication, after per - hop PC5 unicast links have been established between the source UE and the relay UE and between the relay UE and the target UE, an E2E PC5 unicast link can be established between the source UE and the target UE. Conventionally, after the per - hop PC5 unicast links are established, each of the source UE, the relay UE, and the target UE is provided with the user information IDs of the other two UEs. The source UE obtains the L2 ID of the relay UE for the PC5 unicast link communication of the first hop. The target UE obtains the L2 ID of the relay UE for the PC5 unicast link communication of the second hop. The relay UE obtains the L2 IDs of the source UE and the target UE for the two - hop PC5 unicast link communication. Conventionally, the source UE, the relay UE, and the target UE are not provided with the L2 IDs of the source UE and the target UE for the E2E PC5 unicast link.

[0040] Conventionally, a UE obtains the L2 ID of a peer UE during the PC5 unicast link establishment process. For L2 U2U relay communication, in an example where the L2 ID is used as the ID that can be mapped to the source UE and the target UE in the adaptation header, before the E2E PC5 unicast link is established, the source UE and the target UE are provided with each other's L2 IDs for the E2E PC5 unicast link. Additionally, the relay UE is provided with the L2 IDs of the source UE and the target UE for the E2E PC5 unicast link for bearer mapping. Some arrangements involve providing the source UE, the target UE, and the relay UE with the L2 IDs of the target UE and the source UE for the E2E PC5 unicast link.

[0041] Figure 4AFIG. is a diagram illustrating an example method 400a for establishing an E2E link between a source UE and a target UE via at least one relay UE according to various arrangements. Method 400a can be performed using system 100b. For example, method 400a can be performed by a relay UE (e.g., UE 106b). The relay UE can communicate with a source UE (e.g., UE 106a) and a target UE (e.g., UE 106c). In some examples, the relay UE can communicate with an upstream relay UE that is between the source UE and the relay UE along the communication path. In such examples, the relay UE communicates indirectly with the source UE via the upstream relay UE. In some examples, the relay UE can communicate with a downstream relay UE that is between the target UE and the relay UE along the communication path. In such examples, the relay UE communicates indirectly with the target UE via the downstream relay UE. An example of an upstream UE and a downstream UE can be UE204.

[0042] At 410, the relay UE provides the source ID (e.g., L2 ID) of the source UE to the target UE for an E2E unicast link between the source UE and the target UE. At 420, the relay UE provides the target ID of the target UE to the source UE for an E2E unicast link between the source UE and the target UE.

[0043] Figure 4B FIG. is a diagram illustrating an example method 400b for establishing an E2E link between a source UE and a target UE via at least one relay UE according to various arrangements. Method 400b can be performed using system 100b. For example, method 400b can be performed by the source UE (e.g., UE 106a). The source UE can communicate with a relay UE (e.g., UE 106b) and a target UE (e.g., UE 106c).

[0044] At 430, the source UE determines the source ID (e.g., L2 ID or local ID) of the source UE for an E2E unicast link between the source UE and the target UE. At 435, the source UE sends the source ID to the relay UE via a PC5-S message or an RRC message. At 440, the source UE receives the target ID (e.g., L2 ID or local ID) of the target UE from the relay UE via a PC5-S message or an RRC message for the E2E unicast link.

[0045] Figure 4C FIG. is a diagram illustrating an example method 400c for establishing an E2E link between a source UE and a target UE via at least one relay UE according to various arrangements. Method 400c can be performed using system 100b. For example, method 400c can be performed by the target UE (e.g., UE 106c). The target UE can communicate with a relay UE (e.g., UE 106b) and a source UE (e.g., UE 106a).

[0046] At 450, the target UE determines a target ID (e.g., an L2 ID or a local ID) of the target UE for an E2E unicast link between the source UE and the target UE. At 455, the target UE sends the target ID to the relay UE via a PC5-S message or an RRC message. At 460, the target UE receives, via a PC5-S message or an RRC message, a source ID (e.g., an L2 ID or a local ID) of the source UE from the relay UE for the E2E unicast link.

[0047] Features described herein with respect to one of methods 400a, 400b, and 400c may equally apply to the other of methods 400a, 400b, and 400c.

[0048] Figure 5 FIG. is a diagram illustrating an example method 500 for establishing an E2E link between a source UE 501 and a target UE 503 via a relay UE according to various arrangements. Method 500 may be performed using system 100b. For example, source UE 501 is an example of UE 106a. U2U relay UE 502 is an example of UE 106b. Target UE 503 is an example of UE 106c. Each of UEs 501, 502, and 503 may be a UE such as UE 204. At 510, source UE 501, relay UE 502, and target UE 503 perform a U2U relay discovery process to find a relay UE that can reach the source UE and the target UE.

[0049] At 520, to serve the source UE and the target UE, e.g., to forward signaling and user data between the source UE and the target UE, source UE 501 and relay UE 502 perform unicast link establishment or link modification for the first hop. The unicast link may be a PC5 unicast link. The first hop, also referred to as the first PC5 link, the first SL channel / link, or the first RLC channel, refers to the communication link or channel between source UE 501 and relay UE 502. An example of the first hop is communication channel 105a between UEs 106a and 106b.

[0050] At 530, to serve the source UE and the target UE, e.g., to forward signaling and user data between the source UE and the target UE, relay UE 502 and target UE 503 perform unicast link establishment or link modification for the second hop. The unicast link may be a PC5 unicast link. The second hop, also referred to as the second PC5 link, the second SL channel / link, or the second RLC channel, refers to the communication link or channel between relay UE 502 and target UE 503. An example of the second hop is communication channel 105b between UEs 106b and 106c.

[0051] At 540, to negotiate the PC5 RLC channel used to send the E2E SL signaling radio bearer (SRB), the source UE 501 and the relay UE 502 perform an RRC reconfiguration (e.g., a PC5 RRC reconfiguration). At 550, to negotiate the PC5 RLC channel used to send the E2E SL-SRB, the relay UE 502 and the target UE 503 perform an RRC reconfiguration (e.g., a PC5 RRC reconfiguration). At 560, the source UE 501, the relay UE 502, and the target UE 503 perform an E2E unicast link to establish an E2E unicast link (e.g., an E2E PC5 unicast link) between the source UE and the target UE.

[0052] In some arrangements, in 520 and 530, the IDs (e.g., L2 IDs) of the UEs 501, 502, and 503 are exchanged using PC5-S messages during the per-hop (or single-hop) unicast link establishment process. For example, the source UE 501 assigns its ID, called the source ID, which is used for the E2E unicast link (e.g., established at 560). The source UE 501 includes this source ID in the first per-hop direct communication request (DCR) message and sends the first per-hop DCR message to the relay UE 502 at 520.

[0053] In some arrangements, the source ID used to identify the source UE 501 for the E2E unicast link may be the same as the per-hop UE ID used to identify the source UE 501 for the per-hop link (e.g., the first hop established in 520). In such arrangements, an indication that the source ID used for the E2E unicast link is the same as the per-hop UE ID used for the per-hop link (e.g., the first hop) is provided in the PC5-S message, and the per-hop UE ID is provided in the MAC header. In some arrangements, the source ID used for the E2E link (established at 560) may be different from the per-hop UE ID used for the first hop. In this case, the source UE 501 provides the per-hop UE ID to the relay UE 502 in the MAC header and provides the source ID to the relay UE 502 in the PC5-S message (e.g., the first per-hop DCR message).

[0054] In 530, the relay UE 502 includes the source ID in the second per-hop DCR message and sends the second per-hop DCR message to the target UE 503. The second per-hop DCR message includes the source ID that the relay UE 502 received from the source UE 501 in the first-hop DCR message, which may be the same as or different from the per-hop UE ID.

[0055] In response to receiving, from the relay UE 502, a second per-hop DCR message including the source ID of the source UE 501, the target UE 503 allocates its ID, referred to as the target ID, which is used for the E2E unicast link (e.g., established at 560). In 530, the target UE 503 includes the target ID in a first per-hop Direct Communication Accept / Acknowledgement (DCA) message and sends the first per-hop DCA message to the relay UE 502. The DCA originating from the target UE 503 responds to the DCR originating from the source device 501. Examples of PC5-S messages include DCR and DCA.

[0056] In some arrangements, the target ID used to identify the target UE 503 for the E2E unicast link may be the same as the per-hop UE ID used to identify the target UE 503 for the per-hop link (e.g., the second hop established at 530). In such arrangements, an indication that the target ID used for the E2E unicast link is the same as the per-hop UE ID used for the per-hop link (e.g., the second hop) is provided in the PC5-S message, and the per-hop UE ID is provided in the MAC header. In some arrangements, the target ID used for the E2E link (established at 560) may be different from the per-hop UE ID used for the second hop, in which case the target UE 501 provides the per-hop UE ID in the MAC header and provides the target ID to the relay UE 502 in the PC5-S message (e.g., the first per-hop DCA message).

[0057] In 520, the relay UE 502 includes the target ID in the per-hop DCA message for the first hop and sends the per-hop DCA message for the first hop to the source UE 501. The per-hop DCA message includes the target ID that the relay UE 502 received from the target UE 503 in the per-hop DCA message for the second hop, which may be the same as or different from the per-hop UE ID.

[0058] As used herein, the source ID is the ID that identifies the source UE (also referred to as the first UE), which may be the source of a message, data packet, signal, command, etc., or the target of a message, data packet, signal, command, etc. originating from another device such as the target device. The target ID is the ID that identifies the target UE (also referred to as the second UE), which may be the target of a message, data packet, signal, command, etc., or is intended for a message, data packet, signal, command, etc. for another device such as the source device.

[0059] In some arrangements, in method 400a, a source ID is provided using a first PC5-S message received by a relay UE from a source UE and a second PC5-S message sent by the relay UE to a target UE.

[0060] In some arrangements, in method 400a, providing the source ID to the target UE at 410 includes: receiving, by the relay UE from the source UE via a first link (e.g., first hop) between the source UE and the relay UE, a first PC5-S message (first DCR). The first PC5-S message includes one of the following: a source ID that is used to identify the source device for the first link (the source ID is different from an ID such as a per-hop UE ID) or an indication that the source ID for an E2E unicast link is the same as the ID used to identify the source device for the first link. The ID used to identify the source UE for the first link is included in the MAC header of the first link. Method 400a further includes sending, by the relay UE to the target UE via a second link (second hop) between the relay UE and the target UE, a second PC5-S message (e.g., second DCR) that includes the source ID.

[0061] In some arrangements, in method 400a, providing the target ID to the source UE at 420 includes receiving, by the relay UE from the target UE via a second link (second hop) between the target UE and the relay UE, a third PC5-S message. The third PC5-S message includes one of the target IDs (the target ID is different from an ID, such as a per-hop UE ID, that is used to identify the target UE for the second link) or an indication that the target for an E2E unicast link is the same as the ID used to identify the target UE for the first link. The ID used to identify the target UE for the first link is included in the MAC header of the first link. Method 400a further includes sending, by the relay UE to the source UE via a first link (first hop) between the relay UE and the source UE, a fourth PC5-S message (e.g., second DCA) that includes the target ID.

[0062] In some arrangements, in 540 and 550, the IDs (e.g., L2 IDs) of UEs 501, 502, and 503 are exchanged via a PC5-RRC message during a per-hop (or single-hop) PC5 RRC reconfiguration procedure. For example, source UE 501 allocates its source ID, which is used for an E2E unicast link (e.g., established at 560). In 540, source UE 501 includes the source ID in a first RRC message (e.g., RRC reconfiguration SL message or RRCReconfigurationSidelink message) and sends the first RRC message to relay UE 502.

[0063] In some arrangements, the source ID used to identify the source UE 501 for an E2E unicast link can be the same as the per-hop UE ID used to identify the source UE 501 for each hop link (e.g., the first hop established at 520 and for the RRC reconfiguration 540). In such arrangements, an indication is provided in the PC5-RRC message that the source ID used for the E2E unicast link is the same as the per-hop UE ID used for each hop link (e.g., the first hop) rather than the ID of the source UE 501 for the E2E unicast link. In some arrangements, the source ID used for the E2E link (established at 560) can be different from the per-hop UE ID used for the first hop. In this case, the source UE 501 provides the per-hop UE ID in the MAC header and provides the source ID to the relay UE 502 in the PC5-RRC message (e.g., the first RRC message).

[0064] At 550, the relay UE 502 includes the source ID in a second RRC message (e.g., the RRC reconfiguration SL message or the RRCReconfigurationSidelink message) and sends the second RRC message to the target UE 503. The second RRC message includes the source ID that the relay UE 502 received from the source UE 501 in the first RRC message, which can be the same as or different from the per-hop UE ID. In some examples, the relay UE 502 includes the user information ID of the source UE 501 in the second RRC message to identify the source UE 501 in addition to the source ID.

[0065] In response to receiving the second RRC message including the source ID of the source UE 501 from the relay UE 502, the target UE 503 allocates its ID, referred to as the target ID, which is used for the E2E unicast link (e.g., established at 560). At 550, the target UE 503 includes the target ID in a third RRC message (e.g., the RRC reconfiguration SL message or the RRCReconfigurationSidelink message) and sends the third RRC message to the relay UE 502.

[0066] In some arrangements, the target ID used to identify the target UE 503 for an E2E unicast link can be the same as the per-hop UE ID used to identify the target UE 503 for per-hop links (e.g., the second hop established at 530 and for RRC reconfiguration 550). In such arrangements, an indication is provided in the PC5-RRC message that the target ID used for the E2E unicast link is the same as the per-hop UE ID used for per-hop links (e.g., the second hop) rather than the ID of the target UE 501 for the E2E unicast link. In some arrangements, the target ID used for the E2E link (established at 560) can be different from the per-hop UE ID used for the second hop, in which case the target UE 501 provides the per-hop UE ID in the MAC header and provides the target ID to the relay UE 502 in the PC5-RRC message (e.g., the third RRC message).

[0067] At 540, the target UE 502 includes the target ID in the fourth RRC message and sends the fourth RRC message to the source UE 501. The fourth RRC message includes the target ID that the relay UE 502 received from the target UE 503 in the third RRC message, which can be the same as or different from the per-hop UE ID. In some examples, the relay UE 502 includes the user information ID of the target UE 503 in the fourth RRC message to identify the target UE 501 in addition to the source ID.

[0068] In some arrangements, in method 400a, the source ID is provided using the first RRC reconfiguration message (e.g., the first RRC reconfiguration SL message) received by the relay UE from the source UE and the second RRC reconfiguration message (e.g., the first RRC reconfiguration SL message) sent by the relay UE to the target UE.

[0069] In some arrangements, in method 400a, providing the source ID to the target UE at 410 includes: the relay UE receiving, via a first link (first hop) between the source UE and the relay UE, a first RRC message from the source UE, the first RRC message including one of: a source ID (a source ID different from the ID used to identify the source UE for the first link (e.g., the per-hop UE ID)), or an indication that the source ID for the E2E unicast link is the same as the ID used to identify the source device for the first link. The ID used to identify the source UE for the first link is included in the MAC header of the first link. The method 400a further includes: the relay UE sending, via a second link (second hop) between the relay UE and the target UE, a second RRC message including the source ID to the target UE.

[0070] In some arrangements, the second RRC message further includes a user information ID of the source UE different from the source ID and an ID used to identify the source UE for the first link. The user information ID corresponds to or maps to the source ID. The user information ID indicates the source UE to which the source ID belongs. In an example where both a first source UE and a second source UE establish an E2E link with a target UE, the different user information IDs of the first source UE and the second source UE can be used by the target UE to identify the source ID as belonging to their respective user information IDs.

[0071] In some arrangements, in method 400a, providing the target ID to the source UE at 420 includes: the relay UE receiving a third RRC message from the target UE via a second link (e.g., second hop) between the target UE and the relay UE. The third RRC message includes one of the following: a target ID used to identify the target device for the second link (the target ID is different from an ID such as a per-hop UE ID) or an indication indicating that the target ID for the E2E unicast link is the same as the ID used to identify the target UE for the second link. The ID used to identify the target UE for the first link is included in the MAC header of the first link. Method 400a further includes the relay UE sending a fourth RRC message including the target ID to the source UE via a first link (first hop) between the relay UE and the source UE.

[0072] In some arrangements, the fourth RRC message further includes a user information ID of the target UE different from the target ID and an ID used to identify the target UE for the first link. The user information ID corresponds to or maps to the target ID. The user information ID indicates the target UE to which the target ID belongs. In an example where both a first target UE and a second target UE establish an E2E link with the source UE, the different user information IDs of the first target UE and the second target UE can be used by the source UE to identify the source ID as belonging to their respective user information IDs.

[0073] Thus, the source UE 501 can include its L2 ID (for the E2E PC5 link) or an indication (indicating that the L2 ID used for the E2E PC5 link is the same as the L2 ID used for the per-hop PC5 link) in each-hop PC5-S or PC5-RRC message, and the each-hop PC5-S or PC5-RRC message is sent to the relay UE 502 in the first hop. The relay UE 502 includes the L2 ID of the source UE 501 in the each-hop PC5-S or PC5-RRC message, and the each-hop PC5-S or PC5-RRC message is sent to the target UE 503 in the second hop.

[0074] In an example where a PC5-RRC message is used, the user information ID of the source UE 501 is also included to identify the source UE 501. Similarly, the target UE 503 includes its L2 ID or indication in each hop of the PC5-S or PC5-RRC message sent to the relay UE 501. The relay UE 502 includes the L2 ID of the target UE 503 in each hop of the PC5-S or PC5-RRC message (which includes the user information ID of the target UE) sent to the source UE.

[0075] Figure 6 FIG. is a diagram illustrating an example method 600 for transmitting UE IDs in an E2E link between a source UE 601 and a target UE 603 according to various arrangements. Each of the UEs 601, 602a, 602b, and 603 can be a UE such as UE 204. Figure 6 For a multi-hop scenario where there are two or more U2U relay UEs 602a and 602b between the source UE 601 and the target UE 603.

[0076] At 610, the source UE 601 sends to the relay UE 602a a source ID (e.g., L2 ID) identifying the source UE 601 for the E2E link or an indication that the source ID is the same as the per-hop UE ID used for the first hop between the source UE 601 and the relay UE 602a. At 620, the relay UE 602a sends the source ID to the relay UE 602b via the second hop, in a PC5-S message or a PC5-RRC message. At 630, the relay UE 602b sends the source ID to the target UE 603 via the third hop, in a PC5-S message or a PC5-RRC message.

[0077] At 640, the target UE 603 sends to the relay UE 602b a target ID (e.g., L2 ID) identifying the target UE 603 for the E2E link or an indication that the target ID is the same as the per-hop UE ID used for the third hop between the target UE 603 and the relay UE 602b. At 650, the relay UE 602b sends the target ID to the relay UE 602a via the second hop, in a PC5-S message or a PC5-RRC message. At 660, the relay UE 602a sends the target ID to the source UE 601 via the first hop, in a PC5-S message or a PC5-RRC message.

[0078] In an example where a PC5-RRC message is used, the user information IDs of the source UE 601 and the target UE 603 are also included in the PC5-RRC message to identify the source UE 601 and the target UE 603, respectively.

[0079] Figure 7FIG. 700 is a diagram illustrating an example method for transmitting a UE ID in a first E2E link between a source UE 701 and a target UE 703a and a second E2E link between the source UE 701 and a target UE 703b according to various arrangements. Each of the UEs 701, 702a, 702b, 703a, and 703b may be a UE such as UE 204. Figure 7 For a multi-hop scenario in which there are at least one U2U relay UEs 702a and 702b between the source UE 701 and the target UEs 703a and 703b via two communication paths.

[0080] For example, the source UE 701 may communicate with the target UE 703a via a first communication path including a hop 710b between the source UE 701 and the relay UE 702a, a hop 720a between the relay UE 702a and the relay UE 702b, and a hop 730 between the relay UE 702b and the target UE 703a.

[0081] The source UE 701 may communicate with the target UE 703b via a second communication path including a hop 710b between the source UE 701 and the relay UE 702a and a hop 720b between the relay UE 702a and the target UE 703b to establish a second E2E link. To exchange the UE ID via the second communication path, the source UE 701 sends, in a PC5-S message or a PC5-RRC message, a source ID (e.g., an L2 ID) identifying the source UE 701 for the second E2E link, or an indication that the source ID is the same as each hop UE ID used for the hop 710b between the source UE 701 and the relay UE 702a, to the relay UE 702a. The relay UE 702a sends the source ID to the target UE 703b via the hop 720b, in a PC5-S message or a PC5-RRC message. The target UE 703b sends, in a PC5-S message or a PC5-RRC message, a target ID (e.g., an L2 ID) identifying the target UE 703b for the second E2E link, or an indication that the target ID is the same as each hop UE ID used for the hop 720b between the target UE 703b and the relay UE 702a, to the relay UE 702a. The relay UE 702a sends the target ID to the source UE 701 via the hop 710b, in a PC5-S message or a PC5-RRC message.

[0082] Considering that the L2 ID (e.g., source ID or destination ID) is assigned by the UEs (e.g., source UE 701 and destination UEs 703a and 703b) identified by the L2 ID, different UEs may be assigned the same L2 ID. In an example where the second communication path is established first, and UE 703b assigns a destination ID (e.g., IDx) for itself for the second E2E link between source UE 701 and destination UE 703b. When the first communication path is established subsequently, destination UE 703a may assign the same L2 ID (e.g., IDx) for itself for the first E2E link between source UE 701 and destination UE 703a. If IDx is used to identify both destination UEs 703a and 703b, when source UE 701 sends a data packet to the UE identified by IDx, source UE 701 includes IDx in the adaptation header, and relay UE 702a will not be able to determine whether to send the data packet to destination UE 703a or destination UE 703b.

[0083] In order to exchange the UE ID via the first communication path after the UE ID is exchanged via the first communication path, source UE 701 sends, in PC5-S or PC5-RRC, the source ID (e.g., L2 ID) identifying source UE 701 for the first E2E link, or an indication that the source ID is the same as the per-hop UE ID for hop 710a between source UE 701 and relay UE 702a, to relay UE 702a. Relay UE 702a sends the source ID to relay UE 702b via hop 720a, in a PC5-S message or a PC5-RRC message. Relay UE 702a sends the source ID to destination UE 703a via hop 730, in a PC5-S message or a PC5-RRC message.

[0084] Destination UE 703a sends, in a PC5-S message or a PC5-RRC message, the destination ID (e.g., L2 ID) identifying destination UE 703a for the first E2E link, or an indication that the destination ID is the same as the per-hop UE ID for hop 730 between destination UE 703a and relay UE 702b, to relay UE 702b. Relay UE 702a sends the destination ID to relay UE 702a via hop 720a, in a PC5-S message or a PC5-RRC message. Considering that the new destination ID is the same as another destination UE 703b that has been in use to identify a previously established communication link or an E2E unicast link, relay UE 702 may detect an ID conflict.

[0085] In some examples, to avoid such L2 ID conflicts, relay UE 702a assigns a new target ID to target UE 703a and provides the new target ID for target UE 703a to source UE 701 (via hop 710a and using a PC5-S message or a PC5-RRC message) and any upstream or downstream relay UEs, such as relay UE 702b (via hop 720a and using a PC5-S message or a PC5-RRC message). Relay UE 702a maintains a mapping (e.g., a mapping table) of the original target ID (the target ID assigned by target UE 703a itself) and the new target ID in a memory (e.g., UE memory module 234).

[0086] In some arrangements, method 400a further includes, in response to determining that the original target ID of a target UE is currently being used by another target UE for another E2E unicast link, the relay UE assigning a target ID (a new target ID) to the target UE, storing in a memory a mapping of the original target ID for the target UE to the target ID for the target UE, and sending the target ID to the source UE.

[0087] In response to relay UE 702a receiving a data packet from source UE 701 that has the new target ID for target UE 703a in the adaptation header, relay UE 702a uses the new target ID in the mapping table to look up the original target ID and replaces the new target ID with the original target ID of target UE 703a in the adaptation header. Relay UE 702a sends the data packet with the original target ID of target UE 703a in the adaptation header to relay UE 702b, and this relay UE 702b forwards the data packet to target UE 703a.

[0088] In some arrangements, method 400a further includes the relay UE receiving, from the source UE (directly or via a relay UE), a data packet having a target identified by the target ID of the target UE (in the adaptation header), the relay UE using the mapping to determine the original target ID corresponding to the target ID, and the relay UE sending the data packet having a target identified by the original target ID in the adaptation header to the target UE (directly or via a relay UE).

[0089] In response to relay UE 702a receiving a data packet from relay UE 702b that has the original target ID (identifying that the source of the data packet is target UE 703a) in the adaptation header, relay UE 702a uses the original target ID in the mapping table to look up the new target ID, replaces the original target ID with the new target ID in the adaptation header, and sends the data packet to source UE 701. Source UE 701 can identify that the data packet is from target UE 703a (based on the new target ID) based on the new target ID.

[0090] In some arrangements, method 400a further includes a relay UE receiving, from a target UE (directly or via the relay UE), a data packet having a source identified by an original target ID (in an adaptation header), the relay UE using a mapping to determine a target ID corresponding to the original target ID, and the relay UE sending the data packet having a source identified by the target ID in the adaptation header to the source UE (directly or via the relay UE).

[0091] In some arrangements, the relay UE 702a notifies the new target ID to the relay UE 702b and / or the target UE 703a (e.g., via at least one PC5-S message or at least one PC5-RRC message). In some arrangements, method 400a further includes, in response to the allocation of the target ID, the relay UE (e.g., the relay UE 702a) directly sending the new target ID of the target UE to the target UE (e.g., the target UE 703a) by sending at least one PC5-S message or at least one PC5-RRC message to the target UE, or sending the new target ID of the target UE to the target UE (e.g., the target UE 703a) via at least one relay UE (e.g., the relay UE 702b). In some arrangements, method 400a further includes, in response to the allocation of the target ID, the relay UE (e.g., the relay UE 702a) directly sending the new target ID of the target UE to the source UE (e.g., the source UE 701) by sending at least one PC5-S message or at least one PC5-RRC message to the source UE, or sending the new target ID of the target UE to the source UE (e.g., the source UE 701) via at least one relay UE. In some arrangements, method 400a further includes, in response to the allocation of the target ID, the relay UE (e.g., the relay UE 702a) directly sending the new target ID of the target UE to another relay UE (e.g., the relay UE 702b) by sending at least one PC5-S message or at least one PC5-RRC message to the relay UE, or sending the new target ID of the target UE to another relay UE (e.g., the relay UE 702b) via at least one other relay UE.

[0092] In some arrangements, to avoid such L2 ID conflicts, the relay UE 702a notifies the target UE 703a of the ID conflict (e.g., via the relay UE 702b via at least one PC5-S message or at least one PC5-RRC message). The target UE 703a allocates a new target ID and notifies the new target ID to at least one of the relay UE 702b, the relay UE 702a (via the relay UE 702b), or the source UE 701 (via the relay UEs 702a and 702b) via at least one PC5-S message or at least one PC5-RRC message.

[0093] In some arrangements, method 400a further includes, in response to determining that the original target ID of the target UE is currently being used by another target UE for another E2E unicast link, the relay UE sending (either directly or via the relay UE) a message to the target UE notifying the target UE that the original target ID of the target UE is currently being used by another target UE. The relay UE receives from the target UE the target ID of the target UE (e.g., a new target ID). As described, the source ID is the L2 ID of the source UE, and the target ID is the L2 ID of the target UE.

[0094] Figure 8 FIG. is a diagram illustrating an example method 800 for transmitting UE IDs in an E2E link between a first UE 801 and a second UE 803 according to various arrangements. Each of the first UE 801 and the second UE 803 can be a source UE or a target UE as described.

[0095] In some arrangements, the first UE 801 assigns IDx1 to itself and sends IDx1 to the first relay UE 802a. The first relay UE 802a checks whether IDx1 is already being used by another remote UE in another path through the first relay UE 802a / for another remote UE in another path through the first relay UE 802a. If not, the first relay UE 802a sends the IDx1 of the first UE 801 to the second relay UE 802b. The second relay UE 802b checks whether IDx1 is already being used by another remote UE in another path through the second relay UE 802b / for another remote UE in another path through the second relay UE 802b. If so, the second relay UE 802b assigns a new IDx2 to the first UE 801 and notifies the first relay UE 802a and its next-hop node (e.g., the third relay UE), and so on. The penultimate nth relay UE 802n assigns a new IDxn to the first UE 801 and notifies the (n - 1)th relay UE and the second UE 803. The IDx2 to IDxn assigned to the first UE 801 by the relay UEs 802a - 802n are in the same format as IDx1, e.g., a 24-bit L2 ID.

[0096] When the first UE 801 sends data to the second UE 803 via at least one relay UE 802a - 802n, the first UE 801 uses IDx1 as the source ID in the adaptation header and sends it to the first relay UE 802a. When the first relay UE 802a forwards the data packet of the first UE 801 to the next - hop node (the second relay UE 802b), the first relay UE 802a replaces the source ID with IDx2, which is assigned by the next - hop node (the second relay UE 802b) for the first UE 801. Alternatively, the first relay UE 802a may not replace the source ID (keep IDx1 in the adaptation header), and the second relay UE 802b may identify that the packet with IDx1 from the first relay UE 802a is for the first UE 801 based on the stored ID mapping information. When the second relay UE 802b forwards the data packet of the first UE 801 to the next - hop node (e.g., the third relay UE), the second relay UE 802b replaces the source ID with the ID assigned by the next - hop node or IDx2 assigned by itself. When the nth relay UE 702n is assigned to forward the data packet of the remote first UE 801 to the second UE 803, the nth relay UE 702n replaces the source ID with IDxn assigned by it to the first UE 801.

[0097] When the second UE 803 sends data to the first UE 801 via at least one relay UE, the second UE 803 uses IDxn assigned by the next - hop (relay UE N) as the target UE ID in the adaptation header and sends the data packet to the relay UE N. When the second relay UE 802b forwards the data packet (from the second UE 803 to the first UE 801) to the first relay UE 802a, the second relay UE 802b replaces the target UE ID field with IDx1 from the next - hop (the first relay UE 802a). Then the first relay UE 802a forwards the data packet to the first UE 801 without replacing the target UE ID field in the adaptation header. Alternatively, the second relay UE 802b uses IDx2 in the adaptation header as the target UE ID to forward the data packet to the first relay UE 802a. When the first relay UE 802a receives the packet, it identifies that the target of the packet is the first UE 801 and replaces the target UE ID field with IDx1 when forwarding the packet to the first UE 801.

[0098] In some arrangements, the ID that can be mapped to the source UE or the target UE used in the adaptation header can be a local ID. This local ID can be exchanged before the E2E PC5 unicast link is established.

[0099] In some arrangements, the local ID for the source UE or the target UE can be assigned by the relay UE via a PC5-S or PC5-RRC message. The local ID is unique within the scope of the relay UE, which can be 8 bits or other bits. As discussed above, if a PC5-RRC message is used, when the relay UE notifies the source UE of the assigned local ID of the target UE, the user information ID or L2 ID of the target UE is also included to identify the target UE. If a PC5-RRC message is used, when the relay UE notifies the target UE of the assigned local ID of the source UE, the user information ID or L2 ID of the target UE is also included to identify the target UE.

[0100] In a multi-hop scenario, such as Figure 8 shown, the relay UE 802a assigns the local ID IDx1 to the first UE 801, assigns IDy1 to the second UE 803, and notifies the assigned local ID to the first UE 801 and the relay UE 802b. Then the relay UE 802b can re-assign the local IDs x2 and y2 to the UE pair (e.g., re-assign IDx2 to the first UE 801 and re-assign IDy2 to the second UE 803) and notify the assigned local IDs to the relay UE 802a and the next downstream UE (not shown), and so on. The penultimate nth relay UE 802n can re-assign the local IDs xn and yn to the UE pair (e.g., re-assign IDxn to the first UE 801 and re-assign IDyn to the second UE 803) and notify the assigned IDs to the (n - 1)th relay UE and the second UE 803.

[0101] In some arrangements, method 400a further includes: determining, by the relay UE, a first local source ID for the source UE; sending, by the relay UE, the first local source ID to at least one of the upstream UE or the downstream UE using at least one first PC5-S message or at least one first RRC message; determining, by the relay UE, a first local target ID for the target UE; and sending, by the relay UE, the first local target ID to at least one of the upstream UE or the downstream UE using at least one second PC5-S message or at least one second RRC message. The upstream UE includes the source UE or an upstream relay UE. The downstream UE includes the target UE or a downstream relay UE.

[0102] In some examples, the first RRC message further includes the user information ID or L2 ID of the source UE and the ID used to identify the source radio UE. The user information ID indicates the source UE to which the source ID belongs. In some examples, the second RRC message further includes the user information ID or L2 ID of the target UE and the ID used to identify the target UE. The user information ID indicates the target UE to which the target ID belongs. In an example where both the first source UE and the second source UE establish an E2E link with the target UE, different user information IDs of the first source UE and the second source UE can be used by the target UE to identify the source ID as belonging to their respective user information IDs.

[0103] The first UE 801 sends a data packet to the second UE 803. The first UE 801 includes local IDs (e.g., IDx1, IDy1) assigned by the next hop (e.g., relay UE 802a) as the source ID and the target ID in the adaptation header for the data packet. In response to receiving the data packet, the relay UE 802a replaces the adaptation header with local IDs (IDx2, IDy2) assigned by the relay UE 802b and forwards the data packet with the replaced local IDs to the next hop node, etc. The (n - 1)th relay UE replaces the adaptation header with local IDs (IDxn, IDyn) assigned by the next hop node (e.g., the nth relay UE 802n) and forwards the data packet to the nth relay UE 802n. The nth relay UE 802n recognizes that it is the last relay UE and forwards the packet (without changing the adaptation header) to the second UE 803. In some arrangements, the source ID is not included in the adaptation header of the first hop (between the first UE 801 and the relay UE 802a). In some arrangements, the target ID is not included in the adaptation header of the last hop (between the relay UE 802n and the second UE 803).

[0104] In some arrangements, method 400a further includes: receiving, by the relay UE, a data packet with a target identified by a first local target ID (in the adaptation header) of the target UE from an upstream relay UE; determining, by the relay UE, a second local target ID corresponding to the first local target ID (the second local target ID is assigned by a downstream relay UE); and sending, by the relay UE, a data packet with a target identified by the second local target ID (in the adaptation header) to the downstream relay UE. In some arrangements, method 400a further includes receiving, by the relay UE, a data packet with a source identified by a first local source ID (in the adaptation header) of the source UE from an upstream relay UE; determining, by the relay UE, a second local source ID corresponding to the first local source ID (the second local source ID is determined by a downstream relay UE); and sending, by the relay UE, a data packet with a source identified by the second local source ID (in the adaptation header) to the downstream relay UE.

[0105] The second UE 803 sends a data packet to the first UE 801. The second UE 803 includes, in an adaptation header for the data packet, local IDs (e.g., IDyn, IDxn) assigned by a next hop (e.g., relay UE 802n) as the source ID and the destination ID. In response to receiving the data packet, the relay UE 802n replaces the adaptation header with local IDs (IDyn-1, IDxn-1) assigned by the relay UE 802n-1 and forwards the data packet with the replaced local IDs to the next hop node, etc. The relay UE 802b replaces the adaptation header with local IDs (IDy1, IDx1) assigned by the next hop node (e.g., relay UE 802a) and forwards the data packet to the relay UE 802a. The relay UE 802a identifies itself as the last relay UE and forwards the packet (without changing the adaptation header) to the first UE 801. In some arrangements, the destination ID is not included in the adaptation header of the first hop (between the second UE 803 and the relay UE 802n). In some arrangements, the source ID is not included in the adaptation header of the last hop (between the relay UE 802a and the first UE 801).

[0106] In some arrangements, method 400a further includes: the relay UE receiving, from a downstream relay UE, a data packet having a source identified by a first local destination ID of a target UE in an adaptation header. The first local destination ID is assigned by the relay UE. The downstream relay UE determines a first local destination ID corresponding to a second local destination ID. The second local destination ID is assigned by the downstream relay UE. The method 400a further includes the relay UE sending, to an upstream relay UE, a data packet having a source identified by the first local destination ID in the adaptation header. In some arrangements, method 400a further includes the relay UE receiving, from a downstream relay UE, a data packet having a target identified by a first local source ID of a source UE in an adaptation header. The first local source ID is assigned by the relay UE. The downstream relay UE determines a first local source ID corresponding to a second local source ID. The second local source ID is assigned by the downstream relay UE. The method 400a further includes: the relay UE sending, to an upstream relay UE, a data packet having a target identified by the first local source ID in the adaptation header.

[0107] In some arrangements, the local ID of each remote UE is assigned by the UE itself. The local ID of the source UE is assigned by the source UE itself. The local ID of the target UE is assigned by the target UE itself. ID assignment, ID avoidance, and adaptation header replacement during data forwarding are effectively the same as the L2 ID described herein.

[0108] In some arrangements, the local ID of the source UE is assigned by the source UE per target UE. For example, for a target UE, the source UE assigns ID1 to itself, and for another target UE, the source UE assigns ID2 to itself. The source UE notifies the assigned ID to the target UE and the intermediate relay UE. In other words, each UE assigns a local ID to itself for a specific U2U relay communication (E2E PC5 link / source-target pair). In some arrangements, in method 400a, the source UE assigns a first source ID. The relay UE assigns a second source ID in response to determining that the first source ID is used by a UE of a first existing communication path. The target UE assigns a first target ID. The UE assigns a second target ID in response to determining that the first target ID is used by a UE of a second existing communication path. In some arrangements, the first source ID includes the L2 ID or local ID of the source UE. The second source ID includes the L2 ID or local ID of the source UE. The first target ID includes the L2 ID or local ID of the target UE. The second target ID includes the L2 ID or local ID of the target UE.

[0109] Figure 9 FIG. is a diagram illustrating an example method 900 for transmitting a UE ID in an E2E link between a first UE 901 and a second UE 903 according to various arrangements. Each of the first UE 901 and the second UE 903 can be a source UE or a target UE as described.

[0110] In some arrangements, the first UE 901 assigns IDx to itself and sends IDx to the first relay UE 902a (e.g., using a PC5-S message or an RRC message). The first relay UE 902a checks whether IDx has been used by another remote UE in another path through the first relay UE 902a / is used for another remote UE in another path through the first relay UE 902a. If not, the first relay UE 902a sends IDx to the second relay UE 902b (e.g., using a PC5-S message or an RRC message). If so, the first relay UE 902a assigns a new IDx1 to the first UE 801 and notifies the second relay UE 902b (e.g., using a PC5-S message or an RRC message). The second relay UE 902b checks whether IDx or IDx1 has been used by another remote UE in another path through the second relay UE 902b / is used for another remote UE in another path through the second relay UE 902b. If not, the second relay UE 902b sends IDx or IDx1 to the second UE 903 (e.g., using a PC5-S message or an RRC message). If so, the second relay UE 902b assigns a new IDx2 to the first UE 801 and notifies the second UE 903 (e.g., using a PC5-S message or an RRC message).

[0111] In some arrangements, the second UE 903 assigns IDy to itself and sends IDy to the second relay UE 902b (e.g., using a PC5-S message or an RRC message). The second relay UE 902b checks whether IDy has been used by another remote UE in another path through the second relay UE 902b / for another remote UE in another path through the second relay UE 902b. If not, the second relay UE 902b sends IDy to the first relay UE 902a (e.g., using a PC5-S message or an RRC message). If so, the second relay UE 902b assigns a new IDy1 to the second UE 803 and notifies the first relay UE 902a (e.g., using a PC5-S message or an RRC message). The first relay UE 902a checks whether IDy or IDy1 has been used by another remote UE in another path through the first relay UE 902a / for another remote UE in another path through the first relay UE 902a. If not, the first relay UE 902a sends IDy or IDy1 to the first UE 901. If so, the first relay UE 902a assigns a new IDy2 to the second UE 803 and notifies the first UE 901.

[0112] In an example where the first UE 901 assigns IDx to itself, the first relay UE 902a assigns IDx1 to the first UE 901, the second relay UE 902b assigns IDx2 to the first UE 901, and IDy can be used by UEs 901, 902a, 902b, and 903. The first UE 901 sends a data packet to the second UE 903. The first UE 901 includes an ID (e.g., IDx, IDy) in the adaptation header for the data packet as the source ID and the destination ID. In response to receiving the data packet, the relay UE 902a replaces the adaptation header with an ID (IDx1, IDy) and forwards the data packet with the replaced local ID to the next-hop node, the relay UE 902b. The relay UE 902b replaces the adaptation header with an ID (IDx2, IDy) and forwards the data packet to the second UE 803.

[0113] In some arrangements, method 400a further includes: receiving, by a relay UE, a data packet having a destination identified by a first local destination ID of a target UE (determined by an upstream UE) in an adaptation header from the upstream UE (e.g., a source UE or an upstream relay UE); determining, by the relay UE, a second local destination ID corresponding to the first local destination ID (the second local destination ID is determined by the relay UE); and sending, by the relay UE, the data packet having the destination identified by the second local destination ID in the adaptation header to a downstream UE (e.g., the target UE or a downstream relay UE). In some arrangements, method 400a further includes: receiving, by a relay UE, a data packet having a source identified by a first local source ID of a source UE (determined by an upstream UE) in an adaptation header from the upstream UE (e.g., a source UE or an upstream relay UE); determining, by the relay UE, a second local source ID corresponding to the first local source ID (the second local source ID is determined by the relay UE); and sending, by the relay UE, the data packet having the destination identified by the second local source ID in the adaptation header to a downstream UE (e.g., the target UE or a downstream relay UE).

[0114] In an example where the first UE 901 assigns IDx to itself, the first relay UE 902a assigns IDx1 to the first UE 901, the second relay UE 902b assigns IDx2 to the first UE 901, and IDy can be used by UEs 901, 902a, 902b, and 903. The second UE 903 sends a data packet to the first UE 901, and the second UE 903 includes an ID (e.g., IDy, IDx2) in the adaptation header for the data packet as the source ID and the destination ID. In response to receiving the data packet, the relay UE 802b replaces the adaptation header with IDs (IDy, IDx1) and forwards the data packet with the replaced local IDs to the next-hop node, the relay UE 902a. The relay UE 902a replaces the adaptation header with local IDs (IDy, IDx) and forwards the data packet to the first UE 901.

[0115] In some arrangements, method 400a further includes: receiving, by a relay UE, a data packet having a destination identified by a first local source ID of a source UE (determined by the downstream UE) in an adaptation header from a downstream UE (e.g., a target UE or a downstream relay UE); determining, by the relay UE, a second local source ID corresponding to the first local source ID (the second local source ID is determined by the relay UE); and sending, by the relay UE, the data packet having the destination identified by the second local source ID in the adaptation header to an upstream UE (e.g., a source UE or an upstream relay UE). In some arrangements, method 400a further includes: receiving, by a relay UE, a data packet having a source identified by a first local destination ID of a target UE (determined by the downstream UE) in an adaptation header from a downstream UE (e.g., a target UE or a downstream relay UE); determining, by the relay UE, a second local destination ID corresponding to the first local destination ID (the second local source ID is determined by the relay UE); and sending, by the relay UE, the data packet having the source identified by the second local destination ID in the adaptation header to an upstream UE (e.g., a source UE or an upstream relay UE).

[0116] In some arrangements, the ID that can be mapped to a source UE or a target UE used in the adaptation header can be a common ID or a link ID. The common ID or link ID is an ID representing a pair of a source UE and a target UE and can be exchanged before the establishment of an E2E PC5 unicast link.

[0117] Regarding Figure 8 , in some arrangements, the first UE 801 assigns IDx1 to the UE pair including UE 801 and 803, and sends IDx1 to the first relay UE 802a. The first relay UE 802a assigns a new IDx2 to the UE pair, and sends IDx2 to an upstream relay UE (relay UE 802a) and a downstream relay UE (relay UE 802b), and so on. The penultimate nth relay UE 802n assigns a new IDxn to the UE pair and notifies the (n - 1)th relay UE and the second UE 803. Considering that the common / link ID represents the source UE and target UE pair / PC5 unicast link between UE801 and 803, only one ID is included in the adaptation header (different from the case where the above two IDs are included in the adaptation header). When forwarding data, each node can replace the UE ID in the adaptation header with the ID assigned by the next-hop node, and forward the data packet to the next-hop node.

[0118] In some arrangements, method 400a further includes: determining, by a relay UE, a first common ID for a pair of a source UE and a target UE; sending the first common ID to at least one of an upstream UE or a downstream UE. The upstream UE includes a source UE or an upstream relay UE, and the downstream UE includes a target UE or a downstream relay UE.

[0119] In some arrangements, method 400a further includes: receiving, by a relay UE, a data packet having a destination identified by a first common ID from an upstream UE; determining, by the relay UE, a second common ID corresponding to the first common ID for a pair of a source UE and the destination UE (the second common ID is determined by a downstream UE); and sending, by the relay UE, a data packet having a destination identified by the second common ID to the downstream UE.

[0120] In some arrangements related to emergency services for UE-to-network (U2N) relay, emergency services are defined as services from citizens to authorities. The national authorities decide whether the network accepts emergency calls. When a UE enabled with 5G ProSe is not directly connected to the network for emergency services, the UE can attempt to obtain emergency services via 5G ProSe layer 2 or layer 3 U2N relay.

[0121] To support relay emergency services for U2N relay, the BS can indicate support for relay emergency services so that the relay UE can forward emergency services for a remote UE. Specifically, the BS includes an indication of support for relay emergency services for U2N relay in System Information Block 1 (SIB1). In some arrangements, a method includes sending, by the BS, an indication to a UE in SIB1 that indicates support for relay emergency services for U2N relay. The UE receives such an indication.

[0122] In response to receiving a Protocol Data Unit (PDU) session establishment / modification request for emergency services for a remote UE from the 5GC, the BS can select an appropriate relay UE (i.e., a relay UE that supports emergency service relay) to relay emergency services for the remote UE. To enable the BS to select a relay UE that supports emergency service relay, various factors can be considered. That is, the BS can select a relay UE for a plurality of UEs based on at least one of the factors described herein.

[0123] In some examples, the BS sends an indication indicating candidate relay UEs reported by the remote UE that support emergency service relay after receiving a PDU session establishment / modification request for emergency services for the remote UE from the 5GC. In some examples, the BS sends an indication indicating that the remote UE updates the SL relay measurement report.

[0124] In some examples, a new measurement report event is configured. An example event E includes that the PC5 link quality between the remote UE and a candidate relay UE that supports emergency service relay is higher than a threshold. The BS sends the new measurement report event to the remote UE.

[0125] In some examples, when a remote UE initiates the establishment of an emergency PDU session, the remote UE sends an updated SL measurement report to the BS, which includes candidate relay UEs that support emergency service relay and the PC5 link quality with the remote UE is higher than a threshold.

[0126] In some examples, the BS can send an indication to the remote UE, which indicates that the remote UE selects a relay UE. Then the remote UE can select a relay UE that supports emergency service relay by itself. The remote UE reports the selected relay UE to the BS.

[0127] In some examples, in order for the BS to select an appropriate relay UE for emergency service relay, the relay UE can indicate to the BS via the sidelinkUEInformation message or UE capability information or other RRC messages whether the relay UE supports relaying emergency services for the remote UE. In some arrangements, the BS receives an indication from the relay UE indicating whether the relay UE supports relaying emergency services for another UE.

[0128] In some examples where the relay UE is relaying emergency services for the remote UE, the relay UE has its own emergency services, and the relay UE can prioritize the establishment of its own emergency services and stop relaying the emergency services of the remote UE. In order to distinguish the relay UE's own emergency services and the relayed emergency services for the remote UE, a new establishment / resumption cause value can be introduced, which indicates relaying emergency services for the remote UE. In some arrangements, the UE sends an establishment / resumption cause value to the BS, which indicates relaying the emergency services for another UE or the emergency services for this UE.

[0129] In some arrangements, during the legacy Hanover (HO) process, after receiving the HO request confirmation from the target BS, the source BS can send a secondary node (SN) status transfer to the target BS and forward UL / DL data to the target BS. For DL data forwarding, the source BS can forward all downlink packet data convergence protocol (PDCP) SDUs whose SN corresponds to the PDCP PDUs that have not been confirmed by the UE.

[0130] For the case of i2d / i2i path switching between BSs, due to per-hop radio link control (RLC) in the original indirect path, the source BS can forward all DL data that has not been acknowledged by the relay UE to the target BS. That is, the source BS forwards DL data to the target BS based on the reception status of the relay UE rather than the remote UE. However, the reception status of the relay UE does not actually reflect the reception status of the remote UE. Considering that path switching can be triggered due to the deterioration of the PC5 link quality, packet loss occurring at the PC5 interface is likely due to poor PC5 link quality. There may be some DL packets buffered at the relay UE that have been RLC acknowledged by the relay UE to the source BS but have not been successfully transmitted to the remote UE via the PC5 hop. In this case, if legacy Xn data forwarding follows, the source BS will not forward such packets to the target BS. Even if the target BS obtains a PDCP status report from the remote UE, the target BS cannot retransmit such DL packets to the remote UE because the target BS has not received the DL packets from the source BS. Therefore, such DL packets will be missing at the remote UE after the remote UE successfully switches to the target BS.

[0131] In some arrangements, to ensure lossless DL delivery during i2d / i2i path switching between BSs, enhanced data forwarding from the source BS to the target BS can be provided upon each target BS request (based on the legacy PDCP status report). Specifically, the target BS relies on the legacy PDCP status report sent from the remote UE after path switching. The target BS requests the source BS to additionally forward the missing DL packets that have not been forwarded earlier after receiving the PDCP status report.

[0132] In some arrangements, to ensure lossless DL delivery during i2d / i2i path switching between BSs, the PDCP status report is sent from the remote UE to the source BS. Specifically, the source BS triggers the remote UE to send a PDCP status report to the source BS before the source BS performs SN status transfer to the target BS. The source BS can then forward the buffered data to the target BS based on the received PDCP status report, and the target BS can retransmit the PDCP data PDUs to the remote UE as needed.

[0133] In some arrangements, to ensure lossless DL delivery during i2d / i2i path switching between BSs, proactive data forwarding from the source BS to the target BS can be provided. The source BS forwards all buffered data to the target BS without receiving a request from the target BS.

[0134] In some arrangements, in response to receiving a HO request from a source BS to request a path switch from an indirect link to a direct link or from an indirect link to an indirect link, in the HO request confirmation message, the target BS instructs the source BS to perform legacy Xn data forwarding (e.g., forwarding all DL packets that have not been acknowledged by the relaying UE).

[0135] In some arrangements, in response to receiving a HO request from a source BS to request a path switch from an indirect link to a direct link or from an indirect link to an indirect link, in the HO request confirmation message, the target BS instructs the source BS to perform proactive Xn data forwarding (e.g., forwarding DL packets to the target BS based on PDCP status reports from a remote UE (which have not been acknowledged), or forwarding all buffered DL data to the target BS).

[0136] The source BS then performs Xn data forwarding based on the indication of the target BS.

[0137] In some arrangements, the source BS can perform legacy Xn data forwarding or proactive xn data forwarding until it is achieved.

[0138] If legacy Xn data forwarding is performed, after receiving a PDCP status report from a remote UE after the path switch, the target BS can request the source BS to additionally forward missing DL packets (packets that have not been acknowledged by the remote UE in the PDCP status report and have not been forwarded by the source BS to the target BS).

[0139] Although various arrangements of the present solution have been described above, it should be understood that they are presented by way of example and not limitation. Similarly, the various figures may depict exemplary architectures or configurations, and these examples are provided to enable a person of ordinary skill in the art to understand the exemplary features and functions of the present solution. However, these persons will understand that the solution is not limited to the exemplary architectures or configurations shown, but can be implemented using various alternative architectures and configurations. In addition, as will be understood by a person of ordinary skill in the art, one or more features of some arrangements can be combined with one or more features of another arrangement described herein. Therefore, the breadth and scope of the present disclosure should not be limited by any of the above-described illustrative arrangements.

[0140] It should also be understood that any reference to elements using names such as "first", "second", etc. generally does not limit the number or order of these elements. Instead, these names can be used herein as a convenient means of distinguishing between two or more elements or instances of elements. Thus, the reference to a first and a second element does not mean that only two elements can be used, or that the first element must precede the second element in some way.

[0141] In addition, those of ordinary skill in the art will understand that various different technologies and any of the technologies can be used to represent information and signals. For example, the data, instructions, commands, information, signals, bits, and symbols that may be referred to in the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0142] Those of ordinary skill in the art will further understand that any of the various illustrative logical blocks, modules, processors, devices, circuits, methods, and functions described in connection with the aspects disclosed herein can be implemented by electronic hardware (e.g., digital implementation, analog implementation, or a combination of both), firmware, various forms of programs or design code containing instructions (which may be referred to herein for convenience as "software" or "software modules"), or any combination of these technologies. To clearly illustrate this interchangeability of hardware, firmware, and software, the various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether this functionality is implemented as hardware, firmware, or software, or a combination of these technologies, depends on the specific application and design constraints imposed on the overall system. Those of ordinary skill in the art 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 the present disclosure.

[0143] In addition, those of ordinary skill in the art will understand that the various illustrative logical blocks, modules, devices, components, and circuits described herein can be implemented within or performed by 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 devices, or any combination thereof. The logical blocks, modules, and circuits can also include antennas and / or transceivers to communicate with various components within a network or within a device. The general-purpose processor can be a microprocessor, but in an alternative, the processor can be any conventional processor, controller, or state machine. The processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other suitable configuration to perform the functions described herein.

[0144] If implemented in software, the functionality can be stored as one or more instructions or code on a computer-readable medium. Accordingly, the steps of the method or algorithm disclosed herein can be implemented as software stored on a computer-readable medium. Computer-readable media includes computer storage media and communication media, where communication media includes any medium that can transfer a computer program or code from one place to another. The storage media can be any available media that can be 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, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired program code in the form of instructions or data structures and that can be accessed by a computer.

[0145] In this document, the term “module” as used herein refers to software, firmware, hardware, and any combination of these elements for performing the associated functions described herein. Additionally, for discussion purposes, various modules are described as discrete modules; however, as will be apparent to one of ordinary skill in the art, two or more modules can be combined to form a single module that performs the associated functions in accordance with the arrangement of the present solution.

[0146] Furthermore, in the arrangement of the present solution, a memory or other storage, as well as communication components, can be employed. It should be understood that, for clarity, the above description has described the arrangement of the present solution with reference to different functional units and processors. However, it is apparent that any suitable functional distribution between different functional units, processing logic elements, or domains can be used without departing from the present solution. For example, functions illustrated as being performed by separate processing logic elements or controllers can be performed by the same processing logic element or controller. Accordingly, the reference to specific functional units is only a reference to the appropriate means for providing the described functionality and not an indication of a strict logical or physical structure or organization.

[0147] Various modifications to the embodiments described in this disclosure will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the scope of the disclosure. Thus, the disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the novel features and principles disclosed herein, as set forth in the following claims.

Claims

1. A wireless communication method, comprising: providing, by a relay wireless communication device, a source ID of a source wireless communication device to a target wireless communication device for an end-to-end (E2E) unicast link between the source wireless communication device and the target wireless communication device; and providing, by the relay wireless communication device, a target ID of the target wireless communication device to the source wireless communication device for the E2E unicast link.

2. The method according to claim 1, wherein The source ID is provided using a first PC5-S message received by the relay wireless communication device from the source wireless communication device and a second PC5-S message sent by the relay wireless communication device to the target wireless communication device.

3. The method according to claim 1, wherein Providing the source ID to the target wireless communication device includes: receiving, by the relay wireless communication device via a first link between the source wireless communication device and the relay wireless communication device, a first PC5-S message from the source wireless communication device, the first PC5-S message including one of the following: the source ID, wherein the source ID is different from an ID used to identify the source device for the first link; or an indication that the source ID for the E2E unicast link is the same as an ID used to identify the source wireless communication device for the first link; and sending, by the relay wireless communication device via a second link between the relay wireless communication device and the target wireless communication device, a second PC5-S message including the source ID to the target wireless communication device.

4. The method according to claim 1, wherein Providing the target ID to the source wireless communication device includes: receiving, by the relay wireless communication device via a second link between the target wireless communication device and the relay wireless communication device, a third PC5-S message from the target wireless communication device, the third PC5-S message including one of the following: the target ID, wherein the target ID is different from an ID used to identify the target device for the second link; or an indication that the target ID for the E2E unicast link is the same as an ID used to identify the target wireless communication device for the second link; and sending, by the relay wireless communication device via a first link between the relay wireless communication device and the source wireless communication device, a fourth PC5-S message including the target ID to the source wireless communication device.

5. The method according to claim 1, wherein The source ID is provided using a first radio resource control (RRC) reconfiguration message received by the relay wireless communication device from the source wireless communication device and a second RRC reconfiguration message sent by the relay wireless communication device to the target wireless communication device.

6. The method according to claim 1, wherein, Providing the source ID to the target wireless communication device includes: receiving, by the relay wireless communication device via a first link between the source wireless communication device and the relay wireless communication device, a first radio resource control (RRC) message from the source wireless communication device, the first RRC message including one of the following: The source ID, where the source ID is different from the ID used to identify the source wireless communication device for the first link; or An indication indicating that the source ID for the E2E unicast link is the same as the ID used to identify the source wireless communication device for the first link; and The relay wireless communication device sends a second RRC message including the source ID to the target wireless communication device via a second link between the relay wireless communication device and the target wireless communication device.

7. The method according to claim 1, wherein, Providing the target ID to the source wireless communication device includes:[[]] The relay wireless communication device receives a third radio resource control (RRC) message from the target wireless communication device via a second link between the target wireless communication device and the relay wireless communication device, and the third RRC message includes one of the following:[[]] The target ID, where the target ID is different from the ID used to identify the target wireless communication device for the second link; or An indication indicating that the target ID for the E2E unicast link is the same as the ID used to identify the target wireless communication device for the second link; and The relay wireless communication device sends a fourth RRC message including the target ID to the source wireless communication device via a first link between the relay wireless communication device and the source wireless communication device.

8. The method according to claims 6 and 7, wherein, The second RRC message further includes the user information ID of the source wireless communication device and the ID used to identify the source wireless communication device, where the fourth RRC message further includes the user information ID of the target wireless communication device and the ID used to identify the target wireless communication device.

9. The method according to claim 1, further comprising, in response to determining that the original target ID of the target wireless communication device is currently used by another target wireless communication device for another E2E unicast link:[[]] The relay wireless communication device allocates a target ID for the target wireless communication device; The relay wireless communication device stores a mapping from the original target ID of the target wireless communication device to the target ID of the target wireless communication device in a memory; and The relay wireless communication device sends the target ID to the source wireless communication device.

10. The method according to claim 9, further comprising:[[]] The relay wireless communication device receives a data packet of the target identified by the target ID of the target wireless communication device from the source wireless communication device; The relay wireless communication device uses the mapping to determine the original target ID corresponding to the target ID; And The relay wireless communication device sends the data packet of the target identified by the original target ID to the target wireless communication device.

11. The method according to claim 9, further comprising at least one of the following:[[]] In response to allocating the target ID, the relay wireless communication device sends the target ID of the target wireless communication device to the target wireless communication device; In response to the assignment of the target ID, the relay wireless communication device sends the target ID of the target wireless communication device to the source wireless communication device; or In response to the assignment of the target ID, the relay wireless communication device sends the target ID of the target wireless communication device to another relay wireless communication device.

12. The method according to claim 9, further comprising: The relay wireless communication device receives, from the target wireless communication device, a data packet having a source identified by the original target ID of the target wireless communication device; The relay wireless communication device uses the mapping to determine the target ID corresponding to the original target ID; And The relay wireless communication device sends, to the source wireless communication device, a data packet having a source identified by the target ID.

13. The method according to claim 1, further comprising: In response to determining that the original target ID of the target wireless communication device is currently being used by another wireless communication device for another E2E unicast link, the relay wireless communication device sends a message to the target wireless communication device notifying the target wireless communication device that the original target ID of the target wireless communication device is currently being used by another target wireless communication device; And The relay wireless communication device receives the target ID of the target wireless communication device from the target wireless communication device.

14. The method according to claim 1, wherein The source ID includes the L2 ID or the local ID of the source wireless communication device; The target ID includes the L2 ID or the local ID of the target wireless communication device.

15. The method according to claim 1, further comprising: The relay wireless communication device determines a first local source ID for the source wireless communication device; The relay wireless communication device uses at least one first PC5-S message or at least one first radio resource control (RRC) message to send the first local source ID to at least one of an upstream wireless communication device or a downstream wireless communication device, wherein the upstream wireless communication device includes the source wireless communication device or an upstream relay wireless communication device, and the downstream wireless communication device includes the target wireless communication device or a downstream relay wireless communication device; The relay wireless communication device determines a first local target ID for the target wireless communication device; The relay wireless communication device uses at least one second PC5-S message or at least one second RRC message to send the first local target ID to at least one of the upstream wireless communication device or the downstream wireless communication device.

16. The method according to claim 15, wherein The first RRC message further includes the user information ID or the L2 ID of the source wireless communication device and an ID used to identify the source wireless communication device; and The second RRC message further includes the user information ID or the L2 ID of the target wireless communication device and an ID used to identify the target wireless communication device.

17. The method according to claim 15, further comprising The relay wireless communication device receives a data packet having a destination identified by the first local destination ID of the target wireless communication device from the upstream relay wireless communication device; The relay wireless communication device determines a second local destination ID corresponding to the first local destination ID, wherein The second local destination ID is assigned by the downstream relay wireless communication device; And The relay wireless communication device sends a data packet having a destination identified by the second local destination ID to the downstream relay wireless communication device.

18. The method according to claim 15, further comprising The relay wireless communication device receives a data packet having a source identified by a first local target ID of the target wireless communication device from the downstream relay wireless communication device, wherein The first local destination ID is assigned by the relay wireless communication device, the downstream relay wireless communication device determines that the first local destination ID corresponds to the second local destination ID, and the second local destination ID is assigned by the downstream relay wireless communication device; And The relay wireless communication device sends a data packet having a source identified by the first local destination ID to the upstream relay wireless communication device.

19. The method according to claim 1, wherein The source wireless communication device assigns a first source ID; In response to determining that the first source ID is used by a wireless communication device on a first existing communication path, the relay wireless communication device assigns a second source ID; The target wireless communication device assigns a first target ID; and In response to determining that the first target ID is used by a wireless communication device on a second existing communication path, the relay wireless communication device assigns a second target ID.

20. The method according to claim 1, further comprising: The relay wireless communication device determines a first common ID for a pair of the source wireless communication device and the target wireless communication device; The relay wireless communication device sends the first common ID to at least one of an upstream wireless communication device or a downstream wireless communication device, wherein the upstream wireless communication device includes the source wireless communication device or an upstream relay wireless communication device, and the downstream wireless communication device includes the target wireless communication device or a downstream relay wireless communication device.

21. The method according to claim 20, further comprising The relay wireless communication device receives a data packet identified by the first common ID from the upstream wireless communication device; The second common ID for the pair of the source wireless communication device and the target wireless communication device corresponding to the first common ID is determined by the relay wireless communication device, wherein The second common ID is determined by the downstream wireless communication device; And The relay wireless communication device sends a data packet identified by the second common ID to the downstream wireless communication device.

22. A wireless communication device, comprising at least one processor and a memory, wherein, The at least one processor is configured to read code from the memory and implement the method described in claim 1.

23. A computer program product comprising computer-readable program medium code stored thereon, the code causing the at least one processor to implement the method described in claim 1 when executed by the at least one processor.

24. A wireless communication method, comprising: The source wireless communication device determines a source ID of the source wireless communication device for an end-to-end (E2E) unicast link between the source wireless communication device and a target wireless communication device; The source ID is sent from the source wireless communication device to the relay wireless communication device via a PC5-S message or a Radio Resource Control (RRC) message; and The source wireless communication device receives the target ID of the target wireless communication device from the relay wireless communication device for the E2E unicast link.

25. A wireless communication device, comprising at least one processor and a memory, wherein, The at least one processor is configured to read the code from the memory and implement the method described in claim 24.

26. A computer program product comprising computer-readable program medium code stored thereon, the code causing the at least one processor to implement the method described in claim 24 when executed by the at least one processor.

27. A wireless communication method comprising: Determining, by a target wireless communication device, a target ID of the target wireless communication device for an end-to-end (E2E) unicast link between a source wireless communication device and the target wireless communication device; Sending, by the target wireless communication device, the target ID to a relay wireless communication device via a PC5-S message or a Radio Resource Control (RRC) message; and Receiving, by the target wireless communication device, the source ID of the source wireless communication device from the relay wireless communication device for the E2E unicast link.

28. A wireless communication device, comprising at least one processor and a memory, wherein, The at least one processor is configured to read the code from the memory and implement the method described in claim 27.

29. A computer program product comprising computer-readable program medium code stored thereon, the code causing the at least one processor to implement the method described in claim 27 when executed by the at least one processor.

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