WO2025054927A1

WO2025054927A1 - Multi-hop sidelink relay method, user equipment and a base station

Info

Publication number: WO2025054927A1
Application number: PCT/CN2023/118928
Authority: WO
Inventors: Zhe Chen
Original assignee: Shenzhen TCL New Technology Co Ltd
Current assignee: Shenzhen TCL New Technology Co Ltd
Priority date: 2023-09-14
Filing date: 2023-09-14
Publication date: 2025-03-20
Anticipated expiration: 2026-03-14

Abstract

A multi-hop sidelink relay method. A base station serving a sidelink relay UE transmits a routing configuration in a downlink configuration message. The routing configuration comprises routing rules for path selection between paths of multi-hop sidelink relay, and the path selection is for routing one or more protocol data units (PDUs) over multi-hop sidelink relay. A sidelink relay UE receives a protocol data unit (PDU) with a sidelink relay adaption protocol (SRAP) header that includes downlink routing information for multi-hop sidelink relay and transmits the PDU according to uplink routing information of the PDU.

Description

MULTI-HOP SIDELINK RELAY METHOD, USER EQUIPMENT AND A BASE STATION

BACKGROUND OF DISCLOSURE

1. Field of Disclosure

The present disclosure relates to the field of communication systems, and more particularly, to a multi-hop sidelink relay method and user equipment (UE) .

2. Description of Related Art

3GPP one-hop sidelink relay is a technique that enables direct communication between two devices in which a sidelink relay node acts as a bridge between a source device and a destination device, relaying the data packets over the sidelink interface. The relay node can be either a dedicated device or a regular user equipment (UE) that participates in the relay operation voluntarily or upon request from the network. One-hop sidelink relay can be used to extend the coverage of cellular networks, improve the reliability of data transmission, and support low-latency applications. One-hop sidelink relay is based on the 3GPP standard for device-to-device (D2D) communication with 3GPP Release 17 or 18 protocols and procedures for establishing and maintaining sidelink connections.

Technical Problem

The 3GPP standards specify that sidelink (SL) relay is a feature that allows a remote UE to communicate with a gNB through another UE acting as a relay. However, this feature is limited to one hop only, meaning that the relay UE cannot forward the data to another relay UE.

Multi-hop sidelink relay was not introduced in the previous 3GPP Release 17 or 18 sidelink relay. If multi-hop sidelink relay is to be introduced, the relevant enhancements to sidelink relay are required.

Hence, a multi-hop sidelink relay method is desirable.

SUMMARY

An object of the present disclosure is to propose multi-hop sidelink relay method, user equipment (UE) , and a base station.

In a first aspect, an embodiment of the invention provides a multi-hop sidelink relay method for execution by a user equipment (UE) serving as a sidelink remote UE, comprising:

receiving a downlink protocol data unit (PDU) with a sidelink relay adaption protocol (SRAP) header that includes downlink routing information for multi-hop sidelink relay; and

transmitting an uplink PDU with an SRAP header that includes uplink routing information for multi-hop sidelink relay.

In a second aspect, an embodiment of the invention provides a user equipment (UE) comprising a processor configured to call and run a computer program stored in a memory, to cause a device in which the chip is installed to execute the disclosed method and any combination of embodiments of the disclosed method.

In a third aspect, an embodiment of the invention provides a multi-hop sidelink relay method for execution by a user equipment (UE) serving as a sidelink relay UE, comprising:

receiving a protocol data unit (PDU) with a sidelink relay adaption protocol (SRAP) header that includes downlink routing information for multi-hop sidelink relay; and

transmitting the PDU according to uplink routing information of the PDU.

In a fourth aspect, an embodiment of the invention provides a UE comprising a processor configured to call and run a computer program stored in a memory, to cause a device in which the chip is installed to execute the disclosed method and any combination of embodiments of the disclosed method.

In a fifth aspect, an embodiment of the invention provides a multi-hop sidelink relay method for execution by a base station, comprising:

transmitting a routing configuration in a downlink configuration message, wherein the routing configuration comprises routing rules for path selection between paths of multi-hop sidelink relay, and the path selection is for routing one or more protocol data units (PDUs) over multi-hop sidelink relay.

In a sixth aspect, an embodiment of the invention provides a base station comprising a processor configured to call and run a computer program stored in a memory, to cause a device in which the chip is installed to execute the disclosed method.

The disclosed method may be programmed as computer executable instructions stored in non-transitory computer readable medium. The non-transitory computer readable medium, when loaded to a computer, directs a processor of the computer to execute the disclosed method.

The non-transitory computer readable medium may comprise at least one from a group consisting of: a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a Read Only Memory, a Programmable Read Only Memory, an Erasable Programmable Read Only Memory, EPROM, an Electrically Erasable Programmable Read Only Memory and a Flash memory.

The disclosed method may be programmed as a computer program product, that causes a computer to execute the disclosed method.

The disclosed method may be programmed as a computer program, that causes a computer to execute the disclosed method.

Advantageous Effects

Multi-hop sidelink relay was not introduced in the previous 3GPP Release 17 or 18 sidelink relay. If multi-hop sidelink relay is to be introduced, the relevant enhancements to sidelink relay should be introduced. At least two aspects need enhancement, including the following:

(1) . Routing: In 3GPP Release 17 or 18, a sidelink relay only supports single hop routing. If multi-hop sidelink relay is introduced, it is imperative to enhance the routing method to enable multi-hop routing.

(2) . Bearer mapping enhancement: In 3GPP Release 17 or 18, bearer mapping for sidelink relay is performed at the Sidelink Relay Adaption Protocol (SRAP) layer, but the bearer ID at the SRAP layer only supports one-hop bearer mapping. Therefore, enhancements to the SRAP layer are required to support multi hop sidelink relay.

The technical effect of the disclosure includes enhancement to routing configuration, SRAP header and CBR reporting for multi-hop sidelink relay. The disclosure allows path selection between multiple paths in a multi-hop sidelink relay topology.

In some use cases, the disclosure enables multi-hop sidelink relay to improve the coverage and reliability of vehicle-to-everything (V2X) communication in scenarios where direct transmission is not feasible. Multi-hop sidelink relay allows vehicles to relay messages from other vehicles through intermediate nodes. This can enhance the performance of V2X applications such as cooperative awareness, collision avoidance, and platooning.

BRIEF DESCRIPTION OF DRAWINGS

In order to more clearly illustrate the embodiments of the present disclosure or related art, the following figures will be described in the embodiments are briefly introduced. It is obvious that the drawings are merely some embodiments of the present disclosure, a person having ordinary skill in this field may obtain other figures according to these figures without paying the premise.

FIG. 1 illustrates a schematic view showing a wireless communication system comprising a user equipment (UE) , a base station, and a network entity.

FIG. 2 illustrates a schematic view showing an example of sidelink relay with multiple bearers (BR1, BR2 and BR3) in hops.

FIG. 3 illustrates a schematic view showing a user-plane protocol stack for sidelink relay.

FIG. 4 illustrates a schematic view showing a user-plane protocol stack for sidelink relay.

FIG. 5 illustrates a schematic view showing examples of SRAP headers.

FIG. 6 illustrates a schematic view showing an embodiment the disclosed method.

FIG. 7 illustrates a schematic view showing another embodiment of the disclosed method.

FIG. 8 illustrates a schematic view showing an embodiment of the disclosed method using a routing configuration sent from a base station.

FIG. 9 illustrates a schematic view showing an example of multi-hop sidelink relay with multiple paths.

FIG. 10 illustrates a schematic view showing an example of CRB reporting.

FIG. 11 illustrates a schematic view showing another example of CRB reporting.

FIG. 12 illustrates a schematic view showing an example of multi-hop sidelink relay.

FIG. 13 illustrates a schematic view showing examples of SRAP headers with bearer mapping ID.

FIG. 14 illustrates a schematic view showing an example of multi-hop sidelink relay with a bearer configuration.

FIG. 15 illustrates a schematic view showing a system for wireless communication according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the disclosure are described in detail with the technical matters, structural features, achieved objects, and effects with reference to the accompanying drawings as follows. Specifically, the terminologies in the embodiments of the present disclosure are merely for describing the purpose of the certain embodiment, but not to limit the disclosure.

Abbreviations used in the description are listed in the following:

Table 1

The disclosure presents a novel approach to wireless communication, based on the concept of multi-hop sidelink relay. This disclosed method can relay data or signals over multiple hops. This enables better coverage in various environments.

Currently, no competitive technique is available. Integrated access and backhaul (IAB) serving as a relay for the network is developed for applications at a fixed location. IAB nodes are more stable than sidelink relays, which can move frequently. IAB nodes can also support mobility, but they rarely change their position. The functions of IAB, such as routing, bearer mapping and others, can work with a relatively static configuration. The sidelink relay is useful in scenarios where the mobility of remote UEs and relay UEs is much greater than that of network devices, such as base stations or access points. In such scenarios, more flexible routing configuration and bearer mapping configuration are required to ensure reliable and efficient data transmission.

In the description, an NG-RAN node may be one or more entities in a radio access network (RAN) , such as a gNB or base station.

With reference to FIG. 1, a telecommunication system including a UE 10a, a UE 10b, a base station (BS) 20a, and a network entity device 30 executes the disclosed method according to an embodiment of the present disclosure. FIG. 1 is shown for illustrative not limiting, and the system may comprise more UEs, BSs, and CN entities. Connections between devices and device components are shown as lines and arrows in the FIGs. The UE 10a may include a processor 11a, a memory 12a, and a transceiver 13a. The UE 10b may include a processor 11b, a memory 12b, and a transceiver 13b. The base station 20a may include a processor 21a, a memory 22a, and a transceiver 23a. The network entity device 30 may include a processor 31, a memory 32, and a transceiver 33. Each of the processors 11a, 11b, 21a, and 31 may be configured to implement proposed functions, procedures and/or methods described in the description. Layers of radio interface protocol may be implemented in the processors 11a, 11b, 21a, and 31. Each of the memory 12a, 12b, 22a, and 32 operatively stores a variety of programs and information to operate a connected processor. Each of the transceivers 13a, 13b, 23a, and 33 is operatively coupled with a connected processor, and transmits and/or receives radio signals or wireline signals. The UE 10a may be in communication with the UE 10b through a sidelink. The base station 20a may be an eNB, a gNB, or one of other types of radio nodes, and may configure radio resources for the UE 10a and UE 10b.

Each of the processors 11a, 11b, 21a, and 31 may include an application-specific integrated circuit (ASICs) , other chipsets, logic circuits and/or data processing devices. Each of the memory 12a, 12b, 22a, and 32 may include read-only memory (ROM) , a random access memory (RAM) , a flash memory, a memory card, a storage medium and/or other storage devices. Each of the transceivers 13a, 13b, 23a, and 33 may include baseband circuitry and radio frequency (RF) circuitry to process radio frequency signals. When the embodiments are implemented in software, the techniques described herein may be implemented with modules, procedures, functions, entities, and so on, that perform the functions described herein. The modules may be stored in a memory and executed by the processors. The memory may be implemented within a processor or external to the processor, in which those may be communicatively coupled to the processor via various means are known in the art.

The network entity device 30 may be a node in a CN. CN may include LTE CN or 5G core (5GC) which includes user plane function (UPF) , session management function (SMF) , access and mobility management function (AMF) , unified data management (UDM) , policy control function (PCF) , control plane (CP) /user plane (UP) separation (CUPS) , authentication server (AUSF) , network slice selection function (NSSF) , and the network exposure function (NEF) .

Examples of the relay UE and remote UE in the description may include UEs (e.g., the UE 10a or UE 10b) in FIG. 1. An example of the base station in the description may include a base station (e.g., the base station 20a) in FIG. 1. Uplink (UL) transmission of a control signal or data may be a transmission operation from a UE to a base station. Downlink (DL) transmission of a control signal or data may be a transmission operation from a base station to a UE. A DL control signal may comprise downlink control information (DCI) or a radio resource control (RRC) signal, from a base station to a UE.

3GPP Release 17 (Rel_17) introduced SL relay to enable 5G ProSe UE-to-Network Relay (U2N Relay) function. This function allows U2N remote UE (s) to connect to the network.

The L2 and L3 U2N Relay architectures both allow the U2N relay UE to relay data between a serving NG-RAN and a U2N remote UE. The difference is that the L3 U2N Relay is transparent to the serving NG-RAN, except for controlling sidelink resources.

FIG. 2 shows an example of sidelink relay with multiple bearers including bearer BR1 in one hop and bearers BR2 and BR3 in another hop. A remote UE 10d needs to determine a bearer when transmitting uplink traffic to relay UE 10c1 and gNB 20 through relay UE 10c2. The relay UE 10c2 needs to determine a bearer when transmitting uplink traffic to gNB 20 through relay UE 10c1. The gNB 20 has distributed units (DUs) 20-1 and 20-2.

FIG. 3 shows a user-plane protocol stack for sidelink relay. Examples of a remote UE 10f may include the remote UE 10d and UE 10e in FIG. 2. Examples of a relay UE 10c may include the relay UE 10c1 and relay UE 10c2 in FIG. 2. A PC5-PHY layer, a PC5-MAC layer, a PC5-RLC layer, a PC5-SRAP in the relay UE 10c communicate with a PC5-PHY layer, a PC5-MAC layer, a PC5-RLC layer, and a PC5-SRAP in the remote UE 10f. A Uu-PHY layer, a Uu-MAC layer, a Uu-RLC layer, a Uu-SRAP in the relay UE 10c communicate with a Uu-PHY layer, a Uu-MAC layer, a Uu-RLC layer, and a Uu-SRAP in the gNB 20.

A Uu-PDCP layer and a Uu-SDAP layer in the remote UE 10f communicate with Uu-PDCP layer and a Uu-SDAP layer in the gNB 20.

FIG. 4 shows a control-plane protocol stack for sidelink relay. A PC5-PHY layer, a PC5-MAC layer, a PC5-RLC layer, a PC5-SRAP in the relay UE 10c communicate with a PC5-PHY layer, a PC5-MAC layer, a PC5-RLC layer, and a PC5-SRAP in the remote UE 10f. A Uu-PHY layer, a Uu-MAC layer, a Uu-RLC layer, a Uu-SRAP in the relay UE 10c communicate with a Uu-PHY layer, a Uu-MAC layer, a Uu-RLC layer, and a Uu-SRAP in the gNB 20.

A Uu-PDCP layer and a Uu-RRC layer in the remote UE 10f communicate with Uu-PDCP layer and a Uu-RRC layer in the gNB 20.

The layers may be implemented as software or hardware entities, modules, or units, such as programs or circuits, or any combination.

As shown in the FIG. 3 and FIG. 4, in the protocol stack, the SRAP layer operates on a hop-by-hop basis, meaning that it handles the transmission and reception of data packets between adjacent nodes, such as between the remote UE 10f and relay UE 10c and between the relay UE 10c and the gNB 20. The PDCP layer operates on an end-to-end basis, which means it only works at the gNB and the remote UE, not at the relay UE. The relay UE does not have a PDCP layer, so there is no real data radio bearer (DRB) between the two UEs or between the relay UE and the gNB. Instead, there is an RLC channel, which is a bearer without PDCP, between each hop. The RLC channel is set up on a hop-by-hop basis. Similarly, each of the SRAP layer and RRC layer operates on an end-to-end basis.

As shown in FIG. 5 (a) , the current SRAP header only has one UE ID and one bearer ID used to determine an egress link and egress RLC channel. To support multi-hop sidelink relay, the SRAP header should be enhanced. Bearer mapping using the bearer mapping rules in the disclosure can address the bearer mapping issue. As shown in FIG. 5 (b) and FIG. 5 (c) , an SRAP header for DL data transfer contains a remote UE ID and a path ID, or an SRAP header for UL data transfer contains a Cell ID or DU ID and a path ID. The remote UE ID, path ID, Cell ID, and DU ID can be used for multi-hop sidelink relay and can address the bearer mapping issue.

In 3GPP Release 17 or 18, a relay UE can only work for one hop to the remote UE and one hop to the gNB. That is, the relay UE cannot forward the data to another relay UE. Therefore, the relay UE only needs one instance of UE ID information to identify the remote UE by its UE ID and one instance of bearer ID information to identify an egress RLC channel by its bearer ID.

The following summarizes the key features of 3GPP Rel_17/18 sidelink relay:

(1) . A unicast link can be established between one L2 U2N relay UE and one L2 U2N remote UE.

(2) . Rel-18 SL relay supports only one hop relay UE.

(3) . After acquiring a System Information Block (SIB) , the relay UE sends the SIB to the remote UE.

(4) . The U2N remote UE can send and receive Relay discovery messages on the sidelink in any RRC state, including RRC_IDLE, RRC_INACTIVE or RRC_CONNECTED.

(5) . The SRAP sublayer maps bearers and routes packets and supports the following functions:

Data transfer;

Determination of UE ID field and BEARER ID field for data packets;

Determination of egress link; and

Determination of egress RLC channel.

In some embodiments of the disclosure, the SRAP header will be extended to comply with the architecture of multi-hop sidelink relay.

With reference to FIG. 6, a remote UE 10f, relay UE 10c1, relay UE 10c2, and a gNB 20 execute an embodiment of a multi-hop sidelink relay method. An example of UE, such as UE 10c, UE 10c1, UE 10c2, and UE 10f, in the description may include the UE 10a or UE 10b. An example of the base station, such as gNB 20, in the description may include the base station 20a.

An example of downlink transfer of the downlink PDU over multi-hop sidelink relay is illustrated in the following. The gNB 20 transmits at least one downlink protocol data unit (PDU) through multi-hop sidelink relay to the remote UE 10f (S101) . The at least one downlink PDU may include one or more PDUs over Uu interface to the relay UE 10c1. In some embodiments of the disclosure, an indicator is signaled in a control plane message to configure whether the SRAP header of the PDU is used for multi-hop sidelink relay. In some embodiments of the disclosure, the SRAP header of the downlink PDU comprises a reserved bit used to indicate whether the SRAP header of the downlink PDU is used for multi-hop sidelink relay. In some embodiments of the disclosure, the SRAP header of the downlink PDU comprises a path identifier (ID) and a remote UE ID as the downlink routing information for multi-hop sidelink relay. The path ID identifies a downlink path for multi-hop sidelink relay. For example, the remote UE ID is a UE ID of the remote UE 10f.

Through the Uu interface, the relay UE 10c1 receives from the gNB 20 the downlink PDU as a PDU with the SRAP header that includes downlink routing information for multi-hop sidelink relay and transmits the PDU according to uplink routing information of the PDU (S102) .

Similarly, through a sidelink (e.g., ProSe interface) , the relay UE 10c2 receives from the relay UE 10c1 the downlink PDU as a PDU with the SRAP header that includes downlink routing information for multi-hop sidelink relay and transmits the PDU according to uplink routing information of the PDU (S103) .

Through a sidelink (e.g., ProSe interface) , the remote UE 10f receives from the relay UE 10c2 the downlink PDU as a PDU with the SRAP header that includes downlink routing information for multi-hop sidelink relay (S104) . Since the downlink PDU is destined to the remote UE 10f, downlink transfer of the downlink PDU is complete.

With reference to FIG. 7, an example of downlink transfer of the uplink PDU over multi-hop sidelink relay is illustrated in the following.

The remote UE 10f transmits an uplink PDU with an SRAP header that includes uplink routing information for multi-hop sidelink relay (S201) . The at least one uplink PDU may include one or more PDUs over sidelink (e.g., ProSe interface) to the relay UE 10c2. In some embodiments of the disclosure, the SRAP header of the uplink PDU comprises a reserved bit used to indicate whether the SRAP header of the uplink PDU is used for multi-hop sidelink relay. In some embodiments of the disclosure, the SRAP header of the uplink PDU comprises a path identifier (ID) and a base station related ID as the uplink routing information for multi-hop sidelink relay. The path ID identifies an uplink path for multi-hop sidelink relay. The base station related ID includes a distributed unit ID or a cell ID.

In some embodiments of the disclosure, in routing the uplink PDU, the sidelink remote UE determines the path ID based on channel busy rates (CBRs) of hops of a plurality of paths. The relay UE receives CBRs of hops in a sidelink control message from a neighbor relay UE and transfers the received CBRs of hops to a remote UE (e.g., UE 10) or a base station (e.g., gNB 20) . The remote UE (e.g., UE 10) receives the CBRs of hops in a sidelink control message from one or more relay UEs. The sidelink remote UE determines the path ID based on channel busy rates (CBRs) of hops of a plurality of paths. The base station (e.g., gNB 20) receives the CBRs of hops in a sidelink control message from one or more relay UEs. The base station determines the path ID in the routing configuration based on channel busy rates (CBRs) of hops of a plurality of paths.

Through a sidelink (e.g., ProSe interface) , the relay UE 10c2 receives from the remote UE 10f the uplink PDU as a PDU with the SRAP header that includes uplink routing information for multi-hop sidelink relay and transmits the PDU according to uplink routing information of the PDU (S202) .

Similarly, through a sidelink (e.g., ProSe interface) , the relay UE 10c1 receives from the relay UE 10c2 the uplink PDU as a PDU with the SRAP header that includes uplink routing information for multi-hop sidelink relay and transmits the PDU according to uplink routing information of the PDU (S203) .

Through the Uu interface, the gNB 20 receives from the relay UE 10c1 the uplink PDU as a PDU with the SRAP header that includes uplink routing information for multi-hop sidelink relay (S204) . Since the uplink PDU is destined to the remote gNB 20, uplink transfer of the uplink PDU is complete.

In some embodiments of the disclosure, in routing the uplink PDU, the remote UE determines the path ID based on routing configuration in a downlink configuration message. The routing configuration comprises routing rules. In some embodiments of the disclosure, the relay UE determines the path ID based on the routing configuration in a downlink configuration message.

With reference to FIG. 8, the gNB 20 transmits a routing configuration 120 in a downlink configuration message to all relay UEs, such as the relay UE 10c1, the relay UE 10c2, and in coverage remote UE, such as the remote UE 10f. The out-of-coverage remote UE, such as the remote UE 10f, may receive the routing configuration 120 through a relay UE. The routing configuration 120 comprises routing rules for path selection between paths of multi-hop sidelink relay, and the path selection is for routing one or more protocol data units (PDUs) over multi-hop sidelink relay. In some embodiments of the disclosure, the downlink configuration message may be a radio resource control (RRC) message.

In some embodiments of the disclosure, wherein the routing configuration comprises a list or a sequence of parameters of uplink routing configuration comprising one or more of:

a cell identity,

a distributed unit ID,

path IDs,

a list of relay UEs,

a default path, and

an indicator that indicates whether the relay UE is allowed to select a path or link.

In some embodiments of the disclosure, the gNB 20 may determine the routing configuration based on channel busy rates (CBRs) of hops of a plurality of paths. The gNB 20 may receive reporting of the CBRs from the relay UEs and/or remote UEs.

The relay UE receives the CBRs of hops through sidelink control signaling (e.g., in sidelink control message (s) ) from one or more neighbor relay UEs and sends the CBRs to the remote UE or the gNB 20. The sidelink remote UE may determine the path ID based on channel busy rates (CBRs) of hops of a plurality of paths. The gNB 20 may determine the path ID based on channel busy rates (CBRs) of hops of a plurality of paths.

In some embodiments of the disclosure, the bearer configuration comprises a bearer mapping table. In an embodiment, each bearer mapping rule in the bearer mapping table comprises an ingress radio link control (RLC) channel and an egress RLC channel. The bearer mapping rule specifies correlation between an egress RLC channel of a protocol data unit (PDU) and an ingress RLC channel of the PDU for routing the PDU over multi-hop sidelink relay. Each of the relay UEs determines an egress RLC channel of the PDU based on at least one bearer mapping rule in the bearer mapping table and an ingress RLC channel of the PDU, and the PDU comprises an uplink PDU or a downlink PDU.

In some embodiments of the disclosure, in routing the uplink PDU, the remote UE determines a bearer of the PDU based on bearer configuration in a downlink configuration message. Specifically, the remote UE determines an egress RLC channel of the uplink PDU based on at least one bearer mapping rule in the bearer mapping table.

In some embodiments of the disclosure, the bearer configuration comprises a bearer mapping table. In an embodiment, each bearer mapping rule in the bearer mapping table comprises a bearer mapping ID and an egress radio link control (RLC) channel. In an embodiment, each bearer mapping rule in the bearer mapping table comprises a bearer mapping ID, an ingress radio link control (RLC) channel and an egress RLC channel. The bearer mapping ID in the bearer mapping rule is correlated to a bearer mapping ID in a sidelink relay adaption protocol (SRAP) header of a protocol data unit (PDU) for routing over multi-hop sidelink relay. The bearer mapping rule specifies correlation between an egress RLC channel of a protocol data unit (PDU) and an ingress RLC channel of the PDU for routing the PDU over multi-hop sidelink relay. The relay UE retrieves a bearer mapping ID in the SRAP header of the PDU. The relay UE retrieves a bearer mapping rule in the bearer mapping table based on the bearer mapping ID in the SRAP header of the PDU. The relay UE determines an egress RLC channel of a PDU based on the bearer mapping rule in the bearer mapping table and an ingress RLC channel of the PDU, and the PDU comprises an uplink PDU or a downlink PDU.

In some embodiments of the disclosure, the gNB configures the bearer mapping IDs of all relay UEs and remote UEs using RRC configuration. The remote UE sets the bearer mapping ID inside the SRAP header according to the RRC configuration. In routing the uplink PDU, the remote UE determines a bearer mapping ID and includes the determined bearer mapping ID in the SRAP header of an uplink PDU. The relay UE retrieves a bearer mapping rule in the bearer mapping table based on the determined bearer mapping ID in the SRAP header of the uplink PDU. The relay UE determines an egress RLC channel of an uplink PDU based on the bearer mapping rule in the bearer mapping table.

Embodiment 1: An embodiment regarding SRAP header for routing is detailed in the following. Note that the scheme in the following can be applied to other embodiments.

With reference to FIG. 5 (b) , an SRAP header for DL data transfer contains a remote UE ID and a path ID. For DL data transfer through sidelink relay, the final destination is a remote UE, such as the remote UE 10d or UE 10e in FIG. 2, so the UE ID of the remote UE is required and included in a field originally used for UE ID a SRAP header. For simplicity, the field is referred to as UE ID field in the following.

With reference to FIG. 5 (c) , an SRAP header for UL data transfer contains a Cell ID or DU ID and a path ID. For UL data transfer through sidelink relay, the final destination is a gNB DU or a cell in gNB, such as a DU or a cell of the gNB 20 in FIG. 2. Note that the donor relay UE, such as relay UE 10c1, may have dual connection to two gNB DU, such as a DU 20-1 and DU 20-2 of the gNB 20 in FIG. 2, so the UE ID field can be used to identify the gNB DU ID or cell ID.

With reference to FIG. 9, a relay UE3 has two possible paths to gNB 20 in the UL direction: P1 and P3. When receiving packets from a remote UE6, the relay UE3 should select a path to forward the packets to the gNB 20. The remote UE6 is an example of the remote UE 10f, and relay UE1, UE2, UE3, UE4, and UE5 are examples of the relay UE 10c.

With reference to FIG. 5 (b) and (c) , a path ID is added to the SRAP header to identify a path, such as P1, P2, or P3 in FIG. 9. In the SRAP hear, R is a reserved bit. The first R bit is used to indicate whether the SRAP header is an enhanced SRAP header or not. In the first R bit, S” stands for single hop sidelink relay, and “M” stands for multiple hops sidelink relay.

In this embodiment, no modifications are made to the BEARER ID, and later embodiments will make modifications to the BEARER ID for bearer mapping.

Embodiment 2: An embodiment regarding UL route selection is detailed in the following. Note that the scheme in the following can be applied to other embodiments.

This embodiment addresses the scenario where the remote UE6 in FIG. 9 has three possible paths P1, P2, and P3 to reach the gNB 20 via intermediate relay UEs. The challenge is to ensure that each relay UE can select a path and find the next hop on the path. This embodiment focuses on the path selection for the uplink, where the remote UE sets the SRAP header for path selection, i.e., routing. The gNB 20 provides routing configuration to the remote UEs and relay UEs. The remote UEs and relay UEs should follow the routing configuration from the gNB 20. This configuration specifies the entire routing information or the paths, including links of each path. The routing information may comprise a routing table.

In an embodiment of the invention, the remote UE also needs to know the routing table, so as to add the SRAP header for routing. The gNB 20 may configure a routing table and provide the routing table as routing configuration to the remote UEs and relay UEs via RRC signaling in the RRC layer. The routing table includes routing entries. Each routing entry has a routing ID and indicates a cell ID (or a DU ID) , a path ID associated with the cell ID, and a list of the intermediate relay UEs. As mentioned in the above, a cell ID or a DU ID may be used to identify a destination of a packet.

As shown in Table 2, here is an example of UL routing configuration represented by an information element (IE) ulRoutingConfigurationlist-r19.

Table 2

The example introduces new configuration parameters, including the cell ID (or gNB DU ID) or DU ID of a serving base station, such as the gNB 20, in uplink data transfer path. The ulRoutingConfigurationlist-r19 is an uplink routing configuration list and comprises a list or a sequence of ULRoutingConfiguration-r19 IE. The ULRoutingConfiguration-r19 IE is a basic element of UL routing configuration and comprises a sequence of parameters. The parameters comprise cell identity (CellIdentity) , DU ID (DU_Identity) , path ID (SL-Relay-Path-Id) , a list of relay UEs (RELAY-UEList-r19) , a default path, and an indicator that indicates whether a relay UE or a remote UE is allowed to select a path or link.

RELAY-UEList-r19 is a list of relay UEs and includes a sequence of UE IDs (represented by UE-ID) .

The constant maxNrofUE-ID-r19 is a maximum of UE IDs in the RELAY-UEList-r19, such as 32.

The constant maxNrofRoutingConfig-r19 is a maximum of routing configurations, such as 32.

The parameter sl-relay-default-path-id-r19 indicates a default path. The UE selects the default path based on its preference or availability of other paths. The default path is the one that the UE uses when it cannot find a better path.

The parameter If_UE_selection_allowed indicates whether a relay UE or a remote UE is allowed to select a path or link. For example, a value TRUE of the parameter If_UE_selection_allowed indicates a relay UE or a remote UE is allowed to select a path or link. A value FLASE of the parameter If_UE_selection_allowed indicates a relay UE or a remote UE is not allowed to select a path or link. The parameter is optional. The same effects may be achieved via implicit signaling. This approach does not require explicit signaling from the network. For example, the gNB 20 can configure multiple paths for a remote UE or a relay UE and let the UE choose the best one based on its own criteria. The remote UE or relay UE can determine that the relay UE or remote UE is allowed to select a path or link based on presence of the configuration. If the gNB 20 does not configure multiple paths for a remote UE or a relay UE, the remote UE or relay UE can determine that the relay UE or remote UE is not allowed to select a path or link based on absence of the configuration. The criteria are illustrated in the following.

The embodiment provides a method for relay UEs and remote UEs to receive a configuration that indicates the available links, as well as relay UEs and hops for each whole link. The configuration helps remote UEs to select the optimal path for data transmission. For uplink data transfer, each relay UE can also select and switch to a new path based on the congestion level (e.g., channel busy rate, CBR) and the number of hops of the remaining portion of paths for the uplink transfer. For example, with reference to FIG. 12, consider a scenario where a remote UE 10f communicates with the gNB 20 through a path of 4 hops. The path includes:

First hop: remote UE 10f to Relay UE3;

Second hop: Relay UE3 to Relay UE2;

Third hop: Relay UE2 to Relay UE1; and

Fourth hop: Relay UE1 to DU 20-1.

Relay UE2 knows that itself is the destination of the second hop in the path and that there are two more hops to reach the DU 20-1.

The intermediate relay UE does not modify the SRAP header, such as cell ID, path ID, or UE ID, unless there are some exceptional situations, such as the next hop experiencing radio link failure (RLF) . In such an exception situation, the cell ID, path ID, and UE ID may be changed by the relay UE.

To configure the remote UE and relay UE properly, the gNB 20 has to know the congestion level (e.g., CBR) of each hop of the sidelink relay path. This requires new signaling for CBR reporting from UEs to the gNB.

The channel busy ratio (CBR) of each sidelink can be determined by one or both UEs involved in the sidelink communication. In the example of FIG. 10, the relay UE1 can measure the CBR of hop1 and report it to relay UE2. The relay UE2 measures the CBR of hop2 and reports the CBR of hop1 and hop2 together to relay UE3. The relay UE3 can measure the CBR of hop3 and reports the measured CBR of hop3, hop2, and hop1 together to the gNB 20.

The gNB 20 determines routing configuration based on the measured CBR of hop3, hop2, and hop1 and provides the routing configuration to the remote UEs and relay UEs.

Embodiment 3: An embodiment regarding CBR notification to the UE is detailed in the following. Note that the scheme in the following can be applied to other embodiments.

The embodiment provides an example of how the remote UE can obtain the CBR of each hop in order to determine the uplink routing configuration. This is different from the previous embodiment. In the embodiment 2, the gNB 20 was responsible for getting the CBR of each hop and making decision for providing the uplink routing configuration. In the embodiment 3, a remote UE, such as remote UE 10f, receives the measured CBR of hop3, hop2, and hop1. Because routing for uplink data transfer affects the uplink performance and reliability, the remote UE 10f needs to know the CBR of each hop and select an uplink path based on the measured CBR of each hop.

To route efficiently, the remote UE must estimate the global topology based on the CBR of each sidelink hop. For example, the remote UE 10f finds the least congested and shortest path to route uplink packets based on the CBR. As shown in FIG. 11, relay UE2 reports the CBR of hop3 to relay UE1, and relay UE 1 reports the CBR of hop2 and hop3 to the remote UE 10f. CBR of hop1 can be reported by relay UE1 to remote UE 10f or directly measured by remote UE 10f itself.

The remote UE 10f determines a path based on the measured CBR of hop3, hop2, and hop1, includes a path ID of the path in an SRAP header of an uplink packet, and transmits the packet to a relay UE on the path.

Embodiment 4: An embodiment regarding bearer mapping is detailed in the following. Note that the scheme in the following can be applied to other embodiments.

The Rel_17 SRAP header contains the egress bearer ID to identify the egress RLC channel for each SL packet. This is sufficient for Rel_17 SL relay, where only one hop is allowed. The BEARER ID IE only applies to the egress RLC channel, so a fixed bearer ID does not cause any problem in Rel_17 sidelink relay.

However, in Rel_19 SL relay, there are multiple hops in the path, and the egress bearer ID cannot specify the egress RLC channel for each hop. Therefore, the bearer ID needs to be enhanced in Rel_19 SL relay.

With reference to FIG. 12, in a multi-hop sidelink relay scenario, when remote UE sends a SRAP packet to the relay UE3, which has two bearers: BR1 and BR2. The SRAP packet contains a bearer ID that indicates which bearer to use for one hop. The relay UE3 will map the packet to a bear of the bearer ID in the SRAP header. However, this causes ambiguity for relay UE2, which receives the packet from relay UE3. relay UE2 does not know which bearer to use for the next hop, since the bearer ID is only valid for one hop.

This embodiment introduces two options of bearer mapping using SRAP header for multi-hop sidelink relay.

Option 1: The gNB 20 sends to each relay UE an upper layer signal, such as an RRC message conveying an RRC configuration, to configure the bearer mapping.

In this option, the RRC configuration includes bearer mapping rules for each relay UE. The rules contain a bearer mapping table. Each entry of the mapping table represents a mapping between an ingress RLC channel ID and an egress RLC channel ID. Each entry of the mapping table can be a mapping rule. Table 3 shows an example of the bearer mapping table.

One possible way to handle bearer mapping is to eliminate the use of bearer ID IE, which frees up some bits for other purposes. This option seems simple, as it only involves changing the RRC configuration. However, this option has some drawbacks. It does not allow for a per SRAP bearer mapping, and it does not make use of the SRAP sublayer as intended. It also reduces the flexibility of forwarding SRAP packets.

Table 3: Bearer mapping table

This scheme is semi-static, meaning that relay UEs forward ingress packets from the ingress RLC channel directly to the egress RLC channel without processing them.

Option 2: BEARER ID IE is used for bearer mapping ID.

In this option, the legacy BEARER ID IE is used for bearer mapping ID. when receiving a SRAP PDU with BEARER MAPPING ID in the SRAP header, a relay UE determines a corresponding egress RLC channel in the bearer mapping table configured by RRC layer.

This option uses the legacy BEARER ID IE as the bearer mapping ID. When receiving a SRAP PDU with BEARER MAPPING ID in the SRAP header, the relay UE checks the BEARER MAPPING ID in the SRAP header of the received SRAP PDU and finds a corresponding egress RLC channel in the bearer mapping table in the RRC configuration.

The bearer mapping table is illustrated in the next page.

Embodiment 4 only changes the BEARER ID in the SRAP header to BEARER MAPPING ID for bearer mapping, while the previous two embodiment change the routing function of the SRAP. In practice, these two applications can be combined to change the SRAP header.

The RRC configuration may comprise a bearer mapping table that includes the bearer mapping rule and the bearer mapping ID. When receiving the SRAP PDU with a bearer mapping ID, the relay UE uses the table to find the egress RLC channel based on the ingress RLC channel. Table 3 shows an example of the bearer mapping table.

Table 4: Bearer mapping table

Each row of the bear mapping table forms a bearer mapping rule and includes a bearer mapping ID, an ingress RLC channel, and an egress RLC channel.

With reference to FIG. 14, the gNB 20 transmits bearer configuration 121 in a downlink configuration message to a sidelink remote user equipment (UE) and sidelink relay UEs (S302) . A protocol data unit (PDU) for multi-hop sidelink relay to or from the gNB 20 has a sidelink relay adaption protocol (SRAP) header that includes bearer mapping information and is conveyed in a bearer that is determined according to a bearer mapping rule in the bearer configuration 121.

The UE 10 configures a protocol data unit (PDU) with a sidelink relay adaption protocol (SRAP) header that includes bearer mapping information for multi-hop sidelink relay (S304) . The UE 10 transmits the PDU through an egress bearer corresponding to an ingress bearer of the PDU according to a bearer mapping rule in the bearer configuration 121 (S306) . The bearer configuration 121 may be a portion of the routing configuration or not. The embodiment associated bearer configuration may be implemented independent of the embodiment of routing configuration.

FIG. 15 is a block diagram of an example system 700 for wireless communication according to an embodiment of the present disclosure. Embodiments described herein may be implemented into the system using any suitably configured hardware and/or software. FIG. 15 illustrates the system 700 including a radio frequency (RF) circuitry 710, a baseband circuitry 720, a processing unit 730, a memory/storage 740, a display 750, a camera 760, a sensor 770, and an input/output (I/O) interface 780, coupled with each other as illustrated.

The processing unit 730 may include circuitry, such as, but not limited to, one or more single-core or multi-core processors. The processors may include any combinations of general-purpose processors and dedicated processors, such as graphics processors and application processors. The processors may be coupled with the memory/storage and configured to execute instructions stored in the memory/storage to enable various applications and/or operating systems running on the system.

The baseband circuitry 720 may include circuitry, such as, but not limited to, one or more single-core or multi-core processors. The processors may include a baseband processor. The baseband circuitry may handle various radio control functions that enable communication with one or more radio networks via the RF circuitry. The radio control functions may include, but are not limited to, signal modulation, encoding, decoding, radio frequency shifting, etc. In some embodiments, the baseband circuitry may provide for communication compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry may support communication with 5G NR, LTE, an evolved universal terrestrial radio access network (EUTRAN) and/or other wireless metropolitan area networks (WMAN) , a wireless local area network (WLAN) , a wireless personal area network (WPAN) . Embodiments in which the baseband circuitry is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuitry. In various embodiments, the baseband circuitry 720 may include circuitry to operate with signals that are not strictly considered as being in a baseband frequency. For example, in some embodiments, baseband circuitry may include circuitry to operate with signals having an intermediate frequency, which is between a baseband frequency and a radio frequency.

The RF circuitry 710 may enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium. In various embodiments, the RF circuitry may include switches, filters, amplifiers, etc. to facilitate communication with the wireless network. In various embodiments, the RF circuitry 710 may include circuitry to operate with signals that are not strictly considered as being in a radio frequency. For example, in some embodiments, RF circuitry may include circuitry to operate with signals having an intermediate frequency, which is between a baseband frequency and a radio frequency.

In various embodiments, the transmitter circuitry, control circuitry, or receiver circuitry discussed above with respect to the UE, eNB, or gNB may be embodied in whole or in part in one or more of the RF circuitries, the baseband circuitry, and/or the processing unit. As used herein, “circuitry” may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC) , an electronic circuit, a processor (shared, dedicated, or group) , and/or memory (shared, dedicated, or group) that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable hardware components that provide the described functionality. In some embodiments, the electronic device circuitry may be implemented in, or functions associated with the circuitry may be implemented by, one or more software or firmware modules. In some embodiments, some or all of the constituent components of the baseband circuitry, the processing unit, and/or the memory/storage may be implemented together on a system on a chip (SOC) .

The memory/storage 740 may be used to load and store data and/or instructions, for example, for the system. The memory/storage for one embodiment may include any combination of suitable volatile memory, such as dynamic random access memory (DRAM) ) , and/or non-volatile memory, such as flash memory. In various embodiments, the I/O interface 780 may include one or more user interfaces designed to enable user interaction with the system and/or peripheral component interfaces designed to enable peripheral component interaction with the system. User interfaces may include, but are not limited to a physical keyboard or keypad, a touchpad, a speaker, a microphone, etc. Peripheral component interfaces may include, but are not limited to, a non-volatile memory port, a universal serial bus (USB) port, an audio jack, and a power supply interface.

In various embodiments, the sensor 770 may include one or more sensing devices to determine environmental conditions and/or location information related to the system. In some embodiments, the sensors may include, but are not limited to, a gyro sensor, an accelerometer, a proximity sensor, an ambient light sensor, and a positioning unit. The positioning unit may also be part of, or interact with, the baseband circuitry and/or RF circuitry to communicate with components of a positioning network, e.g., a global positioning system (GPS) satellite. In various embodiments, the display 750 may include a display, such as a liquid crystal display and a touch screen display. In various embodiments, the system 700 may be a mobile computing device such as, but not limited to, a laptop computing device, a tablet computing device, a netbook, an ultrabook, a smartphone, etc. In various embodiments, the system may have more or less components, and/or different architectures. Where appropriate, the methods described herein may be implemented as a computer program. The computer program may be stored on a storage medium, such as a non-transitory storage medium.

The embodiment of the present disclosure is a combination of techniques/processes that may be adopted in 3GPP specification to create an end product.

A person having ordinary skill in the art understands that each of the units, algorithm, and steps described and disclosed in the embodiments of the present disclosure are realized using electronic hardware or combinations of software for computers and electronic hardware. Whether the functions run in hardware or software depends on the condition of the application and design requirement for a technical plan. A person having ordinary skill in the art may use different ways to realize the function for each specific application while such realizations should not go beyond the scope of the present disclosure. It is understood by a person having ordinary skill in the art that he/she may refer to the working processes of the system, device, and unit in the above-mentioned embodiment since the working processes of the above-mentioned system, device, and unit are basically the same. For easy description and simplicity, these working processes will not be detailed.

It is understood that the disclosed system, device, and method in the embodiments of the present disclosure may be realized in other ways. The above-mentioned embodiments are exemplary only. The division of the units is merely based on logical functions while other divisions exist in realization. It is possible that a plurality of units or components are combined or integrated into another system. It is also possible that some characteristics are omitted or skipped. On the other hand, the displayed or discussed mutual coupling, direct coupling, or communicative coupling operates through some ports, devices, or units whether indirectly or communicatively by ways of electrical, mechanical, or other kinds of forms.

The units as separating components for explanation are or are not physically separated. The units for display are or are not physical units, that is, located in one place or distributed on a plurality of network units. Some or all of the units are used according to the purposes of the embodiments. Moreover, each of the functional units in each of the embodiments may be integrated into one processing unit, physically independent, or integrated into one processing unit with two or more than two units.

If the software function unit is realized and used and sold as a product, it may be stored in a readable storage medium in a computer. Based on this understanding, the technical plan proposed by the present disclosure may be essentially or partially realized in the form of a software product. Or, one part of the technical plan beneficial to the conventional technology may be realized as the form of a software product. The software product in the computer is stored in a storage medium, including a plurality of commands for a computational device (such as a personal computer, a server, or a network device) to run all or some of the steps disclosed by the embodiments of the present disclosure. The storage medium includes a USB disk, a mobile hard disk, a read-only memory (ROM) , a random access memory (RAM) , a floppy disk, or other kinds of media capable of storing program codes.

While the present disclosure has been described in connection with what is considered the most practical and preferred embodiments, it is understood that the present disclosure is not limited to the disclosed embodiments but is intended to cover various arrangements made without departing from the scope of the broadest interpretation of the appended claims.

Claims

A multi-hop sidelink relay method for execution by a user equipment (UE) serving as a sidelink relay UE or a sidelink remote UE, comprising:

configuring a protocol data unit (PDU) with a sidelink relay adaption protocol (SRAP) header that includes bearer mapping information for multi-hop sidelink relay; and

transmitting the PDU through an egress bearer corresponding to an ingress bearer of the PDU according to a bearer mapping rule.
The multi-hop sidelink relay method of claim 1, wherein an indicator is signaled in a control plane message to configure whether the SRAP header of the PDU is used for multi-hop sidelink relay.
The multi-hop sidelink relay method of claim 1, wherein the SRAP header comprises a reserved bit used to indicate whether the SRAP header of the PDU is used for multi-hop sidelink relay.
The multi-hop sidelink relay method of claim 1, wherein the SRAP header of the PDU comprises a path identifier (ID) and a remote UE ID as downlink routing information for multi-hop sidelink relay;

the path ID identifies a downlink path for multi-hop sidelink relay.
The multi-hop sidelink relay method of claim 1, wherein the SRAP header of the PDU comprises a path identifier (ID) and a base station related ID as uplink routing information for multi-hop sidelink relay;

the path ID identifies an uplink path for multi-hop sidelink relay; and

the base station related ID includes a distributed unit ID or a cell ID.
The multi-hop sidelink relay method of claim 5 or 4, wherein the UE is a sidelink remote UE sets the path ID based on routing configuration in a downlink configuration message; and

the routing configuration comprises routing rules.
The multi-hop sidelink relay method of claim 6, wherein the routing configuration comprises a list or a sequence of parameters of uplink routing configuration comprising one or more of:

a cell identity,

a distributed unit ID,

path IDs,

a list of relay UEs,

a default path, and

an indicator that indicates whether the relay UE is allowed to select a path or link.
The multi-hop sidelink relay method of claim 6, wherein the routing configuration is based on channel busy rates (CBRs) of hops of a plurality of paths.
The multi-hop sidelink relay method of claim 6, wherein a sidelink remote UE determines the path ID based on channel busy rates (CBRs) of hops of a plurality of paths.
The multi-hop sidelink relay method of claim 6 or 9, wherein the relay UE receives CBRs of hops in a sidelink control message from a neighbor relay UE and transfers the received CBRs of hops to a remote UE or a base station.
The multi-hop sidelink relay method of claim 1, 4, or 5, wherein the UE is a sidelink relay UE and determines a bearer of the PDU based on bearer configuration in a downlink configuration message;

the bearer configuration comprises a bearer mapping table;

each bearer mapping rule in the bearer mapping table comprises an ingress radio link control (RLC) channel and an egress RLC channel.
The multi-hop sidelink relay method of claim 11, wherein

the relay UE determines an egress RLC channel of the PDU based on at least one bearer mapping rule in the bearer mapping table and an ingress RLC channel of the PDU, and the PDU comprises an uplink PDU or a downlink PDU.
The multi-hop sidelink relay method of claim 1, 4, or 5, wherein the UE is a sidelink relay UE and determines a bearer of the PDU based on bearer configuration in a downlink configuration message;

the bearer configuration comprises a bearer mapping table;

each bearer mapping rule in the bearer mapping table comprises a bearer mapping ID and an egress radio link control (RLC) channel.
The multi-hop sidelink relay method of claim 13, wherein each bearer mapping rule in the bearer mapping table comprises a bearer mapping ID, an ingress radio link control (RLC) channel and an egress radio link control (RLC) channel.
The multi-hop sidelink relay method of claim 13, wherein

the relay UE retrieves a bearer mapping ID in the SRAP header of the PDU;

the relay UE retrieves a bearer mapping rule in the bearer mapping table based on the bearer mapping ID in the SRAP header of the PDU; and

the relay UE determines an egress RLC channel of a PDU based on the bearer mapping rule in the bearer mapping table, and the PDU comprises an uplink PDU or a downlink PDU.
A user equipment (UE) comprising:

a processor configured to call and run a computer program stored in a memory, to cause a device in which the processor is installed to execute the method of any of claims 1 to 15.
A chip, comprising:

a processor, configured to call and run a computer program stored in a memory, to cause a device in which the chip is installed to execute the method of any of claims 1 to 15.
A computer-readable storage medium, in which a computer program is stored, wherein the computer program causes a computer to execute the method of any of claims 1 to 15.
A computer program product, comprising a computer program, wherein the computer program causes a computer to execute the method of any of claims 1 to 15.
A computer program, wherein the computer program causes a computer to execute the method of any of claims 1 to 15.
A multi-hop sidelink relay method for execution by a user equipment (UE) serving as a sidelink relay UE or a sidelink remote UE, comprising:

receiving a protocol data unit (PDU) with a sidelink relay adaption protocol (SRAP) header that includes routing information for multi-hop sidelink relay; and

transmitting the PDU according to routing information of the PDU.
The multi-hop sidelink relay method of claim 21, wherein an indicator is signaled in a control plane message to configure whether the SRAP header of the PDU is used for multi-hop sidelink relay.
The multi-hop sidelink relay method of claim 21, wherein the SRAP header comprises a reserved bit used to indicate whether the SRAP header of the PDU is used for multi-hop sidelink relay.
The multi-hop sidelink relay method of claim 21, wherein the SRAP header comprises a path identifier (ID) and a remote UE ID as downlink routing information for multi-hop sidelink relay;

the path ID identifies a downlink path for multi-hop sidelink relay.
The multi-hop sidelink relay method of claim 21, wherein the SRAP header comprises a path identifier (ID) and a base station related ID as uplink routing information for multi-hop sidelink relay;

the path ID identifies an uplink path for multi-hop sidelink relay; and

the base station related ID includes a distributed unit ID or a cell ID.
The multi-hop sidelink relay method of claim 25 or 24, wherein the UE is a sidelink relay UE determines the path ID based on routing configuration in a downlink configuration message; and

the routing configuration comprises routing rules.
The multi-hop sidelink relay method of claim 26, wherein the routing configuration comprises a list or a sequence of parameters of uplink routing configuration comprising one or more of:

a cell identity,

a distributed unit ID,

path IDs,

a list of relay UEs,

a default path, and

an indicator that indicates whether the relay UE is allowed to select a path or link.
The multi-hop sidelink relay method of claim 26, wherein the routing configuration is based on channel busy rates (CBRs) of hops of a plurality of paths.
The multi-hop sidelink relay method of claim 26, wherein a sidelink remote UE determines the path ID based on channel busy rates (CBRs) of hops of a plurality of paths.
The multi-hop sidelink relay method of claim 26 or 29, wherein the relay UE receives CBRs of hops in a sidelink control message from a neighbor relay UE and transfers the received CBRs of hops to a remote UE or a base station.
The multi-hop sidelink relay method of claim 21, 24, or 25, wherein the UE is a sidelink relay UE and determines a bearer of the PDU based on bearer configuration in a downlink configuration message;

the bearer configuration comprises a bearer mapping table;

each bearer mapping rule in the bearer mapping table comprises an ingress radio link control (RLC) channel and an egress RLC channel.
The multi-hop sidelink relay method of claim 31, wherein

the relay UE determines an egress RLC channel of the PDU based on at least one bearer mapping rule in the bearer mapping table and an ingress RLC channel of the PDU, and the PDU comprises an uplink PDU or a downlink PDU.
The multi-hop sidelink relay method of claim 21, 24, or 25, wherein the UE is a sidelink relay UE and determines a bearer of the PDU based on bearer configuration in a downlink configuration message;

the bearer configuration comprises a bearer mapping table;

each bearer mapping rule in the bearer mapping table comprises a bearer mapping ID and an egress RLC channel.
The multi-hop sidelink relay method of claim 33, wherein each bearer mapping rule in the bearer mapping table comprises a bearer mapping ID, an ingress radio link control (RLC) channel and an egress RLC channel.
The multi-hop sidelink relay method of claim 33, wherein

the relay UE retrieves a bearer mapping ID in the SRAP header of the PDU;

the relay UE retrieves a bearer mapping rule in the bearer mapping table based on the bearer mapping ID in the SRAP header of the PDU; and

the relay UE determines an egress RLC channel of a PDU based on the bearer mapping rule in the bearer mapping table, and the PDU comprises an uplink PDU or a downlink PDU.
A user equipment (UE) comprising:

a processor configured to call and run a computer program stored in a memory, to cause a device in which the processor is installed to execute the method of any of claims 21 to 35.
A chip, comprising:

a processor, configured to call and run a computer program stored in a memory, to cause a device in which the chip is installed to execute the method of any of claims 21 to 35.
A computer-readable storage medium, in which a computer program is stored, wherein the computer program causes a computer to execute the method of any of claims 21 to 35.
A computer program product, comprising a computer program, wherein the computer program causes a computer to execute the method of any of claims 21 to 35.
A computer program, wherein the computer program causes a computer to execute the method of any of claims 21 to 35.
A multi-hop sidelink relay method for execution by a base station, comprising:

transmitting a routing configuration in a downlink configuration message, wherein the routing configuration comprises routing rules for path selection between paths of multi-hop sidelink relay, and the path selection is for routing one or more protocol data units (PDUs) over multi-hop sidelink relay.
The multi-hop sidelink relay method of claim 41, wherein the routing configuration comprises a list or a sequence of parameters of uplink routing configuration comprising one or more of:

a cell identity,

a distributed unit ID,

path IDs,

a list of relay UEs,

a default path, and

an indicator that indicates whether the relay UE is allowed to select a path or link.
The multi-hop sidelink relay method of claim 41, wherein the base station receives channel busy rates (CBRs) of hops of a plurality of paths and determines the routing configuration based on the channel busy rates (CBRs) of hops.
The multi-hop sidelink relay method of claim 41, wherein the routing configuration comprises bearer configuration that includes a bearer mapping table;

each bearer mapping rule in the bearer mapping table comprises an ingress radio link control (RLC) channel and an egress RLC channel; and

the bearer mapping rule specifies correlation between an egress RLC channel of a protocol data unit (PDU) and an ingress RLC channel of the PDU for routing the PDU over multi-hop sidelink relay.
The multi-hop sidelink relay method of claim 41, wherein the routing configuration comprises bearer configuration that includes a bearer mapping table;

each bearer mapping rule in the bearer mapping table comprises a bearer mapping ID and an egress radio link control (RLC) channel;

the bearer mapping ID in the bearer mapping rule is correlated to a bearer mapping ID in a sidelink relay adaption protocol (SRAP) header of a protocol data unit (PDU) for routing over multi-hop sidelink relay;

the bearer mapping rule specifies an egress RLC channel of a protocol data unit (PDU) for routing the PDU over multi-hop sidelink relay.
The multi-hop sidelink relay method of claim 45, wherein each bearer mapping rule in the bearer mapping table comprises a bearer mapping ID, an ingress radio link control (RLC) channel and an egress RLC channel.
The multi-hop sidelink relay method of claim 45, wherein the bearer mapping rule specifies correlation between an egress RLC channel of a protocol data unit (PDU) and an ingress RLC channel of the PDU for routing the PDU over multi-hop sidelink relay.
A base station comprising:

a processor configured to call and run a computer program stored in a memory, to cause a device in which the processor is installed to execute the method of any of claims 41 to 47.
A chip, comprising:

a processor, configured to call and run a computer program stored in a memory, to cause a device in which the chip is installed to execute the method of any of claims 41 to 47.
A computer-readable storage medium, in which a computer program is stored, wherein the computer program causes a computer to execute the method of any of claims 41 to 47.
A computer program product, comprising a computer program, wherein the computer program causes a computer to execute the method of any of claims 41 to 47.
A computer program, wherein the computer program causes a computer to execute the method of any of claims 41 to 47.
A multi-hop sidelink relay method for execution by a base station, comprising:

transmitting bearer configuration in a downlink configuration message to a sidelink remote user equipment (UE) and sidelink relay UEs;

wherein a protocol data unit (PDU) for multi-hop sidelink relay to or from the base station has a sidelink relay adaption protocol (SRAP) header that includes bearer mapping information and is conveyed in a bearer that is determined according to a bearer mapping rule in the bearer configuration.
The multi-hop sidelink relay method of claim 53, wherein the bearer mapping information comprises a bearer mapping identifier (ID) associated with the bearer mapping rule.
The multi-hop sidelink relay method of claim 53 or 54, wherein the bearer configuration comprises a bearer mapping table;

each bearer mapping rule in the bearer mapping table comprises an ingress radio link control (RLC) channel and an egress RLC channel.
The multi-hop sidelink relay method of claim 55, wherein a sidelink relay UE determines an egress RLC channel of the PDU based on at least one bearer mapping rule in the bearer mapping table and an ingress RLC channel of the PDU, and the PDU comprises an uplink PDU or a downlink PDU.
The multi-hop sidelink relay method of claim 53 or 54, wherein the bearer configuration comprises a bearer mapping table;

each bearer mapping rule in the bearer mapping table comprises a bearer mapping ID and an egress radio link control (RLC) channel.
The multi-hop sidelink relay method of claim 57, wherein each bearer mapping rule in the bearer mapping table comprises a bearer mapping ID, an ingress radio link control (RLC) channel and an egress radio link control (RLC) channel.
A base station comprising:

a processor configured to call and run a computer program stored in a memory, to cause a device in which the processor is installed to execute the method of any of claims 53 to 58.
A chip, comprising:

a processor, configured to call and run a computer program stored in a memory, to cause a device in which the chip is installed to execute the method of any of claims 53 to 58.
A computer-readable storage medium, in which a computer program is stored, wherein the computer program causes a computer to execute the method of any of claims 53 to 58.
A computer program product, comprising a computer program, wherein the computer program causes a computer to execute the method of any of claims 53 to 58.
A computer program, wherein the computer program causes a computer to execute the method of any of claims 53 to 58.