Apparatus and method for sidelink communication

Abstract

A method performed by a relay UE is provided. The relay UE establishes a first RLC channel between the first remote UE and the relay UE, wherein the first RLC channel is associated with the first end-to-end identifier. The relay UE establishes a second RLC channel between the second remote UE and the relay UE, wherein the second RLC channel is associated with the first end-to-end identifier or the second end-to-end identifier. The relay UE receives an incoming sidelink transmission from a first remote UE on a first RLC channel, wherein the incoming sidelink transmission includes a first end-to-end identifier. The relay UE transmits an outgoing sidelink transmission on a second RLC channel to a second remote UE, wherein the outgoing sidelink transmission includes one of the first end-to-end identifier and the second end-to-end identifier.

Description

Technical Field

[0001] The present application generally relates to mobile communications, and more particularly, to apparatuses and methods for sidelink (SL) communication in a user equipment (UE)-to-user equipment relay architecture. Background Art

[0002] In a typical mobile communication environment, a UE (also referred to as a mobile station (MS)) with wireless communication capabilities, such as a mobile phone (also known as a cellular phone or cell phone) or a tablet personal computer (PC), may transmit voice and / or data signals to one or more cellular networks. The wireless communication between the UE and the cellular network may be performed using various radio access technologies (RATs), such as Global System for Mobile communication (GSM) technology, General Packet Radio Service (GPRS) technology, Enhanced Data rates for Global Evolution (EDGE) technology, Wideband Code Division Multiple Access (WCDMA) technology, Code Division Multiple Access 2000 (CDMA-2000) technology, Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) technology, Worldwide Interoperability for Microwave Access (WiMAX) technology, Long Term Evolution (LTE) technology, and Long Term Evolution-Advanced (LTE-A) technology, etc.

[0003] These RAT technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate at the municipal, national, regional, or even global level. An example of an emerging telecommunication standard is 5G New Radio (NR). 5G NR is an enhanced set of the LTE mobile standard released by the Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, reducing costs, and enhancing services.

[0004] In LTE and 5G NR networks, device-to-device (D2D) communication is supported to allow two or more UEs to communicate directly with each other. This D2D communication can also be referred to as SideLink (SL) communication, which can be applied to vehicular communication services also known as Vehicle-to-Everything (V2X) services. V2X generally refers to communication technologies via all interfaces of a vehicle, including Vehicle-to-Vehicle (V2V), Vehicle-to-Infrastructure (V2I), Vehicle-to-Person (V2P), and Vehicle-to-Network (V2N). Specifically, in some cases, two UEs may have data to exchange, but due to physical distance or obstacles, they may not be able to communicate directly with each other. To be used in such cases, a UE-to-UE relay design is considered, where a relay UE can be used to forward data between two or more remote UEs.

[0005] In a layer 2 UE-to-UE relay architecture, data is transferred from one remote UE (UE 1) to another remote UE (UE 2) via an intermediate relay UE using a protocol stack, where the upper layers of the protocol stack (e.g., the Service Data Adaptation Protocol (SDAP) layer and the Packet Data Convergence Protocol (PDCP) layer) are end-to-end (i.e., terminated between the remote UEs), while the lower layers (e.g., the Radio Link Control (RLC) layer, the Media Access Control (MAC) layer, and the Physical (PHY) layer) are hop-by-hop (i.e., terminated between each remote UE and the relay UE). This means that the remote UEs exchange data with the relay UE via one or more channels (e.g., RLC channels) managed in the lower layer, and they exchange data with another remote UE via one or more bearers (e.g., the SL Radio Bearer (SLRB)) managed in the upper layer. To correctly route data from the source remote UE to the destination remote UE, the relay UE needs to know the relationship between the upper layer bearer (or the path the bearer takes through the relay system) and the lower layer channels, so that the relay UE can map incoming transmissions (e.g., data packets received from a remote UE on an incoming RLC channel) to outgoing transmissions (e.g., data packets sent to a remote UE on an outgoing RLC channel). To make this mapping unambiguous, the identifier for the upper layer bearer / path should be unique within the scope of the relay UE. Therefore, it is very necessary for the relay UE and the remote UEs to have a coordinated way to allocate and manage the identifiers for end-to-end communication. Summary of the Invention

[0006] In a first aspect of the present application, a method performed by a relay UE is provided. The method includes the following steps: establishing a first Radio Link Control (RLC) channel between a first remote UE and the relay UE, where the first RLC channel is associated with a first end-to-end identifier; establishing a second RLC channel between a second remote UE and the relay UE, where the second RLC channel is associated with the first end-to-end identifier or a second end-to-end identifier; receiving an incoming sidelink transmission from the first remote UE on the first RLC channel, where the incoming sidelink transmission includes the first end-to-end identifier; and sending an outgoing sidelink transmission to the second remote UE on the second RLC channel, where the outgoing sidelink transmission includes one of the first end-to-end identifier and the second end-to-end identifier.

[0007] In an implementation form of the first aspect of the present application, the outgoing side link transmission includes a first end-to-end identifier in response to the second RLC channel being associated with the first end-to-end identifier. The method further includes the step of determining a mapping of the first RLC channel to a second RLC channel for the outgoing side link transmission based on the first end-to-end identifier.

[0008] In another implementation form of the first aspect of the present application, the outgoing side link transmission includes a second end-to-end identifier in response to the second RLC channel being associated with the second end-to-end identifier. The method further includes the step of determining a mapping of the first RLC channel to a second RLC channel for the outgoing SL transmission based on the first end-to-end identifier. The first end-to-end identifier may include the SL Radio Bearer (SLRB) ID and information of the second remote UE, and the second end-to-end identifier may include the SLRB ID and information of the first remote UE. For example, the information of the first remote UE may include the first UE ID of the first remote UE, and the information of the second remote UE may include the second UE ID of the second remote UE.

[0009] In another implementation form of the first aspect of the present application, the first RLC channel between the first remote UE and the relay UE is established by: receiving a first reconfiguration message from the first remote UE; and sending a first reconfiguration complete message to the first remote UE. The first end-to-end identifier is indicated in the first reconfiguration message or the first reconfiguration complete message.

[0010] In another implementation form of the first aspect of the present application, the second RLC channel between the second remote UE and the relay UE is established by: sending a second reconfiguration message to the second remote UE; and receiving a second reconfiguration complete message from the second remote UE. The first end-to-end identifier is indicated in the second reconfiguration complete message in response to the second RLC channel being associated with the first end-to-end identifier, or the second end-to-end identifier is indicated in the second reconfiguration complete message in response to the second RLC channel being associated with the second end-to-end identifier. Alternatively, the first end-to-end identifier is indicated in the second reconfiguration message in response to the second RLC channel being associated with the first end-to-end identifier, or the second end-to-end identifier is indicated in the second reconfiguration message in response to the second RLC channel being associated with the second end-to-end identifier.

[0011] In a second aspect of the present application, a method performed by a first remote UE is provided. The method includes the following steps: establishing an RLC channel between the first remote UE and a relay UE, where the RLC channel is associated with an end-to-end identifier; after establishing the RLC channel, establishing an SLRB between the first remote UE and a second remote UE, where the SLRB is associated with the end-to-end identifier; and after establishing the SLRB, sending an SL transmission for the second remote UE on the RLC channel, where the SL transmission includes the end-to-end identifier.

[0012] In an implementation form of the second aspect of the present application, the RLC channel between the first remote UE and the relay UE is established by: sending a first reconfiguration message to the relay UE; and receiving a first reconfiguration complete message from the relay UE. The first remote UE may determine the end-to-end identifier and indicate the end-to-end identifier in the first reconfiguration message. Alternatively, the end-to-end identifier may be indicated in the first reconfiguration complete message.

[0013] In another implementation form of the second aspect of the present application, the SLRB between the first remote UE and the second remote UE is established by: sending a second reconfiguration message to the second remote UE via the relay UE; and receiving a second reconfiguration complete message from the second remote UE via the relay UE.

[0014] In another implementation form of the second aspect of the present application, the end-to-end identifier includes an SLRB ID and information of the second remote UE. For example, the information of the second remote UE includes the UE ID of the second remote UE.

[0015] The present invention proposes a device and method for sidelink communication, which realizes the beneficial effect of improving the transmission service quality by using the end-to-end identifier.

[0016] Other aspects and features of the present application will become apparent to those skilled in the art upon reading the following description of specific embodiments of the method for SL communication in a UE-to-UE relay architecture. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present application can be more fully understood by reading the following detailed description and examples with reference to the accompanying drawings, in which:

[0018] Figure 1 is a block diagram showing an exemplary user plane protocol stack for a Layer 2 UE-to-UE relay architecture according to an embodiment of the present application;

[0019] Figure 2 is a block diagram of a UE according to an embodiment of the present application;

[0020] Figure 3is a schematic diagram showing the relationship between the SLRB and the RLC channels in an exemplary Layer 2 UE-to-UE relay architecture;

[0021] Figure 4 is a schematic diagram showing the mapping of the SLRB to the RLC channels according to an embodiment of Figure 3 ;

[0022] Figure 5 is a message sequence diagram showing the connection establishment process in the UE-to-UE relay architecture according to an embodiment of the present application;

[0023] Figure 6 is a message sequence diagram showing the establishment of the RLC channel and the SLRB in the UE-to-UE relay architecture according to an embodiment of the present application;

[0024] Figure 7 is a flowchart showing a method for supporting SL communication for a relay UE in a UE-to-UE relay architecture according to an embodiment of the present application; and

[0025] Figure 8 is a flowchart showing a method for supporting SL communication for a first remote UE in a UE-to-UE relay architecture according to an embodiment of the present application. Detailed Description

[0026] The following description is intended to illustrate the basic principles of the present application and should not be considered limiting. It should be understood that the embodiments can be implemented in software, hardware, firmware, or any combination thereof. The terms "comprising", "comprises", "including", and / or "includes", when used herein, specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

[0027] Figure 1 is a block diagram showing an exemplary user plane protocol stack for a Layer 2 UE-to-UE relay architecture according to an embodiment of the present application.

[0028] As Figure 1 shown, the user plane protocol stack for a remote UE may include an SDAP layer, a PDCP layer, an adaptation layer, an RLC layer, a MAC layer, and a Physical (PHY) layer. All of these layers except the adaptation layer can be modeled in the layers that have been developed for SL communication in Release 16 of the 3GPP specifications. The adaptation layer is dedicated to the relay environment and has the function of mapping the upper layer bearers to the lower layer channels in a manner that supports forwarding through the relay UE. Specifically, the SDAP and PDCP layers are end-to-end (i.e., terminated between remote UEs), while the adaptation layer, RLC, MAC, and PHY layers are hop-by-hop (i.e., terminated between one remote UE and the relay UE).

[0029] It should be understood that Figure 1 the protocol stack shown is for illustrative purposes only and is not intended to limit the scope of the present application. The protocol stack can be replicated across different sets of UEs, such that for example a single relay UE can have multiple peers (remote UEs) in any combination of corresponding ones. In one example, remote UE 1 can communicate with both remote UE 2 and remote UE 3 via the same relay UE. In such a case, UE 1 and UE 2 will instantiate a first set of protocol stacks, while UE 1 and UE3 will instantiate a second set of protocol stacks.

[0030] Although not shown, the control plane protocol stack for the UE-to-UE relay architecture can be similar, except that the SDAP layer should be omitted and a control protocol layer (e.g., the PC5 Radio Resource Control (PC5-RRC) layer) should be added above the PDCP layer.

[0031] In the layer 2 UE-to-UE relay architecture, there are two different levels of "bearer" or "channel" constructs, where "channel" can refer to the RLC channel managed by the RLC layer and used to connect the remote UE and the relay UE, and "bearer" can refer to the SLRB managed by the PDCP layer and used to connect the remote UE and another remote UE.

[0032] Figure 2 is a block diagram of a UE according to an embodiment of the present application.

[0033] In an embodiment, the UE can refer to a relay UE or a remote UE (i.e., the transmitting remote UE or the receiving remote UE in the UE-to-UE relay architecture).

[0034] As Figure 2 shown, the UE can include a wireless transceiver 10, a controller 20, a storage device 30, a display device 40, and an input / output (I / O) device 50.

[0035] The wireless transceiver 10 can be configured to perform wireless transmission and reception to other UEs and / or to a base station (BS) in a cellular network (e.g., a 5G NR network) and from the UE and / or the BS.

[0036] Specifically, the wireless transceiver 10 can include a baseband processing device 11, a radio frequency (RF) device 12, and an antenna 13. The antenna 13 can include an antenna array for beamforming.

[0037] The baseband processing device 11 is configured to perform baseband signal processing and control the communication between a subscriber identity module (not shown) and the RF device 12. The baseband processing device 11 may include a plurality of hardware components to perform baseband signal processing, including analog-to-digital conversion (ADC) / digital-to-analog conversion (DAC), gain adjustment, modulation / demodulation, encoding / decoding, and so on.

[0038] The RF device 12 may receive an RF wireless signal via the antenna 13, convert the received RF wireless signal into a baseband signal, which is processed by the baseband processing device 11, or the RF device 12 receives a baseband signal from the baseband processing device 11, converts the received baseband signal into an RF wireless signal, and then transmits it via the antenna 13. The RF device 12 may also include a plurality of hardware devices to perform radio frequency conversion. For example, the RF device 12 may include a mixer for multiplying the baseband signal by a carrier oscillating at a radio frequency in the supported RAT, where the radio frequency may be any radio frequency used in 5G NR technology (e.g., millimeter wave 30 GHz to 300 GHz), 900 MHz, 2100 MHz, or 2.6 GHz used in LTE / LTE-A / TD-LTE technology, or other radio frequencies depending on the RAT used.

[0039] The controller 20 may be a general-purpose processor, a micro control unit (MCU), an application processor, a digital signal processor (DSP), a graphics processing unit (GPU), a holographic processing unit (HPU), a neural processing unit (NPU), etc., which includes various circuits providing the following functions: data processing and computing, controlling the wireless transceiver 10 to communicate wirelessly with other UEs and / or BSs, storing data (e.g., program code) in the storage device 30 and retrieving data (e.g., program code) from the storage device 30, sending a series of frame data (e.g., represented as text messages, graphics, images, etc.) to the display device 40, and receiving user input signals or output signals via the I / O device 50.

[0040] Specifically, the controller 20 may coordinate the above operations of the wireless transceiver 10, the storage device 30, the display device 40, and the I / O device 50 for performing the method of SL communication in the UE-to-UE relay architecture.

[0041] In another embodiment, the controller 20 may be incorporated into the baseband processing device 11 to serve as a baseband processor.

[0042] As will be understood by those skilled in the art, the circuitry of the controller 20 will typically include transistors configured in a manner to control the operation of the circuitry in accordance with the functions and operations described herein. It will be further understood that the specific structure or interconnection of the transistors will typically be determined by a compiler, such as a Register Transfer Language (RTL) compiler. The RTL compiler may operate on a script that is very similar to an assembly language code to compile the script into a form used for the layout or fabrication of the final circuit. In fact, RTL is well-known for its role and use in facilitating the design flow of electronic and digital systems.

[0043] The storage device 30 may be a non-transitory machine-readable storage medium, including a memory (e.g., flash memory or non-volatile random access memory (NVRAM)), a magnetic storage device (e.g., a hard disk drive or magnetic tape), an optical disk, or any combination thereof, for storing Figure 1 the applications shown, communication protocols (e.g., communication protocols for communicating with the 5G NR network 120), and / or instructions and / or program code for the method of SL communication in the UE-to-UE relay architecture.

[0044] The display device 40 may be a liquid-crystal display (LCD), a light-emitting diode (LED) display, an electronic paper display (EPD), etc., for providing a display function. Alternatively, the display device 40 may further include one or more touch sensors disposed thereon or thereunder for sensing contact, connection, or proximity of an object (e.g., a finger or a stylus).

[0045] The I / O device 50 may include one or more buttons, a keyboard, a mouse, a touchpad, a camera, a microphone, and / or a speaker, etc., to serve as a man-machine interface (MMI) for interacting with the user.

[0046] It should be understood that Figure 2The components described in the embodiments are for illustrative purposes only and are not intended to limit the scope of the present application. For example, the UE may include more components, such as a power supply and / or a Global Positioning System (GPS) device, where the power supply may be a mobile / replaceable battery that provides power to all other components of the UE, and the GPS device may provide the location information of the UE for use in some location-based services or applications. Alternatively, the UE may include fewer components. For example, the UE may not include the display device 40 and / or the I / O device 50.

[0047] Figure 3 is a schematic diagram showing the relationship between the SLRB and the RLC channels in an exemplary Layer 2 UE-to-UE relay architecture.

[0048] As Figure 3 shown, there are three remote UEs and one relay UE serving these remote UEs. Specifically, remote UE1 and remote UE 2 communicate with each other on a single SLRB (denoted as SLRB D(1, 2) in Figure 3 ), and remote UE 1 and remote UE 3 communicate with each other on three different SLRBs (denoted as SLRB A(1, 3), SLRB B(1, 3), and SLRB C(1, 3) in Figure 3 ). Although these SLRBs are shown as directly connecting the remote UEs to each other, it should be understood that the actual data transfer on these end-to-end bearers is through the relay UE.

[0049] In addition, the relay UE and these remote UEs communicate based on various RLC channels. For example, remote UE 1 and the relay UE communicate on two RLC channels (denoted as W(1, R) and X(1, R) in Figure 3 ), remote UE 2 and the relay UE communicate on a single RLC channel (denoted as V(2, R) in Figure 3 ), and remote UE 3 and the relay UE communicate on two RLC channels (denoted as Y(3, R) and Z(3, R) in Figure 3 ).

[0050] Figure 3 The mapping of SLRB to RLC channels in the embodiments of Figure 4 can be further as Figure 4As shown, SLRB D(1, 2) is mapped to RLC channels W(1, R) and V(2, R); SLRB A(1, 3) is mapped to RLC channels W(1, R) and Y(3, R); SLRB B(1, 3) is mapped to RLC channels X(1, R) and Y(3, R); SLRB C(1, 3) is mapped to RLC channels X(1, R) and Z(3, R).

[0051] It should be noted that the SLRB does not necessarily have a globally unique ID. That is, it is not assumed that the identifiers A / B / C / D directly correspond to any distinguishable values known to all UEs. According to the 3GPP specifications for SL communication, each remote UE has a set of identifiers for its bearers with a given peer (for the receiving UE, these identifiers are given by the information element SLRB-PC5-ConfigIndex in the RRCReconfigurationSidelink message when the bearer is set), but the indices of these identifiers may conflict for different UEs. For example, in Figures 3 - 4 the scenario, remote UE 2 may have the index 1 associated with SLRB D, while remote UE 3 may have the index 1 associated with SLRB A. Now consider a packet arriving at the relay UE from remote UE 1 on the ingress RLC channel W(1, R). According to Figure 4 the mapping in the scenario, this packet may be associated with either SLRB D or SLRB A. In order to forward the packet to the correct recipient on the correct egress RLC channel, the relay UE must determine which SLRB is involved. However, since the logical channel only corresponds to the RLC channels to which multiple SLRBs are mapped, the relay UE cannot make a determination based solely on the SL logical channel ID (Logical Channel ID, LCID).

[0052] In a novel aspect of the present application, an end-to-end identifier is indicated to the relay UE together with each packet, where the end-to-end identifier specifically refers to information that can help the relay UE eliminate the routing ambiguity of the packets received on a specific RLC channel.

[0053] To further clarify, the end-to-end identifier can be negotiated between the relay UE and the remote UE when the RLC channel and / or SLRB is established. The end-to-end identifier can be indicated in the adaptation layer, for example, as part of the adaptation layer header or sub-header associated with the data packet. Alternatively, since the layers below the adaptation layer are processed in the relay UE when a packet is received, the end-to-end identifier can be indicated in any underlying layer, such as indicating the SL LCID in the MAC layer.

[0054] For example, if an end-to-end identifier is indicated at the MAC layer, it can be understood as an extension of the LCID space. In this case, the transmitting remote UE can indicate the SL LCID and the "extended LCID" corresponding to a specific RLC channel pair at the MAC layer (e.g., in the MAC sub-header). In Figure 4 the scenario of, an extended LCID can be assigned to the RLC channel W (inlet) and RLC channel V (outlet) pair, and another extended LCID can be assigned to the RLC channel W (inlet) and RLC channel Y (outlet) pair. The relay UE can process the extended LCID to determine the outlet RLC channel.

[0055] In addition, the end-to-end identifier may also need to be provided to the receiving remote UE. For example, in Figure 4 the scenario of, considering a packet arriving at remote UE 3 on RLC channel Y, remote UE 3 needs to determine whether the packet it is receiving is for SLRB A or SLRB B. Since each LCID corresponds to an RLC channel and two SLRBs are mapped to the relevant RLC channel (i.e., RLC channel Y), the known LCID does not provide sufficient information. Therefore, it may be necessary for the relay UE to transmit the end-to-end identifier together with the data packet to the receiving remote UE.

[0056] In one embodiment, the end-to-end identifier can be a combination of the SLRB ID and information of the transmitting remote UE and / or the receiving remote UE (e.g., layer 2 UE ID, MAC address). Specifically, in Figure 4 the scenario of, the end-to-end identifier can be assigned separately for each RLC channel, such that a packet arriving at the relay UE on SLRB D of RLC channel W can be accompanied by an end-to-end identifier value that is different from the end-to-end identifier value of the same packet transmitted by the relay UE on SLRB D of RLC channel V. For example, remote UE 1 can transmit a packet with an end-to-end identifier on RLC channel W, where the end-to-end identifier includes the SLRB ID (e.g., SLRB D) and the UE ID of the receiving remote UE (e.g., remote UE 2). The relay UE can determine the outlet RLC channel as RLC channel V based on the end-to-end identifier, and before forwarding the packet with the end-to-end identifier, replace the UE ID in the end-to-end identifier with the UE ID of the transmitting end remote UE (i.e., remote UE 1).

[0057] In another embodiment, the end-to-end identifier can be a path identifier maintained at the relay UE, which corresponds to a specific pair of RLC channels and thus represents the transmission path between two remote UEs. That is, the end-to-end identifier can be common throughout the transmission path. For example, inFigure 4 In the scenario of , the packets sent on the SLRB D can be assigned the same end-to-end identifier on the RLC channel W (for transmission from the remote UE 1 to the relay UE) and the RLC channel V (for transmission from the relay UE to the remote UE 2). The transmission path can be determined before or at the time of establishing the SLRB (by the relay UE, or through negotiation between the relay UE and one or more remote UEs), and a path ID (which must be unique at the relay UE) can be assigned to reflect the applicable RLC channels. Therefore, at the time of SLRB establishment, the path ID will be associated with the SLRB, and each packet transmitted on the SLRB will be accompanied by the corresponding path ID included in the protocol layer visible to the relay UE (e.g., the adaptation layer). For example, the UE initiating the SLRB establishment (e.g., the remote UE) can indicate the corresponding path ID in the RRC reconfiguration sidelink (RRCReconfigurationSidelink) message to establish one or more RLC channels carrying the SLRB, or the responding UE (e.g., the relay UE) can indicate the path ID in the RRC reconfiguration complete sidelink (RCReconfigurationCompleteSidelink) message acknowledging the establishment of one or more RLC channels carrying the SLRB. It should be noted that different from the design used in Integrated Access and Backhaul (IAB) following Release 16 of the 3GPP specifications, where the destination and path ID are included in the header of the Backhaul Adaptation Protocol (BAP) protocol data unit (PDU), the end-to-end identifier used in this application only needs to include the path ID, and it is sufficient for the relay UE to determine the egress RLC channel to allow the relay UE to forward the packet to the correct destination UE.

[0058] Figure 5 is a message sequence diagram showing the connection establishment process in the UE-to-UE relay architecture according to an embodiment of the present application.

[0059] In the UE-to-UE relay architecture, the connection establishment process can be initiated by a remote UE that wants to send data to another remote UE. In an embodiment, it is the remote UE 1 that initiates the connection establishment process because it wants to send data to the remote UE 2.

[0060] In step the remote UE 1 sends a direct communication (DC) request message (e.g., via broadcast) to the relay UE and performs an authentication and security process with the relay UE.

[0061] In steps S503 - S504, the relay UE forwards a DC request message to remote UE 2 (e.g., by broadcasting), and performs an authentication and security process with remote UE 2.

[0062] In steps S505 - S506, the relay UE receives a first DC acceptance message from remote UE 2, and sends a second DC acceptance message to remote UE 1.

[0063] At this time, an end - to - end relay transmission with hop - by - hop security is established and available after remote UE 1 receives the second DC acceptance message.

[0064] In steps S507 - S508, remote UE 1 and remote UE 2 perform an authentication and security process, and remote UE 1 receives a DC acceptance message from remote UE 2 through the end - to - end relay transmission.

[0065] At this time, an end - to - end secure PC5 - S connection is established and available for subsequent RLC channel and SLRB establishment. Note that the PC5 - S connection between remote UE 1 and remote UE 2 passes through the relay UE, but the security is assumed to be end - to - end, so the relay UE cannot read the content of the data packets or signaling messages being exchanged between these two remote UEs.

[0066] Figure 6 It is a message sequence diagram showing the establishment of the RLC channel and SLRB in the UE - to - UE relay architecture according to an embodiment of the present application.

[0067] In an embodiment, the establishment of the RLC channel and SLRB occurs after the connection establishment process described in the embodiment as Figure 5 to provide an end - to - end secure PC5 - S connection between remote UE 1 and remote UE 2.

[0068] In step S601, remote UE 1 sends a first RRCReconfigurationSidelink message to the relay UE, requesting to establish an RLC channel for communication between remote UE 1 and the relay UE. The first RRCReconfigurationSidelink message may include configurations for only certain protocol layers (e.g., only the underlying layer terminated between remote UE 1 and the relay UE). For Figure 1The protocol stack shown, which means that the first RRCReconfigurationSidelink message can include configurations of the PHY, MAC, RLC, and adaptation layers. In some embodiments, the first RRCReconfigurationSidelink message can also indicate one or more values of the end-to-end identifier to be mapped to the RLC channel configured by the first RRCReconfigurationSidelink message (e.g., in Figure 4 the scenario of “establish RLC channel W, which will carry SLRB A”). In other words, the end-to-end identifier value can be assigned by the initiating / transmitting remote UE. The first RRCReconfigurationSidelink message can also indicate the destination of the SLRB to be established, so that the relay UE can trigger the establishment of the RLC channel with the destination / receiving remote UE. The first RRCReconfigurationSidelink message can also indicate one or more parameters of the SLRB to be established, so that the relay UE can infer the applicable parameters for configuring the RLC channel with the destination / receiving remote UE.

[0069] In step S602, the relay UE responds with a first RRCReconfigurationCompleteSidelink message indicating that the reconfiguration requested in step S601 has been executed. In some embodiments, the first RRCReconfigurationCompleteSidelink message can indicate one or more values of the end-to-end identifier to be mapped to the RLC channel configured by the first RRCReconfigurationSidelink message. In other words, the end-to-end identifier value can be assigned by the relay UE instead of the initiating / transmitting remote UE.

[0070] In step S603, the relay UE sends a second RRCReconfigurationSidelink message to the remote UE 2 to establish one or more RLC channels for communication between the relay UE and the remote UE 2. The second RRCReconfigurationSidelink message may include configurations for only certain protocol layers (e.g., the layers terminated between the relay and the remote UE 2). In some embodiments, the second RRCReconfigurationSidelink message may also indicate one or more values of the end-to-end identifier to be mapped to the RLC channels configured by the second RRCReconfigurationSidelink message (e.g., "establish RLC channel Y, which will carry SLRB A"). The end-to-end identifier values indicated in the second RRCReconfigurationSidelink message may be the same as or different from the end-to-end identifier values assigned in steps S601 - S602 for the same SLRB.

[0071] In step S604, the remote UE 2 sends a second RRCReconfigurationCompleteSidelink message to the relay UE, indicating that the reconfiguration requested in step S603 has been performed. In some embodiments, the second RRCReconfigurationCompleteSidelink message may also indicate one or more values of the end-to-end identifier to be mapped to the RLC channels configured by the second RRCReconfigurationSidelink message. The end-to-end identifier values indicated in the second RRCReconfigurationCompleteSidelink message may be the same as or different from the end-to-end identifier values assigned in steps S601 - S602 for the same SLRB.

[0072] In step S605, the remote UE 1 sends a third RRCReconfigurationSidelink message to the remote UE 2 (via the relay UE, using the secure PC5-S connection between the remote UE 1 and the remote UE 2). The third RRCReconfigurationSidelink message may include configurations for only certain protocol layers (e.g., the upper layers terminated between the remote UEs). In Figure 1In the protocol stack shown, this means that the third RRCReconfigurationSidelink message may only include configurations of the PDCP and SDAP layers. The third RRCReconfigurationSidelink message may configure one or more SLRBs between the remote UE1 and the remote UE 2, which may be mapped to the RLC channels configured in steps S601 and S603.

[0073] In step S606, the remote UE 2 sends a third RRCReconfigurationCompleteSidelink message to the remote UE 1, indicating that the reconfiguration requested in step S605 has been completed.

[0074] It should be noted that, in Figure 6 the embodiment of, when establishing the RLC channels in steps S601 to S604, the SLRB does not exist yet. That is to say, steps S601 to S604 include configuring transmissions for non-existent bearers, assuming that the bearers can be established later. Alternatively, steps S605 to S606 may also be executed before step S601, that is, setting the SLRB before establishing the corresponding RLC channel. This alternative solution may result in the situation where the SLRB exists without underlying support, and before executing steps S601 to S604 and establishing the corresponding RLC channel, it will be impossible to transmit actual service traffic for the SLRB.

[0075] Figure 7 It is a flowchart of a method for a relay UE to support SL communication in a UE-to-UE relay architecture according to an embodiment of the present application.

[0076] In step S701, the relay UE establishes a first RLC channel between the first remote UE and the relay UE, where the first RLC channel is associated with a first end-to-end identifier. For example, the first RLC channel can be established through Figure 6 the RRC reconfiguration process for SL communication described in steps S601 to S602 of

[0077] In step S702, the relay UE establishes a second RLC channel between the second remote UE and the relay UE, where the second RLC channel is associated with the first end-to-end identifier or the second end-to-end identifier. For example, the second RLC channel can be established through Figure 6 the RRC reconfiguration process for SL communication described in steps S603 to S604 of

[0078] In step S703, the relay UE receives an incoming SL transmission from the first remote UE on the first RLC channel, where the incoming SL transmission includes the first end-to-end identifier.

[0079] In step S704, the relay UE sends an outgoing SL transmission to the second remote UE on the second RLC channel, where the outgoing SL transmission includes at least a data packet and one of a first end-to-end identifier and a second end-to-end identifier.

[0080] In one embodiment, the outgoing SL transmission may include at least a data packet and a first end-to-end identifier in response to the second RLC channel being associated with the first end-to-end identifier. For example, the first end-to-end identifier may be a path identifier, and the relay UE may use the path identifier to uniquely determine the mapping of the ingress RLC channel and the egress RLC channel of the SLRB between two remote UEs, and the path identifier is common throughout the transmission path.

[0081] In another embodiment, in response to the second RLC channel being associated with a second end-to-end identifier, the outgoing SL transmission may include at least a data packet and the second end-to-end identifier. For example, the first end-to-end identifier may be composed of the identifier of the SLRB carried by the first RLC channel and the second RLC channel (e.g., SLRB identifier) and information of the destination / receiving remote UE (e.g., UE ID or MAC address), while the second end-to-end identifier may be composed of the identifier of the SLRB carried by the first RLC channel and the second RLC channel (e.g., SLRB identifier) and information of the sending / originating remote UE (e.g., UE ID or MAC address). That is, the first end-to-end identifier and the second end-to-end identifier may be separately allocated for each of the first RLC channel and the second RLC channel, and the relay UE may determine the mapping of the first RLC channel to the second RLC channel for the outgoing SL transmission based on the first end-to-end identifier.

[0082] Figure 8 It is a flowchart of a method for the first remote UE to support SL communication in a UE-to-UE relay architecture according to an embodiment of the present application.

[0083] In an embodiment, the first remote UE may refer to a remote UE that initiates SL communication with another remote UE through UE-to-UE relay.

[0084] In step S801, the first remote UE establishes an RLC channel between the first remote UE and the relay UE, where the first RLC channel is associated with an end-to-end identifier. For example, the RLC channel may be established through the RRC reconfiguration process for SL communication described in steps S601 - S602 of Figure 6 The RLC channel is established through the RRC reconfiguration process for SL communication described in steps S601 - S602.

[0085] In step S802, after the RLC channel is established, the first remote UE establishes an SLRB between the first remote UE and the second remote UE, where the SLRB is associated with an end-to-end identifier. For example, the SLRB can be established through the RRC reconfiguration process for SL communication described in steps S605 - S606 of Figure 6 .

[0086] In step S803, after the SLRB is established, the first remote UE sends an SL transmission for the second remote UE on the RLC channel, where the SL transmission includes the end-to-end identifier.

[0087] In one embodiment, the first end-to-end identifier can be a path identifier, and the relay UE can use this path identifier to uniquely determine the mapping of the ingress RLC channel and the egress RLC channel for the SLRB between two remote UEs, and this path identifier is common throughout the transmission path.

[0088] In another embodiment, the end-to-end identifier can be specifically allocated for the RLC channel, and it can be composed of the SLRBID and information of the destination / receiving remote UE (e.g., UE ID or MAC address).

[0089] It should be noted that even though the foregoing embodiments are for single-hop settings, the method of the present application can also be applicable to multi-hop settings. If there are two or more relay UEs between the sending remote UE and the receiving remote UE, each relay UE needs to know how to map the end-to-end identifier to its own ingress RLC channel and egress RLC channel. This means that when the SLRB is established, they must be associated with the end-to-end identifier known to the relay UE. The relay UEs can communicate during establishment to establish a mutually agreed end-to-end identifier. Then, in order to send packets in a multi-hop setting, each relay UE applies the forwarding process as described above.

[0090] Although the present application has been described by way of example and according to preferred embodiments, it should be understood that the present application is not limited thereto. Without departing from the scope and spirit of the present application, those skilled in the art can still make various changes and modifications. Therefore, the scope of the present application should be defined and protected by the following claims and their equivalents.

[0091] The use of ordinal terms such as "first", "second", etc. in the claims to modify the claim elements themselves does not indicate that one claim element has any priority, precedence, or order relative to another claim element, or the chronological order of performing the method implementation. However, such ordinal terms like "first", "second", etc. are only used as labels to distinguish one claim element with the same name from another element with the same name (but using ordinal words), and thus to distinguish the claim elements.

Claims

1. A sidelink communication method, performed by a relay user equipment, the method comprising: Receiving an incoming sidelink transmission from a first remote user equipment on a first radio link control channel; The first radio link control channel is associated with a sidelink radio bearer identifier; The incoming sidelink transmission includes a first identifier, the first identifier including the sidelink radio bearer identifier and a first user equipment identifier; And Sending an outgoing sidelink transmission to a second remote user equipment on a second radio link control channel according to the sidelink radio bearer identifier and the first user equipment identifier.

2. The sidelink communication method according to claim 1, wherein The outgoing sidelink transmission includes the first user equipment identifier or the second user equipment identifier.

3. The sidelink communication method according to claim 2, wherein The first user equipment identifier is the user equipment identifier of the second remote user equipment, and the second user equipment identifier is the user equipment identifier of the first remote user equipment.

4. The sidelink communication method according to claim 2, wherein The first user equipment identifier is the user equipment identifier of the first remote user equipment, and the second user equipment identifier is the user equipment identifier of the second remote user equipment.

5. The sidelink communication method according to claim 1, the method further comprising: Determining the second radio link control channel for the outgoing sidelink transmission based on the sidelink radio bearer identifier.

6. The sidelink communication method according to claim 5, the method further comprising: Determining the second radio link control channel for the outgoing sidelink transmission based on the sidelink radio bearer identifier and the first user equipment identifier.

7. A sidelink communication method, performed by a first remote user equipment, the method comprising: Receiving an incoming sidelink transmission on a first radio link control channel, the first radio link control channel being associated with a sidelink radio bearer identifier, the incoming sidelink transmission including the sidelink radio bearer identifier and a first user equipment identifier; And Sending an outgoing sidelink transmission on a second radio link control channel according to the sidelink radio bearer identifier.

8. The sidelink communication method according to claim 7, wherein The outgoing sidelink transmission includes the first user equipment identifier or a second user equipment identifier.

9. The sidelink communication method according to claim 8, wherein The first user equipment identifier is the user equipment identifier of the second remote user equipment, and the second user equipment identifier is the user equipment identifier of the first remote user equipment.

10. The sidelink communication method according to claim 8, wherein, The first user equipment identifier is the user equipment identifier of the first remote user equipment, and the second user equipment identifier is the user equipment identifier of the second remote user equipment.

11. The sidelink communication method according to claim 7, wherein Determining the second radio link control channel for the outgoing sidelink transmission based on the sidelink radio bearer identifier.

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