Method and apparatus for user equipment (UE) discovery

Abstract

To provide a method and apparatus for user equipment (UE) discovery.SOLUTION: An exemplary method includes: generating a first discovery message for UE discovery; delivering the first discovery message to a PC5 signaling (PC5-S) layer of first UE; generating a PC5-S message, where the PC5-S message includes discovery information of the first discovery message; and broadcasting the PC5-S message including the discovery information via a signaling radio bearer (SRB). Embodiments of the present application can implement transmission of messages during the discovery procedure and realize a ranging-based service during the discovery procedure.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] FIELD Embodiments of the present application relate generally to wireless communication technologies, and more particularly, to a method and apparatus for user equipment (UE) discovery. [Background technology]

[0002] Sidelink communications support UE-to-UE direct communications. Sidelink communications include new radio (NR) sidelink communications and vehicle-to-everything (V2X) sidelink communications. In NR sidelink communications, an access stratum (AS) function enables at least V2X communications between two or more nearby UEs-to-UEs using NR technology but without going through any network nodes. In V2X sidelink communications, an AS function enables V2X communications between two or more nearby UEs-to-UEs using evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRA) technology but without going through any network nodes.

[0003] Before conducting sidelink communication, a UE discovery procedure may be performed in which the UE may discover other UEs or may be discovered by other UEs in the vicinity of the UE. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] 3GPP (registered trademark) specification TS 23.287 [Non-Patent Document 2] 3GPP (registered trademark) specification TS 23.285 [Non-Patent Document 3] 3GPP (registered trademark) specification TS 38.331 Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above, the industry desires improved techniques for discovery of UEs to implement message transmission during the discovery procedure and to realize ranging-based services during the discovery procedure. [Means for solving the problem]

[0006] Some embodiments of the present application at least provide a technical solution for UE discovery.

[0007] According to some embodiments of the present application, a method performed by a transmitting UE for wireless communication may include generating a first discovery message for discovery of the UE, delivering the first discovery message to a PC5 signaling (PC5-S) layer of the first UE, generating a PC5 signaling (PC5-S) message, where the PC5-S message includes discovery information of the first discovery message, and broadcasting the PC5-S message including the discovery information via a signaling radio bearer (SRB).

[0008] In an embodiment of the present application, the method may further include, in response to delivery of the discovery message to the PC5-S layer of the first UE, sending an indicator from the upper layer of the first UE to the PC5-S layer of the first UE to indicate whether the message delivered to the PC5-S layer is a discovery message.

[0009] In another embodiment of the present application, the method may further include a step of sending an indicator from an upper layer of the first UE to an access stratum (AS) layer of the first UE to indicate whether the PC5-S message includes discovery information.

[0010] In yet another embodiment of the present application, the PC5-S message containing discovery information does not contain other information that is not related to the discovery of the UE.

[0011] In yet another embodiment of the present application, the discovery information may include an indicator to indicate a type of relay. For example, the type of relay is one of a UE-to-UE relay and a UE-to-network relay. In another example, the type of relay is one of a Layer 2 (L2) relay and a Layer 3 (L3) relay.

[0012] In yet another embodiment of the present application, an SRB for transmitting PC5-S messages containing discovery information is established before PC5-S security is established.

[0013] In yet another embodiment of the present application, the SRB for transmitting PC5-S messages containing discovery information is an SRB only for transmitting PC5-S messages related to relaying.

[0014] In yet another embodiment of the present application, the discovery message is an announcement message or a solicitation message. If the discovery message is a solicitation message, the method may further include receiving at least one discovery response message from the at least one second UE in response to the solicitation message.

[0015] In yet another embodiment of the present application, the method may further include receiving, from a base station (BS), ranging information, service information of the at least one service, and a mapping relationship between the ranging information and each of the at least one service; and transmitting, in discovery information of a discovery message, the ranging information, location information of the first UE, the service information of the at least one service, and the mapping relationship.

[0016] In yet another embodiment of the present application, the method may further include receiving, from the BS, ranging information, service information of the at least one service, and a mapping relationship between the ranging information and each of the at least one service, and sending the location information of the second UE and the service information of the at least one service in the discovery information of the discovery message.

[0017] In yet another embodiment of the present application, the method may further include a step of receiving a discovery response message from a third UE, wherein location information of the third UE fulfills the location information of the second UE included in the discovery message.

[0018] In yet another embodiment of the present application, the method may further include transmitting ranging information, location information and direction information of the first UE in discovery information of the discovery message, and receiving a data transmission from the second UE in response to the first UE being a closest UE of the second UE.

[0019] In yet another embodiment of the present application, the method may further include the steps of transmitting ranging information, location information and direction information of the first UE in discovery information of a discovery message; receiving at least one discovery response message from the at least one second UE, each of the at least one discovery response message including location information of the second UE; and selecting a nearest UE from the at least one second UE based on the at least one response message.

[0020] In yet another embodiment of the present disclosure, the location information includes at least one of a zone ID and Global Positioning System (GPS) information.

[0021] According to some other embodiments of the present application, a method performed by a receiving UE for wireless communication may include, at a first UE, receiving a PC5-S message from a second UE via an SRB; delivering the PC5-S message to a PC5-S layer, where the PC5-S message includes discovery information of the discovery message for discovery of the UE; and delivering the discovery message to an upper layer by the PC5-S layer.

[0022] In an embodiment of the present application, the PC5-S message containing discovery information does not contain other information that is not related to the discovery of the UE.

[0023] In another embodiment of the present application, the discovery information may include an indicator to indicate a type of relay. For example, the type of relay is one of a UE-to-UE relay and a UE-to-network relay. In another example, the type of relay is one of a Layer 2 (L2) relay and a Layer 3 (L3) relay.

[0024] In yet another embodiment of the present application, the SRB is established before PC5-S security is established.

[0025] In yet another embodiment of the present application, the SRB is an SRB only for transmitting PC5-S messages related to relaying.

[0026] In yet another embodiment of the present application, the discovery message is an announcement message or a request message. If the discovery message is a request message, the method may further include transmitting a discovery response message in response to the request message.

[0027] In yet another embodiment of the present application, the method may further include receiving, in discovery information of the discovery message, ranging information, location information of the second UE, service information of the at least one service, and a mapping relationship between the ranging information and each of the at least one service, and determining whether to select the second UE based on the discovery information.

[0028] In yet another embodiment of the present application, the method may further include receiving location information of a third UE and service information of the at least one service in discovery information of the discovery message, and transmitting a discovery response message in response to the location information of the first UE satisfying the location information of the third UE included in the discovery message.

[0029] In yet another embodiment of the present application, the method may further include receiving location information of the second UE in discovery information of the discovery message, and determining whether to allow the second UE to access based on a configuration from the BS.

[0030] In yet another embodiment of the present application, the method may further include receiving location information of the second UE in discovery information of the discovery message, and transmitting the discovery information including the location information to the BS.

[0031] In yet another embodiment of the present application, the method may further include: receiving at least one second discovery message from at least one second UE, where the at least one second discovery message includes the discovery message, and each of the at least one second discovery message includes ranging information, location information, and direction information of the discovery information of the discovery message, and selecting a nearest UE from the at least one second UE based on the at least one discovery message.

[0032] In yet another embodiment of the present application, the method may further include the steps of receiving ranging information, location information and direction information of the second UE in discovery information of a discovery message, and transmitting a discovery response message in response to the location information and direction information of the first UE satisfying the ranging information and direction information of the second UE, wherein the discovery response message includes the location information of the first UE.

[0033] In yet another embodiment of the present disclosure, the location information includes at least one of a zone ID and Global Positioning System (GPS) information.

[0034] Some embodiments of the present disclosure also provide an apparatus including at least one non-transitory computer-readable medium having computer-executable instructions stored thereon, at least one receiving circuit, at least one transmitting circuit, and at least one processor coupled to the at least one non-transitory computer-readable medium, the at least one receiving circuit, and the at least one transmitting circuit, the computer-executable instructions being programmed to use the at least one receiving circuit, the at least one transmitting circuit, and the at least one processor to implement any of the methods described above.

[0035] The embodiments of the present application provide technical solutions for UE discovery, to implement message transmission during the discovery procedure, and to realize ranging-based services during the discovery procedure.

[0036] To explain how the advantages and features of the present application may be obtained, the application will be described by reference to specific embodiments thereof that are illustrated in the accompanying drawings. These drawings depict only exemplary embodiments of the present application and therefore should not be considered as limiting its scope. [Brief description of the drawings]

[0037] [Figure 1] FIG. 1 is a schematic diagram of a wireless communication system 100 according to some embodiments of the present application. [Diagram 2] 2 is a schematic diagram of a wireless communication system 200 according to some embodiments of the present application. [Diagram 3] 1 is a schematic diagram of a wireless communication system 300 according to some embodiments of the present application. [Figure 4] FIG. 2 illustrates an exemplary model A ProSe direct discovery procedure according to some embodiments of the present application. [Diagram 5] FIG. 1 illustrates an exemplary model B ProSe direct discovery procedure according to some embodiments of the present application. [Figure 6] FIG. 1 illustrates an exemplary PC5 signaling (PC5-S) protocol stack according to some embodiments of the present application. [Figure 7] 1 is a flow diagram illustrating a method for UE discovery according to some embodiments of the present application. [Figure 8] FIG. 2 illustrates an example Layer 2 UE-to-UE relay protocol stack in accordance with some embodiments of the present application. [Figure 9] FIG. 2 illustrates an example discovery protocol stack in accordance with some other embodiments of the present application. [Figure 10] 10 is a simplified block diagram of an apparatus 1000 for UE discovery according to some embodiments of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] The detailed description of the accompanying drawings is intended as an illustration of a preferred embodiment of the present application, and is not intended to represent the only form in which the present application may be practiced. It is to be understood that the same or equivalent functions may be accomplished by different embodiments that are intended to be encompassed within the spirit and scope of the present application.

[0039] Reference will now be made in detail to some embodiments of the present application, examples of which are illustrated in the accompanying drawings. For ease of understanding, the embodiments are provided under specific network architectures and new service scenarios, such as Third Generation Partnership Project (3GPP®) 5G (NR), 3GPP® Long Term Evolution (LTE) Release 8, etc. It is believed that with the development of network architectures and new service scenarios, all the embodiments of the present application are also applicable to similar technical problems, and further, the terms described in the present application may change, which should not affect the principles of the present application.

[0040] FIG. 1 illustrates a schematic diagram of a wireless communication system 100 in accordance with some embodiments of the present application.

[0041] As shown in FIG. 1, the wireless communication system 100 may support sidelink communication. Sidelink communication supports UE-to-UE direct communication. In the context of this application, sidelink communication may be categorized according to the wireless communication technology employed. For example, sidelink communication may include NR sidelink communication and V2X sidelink communication.

[0042] NR sidelink communication may refer to an AS function that enables at least V2X communication as defined in 3GPP® specification TS 23.287, from nearby UE to nearby UE, using NR technology, but without going through any network node. V2X sidelink communication may refer to an AS function that enables V2X communication as defined in 3GPP® specification TS 23.285, from nearby UE to nearby UE, using E-UTRA technology, but without going through any network node. However, unless otherwise noted, "sidelink communication" may refer to NR sidelink communication, V2X sidelink communication, or any sidelink communication employing other wireless communication technology.

[0043] 1, wireless communication system 100 may include a number of base stations (e.g., BS 102 and BS 103) and a number of UEs (e.g., UE 101A, UE 101B, and UE 101C). Although a particular number of UEs and BSs are depicted in FIG. 1, it is contemplated that any number of UEs and BSs may be included in wireless communication system 100.

[0044] The UE and BS may support communication based on, for example, 3G, Long Term Evolution (LTE), LTE-Advanced (LTE-A), New Radio (NR), or other suitable protocols. In some embodiments of the present application, the BS (e.g., BS 102 or BS 103) may be referred to as an access point, access terminal, base, base unit, macro cell, Node-B, evolved Node B (eNB), gNB, ng-eNB, home Node-B, relay node, or device, or described using other terms used in the art. The UE 101 may include, for example, but is not limited to, a computing device, a wearable device, a mobile device, an IoT device, a vehicle, and the like. Those skilled in the art will understand that as technology develops and advances, the terms described in the present application may change, but should not affect or limit the principles and spirit of the present application.

[0045] In the example of Figure 1, BS 102 and BS 103 may be included in a next generation radio access network (NG-RAN). In an embodiment of the present application, BS 102 may be a gNB and BS 103 may be a ng-eNB.

[0046] UE 101A and UE 101B may be within the coverage of an NG-RAN. For example, as shown in FIG. 1, UE 101A may be within the coverage of BS 102 and UE 101B may be within the coverage of BS 103. UE 101C may be outside the coverage of an NG-RAN. For example, as shown in FIG. 1, UE 101C may be outside the coverage of all BSs, for example, both BS 102 and BS 103. UE 101A and UE 101B may connect to BS 102 and BS 103, respectively, via a network interface, for example, a Uu interface defined in a 3GPP® standard document. BS 102 and BS 103 may be connected to each other via a network interface, for example, an Xn interface defined in a 3GPP® standard document. UE 101A, UE 101B, and UE 101C may be respectively connected to each other via a PC5 interface defined in 3GPP® standard documents.

[0047] Support for V2X services over the PC5 interface may be provided, for example, by NR sidelink communication and / or V2X sidelink communication. NR sidelink communication may support one of three types of transmission models for a Source Layer-2 ID and Destination Layer-2 ID pair: unicast transmission, groupcast transmission, and broadcast transmission. Sidelink communication transmission and reception over the PC5 interface is supported when the UE is within the coverage of the NG-RAN and when the UE is outside the coverage of the NG-RAN. For example, UE 101A within the coverage of BS 102 may perform sidelink transmission and reception (e.g., sidelink unicast transmission, sidelink groupcast transmission, or sidelink broadcast transmission) over the PC5 interface. UE 101C outside the coverage of both BS 102 and BS 103 may also perform sidelink transmission and reception over the PC5 interface.

[0048] A UE that supports sidelink and / or V2X communications may be referred to as a V2X UE, which may be a cell phone, a vehicle, a road map device, a computer, a laptop, an IoT (Internet of Things) device, or other type of device, according to some other embodiments of the present application.

[0049] A V2X UE can operate in different modes. At least two sidelink resource allocation modes are defined for sidelink communication. For example, mode 1 may refer to a situation where the base station schedules sidelink resources to be used by the UE for sidelink transmission, and mode 2 may refer to a situation where the UE determines the sidelink transmission resources and timing in a resource pool. The resource pool may be configured by the base station or the network, or may be pre-configured according to a standard. In mode 2, the base station may not need to dynamically schedule sidelink resources for the UE, and the UE may determine the sidelink transmission resources and timing in the resource pool based on, for example, measurement and sensing results.

[0050] In Mode 1, the UE may need to be in RRC_CONNECTED state to transmit data. The base station can dynamically schedule resources to the UE via a Physical Downlink Control Channel (PDCCH) for NR sidelink communications.

[0051] In Mode 2, the UE can transmit data when the UE is in coverage of the NG-RAN or when the UE is out of coverage of the NG-RAN. The UE may autonomously select a sidelink grant from a resource pool provided by system information (e.g., System Information Block (SIB)) or dedicated signaling while the UE is in coverage of a BS, or from a pre-configured resource pool while the UE is out of coverage of all BSs.

[0052] For NR sidelink communications, a resource pool may be provided for a given validity area without the UE needing to acquire a new resource pool while moving within the validity area, at least when this pool is provided by a SIB (e.g., the reuse valid area of ​​the NR SIB). The UE may be allowed to temporarily use a UE autonomous resource selection method with random selection for sidelink transmissions based on the configuration of an exceptional transmission resource pool defined in 3GPP specification TS 38.331.

[0053] FIG. 2 illustrates a schematic diagram of a wireless communication system 200 in accordance with some embodiments of the present application.

[0054] 2, the wireless communication system 200 may include one BS (e.g., BS 202) and several UEs (e.g., UE 201A and UE 201B). UE 201B may be within the coverage of BS 202, and UE 201A may be out of coverage. Although a particular number of UEs and BSs are depicted in FIG. 2, it is contemplated that any number of UEs may be included in the wireless communication system 200.

[0055] The wireless communication system 200 may support sidelink communication. For example, the UE 201B may communicate sidelink with the UE 201A. The UE 201A may be out of coverage of the BS 202 but access the BS 202 via the UE 201B. Thus, the UE 201A and the BS 202 may establish a radio resource control (RRC) connection between them, and the UE 201A may have an RRC state such as an RRC_IDLE state, an RRC_INACTIVE state, and an RRC_CONNECTED state. In the context of this application, a UE (e.g., the UE 201B) that acts as a relay between the UE and the BS may be referred to as a UE-to-network relay. Although a single relay node is depicted between the UE 201A and the BS 202 in FIG. 2, it should be understood by one skilled in the art that any number of relay nodes may be included.

[0056] FIG. 3 illustrates a schematic diagram of a wireless communication system 300 in accordance with some embodiments of the present application.

[0057] As shown in FIG. 3, the wireless communication system 300 may include a number of UEs (e.g., UE 301A, UE 301B, and UE 301C). The wireless communication system 300 may also include a number of base stations (not shown in FIG. 3). Each of the UEs 301A, UE 301B, and UE 301C may be within the coverage of an NG-RAN or outside the coverage of an NG-RAN. Although a particular number of UEs are depicted in FIG. 3, it is contemplated that any number of UEs may be included in the wireless communication system 300.

[0058] The wireless communication system 300 may support sidelink communication. For example, UE 301B may be in sidelink communication with UE 301A and UE 301C, respectively. UE 301A and UE 301C may not be able to communicate with each other by direct sidelink communication due to the relatively large distance between them. However, UE 301A and UE 301C may establish a connection via UE 301B. In the context of this application, a UE (e.g., UE 301B) acting as a relay between two or more UEs may be referred to as a UE-to-UE relay. Although FIG. 3 depicts a UE-to-UE relay for unicast transmissions, it is contemplated that the UE may perform groupcast and broadcast transmissions via the UE-to-UE relay. It should be understood by one skilled in the art that although FIG. 3 depicts a single relay node between UE 301A and UE 301C, any number of relay nodes may be included.

[0059] Before performing sidelink communication between two or more UEs to UE, a UE discovery procedure may be performed to discover neighboring UEs. According to some embodiments of the present application, a proximity based service (ProSe) direct discovery procedure may be used for a UE to discover or be discovered by other UEs in its vicinity on a PC5 interface. For example, a UE may use the ProSe direct discovery procedure to discover other UEs having applications and / or groups of interest. The ProSe direct discovery procedure may be a common direct discovery procedure for discovering ProSe-enabled UEs, ProSe UE-to-network relays, and ProSe UE-to-UE relays.

[0060] 4 illustrates an exemplary example of a ProSe direct discovery procedure of Model A according to some embodiments of the present application. According to some embodiments of the present application, Model A may refer to a relay UE (e.g., UE-to-network 201B shown in FIG. 2 or UE-to-UE relay 301B shown in FIG. 3) broadcasting a discovery message to one or more other UEs.

[0061] Referring to FIG. 4, in step 1, relay UE 401 may broadcast a discovery message to one or more other UEs (e.g., UEs 402, 403, 404, and 405 in FIG. 4). The discovery message broadcast by the relay UE may be referred to as an announcement message. The announcement message may include information related to relaying. For example, the announcement message may include the identity (ID) of the relay UE. In another example, the announcement message may include at least one of the following information: service information and application information that are enabled or authorized to be relayed by the relay UE, group information for which the relay UE can provide relay services, slicing information (e.g., allowed network slice selection assistance information (NSSAI)) that the relay UE is enabled or authorized to be relayed, and information of the home public land mobile network (HPLMN) or visited public land mobile network (VPLMN) of the relay UE. In yet another example, the announcement message may include any other information that the relay UE intends to be broadcast.

[0062] 5 illustrates an exemplary example of a ProSe direct discovery procedure of model B according to some embodiments of the present application. According to some embodiments of the present application, model B may refer to a UE (e.g., UE 201A shown in FIG. 2, or UE 301A or 301C shown in FIG. 3) broadcasting a discovery message to one or more relay UEs. To distinguish a UE that broadcasts a discovery message in model B from a relay UE, a UE that broadcasts a discovery message in model B may be referred to as a remote UE.

[0063] Referring to FIG. 5, in step 1, a remote UE 501 may broadcast a discovery message to one or more relay UEs (e.g., relay UEs 502, 503, 504, 505 in FIG. 5). The discovery message broadcast by the remote UE may be referred to as a request message. The request message may be used to request information related to relaying. The request message may include information related to the remote UE. For example, the request message may include an ID of the remote UE. In another example, the request message may include at least one of the following information: service information and application information requested to be relayed, group information of the remote UE, slicing information of the remote UE (e.g., an allowed NSSAI), and HPLMN or VPLMN information of the remote UE. In yet another example, the announcement message may include any other information that the remote UE intends to be broadcast.

[0064] After receiving the request message, each relay UE may determine whether it can provide a relay connection to the remote UE based on the request message. For example, the relay UE may determine whether it can provide a service indicated in the request message. If the relay UE can provide a relay connection related to the information included in the request message, the relay UE may send a discovery response message to the remote UE. The discovery response message may include information related to relaying, for example, a relay ID and / or service information may be provided by the relay UE. Referring to FIG. 5, the relay UEs 502 and 503 may provide a relay connection related to the information included in the request message, and in step 2, the relay UEs 502 and 503 may send discovery response messages to the remote UE 501, respectively.

[0065] Therefore, the above discovery procedures in Model A and Model B involve sending a discovery message. However, how to send the discovery message (e.g., protocol stack and radio bearer for sending the discovery message) is not designed in the existing technology.

[0066] Moreover, for geocast services, some downlink traffic may only target UEs in a certain area or a certain zone or a certain range. To expand coverage or overcome poor connectivity, a network may deploy relay UEs to serve a certain area. That is, for some services (e.g., geocast services), ranging information and / or location information may be exchanged between relay UEs and remote UEs to realize ranging-based services. Therefore, how ranging-based information should be transmitted during discovery procedures also needed to be designed.

[0067] In addition, ranging-based (i.e., distance and / or direction-based) applications are applications that utilize the distance and direction between two UEs (not between a UE and a BS). For example, image sharing may be an example of a ranging-based application. That is, how to discover neighboring UEs to perform ranging-based applications also needed to be designed.

[0068] In view of the above, the embodiments of the present application aim to provide a solution for UE discovery, respectively for UE discovery in sidelink. Therefore, the embodiments of the present application can at least solve the above three technical problems. Further details about the embodiments of the present application are provided below in combination with the accompanying drawings.

[0069] According to some embodiments of the present application, the above-mentioned discovery messages may be transmitted UE-to-UE via the PC5-S protocol stack shown in FIG.

[0070] Referring to FIG. 6, FIG. 6 illustrates an exemplary PC5-S protocol stack according to some embodiments of the present application. The PC5-S protocol stack may be used to transmit control plane signaling over a PC5 interface. Referring to FIG. 6, a PC5-S protocol stack between two UEs (e.g., UE A and UE B) may include a PC5-S layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, a medium access control (MAC) layer, and a physical (PHY) layer. Each of these layers may have functions defined in a 3GPP standard document. At least one of the PDCP layer, the RLC layer, the MAC layer, and the PHY layer may be referred to as an access stratum (AS) layer.

[0071] Figure 7 is a flow diagram illustrating a method for UE discovery according to some embodiments of the present application. In the method of Figure 7, a discovery message may be transmitted via the PC5-S protocol stack shown in Figure 6. Although the method is illustrated at a system level by a transmitting UE and a receiving UE, those skilled in the art may understand that the method implemented in the transmitting UE and the method implemented in the receiving UE may be separately implemented and incorporated by other devices having similar functions.

[0072] 7, in step 701, a layer higher than the PC5-S layer (e.g., an application layer or a V2X layer) of a transmitting UE may generate a discovery message for UE discovery. UE discovery may refer to the transmitting UE discovering other UEs and / or the transmitting UE being discovered by other UEs.

[0073] In an embodiment of the present application, the transmitting UE may be a relay UE (e.g., the UE-to-network relay 201B shown in FIG. 2 or the UE-to-UE relay 301B shown in FIG. 3). In this embodiment, the discovery message may be an announcement message. The discovery message may include discovery information. The discovery information may include information related to relaying. For example, the discovery information may include an ID of the relay UE. In another example, the discovery information may include at least one of the following information: service information and application information that are enabled or authorized to be relayed by the relay UE, group information for which the relay UE can provide relay service, slicing information for which the relay UE is enabled or authorized to be relayed, and HPLMN or VPLMN information of the relay UE.

[0074] In another embodiment of the present application, the transmitting UE may be a remote UE (e.g., UE 201A shown in FIG. 2, or UE 301A or 301C shown in FIG. 3). In this embodiment, the discovery message may be a solicitation message. The solicitation message may be used to request information related to relaying. The solicitation message may include discovery information. The discovery information may include information related to the remote UE. For example, the discovery information may include an ID of the remote UE. In another example, the discovery information may include at least one of the following information: service information and application information requested to be relayed, group information of the remote UE, slicing information of the remote UE (e.g., allowed NSSAI), and HPLMN or VPLMN information of the remote UE.

[0075] After generating the discovery message, in step 702, the upper layers of the transmitting UE may deliver the discovery message to the PC5-S layer of the transmitting UE.

[0076] In some embodiments of the present application, when delivering a message to the PC5-S layer, the upper layer may send an indicator to the PC5-S layer to indicate whether the message delivered to the PC5-S layer is a discovery message, so that the PC5-S layer may treat the discovery message differently from other PC5-S messages.

[0077] In some embodiments of the present application, the upper layer of the transmitting UE may indicate to the AS layer of the transmitting UE whether the transmission is for a PC5-S signaling message or for V2X service data. In some other embodiments, the upper layer of the transmitting UE may send an indicator to the AS layer of the transmitting UE to indicate whether the PC5-S message includes discovery information, so that the AS layer may treat the PC5-S message including discovery information differently from other PC5-S messages. For example, for a PC5-S message including a discovery message, the PC5-S layer may deliver the PC5-S message to a logical channel and signaling radio bearer (SRB) associated with the discovery message.

[0078] After receiving the discovery message, in step 703, the PC5-S layer of the transmitting UE may generate a PC5-S message. The PC5-S message may be a new message different from an existing PC5-S message, for example, a direct discovery request message, or may be an existing PC5-S message, for example, a direct communication request message. The PC5-S message may include discovery information of the discovery message. In an embodiment of the present application, the PC5-S layer may parse the discovery message, obtain all discovery information of the message, and include all discovery information in the data portion of the PC5-S message. In another embodiment of the present application, the PC5-S layer may not parse the discovery message, and include the entire discovery message in the container of the PC5-S message. In yet another embodiment of the present application, the PC5-S message including discovery information does not include other information not related to the discovery of the UE. Other information not related to the discovery of the UE may refer to information included in the data portion, and not to information included in the header portion.

[0079] In some embodiments of the present application, the transmitting UE may be a relay UE (e.g., UE-to-network 201B shown in FIG. 2 or UE-to-UE relay 301B shown in FIG. 3). In these embodiments, the discovery information may include an indicator to indicate the type of relay. In an embodiment of the present application, the type of relay may be one of a UE-to-network relay and a UE-to-UE relay. In another embodiment of the present application, the type of relay may be one of a Layer 2 (L2) relay or a Layer 3 (L3) relay.

[0080] For example, FIG. 8 illustrates an example Layer 2 (L2) UE-to-UE relaying protocol stack in accordance with some embodiments of the present application.

[0081] The embodiment of Figure 8 illustrates protocol stacks on each side of UE1 (e.g., UE 301A shown in Figure 3), relay UE (e.g., relay UE 301B shown in Figure 3), and UE2 (e.g., UE 301C shown in Figure 3). Each of UE1 and UE2 is connected to the relay UE via a PC-5 interface, sometimes referred to as a PC5 interface.

[0082] An adaptation layer is supported on another PC5 link (i.e., PC5 link between relay UE and destination UE) for Layer 2 (i.e., L2) UE-to-UE relay. For L2 UE-to-UE relay, the adaptation layer is placed above the RLC sublayer for both control plane (CP) and user plane (UP) on said another PC5 link. Sidelink service data adaptation protocol (SDAP), sidelink PDCP, and RRC are terminated at the two remote UE-to-UE, while RLC, MAC, and PHY are terminated in each PC5 link.

[0083] In particular, as shown in Figure 8, the UE1 side includes the protocol layers of PHY, MAC, RLC, adaptation layer, PDCP, and SDAP; the relay UE side includes the protocol layers of PHY, MAC, RLC, and adaptation layer; and the UE2 side includes the protocol layers of PHY, MAC, RLC, adaptation layer, PDCP, and SDAP.

[0084] With respect to the Layer 3 (i.e., L3) UE-to-UE relay protocol stack, the relay UE has a complete protocol stack. That is, the user plane (UP) protocol stack of the L3 relay UE includes PHY, MAC, RLC, PDCP, and SDAP layers. The control plane (CP) protocol stack of the L3 relay UE includes PHY, MAC, RLC, PDCP, and RRC layers.

[0085] With respect to the Layer 3 (i.e., L3) UE-to-UE relay protocol stack, the relay UE has a complete protocol stack. That is, the user plane (UP) protocol stack of the L3 relay UE includes PHY, MAC, RLC, PDCP, and SDAP layers. The control plane (CP) protocol stack of the L3 relay UE includes PHY, MAC, RLC, PDCP, and RRC layers.

[0086] Thereafter, in step 704, the transmitting UE may broadcast a PC5-S message via the SRB.

[0087] For each unicast PC5-RRC connection, one sidelink (SL) SRB (i.e., SL-SRB0 as specified in the 3GPP® standard documents) may be used to transmit PC5-S messages before PC5-S security is established. One sidelink SRB (i.e., SL-SRB1 as specified in the 3GPP® standard documents) may be used to transmit PC5-S messages for establishing PC5-S security. After PC5-S security is established, one sidelink SRB (i.e., SL-SRB2 as specified in the 3GPP® standard documents) that is protected may be used to transmit PC5-S messages. One sidelink SRB (i.e., SL-SRB3 as specified in the 3GPP® standard documents) may be used to transmit PC5-RRC signaling, which is protected and transmitted only after PC5-S security is established.

[0088] In an embodiment of the present application, the SRB for transmitting the PC5-S message including discovery information may be an SRB specific to transmitting discovery information, e.g., SL-SRB4, which is different from SL-SRB0, SL-SRB1, SL-SRB2, and SL-SRB3. The configuration of the SRB for discovery messages (e.g., SL-SRB4) should be a default configuration or be determined by specifications. For example, SL-SRB4 may be defined in a 3GPP standard document and reserved for carrying the PC5-S message including discovery information. In some embodiments, the SRB for transmitting the PC5-S message including discovery information is established before PC5-S security is established.

[0089] The advantage of using a special SRB to send the PC5-S message containing discovery information is that UEs that are not interested in relaying will not receive this special SRB. If this PC5-S message containing the discovery message is allowed to be sent in SL-SRB0, all UEs will receive the discovery message. Some UEs will have to discard the discovery message if they are not interested in it.

[0090] In another embodiment of the present application, the SRB for transmitting PC5-S messages containing discovery information is an SRB for transmitting relay-related PC5-S messages only, i.e., all relay-related PC5-S messages may be transmitted via this SRB.

[0091] As a result, in step 705, the receiving UE (e.g., AS layer) may receive a PC5-S message including discovery information of the discovery message via the SRB. After receiving the PC5-S message, in step 706, the receiving UE (e.g., AS layer) may deliver the PC5-S message to the PC5-S layer of the receiving UE. The PC5-S layer of the receiving UE may perform the inverse operation of the PC5-S layer of the transmitting UE to generate the discovery message. Then, in step 707, the PC5-S layer of the receiving UE may deliver the discovery message to the upper layers (e.g., application layer and V2X layer) of the receiving UE.

[0092] If the transmitting UE is a relay UE (e.g., UE-to-network relay 201B shown in FIG. 2 or UE-to-UE relay 301B shown in FIG. 3), the receiving UE may be a remote UE (e.g., UE 201A shown in FIG. 2 or UE 301A or 301C shown in FIG. 3). In this embodiment, the discovery message may be an announcement message. After receiving the announcement message, the remote UE may determine whether to access the relay UE based on the information included in the announcement message.

[0093] When the transmitting UE is a remote UE (e.g., UE 201A shown in FIG. 2, or UE 301A or 301C shown in FIG. 3), the receiving UE may be a relay UE (e.g., UE-to-network relay 201B shown in FIG. 2, or UE-to-UE relay 301B shown in FIG. 3). In this embodiment, the discovery message may be a solicitation message. After receiving the announcement message, the relay UE may determine whether it can provide a relay connection indicated in the solicitation message. If the relay UE can provide a relay connection related to the information included in the solicitation message, the relay UE may send a discovery response message to the remote UE. Since the solicitation message is broadcast to at least one relay UE, all relay UEs that can provide a relay connection related to the information included in the solicitation message may send a discovery response message to the remote UE, and the remote UE may receive at least one discovery response message from at least one relay UE.

[0094] In some cases, some downlink traffic may only target UEs in a particular area or zone or range. In these cases, ranging and / or location information may be exchanged between relay and remote UEs to provide geocast services.

[0095] According to some embodiments of the present application, the transmitting UE may be a relay UE (e.g., UE-to-network relay 201B shown in FIG. 2 or UE-to-UE relay 301B shown in FIG. 3), and the receiving UE may be a remote UE (e.g., UE 201A shown in FIG. 2 or UE 301A or 301C shown in FIG. 3).

[0096] In an embodiment of the present application, the relay UE may receive ranging information and service information of at least one service from the BS. In some cases, in addition to the above information, the relay UE may also receive a mapping relationship between the ranging information and each of the at least one service. The BS may transmit the above information by dedicated RRC signaling or by system information block (SIB) signaling.

[0097] The ranging information may refer to a geographical range (e.g., 200 meters) within which the relay UE can provide service. The service information of the at least one service may include a service ID of each of the at least one service that the relay UE can provide. The mapping relationship may indicate which ranging information is related to which type of service.

[0098] After receiving the above information from the BS, the relay UE may include the ranging information, the location information of the relay UE, the service information of the at least one service, and the mapping relationship (in some cases) in discovery information of a discovery message (i.e., an announcement message), and send a PC5-S message including the discovery information. The location information of the relay UE may include at least one of a zone ID or area ID of the relay UE, Global Positioning System (GPS) information of the relay UE, and any other information related to the geographic location of the relay UE.

[0099] For example, the UE may determine the identity of the zone in which it is located (ie, the zone ID) using the following equations (1)-(3): x1 = FLOOR(x / L) Mod Nx (1) y1 = FLOOR(y / W) Mod Ny (2) Zone_id = y1*Nx + x1(3)

[0100] The parameters in the formula are defined as follows: L is the value of zoneLength included in zoneConfig in SystemInformationBlockType21 or SystemInformationBlockType26 specified in the 3GPP (registered trademark) standard document or in SL-V2X-Preconfiguration. ·W is the value of zoneWidth included in zoneConfig in SystemInformationBlockType21 or SystemInformationBlockType26 specified in the 3GPP (registered trademark) standard document or in SL-V2X-Preconfiguration. Nx is the value of zoneIdLongiMod included in zoneConfig in SystemInformationBlockType21 or SystemInformationBlockType26 specified in the 3GPP (registered trademark) standard document or in SL-V2X-Preconfiguration. Ny is the value of zoneIdLatiMod included in zoneConfig in SystemInformationBlockType21 or SystemInformationBlockType26 or SL-V2X-Preconfiguration defined in the 3GPP (registered trademark) standard document. · x is the geodesic distance in longitude between the UE's current position and the geographic coordinate (0, 0) according to the WGS84 model

[80] , expressed in meters. · y is the geodetic distance in latitude between the UE's current location and the geographic coordinate (0, 0) according to the WGS84 model

[80] , expressed in meters. For example, the information element "zoneConfig" may be as follows, as specified in the 3GPP standard document: SL-ZoneConfig-r14 ::= SEQUENCE { zoneLength-r14 ENUMERATED { m5, m10, m20, m50, m100, m200, m500, spare1}, zoneWidth-r14 ENUMERATED { m5, m10, m20, m50, m100, m200, m500, spare1}, zoneIdLongiMod-r14 INTEGER (1..4), zoneIdLatiMod-r14 INTEGER (1..4) }

[0101] In other words, the relay UE may send ranging information, location information, service information of at least one service, and a mapping relationship (in some cases) in the discovery information of the discovery message. Thus, the discovery information included in the PC5-S message sent in step 704 may include at least one of ranging information, location information, service information of at least one service, and a mapping relationship (in some cases).

[0102] As a result, in step 705, the remote UE may receive the ranging information, the location information of the relay UE, the service information of the at least one service, and the mapping relationship (in some cases) between the ranging information and each of the at least one service included in the discovery information of the PC5-S message, and the remote UE may determine whether to select a relay UE and / or access a BS based on its location, the interesting service of the remote UE, and the discovery information. For example, the remote UE may calculate the distance between the remote UE and the relay UE, and if the remote UE is not located within the ranging information indicated in the discovery information, the remote UE may not select a relay UE. In another example, if the remote UE is located within the ranging information indicated in the discovery information and the relay UE just provides the interesting service of the remote UE, the remote UE may select a relay UE and / or access a BS.

[0103] In another embodiment of the present application, the relay UE may receive ranging information and service information of at least one service from the BS. In some cases, in addition to the above information, the relay UE may also receive a mapping relationship between the ranging information and each of the at least one service. The BS may transmit the above information by dedicated RRC signaling or by system information block (SIB) signaling.

[0104] The ranging information may refer to a geographical range (e.g., 200 meters) within which the relay UE can provide service. The service information of the at least one service may include a service ID of each of the at least one service that the relay UE can provide. The mapping relationship may indicate which ranging information is related to which type of service.

[0105] After receiving the above information from the BS, the relay UE may include the location information of the other UE (e.g., a remote UE), the service information of the at least one service, and the mapping relationship (in some cases) in the discovery information of a discovery message (i.e., an announcement message), and send a PC5-S message including the discovery information. The location information of the other UE may include at least one of a zone ID or area ID of the other UE, Global Positioning System (GPS) information of the other UE, and any other information related to the geographic location of the other UE.

[0106] The location information of another UE may be determined based on the location information and ranging information of the relay UE. For example, the relay UE may determine its own location information (e.g., a zone ID) based on Equations (1)-(3), and then determine the location information of another UE based on the ranging information and the location information of the relay UE.

[0107] In other words, the relay UE may send the location information of another UE, the service information of at least one service, and the mapping relationship (in some cases) in the discovery information of the discovery message. Thus, the discovery information included in the PC5-S message sent in step 704 may include the location information of another UE, the service information of at least one service, and the mapping relationship (in some cases) in the discovery information of the discovery message.

[0108] As a result, in step 705, the remote UE may receive the location information of another UE, the service information of the at least one service, and a mapping relationship (in some cases) between the ranging information and each of the at least one service included in the discovery information of the PC5-S message, and the remote UE may determine whether its location satisfies the location information included in the discovery information. The location information of the remote UE may include at least one of a zone ID or area ID of the remote UE, Global Positioning System (GPS) information of the remote UE, and any other information related to the geographic location of the remote UE.

[0109] If the location information of the remote UE satisfies the location information included in the discovery information and the relay UE just provides the interesting service of the remote UE, the remote UE may send a discovery response message to the relay UE. For example, the discovery information may include a zone ID numbered as "7", and after receiving the discovery information, the remote UE may determine its own location information (e.g., zone ID) based on equations (1) to (3), and if the location information of the remote UE is "7" and the relay UE just provides the interesting service of the remote UE, the remote UE may send a discovery response message.

[0110] According to some embodiments, the transmitting UE may be a remote UE (e.g., UE 201A shown in FIG. 2, or UE 301A or 301C shown in FIG. 3), and the receiving UE is a relay UE (e.g., UE-to-network relay 201B shown in FIG. 2, or UE-to-UE relay 301B shown in FIG. 3).

[0111] In these embodiments, the remote UE may send a discovery message (e.g., a solicitation message) to the relay UE that includes location information of the remote UE. The location information of the remote UE may include at least one of a zone ID or area ID of the remote UE, global positioning system (GPS) information of the remote UE, and any other information related to the geographic location of the remote UE.

[0112] Thus, the discovery information included in the PC5-S message sent in step 704 may include location information of the remote UE.

[0113] As a result, in step 705, the relay UE may receive the location information of the remote UE included in the discovery information of the PC5-S message.

[0114] In an embodiment of the present application, the relay UE may determine whether to allow the remote UE to access based on a configuration from the BS. For example, the configuration from the BS may include at least one of ranging information of the relay UE, service information of at least one service that may be provided by the relay UE, and a mapping relationship between the ranging information and each of the at least one service. In some examples, the relay UE may calculate a distance between the UE and the relay UE, and if the remote UE is not located within the range of the relay UE, the relay UE may determine not to allow the remote UE to access. In some other examples, if the remote UE is located within the range of the relay UE and the relay UE can provide an interesting service for the remote UE, the relay UE may allow the remote UE to access. Then, the relay UE may send a discovery response message to the remote UE.

[0115] In another example of the present application, after receiving the location information of the remote UE in the discovery information, the relay UE may send the discovery information including the location information to the BS, so that the BS may determine whether to allow the remote UE to establish a connection with the remote UE through the relay UE.

[0116] In some cases, ranging-based (i.e., distance and / or direction-based) applications may be used for two UEs to UEs. The two UEs may be any kind of UEs. In the embodiment of the present application, both of the two UEs may not be relay UEs. In the embodiment of the present application, one of the two UEs may be a relay UE (e.g., UE to network relay or UE to UE relay), and the other UE may not be a relay UE. For example, the two UEs may be UE 101A and UE 101B, UE 101B and UE 101C, or UE 101A and UE 101C shown in FIG. 1, or UE 201A and UE 201B shown in FIG. 2, or UE 301A and UE 301B, or UE 301B and UE 301C shown in FIG. 3.

[0117] Taking FIG. 1 as an example, assume that UE 101A is seeking neighboring UEs for data transmission from one or more neighboring UEs (eg, UE 101B and UE 101C).

[0118] In the example of the present application, each of one or more neighboring UEs of UE 101A may transmit a discovery message to UE 101A. The discovery information included in the discovery message may include ranging information, neighboring UE location information, and neighboring UE direction information. The neighboring UE location information may include at least one of the neighboring UE's zone ID or area ID, the neighboring UE's GPS information, and any other information related to the neighboring UE's geographic location.

[0119] An upper layer (e.g., application layer) of UE 101A may indicate to AS layer of UE 101A to receive discovery messages. UE 101A may then receive one or more discovery messages from one or more neighboring UEs. For example, UE 101A may receive discovery messages from UE 101B and UE 101C, respectively. UE 101A may then select a UE based on the one or more discovery messages. For example, UE 101A may calculate a distance between UE 101A and each neighboring UE to determine whether UE 101A is within range of the neighboring UE (in other words, the neighboring UE is within range of UE 101A). UE 101A may also determine whether the direction of UE 101A is the same as each neighboring UE. For all neighboring UEs that are within range of UE 101A and have the same direction information as UE 101A, UE 101A may select the closest UE from these UEs and send the data transmission to the closest UE. For example, assuming UE 101B and UE 101C are within range and have the same direction as UE 101A, and UE 101B is closest to UE 101A, UE 101A may select UE 101B and send the data transmission to UE 101B. As a result, UE 101B may receive the data transmission from UE 101A.

[0120] In another example of the present application, the higher layer (e.g., application layer) of UE 101A may indicate to the AS layer of UE 101A to send a discovery message to one or more neighboring UEs (e.g., UE 101B and UE 101C). UE 101A may then send the discovery message to the one or more neighboring UEs. The discovery information included in the discovery message may include ranging information, location information, and direction information of UE 101A. The location information of UE 101A may include at least one of a zone ID or area ID of the neighboring UE, GPS information of the neighboring UE, and any other information related to the geographical location of the neighboring UE.

[0121] After receiving the discovery message, each of the one or more neighboring UEs may determine whether to respond to the discovery message based on the ranging information, location information, and direction information of UE 101A. For example, each neighboring UE may calculate the distance between the neighboring UE and UE 101A. If the neighboring UE is located within the range indicated by the ranging information of UE 101A and in the same direction as UE 101A, the neighboring UE may transmit a discovery response message to UE 101A. In an embodiment of the present application, the discovery response message may include the location information of the neighboring UE.

[0122] As a result, the UE 101A may receive at least one response message from at least one neighboring UE, and each of the at least one discovery response message may include location information of the corresponding neighboring UE. The location information of the neighboring UE may include at least one of a zone ID or area ID of the neighboring UE, GPS information of the neighboring UE, and any other information related to the geographical location of the neighboring UE. Then, the UE 101A may select the nearest neighboring UE for data transmission.

[0123] Ranging-based applications may be beneficial in some cases. For example, a user may want to share a photo with one of the other users when gathering with them. The ranging function in the user's UE automatically calculates the distance and direction of all UEs around the UE based on the discovery message and / or discovery response message, and knows which UE the UE is pointing to and which UE is the closest UE in that direction. Then, the UE automatically tells the user whether to select that UE for transmitting an image based on the ranging result. Then, data transmission starts using a communication technology, for example, 5G technology or Wi-Fi technology.

[0124] In the above embodiment of Figure 7, the discovery message may be transmitted over the PC5-S protocol stack shown in Figure 6. However, according to some other embodiments of the present application, the discovery message may be transmitted over the discovery protocol stack shown in Figure 9.

[0125] Referring to Figure 9, Figure 9 shows an example discovery protocol stack according to some embodiments of the present application. The difference between Figure 6 and Figure 9 is that the PC5-S layer in Figure 6 is replaced by a discovery layer in Figure 9. The discovery layer may be a layer specific to sending discovery messages. The meanings of the other layers are the same as those in Figure 6.

[0126] When using a discovery protocol stack to transmit a discovery message, the procedure may be as follows: a layer higher than the discovery layer of the transmitting UE (e.g., an application layer or a V2X layer) may generate a discovery message for UE discovery and deliver the discovery message to the discovery layer. UE discovery may refer to the transmitting UE discovering other UEs and / or the transmitting UE being discovered by other UEs.

[0127] Similarly, the discovery message may be an announcement message sent by a relay UE or a solicitation message sent by a remote UE. After receiving the discovery message, the discovery layer may generate a message including the discovery information of the discovery message. In an embodiment of the present application, the discovery layer may parse the discovery message, obtain all the discovery information of the discovery message, and include all the discovery information in the data portion of the message. In another embodiment of the present application, the discovery layer may not parse the discovery message, and include the entire discovery message in the container of the message. The information included in the discovery information may be the same as the information in the embodiment of FIG. 7.

[0128] The discovery layer may then deliver a message to the PDCP layer. The message containing the discovery information may be mapped to a sidelink control channel (SCCH). In an embodiment of the present application, the message generated by the discovery layer may be transmitted over an SRB as defined in the embodiment of FIG.

[0129] 10 shows a simplified block diagram of an apparatus for UE discovery according to some embodiments of the present application. The apparatus 1000 may be a UE, for example, UE 101A, UE 101B, or UE 101C shown in FIG. 1, UE 201A or UE 201B shown in FIG. 2, or UE 301A, UE 301B, or UE 301C shown in FIG. 3.

[0130] Referring to FIG. 10, the apparatus 1000 may include at least one non-transitory computer-readable medium 1002, at least one receiving circuit 1004, at least one transmitting circuit 1006, and at least one processor 1008. In some embodiments of the present application, the at least one receiving circuit 1004 and the at least one transmitting circuit 1006 may be integrated into at least one transceiver. The at least one non-transitory computer-readable medium 1002 may store computer-executable instructions. The at least one processor 1008 may be coupled to the at least one non-transitory computer-readable medium 1002, the at least one receiving circuit 1004, and the at least one transmitting circuit 1006. The computer-executable instructions may be programmed to perform a method by the at least one receiving circuit 1004, the at least one transmitting circuit 1006, and the at least one processor 1008. The method may be a method according to an embodiment of the present application, for example, the method shown in FIG. 7.

[0131] The method according to the embodiment of the present application can also be implemented on a programmed processor. However, the controller, flow charts, and modules may be implemented in hardware electronic or logic circuits such as general-purpose or special-purpose computers, programmed microprocessors or microcontrollers and peripheral integrated circuit elements, integrated circuits, discrete element circuits, programmable logic devices, and the like. In general, any device on which a finite state machine capable of implementing the flow charts shown in the figures exists may be used to implement the functions of the processor of the present application. For example, the embodiment of the present application provides an apparatus for UE discovery, including a processor and a memory. Computer programmable instructions for implementing the method for UE discovery are stored in the memory, and the processor is configured to execute the computer programmable instructions for implementing the method for UE discovery. The method may be the method described above or other methods according to the embodiment of the present application.

[0132] An alternative embodiment preferably implements the method according to the embodiment of the present application on a non-transitory computer-readable storage medium storing computer programmable instructions. The instructions are preferably executed by a computer executable component preferably integrated with the network security system. The non-transitory computer-readable storage medium may be contained in any suitable computer readable medium, such as a RAM, a ROM, a flash memory, an EEPROM, an optical storage device (CD or DVD), a hard drive, a floppy drive, or any suitable device. The computer executable component is preferably a processor, but the instructions may alternatively or additionally be executed by any suitable dedicated hardware device. For example, an embodiment of the present application provides a non-transitory computer-readable storage medium having stored thereon computer programmable instructions. The computer programmable instructions are configured to implement the method for UE discovery described above, or other methods according to the embodiment of the present application.

[0133] Although the present application has been described with its specific embodiments, it is apparent that many alternatives, modifications, and variations will be apparent to those skilled in the art. For example, various components of the embodiments may be interchanged, added, or substituted in other embodiments. Also, not all elements of each figure are necessary for the operation of the disclosed embodiments. For example, a person skilled in the art of the disclosed embodiments is enabled to make and use the teachings of the present application by simply adopting the elements of the independent claims. Thus, the embodiments of the present application described herein are intended to be illustrative and not limiting. Various changes may be made without departing from the spirit and scope of the present application. [Explanation of symbols]

[0134] 100 Wireless communication system 101A UE 101B UE 101C UE 102 BS 103 BS 200 Wireless Communication System 201A UE 201B UE 202 B.S. 300 Wireless Communication System 301A UE 301B UE 301C UE 401 Relay UE 402UE 403UE 404UE 405 UE 501 Remote UE 502 Relay UE 503 Relay UE 504 Relay UE 505 Relay UE 1000 devices 1002 Non-transitory computer readable medium 1004 Receiver circuit 1006 Transmitting circuit 1008 Processor

Claims

1. generating a discovery message for user equipment (UE) discovery; delivering the discovery message to a PC5 signaling (PC5-S) layer of a first UE; generating a PC5-S message, the PC5-S message including discovery information of the discovery message; broadcasting the PC5-S message including the discovery information via a signaling radio bearer (SRB); The method includes:

2. 2. The method of claim 1, further comprising the step of: in response to delivery of the discovery message to the PC5-S layer of the first UE, transmitting an indicator from an upper layer of the first UE to the PC5-S layer of the first UE to indicate whether the message delivered to the PC5-S layer is the discovery message.

3. 2. The method of claim 1, further comprising: transmitting an indicator from an upper layer of the first UE to an access stratum (AS) layer of the first UE to indicate whether the PC5-S message includes the discovery information.

4. The method of claim 1 , wherein the PC5-S message containing the discovery information does not contain other information unrelated to discovery of the UE.

5. The method of claim 1 , wherein the discovery information includes an indicator for indicating a type of repeater.

6. The method of claim 5, wherein the relay type is one of a UE-to-UE relay and a UE-to-network relay.

7. 6. The method of claim 5, wherein the type of repeater is one of a Layer 2 (L2) repeater and a Layer 3 (L3) repeater.

8. The method according to claim 1, wherein the SRB for transmitting the PC5-S message including the discovery information is an SRB only for transmitting PC5-S messages related to relaying.

9. receiving ranging information, service information of at least one service, and a mapping relationship between the ranging information and each of the at least one service from a base station (BS); sending the ranging information, the location information of the first UE, service information of at least one service, and the mapping relationship in the discovery information of the discovery message; The method of claim 1 further comprising:

10. receiving ranging information, service information of at least one service, and a mapping relationship between the ranging information and each of the at least one service from a base station (BS); sending location information of a second UE and service information of at least one service in the discovery information of the discovery message; The method of claim 1 further comprising:

11. The method of claim 10, further comprising: receiving a discovery response message from a third UE, wherein location information of the third UE fulfills the location information included in the discovery message.

12. sending ranging information, location information and direction information of the first UE in the discovery information of the discovery message; receiving a data transmission from the second UE in response to the first UE being a closest UE of the second UE; The method of claim 1 further comprising:

13. sending ranging information, location information and direction information of the first UE in the discovery information of the discovery message; receiving at least one discovery response message from at least one second UE, each of the at least one discovery response message including location information of the second UE; selecting a closest UE from the at least one second UE based on the at least one response message; The method of claim 1 further comprising:

14. 14. The method of any one of claims 9, 10, 12, and 13, wherein the location information includes at least one of a zone ID and Global Positioning System (GPS) information.

15. at least one non-transitory computer-readable medium having computer-executable instructions stored thereon; at least one receiving circuit; at least one transmit circuit; at least one processor coupled to the at least one non-transitory computer readable medium, the at least one receiving circuit, and the at least one transmitting circuit; Including, 15. An apparatus programmed with the computer executable instructions to implement the method of any one of claims 1 to 14 using the at least one receiving circuit, the at least one transmitting circuit, and the at least one processor.

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