Relay discovery method and terminal

Abstract

The present application relates to a relay discovery method and terminal. The relay discovery method includes a first terminal receiving a discovery message sent by a second terminal via an SL SRB; the first terminal parses the discovery message to determine whether to select the second terminal as its own relay terminal. In the relay discovery process, the discovery message is transmitted via a sidelink signaling radio bearer, and the discovery message may not be transmitted via a sidelink discovery channel, and there is no need to add a new transmission channel and physical channel, which can reduce system complexity.

Description

[0001] This application is a divisional application of the invention patent application with application number 202080099362.4, application date July 29, 2020, and invention name “Relay discovery method and terminal”. Technical Field

[0002] The present application relates to the field of communications, and more specifically, to a relay discovery method and a terminal. Background Art

[0003] A transmission channel called SL-DCH (Sidelink Discovery Channel) was introduced on the PC5 interface of LTE (Long Term Evolution) of 3GPP (3rd Generation Partnership Project). During the relay discovery process, the discovery request message and the discovery message will be mapped to the SL-DCH, and the SL-DCH will be sent through the PSDCH (Physical Sidelink Discovery Channel). In order to simplify the sending and receiving of discovery messages and discovery request messages, the LTE system introduces the above-mentioned new transmission channels and physical channels. However, the control plane and data plane protocols of the communication system need to introduce additional mechanisms for this purpose, thereby introducing unnecessary system complexity. Summary of the invention

[0004] The embodiments of the present application provide a relay discovery method and terminal, which do not require the addition of new transmission channels and physical channels and can reduce system complexity.

[0005] The present application provides a relay discovery method, including:

[0006] The first terminal receives a discovery message sent by the second terminal through a side link signaling radio bearer SL SRB;

[0007] The first terminal parses the discovery message to determine whether to select the second terminal as its relay terminal.

[0008] The present application provides a relay discovery method, including:

[0009] The second terminal sends a discovery message to the first terminal through a side link signaling radio bearer SL SRB, so that the first terminal parses the discovery message to determine whether to select the second terminal as its relay terminal.

[0010] An embodiment of the present application provides a first terminal, including:

[0011] A receiving unit, configured to receive a discovery message sent by the second terminal via a side link signaling radio bearer SL SRB;

[0012] The processing unit is used to parse the discovery message to determine whether to select the second terminal as its relay terminal.

[0013] An embodiment of the present application provides a second terminal, including:

[0014] The sending unit is used to send a discovery message to the first terminal through a side link signaling radio bearer SL SRB, so that the first terminal parses the discovery message to determine whether to select the second terminal as its relay terminal.

[0015] The embodiment of the present application provides a terminal device, including a processor and a memory. The memory is used to store a computer program, and the processor is used to call and run the computer program stored in the memory, so that the terminal device executes any one of the above-mentioned relay discovery methods.

[0016] An embodiment of the present application provides a chip for implementing the above-mentioned relay discovery method.

[0017] Specifically, the chip includes: a processor, which is used to call and run a computer program from a memory, so that a device equipped with the chip executes any one of the above-mentioned relay discovery methods.

[0018] An embodiment of the present application provides a computer-readable storage medium for storing a computer program. When the computer program is executed by a device, the device executes any one of the above-mentioned relay discovery methods.

[0019] An embodiment of the present application provides a computer program product, including computer program instructions, which enable a computer to execute any one of the above-mentioned relay discovery methods.

[0020] An embodiment of the present application provides a computer program, which, when executed on a computer, enables the computer to execute any one of the above-mentioned relay discovery methods.

[0021] In the embodiment of the present application, the discovery message is transmitted through the side link signaling wireless bearer during the relay discovery process, and the discovery message may not be transmitted through the side link discovery channel. There is no need to add new transmission channels and physical channels, which can reduce system complexity and reduce design and R&D costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of an application scenario according to an embodiment of the present application.

[0023] Figure 2 It is a schematic flowchart of a relay discovery method according to an embodiment of the present application.

[0024] Figure 3 It is a schematic flowchart of a relay discovery method according to another embodiment of the present application.

[0025] Figure 4 It is a schematic diagram of UE accessing the network through a relay.

[0026] Figure 5 is a schematic diagram of mode B of relay discovery.

[0027] Figure 6 is a schematic diagram of mode A of relay discovery.

[0028] Figure 7 It is a schematic diagram of the relay in the side-travel scenario.

[0029] Figure 8 It is a schematic block diagram of a first terminal according to an embodiment of the present application.

[0030] Fig. 9 is a schematic block diagram of a first terminal according to another embodiment of the present application.

[0031] Fig.10 is a schematic block diagram of a second terminal according to an embodiment of the present application.

[0032] Fig.11 is a schematic block diagram of a second terminal according to another embodiment of the present application.

[0033] Fig.12 It is a schematic block diagram of a communication device according to an embodiment of the present application.

[0034] Fig.13 is a schematic block diagram of a chip according to an embodiment of the present application.

[0035] Fig.14 It is a schematic block diagram of a communication system according to an embodiment of the present application. Specific embodiments

[0036] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0037] The technical solutions of the embodiments of the present application can be applied to various communication systems, such as: Global System of Mobile communication (GSM) system, Code Division Multiple Access (CDMA) system, Wideband Code Division Multiple Access (WCDMA) system, General Packet Radio Service (GPRS), Long Term Evolution (LTE) system, Advanced Long Term Evolution (LTE-A) system, New Radio (NR) system, NR system evolution system, LTE on unlicensed spectrum (LTE-U) system, NR on unlicensed spectrum (NR-U) system, Non-Terrestrial Networks (NTN) system, Universal Mobile Telecommunication System (UMTS), Wireless Local Area Networks (WLAN), Wireless Fidelity (Wireless Fidelity) system. Fidelity, WiFi), fifth-generation communication (5th-Generation, 5G) system or other communication systems, etc.

[0038] Generally speaking, traditional communication systems support a limited number of connections and are easy to implement. However, with the development of communication technology, mobile communication systems will not only support traditional communications, but will also support, for example, device to device (Device to Device, D2D) communication, machine to machine (Machine to Machine, M2M) communication, machine type communication (Machine Type Communication, MTC), vehicle to vehicle (V2V) communication, or vehicle to everything (V2X) communication, etc. The embodiments of the present application can also be applied to these communication systems.

[0039] Optionally, the communication system in the embodiment of the present application can be applied to a carrier aggregation (CA) scenario, a dual connectivity (DC) scenario, or a standalone (SA) networking scenario.

[0040] Optionally, the communication system in the embodiment of the present application can be applied to an unlicensed spectrum, wherein the unlicensed spectrum can also be considered as a shared spectrum; or, the communication system in the embodiment of the present application can also be applied to an authorized spectrum, wherein the authorized spectrum can also be considered as an unshared spectrum.

[0041] The embodiments of the present application describe various embodiments in conjunction with network devices and terminal devices, wherein the terminal device may also be referred to as user equipment (UE), access terminal, user unit, user station, mobile station, mobile station, remote station, remote terminal, mobile device, user terminal, terminal, wireless communication device, user agent or user device, etc.

[0042] The terminal device can be a station (STAION, ST) in a WLAN, a cellular phone, a cordless phone, a Session Initiation Protocol (SIP) phone, a Wireless Local Loop (WLL) station, a Personal Digital Assistant (PDA) device, a handheld device with wireless communication function, a computing device or other processing device connected to a wireless modem, a vehicle-mounted device, a wearable device, a terminal device in a next-generation communication system such as an NR network, or a terminal device in a future evolved Public Land Mobile Network (PLMN) network, etc.

[0043] In the embodiments of the present application, the terminal device can be deployed on land, including indoors or outdoors, handheld, wearable or vehicle-mounted; it can also be deployed on the water surface (such as ships, etc.); it can also be deployed in the air (for example, on airplanes, balloons and satellites, etc.).

[0044] In the embodiment of the present application, the terminal device can be a mobile phone, a tablet computer, a computer with wireless transceiver function, a virtual reality (VR) terminal device, an augmented reality (AR) terminal device, a wireless terminal device in industrial control, a wireless terminal device in self driving, a wireless terminal device in remote medical, a wireless terminal device in a smart grid, a wireless terminal device in transportation safety, a wireless terminal device in a smart city, or a wireless terminal device in a smart home, etc.

[0045] As an example but not limitation, in the embodiments of the present application, the terminal device may also be a wearable device. Wearable devices may also be referred to as wearable smart devices, which are a general term for wearable devices that are intelligently designed and developed using wearable technology for daily wear, such as glasses, gloves, watches, clothing, and shoes. A wearable device is a portable device that is worn directly on the body or integrated into the user's clothes or accessories. Wearable devices are not only hardware devices, but also powerful functions achieved through software support, data interaction, and cloud interaction. Broadly speaking, wearable smart devices include full-featured, large-sized, and fully or partially independent of smartphones, such as smart watches or smart glasses, as well as devices that only focus on a certain type of application function and need to be used in conjunction with other devices such as smartphones, such as various types of smart bracelets and smart jewelry for vital sign monitoring.

[0046] In an embodiment of the present application, the network device may be a device for communicating with a mobile device. The network device may be an access point (AP) in WLAN, a base station (Base Transceiver Station, BTS) in GSM or CDMA, a base station (NodeB, NB) in WCDMA, an evolved base station (EvolutionalNode B, eNB or eNodeB) in LTE, or a relay station or access point, or a vehicle-mounted device, a wearable device, and a network device (gNB) in an NR network, or a network device in a future evolved PLMN network, or a network device in an NTN network, etc.

[0047] As an example but not limitation, in an embodiment of the present application, the network device may have a mobile characteristic, for example, the network device may be a mobile device. Optionally, the network device may be a satellite or a balloon station. For example, the satellite may be a low earth orbit (LEO) satellite, a medium earth orbit (MEO) satellite, a geostationary earth orbit (GEO) satellite, a high elliptical orbit (HEO) satellite, etc. Optionally, the network device may also be a base station set up in a location such as land or water.

[0048] In an embodiment of the present application, the network device can provide services for a cell, and the terminal device communicates with the network device through the transmission resources used by the cell (for example, frequency domain resources, or spectrum resources). The cell can be a cell corresponding to the network device (for example, a base station), and the cell can belong to a macro base station or a base station corresponding to a small cell. The small cells here may include: metro cells, micro cells, pico cells, femto cells, etc. These small cells have the characteristics of small coverage and low transmission power, and are suitable for providing high-speed data transmission services.

[0049] Figure 1 A communication system 100 is exemplarily shown. The communication system includes a network device 110 and two terminal devices 120. Optionally, the communication system 100 may include multiple network devices 110, and each network device 110 may include other number of terminal devices 120 within its coverage area, which is not limited in the present embodiment.

[0050] Optionally, the communication system 100 may also include other network entities such as a mobility management entity (Mobility Management Entity, MME), an access and mobility management function (Access and Mobility Management Function, AMF), etc., which is not limited in the embodiments of the present application.

[0051] Among them, the network equipment may include access network equipment and core network equipment. That is, the wireless communication system also includes multiple core networks for communicating with the access network equipment. The access network equipment may be an evolutionary base station (evolutional node B, referred to as eNB or e-NodeB) macro base station, micro base station (also called "small base station"), micro-micro base station, access point (AP), transmission point (TP) or new generation base station (new generation Node B, gNodeB) in a long-term evolution (LTE) system, a next-generation (mobile communication system) (next radio, NR) system or an authorized auxiliary access long-term evolution (LAA-LTE) system.

[0052] It should be understood that the device with communication function in the network / system in the embodiment of the present application can be referred to as a communication device. Figure 1 Taking the communication system shown as an example, the communication equipment may include network equipment and terminal equipment with communication functions. The network equipment and terminal equipment may be specific equipment in the embodiments of the present application and will not be repeated here. The communication equipment may also include other equipment in the communication system, such as network controllers, mobile management entities and other network entities, which are not limited to the embodiments of the present application.

[0053] It should be understood that the terms "system" and "network" are often used interchangeably in this article. The term "and / or" in this article is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0054] It should be understood that the "indication" mentioned in the embodiments of the present application can be a direct indication, an indirect indication, or an indication of an association relationship. For example, A indicates B, which can mean that A directly indicates B, for example, B can be obtained through A; it can also mean that A indirectly indicates B, for example, A indicates C, and B can be obtained through C; it can also mean that there is an association relationship between A and B.

[0055] In the description of the embodiments of the present application, the term "corresponding" may indicate a direct or indirect correspondence between two items, or an association relationship between the two items, or a relationship between indication and being indicated, configuration and being configured, and the like.

[0056] To facilitate understanding of the technical solutions of the embodiments of the present application, the relevant technologies of the embodiments of the present application are described below. The following related technologies can be arbitrarily combined with the technical solutions of the embodiments of the present application as optional solutions, and they all belong to the protection scope of the embodiments of the present application.

[0057] Figure 2 is a schematic flow chart of a relay discovery method 200 according to an embodiment of the present application. The method may optionally be applied to Figure 1 The system shown in the figure is not limited thereto. The method includes at least part of the following contents.

[0058] S210. The first terminal receives a discovery message sent by the second terminal via a sidelink (Sidelink, SL, or sidelink) signaling radio bearer (Signaling Radio Bearer, SRB).

[0059] S220: The first terminal parses the discovery message to determine whether to select the second terminal as its relay terminal.

[0060] Exemplarily, in the relay discovery process, the first terminal can receive the discovery message of the second terminal through the SL SRB, and can reuse the existing transmission channels and physical channels of the sidelink communication. For example, PSSCH, PSCCH, etc. Therefore, in the relay discovery process, the sidelink discovery channel may not be used to transmit the discovery message, and there is no need to add new transmission channels and physical channels, which can reduce the complexity of the system.

[0061] Optionally, in the embodiment of the present application, the first terminal parses the discovery message to determine whether to select the second terminal as its relay terminal, including:

[0062] The first terminal parses the discovery message, determines that the second terminal can serve as a relay for the first terminal, and selects the second terminal as its own relay terminal when the measured wireless signal strength of the second terminal is higher than a first threshold.

[0063] Exemplarily, the discovery message sent by the second terminal may include information about various services supported by the second terminal. If the first terminal parses the discovery message and determines that the second terminal can serve as a relay for the first terminal (for example, it finds the service of interest in the discovery message), and the wireless signal strength of the second terminal obtained by parsing the discovery message is higher than a set first threshold, the second terminal can be selected as its relay terminal. The first threshold may be network-configured or pre-configured.

[0064] Optionally, in the embodiment of the present application, the first terminal receiving a discovery message sent by the second terminal through the sidelink signaling radio bearer further includes:

[0065] The first terminal receives a discovery announcement message periodically sent by the second terminal through the SL SRB.

[0066] Optionally, in an embodiment of the present application, the discovery announcement message includes at least a sending period.

[0067] Optionally, in the embodiment of the present application, the method further includes:

[0068] After acquiring the sending cycle, the first terminal periodically receives the discovery announcement message of the second terminal through the SL SRB based on the sending cycle.

[0069] Optionally, in an embodiment of the present application, the sending period is equal to the period of the wireless resources for sending the discovery announcement message.

[0070] Optionally, in an embodiment of the present application, the period of the wireless resource is a period of pre-configured wireless resources configured by the network, or a period of wireless resources obtained by the second terminal through automatic acquisition.

[0071] Optionally, in an embodiment of the present application, the method further includes: the first terminal sends a discovery request message via the SL SRB. Optionally, this step may be before S210. In this case, after the second terminal receives the discovery request message, it may return a discovery response message to the first terminal. S210 The first terminal receives a discovery message sent by the second terminal via the SL SRB, including: the first terminal receives a discovery response message sent by the second terminal via the SL SRB.

[0072] An exemplary method includes: the first terminal first sends a discovery request message to the second terminal through the SL SRB. After receiving the discovery request message, the second terminal sends a discovery message to the first terminal through the SL SRB. The first terminal selects a relay terminal based on the discovery message sent by the second terminal in response to the discovery request message.

[0073] An exemplary method includes that the second terminal periodically sends a discovery message to the first terminal via the SL SRB. This method does not need to trigger the sending of the second terminal discovery message by a received discovery request message. The first terminal selects a relay terminal based on the discovery message periodically sent by the second terminal.

[0074] Optionally, in the embodiment of the present application, the first terminal triggers sending a discovery request message or monitoring a discovery message, including at least one of the following situations:

[0075] The first terminal is out of the coverage of the network device and needs to be connected to the network device, and the second terminal is within the coverage of the network device.

[0076] The first terminal is within the coverage of the network device, but the measured reference signal receiving power (RSRP) of the wireless signal of the network device to which the first terminal is connected is less than a second threshold, and the second terminal is within the coverage of the network device.

[0077] The first terminal needs to be connected to a third terminal.

[0078] Exemplarily, in the scenario of uplink communication, whether to trigger sending a discovery request message or listening to a discovery message can be determined based on the positional relationship between the first terminal and the network device, signal strength, etc. Assume that the first terminal is outside the coverage of the network device, and the second terminal is within the coverage of the network device. The second terminal can maintain a good communication connection with the network device, and the first terminal can trigger sending a discovery request message or listening to a discovery message to determine whether the second terminal can be used as a relay terminal to communicate with the network device.

[0079] For example, terminal A1 is in the coverage of cell C1, and terminal A2 is in the coverage of cell C2. Terminal A1 can trigger the use of SL SRB to send a discovery request message or monitor a discovery message, and select terminal A2 as a relay terminal to communicate with cell C2.

[0080] For another example, terminal A1 and terminal A2 are both in cell C1 terminal A2, the RSRP of the wireless signal of cell C1 measured by terminal A1 is less than the second threshold, and the RSRP of the wireless signal of cell C1 measured by terminal A2 is greater than or equal to the second threshold, terminal A1 can trigger the use of SL SRB to send a discovery request message or monitor a discovery message, and select terminal A2 as a relay terminal to communicate with cell C1.

[0081] Exemplarily, in the side communication scenario, whether to trigger sending a discovery request message or listening to a discovery message can be determined based on the positional relationship, signal strength, etc. of the first terminal, the second terminal, and the third terminal. Assume that the first terminal is far away from the third terminal, the signal strength of the third terminal is measured to be low, and the first terminal is close to the second terminal, and the signal strength of the second terminal is measured to be high. In addition, the second terminal is close to the third terminal, and the signal strength of the third terminal is measured to be high. The first terminal can trigger sending a discovery request message or listening to a discovery message to determine whether the second terminal can be used as a relay terminal to communicate with the network device.

[0082] In the embodiment of the present application, the second terminal for the first terminal to perform relay selection may be one or more, which is flexibly determined according to the actual application scenario and is not limited in the present application.

[0083] Optionally, in an embodiment of the present application, the medium access control (MAC) protocol data unit (PDU) including the discovery request message includes the logical channel identity (LCID) of the selected SL SRB.

[0084] For example, the correspondence between LCID and SL SRB may include: LCID=0 corresponds to SRB0, LCID=1 corresponds to SRB1, LCID=2 corresponds to SRB2, and LCID=3 corresponds to SRB3. LCID may also be represented in binary. For example, LCID 0 is represented as 000000; LCID 2 is represented as 000001; LCID 2 is represented as 000010; LCID 3 is represented as 000011, etc.

[0085] Optionally, in the embodiment of the present application, the selected SL SRB is SRB0. The first terminal may send a discovery request message and receive a discovery message through SRB0.

[0086] For example, the LCID of SRB0 is 0. When the first terminal triggers the sending of a discovery request message, a Packet Data Convergence Protocol (PDCP) PDU can be generated, and the PDCP PDU can include the discovery request message to be sent. The PDCP PDU first goes to the RLC (Radio Link Control) layer, and the UM (Unacknowledged Mode) sending method is adopted in the RLC layer. Then, it is converted to MAC PDU at the MAC layer, and LCID 0 can be added to the MAC PDU. Then, the MAC PDU can be sent directly on the PSSCH.

[0087] The above-mentioned SRB0 is only an example and not a limitation. Other selected SL SRBs can also be added to the MAC PDU. For example, a new SL SRB type is added, and the new SL SRB is identified by an LCID in the range of 20 to 63. The first terminal can send a discovery request message and receive a discovery message through the new SL SRB. In addition, if a new SL SRB is used, one implementation method can be transparent to the PDCP and RLC layers, without a PDCP protocol header and an RLC layer protocol header, that is, RLC TM (Transparent Mode) is used.

[0088] Optionally, in the embodiment of the present application, the first terminal sends a discovery request message through the SL SRB, including:

[0089] The first terminal sends the discovery request message on a sidelink shared channel PSSCH. The wireless resource pool associated with the PSSCH includes configuration information of a sidelink control channel PSCCH. The PSCCH is a control channel when sending the PSSCH.

[0090] For example, the first terminal transmits a SL SRB including a discovery request message to the second terminal on the PSSCH, and receives a SL SRB including a discovery message from the second terminal on the PSSCH.

[0091] Optionally, in the embodiment of the present application, the method further includes determining the wireless configuration parameters of the first terminal in at least one of the following ways:

[0092] When the first terminal is out of coverage of the network device, the first terminal adopts pre-configured wireless configuration parameters;

[0093] When the first terminal is within the coverage of the network device, the first terminal adopts the wireless configuration parameters broadcast by the network device.

[0094] In the embodiment of the present application, the wireless configuration parameters may include various wireless resources and wireless parameters, etc. For example, the wireless configuration parameters may include the wireless resource pool associated with the above-mentioned PSSCH.

[0095] Optionally, in the embodiment of the present application, when the first terminal is within the coverage of the network device, the first terminal adopts the wireless configuration parameters broadcast by the network device, including at least one of the following:

[0096] When the first terminal is within the coverage of the network device and the first terminal is in an RRC idle state, the first terminal adopts the wireless configuration parameters broadcast by the network device;

[0097] When the first terminal is within the coverage of the network device and is in an RRC connected state, the first terminal adopts the wireless resources and parameters broadcast by the network device, or the wireless configuration parameters dedicated to the first terminal.

[0098] In an embodiment of the present application, during the relay discovery process, the first terminal receives a discovery message through the SL SRB, or sends a discovery request message, and can multiplex PSSCH and PSCCH instead of using the side link discovery channel to transmit the discovery message. Therefore, there is no need to add new transmission channels and physical channels, which can reduce system complexity and reduce design and R&D costs.

[0099] Figure 3 is a schematic flow chart of a relay discovery method 300 according to another embodiment of the present application. The method may optionally be applied to Figure 1 The system shown in FIG. 1 is a system shown in FIG. 1 , but is not limited thereto. The same descriptions as those of method 200 in this embodiment have the same meanings and are not repeated here. The method in this embodiment includes at least part of the following contents.

[0100] S310: The second terminal sends a discovery message to the first terminal through a sidelink signaling radio bearer (SL SRB), so that the first terminal parses the discovery message to determine whether to select the second terminal as its relay terminal.

[0101] Exemplarily, in the relay discovery process, the second terminal can send a discovery message to the first terminal through the SL SRB, and can reuse the existing transmission channels and physical channels of the sidelink communication. For example, PSSCH, PSCCH, etc. Therefore, in the relay discovery process, the sidelink discovery channel may not be used to transmit the discovery message, and there is no need to add a new transmission channel and physical channel, which can reduce the complexity of the system.

[0102] Exemplarily, the discovery message sent by the second terminal may include information about various services supported by the second terminal. If the first terminal parses the discovery message and determines that the second terminal can serve as a relay for the first terminal (for example, finds the service of interest in the discovery message), and the wireless signal strength of the second terminal obtained by parsing the discovery message is higher than a set first threshold, the second terminal can be selected as its relay terminal. The first threshold can be set according to the device characteristics of the first terminal and / or the second terminal.

[0103] Optionally, in the embodiment of the present application, the second terminal sends a discovery message to the first terminal through the SL SRB, further comprising:

[0104] The second terminal periodically sends a discovery announcement message to the first terminal through the SL SRB.

[0105] Optionally, in an embodiment of the present application, the discovery announcement message includes at least a sending period.

[0106] Optionally, in an embodiment of the present application, the sending period is equal to the period of the wireless resources for sending the discovery announcement message.

[0107] Optionally, in an embodiment of the present application, the period of the wireless resource is a period of pre-configured wireless resources configured by the network, or a period of wireless resources obtained by the second terminal through automatic acquisition.

[0108] Optionally, in an embodiment of the present application, the method further includes: the second terminal receives a discovery request message sent by the first terminal via SLSRB. Optionally, this step may be before S310. In this case, S310, the second terminal sends a discovery message to the first terminal via SL SRB, and further includes: the second terminal sends a discovery response message to the first terminal via SL SRB.

[0109] An exemplary method includes: the first terminal first sends a discovery request message to the second terminal through the SL SRB. After receiving the discovery request message, the second terminal sends a discovery message to the first terminal through the SL SRB. The first terminal selects a relay terminal based on the discovery message sent by the second terminal in response to the discovery request message.

[0110] An exemplary method includes that the second terminal periodically sends a discovery message to the first terminal via the SL SRB. This method does not need to trigger the second terminal to send a discovery message via a received discovery request message. The first terminal selects a relay terminal based on the discovery message periodically sent by the second terminal.

[0111] Optionally, in an embodiment of the present application, the second terminal is within the coverage of the network device.

[0112] Exemplarily, in the scenario of uplink communication, whether to trigger sending a discovery request message or listening to a discovery message can be determined based on the positional relationship between the first terminal and the network device, signal strength, etc. Assume that the first terminal is outside the coverage of the network device, and the second terminal is within the coverage of the network device. The second terminal can maintain a good communication connection with the network device, and the first terminal can trigger sending a discovery request message or listening to a discovery message to determine whether the second terminal can be used as a relay terminal to communicate with the network device.

[0113] Exemplarily, in the side communication scenario, whether to trigger sending a discovery request message or listening to a discovery message can be determined based on the positional relationship, signal strength, etc. of the first terminal, the second terminal, and the third terminal. Assume that the first terminal is far away from the third terminal, the signal strength of the third terminal is measured to be low, and the first terminal is close to the second terminal, and the signal strength of the second terminal is measured to be high. In addition, the second terminal is close to the third terminal, and the signal strength of the third terminal is measured to be high. The first terminal can trigger sending a discovery request message or listening to a discovery message to determine whether the second terminal can be used as a relay terminal to communicate with the network device.

[0114] Optionally, in an embodiment of the present application, the MAC PDU including the discovery request message includes the LCID of the selected SL SRB.

[0115] Optionally, in the embodiment of the present application, the selected SL SRB is SRB0, and the LCID of SRB0 is 0. The second terminal may receive a discovery request message and send a discovery message through SRB0.

[0116] The above SRB0 is only an example and not a limitation. Other selected SL SRBs may also be added to the MAC PDU. For example, a new SL SRB type is added and the new SL SRB is identified by an LCID in the range of 20 to 63. The second terminal may receive a discovery request message and send a discovery message through the new SL SRB.

[0117] Optionally, in the embodiment of the present application, the second terminal receives the discovery request message sent by the first terminal through the SL SRB, further comprising:

[0118] The second terminal receives the discovery request message on a sidelink shared channel PSSCH, and a wireless resource pool associated with the PSSCH includes configuration information of a sidelink control channel PSCCH, where the PSCCH is a control channel when sending the PSSCH.

[0119] For example, the second terminal receives the SL SRB including the discovery request message from the first terminal on the PSSCH, and sends the SL SRB including the discovery message to the first terminal on the PSSCH.

[0120] Optionally, in the embodiment of the present application, the method further includes determining the wireless configuration parameters of the second terminal in at least one of the following ways:

[0121] When the second terminal is in an RRC idle state, the second terminal adopts the radio configuration parameters broadcast by a network system message;

[0122] When the second terminal is in an RRC connected state, the second terminal adopts the wireless configuration parameters broadcast by the network device, or the network device configures dedicated wireless configuration parameters for the second terminal.

[0123] For a specific example of the second terminal executing the method 300 of this embodiment, reference may be made to the related description about the second terminal in the above method 200, which will not be described again for the sake of brevity.

[0124] Since the signaling radio bearer will be mapped to another transmission channel, namely SL-SCH (Sidelink Shared Channel), together with the data radio bearer, there is no concept of a logical channel in the information sent on SL-DCH. The relay discovery method of the embodiment of the present application does not require the addition of a new SL-DCH channel. In an application example, a remote terminal (Remote UE) is connected to a wireless network node or another Remote UE through one or more relay terminals (Relay UE). The point-to-point connection between the Remote UE and the Relay UE can be connected through the PC5 interface defined in the 3GPP specification.

[0125] Before establishing a point-to-point connection with a Relay UE, the Remote UE needs to discover and select the Relay UE. There are two modes for discovering and selecting the Relay UE:

[0126] Mode A: Relay UE periodically sends discovery messages. Logically, this message tells the remote UE, "I am a relay UE that supports certain services."

[0127] Mode B: The Remote UE first sends a discovery request message. Logically, this message is asking, "Relay UE, are you there?" If the Relay UE receives this message, it will send the discovery message mentioned in Mode A above.

[0128] Discovery messages and discovery request messages can be sent via the sidelink signaling radio bearer on the PC5 interface of 3GPP NR. This sidelink signaling radio bearer can be an already defined sidelink signaling radio bearer, such as SRB0; or it can be different from the already defined sidelink signaling radio bearer. If it is the latter, new default radio parameters can be defined for this sidelink signaling radio bearer in the 3GPP standard specification, and it can be mapped to the SL-SCH (Sidelink Shared Channel) transport channel like the already defined sidelink signaling radio bearer, and the SL-SCH will be sent via the PSSCH (Physical Sidelink Shared Channel).

[0129] Example 1: UE to network relay

[0130] like Figure 4As shown, it is assumed that UE A and UE B both support the 3GPP NR PC5 interface protocol and the 3GPP NR Uu interface protocol. UE A and UE B have been authenticated by the network when there is network coverage, wherein UE A is authenticated as being able to access the wireless network through a relay UE, that is, UE A is authorized as a Remote UE. UE B is authenticated as being able to work as a relay node, that is, UE B can be a relay UE. In addition, UE A and UE B are both authorized to send and receive messages related to relay discovery, such as discovery messages and discovery request messages.

[0131] like Figure 5 As shown, when UE B works in mode B, when UE A is out of network coverage and needs to connect to the network, it will send a discovery request message. After receiving the discovery request message from UE A, UE B sends a discovery message such as a discovery response message.

[0132] like Figure 6 As shown, UE B may also work in mode A, that is, when no discovery request message is received, it may also periodically send a discovery message, such as a discovery announcement message.

[0133] The content of the message sent by the relay UE in mode A may be different from that of the message sent by the relay UE in mode B. For example, the relay UE in mode A periodically sends a discovery announcement message. For another example, the relay UE in mode B sends a discovery response message after receiving a discovery request message.

[0134] UE B must be within the coverage of the network. When UE B is in the RRC_IDLE state, UE B can use the radio resources and radio configuration parameters broadcast by the network system message. When UE B is in the RRC_CONNECTED state, in addition to the broadcast radio resources and radio configuration parameters, the network can also configure dedicated radio resources for UE B, such as configuring periodic pre-configured radio resources for transmission. If UE A is in Figure 1 If the UE A is outside the network coverage shown, it can only rely on pre-configured wireless resources and parameters. UE A can also be within the coverage of the network and use the wireless resources and configuration parameters broadcast by the network. In this case, UE A needs to measure the wireless signal of the current cell. For example, only when the RSRP of the wireless signal is less than a predetermined threshold, the discovery request message is triggered or the discovery message is directly monitored.

[0135] The wireless parameters of all SRBs of the 3GPP NR PC5 interface are fixed in the protocol. When UE A or UE B is triggered to send a discovery request message or a discovery message, a PDCP PDU is generated, which contains the above discovery message or discovery request message. This PDCP PDU uses a format with a sequence number length of 12 bits and does not contain MAC-I (integrity message authentication code) information related to integrity protection. At the RLC layer, this format uses a sequence number length of 6 bits and is sent in UM mode. At the MAC layer, it is identified according to the LCID of the selected SL SRB, such as SRB0 (ie, LCID = 0). Then this MAC PDU is sent directly on the PSSCH according to the wireless resources mentioned above. The wireless resources also include configuration information of the side control channel PSCCH.

[0136] When UE A finds that the discovery message sent by UE B contains the service it is interested in and the measured wireless signal strength of UE B is higher than a threshold specified by a certain network, it will select UE B as its relay and continue the subsequent relay operation.

[0137] Example 2: UE-to-UE relay

[0138] like Figure 7 As shown, it is assumed that UE A, UE B and UE C all support the 3GPP NR PC5 interface protocol. UE A, UE B and UE C have been authenticated by the network when there is network coverage, where UE A and UE C are authenticated to access the wireless network through relay UE, that is, UE A and UE C are authorized to act as Remote UE. UE B is authenticated to act as a relay node. UE A, UE B and UE C are all authorized to send and receive messages related to relay discovery, such as discovery messages and discovery request messages.

[0139] When UE A needs to connect to UE C, it sends a discovery request message. After receiving the discovery request message from UE A, UE B sends a discovery message. UE B can also work in mode A, that is, when it does not receive a discovery request message, it can also periodically send a discovery message.

[0140] The radio parameters of all SRBs of the 3GPP NR PC5 interface are fixed in the protocol. When UE A, UE C or UEB is triggered to send a discovery request message or a discovery message, a PDCP PDU is generated, which contains the above discovery message or discovery request message. This PDCP PDU uses a format with a sequence number length of 12 bits and does not contain MAC-I (integrity message authentication code) information related to integrity protection. At the RLC layer, this format uses a sequence number length of 6 bits and is sent in UM mode. At the MAC layer, it is identified according to the LCID of the selected SL SRB, such as SRB0 (ie, LCID = 0). Then this MAC PDU is sent directly on the PSSCH according to the radio resources mentioned above. The radio resources also include configuration information of the side control channel PSCCH.

[0141] When UE A or UE C finds that the discovery message sent by UE B contains the service they are interested in, and the measured wireless signal strength of UE B is higher than a threshold specified by a certain network, they will select this UE as their relay.

[0142] The choice of these three UEs between pre-configured wireless resources and parameters, broadcasted wireless resources and parameters, and network-configured wireless resources and parameters is related to the network coverage of the UE itself. If a UE is out of network coverage, pre-configured wireless resources and parameters are used. If it is within network coverage but in RRC_IDLE state, network-broadcasted wireless resources and parameters can be used; if it is in RRC_CONNECTED state, either network-broadcasted wireless resources and parameters or dedicated wireless resources and parameters are used. Wireless resources and parameters can be collectively referred to as wireless configuration parameters.

[0143] Figure 8 4 is a schematic block diagram of a first terminal 400 according to an embodiment of the present application. The first terminal 400 may include:

[0144] The receiving unit 410 is configured to receive a discovery message sent by the second terminal via the SL SRB;

[0145] The processing unit 420 is configured to parse the discovery message to determine whether to select the second terminal as its relay terminal.

[0146] Optionally, in an embodiment of the present application, the processing unit 420 is also used to parse the discovery message, determine that the second terminal can serve as a relay for the first terminal, and when the wireless signal strength of the second terminal is measured to be higher than a first threshold, select the second terminal as its own relay terminal.

[0147] Optionally, in this embodiment of the present application, the receiving unit 410 is further configured to receive a discovery announcement message periodically sent by the second terminal via the SL SRB.

[0148] Optionally, in an embodiment of the present application, the discovery announcement message includes at least a sending period.

[0149] Optionally, in an embodiment of the present application, the receiving unit is further configured to, after acquiring the sending cycle, periodically receive a discovery announcement message of the second terminal through the SL SRB based on the sending cycle.

[0150] Optionally, in an embodiment of the present application, the sending period is equal to the period of the wireless resources for sending the discovery announcement message.

[0151] Optionally, in an embodiment of the present application, the period of the wireless resource is a period of pre-configured wireless resources configured by the network, or a period of wireless resources obtained by the second terminal through automatic acquisition.

[0152] Optionally, in the embodiment of the present application, Fig. 9 As shown, the first terminal also includes:

[0153] The sending unit 430 is configured to send a discovery request message via the SL SRB;

[0154] The receiving unit 410 is further configured to receive a discovery response message sent by the second terminal via the SL SRB.

[0155] Optionally, in the embodiment of the present application, the first terminal further includes: a triggering unit 440, configured to trigger sending a discovery request message or monitoring a discovery message in at least one of the following situations:

[0156] The first terminal is outside the coverage of the network device and needs to be connected to the network device, and the second terminal is within the coverage of the network device;

[0157] The first terminal is within the coverage of the network device, but the measured reference signal received power RSRP of the wireless signal of the network device to which the first terminal is connected is less than the second threshold, and the second terminal is within the coverage of the network device;

[0158] The first terminal needs to be connected to a third terminal.

[0159] Optionally, in an embodiment of the present application, the MAC PDU including the discovery request message includes the LCID of the selected SL SRB.

[0160] Optionally, in an embodiment of the present application, the selected SL SRB is SRB0, and the LCID of SRB0 is 0.

[0161] Optionally, in an embodiment of the present application, the sending unit is also used to send the discovery request message on the sidelink shared channel PSSCH, and the wireless resource pool associated with the PSSCH includes configuration information of the sidelink control channel PSCCH, and the PSCCH is the control channel when sending the PSSCH.

[0162] Optionally, in the embodiment of the present application, the first terminal further includes at least one of the following:

[0163] A first configuration unit 450, configured to use a preconfigured wireless configuration parameter when the first terminal is out of coverage of the network device;

[0164] The second configuration unit 460 is configured to adopt the wireless configuration parameters broadcast by the network device when the first terminal is within the coverage of the network device.

[0165] Optionally, in the embodiment of the present application, the second configuration unit is further configured to perform at least one of the following:

[0166] When the first terminal is within the coverage of the network device and the first terminal is in an RRC idle state, the first terminal adopts the wireless configuration parameters broadcast by the network device;

[0167] When the first terminal is within the coverage of the network device and is in an RRC connected state, the first terminal adopts the wireless resources and parameters broadcast by the network device, or the wireless configuration parameters dedicated to the first terminal.

[0168] The first terminal 400 of the embodiment of the present application can implement the corresponding functions of the first terminal in the aforementioned method embodiment. The corresponding processes, functions, implementation methods and beneficial effects of each module (submodule, unit or component, etc.) in the first terminal 400 can be found in the corresponding description in the aforementioned method embodiment, which will not be repeated here.

[0169] It should be noted that the functions described in each module (sub-module, unit or component, etc.) in the first terminal 400 of the application embodiment can be implemented by different modules (sub-module, unit or component, etc.) or by the same module (sub-module, unit or component, etc.).

[0170] Fig.10 is a schematic block diagram of a second terminal 500 according to an embodiment of the present application. The second terminal 500 may include:

[0171] The sending unit 510 is configured to send a discovery message to the first terminal via a side link signaling radio bearer SL SRB, so that the first terminal parses the discovery message to determine whether to select the second terminal as its relay terminal.

[0172] Optionally, in this embodiment of the present application, the sending unit 510 is further configured to periodically send a discovery announcement message to the first terminal via the SL SRB.

[0173] Optionally, in an embodiment of the present application, the discovery announcement message includes at least a sending period.

[0174] Optionally, in an embodiment of the present application, the sending period is equal to the period of the wireless resources for sending the discovery announcement message.

[0175] Optionally, in an embodiment of the present application, the period of the wireless resource is a period of pre-configured wireless resources configured by the network, or a period of wireless resources obtained by the second terminal through automatic acquisition.

[0176] Optionally, in the embodiment of the present application, Fig.11 As shown, the second terminal also includes:

[0177] The receiving unit 520 is configured to receive a discovery request message sent by the first terminal through the SL SRB;

[0178] The sending unit 410 is further configured to send a discovery response message to the first terminal via the SL SRB.

[0179] Optionally, in an embodiment of the present application, the second terminal is within the coverage of the network device.

[0180] Optionally, in an embodiment of the present application, the MAC PDU including the discovery request message includes the LCID of the selected SL SRB.

[0181] Optionally, in an embodiment of the present application, the selected SL SRB is SRB0, and the LCID of SRB0 is 0.

[0182] Optionally, in an embodiment of the present application, the receiving unit 520 is also used to receive the discovery request message on the sidelink shared channel PSSCH, and the wireless resource pool associated with the PSSCH includes configuration information of the sidelink control channel PSCCH, which is the control channel when sending the PSSCH.

[0183] Optionally, in the embodiment of the present application, the second terminal further includes:

[0184] A first configuration unit 530 is configured to use a radio configuration parameter broadcast by a network system message when the second terminal is in an RRC idle state;

[0185] The second configuration unit 540 is configured to, when the second terminal is in an RRC connected state, adopt the wireless configuration parameters broadcast by the network device, or the network device configures dedicated wireless configuration parameters for the second terminal.

[0186] The second terminal 500 of the embodiment of the present application can implement the corresponding functions of the second terminal in the aforementioned method embodiment. The corresponding processes, functions, implementation methods and beneficial effects of each module (submodule, unit or component, etc.) in the second terminal 500 can be found in the corresponding description in the aforementioned method embodiment, which will not be repeated here.

[0187] It should be noted that the functions described in each module (sub-module, unit or component, etc.) in the second terminal 500 of the application embodiment can be implemented by different modules (sub-module, unit or component, etc.) or by the same module (sub-module, unit or component, etc.).

[0188] Fig.12 6 is a schematic structural diagram of a communication device 600 according to an embodiment of the present application. The communication device 600 includes a processor 610, and the processor 610 can call and run a computer program from a memory to enable the communication device 600 to implement the method in the embodiment of the present application.

[0189] Alternatively, if Fig.12 As shown, the communication device 600 may further include a memory 620. The processor 610 may call and run a computer program from the memory 620 to enable the communication device 600 to implement the method in the embodiment of the present application.

[0190] The memory 620 may be a separate device independent of the processor 610 , or may be integrated into the processor 610 .

[0191] Alternatively, if Fig.12 As shown, the communication device 600 may further include a transceiver 630, and the processor 610 may control the transceiver 630 to communicate with other devices, specifically, may send information or data to other devices, or receive information or data sent by other devices.

[0192] The transceiver 630 may include a transmitter and a receiver. The transceiver 630 may further include an antenna, and the number of the antennas may be one or more.

[0193] Optionally, the communication device 600 may be a network device of an embodiment of the present application, and the communication device 600 may implement the corresponding processes implemented by the network device in each method of the embodiment of the present application, which will not be described in detail here for the sake of brevity.

[0194] Optionally, the communication device 600 may be a terminal device of an embodiment of the present application, and the communication device 600 may implement the corresponding processes implemented by the first terminal or the second terminal in each method of the embodiment of the present application, which will not be described again for the sake of brevity.

[0195] Fig.13 7 is a schematic structural diagram of a chip 700 according to an embodiment of the present application. The chip 700 includes a processor 710, and the processor 710 can call and run a computer program from a memory to implement the method in the embodiment of the present application.

[0196] Alternatively, if Fig.13 As shown, the chip 700 may further include a memory 720. The processor 710 may call and run a computer program from the memory 720 to implement the method executed by the terminal device or the network device in the embodiment of the present application.

[0197] The memory 720 may be a separate device independent of the processor 710 , or may be integrated into the processor 710 .

[0198] Optionally, the chip 700 may further include an input interface 730. The processor 710 may control the input interface 730 to communicate with other devices or chips, and specifically, may obtain information or data sent by other devices or chips.

[0199] Optionally, the chip 700 may further include an output interface 740. The processor 710 may control the output interface 740 to communicate with other devices or chips, and specifically, may output information or data to other devices or chips.

[0200] Optionally, the chip can be applied to the network device in the embodiments of the present application, and the chip can implement the corresponding processes implemented by the network device in each method of the embodiments of the present application. For the sake of brevity, they will not be repeated here.

[0201] Optionally, the chip can be applied to the terminal device in the embodiments of the present application, and the chip can implement the corresponding processes implemented by the terminal device in the various methods of the embodiments of the present application. For the sake of brevity, they will not be repeated here.

[0202] The chips used in the network device and the terminal device may be the same chip or different chips.

[0203] It should be understood that the chip mentioned in the embodiments of the present application can also be called a system-level chip, a system chip, a chip system or a system-on-chip chip, etc.

[0204] The processor mentioned above may be a general-purpose processor, a digital signal processor (DSP), a field programmable gate array (FPGA), an application specific integrated circuit (ASIC) or other programmable logic devices, transistor logic devices, discrete hardware components, etc. Among them, the general-purpose processor mentioned above may be a microprocessor or any conventional processor, etc.

[0205] The memory mentioned above may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable ROM (PROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM) or a flash memory. The volatile memory may be a random access memory (RAM).

[0206] It should be understood that the above-mentioned memory is exemplary but not restrictive. For example, the memory in the embodiments of the present application may also be static random access memory (static RAM, SRAM), dynamic random access memory (dynamic RAM, DRAM), synchronous dynamic random access memory (synchronous DRAM, SDRAM), double data rate synchronous dynamic random access memory (double data rate SDRAM, DDR SDRAM), enhanced synchronous dynamic random access memory (enhanced SDRAM, ESDRAM), synchronous link dynamic random access memory (synch link DRAM, SLDRAM) and direct memory bus random access memory (Direct Rambus RAM, DR RAM), etc. That is to say, the memory in the embodiments of the present application is intended to include but not limited to these and any other suitable types of memory.

[0207] Fig.148 is a schematic block diagram of a communication system 800 according to an embodiment of the present application. The communication system 800 includes a first terminal 810 and a second terminal 820.

[0208] The first terminal is used to receive a discovery message sent by the second terminal through the SL SRB; and parse the discovery message to determine whether to select the second terminal as its own relay terminal.

[0209] The second terminal is used to send a discovery message to the first terminal through the SL SRB, so that the first terminal parses the discovery message to determine whether to select the second terminal as its relay terminal.

[0210] The first terminal 810 may be used to implement the corresponding functions implemented by the first terminal in the above method, and the second terminal 820 may be used to implement the corresponding functions implemented by the second terminal in the above method. For the sake of brevity, they will not be described in detail here.

[0211] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function in accordance with the embodiment of the present application is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions can be transmitted from a website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (Digital Subscriber Line, DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website site, computer, server or data center. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server, data center, etc. that contains one or more available media integrations. The available medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a DVD), or a semiconductor medium (eg, a solid state disk (SSD)).

[0212] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0213] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0214] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A relay discovery method, comprising: The first terminal receives a discovery message sent by the second terminal through a side link signaling radio bearer SL SRB; The first terminal parses the discovery message to determine whether to select the second terminal as its relay terminal; The method further includes: the first terminal sending a discovery request message through the SL SRB; The first terminal receives a discovery message sent by the second terminal via the SL SRB, including: the first terminal receives a discovery response message sent by the second terminal via the SL SRB.

2. The method according to claim 1, wherein: The first terminal parses the discovery message to determine whether to select the second terminal as its relay terminal, including: The first terminal parses the discovery message, determines that the second terminal can serve as a relay for the first terminal, and selects the second terminal as its own relay terminal when the measured wireless signal strength of the second terminal is higher than a first threshold.

3. The method according to claim 1 or 2, wherein: The first terminal receiving the discovery message sent by the second terminal through the SL SRB also includes: The first terminal receives a discovery announcement message periodically sent by the second terminal through the SL SRB.

4. The method according to claim 3, wherein: The discovery announcement message at least includes a sending period.

5. The method according to claim 4, wherein: The method further comprises: After acquiring the sending cycle, the first terminal periodically receives the discovery announcement message of the second terminal through the SL SRB based on the sending cycle.

6. The method according to claim 4 or 5, wherein: The sending period is equal to a period of wireless resources for sending the discovery announcement message.

7. The method according to claim 6, wherein: The period of the wireless resources is a period of pre-configured wireless resources configured by the network, or a period of wireless resources obtained by the second terminal through automatic acquisition.

8. The method according to claim 1, wherein: The first terminal triggers sending a discovery request message or monitoring a discovery message, including at least one of the following situations: The first terminal is outside the coverage of the network device and needs to be connected to the network device, and the second terminal is within the coverage of the network device; The first terminal is within the coverage of the network device, but the measured reference signal received power RSRP of the wireless signal of the network device to which the first terminal is connected is less than a second threshold, and the second terminal is within the coverage of the network device; The first terminal needs to be connected to a third terminal.

9. The method according to claim 1 or 8, wherein: The MAC PDU including the discovery request message includes the LCID of the selected SL SRB.

10. The method according to claim 9, wherein: The first terminal sends a discovery request message through a sidelink signaling radio bearer, including: The first terminal sends the discovery request message on a sidelink shared channel PSSCH, and the wireless resource pool associated with the PSSCH includes configuration information of a sidelink control channel PSCCH, and the PSCCH is a control channel when sending the PSSCH.

11. A relay discovery method, comprising: The second terminal sends a discovery message to the first terminal through a side link signaling radio bearer SL SRB, so that the first terminal parses the discovery message to determine whether to select the second terminal as its relay terminal; The method further includes: the second terminal receiving a discovery request message sent by the first terminal through the SL SRB; The second terminal sends a discovery message to the first terminal through the SL SRB, and also includes: the second terminal sends a discovery response message to the first terminal through the SLSRB.

12. A terminal device, comprising: A processor and a memory, the memory being used to store a computer program, the processor being used to call and run the computer program stored in the memory, so that the terminal device executes the method as claimed in any one of claims 1 to 10.

13. A terminal device, comprising: A processor and a memory, the memory being used to store a computer program, the processor being used to call and run the computer program stored in the memory so that the terminal device executes the method as claimed in claim 11.

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