Relay communication method and apparatus

Abstract

The application relates to a relay communication method and device, the method comprising: a first terminal selecting a relay terminal meeting the demand of the first terminal based on a first trigger condition; wherein the first terminal and the relay terminal are in a multi-hop relay link, and the first trigger condition is related to a link state. In the embodiment of the application, the selection of the relay triggered based on the trigger condition can form a multi-hop relay link, and the communication reliability and the communication range can be improved.

Description

Cross-references to related applications

[0001] This application is a divisional application of Chinese patent application entitled "Relay Communication Method and Apparatus" filed on July 21, 2023, with application number "202380097539.0". Technical Field

[0002] This application relates to the field of communications, and more specifically, to a relay communication method and device. Background Technology

[0003] With the development of wireless communication technology, the 3rd Generation Partnership Project (3GPP) introduced relays. Remote terminals and networks can be connected via relay terminals, such as in User Equipment (UE) to Network (U2N) relays. Source terminals and destination terminals can also be connected via relay terminals, such as in User Equipment to UE (U2U) relays. Communication based on relay terminals can extend communication distances and improve communication reliability. Summary of the Invention

[0004] This application provides a relay communication method and device that can improve communication reliability and range.

[0005] This application provides a relay communication method, including: a first terminal selecting a relay terminal that meets the requirements of the first terminal based on a first triggering condition; wherein the first terminal and the relay terminal are in a multi-hop relay link, and the first triggering condition is related to the link status.

[0006] This application provides a relay communication method, including: a second terminal sending a link status; wherein the link status is related to a first triggering condition, the first triggering condition being used to trigger a first terminal to select a relay terminal that meets the requirements of the first terminal, and the first terminal, the second terminal, and the relay terminal are in a multi-hop relay link.

[0007] This application provides a first terminal, including: a processing unit, configured to select a relay terminal that meets the requirements of the first terminal based on a first triggering condition; wherein the first terminal and the relay terminal are in a multi-hop relay link, and the first triggering condition is related to the link status.

[0008] This application provides a second terminal, including: a sending unit for sending link status; wherein the link status is related to a first triggering condition, the first triggering condition being used to trigger a first terminal to select a relay terminal that meets the requirements of the first terminal, and the first terminal, the second terminal, and the relay terminal are in a multi-hop relay link.

[0009] This application provides a terminal device including a processor and a memory. The memory stores a computer program, and the processor calls and runs the computer program stored in the memory to enable the terminal device to perform the relay communication method described above.

[0010] This application provides a chip for implementing the relay communication method described above. Specifically, the chip includes a processor for retrieving and running a computer program from a memory, causing a device equipped with the chip to execute the relay communication method described above.

[0011] This application provides a computer-readable storage medium for storing a computer program, which, when run by a device, causes the device to perform the aforementioned relay communication method.

[0012] This application provides a computer program product, including computer program instructions that cause a computer to execute the above-described relay communication method.

[0013] This application provides a computer program that, when run on a computer, causes the computer to perform the above-described relay communication method.

[0014] The embodiments of this application can form multi-hop relay links by triggering relay selection based on triggering conditions, which can improve communication reliability and communication range. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of an application scenario according to an embodiment of this application.

[0016] Figure 2A This is a schematic diagram of 3GPP transmission mode 3.

[0017] Figure 2B This is a schematic diagram of 3GPP transmission mode 4.

[0018] Figure 3 This is a schematic diagram of UE-to-UE relay.

[0019] Figure 4 This is a schematic diagram of the process for establishing a connection between a UE and a UE relay.

[0020] Figure 5 This is a schematic diagram of the UE architecture in UE-to-UE relay.

[0021] Figure 6 This is a schematic flowchart of a relay communication method according to an embodiment of this application.

[0022] Figure 7 This is a schematic flowchart of a relay communication method according to another embodiment of this application.

[0023] Figure 8 This is a schematic flowchart of a relay communication method according to another embodiment of this application.

[0024] Figure 9 This is a schematic flowchart of a relay communication method according to an embodiment of this application.

[0025] Figure 10 This is a schematic flowchart of centralized relay selection / reselection according to Embodiment 2 of this application.

[0026] Figure 11 This is a schematic flowchart of distributed relay selection / reselection according to Embodiment 3 of this application.

[0027] Figure 12 This is a schematic block diagram of a first terminal according to an embodiment of this application.

[0028] Figure 13 This is a schematic block diagram of a first terminal according to another embodiment of this application.

[0029] Figure 14 This is a schematic block diagram of a second terminal according to an embodiment of this application.

[0030] Figure 15 This is a schematic structural diagram of a communication device according to an embodiment of this application.

[0031] Figure 16 This is a schematic block diagram of a chip according to an embodiment of this application.

[0032] Figure 17 This is a schematic block diagram of a communication system according to an embodiment of this application. Detailed Implementation

[0033] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0034] The technical solutions of this application embodiment 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, evolution of NR system, LTE-based access to unlicensed spectrum (LTE-U) system, NR-based access to unlicensed spectrum (NR-U) system, Non-Terrestrial Networks (NTN) system, Universal Mobile Telecommunication System (UMTS), Wireless Local Area Networks (WLAN), and Wireless Fidelity (WF). Fidelity (WiFi), 5th-Generation (5G) communication systems, or other communication systems.

[0035] Traditional communication systems typically 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 communication but also, for example, device-to-device (D2D) communication, machine-to-machine (M2M) communication, machine-type communication (MTC), vehicle-to-vehicle (V2V) communication, or vehicle-to-everything (V2X) communication. The embodiments of this application can also be applied to these communication systems.

[0036] In one implementation, the communication system in this application embodiment can be applied to a carrier aggregation (CA) scenario, a dual connectivity (DC) scenario, or a standalone (SA) network deployment scenario.

[0037] In one embodiment, the communication system in this application can be applied to unlicensed spectrum, wherein the unlicensed spectrum can also be considered as shared spectrum; or, the communication system in this application can also be applied to licensed spectrum, wherein the licensed spectrum can also be considered as non-shared spectrum.

[0038] This application describes 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.

[0039] Terminal devices can be stations (STAION, ST) in WLANs, cellular phones, cordless phones, Session Initiation Protocol (SIP) phones, Wireless Local Loop (WLL) stations, Personal Digital Assistant (PDA) devices, handheld devices with wireless communication capabilities, computing devices or other processing devices connected to a wireless modem, in-vehicle devices, wearable devices, terminal devices in next-generation communication systems such as NR networks, or terminal devices in future evolved Public Land Mobile Network (PLMN) networks, etc.

[0040] In the embodiments of this application, the terminal device can be deployed on land, including indoor or outdoor, handheld, wearable or vehicle-mounted; it can also be deployed on water (such as ships); and it can also be deployed in the air (such as airplanes, balloons and satellites).

[0041] In the embodiments of this application, the terminal device may be a mobile phone, a tablet computer, a computer with wireless transceiver capabilities, 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 care, 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.

[0042] By way of example and not limitation, in this embodiment, the terminal device can also be a wearable device. Wearable devices, also known as wearable smart devices, are a general term for devices that utilize wearable technology to intelligently design and develop everyday wearables, such as glasses, gloves, watches, clothing, and shoes. Wearable devices are portable devices that are worn directly on the body or integrated into the user's clothing or accessories. Wearable devices are not merely hardware devices, but also achieve powerful functions through software support, data interaction, and cloud interaction. Broadly speaking, wearable smart devices include those that are feature-rich, large in size, and can achieve complete or partial functions without relying on a smartphone, such as smartwatches or smart glasses, as well as those that focus on a specific type of application function and require the use of other devices such as smartphones, such as various smart bracelets and smart jewelry for vital sign monitoring.

[0043] In the embodiments of this application, the network device can be a device for communicating with mobile devices. The network device can be an access point (AP) in WLAN, a base station (BTS) in GSM or CDMA, a base station (NodeB, NB) in WCDMA, an evolved base station (eNB or eNodeB) in LTE, a relay station or access point, or a vehicle-mounted device, wearable device, or a network device (gNB) in an NR network, or a network device in a future evolved PLMN network or an NTN network, etc.

[0044] By way of example and not limitation, in this embodiment, the network device may have mobility characteristics; 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 located on land, water, or other similar locations.

[0045] In this embodiment, the network device can provide services to a cell. The terminal device communicates with the network device through the transmission resources (e.g., frequency domain resources, or spectrum resources) used by the cell. The cell can be the cell corresponding to the network device (e.g., a base station). The cell can belong to a macro base station or to a base station corresponding to a small cell. The small cell can include: metro cell, micro cell, pico cell, femto cell, etc. These small cells have the characteristics of small coverage area and low transmission power, and are suitable for providing high-speed data transmission services.

[0046] Figure 1 An exemplary communication system 100 is shown. The communication system includes a network device 110 and two terminal devices 120. In one embodiment, the communication system 100 may include multiple network devices 110, and the coverage area of ​​each network device 110 may include other numbers of terminal devices 120, which is not limited in this application embodiment.

[0047] In one embodiment, the communication system 100 may also include other network entities such as a Mobility Management Entity (MME) and an Access and Mobility Management Function (AMF), which are not limited in this application embodiment.

[0048] Network equipment can be further divided into access network equipment and core network equipment. That is, the wireless communication system also includes multiple core networks used to communicate with the access network equipment. Access network equipment can be evolved Node Bs (eNBs or e-NodeBs) in Long-Term Evolution (LTE), Next-Generation Radio (NR) (mobile communication system), or Authorized Auxiliary Access Long-Term Evolution (LAA-LTE) systems, such as macro base stations, micro base stations (also called "small base stations"), pico base stations, access points (APs), transmission points (TPs), or new generation Node Bs (gNodeBs).

[0049] It should be understood that devices with communication functions in the network / system of this application embodiment can be referred to as communication devices. Figure 1 Taking the communication system shown as an example, the communication equipment may include network devices and terminal devices with communication functions. The network devices and terminal devices may be specific devices in the embodiments of this application, which will not be described in detail here. The communication equipment may also include other devices in the communication system, such as network controllers, mobility management entities and other network entities, which are not limited in the embodiments of this application.

[0050] It should be understood that the terms "system" and "network" are often used interchangeably in this document. The term "and / or" in this document merely describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Furthermore, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0051] It should be understood that the term "instruction" mentioned in the embodiments of this application can be a direct instruction, an indirect instruction, or an indication of a relationship. For example, A instructing B can mean that A directly instructs B, such as B being able to obtain information through A; it can also mean that A indirectly instructs B, such as A instructing C, so B can obtain information through C; or it can mean that there is a relationship between A and B.

[0052] In the description of the embodiments of this application, the term "correspondence" may indicate that there is a direct or indirect correspondence between two things, or that there is an association between two things, or that there is a relationship of instruction and being instructed, configuration and being configured, etc.

[0053] To facilitate understanding of the technical solutions of the embodiments of this application, the relevant technologies of the embodiments of this application are described below. The following relevant technologies are optional solutions and can be combined with the technical solutions of the embodiments of this application in any way, and they all fall within the protection scope of the embodiments of this application.

[0054] I. Long Term Evolution (LTE) Device to Device (D2D) / V2X.

[0055] Device-to-device communication is a sidelink (SL) transmission technology based on D2D. Unlike the traditional cellular system where communication data is received or sent through base stations, the vehicle-to-everything (V2X) system uses direct terminal-to-terminal communication, which has higher spectral efficiency and lower transmission latency.

[0056] 3GPP includes two transmission modes: Mode 3 and Mode 4.

[0057] Mode 3: such as Figure 2A As shown, the terminal's transmission resources are allocated by the base station, and the terminal transmits data on the side link according to the resources allocated by the base station. The base station can allocate resources for a single transmission or for semi-static transmission to the terminal.

[0058] Mode 4: such as Figure 2B As shown, the vehicle terminal selects a resource from the resource pool for data transmission.

[0059] In 3GPP, D2D includes different phases: (1) Proximity based Service (ProSe): In Rel-12 / 13, device-to-device communication was studied for ProSe scenarios, which are mainly for public safety services.

[0060] In the neighboring service, by configuring the location of the resource pool in the time domain, such as making the resource pool discontinuous in the time domain, the UE can send / receive data discontinuously on the side link, thereby achieving the effect of saving power.

[0061] (2) Vehicle-to-everything (V2X) system: In Rel-14 / 15, the V2X system was studied for vehicle-to-vehicle communication scenarios, which mainly focused on vehicle-to-vehicle and vehicle-to-person communication services that are relatively fast-moving. In V2X, since the vehicle system has a continuous power supply, power efficiency is not the main issue; rather, data transmission latency is the primary concern. Therefore, the system design requires terminal devices to continuously send and receive data.

[0062] (3) Wearable devices, further enhancement to device-to-device (FeD2D): In Rel-14, this project studied the scenario of wearable devices accessing the network through mobile phones, mainly focusing on scenarios with low mobility and low power access.

[0063] In FeD2D, during the preliminary research phase, 3GPP concluded that the base station could configure the discontinuous reception (DRX) parameters of the remote terminal through a relay terminal. However, since the project did not proceed to the standardization phase, there was no conclusion on the specific details of how to configure DRX.

[0064] II. NR V2X.

[0065] Building upon LTE V2X, NR V2X extends beyond broadcast scenarios to include unicast and multicast scenarios, allowing for the research of V2X applications in these contexts.

[0066] Similar to LTE V2X, NR V2X also includes two resource granting modes: mode-1 and mode-2. Furthermore, a user may be in a hybrid mode, meaning they can acquire resources using both mode-1 and mode-2 simultaneously. This resource acquisition is indicated through sidelink granting, specifically by specifying the time-frequency location of the corresponding Physical Sidelink Control Channel (PSCCH) and Physical Sidelink Shared Channel (PSSCH) resources.

[0067] Unlike LTE V2X, which features non-feedback, UE-initiated Hybrid Automatic Repeat-reQuest (HARQ) retransmission, NR V2X introduces feedback-based HARQ retransmission, which is not limited to unicast communication but also includes multicast communication.

[0068] III. Side-to-side UE-2-UE relay technology.

[0069] like Figure 3 As shown, in Rel-17 ProSe, 3GPP includes U2U (UE-to-UE) relay functionality based on Layer 2 and Layer 3 relays. That is, the source UE connects to the target UE through the relay UE, and the relay UE transmits data between the source UE and the target UE.

[0070] The specific steps for establishing a connection are as follows: Figure 4 As shown. The source UE, relay UE, and target UE discover each other through discovery messages or direct communication request (DCR) messages. The relay UE can help the source UE forward discovery messages or DCR messages. After the source UE and target UE discover each other, they can select a relay, choose a suitable relay, and establish a connection with it. Then, the relay acts as the relay to establish an end-to-end direct communication interface (PC5) connection.

[0071] 3GPP Rel-17 includes Layer 2 terminal-to-terminal relays. For example... Figure 5 As shown, the adaptation layer (e.g., the Sidelink Relay Adaptation Protocol (SRAP) layer) is placed above the control plane and user plane Radio Link Control (RLC) sublayers between the relay UE and the source / target UE. The PC5 Service Data Adaptation Protocol (SDAP) / Packet Data Convergence Protocol (PDCP) and Radio Resource Control (RRC) terminate between the source and target UEs. The RLC, Medium Access Control (MAC), and Physical layer (PHY) terminate in each link (i.e., the link between the source and relay UEs and the link between the relay and target UEs). Whether the adaptation layer is also supported at the PC5 interface between the source and relay UEs is currently inconclusive.

[0072] The following is an example of L2 UE-to-UE relay: (1) The adaptation layer of the relay terminal supports side-link bearer mapping between PC5 RLC channels. For side-link relay services, different end-to-end bearers of the same remote UE and / or different remote UEs, such as signaling radio bearers (SRB) and data radio bearers (DRB), can be mapped N:1 and multiplexed on a PC5 RLC channel.

[0073] (2) The adaptation layer is used to support terminal identification for side services (multiplexing data from multiple terminals). The terminal PC5 radio bearer and the terminal identification information are included in the adaptation layer so that the target can associate received data packets of a specific PDCP entity associated with the radio bearer of the source terminal.

[0074] IV. UE to Network Relay.

[0075] The remote terminal performs measurement reporting, including information such as the relay terminal identifier, serving cell identifier, and Reference Signal Received Power (RSRP) measurement results in the reported information. When the remote terminal performs a link handover from a non-direct path to a direct path, the serving relay terminal can use SL-RSRP for sidelink measurements. When the remote terminal performs a link handover from a direct path to a non-direct path, Sidelink Discovery (SD)-RSRP can be used for sidelink measurements. Additionally, two new measurement reporting trigger events are defined for relay handover from the terminal to the network during measurement reporting: Event 1: When the link quality of the serving relay terminal is lower than the configured threshold, and optionally, the link quality of neighboring cells is higher than the configured threshold, the remote terminal performs measurement reporting. Event 2: When the link quality of the serving cell is lower than the configured threshold, and the link quality of the optional relay terminal is higher than the configured threshold, the remote terminal performs measurement reporting. In addition, a new timer is introduced to assist the remote terminal in performing the handover from a direct link to a non-direct link. When the remote terminal receives an RRC reconfiguration message indicating a handover from a direct link to a non-direct link, the remote terminal starts the timer. When the timer expires, the remote terminal performs an RRC re-establishment.

[0076] The relevant U2U / U2N relays are primarily in single-hop scenarios. For example, from the source UE through a relay UE to the target UE or gNB. This application embodiment can further enhance coverage through multi-hop relays. For example, from the source UE through relay UE1, relay UE2, etc., to the target UE or gNB. In multi-hop relay scenarios, the multi-hop relay selection process on the sidelink may be affected. The relay communication method provided in this application embodiment may include a multi-hop relay selection process in multi-hop relay scenarios.

[0077] Figure 6 This is a schematic flowchart of a relay communication method 600 according to an embodiment of this application. The method 600 can optionally be applied to... Figures 1 to 5 The system shown is not limited to this. The method includes at least a portion of the following.

[0078] S610. The first terminal selects a relay terminal that meets its requirements based on a first triggering condition; wherein the first terminal and the relay terminal are in a multi-hop relay link, and the first triggering condition is related to the link status.

[0079] In this embodiment of the application, a multi-hop relay link in a wireless communication scenario may include two or more relay terminals. The relay in this embodiment of the application may be a terminal. The wireless communication scenario in this embodiment of the application may include a scenario supporting side-by-side communication. The first terminal may be a terminal in the multi-hop relay link. The multi-hop relay link may be a U2U relay link or a U2N relay link. In a U2U relay link, the first terminal may be a source terminal or a target terminal. In a U2N relay link, the first terminal may be a remote terminal. The first terminal may also be a relay terminal in a U2U or U2N relay link. The first triggering condition may include one or more conditions for triggering the first terminal to perform relay selection or reselection. The first triggering condition may be determined based on the link state associated with the first terminal.

[0080] In this embodiment, the first triggering condition may include a relay selection triggering condition and / or a relay reselection triggering condition. For example, the relay selection triggering condition may be used in a scenario where the first terminal currently has no serving relay link and selects a relay for the first time. The relay reselection triggering condition may be used in a scenario where the first terminal has already selected a relay, i.e., there is currently a serving relay link, but a relay reselection may be necessary.

[0081] In one implementation, the first terminal is a remote terminal, source terminal, target terminal, or relay terminal in the multi-hop relay link. The remote terminal, source terminal, and target terminal can also be referred to as end terminals.

[0082] In one implementation, the first triggering condition includes at least one of the following relay selection triggering conditions: This is triggered at the upper layer of the first terminal; The link quality of the direct link of the first terminal is lower than the configured threshold; The direct connection link of the first terminal experienced a wireless link failure; The link quality between the first terminal and one or more candidate relay terminals is higher than the configured threshold; The difference between the link quality between the first terminal and one or more candidate relay terminals and the link quality of the first terminal's direct link is higher than the configured threshold.

[0083] In this embodiment, the upper layer of the first terminal may include a V2X layer and / or a ProSe layer, etc. The V2X layer and / or ProSe layer of the first terminal may trigger the first terminal to perform an initial relay selection under certain circumstances.

[0084] In this embodiment, the direct link of the first terminal may include a direct link between the first terminal and other terminals, or a direct link between the first terminal and a network device. Various parameters can be used to characterize link quality, such as SL-RSRP, SD-RSRP, and Uu-RSRP. Each parameter may have a corresponding configuration threshold. The configuration threshold may be pre-configured or dynamically configured by the network device. For example, if SL-RSRP is lower than or equal to the RSRP threshold, it can be determined that the relay selection trigger condition is met.

[0085] In this embodiment, a wireless link failure in the direct connection link of the first terminal can include a failure of the wireless link between the first terminal and a directly connected terminal. The directly connected terminal of the first terminal can include a source terminal, a target terminal, or a remote terminal directly connected to the first terminal in a multi-hop relay link. For example, the first terminal is the source terminal, and the directly connected terminal is the target terminal. If the link between the source terminal and the target terminal fails, the source terminal can trigger relay selection. Similarly, the first terminal is the target terminal, and the directly connected terminal is the source terminal. If the link between the source terminal and the target terminal fails, the target terminal can trigger relay selection. Furthermore, the first terminal is a remote terminal, and the direct connection link of the first terminal includes the link between the remote terminal and the network device. If the link between the remote terminal and the network device fails, the remote terminal can trigger relay selection. Additionally, the source terminal, target terminal, or remote terminal can select one or more relay terminals. If the source terminal, target terminal, or remote terminal first selects a relay terminal, that relay terminal can continue to select other relay terminals as the first terminal until a multi-hop relay link is formed. If the source terminal, target terminal, or remote terminal selects multiple relay terminals, a multi-hop relay link can be formed based on the selected multiple relay terminals.

[0086] In this embodiment, a wireless link failure in the direct connection link of the first terminal may include a wireless link failure between the first terminal and the network device. If a wireless link failure occurs between the first terminal and the directly connected network device, the first terminal may trigger the selection of a relay terminal. The first terminal may be a remote terminal or a relay terminal already selected by other terminals. For example, a remote UE may first select UE1 as the relay UE between the remote UE and the network device, and UE1 may then select UE2 as the relay UE between UE1 and the network device. Alternatively, a remote UE may first select UE1, UE2, and UE3 as relay UEs between the remote UE and the network device.

[0087] In this embodiment, the configuration threshold for the link quality between the first terminal and one or more candidate relay terminals (e.g., referred to as the first configuration threshold) and the configuration threshold for the link quality of the first terminal's direct link (e.g., referred to as the second configuration threshold) can be the same or different. For example, the first configuration threshold for SL-RSRP of the first terminal's direct link is Thr1, and the first configuration threshold for SD-RSRP is Thr2. The second configuration threshold for SL-RSRP between the first terminal and the candidate relay terminals is Thr3, and the second configuration threshold for SD-RSRP is Thr4. Thr1 and Thr3 are the same, while Thr2 and Thr4 are different.

[0088] In this embodiment, the configuration threshold (which may be referred to as the third configuration threshold) for the difference between the link quality between the first terminal and one or more candidate relay terminals and the link quality of the direct link of the first terminal can be the same as or different from the first configuration threshold and / or the second configuration threshold mentioned above. For example, the third configuration threshold for the SL-RSRP difference is Thr5, and the second configuration threshold for SD-RSRP is Thr6. Thr5 is the same as Thr3, and Thr6 is different from Thr4.

[0089] In this embodiment, there may be one or more candidate relay terminals. Relay selection for any terminal can be triggered based on all candidate relay terminals. Alternatively, relay selection for a corresponding terminal can be triggered based on a subset of candidate relay terminals.

[0090] For example, there are three candidate relay terminals: UE1, UE2, and UE3. The first terminal is the source UE. If the SL-RSRP between the source UE and at least one of UE1, UE2, and UE3 is higher than the configured threshold, the source UE triggers relay selection, for example, selecting UE1 as the relay UE between the source UE and UE1. In this case, UE1 can become the first terminal, and it continues to determine whether the SL-RSRP between UE1 and UE2 and / or UE3 is higher than the configured threshold. If so, UE1 triggers selection of UE2 or UE3 as the relay UE between UE1 and the target UE.

[0091] For example, there are four candidate relay terminals. UE1 and UE2 are candidate relay terminals corresponding to the first terminal, and UE3 and UE4 are candidate relay terminals corresponding to the first-hop relay UE selected by the first terminal. If the first terminal is the target UE, and the SL-RSRP between the target UE and UE1 and / or UE2 is higher than the configured threshold, then the target UE triggers the selection of UE1 or UE2 as the relay UE between the source UE and UE1. If UE1 is selected as the relay UE between the source UE and UE1, UE1 can become the first terminal, and the SL-RSRP between it and UE3 and / or UE4 is further determined to be higher than the configured threshold. If so, UE1 triggers the selection of UE3 or UE4 as the relay UE between UE1 and the target UE.

[0092] In the embodiments of this application, after one or more first terminals initially select a relay terminal based on triggering conditions, a multi-hop relay link may be formed, thereby obtaining a longer communication distance than a single-hop relay network, improving communication reliability and communication range.

[0093] In one implementation, the link quality of the direct link of the first terminal is lower than a configured threshold, including at least one of the following: The PC5 link quality between the first terminal and the directly connected terminal is below the configuration threshold; The quality of the Uu link between the first terminal and the directly connected network device is below the configured threshold.

[0094] For example, the first terminal can be a source UE, and its directly connected terminal can be UE1. If the PC5 link quality between the source UE and UE1 is lower than the configured threshold, the source UE can trigger trunk selection. Similarly, the first terminal can be a target UE, and its directly connected terminal can be UE2. If the PC5 link quality between the target UE and UE2 is lower than the configured threshold, the target UE can trigger trunk selection. Again, the first terminal can be UE1, and its directly connected terminals can be both the source UE and UE2. If the PC5 link quality between the source UE and UE1 is lower than the configured threshold, UE1 can trigger trunk selection. Similarly, if the PC5 link quality between UE1 and UE2 is lower than the configured threshold, UE1 can also trigger trunk selection.

[0095] In one implementation, the configuration thresholds for the PC5 link and / or Uu link are configured via RRC, System Information Block (SIB) configuration, or pre-configuration.

[0096] In one implementation, the first triggering condition includes at least one of the following relay reselection triggering conditions: This is triggered at the upper layer of the first terminal; The link quality of one or more hops in the multi-hop relay link where the first terminal is located is lower than the configured threshold; One or more hops of the multi-hop relay link where the first terminal is located experience a radio link failure. One or more hops of the multi-hop relay link where the first terminal is located are released; In the multi-hop relay link where the first terminal is located, one or more relay terminals experience cell reselection, handover (HO), or radio resource control (RRC) connection establishment failure. The indication information of one or more relay terminals in the multi-hop relay link where the first terminal is located.

[0097] In this embodiment, if a multi-hop trunk link has been established, the configuration threshold for the link quality of one or more hops in the multi-hop trunk link can be the same as or different from the configuration threshold for the link quality initially selected for the trunk. The first terminal can determine whether to trigger trunk reselection based on one or more of the following: the link quality of one or more hops in the multi-hop trunk link, whether the link has failed, whether the link has been released, whether a mobility change has occurred (cell reselection, HO or RRC connection establishment), and trunk terminal indication. The first terminal may be a source terminal, a target terminal, a remote terminal, or a trunk terminal.

[0098] For example, in a multi-hop trunk link, the first hop is between the source UE and the trunk UE1, the second hop is between the trunk UE1 and the trunk UE2, and the third hop is between the trunk UE2 and the target UE.

[0099] If the first terminal is the source UE, and the link quality of hop1 is below the configured threshold or the link is released, the source UE can trigger a trunk reselection, potentially selecting UE3 as the new trunk UE between the source UE and UE2. In this case, hop1 becomes the connection between the source UE and UE3.

[0100] If the first terminal is relay UE1, and the link quality of hop2 is below the configured threshold or the link is released, relay UE1 can trigger relay reselection, possibly selecting UE4 as the new relay UE between UE1 and the target UE. In this case, hop2 becomes the connection between UE1 and UE4, and hop3 becomes the connection between UE4 and the target UE.

[0101] If the first terminal is relay UE1, and UE2 associated with hop2 and hop3 experiences one or more events such as cell reselection, HO or RRC connection establishment failure, UE1 can trigger relay reselection, for example, selecting relay UE5 as the new relay UE between UE1 and the target UE. In this case, the connection between UE1 and UE5 becomes hop2, and the connection between UE5 and the target UE becomes hop3.

[0102] For example, in a multi-hop trunk link, the first hop is between the network device and the trunk UE1, the second hop is between the trunk UE1 and the trunk UE2, and the third hop is between the trunk UE2 and the remote UE.

[0103] If the first terminal is relay UE1, and the link quality of hop1 is below the configured threshold or the link is released, relay UE1 can trigger relay reselection, possibly selecting UE6 as the relay UE between the network device and UE1. In this case, the connection between the network device and relay UE6 becomes hop1, and the connection between relay UE6 and relay UE1 becomes hop2.

[0104] If the first terminal is relay UE2, and the link quality between hop1 and hop2 is below the configured threshold or the link is released, relay UE2 can trigger relay reselection, potentially selecting UE7 as the relay UE between the network device and UE2. In this case, the connection between the network device and relay UE7 becomes hop1, and the connection between relay UE7 and relay UE2 becomes hop2.

[0105] If the first terminal is a remote UE, and UE2 associated with hop3 experiences one or more events such as cell reselection, HO or RRC connection establishment failure, the remote UE can trigger trunk reselection, for example, selecting trunk UE8 as the trunk UE between the remote UE and UE1. In this case, the connection between UE1 and trunk UE8 becomes hop2, and the connection between trunk UE8 and the remote UE becomes hop3.

[0106] In one implementation, the indication information of one or more relay terminals in a multi-hop relay link where the first terminal is located can be used to indicate at least one of the following: link failure, link release, link quality below a configured threshold, cell reselection, HO, or RRC connection establishment failure. If the first terminal receives this indication information, it can determine whether to perform relay reselection based on the specific content indicated by the information. For example, if the indication information indicates that the hop where the relay terminal is located has experienced link failure, link release, or link quality below a configured threshold, the first terminal can perform relay reselection. If the indication information indicates that the relay terminal has experienced cell reselection, HO, or RRC connection establishment failure, the first terminal can perform relay reselection.

[0107] In one implementation, the link quality of one or more hops in the multi-hop relay link where the first terminal is located is lower than a configured threshold, including at least one of the following: In the link between the first terminal and the second terminal, the quality of one or more hops of the PC5 link is lower than the configured threshold. In the link between the first terminal and the network device, the quality of one or more hops of the PC5 link is lower than the configured threshold. The quality of the Uu link from the first terminal to the network is lower than the configured threshold in the first or last hop of the link between the first terminal and the network device.

[0108] For example, if the first terminal is the source terminal, the second terminal can be the target terminal or a relay terminal. If the first terminal is the target terminal, the second terminal can be the source terminal or a relay terminal. If the first terminal is a remote terminal, the second terminal can be a relay terminal. If the first terminal is a relay terminal, the second terminal can be the source terminal, the target terminal, the remote terminal, or any other relay terminal besides the first terminal.

[0109] For example, the first or last hop of the link between the first terminal and the network device can be understood as a hop between the relay terminal and the network device. For example, hop 1 between UE1 and the network device in the example above.

[0110] In one implementation, the configuration thresholds for the PC5 link and / or Uu link are configured by at least one of the following: RRC configuration, SIB configuration, pre-configuration, relay configuration, network configuration of the relay's home network, source terminal configuration, and network configuration of the source terminal's home network. In this embodiment, the networks to which the terminals belong may be the same or different. The network to which the terminal belongs can send configuration information about the terminal to the terminal, or it can send configuration information about other terminals in the multi-hop relay link where the terminal resides to the terminal. For example, relay UE1 belongs to network 1, and relay UE2 belongs to network 2. Configuration thresholds for the PC5 link and / or Uu link of relay UE1 can be received from network 1, and configuration thresholds for the PC5 link and / or Uu link of relay UE2 can be received from network 2. As another example, the source UE belongs to network 3, and configuration thresholds for the PC5 links of one or more of the source UE, relay UE, and target UE can be received from network 3.

[0111] In one implementation, the thresholds for different hops in the multi-hop trunk link where the first terminal is located are configured to be the same or different. For example, the multi-hop trunk link where the first terminal is located includes hop1, hop2, and hop3. The SL-RSRP configuration threshold for hop1 is Thr1, the SL-RSRP configuration threshold for hop2 is Thr2, and the SL-RSRP configuration threshold for hop3 is Thr3.

[0112] The embodiments of this application can form a multi-hop relay link by triggering the selection of relays based on triggering conditions, which can further extend the communication distance and improve the communication reliability and range.

[0113] Figure 7 This is a schematic flowchart of a relay communication method 700 according to another embodiment of this application. The method may include one or more features of the above method, and in one embodiment, the method further includes: S710, the first terminal monitors the link status of its related links.

[0114] In one implementation, the relevant links of the first terminal include one or more hops of the direct link of the first terminal and / or one or more hops of the multi-hop trunk link in which the first terminal is located. For example, in the scenario of initial trunk selection, the relevant links of the first terminal may include the direct link of the first terminal. If the source terminal and the target terminal are initially connected by a direct link, the source terminal or the target terminal can monitor the link status of the link. As another example, in the scenario of reselecting a trunk, the relevant links of the first terminal may include one or more hops of the multi-hop trunk link in which the first terminal is located. If the multi-hop trunk link in which the first terminal is located includes hop1, hop2, and hop3, where hop2 and hop3 are associated with the first terminal. For example, if hop2 is the link between trunk UE1 and the first terminal, such as trunk UE2, and hop3 is the link from trunk UE2 to the target UE, then the first terminal, such as trunk UE2, is associated with hop2 and hop3. The first terminal can monitor the link status of hop2 and / or hop3.

[0115] In this embodiment, the link status of the relevant link of the first terminal can be monitored (also known as measured, detected, etc.) first, and then it can be determined whether the first triggering condition is met based on the link status. If the first triggering condition is met, the first terminal triggers the initial selection or reselection of the relay.

[0116] In one implementation, the link state of the link associated with the first terminal includes at least one of the following: The link quality of the relevant links of the first terminal; The availability of the relevant links of the first terminal; Changes in the mobility of relay terminals on the relevant links of the first terminal.

[0117] In one implementation, the link quality of the relevant link of the first terminal includes at least one of the following: Is the PC5 link quality of the relevant link of the first terminal lower than the configured threshold? Is the Uu link quality of the relevant link of the first terminal lower than the configured threshold?

[0118] For example, if the link quality of the PC5 link between the first terminal and the relay UE1 is lower than or equal to the configured threshold, it indicates poor link quality; if the link quality is higher than the configured threshold, it indicates good link quality.

[0119] For example, if the link quality of the Uu link between the first terminal and the network device is lower than or equal to the configured threshold, it indicates poor link quality; if the link quality is higher than the configured threshold, it indicates good link quality.

[0120] In one implementation, the link availability of the relevant link of the first terminal includes at least one of the following: Whether the relevant link of the first terminal has experienced a radio link failure (RLF); Has the relevant link of the first terminal been released? Whether the relevant link of the first terminal was successfully established.

[0121] For example, if the direct link of the first terminal experiences an RLF (Restricted Link Failure), then that direct link becomes unavailable. Similarly, if in a multi-hop trunk link where the first terminal resides, the first and second hops are released, then the link between the first and second hops becomes unavailable; if the third hop is not released, then the third hop becomes available. Furthermore, if in a multi-hop trunk link where the first terminal resides, the third hop fails to be established, then the third hop becomes unavailable; if the second hop is successfully established, then the second hop becomes available.

[0122] In one implementation, the mobility change of the relay terminal of the related link of the first terminal includes at least one of the following: Has the relay terminal experienced cell reselection? Does the relay terminal generate a HO (Hope)?

[0123] For example, if a cell reselection occurs at a relay terminal on a direct link of the first terminal, the first terminal can trigger the selection or reselection of the relay terminal. If a HO (House of Occurrence) occurs at a one-hop or multi-hop relay terminal on a multi-hop relay link where the first terminal is located, the first terminal can trigger the selection or reselection of the relay terminal.

[0124] In one implementation, the first terminal can send the link status it monitors to other terminals or network devices to assist them in relay selection or reselection. The second triggering condition for the first terminal to send the link status can be found in the relevant description in the following embodiment of the relay communication method executed by the second terminal, simply by replacing the second terminal with the first terminal.

[0125] Figure 8 This is a schematic flowchart of a relay communication method 800 according to another embodiment of this application. The method may include one or more features of the above method. In one embodiment, the method further includes: S810, the first terminal receives link status data sent by the second terminal.

[0126] In one implementation, the second terminal is a relay terminal, a source terminal, a target terminal, or a remote terminal.

[0127] In this embodiment of the application, the second terminal can monitor the link status of its related links.

[0128] In one implementation, the link state of the second terminal-related link includes at least one of the following: The link quality of the relevant links of the second terminal; The availability of the relevant links for this second terminal; Changes in the mobility of relay terminals on the relevant links of the second terminal.

[0129] In one implementation, the link quality of the relevant link of the second terminal includes at least one of the following: Is the PC5 link quality of the relevant link of the second terminal lower than the configured threshold? Is the Uu link quality of the relevant link of the second terminal lower than the configured threshold?

[0130] In one implementation, the link availability of the relevant link of the second terminal includes at least one of the following: Has a radio link failure (RLF) occurred on the relevant link of the second terminal? Has the relevant link of the second terminal been released? Whether the relevant link of the second terminal was successfully established.

[0131] In one implementation, the mobility change of the relay terminal of the related link of the second terminal includes at least one of the following: Has the relay terminal experienced cell reselection? Does the relay terminal generate a HO (Hope)?

[0132] In one implementation, the link state is carried by at least one of the following: PC5 non-access stratum signaling; discovery messages; Direct Communication Request (DCR) messages; Direct Communication Accept (DCA) messages; PC5 Radio Resource Control (PC5-RRC) signaling; and Media Access Control (MAC CE) signaling. For example, the PC5 non-access stratum may include a Proximity Based Services (ProSe) layer and / or a V2X layer, etc.

[0133] In one implementation, the PC5-RRC signaling includes at least one of the following: a measurement report, a notification message.

[0134] In one implementation, the link state includes at least one of the following: The connection status of the service hop, which is the hop where the second terminal is currently connecting to other terminals or network devices; The connection status of the candidate hop, which is a hop that the second terminal may connect to other terminals or network devices.

[0135] For example, a multi-hop trunk link includes a source UE, trunk UE1, trunk UE2, and a target UE. The first hop is between the source UE and trunk UE1, the second hop is between trunk UE1 and trunk UE2, and the third hop is between trunk UE2 and the target UE. The service hop of the source UE may include the first hop, the service hop of trunk UE1 may include the first hop and / or the second hop, the service hop of trunk UE2 may include the second hop and / or the third hop, and the service hop of the target UE may include the third hop.

[0136] For example, a multi-hop trunk link includes a remote UE, trunk UE1, trunk UE2, and a network device. The first hop is between the remote UE and trunk UE1, the second hop is between trunk UE1 and trunk UE2, and the third hop is between trunk UE2 and the network device. The service hop of the remote UE may include the first hop, the service hop of trunk UE1 may include the first hop and / or the second hop, and the service hop of trunk UE2 may include the second hop and / or the third hop.

[0137] In one implementation, the connection status includes at least one of the following: relay terminal identifier, measurement result, hop count, and serving cell information. For example, in the example above, the hop count of relay UE1 can be 1, and the hop count of relay UE2 can be 2.

[0138] In one implementation, the second terminal sending the link status is a relay terminal, and the first terminal receiving the link status includes at least one of the following: a source terminal and / or a target terminal with a normal link to the second terminal; a source terminal or target terminal closer to the second terminal; a source terminal and / or target terminal implemented based on the second terminal; or a source terminal that triggers the establishment of an inter-terminal connection. For example, the second terminal is the sender of the link status, and the sender is a relay terminal. The first terminal is the receiver of the link status, and the receiver can be a source terminal and / or a target terminal. For example, the receiver includes a source terminal and / or a target terminal with a normal link to the sender, a source terminal or target terminal closer to the sender, a source terminal and / or target terminal implemented based on the sender, or a source terminal that triggers the establishment of an inter-terminal connection.

[0139] In this embodiment of the application, in a U2U relay, after one or more relay terminals detect the status of their associated link, they can send the link status to the source terminal and / or the target terminal.

[0140] For example, a multi-hop trunk link includes a source UE, trunk UE1, trunk UE2, and a target UE. If the link between trunk UE2 and the target UE is faulty, such as being released or having poor link quality, and the link between the source UE and trunk UE1 is intact, trunk UE1 can send link status to the source UE. Here, trunk UE1 can be the sender of the link status, and the source UE can be the receiver of the link status.

[0141] For example, a multi-hop trunk link includes a source UE, trunk UE1, trunk UE2, and a target UE. Trunk UE1 can send link status to the end closer to it, i.e., the source UE. Trunk UE2 can send link status to the end closer to it, i.e., the target UE.

[0142] For example, the sending end can be determined based on the sending end's capabilities. For instance, relay UE2 selects to send link status to the source UE based on its own capabilities.

[0143] For example, in a multi-hop trunk link, if the end that triggers the connection establishment between terminals is the source UE, then trunk UE1 and trunk UE2 can send link status to the source UE.

[0144] In one implementation, the second terminal that sends the link status is a relay terminal, and the first terminal that receives the link status is a remote terminal.

[0145] In one implementation, when the second terminal sending the link status is a connected relay terminal, the receiving end of the link status can be a remote terminal and / or a network device.

[0146] For example, if the sending end of this link state is a connected relay terminal, the receiving end of this link state is a remote terminal and / or network device.

[0147] For example, if the sending end of the link is a non-connected relay terminal, the receiving end of the link is a remote terminal.

[0148] In this embodiment of the application, in a U2N relay, after one or more relay terminals monitor the link status of their associated links, they can send the link status to the network device and / or the remote terminal. For example, a multi-hop relay link includes a remote UE, relay UE1, relay UE2, and a network device. If a connection has been established between relay UE2 and the network device, relay UE2 can send the link status to the network device. If relay UE2 has not established a connection with the network device, it can send the link status to the remote terminal through relay UE1.

[0149] In one implementation, the first terminal selects a relay terminal based on at least one of the following: The PC5 link quality between the first terminal and the candidate relay terminal; Compliant with high-level guidelines; It meets the limit for the number of relay hops experienced; It meets the cache capacity requirements of relay terminals; This relay terminal is a multi-hop relay; The serving cell and / or public terrestrial mobile network (PLMN) of the relay terminal meet the requirements; The link quality of the next hop or multiple hops of this relay terminal is higher than the configured threshold, and the threshold configuration for each hop can be the same or different.

[0150] For example, if the first terminal is the source UE, and among the links between the source UE and UE1, UE2, and UE3, the PC5 link between the source UE and UE2 has the best link quality, then the source UE can choose UE2 as the relay UE.

[0151] For example, higher-level criteria include Relay Service Code (RSC) indication information, which allows a first terminal, such as the target UE, to select a relay UE based on the RSC in the indication information.

[0152] For example, if the current service relay hop count for the first terminal, such as the target UE, is 3, the target UE can only choose a relay link that can reach the target UE within 3 hops. This restriction can be configured by the network or related to QoS / service.

[0153] For example, if the cache capacity of UE3 is higher than the set value, the first terminal, such as relay UE2, can select UE3 as the relay UE.

[0154] For example, if UE1 supports multi-hop relay, but UE2 does not, the first terminal, such as the remote UE, can choose UE1 as the relay UE.

[0155] For example, the network can configure the requirements for the serving cell and / or PLMN to which a relay UE belongs. Assume that UEs belonging to serving cell 1, serving cell 2, and PLMN 1 can be used as relay UEs. If UE1 belongs to serving cell 1, UE2 belongs to serving cell 3, and UE3 belongs to PLMN 1, then the serving cell to which UE1 belongs and the PLMN to which UE3 belongs meet the requirements, and UE1 and UE3 can be selected as relay UEs; the serving cell to which UE2 belongs does not meet the requirements, and UE2 is not selected as a relay UE.

[0156] For example, if UE1's next hop is UE2, and its next hop after that is UE3, and the link quality between UE1 and UE2 is higher than configuration threshold 1, and the link quality between UE2 and UE3 is higher than configuration threshold 2, then the first terminal, such as the source terminal, can select UE1 as the relay UE.

[0157] Figure 9 This is a schematic flowchart of a relay communication method 900 according to an embodiment of this application. The method can optionally be applied to... Figures 1 to 5 The system shown is not limited to this. The method includes at least a portion of the following.

[0158] S910, The second terminal sends the link status; wherein the link status is related to the first triggering condition, the first triggering condition is used to trigger the first terminal to select a relay terminal that meets the requirements of the first terminal, and the first terminal, the second terminal and the relay terminal are in a multi-hop relay link.

[0159] In one implementation, step S910, where the second terminal sends the link status, includes: the second terminal periodically sending the link status. For example, after monitoring the link status or receiving the link status from another terminal, the second terminal can periodically send the link status to the first terminal.

[0160] In one implementation, step S910, in which the second terminal sends the link status, includes: the second terminal sending the link status based on a second triggering condition.

[0161] In one implementation, the second triggering condition includes at least one of the following events: The second terminal's measurement result of the reference signal is greater than or equal to the configured threshold; The difference between the current measurement result and the previous measurement result of the reference signal obtained by the second terminal exceeds the configured threshold; The second terminal experienced a radio link failure (RLF). The relevant links of the second terminal were released; The connection establishment of the relevant link of the second terminal failed; The mobility of the relay terminal in the relevant link of the second terminal has changed; The second terminal receives the measurement or monitoring results from the relay terminal; The second terminal receives a request from its previous hop terminal; The relevant links of the second terminal include the direct link of the second terminal and / or one or more hops of the multi-hop relay link where the second terminal is located.

[0162] In this embodiment of the application, the relevant links of the second terminal may include the direct link of the second terminal, or one or more hops of the multi-hop relay link where the second terminal is located.

[0163] In this embodiment of the application, according to the data transmission direction, the upstream terminal of the second terminal can send data to the second terminal. The second terminal can then send data to its next-hop terminal.

[0164] In one implementation, the link state is carried by at least one of the following: PC5 non-access stratum signaling; discovery message; DCR message; DCA message; PC5-RRC signaling; MAC CE signaling.

[0165] In one implementation, the PC5-RRC signaling includes at least one of the following: a measurement report, a notification message.

[0166] In one implementation, the link state includes at least one of the following: The connection status of the service hop, which is the hop where the second terminal is currently connecting to other terminals or network devices; The connection status of the candidate hop, which is a hop that the second terminal may connect to other terminals or network devices.

[0167] In one implementation, the connection status includes at least one of the following: relay terminal identifier, measurement result, hop count, and serving cell information.

[0168] In one implementation, the second terminal sending the link status is a relay terminal, and the first terminal receiving the link status includes at least one of the following: a source terminal and / or a target terminal with a normal link to the second terminal; a source terminal or target terminal closer to the second terminal; a source terminal and / or target terminal implemented based on the second terminal; or a source terminal that triggers the establishment of a connection between terminals.

[0169] In one implementation, the second terminal that sends the link status is a relay terminal, and the first terminal that receives the link status is a remote terminal.

[0170] In one implementation, when the second terminal sending the link state is a connected relay terminal, the receiving end of the link state also includes a network device.

[0171] For a specific example of the second terminal executing the relay communication method 900 in this embodiment, please refer to the relevant descriptions of the second terminal in the relay communication methods 600, 700, and 800 executed by the first terminal above. For the sake of brevity, they will not be repeated here.

[0172] The relay communication method in this application embodiment may include a relay selection and / or reselection mechanism in side-link multi-hop relay technology. For example, based on the relay selection and reselection in single-hop U2U / U2N relay technology, a multi-hop relay selection and reselection mechanism may be further provided, such as including at least one of the following schemes: multi-hop relay selection and reselection triggering conditions; multi-hop relay selection and reselection process; and determination of relays that meet the conditions. Several specific examples are given below.

[0173] Example 1: Multi-hop relay selection / reselection trigger conditions.

[0174] I. Relay selection triggering conditions may include at least one of the following: (1) Triggered by the upper layer (e.g., V2X / Prose layer); (2) The link quality is below a certain threshold, for example: For example, in U2U relay: the PC5 link quality (SL-RSRP / SD-RSRP) with the other UE is below the configured threshold of 1; For example, in U2N relays: the quality of the Uu link in the network is lower than the configured threshold of 2; The above configuration thresholds can be derived from one or more of the following: RRC configuration, SIB configuration, or pre-configuration.

[0175] (3) A wireless link failure occurred between the other party's UE / network.

[0176] II. Relay reselection triggering conditions may include at least one of the following: (1) Triggered by the upper layer (V2X / Prose layer); (2) The link quality of any hop in the current link is below the threshold, including at least one of the following examples: For example, in U2U MH (multi-hop) relay: the quality of any PC5 link (SL-RSRP / SD-RSRP) is lower than the configured threshold of 1; For example, in U2N MH relay: the quality of any PC5 link (SL-RSRP / SD-RSRP) is lower than the configured threshold 2, or the quality of the last hop relay to network Uu is lower than the configured threshold 3.

[0177] The above configuration thresholds are derived from RRC configuration / SIB configuration / pre-configuration / relay configuration (or relay network) / source UE configuration (or source network). Threshold configurations for different hops can be the same or different.

[0178] (3) A wireless link failure occurs at any hop (PC5 / Uu); (4) Any hop link is released; (5) Cell reselection, handover (HO), RRC connection establishment failure, etc. occur in any hop of the U2N MH relay UE; (6) Any relay UE in any hop sends an indication message. This indication message may indicate that the hop link where the relay UE is located has experienced a link failure, link release, poor link quality, cell reselection, HO, RRC connection establishment failure, etc.

[0179] Example 2: Multi-hop trunk selection / reselection process - centralized trunk selection and reselection.

[0180] Figure 10 The schematic flowchart of centralized relay selection / reselection according to Example 2 of this application is as follows: 1. Each UE monitors / measures its own egress-hop status (i.e., an example of link state), which includes at least one of the following: Link quality of PC5 / Uu links with one or more hops (e.g., hops can be labeled as egress-hops), such as SL-RSRP, SD-RSRP, or Uu-RSRP; Availability of PC5 / Uu links (one-hop or multi-hop): whether a radio link failure (RLF) has occurred, whether it has been released, and whether it has been successfully established; For U2N trunks, does the trunk UE experience mobility changes such as HO / cell reselection?

[0181] For example, one or more hops may include hops that are far from the source UE, such as hops that are far from the source UE / target UE (end UE).

[0182] 2. Each relay UE can send its own one-hop or multi-hop monitoring information to the remote / source UE: 2-1. The method of transmission may include at least one of the following: (1) The U2U relay is sent to both UEs, or only to one of the UEs. One of the UEs is the one with an intact link / the one that is closer / the one that is based on the UE / the one that triggered the establishment of the U2U connection.

[0183] (2) U2N relays are sent to the UE and the network, or only to the UE. For example, connected relays are sent to the network and / or the remote UE. Another example is disconnected relays sent to the remote UE.

[0184] 2-2. This sending can be triggered by conditions or periodically, as shown in the following example: (1) The period of periodic triggering can be configured by the upper layer (V2X / Prose layer) or the access layer (base station or source UE); (2) The event that triggers the event can be at least one of the following: The RSRP is measured to be greater than and / or less than a certain threshold, which is configured by the relay UE (or relay UE network) / remote UE (remote UE network) / the network currently accessed by the U2N; The measured RSRP differs from the previous measurement result by (better or worse) by more than a certain threshold (or within a certain time period). This threshold and time period are configured by the relay UE (or relay UE network) / remote UE (remote UE network) / the network currently accessed by the U2N. An RLF (Relational Link Failure) occurs, the link is released, and connection establishment fails. Mobility changes such as HO / cell reselection occur; Received (forwarded) measurement / monitoring results from other relays; Received a request from the source UE (which may be referred to as the source UE, source terminal, etc.).

[0185] 2-3. This information (i.e., one-hop or multi-hop cases) can be carried by at least one of the following methods: PC5 access layer signaling: discovery messages (Model-A / B), DCR messages, DCA messages, or others; PC5-RRC signaling: measurement report, notification message, or other signaling; MAC CE signaling.

[0186] 2-4. This information (i.e., one-hop or multi-hop cases) may include at least one of the following: For example, the current (if any) connection status of the serving hop, such as: Relay UE ID (L2ID), measurement results, hop level, and serving cell information.

[0187] For example, optional candidate hops include: Relay UE ID (L2 ID), measurement results, hop level, and serving cell information.

[0188] The serving hops can include established hops connected to the terminal in a multi-hop trunk link. For example, the serving hops of trunk 1 include hop 2, and the serving hops of trunk 2 include hop 3. The candidate hops of the terminal can include hops with which the terminal may establish a connection. For example, if the candidate hops of trunk 1 and candidate trunk 3 include hop 4, and the candidate hops of candidate trunk 3 and the target UE include hop 5, then hop 4 and hop 5 are hops with which a connection has not yet been established.

[0189] 3. The source / remote UE performs relay selection or reselection, choosing a relay UE that meets the requirements of the upper layer and AS layer. Examples of selection methods are as follows: relay selection or reselection can be performed based on the current hop's detected status; and / or, relay selection or reselection can be performed based on the information content received from other hops.

[0190] Example 3: Multi-hop relay selection / reselection process - Distributed relay selection and reselection Figure 11 The schematic flowchart for distributed relay selection / reselection, based on Example 3 of this application, shows the following steps: 1. Each UE monitors / measures its own egress-hop status, which includes at least one of the following: Link quality of PC5 / Uu links in Egress-hop (SL-RSRP / SD-RSRP / Uu-RSRP). Availability of the PC5 / Uu link in Egress-hop: whether an RLF occurred, whether it was released, and whether it was successfully established; For U2N trunks, does the trunk UE experience mobility changes such as HO / cell reselection?

[0191] 2. Each hop UE will send its own egress-hop status (if any) to the previous hop UE for monitoring / measuring: 2-1. This sending can be triggered by conditions or periodically, as shown in the following example: (1) The period of periodic triggering can be configured by the upper layer (V2X / Prose layer) or the AS layer (base station or source UE); (2) The event that triggers the event can be at least one of the following: The RSRP is measured to be greater than and / or less than a certain threshold, which is configured by the relay UE (or relay UE network) / remote UE (remote UE network) / the network currently accessed by the U2N; The measured RSRP differs from the previous measurement result by (better or worse) by more than a certain threshold (or within a certain time period). This threshold and time period are configured by the relay UE (or relay UE network) / remote UE (remote UE network) / the network currently accessed by the U2N. An RLF (Relational Link Failure) occurs, the link is released, and connection establishment fails. Mobility changes such as HO / cell reselection occur; Received (forwarded) measurement / monitoring results from other relays; Received a request from the previous UE.

[0192] 2-3. This information can be carried in at least one of the following ways: PC5-S signaling: Discovery message (Model-A / B), DCR message, DCA message, or others; PC5-RRC signaling: Measurement reports, notification messages, or other signaling; MAC CE signaling.

[0193] 2-4. This information may include at least one of the following: For example, the current (if any) connection status of the serving hop, such as: Relay UE ID (L2 ID), measurement results, hop level, serving cell information.

[0194] For example, optional candidate hop information includes: Relay UE ID (L2 ID), measurement results, hop level, and serving cell information.

[0195] 3. Each UE performs a relay selection reselection, choosing a relay UE that meets the requirements of the upper layer and AS layer: It can be based on the situation of this hop as detected by itself; and / or, based on the information content after receiving the information of the next hop.

[0196] Example 4: Selection criteria for multi-hop relays.

[0197] For example, relay selection may include at least one of the following criteria: The PC5 link quality with this relay, including SL-RSRP and / or SD-RSRP values, is higher than a certain threshold (higher than a certain threshold for the current serving relay). It complies with high-level guidelines, such as RSC indication information; It meets the limit for the number of relay hops experienced (less than the current service relay hop count); Meets the relay's buffer capacity requirements; This relay is a multi-hop relay; The serving cell and / or PLMN of the relay meets the requirements; The quality of the next hop or multiple hop links of this relay is higher than a certain threshold, and the threshold configuration for each hop can be the same or different.

[0198] The above example provides a selection and reselection process for multi-hop U2U / U2N relays, which can extend the communication distance and improve communication reliability and range.

[0199] Figure 12 This is a schematic block diagram of a first terminal 1200 according to an embodiment of this application. The first terminal 1200 may include: Processing unit 1201 is used to select a relay terminal that meets the requirements of the first terminal based on a first triggering condition; wherein the first terminal and the relay terminal are in a multi-hop relay link, and the first triggering condition is related to the link status.

[0200] In one implementation, the first triggering condition includes at least one of the following relay selection triggering conditions: This is triggered at the upper layer of the first terminal; The link quality of the direct link of the first terminal is lower than the configured threshold; The direct connection link of the first terminal experienced a wireless link failure; The link quality between the first terminal and one or more candidate relay terminals is higher than the configured threshold; The difference between the link quality between the first terminal and one or more candidate relay terminals and the link quality of the first terminal's direct link is higher than the configured threshold.

[0201] In one implementation, the link quality of the direct link of the first terminal is lower than a configured threshold, including at least one of the following: The PC5 link quality between the first terminal and the directly connected terminal is below the configuration threshold; The quality of the Uu link between the first terminal and the directly connected network device is below the configured threshold.

[0202] In one implementation, the configuration thresholds for the PC5 link and / or Uu link are configured via RRC, System Information Block (SIB) configuration, or pre-configuration.

[0203] In one implementation, the first triggering condition includes at least one of the following relay reselection triggering conditions: This is triggered at the upper layer of the first terminal; The link quality of one or more hops in the multi-hop relay link where the first terminal is located is lower than the configured threshold; One or more hops of the multi-hop relay link where the first terminal is located experience a radio link failure. One or more hops of the multi-hop relay link where the first terminal is located are released; In the multi-hop relay link where the first terminal is located, one or more relay terminals experience cell reselection, handover HO, or Radio Resource Control (RRC) connection establishment failure. The indication information of one or more relay terminals in the multi-hop relay link where the first terminal is located.

[0204] In one implementation, the link quality of one or more hops in the multi-hop relay link where the first terminal is located is lower than a configured threshold, including at least one of the following: The quality of one or more hops of the PC5 link between the first terminal and the second terminal is lower than the configured threshold. The quality of one or more hops of the PC5 link between the first terminal and the network device is below the configured threshold. The quality of the Uu link from the first terminal to the network in the first or last hop of the link between the first terminal and the network device is lower than the configured threshold.

[0205] For example, if the first terminal is the source terminal, the second terminal can be the target terminal or a relay terminal. If the first terminal is the target terminal, the second terminal can be the source terminal or a relay terminal. If the first terminal is a remote terminal, the second terminal can be a relay terminal. If the first terminal is a relay terminal, the second terminal can be the source terminal, the target terminal, the remote terminal, or any other relay terminal besides the first terminal.

[0206] In one implementation, the configuration threshold of the PC5 link and / or Uu link is configured by at least one of the following: RRC configuration, SIB configuration, pre-configuration, trunk configuration, network configuration of trunk home, source terminal configuration, and network configuration of source terminal home.

[0207] In one implementation, the thresholds for different hops in the multi-hop relay link where the first terminal is located are configured to be the same or different.

[0208] In one implementation, the indication information is used to indicate at least one of the following: the hop where the relay terminal is located has experienced a link failure, a link release, a link quality lower than a configured threshold, a cell reselection, a HO, or an RRC connection establishment failure.

[0209] In one implementation, the first terminal is a remote terminal, source terminal, target terminal, or relay terminal in the multi-hop relay link.

[0210] In one implementation, the processing unit is also used to monitor the link status of its associated links; The relevant links of the first terminal include the direct link of the first terminal and / or one or more hops of the multi-hop relay link where the first terminal is located.

[0211] In one implementation, the link state of the link associated with the first terminal includes at least one of the following: The link quality of the relevant links of the first terminal; The availability of the relevant links of the first terminal; Changes in the mobility of relay terminals on the relevant links of the first terminal.

[0212] In one implementation, the link quality of the relevant link of the first terminal includes at least one of the following: Is the PC5 link quality of the relevant link of the first terminal lower than the configured threshold? Is the Uu link quality of the relevant link of the first terminal lower than the configured threshold?

[0213] In one implementation, the link availability of the relevant link of the first terminal includes at least one of the following: Did the relevant link of the first terminal experience a radio link failure (RLF)? Has the relevant link of the first terminal been released? Whether the relevant link of the first terminal was successfully established.

[0214] In one implementation, the mobility change of the relay terminal of the related link of the first terminal includes at least one of the following: Has the relay terminal experienced cell reselection? Does the relay terminal generate a HO (Hope)?

[0215] In one implementation, such as Figure 13 As shown, the first terminal 1300 also includes: The receiving unit 1301 is used to receive the link status sent by the second terminal, which is a relay terminal, source terminal, target terminal or remote terminal.

[0216] In one implementation, the link state is carried by at least one of the following: PC5 non-access stratum signaling; discovery message; direct communication request (DCR) message; direct communication acceptance (DCA) message; PC5 radio resource control layer (PC5-RRC) signaling; and MAC CE signaling.

[0217] In one implementation, the PC5-RRC signaling includes at least one of the following: a measurement report, a notification message.

[0218] In one implementation, the link state includes at least one of the following: The connection status of the service hop, which is the hop where the second terminal is currently connecting to other terminals or network devices; The connection status of the candidate hop, which is a hop that the second terminal may connect to other terminals or network devices.

[0219] In one implementation, the connection status includes at least one of the following: relay terminal identifier, measurement result, hop count, and serving cell information.

[0220] In one implementation, the second terminal sending the link status is a relay terminal, and the first terminal receiving the link status includes at least one of the following: a source terminal and / or a target terminal with a normal link to the second terminal; a source terminal or target terminal closer to the second terminal; a source terminal and / or target terminal implemented based on the second terminal; or a source terminal that triggers the establishment of a connection between terminals.

[0221] In one implementation, the second terminal that sends the link status is a relay terminal, and the first terminal that receives the link status is a remote terminal.

[0222] In one implementation, when the second terminal sending the link state is a connected relay terminal, the receiving end of the link state also includes a network device.

[0223] In one implementation, the first terminal selects a relay terminal based on at least one of the following: The PC5 link quality between the first terminal and the candidate relay terminal; Compliant with high-level guidelines; It meets the limit for the number of relay hops experienced; It meets the cache capacity requirements of relay terminals; This relay terminal is a multi-hop relay; The serving cell and / or public terrestrial mobile network (PLMN) of the relay terminal meet the requirements; The link quality of the next hop or multiple hops of this relay terminal is higher than the configured threshold, and the threshold configuration for each hop can be the same or different.

[0224] The first terminals 1200 and 1300 in this application embodiment can realize the corresponding functions of the first terminals in the aforementioned method embodiments. The processes, functions, implementation methods, and beneficial effects of each module (sub-module, unit, or component, etc.) in the first terminals 1200 and 1300 can be found in the corresponding descriptions in the above method embodiments, and will not be repeated here. It should be noted that the functions described for each module (sub-module, unit, or component, etc.) in the first terminals 1200 and 1300 in the application embodiments can be implemented by different modules (sub-modules, units, or components, etc.) or by the same module (sub-module, unit, or component, etc.).

[0225] Figure 14 This is a schematic block diagram of a second terminal 1400 according to an embodiment of this application. The second terminal 1400 may include: The transmitting unit 1401 is used to transmit link status; wherein the link status is related to a first triggering condition, the first triggering condition is used to trigger a first terminal to select a relay terminal that meets the requirements of the first terminal, and the first terminal, the second terminal and the relay terminal are in a multi-hop relay link.

[0226] In one implementation, the transmitting unit is used to periodically transmit the link status.

[0227] In one implementation, the sending unit is used to send the link status based on a second triggering condition.

[0228] In one implementation, the second triggering condition includes at least one of the following events: The second terminal's measurement result of the reference signal is greater than or equal to the configured threshold; The difference between the current measurement result and the previous measurement result of the reference signal obtained by the second terminal exceeds the configured threshold; The second terminal experienced a radio link failure (RLF). The relevant links of the second terminal were released; The connection establishment of the relevant link of the second terminal failed; The mobility of the relay terminal in the relevant link of the second terminal has changed; The second terminal receives the measurement or monitoring results from the relay terminal; The second terminal receives a request from its previous hop terminal; The relevant links of the second terminal include the direct link of the second terminal and / or one or more hops of the multi-hop relay link where the second terminal is located.

[0229] In one implementation, the link state is carried by at least one of the following: PC5 non-access stratum signaling; discovery message; DCR message; DCA message; PC5-RRC signaling; MAC CE signaling.

[0230] In one implementation, the PC5-RRC signaling includes at least one of the following: a measurement report, a notification message.

[0231] In one implementation, the link state includes at least one of the following: The connection status of the service hop, which is the hop where the second terminal is currently connecting to other terminals or network devices; The connection status of the candidate hop, which is a hop that the second terminal may connect to other terminals or network devices.

[0232] In one implementation, the connection status includes at least one of the following: relay terminal identifier, measurement result, hop count, and serving cell information.

[0233] In one implementation, the second terminal sending the link status is a relay terminal, and the first terminal receiving the link status includes at least one of the following: a source terminal and / or a target terminal with a normal link to the second terminal; a source terminal or target terminal closer to the second terminal; a source terminal and / or target terminal implemented based on the second terminal; or a source terminal that triggers the establishment of a connection between terminals.

[0234] In one implementation, the second terminal that sends the link status is a relay terminal, and the first terminal that receives the link status is a remote terminal.

[0235] In one implementation, when the second terminal sending the link state is a connected relay terminal, the receiving end of the link state also includes a network device.

[0236] The second terminal 1400 in this embodiment can implement the corresponding functions of the second terminal in the aforementioned method embodiments. The processes, functions, implementation methods, and beneficial effects of each module (sub-module, unit, or component, etc.) in the second terminal 1400 can be found in the corresponding descriptions in the above method embodiments, and will not be repeated here. It should be noted that the functions described for each module (sub-module, unit, or component, etc.) in the second terminal 1400 of this embodiment can be implemented by different modules (sub-modules, units, or components, etc.) or by the same module (sub-module, unit, or component, etc.).

[0237] Figure 15 This is a schematic structural diagram of a communication device 1500 according to an embodiment of this application. The communication device 1500 includes a processor 1510, which can call and run computer programs from memory to enable the communication device 1500 to implement the methods in the embodiments of this application.

[0238] In one embodiment, the communication device 1500 may further include a memory 1520. The processor 1510 can retrieve and run computer programs from the memory 1520 to enable the communication device 1500 to implement the methods described in the embodiments of this application.

[0239] The memory 1520 can be a separate device independent of the processor 1510, or it can be integrated into the processor 1510.

[0240] In one embodiment, the communication device 1500 may further include a transceiver 1530, and the processor 1510 may control the transceiver 1530 to communicate with other devices. Specifically, it may send information or data to other devices or receive information or data sent by other devices.

[0241] The transceiver 1530 may include a transmitter and a receiver. The transceiver 1530 may further include an antenna, and the number of antennas may be one or more.

[0242] In one embodiment, the communication device 1500 may be the first terminal of the present application embodiment, and the communication device 1500 may implement the corresponding processes implemented by the first terminal in the various methods of the present application embodiment. For the sake of brevity, it will not be described in detail here.

[0243] In one embodiment, the communication device 1500 may be the second terminal of the present application embodiment, and the communication device 1500 may implement the corresponding processes implemented by the second terminal in the various methods of the present application embodiment. For the sake of brevity, it will not be described in detail here.

[0244] Figure 16 This is a schematic structural diagram of a chip 1600 according to an embodiment of this application. The chip 1600 includes a processor 1610, which can call and run computer programs from memory to implement the methods in the embodiments of this application.

[0245] In one embodiment, chip 1600 may further include memory 1620. Processor 1610 can retrieve and run computer programs from memory 1620 to implement the methods executed by the first terminal or the second terminal in this embodiment.

[0246] The memory 1620 can be a separate device independent of the processor 1610, or it can be integrated into the processor 1610.

[0247] In one embodiment, the chip 1600 may further include an input interface 1630. The processor 1610 can control the input interface 1630 to communicate with other devices or chips; specifically, it can acquire information or data sent by other devices or chips.

[0248] In one embodiment, the chip 1600 may further include an output interface 1640. The processor 1610 can control the output interface 1640 to communicate with other devices or chips; specifically, it can output information or data to other devices or chips.

[0249] In one implementation, the chip can be applied to the first terminal in the embodiments of this application, and the chip can implement the corresponding processes implemented by the first terminal in the various methods of the embodiments of this application. For the sake of brevity, it will not be described in detail here.

[0250] In one implementation, the chip can be applied to the second terminal in the embodiments of this application, and the chip can implement the corresponding processes implemented by the second terminal in the various methods of the embodiments of this application. For the sake of brevity, it will not be described in detail here.

[0251] The chips used in the first terminal and the second terminal can be the same chip or different chips.

[0252] It should be understood that the chip mentioned in the embodiments of this application may also be referred to as a system-on-a-chip, system chip, chip system, or system-on-a-chip, etc.

[0253] The processors mentioned above can be general-purpose processors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), or other programmable logic devices, transistor logic devices, discrete hardware components, etc. Among them, the general-purpose processors mentioned above can be microprocessors or any conventional processor.

[0254] The aforementioned memory can be volatile memory or non-volatile memory, or a combination of both. Non-volatile memory can be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. Volatile memory can be random access memory (RAM).

[0255] It should be understood that the above-described memory is exemplary and not a limiting description. For example, the memory in the embodiments of this application may also be static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM), and direct memory bus RAM (DR RAM), etc. That is to say, the memory in the embodiments of this application is intended to include, but is not limited to, these and any other suitable types of memory.

[0256] Figure 17 This is a schematic block diagram of a communication system 1700 according to an embodiment of this application. The communication system 1700 includes a first terminal 1710 and a second terminal 1720.

[0257] The first terminal 1710 is used to select a relay terminal that meets the requirements of the first terminal based on a first triggering condition; wherein the first terminal and the relay terminal are in a multi-hop relay link, and the first triggering condition is related to the link status.

[0258] The second terminal 1720 is used to send link status. The first triggering condition is used to trigger the first terminal to select a relay terminal that meets the requirements of the first terminal. The first terminal, the second terminal and the relay terminal are in a multi-hop relay link.

[0259] The first terminal 1710 can be used to implement the corresponding functions implemented by the first terminal in the above method, and the second terminal 1720 can be used to implement the corresponding functions implemented by the second terminal in the above method. For the sake of brevity, further details are omitted here.

[0260] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. This computer program product includes one or more computer instructions. When these computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates one or more available media. The available media can be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., DVDs), or semiconductor media (e.g., solid-state drives (SSDs)).

[0261] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply 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 this application.

[0262] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0263] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A relay communication method, comprising: The first terminal selects a relay terminal that meets its requirements based on a first triggering condition; wherein the first terminal and the relay terminal are in a multi-hop relay link, and the first triggering condition is related to the link status.

2. The method according to claim 1, wherein, The first triggering condition includes at least one of the following relay selection triggering conditions: The upper layer of the first terminal is triggered; The link quality of the direct connection link of the first terminal is lower than the configured threshold; A wireless link failure occurred between the first terminal and the direct link; The link quality between the first terminal and one or more candidate relay terminals is higher than the configured threshold; The difference between the link quality between the first terminal and one or more candidate relay terminals and the link quality of the direct link of the first terminal is higher than the configured threshold.

3. The method according to claim 2, wherein, The link quality of the direct connection link of the first terminal is lower than the configured threshold, including at least one of the following: The quality of the PC5 link between the first terminal and the directly connected terminal is lower than the configured threshold; The quality of the Uu link between the first terminal and the directly connected network device is lower than the configured threshold. The configuration thresholds for the PC5 link and / or Uu link are configured through Radio Resource Control (RRC), System Information Block (SIB), or pre-configured.

4. The method according to any one of claims 1 to 3, wherein, The first triggering condition includes at least one of the following relay reselection triggering conditions: The upper layer of the first terminal is triggered; The link quality of one or more hops in the multi-hop relay link where the first terminal is located is lower than the configured threshold; One or more hops of the multi-hop relay link where the first terminal is located experience a radio link failure. One or more hops of the multi-hop relay link where the first terminal is located are released; The first terminal is located in a multi-hop relay link where one or more hops of the relay terminal experience cell reselection, handover HO, or RRC connection establishment failure. Upon receiving indication information from one or more relay terminals in the multi-hop relay link where the first terminal is located, In this configuration, the thresholds for different hops in the multi-hop relay link where the first terminal is located are configured to be the same. The indication information is used to indicate at least one of the following: the hop where the relay terminal is located has experienced a link failure, a link release, a link quality lower than the configured threshold, a cell reselection, a HO, or an RRC connection establishment failure.

5. The method according to claim 4, wherein, The link quality of one or more hops in the multi-hop relay link where the first terminal is located is lower than the configured threshold, including at least one of the following: The quality of one or more hops of the PC5 link between the first terminal and the second terminal is lower than the configured threshold. The quality of one or more PC5 links in the link between the first terminal and the network device is lower than the configured threshold. If the quality of the Uu link from the first terminal to the network in the first or last hop of the link between the first terminal and the network device is lower than the configured threshold, the Uu link quality is lower than the configured threshold. The configuration thresholds for the PC5 link and / or Uu link are configured by at least one of the following: RRC configuration, SIB configuration, pre-configuration, trunk configuration, network configuration of trunk home, source terminal configuration, and network configuration of source terminal home.

6. The method according to any one of claims 1 to 5, wherein, The first terminal is a remote terminal, source terminal, target terminal, or relay terminal in the multi-hop relay link; and / or The method further includes: the first terminal monitoring the link status of its related links; The relevant links of the first terminal include the direct link of the first terminal and / or one or more hops of the multi-hop relay link where the first terminal is located. The link status of the first terminal-related link includes at least one of the following: The link quality of the relevant links of the first terminal; The availability of the relevant links of the first terminal; Changes in the mobility of relay terminals in the relevant links of the first terminal.

7. The method according to claim 6, wherein, The link availability of the relevant link of the first terminal includes at least one of the following: whether a radio link failure (RLF) has occurred on the relevant link of the first terminal; whether the relevant link of the first terminal has been released; whether the relevant link of the first terminal has been successfully established; and / or The mobility change of the relay terminal in the relevant link of the first terminal includes at least one of the following: whether the relay terminal has undergone cell reselection; whether the relay terminal has undergone HO.

8. The method according to any one of claims 1 to 7, wherein, The method further includes: The first terminal receives the link status sent by the second terminal, where the second terminal is a relay terminal, source terminal, target terminal, or remote terminal. The link state is carried by at least one of the following methods: PC5 non-access stratum signaling; discovery message; direct communication request (DCR) message; direct communication accept (DCA) message; PC5 radio resource control (PC5-RRC) signaling; and Media Access Control (MAC) control element (CE) signaling. The PC5-RRC signaling includes at least one of the following: measurement report, notification message.

9. The method according to any one of claims 1 to 8, wherein, The first terminal selects a relay terminal based on at least one of the following: The PC5 link quality between the first terminal and the candidate relay terminal; Compliant with high-level guidelines; It meets the limit for the number of relay hops experienced; It meets the cache capacity requirements of relay terminals; The relay terminal is a multi-hop relay; The serving cell and / or public terrestrial mobile network (PLMN) of the relay terminal meet the requirements; The link quality of the next hop or multiple hops of the relay terminal is higher than the configured threshold, and the threshold configuration for each hop can be the same or different.

10. A relay communication method, comprising: The second terminal sends the link status; The link status is related to a first triggering condition, which is used to trigger the first terminal to select a relay terminal that meets the requirements of the first terminal. The first terminal, the second terminal, and the relay terminal are in a multi-hop relay link.

11. The method according to claim 10, wherein, The second terminal sends link status, including: The second terminal periodically sends the link status; and / or The second terminal sends the link status based on the second triggering condition. The second triggering condition includes at least one of the following events: The measurement result of the second terminal on the reference signal is greater than or equal to the configured threshold; The difference between the current measurement result and the previous measurement result of the reference signal obtained by the second terminal exceeds the configured threshold; The second terminal experienced a radio link failure (RLF). The relevant links of the second terminal are released; The connection establishment of the relevant link of the second terminal failed; The relay terminal of the relevant link of the second terminal experiences a change in mobility; The second terminal receives the measurement or monitoring results from the relay terminal; The second terminal receives a request from its preceding terminal; The relevant links of the second terminal include the direct link of the second terminal and / or one or more hops of the multi-hop relay link where the second terminal is located.

12. The method according to claim 10 or 11, wherein, The link state is carried by at least one of the following methods: PC5 non-access stratum signaling; discovery message; DCR message; DCA message; PC5-RRC signaling; MAC CE signaling. The PC5-RRC signaling includes at least one of the following: measurement report, notification message.

13. The method according to any one of claims 10 to 12, wherein, The link status includes at least one of the following information: The connection status of service hops, wherein the service hop is the hop where the second terminal is currently connecting to other terminals or network devices; The connection status of candidate hops, where the candidate hops are those from which the second terminal may connect to other terminals or network devices. The connection status includes at least one of the following: relay terminal identifier, measurement result, hop count, and serving cell information.

14. The method according to any one of claims 10 to 13, wherein, When the second terminal is a connected relay terminal, the receiving end of the link state also includes a network device.

15. A terminal device, comprising: A processor and a memory for storing a computer program, the processor for calling and running the computer program stored in the memory to cause the terminal device to perform the method as claimed in any one of claims 1 to 9 or any one of claims 10 to 14.

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