Communication method and communication device

Abstract

An embodiment of the present application discloses a communication method and a communication device, which is applied to a first terminal device, and includes: receiving second information from a second terminal device; the second information indicates a second condition for the second terminal device to act as a relay device for the first terminal device; sending a first message to the second terminal device based on the second information and the first information; the first message is used to establish a communication connection with the second terminal device, and the first information indicates the first condition for the first terminal device to select or reselect the second terminal device as a relay device; it can avoid selecting an inappropriate relay UE, resulting in additional communication connection establishment overhead, thereby improving communication quality.

Description

Technical Field

[0001] The present application relates to the field of communications, and in particular to a communication method and a communication device. Background Art

[0002] UE to NW (U2N) relay refers to a communication technology that allows a remote user equipment (UE) to access the network through another relay UE. This technology can be used to improve network coverage. For example, if the remote UE is located in a location with poor signal coverage or is outside the network coverage area, the remote UE can access the network through the relay UE, thereby improving network coverage.

[0003] In a UE-to-NW relay scenario, the remote UE and relay UE communicate via the sidelink (SL). SL communication supports unicast, multicast, and broadcast modes. The following discussion focuses on unicast communication between the relay UE and the remote UE. In a UE-to-NW relay scenario, the remote UE experiences high latency and high signaling overhead when selecting or reselecting a relay UE. Summary of the Invention

[0004] The embodiments of the present application disclose a communication method and a communication device, which can improve the communication quality of a remote UE by selecting or reselecting a suitable relay UE.

[0005] In a first aspect, an embodiment of the present application provides a communication method, which is applied to a first terminal device, and the method includes: receiving second information from a second terminal device; the second information indicates a second condition for the second terminal device to act as a relay device for the first terminal device; based on the second information and the first information, sending a first message to the second terminal device; the first message is used to establish a communication connection with the second terminal device, and the first information indicates the first condition for the first terminal device to select or reselect the second terminal device as a relay device.

[0006] In an embodiment of the present application, the first terminal device may send the first message to the second terminal device based on the second information and the first information: when the first condition and the second condition are met, the first terminal device sends the first message to the second terminal device. When the first condition and the second condition are met, the first terminal device sends the first message to the second terminal device, so that when the first terminal device selects or reselects the second terminal device as a relay device, the reselection of the relay device will not be triggered due to failure to meet the second condition. Therefore, the first terminal device sends the first message to the second terminal device based on the second information and the first information, which can avoid selecting an inappropriate relay UE and causing additional communication connection establishment overhead, thereby improving communication quality.

[0007] In one possible implementation, the second information includes a second threshold or a second identifier, the second identifier corresponds to the second threshold, and the second condition includes: a second parameter measuring the signal quality between the first terminal device and the second terminal device is better than the second threshold; the first condition includes: a first parameter measuring the signal quality between the first terminal device and the second terminal device is better than the first threshold.

[0008] In this implementation, the second information includes a second threshold or a second identifier, and the first terminal device can accurately determine the second condition based on the second threshold or the second identifier.

[0009] In a possible implementation, the second information includes the second identifier; and the method further includes: acquiring a second corresponding relationship, where the second corresponding relationship includes a corresponding relationship between the second identifier and the second threshold.

[0010] In this implementation, the second information includes the second identifier, and the first terminal device can use the second identifier and the second corresponding relationship to obtain the second threshold value, and then obtain the second condition.

[0011] In a possible implementation, the second parameter or the first parameter includes any one of the following: a received signal strength indicator RSSI, a reference signal received power RSRP, a reference signal received quality RSRQ, and a signal to interference plus noise ratio SINR.

[0012] In a possible implementation, the first condition further includes: a duration from the current moment to the moment when the last communication connection was established exceeds a first duration.

[0013] In this implementation, the first condition stipulates that the relay UE can only be reselected after the time from the current moment to the time when the last communication connection was established exceeds the first time. This can avoid frequent triggering of the relay UE reselection process and causing excessive communication connection establishment overhead, thereby improving communication quality.

[0014] In a possible implementation, the second information is carried in an announcement message or in a response message to a solicitation message, the solicitation message is used to discover a relay device, and the announcement message is used to discover a relay device.

[0015] In this implementation, the second information is carried in an announcement message or in a response message to a solicitation message, which can reduce signaling overhead.

[0016] In a second aspect, an embodiment of the present application provides another communication method, which is applied to a second terminal device, and the method includes: receiving first information from a first terminal device; the first information indicates a first condition for the first terminal device to select or reselect a terminal device as a relay device; sending a second message to the first terminal device based on the first information and the second information; the second message is used by the first terminal device to discover the second terminal device; the second information indicates a second condition for the second terminal device to act as a relay device for the first terminal device.

[0017] In an embodiment of the present application, the second terminal device sends a second message to the first terminal device based on the first information and the second information, so that when the first terminal device (corresponding to the remote UE) selects or reselects the second terminal device (corresponding to the relay UE) as the relay device, the second terminal device meets the first condition and the second condition, thereby avoiding the selection of an inappropriate relay UE, resulting in additional communication connection establishment overhead and frequent triggering of the relay UE reselection process.

[0018] In one possible implementation, the first information includes a first threshold or a first identifier, the first identifier corresponds to the first threshold, and the first condition includes: a first parameter measuring the signal quality between the second terminal device and the first terminal device is better than the first threshold; the second condition includes: a second parameter measuring the signal quality between the second terminal device and the first terminal device is better than the second threshold.

[0019] In this implementation, the first information includes a first threshold or a first identifier, and the second terminal device can accurately determine the first condition based on the first threshold or the first identifier.

[0020] In a possible implementation, the first information includes the first identifier; and the method further includes: acquiring a first corresponding relationship, where the first corresponding relationship includes a corresponding relationship between the first identifier and the first threshold.

[0021] In this implementation, the first information includes a first identifier, and the second terminal device can use the first identifier and the first corresponding relationship to obtain a first threshold, and then obtain the first condition.

[0022] In a possible implementation, the second parameter or the first parameter includes any one of the following: a received signal strength indicator RSSI, a reference signal received power RSRP, a reference signal received quality RSRQ, and a signal to interference plus noise ratio SINR.

[0023] In a possible implementation manner, the first information is used to discover a relay device.

[0024] In this implementation, the first information can be used to discover the relay device and can also indicate the first condition, with low signaling overhead.

[0025] In a possible implementation, the first information is carried in an announcement message, and the second message is a response message to the first information.

[0026] In this implementation, the first information is carried in an announcement message, and the second message is a response message to the first information, which can reduce signaling overhead.

[0027] In a third aspect, the present application provides another communication method, which is applied to a second terminal device, and the method includes: receiving a third message from a first terminal device, the third message being used to discover a relay device; sending a fourth message to the first terminal device based on the second information; the second information indicating a second condition for the second terminal device to serve as a relay device for the first terminal device, and the fourth message indicating the second terminal device as a candidate relay device for the first terminal device.

[0028] In an embodiment of the present application, the second terminal device sends a fourth message to the first terminal device based on the second information; so that when the first terminal device (corresponding to the remote UE) selects / reselects the second terminal device (corresponding to the relay UE) as the relay device, the second terminal device will serve as the relay device of the first terminal device, which can avoid the first terminal device selecting an inappropriate relay UE, resulting in additional communication connection establishment overhead and frequent triggering of the relay UE reselection process, and improve the communication quality of the first terminal device.

[0029] In a possible implementation, the second condition includes: a second parameter measuring signal quality between the second terminal device and the first terminal device is greater than a second threshold.

[0030] In this implementation, the second condition includes: a second parameter measuring signal quality between the second terminal device and the first terminal device is greater than a second threshold. When the second condition is met, a fourth message is sent to the first terminal device, thereby ensuring the communication quality between the second terminal device and the first terminal device.

[0031] In a possible implementation, the second parameter includes any one of the following: a received signal strength indicator RSSI, a reference signal received power RSRP, a reference signal received quality RSRQ, and a signal to interference plus noise ratio SINR.

[0032] In a possible implementation, the third message is a solicitation message, and the fourth message is a response message to the third message.

[0033] In this implementation, a response message to the third message is sent to the first terminal device based on the second information; this can reduce signaling overhead and reduce the reselection process of triggering the relay UE.

[0034] In a possible implementation manner, the method further includes: receiving the second information from a network device.

[0035] In this implementation, the second information is received from the network device, and the second condition can be flexibly configured.

[0036] In a fourth aspect, an embodiment of the present application provides another communication method, which is applied to a first terminal device, and the method includes: establishing a communication connection with a third terminal device serving as a relay device; sending a fourth message or receiving a fifth message when a third condition is met; the third condition includes: the duration from the current moment of the first terminal device to the moment when the communication connection is established exceeds the first duration; the fourth message is used to discover the relay device, and the fifth message is used to discover the relay device.

[0037] In the embodiment of the present application, when the third condition is met, the fourth message is sent or the fifth message is received, so that the remote UE will not reselect the relay UE until a certain period of time has passed after the communication connection is established, which can avoid the remote UE frequently triggering the relay UE reselection process.

[0038] In one possible implementation, the third condition further includes: the first terminal device is to select or reselect a relay device. The relay device to be selected or reselected by the first terminal device may be that the first terminal device triggers the selection or reselection of the relay device, that is, the first terminal device currently meets the conditions for selecting or reselecting the relay device.

[0039] In this implementation, the first terminal device sends the fourth message or receives the fifth message when waiting to select or reselect the relay device, which can reduce signaling overhead.

[0040] In one possible implementation, the method further includes: receiving second information from a second terminal device; the second information indicates a second condition for the second terminal device to serve as a relay device for the first terminal device; and the third condition further includes: satisfying the second condition.

[0041] In this implementation, the third condition also includes: satisfying the second condition. When a first terminal device (an example of a remote UE) selects / reselects a second terminal device (an example of a relay UE) as a relay device, the second terminal device will serve as a relay device for the first terminal device, thereby avoiding the first terminal device selecting an inappropriate relay UE, resulting in additional communication connection establishment overhead and frequent triggering of the relay UE reselection process, and improving the communication quality of the first terminal device.

[0042] In one possible implementation, the second information includes a second threshold or a second identifier, the second identifier corresponds to the second threshold, and the second condition includes: a second parameter measuring the signal quality between the first terminal device and the second terminal device is better than the second threshold.

[0043] In this implementation, the second information includes a second threshold or a second identifier, and the first terminal device can accurately determine the second condition based on the second threshold or the second identifier.

[0044] In a fifth aspect, an embodiment of the present application provides another communication method, which is applied to a first terminal device, and the method includes: sending a sixth message or receiving a seventh message when the fourth condition is met; the sixth message is used to discover the relay device, and the seventh message is used to discover the relay device. The fourth condition includes: the first terminal device is in the OOC state within the coverage range and the duration of the OOC state reaches a second duration; or, the fourth condition includes: the first terminal device is in the OOC state and the first terminal device triggers an event to discover the relay device; or, the first terminal device switches from the OOC state to the IC state.

[0045] In an embodiment of the present application, when the fourth condition is met, sending the sixth message or receiving the seventh message can prevent the first terminal device from being in the OOC state for a long time and unable to be paged by the network.

[0046] In one possible implementation, the fourth condition includes: the first terminal device is in the OOC state within the coverage range and the duration of the OOC state reaches a second duration, and the first terminal device does not send or receive a message for discovering the relay device within the second duration.

[0047] In this implementation, the first terminal device determines to select a relay device when it is in the OOC state and has been in the OOC state for a second duration, and has not sent or received a message for discovering a relay device within the second duration. This can reduce the number of times the first terminal device sends the sixth message or receives the seventh message, saving signaling overhead.

[0048] In a possible implementation, the sixth message is a solicitation message, and the seventh message is an announcement message.

[0049] In this implementation, when the fourth condition is met, sending a solicitation message or receiving an announcement message can reduce receiving operations and sending operations.

[0050] In a possible implementation, the event triggering the discovery of the relay device includes any one of the following: arrival of periodic services, paging, area notification update RNAU based on the radio access network RAN, and tracking area update TAU.

[0051] In one possible implementation, the method further includes: when the first terminal device detects that the state has changed from the IC state within the coverage range to the OOC state, starting or restarting the timer; the time when the first terminal device is in the OOC state exceeds the second time, including the timer timing out.

[0052] In this implementation, the first terminal device can accurately determine, through the second timer, that the duration of being in the OOC state exceeds the second duration.

[0053] In a sixth aspect, an embodiment of the present application provides another communication method, which is applied to a first network device, and the method includes: receiving first indication information from a second network device; the first indication information indicates a second condition for a second terminal device accessing the second network device to serve as a relay device for the first terminal device; sending second indication information to the first terminal device; the second indication information is used to determine the second condition.

[0054] In an embodiment of the present application, the first network device sends second indication information to the first terminal device so that the first terminal device obtains the second condition that the second terminal device serves as a relay device for the first terminal device.

[0055] In a possible implementation, the first indication information includes a second threshold, and the second condition includes: a second parameter measuring the signal quality between the second terminal device and the first terminal device is better than the second threshold.

[0056] In this implementation manner, the first indication information includes a second threshold, so that the first network device determines the second condition according to the second threshold.

[0057] In a possible implementation, the second indication information includes a second corresponding relationship, the second corresponding relationship includes a corresponding relationship between a second identifier and the second threshold, and the second identifier corresponds to the second terminal device or the second network device.

[0058] In this implementation, the second indication information includes a second corresponding relationship, so that the first terminal device determines the second threshold value according to the second identifier and the second corresponding relationship, and further determines the second condition.

[0059] In a possible implementation, the first indication information further includes a second identifier, where the second identifier corresponds to the second terminal device or the second network device.

[0060] In this implementation, the first indication information further includes a second identifier, which enables the first network device to determine the correspondence between the second threshold and the second identifier.

[0061] In the seventh aspect, an embodiment of the present application provides another communication method, which is applied to a second network device, and the method includes: receiving third indication information from a first network device; the third indication information indicates a first condition for the first terminal device to select or reselect a terminal device as a relay device; sending fourth indication information to the second terminal device; the fourth indication information is used to determine the first condition.

[0062] In the embodiment of the present application, the second network device sends fourth indication information to the second terminal device so that the second terminal device obtains the first condition that the first terminal device serves as a relay device for the second terminal device.

[0063] In one possible implementation, the third indication information includes a first threshold, and the first condition includes: a first parameter measuring the signal quality between the first terminal device and the terminal device selected or reselected by the first terminal device as a relay device is better than the first threshold.

[0064] In this implementation manner, the third indication information includes a first threshold, so that the second network device determines the first condition according to the first threshold.

[0065] In a possible implementation, the fourth indication information includes a first correspondence, the first correspondence includes a correspondence between a first identifier and the first threshold, and the first identifier corresponds to the first terminal device or the first network device.

[0066] In this implementation, the fourth indication information includes the first corresponding relationship, so that the second terminal device determines the first threshold value according to the first identifier and the first corresponding relationship, and further determines the first condition.

[0067] In a possible implementation, the third indication information further includes a first identifier, where the first identifier corresponds to the first terminal device or the first network device.

[0068] In this implementation, the third indication information further includes a first identifier, so that the second network device can determine the correspondence between the first threshold and the first identifier.

[0069] In the eighth aspect, an embodiment of the present application provides a communication device, which is a first terminal device or is included in the first terminal device, and the communication device includes: a receiving unit for receiving second information from a second terminal device; the second information indicates a second condition for the second terminal device to act as a relay device for the first terminal device; a sending unit for sending a first message to the second terminal device based on the second information and the first information; the first message is used to establish a communication connection with the second terminal device, and the first information indicates the first condition for the first terminal device to select or reselect the second terminal device as a relay device.

[0070] In one possible implementation, the second information includes a second threshold or a second identifier, the second identifier corresponds to the second threshold, and the second condition includes: a second parameter measuring the signal quality between the first terminal device and the second terminal device is better than the second threshold; the first condition includes: a first parameter measuring the signal quality between the first terminal device and the second terminal device is better than the first threshold.

[0071] In a possible implementation, the second information includes the second identifier; and the receiving unit is further configured to receive a second corresponding relationship, where the second corresponding relationship includes a corresponding relationship between the second identifier and the second threshold.

[0072] In a possible implementation, the second parameter or the first parameter includes any one of the following: a received signal strength indicator RSSI, a reference signal received power RSRP, a reference signal received quality RSRQ, and a signal to interference plus noise ratio SINR.

[0073] In a possible implementation, the first condition further includes: a duration from the current moment to the moment when the last communication connection was established exceeds a first duration.

[0074] In a possible implementation, the second information is carried in an announcement message or in a response message to a request message, the request message is used to discover a relay device, and the announcement message is used to discover a relay device.

[0075] Regarding the technical effects brought about by the eighth aspect or various possible implementation methods, reference may be made to the introduction to the technical effects of the first aspect or the corresponding implementation methods.

[0076] In the ninth aspect, an embodiment of the present application provides a communication device, which is a second terminal device or is included in a second terminal device, and the communication device includes: a receiving unit for receiving first information from a first terminal device; the first information indicates a first condition for the first terminal device to select or reselect a terminal device as a relay device; a sending unit for sending a second message to the first terminal device based on the first information and the second information; the second message is used by the first terminal device to discover the second terminal device; the second information indicates a second condition for the second terminal device to act as a relay device for the first terminal device.

[0077] In one possible implementation, the first information includes a first threshold or a first identifier, the first identifier corresponds to the first threshold, and the first condition includes: a first parameter measuring the signal quality between the second terminal device and the first terminal device is better than the first threshold; the second condition includes: a second parameter measuring the signal quality between the second terminal device and the first terminal device is better than the second threshold.

[0078] In a possible implementation, the first information includes the first identifier; the receiving unit is further configured to receive a first corresponding relationship, where the first corresponding relationship includes a corresponding relationship between the first identifier and the first threshold.

[0079] In a possible implementation, the second parameter or the first parameter includes any one of the following: a received signal strength indicator RSSI, a reference signal received power RSRP, a reference signal received quality RSRQ, and a signal to interference plus noise ratio SINR.

[0080] In a possible implementation manner, the first information is used to discover a relay device.

[0081] In a possible implementation, the first information is carried in an announcement message, and the second message is a response message to the first information.

[0082] Regarding the technical effects brought about by the ninth aspect or various possible implementation methods, reference may be made to the introduction to the technical effects of the second aspect or the corresponding implementation methods.

[0083] In the tenth aspect, an embodiment of the present application provides a communication device, which is a second terminal device or is included in a second terminal device, and the communication device includes: a receiving unit, used to receive a third message from a first terminal device, and the third message is used to discover a relay device; a sending unit, used to send a fourth message to the first terminal device based on the second information; the second information indicates the second condition for the second terminal device to serve as a relay device of the first terminal device, and the fourth message indicates the second terminal device as a candidate relay device for the first terminal device.

[0084] In a possible implementation, the second condition includes: a second parameter measuring signal quality between the second terminal device and the first terminal device is greater than a second threshold.

[0085] In a possible implementation, the second parameter includes any one of the following: a received signal strength indicator RSSI, a reference signal received power RSRP, a reference signal received quality RSRQ, and a signal to interference plus noise ratio SINR.

[0086] In a possible implementation, the third message is a solicitation message, and the fourth message is a response message to the third message.

[0087] In a possible implementation manner, the receiving unit is further configured to receive the second information from a network device.

[0088] Regarding the technical effects brought about by the tenth aspect or various possible implementation methods, please refer to the introduction to the technical effects of the third aspect or the corresponding implementation methods.

[0089] In the eleventh aspect, an embodiment of the present application provides a communication device, which is a first terminal device or is included in the first terminal device, and the communication device includes: a sending unit or a receiving unit; the sending unit or the receiving unit is used to establish a communication connection with a third terminal device serving as a relay device; the sending unit is used to send a fourth message when a third condition is met; the receiving unit is used to receive a fifth message when the third condition is met; the third condition includes: the time from the current moment of the first terminal device to the moment when the communication connection is established exceeds the first time; the fourth message is used to discover the relay device, and the fifth message is used to discover the relay device.

[0090] In a possible implementation, the third condition further includes: a relay device to be selected or reselected.

[0091] In a possible implementation, the receiving unit is further used to receive second information from a second terminal device; the second information indicates a second condition for the second terminal device to serve as a relay device for the first terminal device; and the third condition also includes: satisfying the second condition.

[0092] In one possible implementation, the second information includes a second threshold or a second identifier, the second identifier corresponds to the second threshold, and the second condition includes: a second parameter measuring the signal quality between the first terminal device and the second terminal device is better than the second threshold.

[0093] Regarding the technical effects brought about by the eleventh aspect or various possible implementation methods, please refer to the introduction to the technical effects of the fourth aspect or the corresponding implementation methods.

[0094] In the twelfth aspect, an embodiment of the present application provides a communication device, which is a first terminal device or is included in the first terminal device, and the communication device includes: a sending unit or a receiving unit; the sending unit is used to send a sixth message when the fourth condition is met; the receiving unit is used to receive a seventh message when the fourth condition is met; the sixth message is used to discover the relay device, and the seventh message is used to discover the relay device, and the fourth condition includes: the first terminal device is in the OOC state within the coverage range and the duration of the OOC state reaches a second duration; or, the fourth condition includes: the first terminal device is in the OOC state and the first terminal device triggers an event to discover the relay device; or, the first terminal device switches from the OOC state to the IC state.

[0095] In one possible implementation, the fourth condition includes: the first terminal device is in the OOC state within the coverage range and the duration of the OOC state reaches a second duration, and the first terminal device does not send or receive a message for discovering the relay device within the second duration.

[0096] In a possible implementation, the sixth message is a request message, and the seventh message is an announcement message.

[0097] In a possible implementation, the event triggering the discovery of the relay device includes any one of the following: arrival of periodic services, paging, area notification update RNAU based on the radio access network RAN, and tracking area update TAU.

[0098] In one possible implementation, the communication device also includes: a timer, which is used to start or restart when the detection unit detects that the first terminal device is converted from the IC state within the coverage range to the OOC state; the time when the first terminal device is in the OOC state exceeds the second time, including the timer timing out.

[0099] Regarding the technical effects brought about by the twelfth aspect or various possible implementation methods, please refer to the introduction to the technical effects of the fifth aspect or the corresponding implementation methods.

[0100] In the thirteenth aspect, an embodiment of the present application provides a communication device, which is a first network device or is included in the first network device, and the communication device includes: a receiving unit for receiving first indication information from a second network device; the first indication information indicates a second condition for a second terminal device accessing the second network device to serve as a relay device for the first terminal device; a sending unit for sending second indication information to the first terminal device; the second indication information is used to determine the second condition.

[0101] In a possible implementation, the first indication information includes a second threshold, and the second condition includes: a second parameter measuring the signal quality between the second terminal device and the first terminal device is better than the second threshold.

[0102] In a possible implementation, the second indication information includes a second corresponding relationship, the second corresponding relationship includes a corresponding relationship between a second identifier and the second threshold, and the second identifier corresponds to the second terminal device or the second network device.

[0103] In a possible implementation, the first indication information further includes a second identifier, where the second identifier corresponds to the second terminal device or the second network device.

[0104] Regarding the technical effects brought about by the thirteenth aspect or various possible implementation methods, reference may be made to the introduction to the technical effects of the sixth aspect or corresponding implementation methods.

[0105] In the fourteenth aspect, an embodiment of the present application provides a communication device, which is a second network device or is included in the second network device, and the communication device includes: a receiving unit for receiving third indication information from the first network device; the third indication information indicates a first condition for the first terminal device to select or reselect a terminal device as a relay device; a sending unit for sending fourth indication information to the second terminal device; the fourth indication information is used to determine the first condition.

[0106] In one possible implementation, the third indication information includes a first threshold, and the first condition includes: a first parameter measuring the signal quality between the first terminal device and the terminal device selected or reselected by the first terminal device as a relay device is better than the first threshold.

[0107] In a possible implementation, the fourth indication information includes a first correspondence, the first correspondence includes a correspondence between a first identifier and the first threshold, and the first identifier corresponds to the first terminal device or the first network device.

[0108] In a possible implementation, the third indication information further includes a first identifier, where the first identifier corresponds to the first terminal device or the first network device.

[0109] Regarding the technical effects brought about by the fourteenth aspect or various possible implementation methods, reference may be made to the introduction to the technical effects of the seventh aspect or corresponding implementation methods.

[0110] In the fifteenth aspect, an embodiment of the present application provides a communication device, which includes a processor, and the processor is used to execute computer-executable instructions stored in a memory so that the communication device executes the method of the above-mentioned first aspect, the above-mentioned fourth aspect or the above-mentioned fifth aspect and any possible implementation method.

[0111] In a possible implementation, the memory is located outside the communication device.

[0112] In a possible implementation, the memory is located within the above-mentioned communication device.

[0113] In a possible implementation, the processor and the memory may also be integrated into one device, that is, the processor and the memory may also be integrated together.

[0114] In a possible implementation, the communication device further includes a transceiver, and the transceiver is used to receive messages or send messages, etc.

[0115] In the sixteenth aspect, an embodiment of the present application provides a communication device, which includes a processor, and the processor is used to execute computer-executable instructions stored in a memory so that the communication device executes the method of the above-mentioned second aspect or the above-mentioned third aspect and any possible implementation method.

[0116] In the seventeenth aspect, an embodiment of the present application provides a communication device, which includes a processor, and the processor is used to execute computer-executable instructions stored in a memory so that the communication device executes the method of the above-mentioned sixth aspect or the above-mentioned seventh aspect and any possible implementation method.

[0117] In aspect 18, an embodiment of the present application provides a communication device, which includes a logic circuit and an interface, wherein the interface is used to obtain data or output data; the logic circuit is used to execute the corresponding method as shown in the above-mentioned first aspect, the above-mentioned fourth aspect or the above-mentioned fifth aspect and any possible implementation method.

[0118] In the nineteenth aspect, an embodiment of the present application provides a communication device, which includes a logic circuit and an interface, wherein the interface is used to obtain data or output data; the logic circuit is used to execute the corresponding method shown in the above-mentioned second aspect or the above-mentioned third aspect and any possible implementation method.

[0119] In the twentieth aspect, an embodiment of the present application provides a communication device, which includes a logic circuit and an interface, wherein the interface is used to obtain data or output data; the logic circuit is used to execute the corresponding method as shown in the sixth or seventh aspect above and any possible implementation method.

[0120] In the twenty-first aspect, an embodiment of the present application provides a communication system, which includes a first network device and a first terminal device, wherein the first terminal device can be used to execute the corresponding method shown in the first aspect or any possible implementation of the first aspect, and the first network device is used to execute the corresponding method shown in the sixth aspect or any possible implementation of the sixth aspect.

[0121] In the twenty-second aspect, an embodiment of the present application provides a communication system, which includes a second network device and a second terminal device, wherein the second terminal device can be used to execute the corresponding method shown in the second aspect or any possible implementation of the second aspect, and the second network device is used to execute the corresponding method shown in the seventh aspect or any possible implementation of the seventh aspect.

[0122] In the twenty-third aspect, the present application provides a computer-readable storage medium for storing a computer program, which, when run on a computer, enables the method shown in any possible implementation of the above-mentioned first to sixth aspects or the first to sixth aspects to be executed.

[0123] In aspect 24, the present application provides a computer program product comprising a computer program or computer code, which, when executed on a processor, enables the method shown in any possible implementation of aspects 1 to 6 or aspects 1 to 6 to be executed. BRIEF DESCRIPTION OF THE DRAWINGS

[0124] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the background technology, the drawings required for use in the embodiments of the present application or the background technology will be described below.

[0125] Figure 1 This is a schematic diagram of a resource acquisition method;

[0126] Figure 2 This is a diagram of another way to obtain resources;

[0127] Figure 3 A schematic diagram of a discovery process provided in an embodiment of the present application;

[0128] Figure 4 A schematic diagram of another discovery process provided in an embodiment of the present application;

[0129] Figure 5 A schematic diagram of an application scenario of a UE to NW relay is provided for an embodiment of the present application;

[0130] Figure 6 A schematic diagram of another application scenario of UE to NW relay is provided for an embodiment of the present application;

[0131] Figure 7 A flowchart showing a remote UE selecting or reselecting a relay UE is shown;

[0132] Figure 8 The conditions for triggering the remote UE to reselect the relay UE and the conditions that need to be met to become a candidate relay UE of the remote UE are shown;

[0133] Figure 9 A schematic diagram of a process for triggering selection / reselection of a relay UE multiple times according to different configurations provided in an embodiment of the present application;

[0134] Figure 10 A schematic diagram of a UE to NW relay communication scenario provided in an embodiment of the present application;

[0135] Figure 11 A flow chart of a communication method provided in an embodiment of the present application;

[0136] Figure 12 A flow chart of another communication method provided in an embodiment of the present application;

[0137] Figure 13 A flow chart of another communication method provided in an embodiment of the present application;

[0138] Figure 14 A flow chart of another communication method provided in an embodiment of the present application;

[0139] Figure 15 A flow chart of another communication method provided in an embodiment of the present application;

[0140] Figure 16 A flow chart of another communication method provided in an embodiment of the present application;

[0141] Figure 17 A flow chart of another communication method provided in an embodiment of the present application;

[0142] Figure 18 A flow chart of another communication method provided in an embodiment of the present application;

[0143] Figure 19 A flow chart of another communication method provided in an embodiment of the present application;

[0144] Figure 20 A flow chart of another communication method provided in an embodiment of the present application;

[0145] Figure 21 A flow chart of another communication method provided in an embodiment of the present application;

[0146] Figure 22 A flow chart of another communication method provided in an embodiment of the present application;

[0147] Figure 23 A flow chart of another communication method provided in an embodiment of the present application;

[0148] Figure 24 A flow chart of another communication method provided in an embodiment of the present application;

[0149] Figure 25 A flow chart of another communication method provided in an embodiment of the present application;

[0150] Figure 26 A flow chart of another communication method provided in an embodiment of the present application;

[0151] Figure 27 A flow chart of another communication method provided in an embodiment of the present application;

[0152] Figure 28 A schematic diagram of a remote UE moving from an IC state to an OOC state due to movement provided in an embodiment of the present application;

[0153] Figure 29 A flow chart of another communication method provided in an embodiment of the present application;

[0154] Figure 30 A flow chart of another communication method provided in an embodiment of the present application;

[0155] Figure 31 A schematic diagram of the structure of a communication device provided in an embodiment of the present application;

[0156] Figure 32 A schematic structural diagram of another communication device provided in an embodiment of the present application;

[0157] Figure 33 A schematic structural diagram of another communication device provided in an embodiment of the present application;

[0158] Figure 34 A schematic structural diagram of another communication device provided in an embodiment of the present application;

[0159] Figure 35 A schematic diagram of the structure of another communication device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0160] In order to make the purpose, technical solutions and advantages of this application clearer, this application will be further described below with reference to the accompanying drawings.

[0161] The terms "first" and "second" in the specification, claims, and drawings of this application are used only to distinguish different objects and are not used to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units that are not listed, or may optionally include other steps or units that are inherent to the process, method, product, or device.

[0162] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it refer to independent or alternative embodiments that are mutually exclusive of other embodiments. It will be understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0163] In a UE-to-NW relay scenario, after selecting or reselecting a relay UE, the remote UE establishes a unicast connection with the selected or reselected relay UE to access the network. If the remote UE selects or reselects an unsuitable relay UE, it will quickly trigger the selection or reselection of the relay UE again. This results in unnecessary unicast connection establishment and increases the delay in selecting a suitable relay UE, affecting the communication quality of the remote UE. If the remote UE triggers the selection (reselection) of the relay UE again within a short period of time (e.g., 100ms, 1s, etc.) after selecting (or reselecting) a relay UE, the relay UE is an unsuitable relay UE for the remote UE. If the remote UE does not trigger the selection (reselection) of the relay UE within a short period of time after selecting (or reselecting) a relay UE, the relay UE is a suitable relay UE for the remote UE. Currently, the scheme adopted by the remote UE for selecting or reselecting a relay UE has a low probability of selecting a suitable relay UE. Therefore, it is necessary to study a better scheme for selecting or reselecting a relay UE to avoid selecting or reselecting an unsuitable relay UE.

[0164] The current scheme used by remote UEs to select or reselect relay UEs has a low probability of selecting a suitable relay UE, which can reduce the remote UE's communication quality. Therefore, research is needed to improve schemes for selecting or reselecting relay UEs to prevent the remote UE from selecting or reselecting an unsuitable relay UE. This application provides a communication scheme that can select or reselect a more suitable relay UE, thereby improving the remote UE's communication quality. The following describes technologies and knowledge related to selecting or reselecting a relay UE, with reference to the accompanying figures.

[0165] 1) Resource acquisition method

[0166] In the UE to NW relay scenario, the transmitting user equipment (Tx UE) needs to obtain resources in advance before sending data through the SL. The Tx UE is the terminal device that sends data and can be either a remote UE or a relay UE. The Tx UE obtains resources in two ways:

[0167] Mode 1 (mode 1): Network device (such as base station) scheduling mode. Figure 1 A schematic diagram of a resource acquisition method. Figure 1The resource acquisition method of method 1 is shown. Figure 1 It can be seen that UE (i.e. Figure 1 The car in the network receives SL authorization from the network device.

[0168] Mode 2: UE autonomous competition mode. Figure 2 A diagram showing another way to obtain resources. Figure 2 The resource acquisition method of method 2 is shown. Figure 2 It can be seen that UE (i.e. Figure 2 The car in the network selects empty and unoccupied resources for transmission without obtaining SL authorization from the network device.

[0169] 2) Modes in which relay UE and remote UE discover each other

[0170] Before establishing a unicast connection between the relay UE and the remote UE, the relay UE and the remote UE may need to perform a discovery process to discover each other. The modes for discovering each other can include the following:

[0171] Model A: The relay UE broadcasts an announcement message to the surroundings, and the remote UE discovers the relay UE after receiving the message. Figure 3 A schematic diagram of a discovery process provided in an embodiment of the present application. Figure 3 In the example, UE1 broadcasts an announcement message to the surrounding area; UE2 (UE3) discovers UE1 based on the announcement message from UE1.

[0172] Model B: The remote UE broadcasts a solicitation message to its neighbors to discover (or find) a relay UE. Upon receiving the solicitation message, the relay UE can reply with a response message if conditions permit, allowing the remote UE to discover the relay UE. Figure 4 This is a schematic diagram of another discovery process provided in the embodiment of the present application. Figure 4 As shown, UE4 broadcasts a solicitation message to the surroundings; UE5 (or UE6) receives the solicitation message from UE4 and can reply with a response message if conditions permit, so that UE4 can discover UE5 (or UE6).

[0173] 3) Threshold requirements that relay UE and remote UE need to meet when sending discovery messages

[0174] Generally speaking, a relay UE must meet certain threshold requirements for sending discovery messages. In this application, a discovery message refers to an announcement message, a solicitation message, or a response message to a solicitation message. The following describes, with reference to the accompanying figures, the threshold requirements for a relay UE in RRC idle or inactive state to send discovery messages. Figure 5 A schematic diagram of an application scenario of UE to NW relay is provided for an embodiment of the present application. Figure 5 In the figure, relay UE1 indicates a relay UE whose Uu interface signal quality is less than threshold 1. Relay UE2 indicates a relay UE whose Uu interface signal quality is greater than or equal to threshold 2 (threshold 1) and less than or equal to threshold 1. That is, relay UE whose Uu interface signal quality is within threshold 2 and threshold 1. Relay UE3 indicates a relay UE whose Uu interface signal quality is greater than threshold 2. Threshold 1 is less than threshold 2. Figure 5 The relay UE2 in the example meets the threshold requirement for sending the discovery message, while the relay UE1 and the relay UE3 do not meet the threshold requirement for sending the discovery message.

[0175] Similarly, the remote UE must also meet certain threshold requirements for sending discovery messages. The following describes the threshold requirements that must be met for remote UEs in RRC idle and inactive states to send discovery messages, with reference to the accompanying figures. Figure 6 A schematic diagram of another application scenario of UE to NW relay provided in an embodiment of the present application. Figure 6 In the figure, remote UE1 represents a remote UE whose signal quality of the Uu port is greater than or equal to a threshold (ie, a threshold broadcast by a network device), and remote UE2 and remote UE3 both represent remote UEs whose signal quality of the Uu port is less than the threshold. Figure 6 In the example, remote UE2 and remote UE3 both meet the threshold requirement for sending discovery messages, but remote UE1 does not meet the threshold requirement for sending discovery messages.

[0176] It can be understood that OOC may mean not being within the coverage of any network device, not being within the coverage of a network device supporting sidelink communication, or specifically not being within the coverage of a specific network device.

[0177] Correspondingly, in coverage (IC) may refer to being within the coverage of any network device, within the coverage of a network device supporting sidelink communication, or specifically within the coverage of a specific network device.

[0178] 4) The remote UE selects or reselects the relay UE

[0179] Figure 7 FIG1 shows a flow chart of a remote UE selecting or reselecting a relay UE. Figure 7 As shown, when the remote UE is in OOC, or in IC but the air interface signal quality Uu-reference signal received power (RSRP) is less than the threshold threshHigh, the remote UE will be triggered to select or reselect the relay UE.

[0180] Furthermore, when the remote UE does not have a selected (i.e., selected) relay UE, or the sidelink reference signal received power (SL-RSRP) corresponding to the currently selected relay UE is lower than the threshold q-RxLevMin, or a radio link failure (RLF) occurs in the current SL, the remote UE needs to select a relay UE that satisfies the SL-RSRP requirement of being higher than (q-RxLevMin plus minHyst). The SL-RSRP can be obtained by measuring the SD-RSRP obtained by the discovery message, or by measuring the reference signal after establishing a unicast connection. When there are multiple relay UEs whose corresponding SL-RSRPs meet the requirements, the remote UE decides which relay UE to select.

[0181] Note that exceeding q-RxLevMin plus minHyst can be interpreted as exceeding q-RxLevMin by minHyst. Here, q-RxLevMin is a threshold, and minHyst is an offset in dB (a 3dB increase means double the original value). In other words, minHyst describes q-RxLevMin and is a relative value. For example, "exceeds q-RxLevMin by 0dB" means "exceeds q-RxLevMin." Another example is "exceeds q-RxLevMin by 3dB" means "exceeds 2*q-RxLevMin." Figure 8 The conditions for triggering the remote UE to reselect the relay UE and the conditions that need to be met to become a candidate relay UE of the remote UE are shown. Figure 8 As shown, the condition for triggering the remote UE to reselect a relay UE is that the corresponding SL-RSRP is lower than q-RxLevMin. The condition for becoming a candidate relay UE for the remote UE is that the corresponding SL-RSRP is higher than q-RxLevMin plus minHyst. For example, if the SL-RSRP of a relay UE is higher than q-RxLevMin plus minHyst, the relay UE meets the conditions for becoming a candidate relay UE for the remote UE.

[0182] The remote UE determines the conditions for triggering the selection or reselection of the relay UE based on the currently acquired configuration parameters (e.g., q-RxLevMin0, minHyst0, etc.). For example, the remote UE acquires the configuration parameters for determining the conditions for triggering the selection or reselection of the relay UE based on a pre-configuration message, a system information block (SIB) message, or RRC dedicated signaling.

[0183] 5) Signal quality measurement

[0184] It should be clarified that the description of signal quality in this application uses RSRP as an example. It is understandable that RSRP can also be replaced by parameters such as received signal strength indication (RSSI), reference signal received power RSRP, reference information received quality (RSRQ), and signal to interference plus noise ratio (SINR). SL-RSRP can be the SD-RSRP obtained by measuring a discovery message (such as an announcement message or a response message), or it can be obtained by measuring the reference signal after establishing a unicast connection.

[0185] An example of measuring SL-RSRP after establishing a unicast connection (UE1 and UE2 establish a unicast connection) is as follows:

[0186] S1, UE1 determines the first receiving power of the signal sent by UE2. The signal sent by UE2 may include a reference signal sent through a physical sidelink shared channel (PSSCH) or a physical sidelink control channel (PSCCH). The first receiving power may be the power of the signal sent by UE2 received by UE1. The power of the signal sent by UE2 is the first transmitting power. The first transmitting power is the transmitting power of the signal determined by UE2 taking into account the sidelink channel conditions between UE1 and UE2. The first transmitting power may be determined by UE2 based on the sidelink channel conditions between UE1 and UE2. The sidelink channel conditions include path loss. UE1 and UE2 establish a sidelink unicast link, or a PC5 unicast link, or a PC5 RRC connection, or a direct link, or a layer 2 link.

[0187] S2, UE2 sends first power indication information to UE1. The first power indication information is used to indicate the first transmit power. UE2 can determine the first transmit power based on the sidelink channel conditions between UE1 and UE2. In addition, the second transmit power is the transmit power of the signal sent by UE2 without considering the sidelink channel conditions between UE1 and UE2. That is to say, the second transmit power is independent of the sidelink channel conditions between UE1 and UE2. For example, the second transmit power is determined based on the downlink path loss and / or maximum transmit power of UE2. Alternatively, the second transmit power is the power of UE2 sending a discovery message. The power of sending a discovery message can be understood as the power of sending a reference signal of the channel carrying the discovery message. The channel carrying the discovery message can be PSSCH or a physical sidelink discovery channel (PSDCH).

[0188] S3. UE1 determines the SL-RSRP based on the first receiving power, the first transmitting power, and the second transmitting power. For example, SL-RSRP is equal to the first receiving power plus the second transmitting power minus the first transmitting power. UE1 can obtain the first transmitting power based on the first power indication information. UE1 may pre-store the second transmitting power (for example, the power for UE2 to send a discovery message), or may determine the second transmitting power based on the downlink path loss and / or the maximum transmitting power of UE2. UE1 may determine whether to trigger the relay UE reselection or discovery process based on the first receiving power, the first transmitting power, and the second transmitting power. For example, if the first receiving power plus the second transmitting power minus the first transmitting power is less than or equal to the preset threshold (q-RxLevMin), the relay UE reselection or discovery process is triggered.

[0189] Figure 9 The embodiment of the present application provides a schematic diagram of a process of triggering the selection / reselection of a relay UE multiple times according to different configurations. Figure 9 As shown, the process of the remote UE triggering multiple relay UE selection / reselection based on different configurations is as follows: the remote UE selects / reselects relay UE1 based on the zeroth configuration (i.e., config0); the remote UE selects / reselects relay UE2 based on the first configuration (i.e., config1); and the remote UE selects / reselects relay UE3 based on the second configuration (i.e., config2). The first configuration (i.e., config1) is obtained by the remote UE from the serving / camping cell of relay UE1; the second configuration (i.e., config2) is obtained by the remote UE from the serving / camping cell of relay UE2.

[0190] How to ensure that a remote UE does not trigger relay device reselection within a short period of time after selecting or reselecting a relay UE is a current problem that needs to be solved. This application provides a communication solution that can improve the communication quality of the remote UE. The following, combined with the accompanying figures, describes application scenarios in which the communication solution for selecting or reselecting a relay UE provided in this application is applicable.

[0191] The communication scheme for selecting or reselecting a relay UE provided in this application is applicable to UE to NW relay communication scenarios, such as L2 UE to NW relay or L3 UE to NW relay. A network device is an entity on the network side that transmits or receives signals, such as an eNB or gNB. A terminal device is an entity on the user side that receives or transmits signals, such as a mobile phone. Due to the wide range of application scenarios for base stations and UEs, the following figures use a base station as an example of a network device and a UE as an example of a terminal device.

[0192] Figure 10 A schematic diagram of a UE to NW relay communication scenario provided in an embodiment of the present application. Figure 10 As shown, the communication scenario of UE to NW relay includes: a base station (such as gNB), one or more remote UE terminal devices ( Figure 10 Only one is shown) and one or more terminal devices as relay UEs ( Figure 10 Only one is shown). Figure 10 As shown, the remote UE accesses the base station through the relay UE. In other words, the remote UE accesses the serving / camped cell accessed by the relay UE through the relay UE. Figure 10 In the embodiment of the present invention, the relay UE can be in RRC connected state or RRC idle state / RRC inactive state. The remote UE can be in OOC state, RRC idle state / RRC inactive state or RRC connected state. The remote UE and the relay UE communicate via SL. The communication solution provided in this application can be applied to long term evolution (LTE) system, 4G system, new radio (NR) system, next generation wireless local area network system, etc., and this application does not limit it.

[0193] Several schemes for selecting or reselecting a relay UE provided by this application are described below with reference to the accompanying drawings.

[0194] Figure 11 This is a flow chart of a communication method provided in an embodiment of the present application. Figure 11 As shown, the method includes:

[0195] 1101. When a first condition is met, the first terminal device sends a direct communication request message to the second terminal device.

[0196] The direct communication request message is used to establish a unicast connection with the second terminal device. That is, the purpose of the first terminal device sending the direct communication request message to the second terminal device may be to request the establishment of a unicast communication connection with the second terminal device. If the first condition is met, the first terminal device sending the direct communication request message to the second terminal device indicates that the first terminal device selects or reselects the second terminal device as a relay device if the first condition is met.

[0197] The first condition may be a condition for the first terminal device to select or reselect the second terminal device as the relay device, rather than a condition that triggers the first terminal device to select or reselect the relay UE. For example, the condition that triggers the first terminal device to select or reselect the relay UE is that the first terminal device does not have a selected relay UE or the SL-RSRP corresponding to the currently selected relay UE is lower than the threshold q-RxLevMin, and the condition for the first terminal device to select or reselect the second terminal device as the relay device is that the SL-RSRP corresponding to the second terminal device is higher than q-RxLevMin plus minHyst.

[0198] 1102. The first terminal device receives a direct communication acceptance message from the second terminal device.

[0199] The first terminal device receives a direct communication accept message (directcommunication accept) from the second terminal device, thereby completing the establishment of a unicast connection with the second terminal device.

[0200] 1103. When the second condition is not met, the first terminal device triggers reselection of the relay device.

[0201] The second condition may be a threshold requirement of the signal quality between the first terminal device and the second terminal device set by the cell where the second terminal device (relay UE) resides / serves. For example, when the signal quality between the first terminal device and the second terminal device does not meet the threshold requirement of the signal quality between the first terminal device and the second terminal device set by the cell where the second terminal device (relay UE) resides / serves, the cell where the second terminal device (relay UE) resides / serves denies access to the first terminal device or the second terminal device.

[0202] Figure 11In the method flow, the first terminal device only considers the first condition when selecting or reselecting the second terminal device as the relay device, but does not consider the second condition. This may cause the relay device to be reselected after the first terminal device establishes a communication connection with the second terminal device because the second condition is not met. It is understandable that Figure 11 In the method flow, after the first terminal device establishes a communication connection with the second terminal device, the reason for triggering the reselection of the relay device is that the first terminal device selects or reselects the second terminal device as the relay device when the second condition is not met. In other words, when the first terminal device selects or reselects the second terminal device as the relay device, it does not consider whether the signal quality (for example, SL-RSRP) between the first terminal device and the second terminal device meets the threshold requirements of the cell where the second terminal device resides / serves.

[0203] Figure 11 In the method flow, since the first terminal device and the second terminal device establish a communication connection, the relay device will be triggered to reselect. Figure 11 The method flow in this article will cause unnecessary communication connections to be established. Figure 11 In order to solve the problem of unnecessary communication connection establishment caused by the method flow in the present application, the present application provides some solutions for selecting or reselecting relay devices that can solve this problem. These solutions mainly include: when the first condition and the second condition are met, the first terminal device selects or reselects the second terminal device as a relay device. The first condition may be a condition that needs to be met for the first terminal device to select or reselect a terminal device as a relay device. For example, the first condition is that the SL-RSRP (corresponding to the first parameter) between the first terminal device and the second terminal device is greater than the first threshold (for example, q-RxLevMin plus minHyst). The second condition may be a condition for the second terminal device to serve as a relay device for other terminal devices. The second condition can be understood as a condition that the cell where the second terminal device resides / serves allows the terminal device to access. For example, the second condition is a condition that needs to be met for the second terminal device to select or reselect a terminal device as a relay device. For example, the second condition is that the SL-RSRP (corresponding to the second parameter) between the second terminal device and the first terminal device is greater than the second threshold. The first condition may be equivalent to Figure 7 The conditions for remote UE to select or reselect relay UE in the method flow are that SL-RSRP is higher than q-RxLevMin plus minHyst. The first condition corresponds to Figure 9 In config0, the second condition corresponds to Figure 9 config1. Alternatively, the first condition corresponds to Figure 9 In config1, the second condition corresponds to Figure 9 config2. Figure 9The scheme for selecting or reselecting a relay device is as follows: when the first condition (corresponding to config0) is met, relay UE1 is selected or reselected. Alternatively, when the first condition (corresponding to config1) is met, relay UE2 is selected or reselected. Alternatively, when the first condition (corresponding to config2) is met, relay UE2 is selected or reselected. Figure 9 Compared to the solution shown in the preceding example, the present application provides an example of a solution for selecting or reselecting a relay device as follows: When the first condition (corresponding to config0) and the second condition (corresponding to config1) are met, relay UE1 is selected or reselected. Alternatively, when the first condition (corresponding to config1) and the second condition (corresponding to config2) are met, relay UE2 is selected or reselected. Alternatively, when the first condition (corresponding to config2) and the second condition (corresponding to config3) are met, relay UE3 is selected or reselected.

[0204] An example of a solution for selecting or reselecting a relay device provided in this application is described below with reference to the accompanying drawings.

[0205] Figure 12 This is another flow chart of a communication method provided in an embodiment of the present application. Figure 12 As shown, the method includes:

[0206] 1201. The first terminal device obtains second information.

[0207] One possible implementation of step 1201 is to receive second information from a second terminal device (an example of a relay UE). Another possible implementation of step 1201 is to have the first terminal device obtain preconfigured or predefined second information. Another possible implementation of step 1201 is to have the first terminal device obtain the second information from another device (e.g., a network device). For example, the first terminal device obtains the second information from a network device to which it is connected.

[0208] The second information indicates a second condition for the second terminal device to serve as a relay device for the first terminal device.

[0209] In one possible implementation, the second information includes information indicating the second threshold, and a second parameter or information indicating the second parameter. The second information may also include other information, which is not limited in this application. The first terminal device may determine the second condition based on the information indicating the second threshold contained in the second information, and the second parameter or information indicating the second parameter. For example, the second information includes information indicating the second threshold (for example, 10) and information indicating the second parameter (for example, 10). The first terminal device may determine the second threshold based on the information indicating the second threshold, and determine the second parameter based on the information indicating the second parameter. For example, the second information includes information indicating the second threshold and a second parameter. The first terminal device may determine the second threshold based on the information indicating the second threshold. Alternatively, the second information may include the second threshold or information indicating the second threshold, wherein the second parameter is a predefined parameter. For example, the first terminal device obtains the second threshold based on the second information, and determines the second condition based on the second threshold and the predefined second parameter.

[0210] In one possible implementation, the second information includes a second threshold or a second identifier, and the second identifier corresponds to the second threshold. The second condition includes: a second parameter for measuring the signal quality between the first terminal device and the second terminal device is better than the second threshold. Alternatively, the second condition includes: determining that the second parameter is better than the second threshold; wherein the second parameter is a parameter obtained by measurement that characterizes (or indicates) the signal quality between the first terminal device and the second terminal device. Alternatively, the second condition includes: judging that the second parameter is better than the second threshold; wherein the second parameter is a parameter obtained by measurement that characterizes (or indicates) the signal quality between the first terminal device and the second terminal device. Alternatively, the second condition includes: the second parameter for evaluating (or characterizing) the signal quality between the first terminal device and the second terminal device is better than the second threshold. In this application, signal quality can be replaced by link quality, communication quality, connection quality, signal strength, etc.

[0211] In this application, "better than" can be understood as greater than or less than. If the second parameter is positively correlated with the signal quality, that is, the larger the second parameter is, the better the signal quality is, then the second parameter is better than the second threshold value means that the second parameter is greater than the second threshold value. For example, if the second parameter is RSRP, the second parameter is better than the second threshold value means that the second parameter is greater than the second threshold value. For another example, if the second parameter is RSSI, the second parameter is better than the second threshold value means that the second parameter is greater than the second threshold value. If the second parameter is negatively correlated with the signal quality, that is, the larger the second parameter is, the worse the signal quality is, then the second parameter is better than the second threshold value means that the second parameter is less than the second threshold value.

[0212] The second parameter includes any one of the following: RSSI, RSRP, RSRQ, SINR. In some embodiments, the second terminal device obtains the second information or the information used to generate the second information through a pre-configuration message, a SIB message, a dedicated RRC signaling, etc.

[0213] The second threshold may include one or more of the second q-RxLevMin, the second minHyst, the second threshHigh, and the second hystMax. For example, the second threshold is the second q-RxLevMin or the second threshHigh. For another example, the second threshold is the second q-RxLevMin plus the second minHyst. The second threshHigh may be a threshold that triggers the second terminal device to select or reselect the relay device. For example, the air interface signal quality (e.g., Uu-RSRP) of the second terminal device is less than the threshold second threshHigh, and the second terminal device will be triggered to select or reselect the relay UE. The second q-RxLevMin may be a threshold that triggers the second terminal device to select or reselect the relay device, and the second minHyst is a relative value used to describe the second q-RxLevMin. For example, when the SL-RSRP corresponding to the relay UE currently selected by the second terminal device is lower than the threshold second q-RxLevMin, the second terminal device reselects the relay UE that satisfies the SL-RSRP higher than (the second q-RxLevMin plus the second minHyst). The second threshold value may also be other values, which are not limited in this application. The second threshold value may be a threshold value derived from the second q-RxLevMin, such as 1.1*second q-RxLevMin, 1.2*second q-RxLevMin, etc. The second threshold value may be a threshold value derived from the second threshHigh, such as 1.1*second threshHigh, 1.2*second threshHigh, etc. The second threshold value may be a threshold value derived from the second q-RxLevMin and the second minHyst, such as 1.1*(second q-RxLevMin plus second minHyst), 0.9*(second q-RxLevMin plus second minHyst), etc.

[0214] In one possible implementation, the second information is carried in an announcement message or a response message to a solicitation message. The solicitation message is used to discover relay devices, and the announcement message is used to discover relay devices. The announcement can also be understood as the relay device allowing itself to be discovered by other devices.

[0215] In one possible implementation, when the third parameter is not better than the third threshold or the fourth parameter measuring the signal quality between the above-mentioned first terminal device and the relay device currently selected or connected to it is not better than the fourth threshold, the above-mentioned first terminal device receives the second information from the second terminal device. The above-mentioned third parameter is used to measure the quality of the signal received by the above-mentioned first terminal device from the service cell or the resident cell of the above-mentioned first terminal device. The third parameter can be any one of RSSI, RSRP, RSRQ, and SINR, and the fourth parameter can be any one of RSSI, RSRP, RSRQ, and SINR. The third threshold may be the same as or different from the first threshold. The fourth threshold may be the same as or different from the first threshold. The fact that the third parameter is not better than the third threshold or the fourth parameter measuring the signal quality between the above-mentioned first terminal device and the relay device currently selected or connected to it is not better than the fourth threshold can be understood as a condition for the first terminal device to trigger the selection or reselection of the relay device. For example, when the first terminal device (i.e., remote UE) determines that the Uu-RSRP of the current serving / resident cell is less than a third threshold (e.g., threshHigh), or the SL-RSRP of the currently selected / connected relay UE is less than a fourth threshold (e.g., q-RxLevMin), the second information from the second terminal device is received, i.e., step 1201 is executed. In this implementation, the third parameter is not better than the third threshold or the fourth parameter that measures the signal quality between the above-mentioned first terminal device and its currently selected or connected relay device is not better than the fourth threshold can be understood as a condition that triggers the first terminal device to select or reselect the relay device. In this implementation, when the condition that triggers the first terminal device to select or reselect the relay device is met, receiving the second information from the second terminal device can reduce the workload.

[0216] 1202. The first terminal device sends a first message to the second terminal device based on the second information and the first information.

[0217] In one possible implementation, the first terminal device is preconfigured with the first information or predefined with the first information. In another possible implementation, the first terminal device obtains the first information from another device (e.g., a network device or a terminal device). For example, the first terminal device obtains the first information from a network device to which it is connected.

[0218] Step 1202 can be replaced by: the first terminal device sends the first message to the second terminal device based on the second information. The first terminal device sending the first message to the second terminal device based on the second information can be: sending the first message to the second terminal device if the second condition is met; sending the first message to the second terminal device when the second condition is met; or sending the first message to the second terminal device where the first terminal device meets the second condition. The first terminal device sending the first message to the second terminal device based on the second information can avoid disconnecting the communication connection with the second terminal device within a short period of time after establishing the communication connection, and avoiding short or frequent reselection of a terminal device as a relay device.

[0219] The first message is used to establish a communication connection with the second terminal device. The purpose of the first terminal device sending the first message to the second terminal device may be to request the establishment of a communication connection with the second terminal device. The first information indicates a first condition for the first terminal device to select or reselect the second terminal device as a relay device. In one possible implementation, the first condition includes: a first parameter measuring the signal quality between the second terminal device and the first terminal device is greater than a first threshold. The first information may include the first threshold or information indicating the first threshold (e.g., 01), as well as the first parameter or information indicating the first parameter (e.g., 01). The first information may also include other information, which is not limited in this application. The first terminal device may determine the first condition based on the first threshold or information indicating the first threshold, and the first parameter or information indicating the first parameter contained in the first information. For example, the first information may include the first threshold and the first parameter. For another example, the first information may include the first threshold and information indicating the first parameter. The first terminal device may determine the first parameter based on the information indicating the first parameter. For another example, the first information may include information indicating the first threshold and the first parameter. The first terminal device may determine the first threshold based on the information indicating the first threshold. For another example, the first information may include information indicating the first threshold and the first parameter. The first terminal device may determine the first threshold based on the information indicating the first threshold, and determine the first parameter based on the information indicating the first parameter. Alternatively, the first information may include the first threshold or the information indicating the first threshold, wherein the first parameter is a predefined parameter. For example, the first terminal device obtains the first threshold based on the first information, and determines the first condition based on the first threshold and the predefined first parameter.

[0220] Alternatively, the first condition includes: determining that the first parameter is better than a first threshold; wherein the first parameter is a parameter obtained by measurement that characterizes (or indicates) the signal quality between the first terminal device and the second terminal device. Alternatively, the first condition includes: judging that the first parameter is better than a first threshold; wherein the first parameter is a parameter obtained by measurement that characterizes (or indicates) the signal quality between the first terminal device and the second terminal device. Alternatively, the first condition includes: the first parameter that evaluates (or characterizes) the signal quality between the first terminal device and the second terminal device is better than a first threshold. For the first parameter being better than the first threshold, please refer to the relevant description of the second parameter being better than the second threshold.

[0221] The above-mentioned first parameter includes any one of the following: RSSI, RSRP, RSRQ, SINR. For example, when the measured SL-RSRP (corresponding to the first parameter) between the first terminal device and the second terminal device is greater than the first threshold, the first terminal device sends a first message to the second terminal device. The first threshold may include one or more of the first q-RxLevMin, the first minHyst, the first threshHigh, and the first hystMax. For example, the second threshold is the first q-RxLevMin plus the first minHyst. The first threshHigh may be a threshold that triggers the first terminal device to select or reselect a relay device. For example, the air interface signal quality (such as Uu-RSRP) of the first terminal device is less than the threshold first threshHigh, and the first terminal device will be triggered to select or reselect the relayUE. The first q-RxLevMin may be a threshold that triggers the first terminal device to select or reselect a relay device, and the first minHyst is a relative value used to describe the first q-RxLevMin. For example, when the SL-RSRP corresponding to the relay UE currently selected by the first terminal device is lower than the first q-RxLevMin threshold, the first terminal device reselects a relay UE whose corresponding SL-RSRP is higher than (the first q-RxLevMin plus the first minHyst). In actual applications, the first parameter and the first threshold can be set according to actual needs and are not limited in this application.

[0222] The first terminal device sends the first message to the second terminal device based on the second information and the first information. This can be: when the first condition and the second condition are met, the first terminal device sends the first message to the second terminal device; or when the second condition is met, the first terminal device sends the first message to the second terminal device; or when the first condition and the second condition are met, the first terminal device sends the first message to the second terminal device; or when the second condition is met, the first terminal device sends the first message to the second terminal device; or when the first condition is met, the first terminal device sends the first message to the second terminal device, wherein the second condition is also met when the first condition is met; or when it is determined (or judged) that the first condition and the second condition are met, the first terminal device sends the first message to the second terminal device; or when it is determined (or judged) that the second condition is met, the first terminal device sends the first message to the second terminal device.

[0223] When the first and second conditions are met, the first terminal device sends the first message to the second terminal device. This can avoid situations where, after establishing a communication connection with the second terminal device, the communication connection is disconnected within a short period of time, and where a terminal device is frequently or quickly reselected as a relay device. In other words, when the first and second conditions are met, the first terminal device sends the first message to the second terminal device, thereby avoiding the establishment of unnecessary communication connections and reducing the triggering of reselections.

[0224] In one possible implementation, the first condition further includes: the duration from the current moment to the time when the last communication connection (e.g., a unicast connection) was established exceeds a first duration. The time when the last communication connection was established may be the time when the most recent communication connection was established. The time when the most recent communication connection was established may be the time when the first terminal device sent a request to establish a communication connection, or the time when the first terminal device received a message indicating that the other party agreed to establish the communication connection. For example, the time when the most recent communication connection was established may be the time when the first terminal device last sent a direct communication request message. As another example, the time when the most recent communication connection was established may be the time when the first terminal device last received a direct communication accept message. The first duration may be 50ms, 100ms, 200ms, 1s, etc. The first duration may be predefined by the protocol, configured by the network device, or preconfigured by the first terminal device, and is not limited in this application. In actual applications, the first duration may be configured as needed. The first duration may be the duration of a first timer. Upon receiving the direct communication accept message, the first terminal device starts a first timer. If the first timer expires, the first terminal device determines that the duration from the current moment to the time when the most recent communication connection was established exceeds the first duration. The first condition stipulates that the first terminal device can only reselect the relay UE after the time from the current moment (i.e. the moment of selecting or reselecting the relay device) to the moment when the last communication connection (such as a unicast connection) was established exceeds the first time. This can avoid frequent triggering of the relay UE reselection process and causing excessive communication connection establishment overhead, thereby improving communication quality.

[0225] In an embodiment of the present application, the first terminal device sends a first message to the second terminal device based on the second information and the first information, so that the signal quality (for example, SL-RSRP) corresponding to the second terminal device (corresponding to the relayUE) selected / reselected by the first terminal device (corresponding to the remote UE) can meet the threshold requirement of the resident / serving cell of the second terminal device (corresponding to the second condition), which can avoid the first terminal device selecting an inappropriate relay UE, resulting in additional communication connection establishment overhead and frequent triggering of the relay UE reselection process, thereby improving the communication quality of the remote UE.

[0226] Figure 13 A flowchart of another communication method provided in an embodiment of the present application. Figure 13 The method flow is Figure 12 A possible implementation of the method flow in . Figure 13 As shown, the method includes:

[0227] 1301. The first terminal device obtains first configuration information.

[0228] The first configuration information may include a first threshold value. The first terminal device may obtain the first configuration information through a pre-configuration message, an SIB message, a dedicated RRC signaling, or the like. For example, the first terminal device obtains the first configuration information based on an SIB message, a dedicated RRC signaling, or the like from a network device. For another example, the first terminal device obtains the first configuration information based on a message (e.g., a PC5-RRC message, a PC5-S message, etc.) sent by the currently selected / connected relay UE. Step 1301 is optional. The first terminal device may be pre-configured with the first configuration information.

[0229] 1302. The second terminal device obtains second configuration information.

[0230] The second terminal device may obtain the second configuration information through a pre-configuration message, a SIB message, dedicated RRC signaling, or the like. For example, the second terminal device obtains the second configuration information based on an SIB message or dedicated RRC signaling from a network device. In another example, the second terminal device obtains the second configuration information based on a message (e.g., a PC5-RRC message or a PC5-S message) sent by the currently selected / connected relay UE. Step 1302 is optional. The second terminal device may be pre-configured with the second configuration information.

[0231] 1303. The first terminal device receives second information from the second terminal device.

[0232] The second information indicates a second condition for the second terminal device to function as a relay device for the first terminal device. The second condition may include: a second parameter measuring the signal quality between the first terminal device and the second terminal device is greater than a second threshold.

[0233] In one possible implementation, the second configuration information includes the second threshold, and the second information includes the second threshold. The second information is the same as or different from the second configuration information. The second terminal device may obtain the second information based on the second configuration information. For example, the second terminal device obtains the second threshold from the second configuration information and generates the second information including the second threshold.

[0234] In another possible implementation, the second configuration information includes one or more thresholds, and the second information includes the second threshold. The second terminal device may obtain the second threshold based on the one or more thresholds included in the second configuration information. The one or more thresholds included in the second configuration information may include one or more of: a second q-RxLevMin, a second minHyst, a second threshHigh, and a second hystMax. The second threshold may be a threshold derived from the second q-RxLevMin, such as 1.1*second q-RxLevMin, 1.2*second q-RxLevMin, etc. The second threshold may be a threshold derived from the second threshHigh, such as 1.1*second threshHigh, 1.2*second threshHigh, etc. The second threshold may be a threshold derived from the second q-RxLevMin and the second minHyst, such as 1.1*(second q-RxLevMin plus second minHyst), 0.9*(second q-RxLevMin plus second minHyst), etc.

[0235] In one possible implementation, the second information is carried in an announcement message. The announcement message is used to discover the second terminal device. In mode A in which the relay UE and the remote UE discover each other, the relay UE (corresponding to the second terminal device) broadcasts an announcement message to the surrounding area. For example, the message is a PC5-S message. After receiving the message, the remote UE (corresponding to the first terminal device) discovers the relay UE. In this implementation, the second information is carried in the announcement message that the second terminal device broadcasts to the surrounding area, so that the first terminal device can discover the second terminal device according to the received announcement message and obtain the second information. It should be understood that the second information is carried in the announcement message, which can reduce signaling overhead.

[0236] In one possible implementation, the second information is carried in a response message to a solicitation message. The solicitation message is used to discover a relay device. In this implementation, before receiving the second information from the second terminal device, the first terminal device broadcasts a solicitation message to the surrounding area to discover the relay UE (corresponding to the second terminal device). In mode B in which the relay UE and the remote UE discover each other, the remote UE (corresponding to the first terminal device) broadcasts a request (solicitation) message to the surrounding area to discover (or find) the relay UE (corresponding to the second terminal device). After receiving the message, the relay UE may reply with a response (response) message if conditions permit, so that the remote UE can discover the relay UE. In this implementation, the second information is carried in a response message to the solicitation message, so that the first terminal device can discover the second terminal device based on the received solicitation message and obtain the second information. It should be understood that the second information carried in the solicitation message can reduce signaling overhead.

[0237] In a possible implementation, the second message is carried in a message other than the announcement message and the solicitation message. This eliminates the need to modify the existing announcement message and solicitation message, and enhances compatibility.

[0238] 1304. The first terminal device determines to select or reselect the second terminal device as the relay device based on the first information and the second information.

[0239] In one possible implementation, the first information is the same as the first configuration information. In another possible implementation, the first information is different from the first configuration information, and the first terminal device can obtain the first information according to the first configuration information.

[0240] A possible implementation of step 1304 is as follows: when the first condition and the second condition are met, determine to select or reselect the second terminal device as the relay device. The above-mentioned first information indicates the first condition for the above-mentioned first terminal device to select or reselect the above-mentioned second terminal device as the relay device. For example, the first parameter and the second parameter are both SL-RSRP, the first threshold is the first q-RxLevMin plus the first minHyst, and the second threshold is the second q-RxLevMin. The situation where the first condition and the second condition are met may be: the SL-RSRP corresponding to the second terminal device is greater than the first threshold (i.e., the first q-RxLevMin plus the first minHyst), and the SL-RSRP is greater than or greater than or equal to the second q-RxLevMin.

[0241] Step 1304 may be replaced by: the first terminal device determines not to select or reselect the second terminal device as the relay device based on the first information and the second information. In other words, if the first condition or the second condition is not met, the first terminal device is determined not to select or reselect the second terminal device as the relay device.

[0242] 1305. The first terminal device sends a direct communication request message.

[0243] 1306. The first terminal device receives a direct communication acceptance message.

[0244] It should be understood that if step 1304 determines to select or reselect the second terminal device as the relay device, steps 1305 and 1306 are executed; otherwise, the process of selecting or reselecting the relay device is continued.

[0245] In an embodiment of the present application, the first terminal device sends a first message to the second terminal device based on the second information and the first information, so that the signal quality (for example, SL-RSRP) corresponding to the second terminal device (corresponding to the relayUE) selected / reselected by the first terminal device (corresponding to the remote UE) can meet the threshold requirement of the resident / serving cell of the second terminal device (corresponding to the second condition), thereby avoiding the selection of an inappropriate relay UE, resulting in additional communication connection establishment overhead and frequent triggering of the relay UE reselection process.

[0246] Figure 14 A flowchart of another communication method provided in an embodiment of the present application. Figure 14 The method flow is Figure 12 A possible implementation of the method flow in . Figure 14 As shown, the method includes:

[0247] 1401. The first terminal device obtains first configuration information.

[0248] For step 1401 , reference may be made to the relevant description of step 1301 .

[0249] 1402. The second terminal device obtains second configuration information.

[0250] For step 1402 , reference may be made to the relevant description of step 1302 .

[0251] 1403. The first terminal device obtains a second corresponding relationship from the network device.

[0252] The second correspondence includes a correspondence between a second identifier and a second threshold. The above-mentioned second identifier may include an identifier of the second terminal device. The above-mentioned second identifier may include one or more of a cell identifier (cell ID), a public land mobile network identifier (PLMN), a system information area identifier (systemInformationArea ID), and an identifier of the second terminal device corresponding to the second terminal device. The first terminal device obtains the second correspondence from the network device by obtaining the second correspondence from the network device. For example, the first terminal device obtains the second correspondence from the network device by obtaining the second correspondence through one or more of a pre-configuration message, an SIB message, and an RRC dedicated signaling. The first terminal device obtains the second correspondence from the network device by: obtaining a relationship table containing the second correspondence from the network device; or obtaining data for determining the second correspondence, and determining the second correspondence based on the data. For example, the first terminal device obtains a second correspondence table from the network device, and the second correspondence table includes a correspondence between multiple identifiers and multiple thresholds, such as a correspondence between the second identifier and the second threshold.

[0253] Step 1403 is optional and not essential. In one possible implementation, the first terminal device may be pre-configured with the second correspondence, for example, the first terminal device may be pre-configured with the second correspondence when it leaves the factory. For example, the first terminal device may be pre-configured with a second threshold index table, which includes a correspondence between a second identifier and a second threshold. The second identifier may be considered an index corresponding to the second threshold.

[0254] Step 1403 may be replaced by: the first terminal device obtains second correspondence indication information from the network device, and determines the second correspondence according to the second correspondence indication information. The second correspondence indication information is used to indicate the second correspondence.

[0255] 1404. The first terminal device receives second information from the second terminal device.

[0256] In one possible implementation, the second information includes the second identifier. In another possible implementation, the second information is carried in an announcement message. In another possible implementation, the second information is carried in a response message to the solicitation message.

[0257] 1405. The first terminal device determines to select or reselect the second terminal device as the relay device based on the first information and the second information.

[0258] A possible implementation of step 1405 is as follows: the first terminal device determines the second threshold corresponding to the second terminal device based on the second correspondence and the second identifier included in the second information; when the first condition and the second condition are met, determines to select or reselect the second terminal device as the relay device.

[0259] 1406. The first terminal device sends a direct communication request message.

[0260] 1407. The first terminal device receives a direct communication acceptance message.

[0261] Figure 13 In the method process, the second information received by the first terminal device from the second terminal device includes a second threshold. Figure 14 In the method process, the second information received by the first terminal device from the second terminal device includes the second identifier. Figure 14 The method flow and Figure 13 The difference between the method flow in is that the method for the first terminal device to obtain the second threshold is different. Figure 14 The method process can also prevent the first terminal device from selecting an inappropriate relay UE, resulting in additional communication connection establishment overhead and frequent triggering of the relay UE reselection process, and improve the communication quality of the remote UE.

[0262] Figure 14 In the method flow, the first terminal device obtains the second correspondence from the network device. In other words, the first network device to which the first terminal device is connected can send the second correspondence to the first terminal device. The following describes the method flow of the first network device obtaining the second correspondence and sending the second correspondence to the first terminal device in conjunction with the accompanying drawings.

[0263] Figure 15 Another communication method process provided by the embodiment of this application. Figure 15 As shown, the method includes:

[0264] 1501. A first network device receives first indication information from a second network device.

[0265] The first indication information indicates a second condition for the second terminal device accessing the second network device to serve as a relay device for the first terminal device (any terminal device).

[0266] 1502. The first network device sends second indication information to the first terminal device according to the first indication information.

[0267] The second indication information is used to determine the second condition. The second condition may include: a second parameter measuring the signal quality between the second terminal device and the first terminal device is greater than the second threshold. In one possible implementation, the first indication information includes the second threshold. Furthermore, the first indication information may also include a second identifier, where the second identifier corresponds to the second terminal device or the second network device.

[0268] In one possible implementation, the second indication information includes a second correspondence, the second correspondence includes a correspondence between a second identifier and the second threshold, and the second identifier corresponds to the second terminal device or the second network device. The first terminal device may determine the second threshold, i.e., determine the second condition, based on the second correspondence and the second identifier.

[0269] In an embodiment of the present application, the first network device sends second indication information to the first terminal device so that the first terminal device obtains the second condition that the second terminal device serves as a relay device for the first terminal device.

[0270] Figure 16 Another communication method process provided in an embodiment of the present application. Figure 16 The method flow is Figure 15 A possible implementation of the method flow in . Figure 16 As shown, the method includes:

[0271] 1601. A first network device sends a second configuration information request message to a second network device.

[0272] The second configuration information request message is used to obtain a second threshold value corresponding to the second identifier. In one possible implementation, the second identifier is an identifier corresponding to the second terminal device, and the second configuration information request message may include the second identifier. In another possible implementation, the second identifier is an identifier corresponding to the second network device, and the second configuration information request message may not include the second identifier. In some embodiments, the conditions (corresponding to the second condition) for each terminal device (including the second terminal device) accessing the second network device to serve as a relay device for other terminal devices are the same, and the second identifier is the identifier corresponding to the second network device. In some embodiments, the conditions for each terminal device (including the second terminal device) accessing the second network device to serve as a relay device for other terminal devices are different, and the second identifier is the identifier corresponding to the second terminal device.

[0273] 1602. The second network device sends first indication information to the first network device.

[0274] The first indication information may include the second threshold. Optionally, the first indication information further includes a second identifier, and the second identifier and the second threshold have a corresponding relationship. The first indication information may be sent by the second network device in response to the second configuration information request message.

[0275] 1603. The first network device determines a second corresponding relationship according to the first indication information.

[0276] The second corresponding relationship includes a corresponding relationship between the second identifier and the second threshold.

[0277] 1604. The first network device sends a second corresponding relationship to the first terminal device.

[0278] Step 1604 may be replaced by: the first network device sends second correspondence indication information to the first terminal device, so that the first terminal device determines the second correspondence according to the second correspondence indication information. The second correspondence indication information is used to indicate the second correspondence.

[0279] The first network device may send the second correspondence to the first terminal device through one or more of a pre-configuration message, a SIB message, and an RRC dedicated signaling.

[0280] In an embodiment of the present application, the first network device sends the second corresponding relationship to the first terminal device, so that the first terminal device determines the second threshold value using the second corresponding relationship.

[0281] Figure 17 Another communication method process provided in an embodiment of the present application. Figure 17 The method flow is Figure 15 A possible implementation of the method flow in . Figure 17 As shown, the method includes:

[0282] 1701. The second network device sends first indication information to the first network device.

[0283] 1702. The first network device determines a second corresponding relationship according to the first indication information.

[0284] The second corresponding relationship includes a corresponding relationship between the second identifier and the second threshold.

[0285] In one possible implementation, the second identifier is an identifier corresponding to the second terminal device, and the first indication information includes the second identifier. In another possible implementation, the second identifier is an identifier corresponding to the second network device, and the first network device can determine the second identifier based on the first indication information.

[0286] 1703. The first network device sends a second corresponding relationship to the first terminal device.

[0287] Step 1703 may be replaced by: the first network device sends second correspondence indication information to the first terminal device, so that the first terminal device determines the second correspondence according to the second correspondence indication information. The second correspondence indication information is used to indicate the second correspondence.

[0288] In an embodiment of the present application, the first network device sends the second corresponding relationship to the first terminal device, so that the first terminal device determines the second threshold value using the second corresponding relationship.

[0289] Figures 12 to 14 In the method flow, the first terminal device (remote UE) selects or reselects the second terminal device that meets the first condition and the second condition as the relay device. That is, Figures 12 to 14 In the method flow, the first terminal device can ensure that the relay device it selects or reselects satisfies the first condition and the second condition. The following describes a solution for selecting or reselecting a relay UE so that any relay UE discovered by the first terminal device satisfies the first condition and the second condition.

[0290] Figure 18 This is another flow chart of a communication method provided in an embodiment of the present application. Figure 18 As shown, the method includes:

[0291] 1801. The second terminal device obtains the first information.

[0292] One possible implementation of step 1801 is: receiving first information from a first terminal device (an example of a remote UE). Another possible implementation of step 1801 is: the second terminal device obtains preconfigured first information or predefined first information. Another possible implementation of step 1801 is: the second terminal device obtains the first information from another device (e.g., a network device). For example, the second terminal device obtains the first information from the network device to which it is connected.

[0293] The first information indicates a first condition for the first terminal device to select or reselect a terminal device as a relay device. Exemplarily, the first information is carried in a solicitation message for discovering a relay device.

[0294] 1802. The second terminal device sends a second message to the first terminal device based on the first information and the second information.

[0295] The second message is used by the first terminal device to discover the second terminal device. The second information indicates a second condition for the second terminal device to serve as a relay device for the first terminal device. In one possible implementation, the first information is carried in a solicitation message for discovering a relay device, and the second message is a response message to the first information.

[0296] According to the first information and the second information, sending the second message to the first terminal device can be: sending the second message to the first terminal device when the first condition and the second condition are met; sending the second message to the first terminal device when the second condition is met; sending the second message to the first terminal device when the first condition is met; sending the second message to the first terminal device when the first condition and the second condition are met; sending the second message to the first terminal device when the second condition is met; sending the second message to the first terminal device when the first condition is met; sending the first message to the first terminal device when it is determined (or judged) that the first condition and the second condition are met; sending the first message to the second terminal device when it is determined (or judged) that the first condition and the second condition are met; sending the first message to the second terminal device when it is determined (or judged) that the first condition is met; sending the first message to the second terminal device when it is determined (or judged) that the first condition is met; sending the first message to the second terminal device when it is determined (or judged) that the second condition is met.

[0297] Step 1802 can be replaced by: the second terminal device sends a second message to the first terminal device based on the second information. The second terminal device sending the second message to the first terminal device based on the second information can include: sending the second message to the first terminal device if the second condition is met; sending the second message to the first terminal device when the second condition is met; or sending the second message to the first terminal device where the first terminal device meets the second condition. The second terminal device sending the second message to the first terminal device based on the second information can avoid disconnecting the communication connection with the first terminal device within a short period of time after establishing the communication connection.

[0298] Step 1802 can be replaced by: the second terminal device sends a second message to the first terminal device based on the first information. The second terminal device sending the second message to the first terminal device based on the first information can be: sending the second message to the first terminal device if the first condition is met; sending the second message to the first terminal device when the first condition is met; or sending the second message to the first terminal device where the first terminal device meets the first condition. The second terminal device sending the second message to the first terminal device based on the first information can avoid disconnecting the communication connection with the first terminal device within a short period of time after establishing the communication connection.

[0299] In one possible implementation, the first information includes a first threshold or a first identifier, the first identifier corresponds to the first threshold, and the first condition includes: a first parameter measuring the signal quality between the second terminal device and the first terminal device is better than the first threshold; the second condition includes: a second parameter measuring the signal quality between the second terminal device and the first terminal device is better than the second threshold.

[0300] In an embodiment of the present application, the second terminal device sends a second message to the first terminal device based on the first information and the second information, so that when the first terminal device (corresponding to the remote UE) selects / reselects the second terminal device (corresponding to the relayUE) as the relay device, the signal quality (for example, SL-RSRP) corresponding to the second terminal device can meet the threshold requirement of the resident / serving cell of the second terminal device (corresponding to the second condition), thereby avoiding the selection of an inappropriate relay UE, resulting in additional communication connection establishment overhead and frequent triggering of the relay UE reselection process.

[0301] Figure 19 A flowchart of another communication method provided in an embodiment of the present application. Figure 19 The method flow is Figure 18 A possible implementation of the method flow in . Figure 19 As shown, the method includes:

[0302] 1901. The first terminal device obtains first configuration information.

[0303] For step 1901 , please refer to the relevant description of step 1301 .

[0304] 1902. The second terminal device obtains second configuration information.

[0305] For step 1902, reference may be made to the description of step 1302. Both step 1902 and step 1903 are optional.

[0306] 1903. The second terminal device receives the first information from the first terminal device.

[0307] 1904. The second terminal device sends a second message to the first terminal device based on the first information and the second information.

[0308] A possible implementation of step 1904 is as follows: if the first condition and the second condition are met, the second message is sent to the first terminal device. Step 1904 can be replaced by: if the first condition or the second condition is not met, the second message is not sent to the first terminal device.

[0309] 1905. The first terminal device sends a direct communication request message to the second terminal device.

[0310] Exemplarily, after receiving the second message, the first terminal device sends a direct communication request message to the second terminal device.

[0311] 1906. The second terminal device sends a direct communication acceptance message to the first terminal device.

[0312] Exemplarily, after receiving the direct communication request message, the first terminal device sends a direct communication acceptance message to the first terminal device.

[0313] In an embodiment of the present application, the second terminal device sends a second message to the first terminal device based on the first information and the second information, so that when the first terminal device (corresponding to the remote UE) selects / reselects the second terminal device (corresponding to the relayUE) as the relay device, the signal quality corresponding to the second terminal device (for example, SL-RSRP) can meet the threshold requirement of the resident / serving cell of the second terminal device (corresponding to the second condition), which can avoid the selection of an inappropriate relay UE, resulting in additional communication connection establishment overhead and frequent triggering of the relay UE reselection process, thereby improving the communication quality of the remote UE.

[0314] Figure 20 A flowchart of another communication method provided in an embodiment of the present application. Figure 20 The method flow is Figure 18 A possible implementation of the method flow in . Figure 20 As shown, the method includes:

[0315] 2001. A first terminal device obtains first configuration information.

[0316] For step 2001 , please refer to the relevant description of step 1301 .

[0317] 2002. The second terminal device obtains second configuration information.

[0318] For step 2002 , please refer to the relevant description of step 1302 .

[0319] 2003. The second terminal device obtains the first corresponding relationship from the network device.

[0320] The first correspondence includes a correspondence between a first identifier and a first threshold. The above-mentioned first identifier may include an identifier of the first terminal device. The above-mentioned first identifier may include one or more of a cell identifier, a PLMN, a system information area identifier (systemInformationArea ID), and an identifier of the first terminal device corresponding to the first terminal device. The second terminal device obtains the first correspondence from the network device by obtaining the first correspondence from the network device to which the second terminal device accesses. Exemplarily, the second terminal device obtains the first correspondence from the network device by obtaining the first correspondence through one or more of a pre-configuration message, an SIB message, and an RRC dedicated signaling. The second terminal device obtains the first correspondence from the network device by: obtaining a relationship table including the first correspondence from the network device; or obtaining data for determining the first correspondence, and determining the first correspondence based on the data. For example, the second terminal device obtains a first correspondence table from the network device, and the first correspondence table includes correspondences between multiple identifiers and multiple thresholds, such as the correspondence between the first identifier and the first threshold.

[0321] Step 2003 is optional and not essential. In one possible implementation, the second terminal device may be pre-configured with the first correspondence, for example, the second terminal device may be pre-configured with the first correspondence when it leaves the factory. For example, the second terminal device may be pre-configured with a first threshold index table, which includes a correspondence between a first identifier and a first threshold. The first identifier may be considered an index corresponding to the first threshold.

[0322] 2004. The second terminal device receives the first information from the first terminal device.

[0323] The first information may include a first identifier. In a possible implementation, the first information is carried in a solicitation message.

[0324] 2005. The second terminal device sends a second message to the first terminal device based on the first information and the second information.

[0325] A possible implementation of step 2005 is as follows: the second terminal device determines the first threshold corresponding to the first terminal device based on the first corresponding relationship and the first identifier included in the first information; and sends a second message to the first terminal device when the first condition and the second condition are met.

[0326] 2006. The first terminal device sends a direct communication request message to the second terminal device.

[0327] 2007. The second terminal device sends a direct communication acceptance message to the first terminal device.

[0328] Figure 20 The method flow and Figure 19 The difference between the method flow in is that the way of obtaining the first threshold is different. Figure 20 The method process can also prevent the first terminal device from selecting an inappropriate relay UE, resulting in additional communication connection establishment overhead and frequent triggering of the relay UE reselection process, and improve the communication quality of the remote UE.

[0329] Figure 20 In the method flow, the second terminal device obtains the first correspondence from the network device. In other words, the second network device to which the second terminal device is connected can send the first correspondence to the second terminal device. The following describes the method flow of the second network device obtaining the first correspondence and sending the first correspondence to the second terminal device in conjunction with the accompanying drawings.

[0330] Figure 21 Another communication method process provided by the embodiment of this application. Figure 21 As shown, the method includes:

[0331] 2101. The second network device receives third indication information from the first network device.

[0332] The third indication information indicates a first condition for the first terminal device to select or reselect a terminal device as a relay device.

[0333] 2102. The second network device sends fourth indication information to the second terminal device according to the third indication information.

[0334] The fourth indication information is used to determine the first condition. In one possible implementation, the third indication information includes a first threshold, and the first condition includes: a first parameter measuring signal quality between the first terminal device and a terminal device selected or reselected by the first terminal device as a relay device is greater than the first threshold. The third indication information may also include a first identifier, where the first identifier corresponds to the first terminal device or the first network device.

[0335] In a possible implementation, the fourth indication information includes a first correspondence, the first correspondence includes a correspondence between a first identifier and the first threshold, and the first identifier corresponds to the first terminal device or the first network device.

[0336] In the embodiment of the present application, the second network device sends fourth indication information to the second terminal device so that the second terminal device obtains the first condition for the first terminal device to select or reselect a terminal device as a relay device.

[0337] Figure 22 Another communication method process provided in an embodiment of the present application. Figure 22 The method flow is Figure 21 A possible implementation of the method flow in . Figure 22 As shown, the method includes:

[0338] 2201. The second network device sends a first configuration information request message to the first network device.

[0339] The first configuration information request message is used to obtain a first threshold value corresponding to the first identifier. In one possible implementation, the first identifier is an identifier corresponding to the first terminal device, and the first configuration information request message may include the first identifier. In another possible implementation, the first identifier is an identifier corresponding to the first network device, and the first configuration information request message may not include the first identifier. In some embodiments, the conditions (corresponding to the first condition) for each terminal device (including the first terminal device) accessing the first network device to select or reselect a terminal device as a relay device are the same, and the first identifier is the identifier corresponding to the first network device. In some embodiments, the conditions (corresponding to the first condition) for each terminal device (including the first terminal device) accessing the first network device to select or reselect a terminal device as a relay device are different, and the first identifier is the identifier corresponding to the first terminal device.

[0340] 2202. The first network device sends third indication information to the second network device.

[0341] The third indication information may include the first threshold. Optionally, the third indication information further includes a first identifier, and the first identifier and the first threshold have a corresponding relationship.

[0342] 2203. The second network device determines the first corresponding relationship according to the third indication information.

[0343] The first corresponding relationship may include a corresponding relationship between a first identifier and a first threshold.

[0344] 2204. The second network device sends the first corresponding relationship to the second terminal device.

[0345] The second network device may send the first corresponding relationship to the second terminal device through one or more of a pre-configuration message, a SIB message, and an RRC dedicated signaling.

[0346] Step 2204 may be replaced by: the second network device sends first correspondence indication information to the second terminal device, so that the second terminal device determines the first correspondence according to the first correspondence indication information. The first correspondence indication information is used to indicate the first correspondence.

[0347] In an embodiment of the present application, the second network device sends the first corresponding relationship to the second terminal device, so that the second terminal device determines the first threshold value by using the first corresponding relationship.

[0348] Figure 23 Another communication method process provided in an embodiment of the present application. Figure 23 The method flow is Figure 21 A possible implementation of the method flow in . Figure 23 As shown, the method includes:

[0349] 2301. The first network device sends third indication information to the second network device.

[0350] 2302. The second network device determines the first corresponding relationship according to the third indication information.

[0351] 2303. The second network device sends the first corresponding relationship to the second terminal device.

[0352] Step 2303 may be replaced by: the second network device sends first correspondence indication information to the second terminal device, so that the second terminal device determines the first correspondence according to the first correspondence indication information. The first correspondence indication information is used to indicate the first correspondence.

[0353] In an embodiment of the present application, the second network device sends the first corresponding relationship to the second terminal device, so that the second terminal device determines the first threshold value by using the first corresponding relationship.

[0354] Figures 18 to 20 In the method flow, the second terminal device sends a second message to the first terminal device based on the first information and the second information. It should be understood that Figures 12 to 14In the method flow, only the relay UE (such as the second terminal device) that meets the first condition and the second condition will send the second message to the first terminal device so as to be discovered by the first terminal device. Figures 18 to 20 In the method flow, any relay UE discovered by the first terminal device satisfies the first condition and the second condition. The following describes a method flow in which any relay UE discovered by the first terminal device satisfies the second condition.

[0355] Figure 24 This is another flow chart of a communication method provided in an embodiment of the present application. Figure 24 As shown, the method includes:

[0356] 2401. The second terminal device receives a third message from the first terminal device.

[0357] The third message is used to discover the relay device. Exemplarily, the third message is a solicitation message.

[0358] 2402. The second terminal device sends a fourth message to the first terminal device based on the second information.

[0359] The second information indicates a second condition for the second terminal device to act as a relay device for the first terminal device. The second terminal device sending the fourth message to the first terminal device according to the second information may be: sending the fourth message to the first terminal device when the second condition is met.

[0360] In one possible implementation, the third message is a solicitation message broadcast by the first terminal device, and the fourth message is a response message to the third message. The second condition may include: a second parameter measuring the signal quality between the second terminal device and the first terminal device is greater than a second threshold. The fourth message indicates that the second terminal device is a candidate relay device for the first terminal device. In other words, the fourth message indicates that the second terminal device agrees to be discovered by the first terminal device.

[0361] In some embodiments, the conditions for the second terminal device to act as a relay device for different terminal devices may be the same. After receiving the solicitation message broadcast by any terminal device, the second terminal device determines whether the second condition for acting as a relay device for the arbitrary terminal device is satisfied. If so, a response message for the solicitation message is sent to the arbitrary terminal device. If not, no response message is sent to the solicitation message. In some embodiments, the conditions for the second terminal device to act as a relay device for different terminal devices may be different (for example, related to the quality of service requirements of the terminal device). After receiving the solicitation message broadcast by any terminal device, the second terminal device first determines the condition for acting as a relay device for the arbitrary terminal device. Then, it determines whether the condition for acting as a relay device for the arbitrary terminal device is satisfied. If so, a response message for the solicitation message is sent to the arbitrary terminal device. If not, no response message is sent to the solicitation message.

[0362] In one possible implementation, the second terminal device may obtain the second information from the second network device before executing step 2402. For example, the second terminal device may obtain the second information through a pre-configuration message, a SIB message, dedicated RRC signaling, etc. In another possible implementation, the second terminal device may be pre-configured with the second information. In another possible implementation, the second terminal device obtains the second information based on the second configuration information obtained from the network device.

[0363] In an embodiment of the present application, the second terminal device sends a fourth message to the first terminal device based on the second information; so that when the first terminal device (corresponding to the remote UE) selects / reselects the second terminal device (corresponding to the relay UE) as the relay device, the signal quality corresponding to the second terminal device (for example, SL-RSRP) can meet the threshold requirement of the resident / serving cell of the second terminal device (corresponding to the second condition), which can avoid the selection of an inappropriate relay UE, resulting in additional communication connection establishment overhead and frequent triggering of the relay UE reselection process, and improve the communication quality of the remote UE.

[0364] Figure 25 A flowchart of another communication method provided in an embodiment of the present application. Figure 25 The method flow is Figure 24 A possible implementation of the method flow in . Figure 25 As shown, the method includes:

[0365] 2501. The first terminal device obtains first configuration information.

[0366] For step 2501 , please refer to the relevant description of step 1301 .

[0367] 2502. The second terminal device obtains second configuration information.

[0368] For step 2502 , please refer to the relevant description of step 1302 .

[0369] 2503. The first terminal device sends a third message to the second terminal device.

[0370] The third message may be a solicitation message for discovering the relay device, that is, the solicitation message broadcast by the first terminal device.

[0371] 2504. The second terminal device determines whether to reply a response message of the third message to the first terminal device based on the second information.

[0372] In some embodiments, the second terminal device determines to reply a response message of the third message to the first terminal device if the second condition is met; and determines not to reply a response message of the third message to the first terminal device if the second condition is not met.

[0373] 2505. The second terminal device sends a fourth message to the first terminal device.

[0374] The fourth message is a response message (ie, a response message) to the third message (ie, the solicitation message).

[0375] 2506. The first terminal device determines whether to select or reselect the second terminal device as the relay device.

[0376] A possible implementation of step 2506 is as follows: when the first condition is met, the first terminal device determines to select or reselect the second terminal device as the relay device.

[0377] 2507. The first terminal device sends a direct communication request message to the second terminal device.

[0378] 2508. The second terminal device sends a direct communication acceptance message to the first terminal device.

[0379] If the first terminal device determines to select or reselect the second terminal device as the relay device, step 2507 is executed; otherwise, the process of selecting or reselecting the second terminal device as the relay device ends. It should be understood that steps 2507 and 2508 are only executed if the first terminal device determines to select or reselect the second terminal device as the relay device.

[0380] In the embodiment of the present application, the second terminal device sends a fourth message to the first terminal device based on the second information, thereby ensuring that the second terminal device discovered by the first terminal device meets the second condition. Furthermore, the first terminal device determines whether to select or reselect the second terminal device as a relay device, so as to select or reselect the second terminal device that meets the first and second conditions as the relay device. This can avoid selecting an inappropriate relay UE, resulting in additional communication connection establishment overhead and frequent triggering of the relay UE reselection process, and improve the communication quality of the remote UE.

[0381] The main principle of the previously described scheme for selecting or reselecting a relay device is that, when the first and second conditions are met, the first terminal device selects or reselects the second terminal device as the relay device. To prevent the remote UE from frequently triggering the relay UE reselection process, this application also provides a method for ensuring that the remote UE only reselects the relay UE after a certain period of time has passed since the communication connection was established.

[0382] Figure 26 Another communication method process provided by the embodiment of this application. Figure 26 As shown, the method includes:

[0383] 2601. A first terminal device establishes a communication connection with a third terminal device serving as a relay device.

[0384] 2602. When the third condition is met, send a fourth message or receive a fifth message.

[0385] In one possible implementation, the third condition includes: the duration from the current moment of the first terminal device to the moment when the communication connection (i.e., the communication connection established in step 2601) is established exceeds the first duration. The fourth message is used to discover the relay device, and the fifth message is used to discover the relay device. The communication connection established in step 2602 may be the communication connection most recently established by the first terminal device. The duration from the current moment of the first terminal device to the moment when the communication connection is established exceeds the first duration, which may be: the duration from the current moment to the moment when the last communication connection (e.g., a unicast connection) was established exceeds the first duration. The first condition stipulates that the first terminal device can only reselect the relay UE after the duration from the current moment (i.e., the moment of selecting or reselecting the relay device this time) to the moment when the last communication connection (e.g., a unicast connection) was established exceeds the first duration, which can avoid frequent triggering of the relay UE reselection process to cause excessive communication connection establishment overhead, thereby improving communication quality.

[0386] Step 2602 may be replaced by: when the third condition is met, sending the fourth message or receiving the fifth message. Alternatively, step 2602 may be replaced by: sending the fourth message or receiving the fifth message, wherein the first terminal device meets the third condition.

[0387] In a possible implementation, the third condition further includes: the first terminal device is currently waiting to select or reselect a relay device, that is, the first terminal device currently triggers the process of selecting or reselecting a relay device.

[0388] In one possible implementation, the first terminal device may also receive second information from the second terminal device; the second information indicates a second condition for the second terminal device to act as a relay device for the first terminal device; and the third condition also includes: satisfying the second condition.

[0389] In the embodiment of the present application, when the third condition is met, the fourth message is sent or the fifth message is received, so that the remote UE will not reselect the relay UE until a certain period of time has passed after the communication connection is established, which can avoid the remote UE frequently triggering the relay UE reselection process.

[0390] Figure 27 Another communication method process provided in an embodiment of the present application. Figure 27 The method flow is Figure 26 A possible implementation of the method flow in . Figure 27 As shown, the method includes:

[0391] 2701. A first terminal device receives second information from a second terminal device.

[0392] The second information indicates a second condition for the second terminal device to serve as a relay device for the first terminal device. The second information includes a second threshold or a second identifier, and the second identifier corresponds to the second threshold.

[0393] 2702. The first terminal device sends a direct communication request message.

[0394] 2703. The first terminal device receives a direct communication acceptance message.

[0395] Step 2701 is optional. The second information may be carried in an announcement message, a response message to a solicitation message, a direct communication request message, a direct communication accept message, a PC5-RRC or PC5-S message after a unicast connection is established, or the like.

[0396] 2704. The first terminal device determines that the difference between the current moment and the moment when the unicast connection is established is greater than the first duration.

[0397] The first terminal device determining that the difference between the current time and the time when the unicast connection is established is greater than the first duration may be: the duration between the current time and the time when the last communication connection (i.e., the unicast connection) was established exceeds the first duration. The time when the unicast connection is established may be the time when the first terminal device receives the direct communication acceptance message in step 2703.

[0398] 2705. The first terminal device determines to reselect the relay device.

[0399] It can be understood that when the difference between the current moment and the moment when the unicast connection is established is greater than the first duration, the first terminal device determines to reselect the relay device.

[0400] In a possible implementation, the second threshold may be a second q-RxLevMin. The first terminal device determines to reselect the relay device only when the SL-RSRP corresponding to the second terminal device is less than the second q-RxLevMin.

[0401] In one possible implementation, the second threshold may be the second q-RxLevMin multiplied by the first coefficient, and the first terminal device determines to reselect the relay device only when the SL-RSRP corresponding to the second terminal device is less than (the second q-RxLevMin multiplied by the first coefficient). It can be understood that the first coefficient may be sent by the second terminal device (i.e., relayUE) to the first terminal device or may be predefined by the protocol. Furthermore, for the second terminal device to send the first coefficient to the first terminal device, the second terminal device may obtain the first coefficient through the resident / serving cell. Exemplarily, the first coefficient may be 0. Exemplarily, the first coefficient may be 0.5, or expressed as 3dB less than the second q-RxLevMin. Exemplarily, the first coefficient may be 0.25, or expressed as 6dB less than the second q-RxLevMin. Optionally, when the first terminal device determines to reselect the relay device, the first terminal device sends a solicitation message or receives an announcement message.

[0402] In an embodiment of the present application, the first terminal device will only reselect the relay UE when the difference between the current moment and the moment when the unicast connection is established is greater than the first duration, which can avoid the remote frequently triggering the relay UE reselection process.

[0403] The previous section describes a solution for improving the communication quality of the remote UE by preventing the remote UE from frequently triggering the relay UE reselection process. In practice, if the remote UE fails to establish a unicast connection with a relay UE for an extended period of time, the remote UE will remain out of range (OOC) and unable to be paged by the network, affecting the communication quality of the remote UE. Figure 28 A schematic diagram of a remote UE moving from an IC state to an OOC state due to movement is provided in an embodiment of the present application. Figure 28 In the figure, the arrow indicates the direction of movement of the remote UE. The movement of the remote UE may cause the remote UE to change from the IC state to the OOC state. The IC state includes one or more of the RRC connected state, the RRC idle state, and the RRC inactive state.

[0404] The embodiment of the present application also provides a solution that can solve the problem that the remote UE is in the OOC state for a long time and cannot be paged by the network.

[0405] Figure 29 Another communication method process provided by the embodiment of this application. Figure 29 As shown, the method includes:

[0406] 2901. When the fourth condition is met, the first terminal device determines to select a relay device.

[0407] In one possible implementation, the fourth condition includes: the first terminal device is in an OOC state within coverage and the duration of the OOC state reaches a second duration. The second duration can be 100ms, 1s, 5s, etc. The second duration can be pre-configured by the first terminal device or configured by the network device. For example, the network device configures the second duration to the first terminal device through RRC dedicated signaling, SIB message, or pre-configuration message. In some embodiments, for a terminal device that is continuously in an OOC state, the terminal device may perform the following actions: periodically (every second duration) sending the sixth message or receiving the seventh message. In one possible implementation, to prevent the first terminal device from being unable to be paged by the network due to being in OOC for a long time, the first terminal device determines to select a relay device when it is currently in OOC and the duration of the OOC state reaches the second duration. In this implementation, the first terminal device does not need to consider whether the conditions for triggering the selection or reselection of a relay device are met, nor does it need to consider whether there is a need to transmit data with the network. In this implementation, the fourth condition may also include: the first terminal device does not send or receive a message for discovering a relay device within the second duration. That is, when the first terminal device is in the OOC state and has been in the OOC state for a second duration, and has not sent or received a message for discovering a relay device within the second duration, it determines to select a relay device. This can reduce the number of times the first terminal device sends the sixth message or receives the seventh message, saving signaling overhead.

[0408] Step 2901 may be replaced by: when the fourth condition is met, the first terminal device determines to select a relay device. Alternatively, step 2901 may be replaced by: the first terminal device determines to select a relay device, and the first terminal device meets the fourth condition.

[0409] In one possible implementation, the fourth condition includes: the first terminal device is in an OOC state and the first terminal device triggers an event to discover a relay device. The event that triggers the discovery of a relay device includes any of the following: periodic service arrival, paging, RAN-based notification area update (RNAU), and tracking area update (TAU). In this implementation, the network can page the device in a timely manner.

[0410] In one possible implementation, the fourth condition includes: the first terminal device switches from an OOC state to an IC state, i.e., the first terminal device changes from an OOC state to an IC state. In other words, when the first terminal device changes from an OOC state to an IC state, it is determined to select a relay device so as to be paged by the network.

[0411] 2902. The first terminal device sends the sixth message or receives the seventh message.

[0412] The sixth message is used to discover a relay device, and the seventh message is used to discover a relay device. Exemplarily, the sixth message is a solicitation message used to discover a relay device. Exemplarily, the seventh message is an announcement message used to discover a relay device, i.e., an announcement message broadcast by a relay UE.

[0413] In the embodiment of the present application, when the fourth condition is met, sending the sixth message or receiving the seventh message can prevent the first terminal device from being in OOC for a long time and unable to be paged by the network.

[0414] Figure 30 Another communication method process provided in an embodiment of the present application. Figure 30 The method flow is Figure 29 A possible implementation of the method flow in . Figure 30 As shown, the method includes:

[0415] 3001. When the second timer times out or stops, the first terminal device determines to reselect the relay device.

[0416] When the first terminal device changes from the IC state to the OOC state, the second timer is started or restarted; when the first terminal device changes from the OOC state to the IC state, the second timer is stopped.

[0417] 3002. The first terminal device sends a sixth message.

[0418] The sixth message may be a solicitation message for discovering a relay device.

[0419] 3003. The first terminal device receives the seventh message.

[0420] The seventh message may be an announcement message used to discover the relay device.

[0421] Step 3002 and step 3003 are optional. It should be understood that the first terminal device will execute step 3002 or step 3003 only after determining to reselect the relay device.

[0422] It should be understood that the expiration of the second timer indicates that the first terminal device has been in the OOC state for a period of time that has reached or exceeded the second duration. When the second timer expires, the first terminal device determines to reselect the relay device, which can avoid being in the OOC state for a long time and unable to be paged by the network. The expiration of the second timer indicates that the first terminal device has changed from the IC state to the OOC state. The first terminal device determines to reselect the relay device and can access the network in a timely manner.

[0423] Figure 31 A schematic structural diagram of a communication device provided in an embodiment of the present application. Figure 31 The communication device is the first terminal device or is included in the first terminal device. Figure 31 As shown, the communication device 3100 includes:

[0424] The receiving unit 3101 is configured to receive second information from a second terminal device, wherein the second information indicates a second condition for the second terminal device to serve as a relay device for the first terminal device.

[0425] The sending unit 3102 is used to send a first message to the above-mentioned second terminal device based on the above-mentioned second information and the first information; the above-mentioned first message is used to establish a communication connection with the above-mentioned second terminal device, and the above-mentioned first information indicates the first condition for the above-mentioned first terminal device to select or reselect the above-mentioned second terminal device as a relay device.

[0426] Reuse Figure 31 In a possible implementation, the communication device 3100 includes a receiving unit 3101 or a sending unit 3102.

[0427] The receiving unit 3101 or the sending unit 3102 is configured to establish a communication connection with a third terminal device serving as a relay device;

[0428] The sending unit 3102 is configured to send a fourth message when the third condition is met;

[0429] The receiving unit 3101 is used to receive the fifth message when the above-mentioned third condition is met; the above-mentioned third condition includes: the duration from the current moment of the above-mentioned first terminal device to the moment when the above-mentioned communication connection is established exceeds the first duration; the above-mentioned fourth message is used to discover the relay device, and the above-mentioned fifth message is used to discover the relay device.

[0430] For example, the process of establishing a unicast connection between the first terminal device and the second terminal device is as follows: the sending unit 3102 sends a direct communication request message to request to establish a unicast connection with the second terminal device, and the receiving unit 3101 receives a direct communication acceptance message from the second terminal device.

[0431] In a possible implementation, the receiving unit 3101 is further used to receive second information from a second terminal device; the second information indicates a second condition for the second terminal device to act as a relay device for the first terminal device; and the third condition also includes: satisfying the second condition.

[0432] Reuse Figure 31 In a possible implementation, the communication device 3100 includes a receiving unit 3101 or a sending unit 3102.

[0433] The sending unit 3102 is configured to send a sixth message when the fourth condition is met;

[0434] The receiving unit 3101 is used to receive the seventh message when the fourth condition is met; the above-mentioned sixth message is used to discover the relay device, and the above-mentioned seventh message is used to discover the relay device. The above-mentioned fourth condition includes: the above-mentioned first terminal device is in the OOC state within the coverage range and the duration of the OOC state reaches the second duration; or, the above-mentioned fourth condition includes: the above-mentioned first terminal device is in the OOC state and the above-mentioned first terminal device triggers an event of discovering the relay device; or, the above-mentioned first terminal device switches from the OOC state to the IC state.

[0435] Figure 32 A schematic structural diagram of a communication device provided in an embodiment of the present application. Figure 32 The communication device is a second terminal device or is included in the second terminal device. Figure 32 As shown, the communication device 3200 includes: a receiving unit 3201 and a sending unit 3202.

[0436] In one possible implementation, the functions of the units included in the communication device 3200 are as follows:

[0437] The receiving unit 3201 is configured to receive first information from a first terminal device, wherein the first information indicates a first condition for the first terminal device to select or reselect a terminal device as a relay device;

[0438] The sending unit 3202 is used to send a second message to the above-mentioned first terminal device based on the above-mentioned first information and second information; the above-mentioned second message is used by the above-mentioned first terminal device to discover the above-mentioned second terminal device; the above-mentioned second information indicates the second condition of the above-mentioned second terminal device as a relay device of the above-mentioned first terminal device.

[0439] In one possible implementation, the functions of the units included in the communication device 3200 are as follows:

[0440] The receiving unit 3201 is configured to receive a third message from the first terminal device, where the third message is used to discover a relay device.

[0441] The sending unit 3202 is used to send a fourth message to the above-mentioned first terminal device based on the second information; the above-mentioned second information indicates the second condition for the above-mentioned second terminal device to serve as a relay device for the above-mentioned first terminal device, and the above-mentioned fourth message indicates the above-mentioned second terminal device to serve as a candidate relay device for the above-mentioned first terminal device.

[0442] In a possible implementation, the receiving unit 3201 is further configured to receive the second information from the network device.

[0443] Figure 33 A schematic structural diagram of a communication device provided in an embodiment of the present application. Figure 33 The communication device is a first network device or is included in the first network device. Figure 33 As shown, the communication device 3300 includes:

[0444] The receiving unit 3301 is configured to receive first indication information from a second network device; the first indication information indicates a second condition for a second terminal device connected to the second network device to serve as a relay device for the first terminal device.

[0445] The sending unit 3302 is used to send second indication information to the above-mentioned first terminal device; the above-mentioned second indication information is used to determine the above-mentioned second condition.

[0446] Reuse Figure 33 , Figure 33 The communication device is a second network device or is included in the second network device.

[0447] The receiving unit 3301 is configured to receive third indication information from the first network device; the third indication information indicates a first condition for the first terminal device to select or reselect a terminal device as a relay device;

[0448] The sending unit 3302 is used to send fourth indication information to the second terminal device; the above fourth indication information is used to determine the above first condition.

[0449] Figure 34 A schematic diagram of the structure of another communication device provided in an embodiment of the present application. Figure 34 The communication device in the communication device can be the above-mentioned first terminal device, or the second terminal device, or the first network device, or the second network device.

[0450] like Figure 34As shown. The communication device 340 includes at least one processor 3420, which is used to implement the function of the first terminal device in the method provided in the embodiment of the present application; or, to implement the function of the second terminal device in the method provided in the embodiment of the present application; or, to implement the function of the first network device in the method provided in the embodiment of the present application; or, to implement the function of the second network device in the method provided in the embodiment of the present application. The communication device 340 may also include a transceiver 3410. The transceiver 3410 is used to communicate with other devices / devices via a transmission medium. The processor 3420 uses the transceiver 3410 to send and receive data and / or signaling, and is used to implement the method in the above method embodiment.

[0451] Optionally, the communication device 340 may further include at least one memory 3430 for storing program instructions and / or data. The memory 3430 is coupled to the processor 3420. Coupling in the embodiments of the present application is an indirect coupling or communication connection between devices, units, or modules, which may be electrical, mechanical, or other forms, and is used for information exchange between devices, units, or modules. The processor 3420 may operate in conjunction with the memory 3430. The processor 3420 may execute program instructions stored in the memory 3430. At least one of the at least one memory may be included in the processor.

[0452] The specific connection medium between the transceiver 3410, the processor 3420 and the memory 3430 is not limited in the embodiment of the present application. Figure 34 The memory 3430, the processor 3420 and the transceiver 3410 are connected via a bus 3440. Figure 34 The connections between the other components are shown in bold lines, which are only for illustration and not intended to be limiting. The bus can be divided into address bus, data bus, control bus, etc. Figure 34 Only one thick line is used in the diagram, but this does not mean that there is only one bus or one type of bus.

[0453] In the embodiments of the present application, the processor may be a general-purpose processor, a digital signal processor, an application-specific integrated circuit, a field programmable gate array or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component, and may implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of the present application. A general-purpose processor may be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of the present application may be directly implemented as being executed by a hardware processor, or may be executed by a combination of hardware and software modules in the processor.

[0454] It is understood that when the communication device 340 is a first terminal device, the transceiver 3410 implements the functions of the receiving unit 3101 and the sending unit 3102. Alternatively, when the communication device 340 is a second terminal device, the transceiver 3410 implements the functions of the receiving unit 3201 and the sending unit 3202. Alternatively, when the communication device 340 is a first network device, the transceiver 3410 implements the functions of the receiving unit 3301 and the sending unit 3302. Alternatively, when the communication device 340 is a second network device, the transceiver 3410 implements the functions of the receiving unit 3301 and the sending unit 3302.

[0455] Figure 35 A schematic structural diagram of another communication device 350 provided in an embodiment of the present application. Figure 35 The communication device in the embodiment may be the first terminal device, the second terminal device, the first network device, or the second network device. Figure 35 As shown, Figure 35 The communication device shown includes a logic circuit 3501 and an interface 3502. The logic circuit 3501 can be a chip, a processing circuit, an integrated circuit or a system on chip (SoC) chip, etc., and the interface 3502 can be a communication interface, an input / output interface, etc. The interface 3502 is used to implement the sending and receiving of data or signaling. In the embodiment of the present application, the logic circuit and the interface can also be coupled to each other. The embodiment of the present application does not limit the specific connection method of the logic circuit and the interface. In some embodiments of the present application, the logic circuit and the interface can be used to perform the functions or operations performed by the above-mentioned communication device.

[0456] The present application also provides a computer-readable storage medium, in which computer code is stored. When the computer code is run on a computer, the computer executes the method of the above embodiment.

[0457] The present application also provides a computer program product, which includes computer code or computer program. When the computer code or computer program runs on a computer, the method in the above embodiment is executed.

[0458] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the above claims.

Claims

1. A communication method, characterized in that: Applied to a first terminal device, the method includes: receiving second information from a second terminal device; wherein the second information indicates a second condition for the second terminal device to serve as a relay device for the first terminal device; Based on the second information and the first information, a first message is sent to the second terminal device; the first message is used to establish a communication connection with the second terminal device, and the first information indicates a first condition for the first terminal device to select or reselect the second terminal device as a relay device.

2. The method according to claim 1, characterized in that The second information includes a second threshold or a second identifier, the second identifier corresponds to the second threshold, and the second condition includes: a second parameter measuring the signal quality between the first terminal device and the second terminal device is better than the second threshold; the first condition includes: a first parameter measuring the signal quality between the first terminal device and the second terminal device is better than the first threshold.

3. The method according to claim 2, characterized in that The second information includes the second identifier; and the method further includes: A second corresponding relationship is acquired, where the second corresponding relationship includes a corresponding relationship between the second identifier and the second threshold.

4. The method according to claim 2 or 3, characterized in that The second parameter or the first parameter includes any one of the following: received signal strength indicator RSSI, reference signal received power RSRP, reference signal received quality RSRQ, and signal to interference plus noise ratio SINR.

5. The method according to claim 2 or 3, characterized in that The first condition also includes: the duration from the current moment to the moment when the last communication connection was established exceeds a first duration.

6. The method according to claim 2 or 3, characterized in that The second information is carried in an announcement message or in a response message to a request message, the request message is used to discover a relay device, and the announcement message is used to discover a relay device.

7. A communication method, characterized in that: Applied to a second terminal device, the method includes: receiving first information from a first terminal device; the first information indicating a first condition for the first terminal device to select or reselect a terminal device as a relay device; Based on the first information and the second information, a second message is sent to the first terminal device; the second message is used by the first terminal device to discover the second terminal device; the second information indicates a second condition for the second terminal device to act as a relay device for the first terminal device.

8. The method according to claim 7, characterized in that The first information includes a first threshold or a first identifier, the first identifier corresponds to the first threshold, and the first condition includes: a first parameter measuring the signal quality between the second terminal device and the first terminal device is better than the first threshold; the second condition includes: a second parameter measuring the signal quality between the second terminal device and the first terminal device is better than the second threshold.

9. The method according to claim 8, characterized in that The first information includes the first identifier; and the method further includes: A first corresponding relationship is acquired, where the first corresponding relationship includes a corresponding relationship between the first identifier and the first threshold.

10. The method according to claim 8 or 9, characterized in that The second parameter or the first parameter includes any one of the following: received signal strength indicator RSSI, reference signal received power RSRP, reference signal received quality RSRQ, and signal to interference plus noise ratio SINR.

11. The method according to claim 10, characterized in that The first information is used to discover the relay device.

12. The method according to claim 11, characterized in that The first information is carried in an announcement message, and the second message is a response message to the first information.

13. A communication method, characterized in that: Applied to a second terminal device, the method includes: receiving a third message from the first terminal device, where the third message is used to discover the relay device; According to the second information, a fourth message is sent to the first terminal device; the second information indicates the second condition for the second terminal device to serve as a relay device for the first terminal device, and the fourth message indicates the second terminal device to serve as a candidate relay device for the first terminal device.

14. The method according to claim 13, wherein: The second condition includes: a second parameter measuring the signal quality between the second terminal device and the first terminal device is better than a second threshold.

15. The method according to claim 14, characterized in that The second parameter includes any one of the following: received signal strength indicator RSSI, reference signal received power RSRP, reference signal received quality RSRQ, and signal to interference plus noise ratio SINR.

16. The method according to any one of claims 13 to 15, characterized in that The third message is a solicitation message, and the fourth message is a response message to the third message.

17. The method according to any one of claims 13 to 15, characterized in that The method further comprises: The second information is received from the network device.

18. A communication method, characterized in that: Applied to a first terminal device, the method includes: Establishing a communication connection with a third terminal device serving as a relay device; When the third condition is met, a fourth message is sent or a fifth message is received; the third condition includes: the duration from the current moment of the first terminal device to the moment when the communication connection is established exceeds the first duration; the fourth message is used to discover a relay device, and the fifth message is used to discover a relay device.

19. The method according to claim 18, characterized in that The method further comprises: Receive second information from a second terminal device; the second information indicates a second condition for the second terminal device to serve as a relay device for the first terminal device; the third condition also includes: satisfying the second condition.

20. The method according to claim 19, characterized in that The second information includes a second threshold or a second identifier, the second identifier corresponds to the second threshold, and the second condition includes: a second parameter measuring the signal quality between the first terminal device and the second terminal device is better than the second threshold.

21. A communication method, characterized in that: Applied to a first terminal device, the method includes: If the fourth condition is met, the sixth message is sent or the seventh message is received; the sixth message is used to discover the relay device, and the seventh message is used to discover the relay device. The fourth condition includes: the first terminal device is in the OOC state within the coverage range and the time duration in the OOC state reaches a second time duration, and the first terminal device does not send or receive a message for discovering the relay device within the second time duration; or, the fourth condition includes: the first terminal device is in the OOC state and the first terminal device triggers an event to discover the relay device; or, the first terminal device switches from the OOC state to the IC state.

22. The method according to claim 21, characterized in that The sixth message is a request message, and the seventh message is an announcement message.

23. The method according to claim 21 or 22, characterized in that The event triggering the discovery of the relay device includes any one of the following: arrival of periodic services, paging, area notification update RNAU based on the radio access network RAN, and tracking area update TAU.

24. The method according to claim 21 or 22, characterized in that The method further comprises: When the first terminal device detects that the IC state is converted from being in coverage to being in the OOC state, the timer is started or restarted; the time when the first terminal device is in the OOC state exceeds the second time, including the timer timing out.

25. A communication method, characterized in that: Applied to a first network device, the method includes: receiving first indication information from a second network device; wherein the first indication information indicates a second condition under which a second terminal device connected to the second network device serves as a relay device for the first terminal device; Send second indication information to the first terminal device; the second indication information is used to determine the second condition.

26. The method according to claim 25, characterized in that The first indication information includes a second threshold, and the second condition includes: a second parameter measuring the signal quality between the second terminal device and the first terminal device is better than the second threshold.

27. The method according to claim 26, characterized in that The second indication information includes a second corresponding relationship, the second corresponding relationship includes a corresponding relationship between a second identifier and the second threshold, and the second identifier corresponds to the second terminal device or the second network device.

28. The method according to claim 26 or 27, characterized in that The first indication information further includes a second identifier, and the second identifier corresponds to the second terminal device or the second network device.

29. A communication method, characterized in that: Applied to the second network device, the method includes: receiving third indication information from the first network device; the third indication information indicating a first condition for the first terminal device to select or reselect a terminal device as a relay device; Send fourth indication information to the second terminal device; the fourth indication information is used to determine the first condition.

30. The method according to claim 29, wherein The third indication information includes a first threshold, and the first condition includes: a first parameter measuring the signal quality between the first terminal device and the terminal device selected or reselected as the relay device by the first terminal device is better than the first threshold.

31. The method according to claim 30, wherein The fourth indication information includes a first corresponding relationship, the first corresponding relationship includes a corresponding relationship between a first identifier and the first threshold, and the first identifier corresponds to the first terminal device or the first network device.

32. The method according to claim 30 or 31, characterized in that The third indication information further includes a first identifier, and the first identifier corresponds to the first terminal device or the first network device.

33. A communication device, characterized in that: include: processors and transceivers; The transceiver is used to receive a signal or send a signal; the processor is used to execute the computer-executable instructions stored in the memory, so that the communication device performs the method according to any one of claims 1 to 32.

34. A communication device, characterized in that: The method comprises a unit for implementing the method according to any one of claims 1 to 32.

35. A computer-readable storage medium, characterized in that The computer-readable storage medium is used to store a computer program, which enables the method according to any one of claims 1 to 32 to be implemented when the computer-readable storage medium is run on a computer.

36. A computer program product, characterized in that The computer program product comprises a computer program or a computer code, which enables the method according to any one of claims 1 to 32 to be implemented when the computer program product is run on a processor.

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