Communication method and communication device

Abstract

This application provides a communication method, a communication device, and a communication system. The communication method is applied to a first relay device. The communication method includes receiving, by the first relay device, a first request message from a source terminal device, and when the transmission quality determined based on the first request message, which is of the first relay device, meets a first condition and / or when the capability of the first relay device meets a condition related to service quality, sending, based on the first request message, a second request message to a target terminal device. Both the first request message and the second request message are used to request discovery of the target terminal device, and the first request message and the second request message each include an identifier of the source terminal device and an identifier of the target terminal device. In addition, the second request message further includes an identifier of the first relay device. In this way, a first relay device that meets the requirements helps the source terminal device continue to discover the target terminal device in order to guarantee the reliability of subsequent communication between the source terminal device and the target terminal device via the first relay device.

Description

Technical Field

[0001] This application claims priority to Chinese Patent Application No. 202210932823.2, titled "COMMUNICATION METHOD AND COMMUNICATION APPARATUS", filed with the China National Intellectual Property Administration on August 4, 2022, which is hereby incorporated by reference in its entirety.

[0002] Embodiments of the present application relate to the field of communication technologies, and more specifically, to communication methods and communication apparatuses.

Background Art

[0003] To improve the coverage or capacity of sidelink (SL), user equipment (UE)-to-UE relay technology, that is, the technology in which a source terminal device communicates with a target terminal device via a relay terminal device, can be used.

[0004] In the UE to UE relay scenario, there may be multiple relay terminal devices between a source terminal device and a target terminal device having unicast communication requirements. In this case, one relay terminal device among the multiple relay terminal devices needs to be selected as the relay device for unicast communication between the source terminal device and the target terminal device, that is, a unicast communication path between the source terminal device and the target terminal device needs to be selected. Therefore, how to select an appropriate relay terminal device from among the multiple relay terminal devices is important for the reliability of unicast communication between the source terminal device and the target terminal device.

Summary of the Invention

[0005] Embodiments of the present application provide a communication method and a communication device. The communication method can guarantee the reliability of unicast communication between a source terminal device and a target terminal device.

Means for Solving the Problem

[0006] According to a first aspect, a communication method is provided. The communication method may be executed by a first relay device, or may be executed by a chip or circuit of the first relay device. This is not limited in the present application. For ease of explanation, an example where the method is executed by a first relay device is used in the following description.

[0007] The communication method includes a step in which a first relay device receives a first request message from a source terminal device. The first request message is used to request discovery of a target terminal device, and the first request message includes an identifier of the source terminal device and an identifier of the target terminal device. When the transmission quality of the first relay device meets a first condition and / or when the capability of the first relay device meets a second condition, the first relay device transmits a second request message to the target terminal device based on the first request message. The transmission quality of the first relay device is determined based on the first request message. The second condition includes a condition related to quality of service QoS. The second request message is used to request discovery of a target terminal device, and the second request message includes an identifier of the source terminal device, an identifier of the target terminal device, and an identifier of the first relay device.

[0008] In this embodiment of the present application, only when the transmission quality of the first relay device meets the conditions and / or the capabilities of the first relay device meet the conditions related to the quality of service QoS, the first relay terminal device transmits a request message requesting the discovery of the target terminal device to the target terminal device. In other words, the transmission quality of the first relay device and / or the QoS that can be provided by the first relay device meet the corresponding requirements, and the first relay device helps ensure the reliability of subsequent communication between the source terminal device and the target terminal device via the first relay device by allowing the source terminal device to continue discovering the target terminal device.

[0009] In a possible implementation, the first relay device's transmission quality meeting the first condition includes the first relay device's transmission quality being equal to or greater than a first threshold, or the first relay device's transmission quality being equal to or greater than a first threshold and the first relay device's transmission quality being equal to or less than a second threshold. The second threshold is greater than the first threshold.

[0010] When the transmission quality of the first relay device is equal to or greater than the first threshold, the first relay device helps ensure that the source terminal device continues to discover the target terminal device. In this way, it can be guaranteed that the transmission quality between the first relay device and the source terminal device can meet the corresponding requirements.

[0011] When the transmission quality of the first relay device is equal to or greater than the first threshold, the first relay device's transmission quality is equal to or less than a second threshold, and the second threshold is greater than the first threshold, the first relay device helps ensure that the source terminal device continues to discover the target terminal device. In this way, it can be guaranteed that the transmission quality between the first relay device and the source terminal device can meet the corresponding requirements, and it is also possible to avoid the situation where there is no gain because the first relay device is overly closed to the source terminal device.

[0012] In one possible implementation, the first request message includes the first quality of service (QoS) requirement of the source terminal device regarding the source terminal device and the target terminal device.

[0013] In one possible implementation, the first relay device's ability to meet the second condition includes the first relay device's ability to meet the first QoS requirement.

[0014] When the first relay device's ability meets the first QoS requirement, the first relay device helps the source terminal device continue to discover the target terminal device. In this way, it can be guaranteed that the first relay device is suitable to function as a relay device between the source terminal device and the target terminal device.

[0015] In one possible implementation, the communication method further includes the step of the first relay device receiving a first response message to the second request message from the target terminal device. The first relay device transmits a second response message to the source terminal device for the first request message. The second response message includes the identifier of the first relay device and / or the identifier of the target terminal device.

[0016] In one possible implementation, the step of the first relay device transmitting a second response message to the source terminal device for the first request message includes the step of the first relay device determining whether to transmit the second response message to the source terminal device based on the first reference information and / or the second reference information. The first reference information includes the transmission quality of the first response message. The second reference information includes whether a unicast connection is established between the first relay device and the source terminal device.

[0017] In one possible implementation, for the first relay device to determine whether to send the second response message to the source terminal device based on the first reference information, when the transmission quality of the first response message is greater than or equal to a third threshold, the first relay device determines to send the second response message to the source terminal device; or when the transmission quality of the first response message is greater than or equal to the third threshold and the transmission quality of the first response message is less than or equal to a fourth threshold, the first relay device determines to send the second response message to the source terminal device. The fourth threshold is greater than the third threshold.

[0018] When the transmission quality of the first response message is greater than or equal to the third threshold, the first relay device determines to send the second response message to the source terminal device. In this way, it can be guaranteed that the transmission quality between the first relay device and the source terminal device can meet the corresponding requirements. Thereby, the reliability of subsequent communication between the source terminal device and the source terminal device via the first relay device is further guaranteed.

[0019] When the transmission quality of the first response message is greater than or equal to the third threshold and the transmission quality of the first response message is less than or equal to the fourth threshold, the first relay device determines to send the second response message to the source terminal device. The fourth threshold is greater than the third threshold. In this way, it can be guaranteed that the transmission quality between the first relay device and the source terminal device can meet the corresponding requirements, and it can also avoid the situation where there is no gain because the first relay device is overly closed to the source terminal device. Thereby, the reliability of subsequent communication between the source terminal device and the source terminal device via the first relay device is further guaranteed.

[0020] In a possible implementation form, for the first relay device to determine whether to send a second response message to the source terminal device based on the second reference information includes that when a unicast connection is established between the first relay device and the source terminal device, the first relay device determines to send the second response message to the source terminal device.

[0021] When a unicast connection is established between the first relay device and the source terminal device, the first relay device determines to send the second response message to the source terminal device. In this way, the existing unicast connection between the first relay device and the source terminal device can be multiplexed, thereby shortening the time for establishing a link between the first relay device and the source terminal device and shortening the time for establishing a link between the source terminal device and the target terminal device.

[0022] In a possible implementation form, after the first relay device sends the second response message to the source terminal device, the communication method further includes the step that the first relay device receives a third request message from the source terminal device. The third request message is used to request to establish a first unicast connection, the third request message includes the second QoS requirement of the source terminal device regarding the first relay device and the target terminal device, and the first unicast connection is a connection between the source terminal device and the first relay device. When the capability of the first relay device meets the second QoS requirement, the first relay device establishes the first unicast connection to the source terminal device; or when the capability of the first relay device does not meet the second QoS requirement, the first relay device skips establishing the first unicast connection to the source terminal device.

[0023] If the capabilities of the first relay device meet the second QoS requirements of the source terminal device regarding the first relay device and the target terminal device, the first relay device establishes a unicast connection with the source terminal device. In this way, it can be ensured that the first relay device is suitable for functioning as a relay device between the source terminal device and the target terminal device.

[0024] In a possible implementation form, after the first relay device establishes a first unicast connection to the source terminal device, the communication method further includes the step of the first relay device sending a fourth request message to the target terminal device. The fourth request message is used to request the establishment of a second unicast connection, and the second unicast connection is a connection between the target terminal device and the first relay device. The first relay device receives a third response message from the target terminal device. The third response message includes the third QoS requirements of the target terminal device regarding the first relay device and the source terminal device. If the capabilities of the first relay device meet the third QoS requirements, the first relay device establishes a second unicast connection to the target terminal device; or, if the capabilities of the first relay device do not meet the third QoS requirements, the first relay device skips the establishment of the second unicast connection to the target terminal device.

[0025] The first relay device establishes a unicast connection with the target terminal device only when the capabilities of the first relay device meet the third QoS requirements of the target terminal device regarding the first relay device and the source terminal device. In this way, it can be ensured that the first relay device is suitable for functioning as a relay device between the source terminal device and the target terminal device.

[0026] In one possible implementation, when a first link is established between a source terminal device and a target terminal device, and the transmission quality of the second link and / or the third link does not meet the quality transmission conditions, or the second link and / or the third link is interrupted, the first request message is used to request the discovery of the target terminal device, which includes that the first request message is used to request the rediscovery of the target terminal device. The second link is a link between the second relay device and the target terminal device, and the third link is a link between the second relay device and the source terminal device.

[0027] According to a second aspect, a communication method is provided. The communication method may be executed by a target terminal device, or may be executed by a chip or a circuit of the target terminal device. This is not limited in the present application. For the sake of easy explanation, an example in which the method is executed by a target terminal device is used in the following description.

[0028] The communication method includes steps in which a target terminal device receives a first message from each of a plurality of first terminal devices. The first message is used to request discovery of the target terminal device, and the first message includes an identifier of the first terminal device and an identifier of the target terminal device. The target terminal device determines at least one second terminal device among the plurality of first terminal devices based on first information, second information, and / or third information. The target terminal device sends a second message to the at least one second terminal device. The second message indicates that the target terminal device has been discovered, and the second message includes an identifier of the target terminal device. The first information indicates a direct or indirect path between the first terminal device and the target terminal device and the transmission quality between the first terminal device and the target terminal device. The transmission quality between the first terminal device and the target terminal device is determined based on the first message. The second information indicates whether a unicast connection has been established between the first terminal device and the target terminal device. The third information indicates first quality of service QoS requirements of the source terminal device with respect to the source terminal device and the target terminal device.

[0029] In this embodiment of the present application, the target terminal device selects the second terminal device from the plurality of first terminal devices based on the direct or indirect path between the first terminal device and the target terminal device, whether a unicast connection has been established, and / or the first QoS requirements of the source terminal device with respect to the source terminal device and the target terminal device to ensure that the second terminal device is properly selected. Thereby, the reliability of subsequent communication between the second terminal device and the target terminal device is further ensured.

[0030] In one possible implementation, for the target terminal device to determine a plurality of second terminal devices among a plurality of first terminal devices based on the first information and the second information includes the target terminal device determining, based on the first information, whether there is a first terminal device among the plurality of first terminal devices that satisfies a third condition. When there is a first terminal device among the plurality of first terminal devices that satisfies the third condition, the target terminal device determines the first terminal device that satisfies the third condition as the second terminal device; or when there is no first terminal device among the plurality of first terminal devices that satisfies the third condition, the target terminal device determines, based on the second information, whether there is a first terminal device among the plurality of first terminal devices that satisfies a fourth condition. The third condition includes that there is a direct path between the first terminal device and the target terminal device and the transmission quality between the first terminal device and the target terminal device is equal to or higher than a fifth threshold. The fourth condition includes that a unicast connection is established between the first terminal device and the target terminal device.

[0031] The target terminal device preferentially selects a first terminal device having a direct path to the target terminal device as the second terminal device, and the transmission quality of the direct path meets the corresponding requirements. In this way, the transmission quality between the target terminal device and the second terminal device can be guaranteed. In addition, the communication delay between the target terminal device and the second terminal device can be further reduced. Thereby, the reliability of subsequent communication between the target terminal device and the second terminal device (an example of the source terminal device) is further guaranteed. Next, when the target terminal device does not select a second terminal device that meets the fourth condition, the target terminal device selects a first terminal device that establishes a unicast connection with the target terminal device as the second terminal device. In this way, the existing unicast connection between the second terminal device and the target terminal device can be multiplexed, thereby shortening the time for establishing a link between the second terminal device and the target terminal device.

[0032] In a possible implementation, for the target terminal device to determine whether there is a first terminal device that meets the fourth condition among a plurality of first terminal devices based on the fourth information, when there is a first terminal device that meets the fourth condition among the plurality of first terminal devices, the target terminal device determines the first terminal device that meets the fourth condition as the second terminal device; or when there is no first terminal device that meets the fourth condition among the plurality of first terminal devices, the target terminal device determines the second terminal device among the plurality of first terminal devices based on the fourth information. The fourth information includes the transmission quality between the first terminal device and the target terminal device.

[0033] In one possible implementation, for the target terminal device to determine the second terminal device among the plurality of first terminal devices based on the fourth information includes the target terminal device determining whether there is a first terminal device that meets the fifth condition among the plurality of first terminal devices based on the fourth information. When there is a first terminal device that meets the fifth condition among the plurality of first terminal devices, the target terminal device determines the first terminal device that meets the fifth condition as the second terminal device; or when there is no first terminal device that meets the fifth condition among the plurality of first terminal devices, the target terminal device determines the first terminal device having a direct path to the target terminal device among the plurality of first terminal devices as the second terminal device. The fifth condition includes that there is an indirect path between the first terminal device and the target terminal device and the transmission quality between the first terminal device and the target terminal device is equal to or higher than a sixth threshold; or the fifth condition includes that there is an indirect path between the first terminal device and the target terminal device and both the transmission quality between the first terminal device and the target terminal device and the transmission quality between the first terminal device and the source terminal device are greater than a seventh threshold.

[0034] If the target terminal device does not select a first terminal device that meets the third and fourth conditions, the target terminal device may select the first terminal device from the indirect path as the second terminal device, provided that the transmission quality between the first terminal device and the target terminal device meets the corresponding requirements, or both the transmission quality between the first terminal device and the target terminal device and the transmission quality between the first terminal device and the source terminal device meet the corresponding requirements. In this way, the transmission quality between the target terminal device and the second terminal device can be guaranteed, thereby ensuring the reliability of subsequent communication between the source terminal device and the second terminal device.

[0035] If the target terminal device does not select a first terminal device that satisfies the third condition, the fourth condition, and the fifth condition, the target terminal device may directly determine, as the second terminal device, a first terminal device that has a direct path to the target terminal device. In this way, the communication delay between the target terminal device and the second terminal device can be reduced.

[0036] In a possible implementation form, the first message includes the transmission quality between the first terminal device and the source terminal device.

[0037] In a possible implementation form, when multiple second terminal devices are determined, this communication method further includes a step in which the target terminal device determines a third terminal device among the multiple second terminal devices and uses the third terminal device as the final second terminal device. The third terminal device is the terminal device with the highest transmission quality with the target terminal device among the multiple second terminal devices; or the third terminal device is the terminal device with the highest transmission quality with both the target terminal device and the source terminal device among the multiple second terminal devices.

[0038] In a possible implementation form, for the target terminal device to determine multiple second terminal devices among the multiple first terminal devices based on the second information includes the target terminal device determining, as the second terminal device, a first terminal device that has established a unicast connection with the target terminal device among the multiple first terminal devices.

[0039] The target terminal device preferentially selects, as the second terminal device, the first terminal device that establishes a unicast connection with the target terminal device. In this way, the existing unicast connection between the second terminal device and the target terminal device can be multiplexed, thereby shortening the time for establishing a link between the second terminal device and the target terminal device and shortening the time for establishing a link between the source terminal device and the target terminal device.

[0040] In a possible implementation form, the target terminal device determining, as the second terminal device, the first terminal device that has established a unicast connection with the target terminal device among a plurality of first terminal devices includes the target terminal device determining, as the second terminal device, the first terminal device that has established a unicast connection with the target terminal device among a plurality of first terminal devices and whose transmission quality with the target terminal device is equal to or higher than an eighth threshold.

[0041] The target terminal device preferentially selects, as the second terminal device, the first terminal device that has established a unicast connection with the target terminal device and whose transmission quality with the target terminal device is equal to or higher than an eighth threshold. In this way, the existing unicast connection between the second terminal device and the target terminal device can be multiplexed, thereby shortening the time for establishing a link between the second terminal device and the target terminal device and shortening the time for establishing a link between the source terminal device and the target terminal device. Thereby, the reliability of subsequent communication between the second terminal device and the target terminal device can be further guaranteed.

[0042] In a possible implementation form, the target terminal device determining a plurality of second terminal devices among a plurality of first terminal devices based on third information includes the target terminal device determining, as the second terminal device, the first terminal device that meets a first QoS requirement among a plurality of first terminal devices.

[0043] In one possible implementation, the first message includes a first QoS requirement.

[0044] According to a third aspect, a communication method is provided. The communication method may be executed by a source terminal device or may be executed by a chip or a circuit of the source terminal device. This is not limited in the present application. For ease of explanation, an example in which the method is executed by a source terminal device is used in the following description.

[0045] The communication method includes a step in which a source terminal device transmits a first request message. The first request message is used to request to discover a target terminal device, and the first request message includes an identifier of the source terminal device and an identifier of the target terminal device. The source terminal device receives a third message from each of a plurality of second terminal devices. The third message indicates that the target terminal device has been discovered, and the third message includes an identifier of the second terminal device or the third message includes an identifier of the second terminal device and an identifier of the target terminal device. The source terminal device determines a fourth terminal device among the plurality of second terminal devices based on sixth information and / or seventh information. The source terminal device establishes a unicast connection with the target terminal device via the fourth terminal device. The sixth information indicates a direct path or an indirect path between the second terminal device and the source terminal device and a transmission quality between the second terminal device and the source terminal device. The transmission quality between the second terminal device and the source terminal device is determined based on the third message. The seventh information indicates whether a unicast connection has been established between the second terminal device and the source terminal device.

[0046] In this embodiment of the present application, the source terminal device selects a fourth terminal device from a plurality of second terminal devices based on whether a direct path or an indirect path and / or a unicast connection is established between the second terminal device and the source terminal device. Thereby, it can be guaranteed that the fourth terminal device is appropriately selected. Thereby, the reliability of subsequent communication between the fourth terminal device and the source terminal device is further guaranteed.

[0047] In a possible implementation form, for the source terminal device to determine a fourth terminal device among a plurality of second terminal devices based on the sixth information and the seventh information includes the source terminal device determining, based on the sixth information, whether there is a fourth terminal device that meets the sixth condition among the plurality of second terminal devices. When there are a plurality of second terminal devices that meet the sixth condition, the source terminal device determines the second terminal device that meets the sixth condition as the fourth terminal device; or when there is no second terminal device that meets the sixth condition among the plurality of second terminal devices, the source terminal device determines, based on the seventh information, whether there is a second terminal device that meets the seventh condition among the plurality of second terminal devices. The sixth condition includes that there is a direct path between the second terminal device and the source terminal device, and the transmission quality between the second terminal device and the source terminal device is equal to or higher than a ninth threshold. The seventh condition includes that a unicast connection is established between the second terminal device and the source terminal device.

[0048] The source terminal device preferentially selects a second terminal device having a direct path to the source terminal device as the fourth terminal device, and the transmission quality of the direct path meets the corresponding requirements. In this way, the transmission quality between the source terminal device and the fourth terminal device can be guaranteed. In addition, the communication delay between the source terminal device and the fourth terminal device can be further reduced. Thereby, the reliability of subsequent communication between the source terminal device and the fourth terminal device (an example of the target terminal device) is further guaranteed. Next, when the source terminal device does not select a second terminal device that meets the sixth condition, the source terminal device selects a second terminal device that establishes a unicast connection with the source terminal device as the fourth terminal device. In this way, the existing unicast connection between the fourth terminal device and the source terminal device can be multiplexed, thereby shortening the time for establishing a link between the fourth terminal device and the source terminal device.

[0049] In a possible implementation form, for the source terminal device to determine whether there is a second terminal device that meets the seventh condition among a plurality of second terminal devices based on the seventh information includes: when there is a second terminal device that meets the seventh condition among the plurality of second terminal devices, the source terminal device determines the second terminal device that meets the seventh condition as the fourth terminal device; or when there is no second terminal device that meets the seventh condition among the plurality of second terminal devices, the source terminal device determines the fourth terminal device among the plurality of second terminal devices based on the eighth information. The eighth information includes the transmission quality between the second terminal device and the source terminal device; or the eighth information includes the transmission quality between the second terminal device and the target terminal device and the transmission quality between the second terminal device and the source terminal device.

[0050] In one possible implementation, for the source terminal device to determine the fourth terminal device among the plurality of second terminal devices based on the eighth information includes the source terminal device determining whether there is a second terminal device that satisfies the eighth condition among the plurality of first terminal devices based on the eighth information. When there is a second terminal device that satisfies the eighth condition among the plurality of second terminal devices, the source terminal device determines the second terminal device that satisfies the eighth condition as the fourth terminal device; or when there is no second terminal device that satisfies the eighth condition among the plurality of second terminal devices, the source terminal device determines the second terminal device having a direct path to the source terminal device among the plurality of second terminal devices as the fourth terminal device. The eighth condition includes that there is an indirect path between the second terminal device and the source terminal device and the transmission quality between the second terminal device and the source terminal device is equal to or higher than the tenth threshold; or the eighth condition includes that there is an indirect path between the second terminal device and the source terminal device and both the transmission quality between the second terminal device and the target terminal device and the transmission quality between the second terminal device and the source terminal device are greater than the eleventh threshold.

[0051] When the source terminal device does not select a second terminal device that satisfies the sixth condition and the seventh condition, the source terminal device may select the second terminal device from the indirect path as the fourth terminal device, and whether the transmission quality between the second terminal device and the source terminal device satisfies the corresponding requirement, or both the transmission quality between the second terminal device and the source terminal device and the transmission quality between the second terminal device and the source terminal device satisfy the corresponding requirement. In this way, the transmission quality between the source terminal device and the fourth terminal device can be guaranteed, thereby guaranteeing the reliability of subsequent communication between the source terminal device and the fourth terminal device.

[0052] If the source terminal device does not select a second terminal device that satisfies the sixth condition, the seventh condition, and the eighth condition, the source terminal device may directly determine, as the fourth terminal device, a second terminal device that has a direct path to the source terminal device. In this way, the delay of communication between the source terminal device and the fourth terminal device can be reduced.

[0053] In a possible implementation form, the third message includes the transmission quality between the second terminal device and the target terminal device.

[0054] In a possible implementation form, when a plurality of fourth terminal devices are determined, the communication method further includes a step in which the source terminal device determines a fifth terminal device among the plurality of fourth terminal devices and uses the fifth terminal device as the final fourth terminal device. The fifth terminal device is the terminal device with the highest transmission quality with the target terminal device among the plurality of fourth terminal devices; or the fifth terminal device is the terminal device with the highest transmission quality with both the target terminal device and the source terminal device among the plurality of fourth terminal devices.

[0055] In a possible implementation form, for the source terminal device to determine a fourth terminal device among a plurality of second terminal devices based on the seventh information includes the source terminal device determining, as the fourth terminal device, a second terminal device that has established a unicast connection with the source terminal device among the plurality of second terminal devices.

[0056] In a possible implementation form, for the source terminal device to determine, as the second terminal device, a first terminal device that has established a unicast connection with the target terminal device among the plurality of first terminal devices includes the source terminal device determining, as the fourth terminal device, a first terminal device that has established a unicast connection with the target terminal device among the plurality of first terminal devices and whose transmission quality with the target terminal device is equal to or higher than a twelfth threshold.

[0057] In one possible implementation, when a first link is established between a source terminal device and a target terminal device, and the transmission quality of a second link and / or a third link does not meet the quality transmission conditions, or when the second link and / or the third link is interrupted, a first request message is used to request discovering the target terminal device, which includes that the first request message is used to request rediscovering the target terminal device. The second link is a link between a second relay device and the target terminal device, and the third link is a link between the second relay device and the source terminal device.

[0058] In one possible implementation, when the second link and / or the third link is interrupted, before the source terminal device sends a first request message, the communication method further includes a step that the source terminal device receives a link interruption message sent by the second relay device. The link interruption message indicates that the link between the second relay device and the target terminal device is interrupted. The source terminal device releases the end-to-end unicast connection established between the source terminal device and the target terminal device and the context information of the unicast connection associated with the second link and the third link.

[0059] According to a fourth aspect, a communication device is provided. The communication device may be a first relay device, or a chip or a circuit of the first relay device. This is not limited in this application.

[0060] The communication device is a transceiver unit configured to receive a first request message from a source terminal device, where the first request message is used to request discovery of a target terminal device, and the first request message includes an identifier of the source terminal device and an identifier of the target terminal device, a transceiver unit, and when the transmission quality of the communication device meets a first condition and / or when the capability of the communication device meets a second condition, a processing unit configured to transmit a second request message to the target terminal device based on the first request message. The transmission quality of the communication device is determined based on the first request message. The second condition includes a condition related to the quality of service QoS. The second request message is used to request discovery of the target terminal device, and the second request message includes an identifier of the source terminal device, an identifier of the target terminal device, and an identifier of the communication device.

[0061] In one possible implementation, the communication device's transmission quality meeting the first condition includes the communication device's transmission quality being greater than or equal to a first threshold; or the communication device's transmission quality being greater than or equal to a first threshold and the communication device's transmission quality being less than or equal to a second threshold. The second threshold is greater than the first threshold.

[0062] In one possible implementation, the first request message includes a first quality of service QoS requirement of the source terminal device regarding the source terminal device and the target terminal device.

[0063] In one possible implementation, the communication device's capability meeting the second condition includes the communication device's capability meeting a first QoS requirement.

[0064] In one possible implementation, the transceiver unit is further configured to receive a first response message to the second request message from the target terminal device and send a second response message to the source terminal device for the first request message. The second response message includes an identifier of the communication device and / or an identifier of the target terminal device.

[0065] In one possible implementation, the processing unit is further configured to determine whether to send the second response message to the source terminal device based on the first reference information and / or the second reference information. The first reference information includes the transmission quality of the first response message. The second reference information includes whether a unicast connection is established between the communication device and the source terminal device.

[0066] In one possible implementation, the processing unit determines to send the second response message to the source terminal device when the transmission quality of the first response message is greater than or equal to a third threshold; or is further specifically configured to determine to send the second response message to the source terminal device when the transmission quality of the first response message is greater than or equal to the third threshold and the transmission quality of the first response message is less than or equal to a fourth threshold. The fourth threshold is greater than the third threshold.

[0067] In one possible implementation, the processing unit is further specifically configured to determine to send the second response message to the source terminal device when a unicast connection is established between the communication device and the source terminal device.

[0068] In a possible implementation form, the transceiver unit is further configured to receive a third request message from the source terminal device. The third request message is used to request to establish a first unicast connection. The third request message includes the second QoS requirement of the source terminal device regarding the communication device and the target terminal device. The first unicast connection is a connection between the source terminal device and the communication device. When the capabilities of the communication device meet the second QoS requirement, the processing unit is further specifically configured to establish a first unicast connection with the source terminal device; or when the capabilities of the communication device do not meet the second QoS requirement, the processing unit is further specifically configured to skip establishing a first unicast connection to the source terminal device.

[0069] In a possible implementation form, the transceiver unit is further configured to send a fourth request message to the target terminal device. The fourth request message is used to request to establish a second unicast connection. The second unicast connection is a connection between the target terminal device and the communication device. The transceiver unit is further configured to receive a third response message from the target terminal device. The third response message includes the third QoS requirement of the target terminal device regarding the communication device and the source terminal device. When the capabilities of the communication device meet the third QoS requirement, the transceiver unit is further specifically configured to establish a second unicast connection with the target terminal device; or when the capabilities of the communication device do not meet the third QoS requirement, the transceiver unit is further specifically configured to skip establishing a second unicast connection to the target terminal device.

[0070] In a possible implementation, when a first link is established between a source terminal device and a target terminal device, and the transmission quality of the second link and / or the third link does not meet the quality transmission conditions, or the second link and / or the third link is interrupted, the first request message is used to request discovering the target terminal device, which includes that the first request message is used to request rediscovering the target terminal device. The second link is a link between a second relay device and the target terminal device, and the third link is a link between the second relay device and the source terminal device.

[0071] For the technical effects of any possible implementation of the fourth aspect, reference may be made to the technical effects of the corresponding implementation of the first aspect. Details will not be described again in this specification.

[0072] According to the fifth aspect, a communication device is provided. The communication device may be a target terminal device, or a chip or circuit of the target terminal device. This is not limited in this application.

[0073] The communication device is a transceiver unit configured to receive a first message from each of a plurality of first terminal devices, the first message being used to request discovery of the communication device, the first message including an identifier of the first terminal device and an identifier of the communication device, a transceiver unit, and at least one of the plurality of first terminal devices based on first information, second information, and / or third information. A processing unit configured to determine a second terminal device of the plurality of first terminal devices. The transceiver unit is further configured to transmit a second message to at least one second terminal device. The second message indicates that the communication device has been discovered, and the second message includes an identifier of the communication device. The first information indicates a direct or indirect path between the first terminal device and the communication device and a transmission quality between the first terminal device and the communication device. The transmission quality between the first terminal device and the communication device is determined based on the first message. The second information indicates whether a unicast connection has been established between the first terminal device and the communication device. The third information indicates a first quality of service QoS requirement of the source terminal device regarding the source terminal device and the communication device.

[0074] In a possible implementation, the processing unit determines, based on the first information, whether there is a first terminal device among the plurality of first terminal devices that satisfies a third condition; when there is a first terminal device among the plurality of first terminal devices that satisfies the third condition, determining the first terminal device that satisfies the third condition as the second terminal device; or when there is no first terminal device among the plurality of first terminal devices that satisfies the third condition, determining, based on the second information, whether there is a first terminal device among the plurality of first terminal devices that satisfies a fourth condition. Specifically configured as follows. The third condition includes that there is a direct path between the first terminal device and the communication device and that the transmission quality between the first terminal device and the communication device is equal to or higher than a fifth threshold. The fourth condition includes that a unicast connection is established between the first terminal device and the communication device.

[0075] In a possible implementation form, when there is a first terminal device that meets the fourth condition among a plurality of first terminal devices, the processing unit determines the first terminal device that meets the fourth condition as the second terminal device; or when there is no first terminal device that meets the fourth condition among the plurality of first terminal devices, the processing unit is further specifically configured to determine the second terminal device among the plurality of first terminal devices based on the fourth information. The fourth information includes the transmission quality between the first terminal device and the communication device.

[0076] In a possible implementation form, the processing unit determines, based on the fourth information, whether there is a first terminal device that meets the fifth condition among the plurality of first terminal devices; when there is a first terminal device that meets the fifth condition among the plurality of first terminal devices, the processing unit determines the first terminal device that meets the fifth condition as the second terminal device; or when there is no first terminal device that meets the fifth condition among the plurality of first terminal devices, the processing unit is further specifically configured to determine the first terminal device having a direct path to the communication device among the plurality of first terminal devices as the second terminal device. The fifth condition includes that there is an indirect path between the first terminal device and the communication device and the transmission quality between the first terminal device and the communication device is equal to or higher than a sixth threshold value; or the fifth condition includes that there is an indirect path between the first terminal device and the communication device and both the transmission quality between the first terminal device and the communication device and the transmission quality between the first terminal device and the source terminal device are greater than a seventh threshold value.

[0077] In a possible implementation form, the first message includes the transmission quality between the first terminal device and the source terminal device.

[0078] In a possible implementation form, the processing unit is further configured to determine a third terminal device among a plurality of second terminal devices and use the third terminal device as the final second terminal device. The third terminal device is the terminal device with the highest transmission quality with the communication device among the plurality of second terminal devices; or the third terminal device is the terminal device with the highest transmission quality with both the communication device and the source terminal device among the plurality of second terminal devices.

[0079] In a possible implementation form, the processing unit is further specifically configured to determine, as the second terminal device, a first terminal device that has established a unicast connection with the communication device among a plurality of first terminal devices.

[0080] In a possible implementation form, the processing unit is further specifically configured to determine, as the second terminal device, a first terminal device that has established a unicast connection with the communication device and whose transmission quality with the communication device is equal to or higher than an eighth threshold among a plurality of first terminal devices.

[0081] In a possible implementation form, the processing unit is further specifically configured to determine, as the second terminal device, a first terminal device that meets a first QoS requirement among a plurality of first terminal devices.

[0082] In a possible implementation form, the first message includes a first QoS requirement.

[0083] For the technical effects of any possible implementation form of the fifth aspect, reference may be made to the technical effects of the corresponding implementation form of the second aspect. Details will not be described again in this specification.

[0084] According to the sixth aspect, a communication device is provided. The communication device may be a source terminal device, or a chip or circuit of the source terminal device. This is not limited in this application.

[0085] The communication device is a transceiver unit configured to transmit a first request message, where the first request message is used to request discovery of a target terminal device, the first request message includes an identifier of a source terminal device and an identifier of the target terminal device, the transceiver unit is further configured to receive a third message from each of a plurality of second terminal devices, the third message indicates that the target terminal device has been discovered, and the third message includes an identifier of the second terminal device or the third message includes an identifier of the second terminal device and an identifier of the target terminal device, a transceiver unit, and a processing unit configured to determine a fourth terminal device among the plurality of second terminal devices based on sixth information and / or seventh information. The processing unit is further configured to establish a unicast connection with the target terminal device via the fourth terminal device. The sixth information indicates a direct or indirect path between the second terminal device and the source terminal device and the transmission quality between the second terminal device and the source terminal device. The transmission quality between the second terminal device and the source terminal device is determined based on the third message. The seventh information indicates whether a unicast connection has been established between the second terminal device and the source terminal device.

[0086] In a possible implementation form, the processing unit determines, based on the sixth piece of information, whether there is a fourth terminal device that meets the sixth condition among a plurality of second terminal devices; when there is a second terminal device that meets the sixth condition among the plurality of second terminal devices, determines the second terminal device that meets the sixth condition as the fourth terminal device; or when there is no second terminal device that meets the sixth condition among the plurality of second terminal devices, further configured to determine, based on the seventh piece of information, whether there is a second terminal device that meets the seventh condition among the plurality of second terminal devices. The sixth condition includes that there is a direct path between the second terminal device and the source terminal device, and the transmission quality between the second terminal device and the source terminal device is equal to or higher than the ninth threshold. The seventh condition includes that a unicast connection is established between the second terminal device and the source terminal device.

[0087] In a possible implementation form, the processing unit determines, when there is a second terminal device that meets the seventh condition among the plurality of second terminal devices, the second terminal device that meets the seventh condition as the fourth terminal device; or when there is no second terminal device that meets the seventh condition among the plurality of second terminal devices, further configured to determine the fourth terminal device among the plurality of second terminal devices based on the eighth piece of information. The eighth piece of information includes the transmission quality between the second terminal device and the source terminal device; or the eighth piece of information includes the transmission quality between the second terminal device and the target terminal device and the transmission quality between the second terminal device and the source terminal device.

[0088] In a possible implementation form, the processing unit determines whether there is a second terminal device that satisfies the eighth condition among a plurality of first terminal devices based on the eighth information; when there is a second terminal device that satisfies the eighth condition among the plurality of second terminal devices, determines the second terminal device that satisfies the eighth condition as the fourth terminal device; or when there is no second terminal device that satisfies the eighth condition among the plurality of second terminal devices, further specifically configures to determine the second terminal device having a direct path to the source terminal device among the plurality of second terminal devices as the fourth terminal device. The eighth condition includes that there is an indirect path between the second terminal device and the source terminal device and the transmission quality between the second terminal device and the source terminal device is equal to or higher than the tenth threshold; or the eighth condition includes that there is an indirect path between the second terminal device and the source terminal device and both the transmission quality between the second terminal device and the target terminal device and the transmission quality between the second terminal device and the source terminal device are greater than the eleventh threshold.

[0089] In a possible implementation form, the third message includes the transmission quality between the second terminal device and the target terminal device.

[0090] In a possible implementation form, the processing unit is further configured to determine a fifth terminal device among the plurality of fourth terminal devices and use the fifth terminal device as the final fourth terminal device. The fifth terminal device is the terminal device with the highest transmission quality with the target terminal device among the plurality of fourth terminal devices; or the fifth terminal device is the terminal device with the highest transmission quality with both the target terminal device and the source terminal device among the plurality of fourth terminal devices.

[0091] In a possible implementation form, the processing unit is further specifically configured to determine the second terminal device that has established a unicast connection with the source terminal device among the plurality of second terminal devices as the fourth terminal device.

[0092] In a possible implementation form, the processing unit is further specifically configured to determine a first terminal device whose transmission quality with a target terminal device is above a twelfth threshold and which has established a unicast connection with the target terminal device among a plurality of first terminal devices as the fourth terminal device.

[0093] In a possible implementation form, when a first link is established between a source terminal device and a target terminal device, and the transmission quality of the second link and / or the third link does not meet the quality transmission condition, or when the second link and / or the third link is interrupted, the first request message is used to request discovering the target terminal device, which includes that the first request message is used to request rediscovering the target terminal device. The second link is a link between the second relay device and the target terminal device, and the third link is a link between the second relay device and the source terminal device.

[0094] In a possible implementation form, when the second link and / or the third link is interrupted, before the source terminal device sends the first request message, the transceiver unit is further configured to receive a link interruption message sent by the second relay device. The link interruption message indicates that the link between the second relay device and the target terminal device is interrupted. The processing unit is further configured to release the end-to-end unicast connection established between the source terminal device and the target terminal device and the context information of the unicast connection associated with the second link and the third link.

[0095] For the technical effects of any possible implementation form of the sixth aspect, refer to the technical effects of the corresponding implementation form of the third aspect. Details will not be described again in this specification.

[0096] According to a seventh aspect, a communication device is provided that includes one or more processors, a memory, and one or more computer programs. The one or more computer programs are stored in the memory. The one or more computer programs include instructions. When the instructions are executed by the communication device, the communication device is enabled to execute the communication method in any possible implementation form from the first aspect to the third aspect.

[0097] According to an eighth aspect, a processor is provided that is configured to execute the communication method in any possible implementation form from the first aspect to the third aspect.

[0098] Operations such as transmission and acquisition / reception related to the processor, unless otherwise specified, or unless the operation conflicts with the actual function or internal logic of the operation in the related description, can be understood as operations such as the output and reception or input of the processor, or operations such as transmission and reception executed by the radio frequency circuit and antenna. This is not limited in this application.

[0099] According to a ninth aspect, a chip system including a processor is provided. The processor is configured to call a computer program from the memory and execute the computer program to enable a communication device equipped with the chip system to execute the communication method in any possible implementation form from the first aspect to the third aspect.

[0100] Optionally, in one implementation form, the chip further includes a memory. The memory stores a computer program or instructions. The processor is configured to execute the computer program or instructions stored in the memory. When the computer program or instructions are executed, the processor is configured to execute the communication method in any possible implementation form from the first aspect to the third aspect.

[0101] According to a tenth aspect, a computer program product including instructions is provided. When the computer program product operates on a communication device, the communication device is enabled to execute a communication method in any possible implementation form from the first aspect to the third aspect.

[0102] According to an eleventh aspect, a computer-readable storage medium is provided. The storage medium may be non-volatile. The storage medium includes instructions. When the instructions are operated by a communication device, the communication device is enabled to execute a communication method in any possible implementation form from the first aspect to the third aspect.

[0103] According to a twelfth aspect, a chip including at least one processor and an interface circuit is provided. The interface circuit is configured to provide program instructions or data to the at least one processor. The at least one processor is configured to execute program instructions to implement a communication method in any possible implementation form from the first aspect to the third aspect.

[0104] According to a thirteenth aspect, a communication system including a first relay device, a target terminal device, and / or a source terminal device is provided. The first relay device is configured to execute a communication method in any possible implementation form of the first aspect. The target terminal device is configured to execute a communication method in any possible implementation form of the second aspect. The source terminal device is configured to execute a communication method in any possible implementation form of the third aspect.

Brief Description of the Drawings

[0105]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0106] Hereinafter, with reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be described.

[0107] Before the embodiments of the present application are described, the following explanations are first provided to facilitate the understanding of the embodiments of the present application.

[0108] First, in the embodiments of the present application, the "instruction" may include direct instructions and indirect instructions, or may include explicit instructions and implicit instructions. Information indicated by a specific signal (e.g., the following first information) is called instruction target information. In a specific implementation process, the instruction target information may be instructed in multiple ways. By way of non-limiting example, the instruction target information may be directly instructed, for example, by the instruction target information or an index of the instruction target information. Alternatively, the instruction target information may be indirectly indicated by indicating other information, and there is a relationship between the other information and the instruction target information. Alternatively, only a part of the instruction target information may be indicated, and the other parts of the instruction target information are known or pre-agreed. For example, the specific information may alternatively be indicated using a pre-agreed arrangement sequence of a plurality of information (e.g., specified by a protocol) to reduce the instruction overhead to a certain extent.

[0109] Second, the terms "first", "second", and various numbers in the following embodiments are merely used for distinction for the sake of easy explanation and are not intended to limit the scope of the embodiments of the present application. For example, different messages are distinguished, or different information is distinguished.

[0110] Third, "a plurality of" in the embodiments of the present application usually means two or more.

[0111] Fourth, the direct path between two terminal devices in the embodiments of the present application may mean that the two terminal devices can receive broadcast or multicast information from each other without transferring through another terminal device. In this case, a unicast connection link is not established between the two terminal devices.

[0112] For example, the direct path between the first terminal device and the target terminal device in the following description can be understood as the first terminal device being able to communicate directly with the target terminal device without transferring through another terminal device. In this case, no link is established between the first terminal device and the target terminal device.

[0113] Fifthly, the indirect path in the embodiments of the present application means that two terminal devices can communicate with each other only through transfer via another terminal device. In this case, no link is established between the two terminal devices.

[0114] For example, the indirect path between the first terminal device and the target terminal device in the following description can be understood as the first terminal device being able to communicate with the target terminal device only through transfer by another terminal device. In this case, no link is established between the first terminal device and the target terminal device.

[0115] Sixthly, in the embodiments of the present application, an example of functioning as an active party for the source terminal device to discover the target terminal device is used, which should not constitute a limitation to the present application. For example, in some embodiments, the target terminal device may alternatively function as an active party that requests to discover the source terminal device. In this case, in the example where the source terminal device is used to request to discover the target terminal device, only the execution steps executed by the target terminal device and the execution steps executed by the source terminal device need to be exchanged.

[0116] The terminal device in the embodiments of the present application may also be referred to as a user equipment (UE), an access terminal, a subscriber unit, a subscriber station, a mobile station, a remote station, a remote terminal, a mobile device, a user terminal, a terminal, a wireless communication device, a user agent, or a user device. The terminal device in the embodiments of the present application may be a mobile phone, a tablet computer (pad), a computer with a wireless transceiver function, a virtual reality (VR) terminal device, an augmented reality (AR) terminal device, a wireless terminal for industrial control, a wireless terminal for self-driving, a wireless terminal for remote medical, a wireless terminal for smart grid, a wireless terminal for transportation safety, a wireless terminal for smart city, or a wireless terminal for smart home, etc. The application scenario is not limited in the embodiments of the present application.

[0117] In an embodiment of the present application, the terminal device includes a hardware layer, an operating system layer operating on the hardware layer, and an application layer operating on the operating system layer. The hardware layer includes hardware such as a central processing unit (CPU), a memory management unit (MMU), and a memory (also referred to as main memory). The operating system may be one or more computer operating systems that perform service processing through a process, for example, a Linux (registered trademark) operating system, a Unix (registered trademark) operating system, an Android (registered trademark) operating system, an iOS (registered trademark) operating system, or a Windows (registered trademark) operating system. The application layer includes applications such as a browser, an address book, word processing software, and instant messaging software. In addition, the specific structure of the execution body of the method provided in the embodiment of the present application is not specifically limited in the embodiment of the present application as long as the program recording the code of the method provided in the embodiment of the present application can be operated to execute communication according to the method provided in the embodiment of the present application. For example, the method provided in the embodiment of the present application may be executed by a terminal device or a functional module within the terminal device that can call and execute the program.

[0118] In addition, aspects or features of the present application may be implemented as a method, apparatus, or product using standard programming techniques and / or engineering techniques. The term "product" as used in the present application includes a computer program that can be accessed from any computer-readable component, carrier, or medium. For example, computer-readable media can include, but are not limited to, magnetic storage components (such as hard disks, floppy disks, or magnetic tapes), optical disks (such as compact discs (CDs) or digital versatile discs (DVDs)), smart cards, and flash memory components (such as erasable programmable read-only memories (EPROMs), cards, sticks, or key drives). In addition, the various storage media described herein may represent one or more devices and / or other machine-readable media configured to store information. The term "machine-readable media" may include, but is not limited to, wireless channels and various other media capable of storing, containing, and / or carrying instructions and / or data.

[0119] In a wireless communication system, terminal devices may perform data communication with each other via a network device, or terminal devices may directly perform communication with each other without passing through a network device. In this way, communication latency can be effectively reduced.

[0120] The interface between terminal devices is called a PC5 interface, and the PC5 interface is similar to the Uu interface between a terminal device and a network device.

[0121] The link between terminal devices is called SL, and a typical application scenario of SL communication is vehicle-to-everything (V2X). In vehicle-to-everything, each vehicle may be regarded as a terminal device.

[0122] SL supports broadcast communication, unicast communication, and multicast communication. Below, broadcast communication, unicast communication, and multicast communication will be described separately.

[0123] (1) Broadcast communication This is similar to a network device broadcasting system information. Specifically, the terminal device transmits the data of the broadcast service to the outside without encryption. If a terminal device is interested in the broadcast service, any other terminal device within the effective reception range can receive the data of the broadcast service.

[0124] (2) Unicast communication This is similar to the data communication executed after a radio resource control (RRC) connection is established between a terminal device and a network device. In unicast communication, two terminal devices need to first establish a unicast connection. After the unicast connection is established, the two terminal devices execute data communication based on the negotiated identifiers (source L2 ID and destination L2 ID described later).

[0125] The unicast communication executed once on the SL corresponds to a pair of IDs, namely, a source layer 2 identifier (L2 ID) and a destination layer 2 identifier (destination L2 ID). The sub-header of each SL media access control protocol data unit (MAC PDU) contains several bytes of the source L2 ID and several bytes of the destination L2 ID so that the data can be transmitted to the correct receiving end.

[0126] The data transmitted between two terminal devices may or may not be encrypted. In unicast communication, compared with broadcast communication, unicast communication can be executed only between two terminal devices with a unicast connection established.

[0127] (3) Multicast communication This means communication between all terminal devices within a communication group. Any terminal device within the group can receive and transmit data of the multicast service.

[0128] To expand the coverage or improve the capacity of the SL, the UE to UE relay technology, that is, the technology in which the source terminal device communicates with the target terminal device via a relay terminal device, can be used. Hereinafter, with reference to FIGS. 1 and 2, the UE to UE relay communication system provided in the embodiments of the present application will be described.

[0129] FIG. 1 is a diagram of the architecture of a communication system applicable to an embodiment of the present application.

[0130] For example, as shown in FIG. 1, a UE-to-UE relay communication system includes one source terminal device (source UE, which may also be called the starting terminal device), at least one relay terminal device (relay UE), and at least one target terminal device (target UE). For example, when there is a requirement for unicast communication between the source terminal device and the target terminal device, if the coverage signal between the source terminal device and the target terminal device is insufficient, or the target terminal device is located outside the signal coverage area of the source terminal device (or the communication range of the source terminal device), in order to improve the coverage extension function or capacity function of the SL, the data and signaling transmission between the source terminal device and the target terminal device can be implemented via the relay terminal device. In the L2-based relay method, user plane data is relayed and transferred under the packet data convergence protocol (PDCP) layer on the relay terminal device side.

[0131] It should be understood that FIG. 1 is only a simplified diagram of an example for ease of understanding. The communication system may further include other devices not depicted in FIG. 1.

[0132] Currently, UE-to-UE relay includes two possible implementation forms, namely, layer 3 (L3)-based relay mode and L2-based relay mode. In the L3-based relay mode, user plane data is transferred at the internet protocol (IP) layer. Specifically, the relay terminal device needs to parse the data packet sent by the source terminal device to the target terminal device at the IP layer and determine to transfer the packet to the target terminal device based on information such as the IP address. In the L2-based relay mode, user plane data is transferred under the packet data convergence protocol (PDCP) layer. In this case, the user plane protocol stack is shown in Figure 2.

[0133] Figure 2 is a diagram of the protocol stack of the communication system shown in Figure 1 based on L2.

[0134] For example, as shown in Figure 2, the user plane protocol stack of the source terminal device includes an IP / non-IP layer, a service data adaptation protocol (SDAP) layer, a packet data convergence protocol (PDCP) layer, an adaptation layer, a radio link control (RLC) layer, a medium access control (MAC) layer, and a physical layer (PHY).

[0135] The user plane protocol stack of the relay terminal device includes an adaptation layer, an RLC layer, a MAC layer, and a PHY layer.

[0136] The user plane protocol stack of the target terminal device includes the IP / non-IP layer, SDAP layer, PDCP layer, adaptation layer, RLC layer, MAC layer, and PHY.

[0137] The main functions of the adaptation layer include bearer multiplexing and demultiplexing, that is, supporting the multiplexing of different bearers into one bearer or splitting one bearer into different bearers. When the source terminal device communicates with multiple target terminal devices through one relay terminal device, a local identifier (local ID) needs to be assigned to each target terminal device to distinguish data belonging to different target terminal devices. The local identifier is carried in the data packet routing process to indicate the target terminal device to which the data belongs.

[0138] The source terminal device exchanges information with the target terminal device through the PDCP layer, and the source terminal device exchanges information with the relay terminal device through the adaptation layer.

[0139] In the UE to UE relay communication system, the source terminal device needs to discover, select, and connect to the relay terminal device in order to directly transmit information to the target terminal device.

[0140] The solutions for the source terminal device to discover the relay terminal device may include two discovery models.

[0141] (1) Model A In Model A, the terminal device with relay capabilities actively broadcasts a discovery message to the surroundings. The discovery message indicates that the terminal device has relay capabilities. In other words, the terminal device can function as a relay terminal device for communication between two terminal devices.

[0142] (2) Model B In Model B, the source terminal device actively broadcasts a solicitation message to the surroundings. The solicitation message is used to inquire whether there is a relay terminal device in the surroundings. After receiving the solicitation message, the terminal device determines whether to return a response message based on the solicitation message and the status of the terminal device (e.g., whether the terminal device has relay capabilities).

[0143] Note that in the communication method provided by the embodiments of the present application, the solution for the source terminal device to discover the relay terminal device is Model B.

[0144] In a UE to UE relay communication system, there may be multiple relay terminal devices. In this case, after all of the multiple relay terminal devices receive the solicitation message broadcast by the source terminal device, they forward the solicitation message to the target terminal device. Then, the target terminal device may select one relay terminal device from among the multiple relay terminal devices and return a response message to the selected relay terminal device. The relay terminal device forwards the response message to the source terminal device. Furthermore, the source terminal device is connected to the target terminal device via the relay terminal device and can communicate with the target terminal device. In this way, the communication quality between the source terminal device and the target terminal device depends on the selected relay terminal device.

[0145] However, in the existing solutions, it cannot be guaranteed that the relay terminal device selected from among the multiple relay terminal devices is appropriate, and the reliability of the unicast communication between the source terminal device and the target terminal device cannot be guaranteed.

[0146] Based on this, an embodiment of the present application provides a communication method. The communication method can ensure that the selected relay terminal device is appropriate in order to guarantee the reliability of unicast communication between the source terminal device and the target terminal device.

[0147] An example of the communication method provided by the embodiment of the present application will be described in detail below with reference to FIG. 3.

[0148] FIG. 3 is an exemplary flowchart of a communication method 300 according to an embodiment of the present application.

[0149] For example, as shown in FIG. 3, the communication method 300 includes S301 to S303, and S302 is an optional step. Hereinafter, S301 to S303 will be described in detail.

[0150] S301: The source terminal device sends a first request message.

[0151] For example, the source terminal device may send the first request message in a broadcast or multicast manner.

[0152] The first request message is used to request to discover the target terminal device. The first request message includes the identifier of the source terminal device and the identifier of the target terminal device.

[0153] The type of the identifier of the terminal device is not limited in this embodiment of the present application.

[0154] For example, the identifier of the terminal device may be the user information identifier of the terminal device, for example, the identifier of the application (APP) layer.

[0155] In this example, the identifier of the source terminal device may be the identifier of the source terminal device in the APP layer. The identifier of the target terminal device may be the identifier of the target terminal device in the APP layer.

[0156] In one example, the first request message may further include the type of the first request message. The type of the first request message may be understood as the discovery type described above.

[0157] It should be understood that this embodiment of the present application is applicable when the type of the first request message is Model B.

[0158] In one example, the first request message may further include a relay service code (RSC), and the RSC indicates a connection service that can be supported by UE-to-UE relay.

[0159] In one example, the first request message may further include relay indication information, and the relay indication information indicates whether the relay device can participate in the UE-to-UE relay procedure. In other words, the relay indication information indicates whether the relay device is allowed to forward the first request message received by the relay device. For example, when the relay indication information indicates that the relay terminal device participates in the procedure, after receiving the relay indication information, the relay terminal device does not forward the relay terminal device to the next-hop terminal device. In this specification, when the first request message includes relay indication information, the first request message may be further considered to be used to request to discover the relay terminal device.

[0160] Optionally, in some embodiments, when a first link is established between a source terminal device and a target terminal device, and the transmission quality of a second link and / or a third link does not meet the quality transmission conditions, or the second link and / or the third link is interrupted (e.g., radio link failure (RLF)), a first request message is used to request discovering the target terminal device, which includes that the first request message is used to request rediscovering the target terminal device.

[0161] The first link may be regarded as a link established between the source terminal device and the target terminal device via a second relay device. The second link is a link between the second relay device and the target terminal device, and the third link is a link between the second relay device and the source terminal device.

[0162] Optionally, in this embodiment, the first request message may further carry the reason for rediscovering the target terminal device.

[0163] Optionally, in this embodiment, when the second link and / or the third link is interrupted, the second relay device may further send a link interruption message to the source terminal device. The link interruption message indicates that the link between the second relay device and the target terminal device is interrupted. After receiving the link interruption message, the source terminal device may further release the end-to-end unicast connection established between the source terminal device and the target terminal device and the context information of the unicast connection associated with the second link and the third link. The end-to-end unicast connection established between the source terminal device and the target terminal device may be understood as a logical unicast connection established between the source terminal device and the target terminal device via the relay device.

[0164] Based on S301, the terminal devices within the communication range (or communication distance) of the source terminal device can receive the first request message broadcast by the source terminal device.

[0165] In one example, when the target terminal device is within the communication range of the source terminal device, the target terminal device can directly receive the first request message broadcast by the source terminal device. Subsequently, the target terminal device directly sends a response message to the source terminal device, whereby the source terminal device establishes a unicast connection with the target terminal device.

[0166] In another example, when the target terminal device is not within the communication range of the source terminal device, the target terminal device cannot directly receive the first request message broadcast by the source terminal device. In this case, the source terminal device continues to discover the target terminal device via a terminal device (which may be understood as a relay terminal device) within the communication range of the source terminal device, and it is necessary to establish a unicast connection with the target terminal device via the terminal device within the communication range of the source terminal device.

[0167] When the target terminal device is not within the communication range of the source terminal device, in one example, after receiving the first request message, the terminal device within the communication range of the source terminal device may directly execute S303 without executing S302. In another example, to ensure the reliability of unicast communication between the source terminal device and the target terminal device, the terminal device within the communication range of the source terminal device may further determine whether to continue to assist the source terminal device in discovering the target terminal device. In other words, the terminal device within the communication range of the source terminal device needs to execute S302.

[0168] The number of terminal devices within the communication range of the source terminal device is not limited in this embodiment of the present application.

[0169] First, S302 will be described using an example where the terminal device within the communication range of the source terminal device is the first relay device.

[0170] S302: The first relay device determines whether to send a second request message to the target terminal device.

[0171] The second request message is used to request discovery of the target terminal device, and the second request message includes the identifier of the source terminal device, the identifier of the target terminal device, and the identifier of the first relay device.

[0172] Hereinafter, S302 will be described in detail using Methods 1 to 5 as examples.

[0173] Method 1: The first relay device determines whether to send a second request message to the target terminal device based on whether the transmission quality of the first relay device meets the first condition.

[0174] Specifically, when the transmission quality of the first relay device meets the first condition, the first relay device determines to send the second request message to the target terminal device; or when the transmission quality of the first relay device does not meet the first condition, the first relay device does not send the second request message to the target terminal device.

[0175] In one example, the transmission quality of the first relay device meeting the first condition includes the transmission quality of the first relay device being equal to or higher than the first threshold. In this way, it can be ensured that the transmission quality between the first relay device and the source terminal device can meet the corresponding requirements.

[0176] In another example, the transmission quality of the first relay device is equal to or higher than the first threshold value, and the transmission quality of the first relay device is equal to or lower than the second threshold value. The second threshold value is greater than the first threshold value. In this way, it can be ensured that the transmission quality between the first relay device and the source terminal device can meet the corresponding requirements, and it is also possible to avoid the case where there is no gain because the first relay device is overly closed to the source terminal device.

[0177] The method by which the first relay device obtains the transmission quality of the first relay device is not limited in this application.

[0178] In one example, the transmission quality of the first relay device may be obtained by the first relay device based on the first request message currently being transmitted.

[0179] For example, the transmission quality of the first relay device may be the RSRP value of the first request message obtained by the first relay device measuring the reference signal received power (RSRP) of the first request message.

[0180] In this embodiment of this application, the type of the transmission quality of the first relay device is not limited. For example, in addition to the RSRP value of the first request message, the transmission quality of the first relay device may alternatively be the signal to interference plus noise ratio (SINR) value, the reference signal received quality (RSRQ) value, the received signal strength indicator (RSSI) value, etc. of the first request message.

[0181] In another example, the transmission quality of the first relay device may be obtained by the first relay device based on the information transmitted historically.

[0182] Method 2: The first relay device determines whether to send a second request message to the target terminal device based on whether the capabilities of the first relay device meet a second condition.

[0183] Specifically, when the capabilities of the first relay device meet the second condition, the first relay device determines to send a second request message to the target terminal device; or when the capabilities of the first relay device do not meet the second condition, the first relay device does not send the second request message to the target terminal device.

[0184] The second condition includes conditions related to quality of service QoS.

[0185] In one example, the capabilities of the first relay device meeting the second condition includes the capabilities of the first relay device meeting a first QoS requirement. The first QoS requirement is the first quality of service QoS requirement of the source terminal device with respect to the source terminal device and the target terminal device. In other words, the capabilities of the first relay device can meet the first quality of service QoS requirement of the source terminal device with respect to the source terminal device and the target terminal device.

[0186] The method by which the first relay device obtains the first QoS requirement is not limited in this application.

[0187] In one example, the first QoS requirement may be predefined or preconfigured. For example, the first QoS requirement may be specified by a communication protocol.

[0188] In another example, the first QoS requirement may be notified to the first relay device by the source terminal device. For example, the source terminal device may include the first QoS requirement in the first request message. Then, the first relay device can know the first QoS requirement.

[0189] For example, QoS may include priority, packet error rate, rate, delay, throughput, packet loss rate, and the like.

[0190] Method 3: The first relay device determines whether to send a second request message to the target terminal device based on whether the transmission quality of the first relay device meets the first condition and whether the capability of the first relay device meets the second condition.

[0191] Specifically, in one example, when the transmission quality of the first relay device meets the first condition and the capability of the first relay device meets the second condition, the first relay device determines to send a second request message to the target terminal device; or when the transmission quality of the first relay device does not meet the first condition and / or the capability of the first relay device does not meet the second condition, the first relay device does not send a second request message to the target terminal device.

[0192] In another example, when the transmission quality of the first relay device meets the first condition or the capability of the first relay device meets the second condition, the first relay device determines to send a second request message to the target terminal device; or when the transmission quality of the first relay device does not meet the first condition and the capability of the first relay device does not meet the second condition, the first relay device does not send a second request message to the target terminal device.

[0193] For the content not described in Method 3, such as the transmission quality of the first relay device, the first condition, and the second condition, please refer to the relevant descriptions of Method 1 and Method 2. Details are not described again in this specification.

[0194] In Modes 1 to 3, only when the transmission quality of the first relay device meets the conditions and / or when the capabilities of the first relay device meet the conditions related to the quality of service QoS, the first relay terminal device sends a request message requesting to discover the target terminal device to the target terminal device. In other words, the transmission quality of the first relay device and / or the QoS that can be provided by the first relay device meet the corresponding requirements, and the first relay device helps the source terminal device to continue discovering the target terminal device in order to ensure the reliability of subsequent communication between the source terminal device and the target terminal device via the first relay device.

[0195] Mode 4: When the first request message carries the RSC, the first relay device determines whether to send a second request message to the target terminal device based on the RSC.

[0196] Specifically, when the RSC carried in the first request message is greater than or equal to R18, the first relay device determines to send a second request message to the target terminal device; or when the RSC carried in the first request message is less than R18, the first relay device does not send a second request message to the target terminal device.

[0197] When the RSC carried in the first request message is less than R18, it should be understood that the source terminal device is a legacy UE and does not support UE-to-UE relay technology.

[0198] Mode 5: The first relay device determines whether to send a second request message to the target terminal device based on whether the first request message carries relay_indication information.

[0199] Specifically, when the first request message carries relay_indication information, the first relay device determines to send a second request message to the target terminal device. In this case, the second request message does not carry relay_indication information. When the first request message does not carry relay_indication information, the first relay device determines not to send the second request message to the target terminal device.

[0200] In methods 4 and 5, when the communication system supports UE-to-UE relay technology, the first relay terminal device sends a request message requesting to discover the target terminal device to the target terminal device. Specifically, when the communication system supports UE-to-UE relay technology, the first relay device can help the source terminal device continue to discover the target terminal device in order to avoid problems that occur when the source terminal device subsequently establishes a connection to the target terminal device via the first relay device.

[0201] After S302, that is, in S303, the first relay device sends a second request message to the target terminal device. Correspondingly, the target terminal device receives the second request message from the first relay device.

[0202] Optionally, in some embodiments, after receiving the first request message, the first relay device may directly execute S303 without executing S302.

[0203] Optionally, in some embodiments, after S303, the target terminal device may further send a response message to the source terminal device via the first relay device. In this case, as shown in FIG. 4, the communication method 300 further includes S304 and S305. Hereinafter, S304 and S305 will be described in detail.

[0204] S304: The target terminal device sends a first response message to the first relay device in response to the second request message. Correspondingly, the first relay device receives the first response message from the target terminal device.

[0205] S305: The first relay device sends a second response message to the source terminal device in response to the first request message. The second response message includes the identifier of the first relay device and / or the identifier of the target terminal device.

[0206] Optionally, in some embodiments, as shown in FIG. 4, before S305, the first relay device may further execute S306.

[0207] S306: The first relay device determines whether to send the second response message to the source terminal device based on the first reference information and / or the second reference information.

[0208] The first reference information includes the transmission quality of the first response message, and the second reference information includes whether a unicast connection is established between the first relay device and the source terminal device.

[0209] In one example, for the first relay device to determine whether to send the second response message to the source terminal device based on the first reference information includes that when the transmission quality of the first response message is equal to or higher than a third threshold, the first relay device determines to send the second response message to the source terminal device. In this way, it can be guaranteed that the transmission quality between the first relay device and the source terminal device can meet the corresponding requirements. Thereby, the reliability of subsequent communication between the source terminal device and the source terminal device via the first relay device is further guaranteed.

[0210] In another example, when the transmission quality of the first response message is equal to or higher than a third threshold and equal to or lower than a fourth threshold, the first relay device determines to send a second response message to the source terminal device. The fourth threshold is greater than the third threshold. In this way, it can be ensured that the transmission quality between the first relay device and the source terminal device can meet the corresponding requirements, and it is also possible to avoid the situation where there is no gain because the first relay device is overly closed to the source terminal device. Thereby, the reliability of subsequent communication between the source terminal device and the source terminal device via the first relay device is further guaranteed.

[0211] In one example, when the first relay device determines whether to send a second response message to the source terminal device based on the second reference information, when a unicast connection is established between the first relay device and the source terminal device, it includes that the first relay device determines to send a second response message to the source terminal device. In this way, the existing unicast connection between the first relay device and the source terminal device can be multiplexed, thereby shortening the time for establishing a link between the first relay device and the source terminal device and shortening the time for establishing a link between the source terminal device and the target terminal device.

[0212] Based on S301 to S305, the source terminal device may implement a process of discovering the target terminal device. Then, the source terminal device may establish a connection with the target terminal device.

[0213] Optionally, in some embodiments, in the process of the source terminal device establishing a connection to the target terminal device, if the source terminal device does not establish a first unicast connection to the first relay device, as shown in FIG. 4, the source terminal device needs to further execute S307.

[0214] S307: The source terminal device sends a third request message to the first relay device. Correspondingly, the first relay device receives the third request message from the source terminal device.

[0215] The third request message is used to request the establishment of a first unicast connection.

[0216] In one example, after receiving the third request message, the first relay device may directly establish a first unicast connection to the source terminal device, that is, S308 shown in FIG. 4.

[0217] In another example, after receiving the third request message, in order to guarantee the reliability of unicast communication between the source terminal device and the target terminal device, the first relay device further determines whether to establish a first unicast connection to the source terminal device, and can establish a first unicast connection to the source terminal device only when establishing a first unicast connection to the source terminal device.

[0218] In this example, as shown in FIG. 4, the first relay device needs to further execute S308 when it executes S309 and determines to establish a first unicast connection with the source terminal device.

[0219] S309: The first relay device determines whether to establish a first unicast connection with the source terminal device.

[0220] Specifically, when the capability of the first relay device meets the second QoS requirement, the first relay device establishes a first unicast connection to the source terminal device, that is, S313 shown in FIG. 4. When the capability of the first relay device does not meet the second QoS requirement, the first relay device does not establish a first unicast connection to the source terminal device. The second QoS requirement is the QoS requirement of the source terminal device regarding the first relay device and the target terminal device.

[0221] The method by which the first relay device obtains the second QoS requirement is not limited in this application.

[0222] In one example, the second QoS requirement may be predefined or preconfigured. For example, the second QoS requirement may be specified by a communication protocol.

[0223] In another example, the second QoS requirement may be notified by the source terminal device to the first relay device. For example, the source terminal device may include the second QoS requirement in a third request message. Then, the first relay device can know the second QoS requirement.

[0224] It should be noted that the fact that the first relay device does not establish a first unicast connection to the source terminal device can be understood as the first relay device sending a rejection message to the source terminal device or the first relay device not performing any operation.

[0225] After the first relay device establishes a first unicast connection to the source terminal device, the first relay device further needs to establish a second unicast connection to the target terminal device. As shown in FIG. 4, the first relay device further needs to execute S310.

[0226] Step S310: The first relay device sends a fourth request message to the target terminal device. Correspondingly, the target terminal device receives the fourth request message from the first relay device.

[0227] The fourth request message is used to request to establish a second unicast connection, and the second unicast connection is a connection between the target terminal device and the first relay device.

[0228] In one example, before S310, in order to ensure the reliability of unicast communication between the source terminal device and the target terminal device, the first relay device may further determine whether to establish a second unicast connection to the target terminal device, and execute S310 only when establishing the second unicast connection to the target terminal device.

[0229] In this example, as shown in FIG. 4, when the first relay device executes S311 and determines to establish a second unicast connection with the target terminal device, it is further necessary to execute S310.

[0230] S311: The first relay device needs to determine whether to establish a second unicast connection with the target terminal device.

[0231] Specifically, when the capabilities of the first relay device meet the third QoS requirement, the first relay device establishes a second unicast connection to the target terminal device. When the capabilities of the first relay device do not meet the third QoS requirement, the first relay device does not establish a second unicast connection to the target terminal device. The third QoS requirement is the QoS requirement of the target terminal device regarding the first relay device and the source terminal device.

[0232] The method by which the first relay device obtains the third QoS requirement is not limited in this application.

[0233] In one example, the third QoS requirement may be predefined or preconfigured. For example, the third QoS requirement may be specified in the communication protocol.

[0234] In another example, the third QoS requirement may be notified by the source terminal device to the first relay device. For example, after S310, the source terminal device needs to execute S312 shown in FIG. 4. Specifically, the source terminal device sends a third response message to the first relay device, and includes the third QoS requirement in the third response message. Then, the first relay device can know the third QoS requirement.

[0235] Based on S307 to S313, the source terminal device may implement a process of establishing a unicast connection to the target terminal device via the first relay device.

[0236] The target terminal device can usually receive a plurality of request messages. For example, the target terminal device directly receives the request message sent by the source terminal device and / or receives the request message sent by the source terminal device via the relay terminal device. In this case, the target terminal device may directly send a response message to the transmission body of the request message in order for the source terminal device to implement a process of discovering the target terminal device. Then, after receiving the response message, the source terminal device establishes a unicast connection with the target terminal device. Optionally, in some embodiments, in order to ensure the reliability of unicast communication between the source terminal device and the target terminal device, the target terminal device further selects at least one transmission entity from a plurality of transmission entities that send request messages in order for the source terminal device to implement a process of discovering the target terminal device, and sends the response message to at least one transmission entity. Then, after receiving the response message, the source terminal device establishes a unicast connection with the target terminal device.

[0237] Whether a plurality of request messages are directly sent by the source terminal device to the target terminal device or are sent by the source terminal device to the target terminal device via a relay device is not limited in the embodiments of the present application.

[0238] Another communication method provided in the present application will be described in detail below with reference to FIG. 5.

[0239] FIG. 5 is a schematic flowchart of a communication method 400 according to an embodiment of the present application.

[0240] For example, as shown in FIG. 5, the communication method 400 includes S401 to S403, and S402 is an optional step. Hereinafter, S401 to S403 will be described in detail.

[0241] S401: The target terminal device receives a first message from each of a plurality of first terminal devices.

[0242] The first message is used to request to discover the target terminal device, and the first message includes an identifier of the first terminal device and an identifier of the target terminal device.

[0243] Optionally, in some embodiments, the first message may further include an identifier of the source terminal device.

[0244] It should be noted that the plurality of first terminal devices may be of different types or of the same type. The type of the first terminal device may include whether the first terminal device is a source terminal device or a relay terminal device.

[0245] In one example, after the target terminal device receives the first message, the target terminal device may not execute S402 and directly execute S403. In this case, the fourth terminal device in S403 is the first terminal device in S401, and the number of the fourth terminal devices is equal to the number of the first terminal devices in S401.

[0246] In another example, in order to ensure the reliability of the unicast communication between the source terminal device and the target terminal device, the target terminal device may further execute S402 before executing S403.

[0247] S402: The target terminal device determines at least one second terminal device among a plurality of first terminal devices.

[0248] Hereinafter, S402 will be described in detail using Methods A to G as examples.

[0249] Method A: The target terminal device determines at least one second terminal device among a plurality of first terminal devices based on the first information.

[0250] The first information indicates a direct path or an indirect path between the first terminal device and the target terminal device, and the transmission quality between the first terminal device and the target terminal device.

[0251] In one example, the transmission quality between the first terminal device and the target terminal device may be obtained by the target terminal device via the first message being currently transmitted.

[0252] The type of transmission quality between the first terminal device and the target terminal device is not limited in this embodiment of the present application. For example, the transmission quality between the first terminal device and the target terminal device may be the RSRP value obtained by the target terminal device by measuring the RSRP of the first message. In addition, the transmission quality of the first relay device may alternatively be the SINR value, RSRQ value, or RSSI value of the first message.

[0253] In another example, the transmission quality between the first terminal device and the target terminal device may be obtained by the target terminal device via historical information transmitted between the target terminal device and the first terminal device.

[0254] For example, if the first message carries only the identifier of the first terminal device and the identifier of the target terminal device and does not carry the identifier of another terminal device (for example, the identifier of the relay device), it may be considered that there is a direct path between the first terminal device and the target terminal device. In other words, the first terminal device is the source terminal device. If the first message carries the identifier of the source terminal device in addition to the identifier of the first terminal device and the identifier of the target terminal device, it may be considered that there is an indirect path between the first terminal device and the target terminal device. In other words, the first terminal device is a relay device.

[0255] Specifically, the target terminal device determining at least one second terminal device among a plurality of first terminal devices based on the first information includes the following steps.

[0256] S11: The target terminal device determines, based on the first information, whether there is a first terminal device that satisfies a third condition among the plurality of first terminal devices. The third condition includes that there is a direct path between the first terminal device and the target terminal device and the transmission quality between the first terminal device and the target terminal device is equal to or higher than a fifth threshold.

[0257] It should be understood that when there is a direct path between the first terminal device and the target terminal device, the first terminal device may be regarded as the source terminal device described above. When there is an indirect path between the first terminal device and the target terminal device, the first terminal device may be regarded as the first relay device described above.

[0258] When there is a first terminal device that satisfies the third condition among a plurality of first terminal devices, the first terminal device that satisfies the third condition is determined as the second terminal device.

[0259] Optionally, as an example, when there are a plurality of first terminal devices that all satisfy the third condition among the plurality of first terminal devices, the target terminal device may further select, from the plurality of first terminal devices that satisfy the third condition, the first terminal device with the highest transmission quality with the target terminal device, and use the first terminal device as the second terminal device. In this way, it can be guaranteed that the transmission quality between the second terminal device and the target terminal device can meet the corresponding requirements, and it can also be guaranteed that the transmission quality between the second terminal device and the target terminal device among the plurality of first terminal devices is the best.

[0260] When there is no first terminal device that satisfies the third condition among the plurality of first terminal devices, the target terminal device executes S12.

[0261] S12: The target terminal device determines, based on the fourth information, whether there is a first terminal device that satisfies the fifth condition among the plurality of first terminal devices. The fourth information includes the transmission quality between the first terminal device and the target terminal device.

[0262] When there are multiple first terminal devices that meet the fifth condition among the multiple first terminal devices, the target terminal device determines a first terminal device that meets the fifth condition as the second terminal device.

[0263] When there is no first terminal device that meets the fifth condition among the multiple first terminal devices, the target terminal device determines a first terminal device that has a direct path to the target terminal device among the multiple first terminal devices as the second terminal device.

[0264] Hereinafter, S12 will be described in detail using an example where the fifth condition is Case 1 and an example where the fifth condition is Case 2.

[0265] Case 1: The fifth condition includes that there is an indirect path between the first terminal device and the target terminal device, and the transmission quality between the first terminal device and the target terminal device is greater than a sixth threshold. In this case, the sixth threshold is greater than the fifth threshold.

[0266] Optionally, in one example, when there are multiple first terminal devices that meet all the fifth conditions among the multiple first terminal devices, the target terminal device may further select a first terminal device with the highest transmission quality with the target terminal device from the multiple first terminal devices that meet the fifth condition, and use the first terminal device as the second terminal device. In this way, it can be guaranteed that the transmission quality between the second terminal device and the target terminal device can meet the corresponding requirements, and it can also be guaranteed that the transmission quality between the second terminal device and the target terminal device among the multiple first terminal devices is the best.

[0267] Optionally, in another example, if there are multiple first terminal devices that all meet the fifth condition among the multiple first terminal devices, the target terminal device further selects, from among the multiple first terminal devices that meet the fifth condition, a first terminal device whose highest transmission quality with the target terminal device is below the 13th threshold, and the first terminal device may be used as the second terminal device. In this way, it can be guaranteed that the transmission quality between the second terminal device and the target terminal device can meet the corresponding requirements, and it is also possible to avoid the situation where there is no gain because the second terminal device is overly closed to the target terminal device.

[0268] Case 2: The fifth condition includes that there is an indirect path between the first terminal device and the target terminal device, and both the transmission quality between the first terminal device and the target terminal device and the transmission quality between the first terminal device and the source terminal device are greater than the seventh threshold.

[0269] The method by which the target terminal device obtains the transmission quality between the first terminal device and the source terminal device is not limited in this application. For example, the transmission quality between the first terminal device and the source terminal device may be predefined or pre-set (e.g., specified by a protocol). In another example, the first terminal device may notify the target terminal device of the transmission quality between the first terminal device and the source terminal device via a first message.

[0270] It should be noted that the transmission quality between the first terminal device and the source terminal device is the RSRP value, SINR value, RSRQ value, or RSSI value between the first terminal device and the source terminal device.

[0271] Optionally, in one example, if there are a plurality of first terminal devices that all meet the fifth condition among the plurality of first terminal devices, the target terminal device may further select, from the plurality of first terminal devices that meet the fifth condition, the first terminal device with the highest transmission quality with the target terminal device, and use the first terminal device as the second terminal device. In this way, it can be guaranteed that the transmission quality between the second terminal device and the target terminal device can meet the corresponding requirements, and it can also be guaranteed that the transmission quality between the second terminal device and the target terminal device among the plurality of first terminal devices is the best.

[0272] In this example, the first terminal device with the highest transmission quality with the target terminal device can be understood as having the highest transmission quality both between the first terminal device and the target terminal device and between the first terminal device and the source terminal device. Alternatively, the average value of the transmission quality between the first terminal device and the target terminal device and the average value of the transmission quality between the first terminal device and the source terminal device are both the largest.

[0273] In Case 2, it should be noted that when the fifth condition includes that there is an indirect path between the first terminal device and the target terminal device, and both the transmission quality between the first terminal device and the target terminal device and the transmission quality between the first terminal device and the source terminal device are greater than the seventh threshold, the non-existence of a first terminal device that meets the fifth condition among the plurality of first terminal devices can be understood as the transmission quality between each of the plurality of first terminal devices and the target terminal device being less than the seventh threshold, and / or the transmission quality between each of the plurality of first terminal devices and the source terminal device being less than the seventh threshold.

[0274] In addition, in Case 2, the fact that both the transmission quality between the first terminal device and the target terminal device and the transmission quality between the first terminal device and the source terminal device under the fifth condition are greater than the seventh threshold may be replaced with the fact that the transmission quality between the first terminal device and the target terminal device is equal to or greater than threshold value 1, and the transmission quality between the first terminal device and the source terminal device is equal to or greater than threshold value 2. In this case, the fact that there is no first terminal device satisfying the fifth condition among the plurality of first terminal devices may be understood as the transmission quality between each of the plurality of first terminal devices and the target terminal device being less than threshold value 1, and / or the transmission quality between each of the plurality of first terminal devices and the source terminal device being less than threshold value 2.

[0275] In Method A, first, the target terminal device preferentially selects, as the second terminal device, a first terminal device having a direct path to the target terminal device, and the transmission quality of the direct path satisfies the corresponding requirements. In this way, the transmission quality between the target terminal device and the second terminal device can be guaranteed. In addition, the delay of the communication between the target terminal device and the second terminal device can be further reduced. Thereby, the reliability of the subsequent communication between the source terminal device and the second terminal device is further guaranteed.

[0276] Second, the target terminal device may select, as the second terminal device, a first terminal device from among the indirect paths, provided that the transmission quality between the first terminal device and the target terminal device satisfies the corresponding requirements, or the transmission quality between the first terminal device and the target terminal device and the transmission quality between the first terminal device and the source terminal device satisfy the corresponding requirements. In this way, the transmission quality between the target terminal device and the second terminal device can be guaranteed, thereby guaranteeing the reliability of the subsequent communication between the source terminal device and the target terminal device via the second terminal device.

[0277] Finally, if the target terminal device has not yet selected a second terminal device that meets the corresponding requirements from the plurality of first terminal devices, the target terminal device may directly determine, as the second terminal device, a first terminal device that has a direct path to the target terminal device. In this way, the delay in communication between the target terminal device and the second terminal device can be reduced.

[0278] Method B: The target terminal device determines at least one second terminal device among the plurality of first terminal devices based on the second information.

[0279] The second information indicates whether a unicast connection is established between the first terminal device and the target terminal device.

[0280] Specifically, the target terminal device determining a plurality of second terminal devices among the plurality of first terminal devices based on the second information includes the target terminal device determining, as the second terminal device, a first terminal device that has established a unicast connection with the target terminal device among the plurality of first terminal devices. In other words, the target terminal device preferentially considers a first terminal device that establishes a unicast connection with the target terminal device. Then, the existing unicast connection between the second terminal device and the target terminal device can be multiplexed, thereby shortening the time for establishing a link between the second terminal device and the target terminal device and shortening the time for establishing a link between the source terminal device and the target terminal device.

[0281] Optionally, in one example, if there are a plurality of first terminal devices that establish a unicast connection with the target terminal device among the plurality of first terminal devices, the target terminal device may further consider another factor in addition to the second information to further select the second terminal device.

[0282] For example, another factor may include the transmission quality between the first terminal device and the target terminal device.

[0283] Specifically, the target terminal device may determine, as the second terminal device, a first terminal device whose transmission quality with the target terminal device is equal to or higher than an eighth threshold value and which has established a unicast connection with the target terminal device among a plurality of first terminal devices.

[0284] It should be noted that when the transmission quality between the first terminal device and the target terminal device is the RSRP value between the first terminal device and the target terminal device, since a unicast connection is established between the first terminal device and the target terminal device, the RSRP value between the first terminal device and the target terminal device may be referred to as a sidelink reference signal received power (SL-RSRP) value.

[0285] Method C: The target terminal device determines at least one second terminal device among a plurality of first terminal devices based on the first information and the second information.

[0286] For the related description of the first information, refer to the related description of Method A. Details will not be described again in this specification.

[0287] For the related description of the second information, refer to the related description of Method B. Details will not be described again in this specification.

[0288] Specifically, as shown in FIG. 6, the target terminal device determining a plurality of second terminal devices among a plurality of first terminal devices based on the first information and the second information includes the following steps.

[0289] S21: The target terminal device determines whether there are multiple first terminal devices that satisfy the third condition based on the first information.

[0290] For the related description of the third condition, please refer to the related description of Method A. Details will not be described again in this specification.

[0291] When there is a first terminal device that satisfies the third condition among the multiple first terminal devices, the first terminal device that satisfies the third condition is determined as the second terminal device.

[0292] Optionally, in one example, when there are multiple first terminal devices that all satisfy the third condition among the multiple first terminal devices, the target terminal device further selects, from the multiple first terminal devices that satisfy the third condition, a first terminal device whose transmission quality with the target terminal device is below the twelfth threshold, and the first terminal device may be used as the second terminal device. In this way, it can be guaranteed that the transmission quality between the first terminal device and the target terminal device can meet the corresponding requirements, and it can also avoid the situation where there is no gain because the first terminal device is too closed to the target terminal device.

[0293] When there is no first terminal device that satisfies the third condition among the multiple first terminal devices, in one example, the target terminal device executes S22. In another example, the target terminal device may execute S23. In other words, in this case, the target terminal device does not need to execute S22.

[0294] S22: The target terminal device determines whether there are multiple first terminal devices that satisfy the fourth condition based on the second information. The fourth condition includes that a unicast connection is established between the first terminal device and the target terminal device.

[0295] When there are multiple first terminal devices that satisfy the fourth condition, the target terminal device determines a first terminal device that satisfies the fourth condition as the second terminal device.

[0296] When there is no first terminal device that satisfies the fourth condition among the multiple first terminal devices, the target terminal device executes S23.

[0297] S23: The target terminal device determines the second terminal device among the multiple first terminal devices based on the fourth information.

[0298] Specifically, the target terminal device determines whether there are multiple first terminal devices that satisfy the fifth condition based on the fourth information.

[0299] When there are multiple first terminal devices that satisfy the fifth condition, the target terminal device determines a first terminal device that satisfies the fifth condition as the second terminal device.

[0300] When there is no first terminal device that satisfies the fifth condition among the multiple first terminal devices, the target terminal device executes S24.

[0301] Regarding the solution where the target terminal device determines whether there are multiple first terminal devices that satisfy the fifth condition in S23 based on the fourth information, please refer to the relevant description of S12. Details will not be described again in this specification.

[0302] In S23, when the transmission quality between the first terminal device of the fifth condition and the target terminal device is the RSRP value between the first terminal device and the target terminal device, since a unicast connection is not established between the first terminal device and the target terminal device, it should be noted that the RSRP value between the first terminal device and the target terminal device may be referred to as the sidelink discovery reference signal received power (SD-RSRP) value.

[0303] Optionally, in one example, when a plurality of second terminal devices are determined based on S23, the target terminal device may further determine a third terminal device among the plurality of second terminal devices and use the third terminal device as the final second terminal device.

[0304] In one example, the third terminal device is the terminal device with the highest transmission quality with the target terminal device among the plurality of second terminal devices. In other words, the target terminal device uses the terminal device with the highest transmission quality with the target terminal device among the plurality of second terminal devices as the final second terminal device.

[0305] In another example, the third terminal device is the terminal device with the highest transmission quality with both the target terminal device and the source terminal device among the plurality of second terminal devices. In other words, the target terminal device uses the terminal device with the highest transmission quality with both the target terminal device and the source terminal device among the plurality of second terminal devices as the final second terminal device.

[0306] S24: The target terminal device determines, as the second terminal device, the first terminal device that has a direct path to the target terminal device among the plurality of first terminal devices.

[0307] From S21 to S24, it can be found that the target terminal device preferentially selects a first terminal device having a direct path to the target terminal device as the second terminal device, and the transmission quality of the direct path meets the corresponding requirements. In this way, the transmission quality between the target terminal device and the second terminal device can be guaranteed. In addition, the communication delay between the target terminal device and the second terminal device can be further reduced. Thereby, the reliability of subsequent communication between the source terminal device and the target terminal device via the second terminal device is further guaranteed.

[0308] Next, the target terminal device selects a first terminal device that establishes a unicast connection with the target terminal device as the second terminal device. In this way, the existing unicast connection between the second terminal device and the target terminal device can be multiplexed, thereby shortening the time for establishing a link between the second terminal device and the target terminal device and shortening the time for establishing a link between the source terminal device and the target terminal device.

[0309] The target terminal device may select the first terminal device as the second terminal device from the indirect path, provided that the transmission quality between the first terminal device and the target terminal device meets the corresponding requirements, or the transmission quality between the first terminal device and the target terminal device and the transmission quality between the first terminal device and the source terminal device meet the corresponding requirements. In this way, the transmission quality between the target terminal device and the second terminal device can be guaranteed, thereby guaranteeing the reliability of subsequent communication between the source terminal device and the second terminal device.

[0310] If the target terminal device has not yet selected a second terminal device that meets the corresponding requirements from a plurality of first terminal devices, the target terminal device may directly determine, as the second terminal device, a first terminal device that has a direct path to the target terminal device. In this way, the delay in communication between the target terminal device and the second terminal device can be reduced.

[0311] In conclusion, based on S21 to S24, the priorities for the target terminal device to select the second terminal device from a plurality of first terminal devices in descending order are the direct path and the transmission quality of the direct path, the established unicast connection, and the indirect path and the transmission quality of the indirect path.

[0312] From S21, S23, and S24, it can be found that the target terminal device preferentially selects, as the second terminal device, a first terminal device that has a direct path to the target terminal device, and the transmission quality of the direct path meets the corresponding requirements. In this way, the transmission quality between the target terminal device and the second terminal device can be guaranteed. In addition, the delay in communication between the target terminal device and the second terminal device can be further reduced. Thereby, the reliability of subsequent communication between the source terminal device and the target terminal device via the second terminal device is further guaranteed.

[0313] The target terminal device may select, as the second terminal device, a first terminal device from the indirect path, provided that the transmission quality between the first terminal device and the target terminal device meets the corresponding requirements, or the transmission quality between the first terminal device and the target terminal device and the transmission quality between the first terminal device and the source terminal device meet the corresponding requirements. In this way, the transmission quality between the target terminal device and the second terminal device can be guaranteed, thereby guaranteeing the reliability of subsequent communication between the source terminal device and the second terminal device.

[0314] If the target terminal device has not yet selected a second terminal device that meets the corresponding requirements from a plurality of first terminal devices, the target terminal device may directly determine, as the second terminal device, a first terminal device that has a direct path to the target terminal device. In this way, the delay in communication between the target terminal device and the second terminal device can be reduced.

[0315] Based on S21, S23, and S24, the priority for the target terminal device to select the second terminal device from a plurality of first terminal devices in descending order is the direct path and the transmission quality of the direct path, as well as the indirect path and the transmission quality of the indirect path.

[0316] Method D: The target terminal device determines at least one second terminal device among a plurality of first terminal devices based on third information. The third information indicates the first QoS requirement of the source terminal device regarding the source terminal device and the target terminal device.

[0317] Specifically, the target terminal device determines, as the second terminal device, a first terminal device that meets the first QoS requirement among a plurality of first terminal devices.

[0318] The method by which the target terminal device obtains the first QoS requirement is not limited in this application.

[0319] In one example, the first QoS requirement may be predefined or preconfigured. For example, the first QoS requirement may be specified by a communication protocol.

[0320] In another example, the first QoS requirement may be notified to the target terminal device by the first terminal device. For example, the first terminal device may include the first QoS requirement in a first message. Then, the target terminal device can know the first QoS requirement.

[0321] Method E: The target terminal device determines the second terminal device among the plurality of first terminal devices based on the first information and the third information.

[0322] Specifically, the target terminal device determines, based on the first information and the third information, the first terminal device that satisfies both the third condition and the first QoS requirement among the plurality of first terminal devices as the second terminal device.

[0323] Note that the execution order of whether the target terminal device first selects the first terminal device that satisfies the third condition from among the plurality of first terminal devices or first selects the first terminal device that satisfies the first QoS requirement from among the plurality of first terminal devices is not limited in this application.

[0324] In one example, the target terminal device may first select the first terminal device that satisfies the third condition from among the plurality of first terminal devices, and then select the second terminal device from the first terminal devices that satisfy the third condition.

[0325] In another example, the target terminal device may first select the first terminal device that satisfies the first QoS requirement from among the plurality of first terminal devices, and then select the second terminal device from the first terminal devices that satisfy the third condition.

[0326] Regarding the solution for selecting the first terminal device that satisfies the third condition from among the plurality of first terminal devices, please refer to the related description of Method A. Regarding the solution for selecting the first terminal device that satisfies the first QoS requirement from among the plurality of first terminal devices, please refer to the related description of Method D.

[0327] Method F: The target terminal device determines the second terminal device among the plurality of first terminal devices based on the second information and the third information.

[0328] Specifically, the target terminal device determines, based on the second information and the third information, a first terminal device that meets the first QoS requirement among a plurality of first terminal devices that have established a unicast connection with the target terminal device as the second terminal device.

[0329] It should be noted that the execution order of whether the target terminal device first selects a first terminal device that has established a unicast connection with the target terminal device from among a plurality of first terminal devices, or first selects a first terminal device that meets the first QoS requirement from among a plurality of first terminal devices is not limited in this application.

[0330] Regarding the solution for the method of selecting a first terminal device that has established a unicast connection with the target terminal device from among a plurality of first terminal devices, refer to the related description of Method B. Regarding the solution for the method of selecting a first terminal device that meets the first QoS requirement from among a plurality of first terminal devices, refer to the related description of Method D.

[0331] Method G: The target terminal device determines a second terminal device among a plurality of first terminal devices based on the first information, the second information, and the third information.

[0332] Specifically, the target terminal device determines, based on the first information, the second information, and the third information, a first terminal device that meets both the third condition and the first QoS requirement among a plurality of first terminal devices that have established a unicast connection with the target terminal device as the second terminal device.

[0333] Note that the execution order of whether the target terminal device first selects a first terminal device that satisfies the third condition from a plurality of first terminal devices, or first selects a first terminal device that has established a unicast connection with the target terminal device from a plurality of first terminal devices, or first selects a first terminal device that satisfies the first QoS requirement from a plurality of first terminal devices is not limited in this application.

[0334] Regarding the solution for selecting a first terminal device that satisfies the third condition from among a plurality of first terminal devices, please refer to the relevant description of Method A. Regarding the solution for selecting a first terminal device that has established a unicast connection with the target terminal device from a plurality of first terminal devices, please refer to the relevant description of Method B. Regarding the solution for selecting a first terminal device that satisfies the first QoS requirement from a plurality of first terminal devices, please refer to the relevant description of Method D.

[0335] S403: The target terminal device sends a second message to at least one second terminal device.

[0336] The second message indicates that the target terminal device has been discovered, and the second message includes the identifier of the target terminal device.

[0337] Optionally, the target terminal device may further send a message used to reject the discovery of the target terminal device to a first terminal device other than at least one second terminal device among the plurality of first terminal devices, or the target terminal device may not respond to the message (for example, do not perform any operation).

[0338] Whether the target terminal device in the foregoing description of method 400 supports UE-to-UE relay technology, in other words, whether the target terminal device is a legacy device (legacy UE), is not limited in the present embodiment of the present application.

[0339] Optionally, in an embodiment where the target terminal device does not support UE-to-UE relay technology, in other words, the target terminal device is a legacy device (legacy UE). In order to prevent an error from occurring in the process of the source terminal device continuously exchanging information with the target terminal device via the established unicast connection, after executing S401, the target terminal device first executes S404, and based on the determination result of S404, determines whether to execute S403 (the foregoing method 400 includes only S401 and S403 and does not include S402), or whether to execute S402 and S403 (the foregoing method 400 includes S401 to S403). S404 will be described in detail below.

[0340] S404: The target terminal device determines whether to accept each first message based on each first message.

[0341] In one example, when the target terminal device confirms that the parameters carried in the first message include unknown parameters, the target terminal device determines not to accept the first message. Alternatively, when the target terminal device confirms that all the parameters carried in the first message are known parameters, the target terminal device determines to accept the first message.

[0342] For example, the RSC included in the first message is an RSC after R18, or the first message carries parameters newly added in a version after R18. In this case, the parameters carried in the first message may be regarded as including parameters unknown to the target terminal device.

[0343] In another example, when the target terminal device confirms that the first message has been relayed by a relay device, in other words, that the first terminal device is a relay device, the target terminal device decides not to accept the first message. Alternatively, when the target terminal device confirms that the first message has not been relayed by a relay device and is directly transmitted by the source terminal device, in other words, that the first terminal device is the source terminal device, the target terminal device decides to accept the first message.

[0344] For example, when the target terminal device confirms that, in addition to the identifier of the first terminal device and the identifier of the target terminal device, the first message further carries the identifier of another terminal device (for example, the identifier of the source terminal device), the target terminal device may regard the first message as being relayed by a relay device (that is, the first terminal device).

[0345] When the target terminal device confirms that the first message carries the identifier of the first terminal device and the identifier of the target terminal device and does not carry the identifier of another terminal device, the target terminal device may regard the first message as not being relayed by a relay device and being directly transmitted by the source terminal device (that is, the first terminal device).

[0346] Optionally, if the target terminal device determines not to accept the first message, the target terminal device may further send a message to the first terminal device that sends the first message, which is used to reject discovering the target terminal device; or the target terminal device may ignore the first terminal device that sent the first message / not respond to the first terminal device that sent the first message (e.g., do not perform any operation). Optionally, if the target terminal device determines to accept the first message, in the foregoing embodiment where method 400 includes only S401 and S403 and does not include S402, the target terminal device may directly execute S403. In this case, the fourth terminal device in S403 is the first terminal device that sends the first message.

[0347] Optionally, if the target terminal device determines to accept the first message, in the foregoing embodiment where method 400 includes S401 to S403, the target terminal device may directly execute S402. In this case, the first terminal device in S402 is the first terminal device that sends the first message.

[0348] It should be noted that if the target terminal device is R18 or later, the target terminal device may be considered to support UE-to-UE relay technology. It should be noted that if the target terminal device is before R17, the target terminal device may be considered not to support UE-to-UE relay technology.

[0349] The source terminal device can also usually receive a plurality of response messages. For example, the source terminal device directly receives a request message sent by the target terminal device and / or receives a request response sent by the target terminal device via the relay terminal device. In this case, in order to ensure the reliability of unicast communication between the source terminal device and the target terminal device, the source terminal device in the embodiments of the present application selects at least one transmission entity from a plurality of transmission entities that transmit a plurality of response messages to implement the communication process between the source terminal device and the target terminal device, and can establish a unicast connection with the transmission entity.

[0350] Whether a plurality of response messages are directly sent by the target terminal device to the source terminal device or are sent by the target terminal device to the source terminal device via the relay device is not limited in the embodiments of the present application.

[0351] Referring to FIG. 7, hereinafter, an example in which the source terminal device receives a third message sent by a plurality of second terminal devices is used to illustrate how the source terminal device selects at least one transmission entity from a plurality of transmission entities that transmit a plurality of request messages.

[0352] FIG. 7 is a schematic flowchart of a communication method 500 according to an embodiment of the present application.

[0353] For example, as shown in FIG. 7, the communication method 500 includes S501 to S503. Hereinafter, S501 to S503 will be described in detail.

[0354] S501: The source terminal device receives a third message from each of a plurality of second terminal devices.

[0355] The third message indicates that the target terminal device has been discovered. The third message includes the identifier of the second terminal device, or the third message includes the identifier of the second terminal device and the identifier of the target terminal device.

[0356] Optionally, in some embodiments, the third message may further include the identifier of the source terminal device.

[0357] S502: The source terminal device determines the fourth terminal device among the plurality of second terminal devices.

[0358] Hereinafter, as an example, S502 will be described in detail using Method A' to Method C'.

[0359] Method A': The source terminal device determines the fourth terminal device among the plurality of first terminal devices based on the sixth information.

[0360] The sixth information indicates the direct or indirect path between the second terminal device and the source terminal device, and the transmission quality between the second terminal device and the source terminal device.

[0361] In one example, the transmission quality between the second terminal device and the source terminal device may be obtained by the source terminal device via the third message being currently transmitted.

[0362] The type of the transmission quality between the second terminal device and the source terminal device is not limited in this embodiment of the present application. For example, the transmission quality between the second terminal device and the source terminal device may be the RSRP value obtained by the source terminal device by measuring the RSRP of the third message. Additionally, the second terminal device and the source terminal device may alternatively be the SINR value, RSRQ value, or RSSI value of the third message.

[0363] In another example, the transmission quality between the second terminal device and the source terminal device may be obtained by the source terminal device via the history information transmitted between the source terminal device and the second terminal device.

[0364] For example, if the third message carries only the identifier of the second terminal device, or only the identifier of the second terminal device and the identifier of the source terminal device, and does not carry the identifier of another terminal device, a direct path may be considered to exist between the second terminal device and the source terminal device. In other words, the second terminal device is the target terminal device. If the third message further carries the identifier of the target terminal device in addition to the identifier of the second terminal device, or in addition to the identifier of the second terminal device and the identifier of the source terminal device, an indirect path may be considered to exist between the second terminal device and the source terminal device. In other words, the second terminal device is a relay device.

[0365] Specifically, the target terminal device determining the fourth terminal device among the plurality of first terminal devices based on the sixth information includes the following steps.

[0366] S11’: The source terminal device determines, based on the sixth information, whether a fourth terminal device that satisfies the sixth condition exists among the plurality of second terminal devices. The sixth condition includes that there is a direct path between the second terminal device and the source terminal device, and the transmission quality between the second terminal device and the source terminal device is equal to or higher than the ninth threshold.

[0367] When a second terminal device that satisfies the sixth condition exists among the plurality of second terminal devices, the source terminal device determines the second terminal device that satisfies the sixth condition as the fourth terminal device.

[0368] Optionally, in one example, if there are multiple second terminal devices that all meet the sixth condition among the multiple second terminal devices, the source terminal device may further select, from the multiple second terminal devices that meet the sixth condition, the second terminal device with the highest transmission quality with respect to the source terminal device, and use the second terminal device as the fourth terminal device. In this way, it can be guaranteed that the transmission quality between the fourth terminal device and the source terminal device can meet the corresponding requirements, and it can also be guaranteed that the transmission quality between the fourth terminal device and the source terminal device among the multiple second terminal devices is the best.

[0369] When there is no second terminal device that meets the sixth condition among the multiple second terminal devices, the source terminal device executes S12’.

[0370] S12’: The source terminal device determines the fourth terminal device among the multiple second terminal devices based on the eighth information.

[0371] Specifically, the source terminal device determines, based on the eighth information, whether there is a fourth terminal device that meets the eighth condition among the multiple second terminal devices.

[0372] When there is a second terminal device that meets the eighth condition among the multiple second terminal devices, the source terminal device determines the second terminal device that meets the eighth condition as the fourth terminal device.

[0373] When there is no second terminal device that meets the eighth condition among the multiple second terminal devices, the source terminal device determines, among the multiple second terminal devices, the second terminal device that has a direct path to the source terminal device as the fourth terminal device.

[0374] Hereinafter, S12’ will be described in detail using an example where the eighth information and the eighth condition are Case 1’, and an example where the eighth information and the eighth condition are Case 2’.

[0375] Case 1’: The eighth piece of information includes the transmission quality between the second terminal device and the source terminal device. The tenth condition includes that there is an indirect path between the second terminal device and the source terminal device, and the transmission quality between the second terminal device and the source terminal device is equal to or higher than a tenth threshold value. The tenth threshold value is greater than the ninth threshold value.

[0376] Optionally, in one example, if there are a plurality of second terminal devices that all meet the sixth condition among the plurality of second terminal devices, the source terminal device may further select, from the plurality of second terminal devices that meet the sixth condition, the second terminal device with the highest transmission quality with the source terminal device, and use the second terminal device as the fourth terminal device. In this way, it can be guaranteed that the transmission quality between the fourth terminal device and the source terminal device can meet the corresponding requirements, and it can also be guaranteed that the transmission quality between the fourth terminal device and the source terminal device among the plurality of second terminal devices is the best.

[0377] Optionally, in another example, if there are a plurality of second terminal devices that all meet the sixth condition among the plurality of second terminal devices, the source terminal device may further select, from the plurality of second terminal devices that meet the sixth condition, the second terminal device with a transmission quality equal to or lower than a fifteenth threshold value with the source terminal device, and use the second terminal device as the fourth terminal device. In this way, it can be guaranteed that the transmission quality between the fourth terminal device and the source terminal device can meet the corresponding requirements, and it can also avoid the case where there is no gain because the fourth terminal device is overly closed to the source terminal device.

[0378] Case 2': The eighth piece of information includes the transmission quality between the second terminal device and the target terminal device and the transmission quality between the second terminal device and the source terminal device. The eighth condition includes that there is an indirect path between the second terminal device and the source terminal device, and both the transmission quality between the second terminal device and the target terminal device and the transmission quality between the second terminal device and the source terminal device are greater than the eleventh threshold value.

[0379] The method by which the source terminal device obtains the transmission quality between the second terminal device and the target terminal device is not limited in this application. For example, the transmission quality between the second terminal device and the target terminal device may be predefined or preset (for example, specified by a protocol). In another example, the second terminal device may notify the source terminal device of the transmission quality between the second terminal device and the target terminal device via a third message.

[0380] It should be noted that the transmission quality between the second terminal device and the target terminal device is the RSRP value, SINR value, RSRQ value, or RSSI value between the second terminal device and the target terminal device.

[0381] Optionally, in one example, if there are multiple second terminal devices that all meet the eighth condition among the multiple second terminal devices, the source terminal device may further select, from the multiple second terminal devices that meet the eighth condition, the second terminal device with the highest transmission quality with the source terminal device, and use the second terminal device as the fourth terminal device. In this way, it can be guaranteed that the transmission quality between the fourth terminal device and the source terminal device can meet the corresponding requirements, and it can also be guaranteed that the transmission quality between the fourth terminal device and the source terminal device among the multiple second terminal devices is the best.

[0382] In this example, it can be understood that the second terminal device with the highest transmission quality with the source terminal device has the highest transmission quality both between the second terminal device and the target terminal device and between the second terminal device and the source terminal device. Alternatively, both the average value of the transmission quality between the second terminal device and the target terminal device and the average value of the transmission quality between the second terminal device and the source terminal device are the maximum.

[0383] In case 2', the eighth condition includes that there is an indirect path between the second terminal device and the source terminal device. When both the transmission quality between the second terminal device and the target terminal device and the transmission quality between the second terminal device and the source terminal device are greater than the eleventh threshold, the absence of a second terminal device that satisfies the eighth condition among the plurality of second terminal devices may be understood as that the transmission quality between each of the plurality of second terminal devices and the target terminal device is less than the eleventh threshold, and / or the transmission quality between each of the plurality of second terminal devices and the source terminal device is less than the eleventh threshold. It should be noted.

[0384] In addition, in case 2', the fact that both the transmission quality between the second terminal device and the target terminal device and the transmission quality between the second terminal device and the source terminal device in the eighth condition are greater than the eleventh threshold may be replaced by the fact that the transmission quality between the second terminal device and the target terminal device is 3 or more, and the transmission quality between the second terminal device and the source terminal device is 4 or more. In this case, the absence of a second terminal device that satisfies the eighth condition among the plurality of second terminal devices may be understood as that the transmission quality between each of the plurality of second terminal devices and the target terminal device is less than 3, and / or the transmission quality between each of the plurality of second terminal devices and the source terminal device is less than 4.

[0385] In the foregoing method A', first, the source terminal device preferentially selects, as the fourth terminal device, a second terminal device having a direct path to the source terminal device, and the transmission quality of the direct path meets the corresponding requirements. In this way, the transmission quality between the source terminal device and the fourth terminal device can be guaranteed. In addition, the communication delay between the source terminal device and the fourth terminal device can be further reduced. Thereby, the reliability of subsequent communication between the source terminal device and the fourth terminal device is further guaranteed.

[0386] Second, the source terminal device selects, as the fourth terminal device, a second terminal device from the indirect paths, and determines whether the transmission quality between the second terminal device and the source terminal device meets the corresponding requirements, or whether the transmission quality between the second terminal device and the source terminal device and the transmission quality between the second terminal device and the target terminal device meet the corresponding requirements. In this way, the transmission quality between the source terminal device and the fourth terminal device can be guaranteed, thereby guaranteeing the reliability of subsequent communication between the source terminal device and the source terminal device via the fourth terminal device.

[0387] Finally, if the source terminal device has not yet selected, as the fourth terminal device, a second terminal device that meets the corresponding requirements from among a plurality of second terminal devices, the source terminal device can directly determine, as the fourth terminal device, a second terminal device having a direct path to the source terminal device. In this way, the communication delay between the source terminal device and the fourth terminal device can be reduced.

[0388] Method B': The source terminal device determines the fourth terminal device among a plurality of second terminal devices based on the seventh information.

[0389] The seventh information indicates whether a unicast connection is established between the second terminal device and the source terminal device.

[0390] Specifically, the source terminal device determining the fourth terminal device among the plurality of second terminal devices based on the seventh information includes the source terminal device determining whether there is a second terminal device that satisfies the seventh condition among the plurality of second terminal devices based on the seventh information. The seventh condition includes that a unicast connection is established between the second terminal device and the source terminal device. In other words, the source terminal device preferentially considers the second terminal device that establishes a unicast connection with the source terminal device. Subsequently, the existing unicast connection between the fourth terminal device and the source terminal device can be multiplexed, thereby shortening the time for establishing a link between the fourth terminal device and the target terminal device and shortening the time for establishing a link between the source terminal device and the target terminal device.

[0391] Optionally, in one example, when there are a plurality of second terminal devices that establish a unicast connection with the source terminal device among the plurality of second terminal devices, the source terminal device may further consider another factor in addition to the seventh information to further select the fourth terminal device.

[0392] For example, another factor may include the transmission quality between the second terminal device and the source terminal device.

[0393] Specifically, the source terminal device can determine, as the fourth terminal device, the second terminal device that has established a unicast connection with the source terminal device among the plurality of second terminal devices and whose transmission quality with the source terminal device is equal to or higher than the twelfth threshold.

[0394] It should be noted that when the transmission quality between the second terminal device and the source terminal device is the RSRP value between the second terminal device and the source terminal device, since a unicast connection is established between the second terminal device and the source terminal device, the RSRP value between the second terminal device and the source terminal device may be called the SL-RSRP value.

[0395] Method C’: The source terminal device determines the fourth terminal device among the plurality of second terminal devices based on the sixth information and the seventh information.

[0396] For the related description of the sixth information, please refer to the related description of Method A’. Details will not be described again in this specification.

[0397] For the related description of the seventh information, please refer to the related description of Method B’. Details will not be described again in this specification.

[0398] Specifically, as shown in FIG. 7, the source terminal device determines the fourth terminal device among the plurality of second terminal devices based on the sixth information and the seventh information, which includes the following steps.

[0399] S21’: The source terminal device determines whether there is a fourth terminal device that satisfies the sixth condition among the plurality of second terminal devices based on the sixth information.

[0400] For the related description of the sixth condition, please refer to the related description of Method A’. Details will not be described again in this specification.

[0401] When there are a plurality of second terminal devices that satisfy the sixth condition among the plurality of second terminal devices, the source terminal device determines the second terminal device that satisfies the sixth condition as the fourth terminal device.

[0402] Optionally, in one example, if there are multiple second terminal devices that all meet the sixth condition among the multiple second terminal devices, the source terminal device further selects, from the multiple first terminal devices that meet the sixth condition, a second terminal device whose transmission quality with the source terminal device is below the 14th threshold value, and the second terminal device may be used as the fourth terminal device. In this way, it can be guaranteed that the transmission quality between the fourth terminal device and the source terminal device can meet the corresponding requirements, and it is also possible to avoid the situation where there is no gain because the fourth terminal device is overly closed to the source terminal device.

[0403] When there is no second terminal device that meets the sixth condition among the multiple second terminal devices, in one example, the source terminal device executes S22’. In another example, the source terminal device may execute S23’. In other words, in this case, the source terminal device does not need to execute S22’.

[0404] S22’: The source terminal device determines, based on the seventh information, whether there is a second terminal device that meets the seventh condition among the multiple second terminal devices.

[0405] For the related description of the seventh condition, please refer to the related description of method B’. Details will not be described again in this specification.

[0406] When there is a second terminal device that meets the seventh condition among the multiple second terminal devices, the source terminal device determines the second terminal device that meets the seventh condition as the fourth terminal device.

[0407] When there is no second terminal device that meets the seventh condition among the multiple second terminal devices, the source terminal device executes S23’.

[0408] S23’: The source terminal device determines the fourth terminal device among the multiple second terminal devices based on the eighth information.

[0409] Specifically, the source terminal device determines, based on the eighth piece of information, whether there are second terminal devices that satisfy the eighth condition among a plurality of first terminal devices.

[0410] When there are second terminal devices that satisfy the eighth condition among a plurality of second terminal devices, the source terminal device determines the second terminal device that satisfies the eighth condition as the fourth terminal device.

[0411] When there are no second terminal devices that satisfy the eighth condition among a plurality of second terminal devices, the source terminal device executes S24'.

[0412] Regarding the solution in which the source terminal device determines, based on the eighth piece of information, whether there is a second terminal device that satisfies the eighth condition among a plurality of second terminal devices in S23', refer to the related description of S12'. Details are not described again in this specification.

[0413] In S23', when the transmission quality between the second terminal device and the source terminal device in the eighth condition is the RSRP value between the second terminal device and the source terminal device, note that since no unicast connection is established between the second terminal device and the source terminal device, the RSRP value between the second terminal device and the source terminal device may be called the SD-RSRP value.

[0414] Optionally, in one example, when a plurality of fourth terminal devices are determined based on S23', the source terminal device may further determine a fifth terminal device among the plurality of fourth terminal devices and use the fifth terminal device as the final fourth terminal device.

[0415] In one example, the fifth terminal device is the terminal device with the highest transmission quality with the target terminal device among the plurality of fourth terminal devices. In other words, the source terminal device uses, as the final fourth terminal device, the terminal device with the highest transmission quality with the source terminal device among the plurality of fourth terminal devices.

[0416] In another example, the fifth terminal device is the terminal device with the highest transmission quality with both the target terminal device and the source terminal device among the plurality of fourth terminal devices. In other words, the source terminal device uses, as the final fourth terminal device, the terminal device with the highest transmission quality with both the source terminal device and the target terminal device among the plurality of fourth terminal devices.

[0417] S24’: The source terminal device determines, as the fourth terminal device, the second terminal device having a direct path to the source terminal device among the plurality of second terminal devices.

[0418] From S21’ to S24’, it can be found that the source terminal device preferentially selects, as the fourth terminal device, the second terminal device having a direct path to the source terminal device, and the transmission quality of the direct path meets the corresponding requirements. In this way, the transmission quality between the source terminal device and the fourth terminal device can be guaranteed. In addition, the delay of communication between the source terminal device and the fourth terminal device can be further reduced. Thereby, the reliability of subsequent communication between the source terminal device and the fourth terminal device is further guaranteed.

[0419] Next, the source terminal device selects a second terminal device that establishes a unicast connection with the source terminal device as the fourth terminal device. In this way, the existing unicast connection between the fourth terminal device and the source terminal device can be multiplexed, thereby shortening the time for establishing a link between the fourth terminal device and the source terminal device and shortening the time for establishing a link between the source terminal device and the target terminal device.

[0420] The source terminal device selects a second terminal device from an indirect path as the fourth terminal device, and determines whether the transmission quality between the second terminal device and the source terminal device meets the corresponding requirements, or whether the transmission quality between the second terminal device and the source terminal device and the transmission quality between the second terminal device and the source terminal device meet the corresponding requirements. In this way, the transmission quality between the source terminal device and the fourth terminal device can be guaranteed, thereby guaranteeing the reliability of subsequent communication between the source terminal device and the source terminal device via the fourth terminal device.

[0421] If the source terminal device has not yet selected a fourth terminal device that meets the corresponding requirements from a plurality of second terminal devices, the source terminal device may directly determine a second terminal device having a direct path to the source terminal device as the fourth terminal device. In this way, the communication delay between the source terminal device and the fourth terminal device can be reduced.

[0422] In conclusion, based on S21’~S24’, the priorities for the source terminal device to select the fourth terminal device from a plurality of second terminal devices in descending order are the direct path and the transmission quality of the direct path, the established unicast connection, and the indirect path and the transmission quality of the indirect path.

[0423] From S21’, S23’, and S24’, it can be found that the source terminal device preferentially selects, as the fourth terminal device, a second terminal device having a direct path to the source terminal device, and the transmission quality of the direct path can meet the corresponding requirements. In this way, the transmission quality between the source terminal device and the fourth terminal device can be guaranteed. In addition, the communication delay between the source terminal device and the fourth terminal device can be further reduced. Thereby, the reliability of subsequent communication between the source terminal device and the fourth terminal device is further guaranteed.

[0424] The source terminal device selects, as the fourth terminal device, a second terminal device from the indirect path, and whether the transmission quality between the second terminal device and the source terminal device meets the corresponding requirements, or the transmission quality between the second terminal device and the source terminal device and the transmission quality between the second terminal device and the source terminal device meet the corresponding requirements. In this way, the transmission quality between the source terminal device and the fourth terminal device can be guaranteed, thereby guaranteeing the reliability of subsequent communication between the source terminal device and the source terminal device via the fourth terminal device.

[0425] If the source terminal device has not yet selected, as the fourth terminal device, a second terminal device that meets the corresponding requirements from a plurality of second terminal devices, the source terminal device can directly determine, as the fourth terminal device, a second terminal device having a direct path to the source terminal device. In this way, the communication delay between the source terminal device and the fourth terminal device can be reduced.

[0426] Based on S21’, S23’, and S24’, the priorities for the target terminal device to select the fourth terminal device from a plurality of second terminal devices in descending order are the direct path and the transmission quality of the direct path, and the indirect path and the transmission quality of the indirect path.

[0427] S503: The source terminal device establishes a unicast connection to the target terminal device via the fourth terminal device.

[0428] Optionally, in some embodiments, there is one fourth terminal device, there is a direct path between the fourth terminal device and the source terminal device, and if a unicast connection is not established between the fourth terminal device and the source terminal device, the source terminal device directly establishes a unicast connection to the second terminal device. In this embodiment, the fourth terminal device may be regarded as the target terminal device.

[0429] Optionally, in some embodiments, there is one fourth terminal device, there is an indirect path between the fourth terminal device and the source terminal device, and if a unicast connection is not established between the fourth terminal device and the source terminal device, the source terminal device first establishes a unicast connection to the fourth terminal device. Then, the fourth terminal device establishes a unicast connection to the target terminal device. Further, the source terminal device communicates with the target terminal device via the second terminal device. In this embodiment, the fourth terminal device may be regarded as the first relay device described above.

[0430] Optionally, in some further embodiments, there is one fourth terminal device, there is a direct path between the fourth terminal device and the source terminal device, and if a unicast connection is established between the fourth terminal device and the source terminal device, the fourth terminal device need not establish a unicast connection with the source terminal device and may communicate directly with the source terminal device. In this embodiment, the fourth terminal device may be regarded as the target terminal device.

[0431] Optionally, in some further embodiments, there is a fourth terminal device, there is an indirect path between the fourth terminal device and the source terminal device, and when a unicast connection is established between the fourth terminal device and the source terminal device, the fourth terminal device does not need to establish a unicast connection with the source terminal device, and the fourth terminal device directly establishes a unicast connection to the target terminal device. In this way, the source terminal device communicates with the target terminal device via the fourth terminal device. In this embodiment, the fourth terminal device may be regarded as the first relay device described above.

[0432] It should be noted that at least two of the above-described method 300, method 400, and method 500 may be implemented in combination or separately. This is not limited in the embodiments of this application.

[0433] The communication device provided in the embodiments of this application will be described in detail below with reference to FIGS. 8 and 9.

[0434] FIG. 8 is a diagram of the structure of a communication device 800 according to an embodiment of this application.

[0435] For example, as shown in FIG. 8, the communication device 800 includes a transceiver unit 810 and a processing unit 820.

[0436] The transceiver unit 810 may communicate with the outside. The transceiver unit 810 may also be called a communication interface or a communication unit. The processing unit 820 is configured to process data.

[0437] Optionally, the communication device 800 may further include a storage unit. The storage unit may be configured to store instructions and / or data. The processing unit 820 may read the instructions and / or data in the storage unit.

[0438] In one implementation form, the communication device 800 may be configured to execute the operations executed by the execution entity in the aforementioned method 300.

[0439] In one example, the communication device 800 may be a source terminal device or a component that can be configured as a source terminal device. The transceiver unit 810 is configured to execute reception / transmission related operations on the source terminal device side in the method 300, and the processing unit 820 is configured to execute processing related operations on the source terminal device side in the method 300.

[0440] In another example, the communication device 800 may be a first relay device or a component that can be configured as a first relay device. The transceiver unit 810 is configured to execute reception / transmission related operations on the first relay device side in the method 300, and the processing unit 820 is configured to execute processing related operations on the first relay device side in the method 300.

[0441] In yet another example, the communication device 800 may be a target terminal device or a component that can be configured as a target terminal device. The transceiver unit 810 is configured to execute reception / transmission related operations on the target terminal device side in the method 300, and the processing unit 820 is configured to execute processing related operations on the target terminal device side in the method 300.

[0442] In another implementation form, the communication device 800 may be configured to execute the operations executed by the execution entity in the aforementioned method 500.

[0443] In one example, the communication device 800 may be a first terminal device or a component that can be configured as a first terminal device. The transceiver unit 810 is configured to execute reception / transmission related operations on the first terminal device side in the method 400, and the processing unit 820 is configured to execute processing related operations on the first terminal device side in the method 400.

[0444] In another example, the communication device 800 can be a second terminal device or a component that can be configured as a second terminal device. The transceiver unit 810 is configured to perform reception / transmission related operations on the second terminal device side in method 400, and the processing unit 820 is configured to perform processing related operations on the second terminal device side in method 400.

[0445] In yet another example, the communication device 800 can be a target terminal device or a component that can be configured as a target terminal device. The transceiver unit 810 is configured to perform reception / transmission related operations on the target terminal device side in method 400, and the processing unit 820 is configured to perform processing related operations on the target terminal device side in method 400.

[0446] In yet another implementation, the communication device 800 can be configured to perform the operations executed by the executor in the aforementioned method 500.

[0447] In one example, the communication device 800 can be a second terminal device or a component that can be configured as a second terminal device. The transceiver unit 810 is configured to perform reception / transmission related operations on the second terminal device side in method 500, and the processing unit 820 is configured to perform processing related operations on the second terminal device side in method 500.

[0448] In another example, the communication device 800 can be a source terminal device or a component that can be configured as a source terminal device. The transceiver unit 810 is configured to perform reception / transmission related operations on the source terminal device side in method 500, and the processing unit 820 is configured to perform processing related operations on the source terminal device side in method 500.

[0449] In yet another example, the communication device 800 can be a fourth terminal device or a component that can be configured as a fourth terminal device. The transceiver unit 810 is configured to perform reception / transmission related operations on the side of the fourth terminal device in method 500, and the processing unit 820 is configured to perform processing related operations on the side of the fourth terminal device in method 500.

[0450] FIG. 9 is a diagram of the structure of a communication device 900 according to an embodiment of the present application.

[0451] As shown in FIG. 9, the communication device 900 includes one or more processors 910 and one or more memories 920. The one or more memories 920 store one or more computer programs, and the one or more computer programs include instructions.

[0452] In one example, the communication device 900 can be a source terminal device, a first relay device, or a target terminal device in method 300. In this case, when the instructions in the communication device 900 are operated by one or more processors 910, the communication device 900 is enabled to execute the technical solutions executed by the source terminal device, the first relay device, or the target terminal device in method 300.

[0453] In another example, the communication device 900 can be a first terminal device, a second terminal device, or a target terminal device in the aforementioned method 400. In this case, when the instructions in the communication device 900 are operated by one or more processors 910, the communication device 900 is enabled to execute the technical solutions executed by the first terminal device, the second terminal device, or the target terminal device in method 400.

[0454] In yet another example, the communication device 900 may be the second terminal device, the source terminal device, or the fourth terminal device in the aforementioned method 500. In this case, when the instructions in the communication device 900 are operated by one or more processors 910, the communication device 900 is enabled to execute the technical solution executed by the second terminal device, the source terminal device, or the fourth terminal device in the method 500.

[0455] One embodiment of the present application provides a communication system including a source terminal device, a first relay device, and a target terminal device. The system is configured to execute the technical solution of the aforementioned method 300. The implementation principle and technical effect thereof are the same as those of the embodiments related to the aforementioned method. Details are not described again in this specification.

[0456] One embodiment of the present application provides a communication system including a first terminal device, a second terminal device, and a target terminal device. The system is configured to execute the technical solution of the aforementioned method 400. The implementation principle and technical effect thereof are the same as those of the embodiments related to the aforementioned method. Details are not described again in this specification.

[0457] One embodiment of the present application provides a communication system including a second terminal device, a source terminal device, and a fourth terminal device. The system is configured to execute the technical solution of the aforementioned method 500. The implementation principle and technical effect thereof are the same as those of the embodiments related to the aforementioned method. Details are not described again in this specification.

[0458] One embodiment of this application provides a computer program product. When the computer program product operates on a device, the device is enabled to implement the technical solutions of the foregoing embodiments. The implementation principle and technical effects are the same as those of the foregoing method-related embodiments. Details are not described again herein. In one example, the device may include the source terminal device, the first relay device, or the target terminal device in the foregoing method 300. In another example, the device may include the first terminal device, the second terminal device, or the target terminal device in the foregoing method 400. In still another example, the device may include the second terminal device, the source terminal device, or the fourth terminal device in the foregoing method 500.

[0459] One embodiment of this application provides a computer-readable storage medium. The readable storage medium includes instructions. When the instructions are operated on a device, the device is enabled to implement the technical solutions of the foregoing embodiments. The implementation principle and technical effects are the same. Details are not described again herein. In one example, the device may include the source terminal device, the first relay device, or the target terminal device in the foregoing method 300. In another example, the device may include the first terminal device, the second terminal device, or the target terminal device in the foregoing method 400. In still another example, the device may include the second terminal device, the source terminal device, or the fourth terminal device in the foregoing method 500.

[0460] One embodiment of this application provides a chip. The chip is configured to execute instructions. When the chip operates, the technical solutions of the foregoing embodiments are executed. The implementation principle and technical effects are the same. Details are not described again herein.

[0461] Those skilled in the art can recognize that the units and algorithm steps in the examples described in combination with the embodiments disclosed in this specification can be implemented by electronic hardware or a combination of computer software and electronic hardware. Whether a function is executed by hardware or by software depends on the specific application of the technical solution and the design constraints. Those skilled in the art may use different methods to implement the described functions for each specific application, but the implementation form should not be considered to exceed the scope of the embodiments of this application.

[0462] For the purpose of simplifying the description, it can be clearly understood by those skilled in the art to refer to the corresponding processes in the embodiments of the foregoing method for the detailed working processes of the foregoing systems, devices, and units. Details are not described again in this specification.

[0463] In some embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the described device embodiments are only examples. For example, the division into units is only a logical function division, and there may be other divisions in actual implementation forms. For example, a plurality of units or components may be combined or integrated into another system, or some features may be ignored or not executed. In addition, the presented or described mutual coupling, direct coupling, or communication connection may also be implemented through some interfaces. The indirect coupling or communication connection between devices or units may be implemented in electronic form, mechanical form, or other forms.

[0464] The units described as separate parts may or may not be physically separate, and the parts presented as units may or may not be physical units, i.e., they may be arranged in one location or may be distributed across multiple network units. Some or all of the units may be selected based on actual requirements to achieve the objectives of the solutions of the embodiments.

[0465] In addition, the functional units of the embodiments of the present application may be integrated into one processing unit, each unit may exist physically alone, or two or more units may be integrated into one unit.

[0466] When functions are realized in the form of software functional units and are sold or used as independent products, those functions may be stored in a computer-readable storage medium. Based on such understanding, the technical solutions of the present application, in essence, or the parts that contribute to the existing technology, or a part of the technical solutions, may be implemented in the form of software products. The computer software products include several instructions stored in the storage medium for instructing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods of the embodiments of the present application. The aforementioned storage medium includes any medium capable of storing program codes, such as a USB flash drive, a removable hard disk drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0467] The foregoing description is merely a specific implementation form of the present application and is not intended to limit the protection scope of the present application. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present application shall fall within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Description of the Reference Numerals

[0468] 300 Communication method 400 Communication method 500 Communication method 800 Communication device 810 Transceiver unit 820 Processing unit 900 Communication device 910 Processor 920 Memory

Claims

1. A communication method, wherein the communication method comprises: Receiving, by a source terminal device, a first request message, wherein the first request message is used to request discovery of a target terminal device, and the first request message includes an identifier of the source terminal device and an identifier of the target terminal device; When the transmission quality of a first relay device meets a first condition and / or the capability of the first relay device meets a second condition, transmitting, by the first relay device, a second request message to the target terminal device based on the first request message; Comprising: The transmission quality of the first relay device is determined based on the first request message; The second condition includes a condition related to quality of service (QoS); The second request message is used to request discovery of the target terminal device, and the second request message includes the identifier of the source terminal device, the identifier of the target terminal device, and an identifier of the first relay device; A communication method.

2. The fact that the transmission quality of the first relay device meets the first condition is That the transmission quality of the first relay device is equal to or greater than a first threshold, or That the transmission quality of the first relay device is equal to or greater than a first threshold and the transmission quality of the first relay device is equal to or less than a second threshold, where the second threshold is greater than the first threshold; The communication method according to Claim 1.

3. The communication method according to Claim 1 or 2, wherein the first request message includes a first quality of service (QoS) requirement of the source terminal device with respect to the source terminal device and the target terminal device.

4. The fact that the capability of the first relay device meets the second condition is That the capability of the first relay device meets the first QoS requirement; The communication method according to Claim 3.

5. The communication method further comprises: Receiving, by the source terminal device, a first response message to the second request message from the target terminal device; Sending a second response message to the source terminal device for the first request message, wherein the second response message includes the identifier of the first relay device and / or the identifier of the target terminal device The communication method according to any one of claims 1 to 4, further comprising

6. The step of sending a second response message to the source terminal device for the first request message is Determining whether to send the second response message to the source terminal device based on first reference information and / or second reference information Including The first reference information includes the transmission quality of the first response message The second reference information includes whether a unicast connection is established between the first relay device and the source terminal device The communication method according to claim 5

7. The step of determining whether to send the second response message to the source terminal device based on first reference information is Determining to send the second response message to the source terminal device when the transmission quality of the first response message is greater than or equal to a third threshold, or Determining to send the second response message to the source terminal device when the transmission quality of the first response message is greater than or equal to a third threshold and the transmission quality of the first response message is less than or equal to a fourth threshold, wherein the fourth threshold is greater than the third threshold The communication method according to claim 6, including

8. The step of determining whether to send the second response message to the source terminal device based on second reference information is Determining to send the second response message to the source terminal device when the unicast connection is established between the first relay device and the source terminal device The communication method according to claim 6 or 7, including

9. After the step of sending a second response message to the source terminal device, the communication method is Receiving a third request message from the source terminal device, where the third request message is used to request establishing a first unicast connection, the third request message includes second QoS requirements of the source terminal device regarding the first relay device and the target terminal device, and the first unicast connection is a connection between the source terminal device and the first relay device; When the capabilities of the first relay device meet the second QoS requirements, establishing the first unicast connection to the source terminal device, or When the capabilities of the first relay device do not meet the second QoS requirements, skipping the step of establishing the first unicast connection to the source terminal device; The communication method according to any one of claims 5 to 8, further comprising.

10. After the step of establishing the first unicast connection to the source terminal device, the communication method includes: Sending a fourth request message to the target terminal device, where the fourth request message is used to request establishing a second unicast connection, and the second unicast connection is a connection between the target terminal device and the first relay device; Receiving a third response message from the target terminal device, where the third response message includes third QoS requirements of the target terminal device regarding the first relay device and the source terminal device; When the capabilities of the first relay device meet the third QoS requirements, establishing the second unicast connection to the target terminal device, or When the capabilities of the first relay device do not meet the third QoS requirements, skipping the step of establishing the second unicast connection to the target terminal device; The communication method according to claim 9, further comprising.

11. A first link is established between the source terminal device and the target terminal device. When the transmission quality of the second link and / or the third link does not meet the quality transmission conditions, or when the second link and / or the third link is interrupted, the first request message is used to request discovering the target terminal device, including that the first request message is used to request rediscovering the target terminal device. The second link is a link between a second relay device and the target terminal device, and the third link is a link between the second relay device and the source terminal device. The communication method according to any one of claims 1 to 10.

12. A communication method, wherein the communication method includes: Receiving a first message from each of a plurality of first terminal devices, the first message being used to request discovering a target terminal device, the first message including an identifier of the first terminal device and an identifier of the target terminal device; Determining at least one second terminal device among the plurality of first terminal devices based on first information, second information, and / or third information; Sending a second message to the at least one second terminal device, the second message indicating that the target terminal device has been discovered, the second message including the identifier of the target terminal device; and including The first information indicates a direct path or an indirect path between the first terminal device and the target terminal device, and a transmission quality between the first terminal device and the target terminal device, and the transmission quality between the first terminal device and the target terminal device is determined based on the first message; The second information indicates whether a unicast connection is established between the first terminal device and the target terminal device; The third information indicates a first quality of service (QoS) requirement of the source terminal device regarding the source terminal device and the target terminal device. Communication method.

13. The step of determining a plurality of second terminal devices among the plurality of first terminal devices based on the first information and the second information includes: determining whether there is a first terminal device that satisfies a third condition among the plurality of first terminal devices based on the first information; when there is a first terminal device that satisfies the third condition among the plurality of first terminal devices, determining the first terminal device that satisfies the third condition as the second terminal device, or when there is no first terminal device that satisfies the third condition among the plurality of first terminal devices, determining whether there is a first terminal device that satisfies a fourth condition among the plurality of first terminal devices based on the second information; including the third condition includes that there is the direct path between the first terminal device and the target terminal device, and the transmission quality between the first terminal device and the target terminal device is equal to or higher than a fifth threshold; the fourth condition includes that the unicast connection is established between the first terminal device and the target terminal device; The communication method according to claim 12.

14. The step of determining whether there is a first terminal device that satisfies a fourth condition among the plurality of first terminal devices based on the second information includes: when there is a first terminal device that satisfies the fourth condition among the plurality of first terminal devices, determining the first terminal device that satisfies the fourth condition as the second terminal device, or when there is no first terminal device that satisfies the fourth condition among the plurality of first terminal devices, determining the second terminal device from among the plurality of first terminal devices based on fourth information; including the fourth information includes the transmission quality between the first terminal device and the target terminal device; The communication method according to claim 13.

15. The step of determining the second terminal device from among the plurality of first terminal devices based on fourth information includes: determining whether there is a first terminal device that satisfies a fifth condition among the plurality of first terminal devices based on the fourth information; When there is a first terminal device that satisfies the fifth condition among the plurality of first terminal devices, determining the first terminal device that satisfies the fifth condition as the second terminal device, or When there is no first terminal device that satisfies the fifth condition among the plurality of first terminal devices, determining a first terminal device having the direct path to the target terminal device among the plurality of first terminal devices as the second terminal device, and including the fifth condition includes that there is the indirect path between the first terminal device and the target terminal device, and the transmission quality between the first terminal device and the target terminal device is greater than a sixth threshold, or the fifth condition includes that there is the indirect path between the first terminal device and the target terminal device, and both the transmission quality between the first terminal device and the target terminal device and the transmission quality between the first terminal device and the source terminal device are greater than a seventh threshold, The communication method according to claim 14.

16. The communication method according to claim 15, wherein the first message includes the transmission quality between the first terminal device and the source terminal device.

17. When a plurality of second terminal devices are determined, the communication method is determining a third terminal device among the plurality of second terminal devices and using the third terminal device as the final second terminal device further including the third terminal device is the terminal device having the highest transmission quality with the target terminal device among the plurality of second terminal devices, or the third terminal device is the terminal device having the highest transmission quality with both the target terminal device and the source terminal device among the plurality of second terminal devices, The communication method according to claim 15 or 16.

18. The step of determining a plurality of second terminal devices among the plurality of first terminal devices based on the second information is determining, as the second terminal device, a first terminal device that has established a unicast connection with the target terminal device among the plurality of first terminal devices including the communication method according to claim 12.

19. The step of determining the first terminal device that has established a unicast connection with the target terminal device among the plurality of first terminal devices as the second terminal device is the step of determining, as the second terminal device, a first terminal device that has established a unicast connection with the target terminal device and whose transmission quality with the target terminal device is equal to or higher than an eighth threshold value among the plurality of first terminal devices The communication method according to claim 18, comprising this.

20. The step of determining a plurality of second terminal devices among the plurality of first terminal devices based on third information is the step of determining, as the second terminal device, a first terminal device that satisfies the first QoS requirement among the plurality of first terminal devices The communication method according to claim 12, comprising this.

21. The communication method according to claim 12 or 20, wherein the first message includes the first QoS requirement.

22. A communication method, the communication method comprising: transmitting a first request message, the first request message being used to request discovery of a target terminal device, the first request message including an identifier of a source terminal device and an identifier of the target terminal device; receiving a third message from each of a plurality of second terminal devices, the third message indicating that the target terminal device has been discovered, the third message including an identifier of the second terminal device or the third message including the identifier of the second terminal device and the identifier of the target terminal device; determining a fourth terminal device among the plurality of second terminal devices based on sixth information and / or seventh information; and establishing a unicast connection with the target terminal device via the fourth terminal device including the sixth information indicates a direct path or an indirect path between the second terminal device and the source terminal device and a transmission quality between the second terminal device and the source terminal device, and the transmission quality between the second terminal device and the source terminal device is determined based on the third message. The seventh information indicates whether a unicast connection is established between the second terminal device and the source terminal device. Communication method. **Claim 23** The step of determining a fourth terminal device among the plurality of second terminal devices based on the sixth information and the seventh information includes: Determining, based on the sixth information, whether there is a fourth terminal device that satisfies a sixth condition among the plurality of second terminal devices; When there is a second terminal device that satisfies the sixth condition among the plurality of second terminal devices, determining the second terminal device that satisfies the sixth condition as the fourth terminal device, or When there is no second terminal device that satisfies the sixth condition among the plurality of second terminal devices, determining, based on the seventh information, whether there is a second terminal device that satisfies a seventh condition among the plurality of second terminal devices. The sixth condition includes that there is the direct path between the second terminal device and the source terminal device, and the transmission quality between the second terminal device and the source terminal device is equal to or higher than a ninth threshold. The seventh condition includes that the unicast connection is established between the second terminal device and the source terminal device. The communication method according to claim 22. **Claim 24** The step of determining, based on the seventh information, whether there is a second terminal device that satisfies a seventh condition among the plurality of second terminal devices includes: When there is a second terminal device that satisfies the seventh condition among the plurality of second terminal devices, determining the second terminal device that satisfies the seventh condition as the fourth terminal device, or When there is no second terminal device that satisfies the seventh condition among the plurality of second terminal devices, determining the fourth terminal device from among the plurality of second terminal devices based on eighth information. The eighth information includes the transmission quality between the second terminal device and the source terminal device, or The eighth information includes the transmission quality between the second terminal device and the target terminal device and the transmission quality between the second terminal device and the source terminal device. The communication method according to claim 23. **Claim 25** ​ ​ The step of determining the fourth terminal device among the plurality of second terminal devices based on the eighth information includes: determining whether there is a second terminal device that satisfies an eighth condition among the plurality of first terminal devices based on the eighth information; when there is a second terminal device that satisfies the eighth condition among the plurality of second terminal devices, determining the second terminal device that satisfies the eighth condition as the fourth terminal device, or when there is no second terminal device that satisfies the eighth condition among the plurality of second terminal devices, determining, as the fourth terminal device, a second terminal device that has the direct path to the source terminal device among the plurality of second terminal devices; including the eighth condition includes that there is the indirect path between the second terminal device and the source terminal device, and the transmission quality between the second terminal device and the source terminal device is greater than a tenth threshold, or the eighth condition includes that there is the indirect path between the second terminal device and the source terminal device, and both the transmission quality between the second terminal device and the target terminal device and the transmission quality between the second terminal device and the source terminal device are greater than an eleventh threshold; The communication method according to claim 24.

26. The communication method according to claim 25, wherein the third message includes the transmission quality between the second terminal device and the target terminal device.

27. When a plurality of fourth terminal devices are determined, the communication method further includes determining a fifth terminal device among the plurality of fourth terminal devices and using the fifth terminal device as the final fourth terminal device, wherein the fifth terminal device is a terminal device having the highest transmission quality with the target terminal device among the plurality of fourth terminal devices, or the fifth terminal device is a terminal device having the highest transmission quality with both the target terminal device and the source terminal device among the plurality of fourth terminal devices. The communication method according to claim 25 or 26.

28. The step of determining a fourth terminal device among the plurality of second terminal devices based on the seventh information includes: Determining, as the fourth terminal device, a second terminal device that has established a unicast connection with the source terminal device among the plurality of second terminal devices The communication method according to claim 22, comprising: **Claim 29** The step of determining a first terminal device that has established a unicast connection with the target terminal device among the plurality of first terminal devices as the second terminal device includes: Determining, as the fourth terminal device, a first terminal device that has established a unicast connection with the target terminal device among the plurality of first terminal devices and whose transmission quality with the target terminal device is equal to or higher than a twelfth threshold The communication method according to claim 28, comprising: **Claim 30** When a first link is established between the source terminal device and the target terminal device, and the transmission quality of the second link and / or the third link does not meet the quality transmission condition, or the second link and / or the third link is interrupted, the first request message is used to request discovering the target terminal device, including that the first request message is used to request rediscovering the target terminal device. The second link is a link between the second relay device and the target terminal device, and the third link is a link between the second relay device and the source terminal device. The communication method according to any one of claims 22 to 29 **Claim 31** When the second link and / or the third link is interrupted, before the source terminal device transmits the first request message, the communication method includes: Receiving a link interruption message transmitted by the second relay device, where the link interruption message indicates that the link between the second relay device and the target terminal device is interrupted Releasing the end-to-end unicast connection established between the source terminal device and the target terminal device and the context information of the unicast connection associated with the second link and the third link The communication method according to claim 30, comprising

32. A communication system, comprising a first relay device, a target terminal device, and / or a source terminal device, wherein the first relay device is configured to execute the communication method according to any one of claims 1 to 11, and / or the target terminal device is configured to execute the communication method according to any one of claims 12 to 21, and / or the source terminal device is configured to execute the communication method according to any one of claims 22 to 31.

33. A communication device comprising a module or unit configured to execute the communication method according to any one of claims 1 to 31.

34. A communication device, comprising one or more processors, one or more memories, one or more computer programs stored in the one or more memories, the one or more computer programs including instructions which, when executed by the one or more processors, enable the communication device to execute the communication method according to any one of claims 1 to 31 and a communication device comprising the same.

35. A computer-readable storage medium containing computer instructions which, when run on a communication device, enable the communication device to execute the communication method according to any one of claims 1 to 31.

36. A chip comprising at least one processor and an interface circuit, the interface circuit being configured to provide program instructions or data to the at least one processor, the at least one processor being configured to execute the program instructions to implement the communication method according to any one of claims 1 to 31.

37. A computer program product containing computer instructions which, when part or all of the computer instructions are run on a computer, cause the communication method according to any one of claims 1 to 31 to be executed.

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