Sidelink quality measurement method and communications apparatus

1. A method, comprising:

sending, by a first terminal device, a reference signal to a second terminal device;

receiving, by the first terminal device from the second terminal device, channel state information of a first sidelink and channel state information of a second sidelink, wherein the second sidelink is a direct link from the second terminal device to a third terminal device, the reference signal is used to determine the channel state information of the first sidelink, and the first sidelink is a direct link from the first terminal device to the second terminal device;

obtaining, by the first terminal device, channel state information of a third sidelink, wherein the third sidelink is a direct link from the first terminal device to the third terminal device; and

determining, by the first terminal device, based on the channel state information of the third sidelink, the channel state information of the second sidelink, and the channel state information of the first sidelink, a link to use to send data or control information to the third terminal device.

2. The method according to claim 1 , wherein obtaining, by the first terminal device, the channel state information of the third sidelink comprises:

receiving, by the first terminal device, the channel state information of the third sidelink from the third terminal device; or

receiving, by the first terminal device, the channel state information of the third sidelink from a network device.

3. The method according to claim 1 , further comprising:

determining, by the first terminal device based on the channel state information of the first sidelink and first data, a transmission parameter of the first data and a time-frequency resource that is to be used to send the first data; and

sending, by the first terminal device, the first data to the second terminal device on the time-frequency resource based on the transmission parameter.

4. The method according to claim 3 , further comprising:

sending, by the first terminal device, first indication information to a network device, wherein the first indication information indicates a start position and a size of the time-frequency resource to be used to send the first data; and

receiving, by the first terminal device, downlink control information from the network device, wherein the downlink control information comprises grant information of the time-frequency resource, and the grant information indicates to the first terminal device to send the first data on the time-frequency resource.

5. The method according to claim 1 , wherein the channel state information of the second sidelink comprises an identifier of the second terminal device and an identifier of the third terminal device, wherein a time domain position of a field that carries the identifier of the second terminal device is before a time domain position of a field that carries the identifier of the third terminal device, and the identifier of the second terminal device and the identifier of the third terminal device indicate the second sidelink.

6. A method, comprising:

receiving, by a second terminal device, a reference signal from a first terminal device;

determining, by the second terminal device, channel state information of a first sidelink based on the reference signal, wherein the first sidelink is a direct link from the first terminal device to the second terminal device;

obtaining, by a second terminal device, channel state information of a second sidelink, wherein the second sidelink is a direct link from the second terminal device to a third terminal device; and

sending, by the second terminal device to the first terminal device or a network device, the channel state information of the first sidelink and the channel state information of the second sidelink.

7. The method according to claim 6 , wherein obtaining, by the second terminal device, the channel state information of the second sidelink comprises:

receiving, by the second terminal device, the channel state information of the second sidelink from the third terminal device; or

receiving, by the second terminal device, the channel state information of the second sidelink from a network device.

8. The method according to claim 6 , wherein the channel state information of the second sidelink comprises an identifier of the second terminal device and an identifier of the third terminal device, a time domain position of a field that carries the identifier of the second terminal device is before a time domain position of a field that carries the identifier of the third terminal device, and the identifier of the second terminal device and the identifier of the third terminal device indicate the second sidelink.

9. A method, comprising:

receiving, by a network device from a first terminal device or a second terminal device, channel state information of a first sidelink, wherein the first sidelink is a direct link from the first terminal device to the second terminal device;

receiving, by the network device from a third terminal device, channel state information of a second sidelink and channel state information of a third sidelink, wherein the second sidelink is a direct link from the second terminal device to the third terminal device, and the third sidelink is a direct link from the first terminal device to the third terminal device;

determining, by the network device based on the channel state information of the third sidelink, the channel state information of the second sidelink, and the channel state information of the first sidelink, a first link for sending data or control information by the first terminal device to the third terminal device; and

sending, by the network device, information about the first link to the first terminal device.

10. The method according to claim 9 , further comprising:

determining, by the network device based on the channel state information of the first sidelink and first data, a transmission parameter of the first data and a time-frequency resource that is to be used by the first terminal device to send the first data, wherein the first data is data to be sent by the first terminal device on the first sidelink; and

sending, by the network device, downlink control information to the first terminal device, wherein the downlink control information comprises the transmission parameter of the first data and the time-frequency resource that is to be used to send the first data.

11. A communications apparatus, comprising:

a memory storage comprising instructions; and

one or more processors in communication with the memory storage, wherein the execution of the instructions by the one or more processors causes the apparatus to:

send a reference signal to a second terminal device;

receive, from the second terminal device, channel state information of a first sidelink and channel state information of a second sidelink, wherein the second sidelink is a direct link from the second terminal device to a third terminal device, the reference signal is used to determine the channel state information of a first sidelink, and the first sidelink is a direct link from a first terminal device to the second terminal device;

obtain channel state information of a third sidelink, wherein the third sidelink is a direct link from the first terminal device to the third terminal device; and

determine, based on the channel state information of the third sidelink, the channel state information of the second sidelink, and the channel state information of the first sidelink, a link to use to send data or control information to the third terminal device.

12. The communications apparatus according to claim 11 , wherein the execution of the instructions by the one or more processors causes the apparatus to:

receive the channel state information of the third sidelink from the third terminal device; or

receive the channel state information of the third sidelink from a network device.

13. The communications apparatus according to claim 11 , wherein the execution of the instructions by the one or more processors further causes the apparatus to:

obtain a transmission parameter of first data and a time-frequency resource to be used to send the first data, wherein the time-frequency resource to be used to send the first data and the transmission parameter of the first data are determined based on the channel state information of the first sidelink and the first data; and

send the first data to the second terminal device on the time-frequency resource based on the transmission parameter.

14. The communications apparatus according to claim 13 , wherein the execution of the instructions by the one or more processors further causes the apparatus to:

send first indication information to a network device, wherein the first indication information indicates a start position and a size of the time-frequency resource to be used to send the first data; and

receive downlink control information from the network device, wherein the downlink control information comprises grant information of the time-frequency resource, and the grant information indicates to the first terminal device to send the first data on the time-frequency resource.

15. The communications apparatus according to claim 11 , wherein the channel state information of the second sidelink comprises an identifier of the second terminal device and an identifier of the third terminal device, a time domain position of a field that carries the identifier of the second terminal device is before a time domain position of a field that carries the identifier of the third terminal device, and the identifier of the second terminal device and the identifier of the third terminal device are used to indicate the second sidelink.

16. A communications apparatus, comprising:

a memory storage comprising instructions; and

one or more processors in communication with the memory storage, wherein the execution of the instructions by the one or more processors causes the apparatus to:

receive a reference signal from a first terminal device;

determine channel state information of a first sidelink based on the reference signal, wherein the first sidelink is a direct link from the first terminal device to a second terminal device;

obtain channel state information of a second sidelink, wherein the second sidelink is a direct link from the second terminal device to a third terminal device; and

send, to the first terminal device or a network device, the channel state information of the first sidelink and the channel state information of the second sidelink.

17. The communications apparatus according to claim 16 , wherein the execution of the instructions by the one or more processors causes the apparatus to:

receive the channel state information of the second sidelink from the third terminal device; or

receive the channel state information of the second sidelink from a network device.

18. The communications apparatus according to claim 16 , wherein the channel state information of the second sidelink comprises an identifier of the second terminal device and an identifier of the third terminal device, a time domain position of a field that carries the identifier of the second terminal device is before a time domain position of a field that carries the identifier of the third terminal device, and the identifier of the second terminal device and the identifier of the third terminal device indicate the second sidelink.

19. A communications apparatus, comprising:

a memory storage comprising instructions; and

one or more processors in communication with the memory storage, wherein the execution of the instructions by the one or more processors causes the apparatus to:

receive, from a first terminal device or a second terminal device, channel state information of a first sidelink, wherein the first sidelink is a direct link from the first terminal device to the second terminal device;

receive channel state information of a second sidelink and channel state information of a third sidelink from a third terminal device, wherein the second sidelink is a direct link from the second terminal device to the third terminal device, and the third sidelink is a direct link from the first terminal device to the third terminal device;

determine, based on the channel state information of the third sidelink, the channel state information of the second sidelink, and the channel state information of the first sidelink, a link for sending data or control information by the first terminal device to the third terminal device; and

send information about the link to the first terminal device.

20. The communications apparatus according to claim 19 , wherein the execution of the instructions by the one or more processors further causes the apparatus to:

determine, based on the channel state information of the first sidelink and first data, a transmission parameter of the first data and a time-frequency resource that is to be used by the first terminal device to send the first data, wherein the first data is to be sent by the first terminal device on the first sidelink; and

send downlink control information to the first terminal device, wherein the downlink control information comprises the transmission parameter of the first data and the time-frequency resource that is to be used to send the first data.