Method and devices for transmitting system information from terminal device

1. A method, wherein the method comprises:

receiving, by a first terminal device from a second terminal device, first indication information, wherein the first indication information comprises information indicating one or more capabilities supported by the second terminal device, the one or more capabilities including an extended access barring (EAB) capability, a commercial mobile alert service (CMAS) capability, a service specific access control (SSAC) capability, or an application specific congestion control for data communication (ACDC) capability supported by the second terminal device;

determining, by the first terminal device, all of system information (SI) required by the second terminal device based on the first indication information including the one or more capabilities supported by the second terminal device, wherein the second terminal device communicates with a base station via the first terminal device; and

sending, by the first terminal device, a message comprising target SI to the second terminal device, wherein the target SI is some or all of the SI required by the second terminal device.

2. The method according to claim 1 , wherein the first indication information comprises information indicating a type of the SI required by the second terminal device.

3. The method according to claim 1 , wherein the method further comprises:

sending, by the first terminal device, a first broadcast message to the second terminal device, wherein the first broadcast message comprises public SI and the target SI does not comprise the public SI.

4. The method according to claim 1 , wherein the sending the message comprising the target SI comprises:

sending, by the first terminal device, a second broadcast message, wherein the second broadcast message is a discovery message that carries the target SI or a master information block-SL message that carries the target SI.

5. The method according to claim 1 , wherein the sending the message comprising the target SI comprises:

receiving, by the first terminal device, system information broadcast by the base station;

extracting, by the first terminal device, the target SI from the system information broadcast by the base station;

generating, by the first terminal device, a Radio Resource Control (RRC) message, wherein the RRC message comprises the target SI; and

sending, by the first terminal device, the RRC message to the second terminal device.

6. A method, wherein the method comprises:

generating, by a second terminal device, first indication information that indicates system information (SI) required by the second terminal device, wherein the first indication information comprises information indicating one or more capabilities supported by the second terminal device, the one or more capabilities including an extended access barring (EAB) capability, a commercial mobile alert service (CMAS) capability, a service specific access control (SSAC) capability, or an application specific congestion control for data communication (ACDC) capability supported by the second terminal device;

sending, by the second terminal device, the first indication information to a first terminal device for the first terminal device to determine all of the SI required by the second terminal device, wherein the second terminal device communicates with a base station via the first terminal device; and

receiving, by the second terminal device from the first terminal device, a message that comprises target SI, wherein the target SI is some or all of the SI required by the second terminal device.

7. The method according to claim 6 , wherein the first indication information comprises information indicating a type of the SI required by the second terminal device.

8. The method according to claim 6 , wherein the method further comprises:

receiving, by the second terminal device, a first broadcast message sent by the first terminal device, wherein the first broadcast message comprises public SI and the target SI does not comprise the public SI.

9. The method according to claim 6 , wherein the receiving the message that comprises the target SI comprises:

receiving, by the second terminal device, a second broadcast message sent by the first terminal device, wherein the second broadcast message is a discovery message that carries the target SI or a master information block-SL message that carries the target SI.

10. The method according to claim 6 , wherein the receiving the message that comprises the target SI comprises:

receiving, by the second terminal device, a Radio Resource Control (RRC) message generated by the first terminal device, wherein the RRC message comprises the target SI.

11. A terminal device comprising:

a transceiver;

a non-transitory memory storage comprising instructions; and

a processor in communication with the non-transitory memory storage, wherein the processor is configured to execute the instructions to:

receive first indication information from a second terminal device, wherein the first indication information comprises information indicating one or more capabilities supported by the second terminal device, one or more capabilities including an extended access barring (EAB) capability, a commercial mobile alert service (CMAS) capability, a service specific access control (SSAC) capability, or an application specific congestion control for data communication (ACDC) capability supported by the second terminal device;

determine all of system information (SI) required by second terminal device based on the first indication information including the one or more capabilities supported by the second terminal device, wherein the second terminal device communicates with a base station via the terminal device; and

send a message comprising target SI to the second terminal device, wherein the target SI is at least some or all of the SI required by the second terminal device.

12. The terminal device according to claim 11 , wherein the first indication information comprises information indicating a type of the SI required by the second terminal device.

13. The terminal device according to claim 11 , wherein the processor is further configured to execute the instructions to:

send a first broadcast message that comprises public SI and wherein the target SI does not comprise the public SI.

14. The terminal device according to claim 11 , wherein the processor is further configured to execute the instructions to:

send a second broadcast message to the second terminal device, wherein the second broadcast message is a discovery message that carries the target SI or a master information block-SL message that carries the target SI.

15. The terminal device according to claim 11 , wherein the processor is further configured to execute the instructions to:

receive system information broadcast by the base station;

extract the target SI from the system information broadcast by the base station;

generate a Radio Resource Control (RRC) message that comprises the target SI; and

send the RRC message to the second terminal device.

16. A terminal device, wherein the terminal device comprises:

a transceiver;

a non-transitory memory storage comprising instructions; and

a processor in communication with the non-transitory memory storage, wherein the processor is configured to execute the instructions to:

generate first indication information that indicates system information (SI) required by the terminal device, wherein the first indication information comprises information indicating one or more capabilities supported by the terminal device, the one or more capabilities including an extended access barring (EAB) capability, a commercial mobile alert service (CMAS) capability, a service specific access control (SSAC) capability, or an application specific congestion control for data communication (ACDC) capability supported by the terminal device;

send the first indication information to a first terminal device for the first terminal device to determine all of the SI required by the terminal device, wherein the terminal device is configured to communicate with a base station via the first terminal device; and

receive a message that comprises target SI from the first terminal device, wherein the target SI is some or all of the SI required by the terminal device.

17. The terminal device according to claim 16 , wherein the first indication information comprises information indicating a type of the SI required by the terminal device.

18. The terminal device according to claim 16 , wherein the processor is further configured to execute the instructions to:

receive a first broadcast message sent by the first terminal device, wherein the first broadcast message comprises public SI and the target SI does not comprise the public SI.

19. The terminal device according to claim 16 , wherein the processor is further configured to execute the instructions to:

receive a second broadcast message sent by the first terminal device, wherein the second broadcast message is a discovery message that carries the target SI or a master information block-SL message that carries the target SI.

20. The terminal device according to claim 16 , wherein the processor is further configured to:

execute the instructions to receive a Radio Resource Control (RRC) message generated by the first terminal device, and wherein the RRC message comprises the target SI.

21. The method of claim 1 , further comprising:

adding, by the first terminal device, the second terminal device into a target device group based on the first indication information, wherein terminal devices in the target device group share at least one requirement for the SI, wherein the message is a multicast message, and wherein the sending comprises:

sending, by the first terminal device, the multicast message including the target SI to the terminal devices in the target device group.

22. The method of claim 1 , wherein the one or more capabilities include the SSAC capability or the ACDC capability, wherein the first indication information includes an updated parameter of the one or more capabilities, and wherein the SI in the message comprises an updated SI.