Transmitting system information on sidelink

1. A method for wireless communications performed by a first user equipment (UE), comprising:

receiving first system information from a second UE;

determining, based on one or more first parameters, to receive second system information from the second UE;

receiving the second system information in a sidelink system information block (S-SIB) from the second UE, wherein the first system information comprises a first parameter of the one or more first parameters that implicitly indicates the second UE will transmit or has transmitted the S-SIB and wherein the first parameter indicates at least one of:

the second UE uses a time division duplex (TDD) communication system; or

a synchronization source for the second UE is a base station (BS); and

communicating with the second UE via sidelink resources determined based on the first system information and the second system information.

2. The method of claim 1 , wherein the first system information is conveyed via a sidelink master information block (S-MIB), the S-MIB conveyed via a physical sidelink broadcast channel (PSBCH).

3. A method for wireless communications performed by a first user equipment (UE), comprising:

receiving first system information from a second UE;

determining, based on one or more first parameters, to receive second system information from the second UE, wherein the one or more first parameters comprise an elapsed time since the first UE previously received another second system information;

receiving the second system information in a sidelink system information block (S-SIB) from the second UE; and

communicating with the second UE via sidelink resources determined based on the first system information and the second system information.

4. The method of claim 1 , further comprising determining a time resource to receive the S-SIB, wherein the first UE receives the S-SIB using the determined time resource.

5. The method of claim 4 , wherein the time resource occurs during a window, and the method further comprises determining a size of the window.

6. The method of claim 5 , wherein the first system information comprises one or more second parameters and the time is determined based on the one or more second parameters.

7. The method of claim 5 , wherein the time occurs a predetermined period after receiving the first system information.

8. The method of claim 1 , further comprising determining a frequency resource to receive the S-SIB, wherein the first system information comprises one or more second parameters and the frequency resource is determined based on the one or more second parameters.

9. The method of claim 1 , further comprising determining a frequency resource to receive the S-SIB, wherein the frequency resource is determined based on a frequency used to transmit the first system information.

10. The method of claim 1 , further comprising determining a frequency resource to receive the S-SIB, wherein determining the frequency resource comprises:

determining a plurality of frequency resources; and

performing blind decoding to receive the second system information in the plurality of frequency resources.

11. The method of claim 1 , wherein the second system information includes at least one of a time-division duplex (TDD) uplink/downlink (UL/DL) configuration for sidelink communications, a sidelink slots configuration indicating slots allocated for sidelink communications, a sidelink bandwidth part indicating a frequency band allocated for sidelink communication, and a sidelink resource pool indicating a set of time and frequency resources allocated for sidelink communication.

12. The method of claim 1 , wherein:

the first system information is transmitted by the second UE at a first periodicity; and

the second system information is transmitted by the second UE at a second periodicity.

13. A method for wireless communications performed by a first user equipment (UE), comprising:

transmitting first system information to a second UE;

determining, based on one or more first parameters, to transmit second system information to the second UE;

transmitting the second system information in a sidelink system information block (S-SIB) to the second UE, wherein the first system information comprises a first parameter of the one or more first parameters that implicitly indicates the first UE will transmit or has transmitted the S-SIB, and wherein the first parameter indicates that a synchronization source for the first UE is a base station (BS); and

communicating with the second UE via sidelink resources determined based on the first system information and the second system information.

14. The method of claim 13 , further comprising:

receiving third system information from a base station (BS) or a third UE, wherein the third system information includes at least one of:

the one or more first parameters; or

an indication of time or frequency resources to be used for transmitting the second system information.

15. The method of claim 13 , wherein the first system information is conveyed via a sidelink master information block (S-MIB), the S-MIB being conveyed via a physical sidelink broadcast channel (PSBCH).

16. The method of claim 13 , wherein the one or more first parameters comprise a frequency band used by the first UE for transmitting the first system information.

17. A method for wireless communications performed by a first user equipment (UE), comprising:

transmitting first system information to a second UE;

determining, based on one or more first parameters, to transmit second system information to the second UE, wherein the one or more first parameters comprise an elapsed time since the first UE previously transmitted another second system information;

transmitting the second system information in a sidelink system information block (S-SIB) to the second UE, and

communicating with the second UE via sidelink resources determined based on the first system information and the second system information.

18. The method of claim 13 , further comprising determining a time resource for transmitting the S-SIB, wherein the first UE transmits the S-SIB using the determined time resource, wherein the time resource occurs during a window, and the method further comprises determining a size of the window.

19. The method of claim 13 , further comprising determining a time to transmit the S-SIB, wherein the first UE transmits the S-SIB at the determined time, wherein the first system information comprises one or more second parameters and the time is determined based on the one or more second parameters.

20. The method of claim 13 , further comprising determining a time to transmit the S-SIB, wherein the first UE transmits the S-SIB at the determined time, wherein the time occurs a predetermined period after transmitting the first system information.

21. The method of claim 13 , further comprising determining a frequency resource to transmit the S-SIB, wherein the first system information comprises one or more second parameters and the frequency resource is determined based on the one or more second parameters.

22. The method of claim 13 , further comprising determining a frequency resource to transmit the S-SIB, wherein the frequency resource is determined based on a frequency used to transmit the first system information.

23. The method of claim 13 , wherein the S-SIB is conveyed in a physical sidelink shared channel (PSSCH).

24. The method of claim 13 , wherein the second system information includes at least one of a time-division duplex (TDD) uplink/downlink (UL/DL) configuration for sidelink communications, a sidelink slots configuration indicating slots allocated for sidelink communications, a sidelink bandwidth part indicating a frequency band allocated for sidelink communication, and a sidelink resource pool indicating a set of time and frequency resources allocated for sidelink communication.

25. The method of claim 13 , wherein:

the first system information is transmitted by the first UE at a first periodicity; and

the second system information is transmitted by the first UE at a second periodicity.

26. The method of claim 13 , further comprising:

determining a synchronization priority of the first UE; and

determining to transmit the second system information based on at least the synchronization priority of the first UE.

27. A first apparatus for wireless communications comprising:

a processor configured to:

receive first system information from a user equipment (UE);

determine, based on one or more first parameters, to receive second system information from the UE;

receive the second system information in a sidelink system information block (S-SIB) from the UE, wherein the first system information comprises a first parameter of the one or more first parameters that implicitly indicates the second UE will transmit or has transmitted the S-SIB and wherein the first parameter indicates at least one of:

the second UE uses a time division duplex (TDD) communication system;

or

a synchronization source for the second UE is a base station (BS); and

communicate with the UE using sidelink resources determined based on the first system information and the second system information; and

a memory coupled with the processor.

28. A first apparatus for wireless communications comprising:

a processor configured to:

transmit first system information to a user equipment (UE);

determine, based on one or more first parameters, to transmit second system information to the UE;

transmit the second system information in a sidelink system information block (S-SIB) to the UE, wherein the first system information comprises a first parameter of the one or more first parameters that implicitly indicates the first UE will transmit or has transmitted the S-SIB, and wherein the first parameter indicates that a synchronization source for the first UE is a base station (BS); and

communicate with the UE via sidelink resources determined based on the first system information and the second system information; and

a memory coupled with the processor.

29. The method of claim 3 , wherein the one or more first parameters comprise a frequency band used by the second UE for transmitting the first system information.

30. The method of claim 17 , wherein the one or more first parameters comprise a frequency band used by the first UE for transmitting the first system information.

31. A first apparatus for wireless communications comprising:

a processor configured to:

receive first system information from a second user equipment (UE);

determine, based on one or more first parameters, to receive second system information from the second UE, wherein the one or more first parameters comprise an elapsed time since the first UE previously received another second system information;

receive the second system information in a sidelink system information block (S-SIB) from the second UE; and

communicate with the second UE via sidelink resources determined based on the first system information and the second system information; and

a memory coupled with the processor.

32. A first apparatus for wireless communications comprising:

a processor configured to:

transmit first system information to a second user equipment (UE);

determine, based on one or more first parameters, to transmit second system information to the second UE, wherein the one or more first parameters comprise an elapsed time since the first UE previously transmitted another second system information;

transmit the second system information in a sidelink system information block (S-SIB) to the second UE; and

communicate with the second UE via sidelink resources determined based on the first system information and the second system information; and

a memory coupled with the processor.