Method and apparatus for transmiting and receiving synchronization signal in new radio vehicle to everything system

1. A method comprising:

determining, by a wireless user device, a global navigation satellite system (GNSS) as a synchronization reference source associated with a sidelink synchronization;

determining a slot number for sidelink communication, based on:

the GNSS being the synchronization reference source associated with a sidelink synchronization;

a subcarrier spacing index for sidelink; and

one or more time parameters associated with the GNSS,

wherein the determining the slot number is based on Floor((Tcurrent−Tref−OffsetDFN)*2 μ )mod(10*2 μ ), where Tcurrent is a current Coordinated Universal Time (UTC) time obtained from the GNSS, Tref is a reference UTC time, OffsetDFN is, if configured, a direct frame number (DFN) offset value associated with a sidelink DFN or, if not configured, zero, and, wherein μ is the subcarrier spacing index for sidelink; and transmitting, based on the slot number, a sidelink synchronization signal from the wireless user device to a second wireless user device.

2. The method of claim 1 , further comprising:

determining, based on the one or more time parameters associated with the GNSS and based on the GNSS being the synchronization reference source associated with a sidelink synchronization, a direct frame number (DFN) of a frame,

wherein the transmitting the sidelink synchronization signal is further based on the DFN.

3. The method of claim 1 , wherein:

μ=0 for 15 kHz of subcarrier spacing for sidelink;

μ=1 for 30 kHz of subcarrier spacing for sidelink;

μ=2 for 60 kHz of subcarrier spacing for sidelink;

μ=3 for 120 kHz of subcarrier spacing for sidelink; and

μ=4 for 240 kHz of subcarrier spacing for sidelink.

4. The method of claim 1 , further comprising:

determining a parameter indicating a starting point of a sidelink-synchronization signal block (SL-SSB) time window,

wherein the transmitting the sidelink synchronization signal comprises transmitting, based on the slot number and based on the parameter indicating the starting point of the SL-SSB time window, one or more SL-SSBs.

5. The method of claim 4 , further comprising:

receiving, from a base station, one or more messages comprising the parameter indicating the starting point of the SL-SSB time window.

6. The method of claim 1 , further comprising:

receiving, from a base station, configuration information for transmitting one or more sidelink synchronization signal,

wherein the transmitting the sidelink synchronization signal is further based on the configuration information.

7. The method of claim 1 , further comprising:

determining, based on not receiving from a base station configuration information for transmitting one or more sidelink synchronization signal, preconfigured configuration information for transmitting one or more sidelink synchronization signal,

wherein the transmitting the sidelink synchronization signal is further based on the preconfigured configuration information.

8. The method of claim 1 , wherein the sidelink synchronization comprises a New Radio (NR) vehicle-to-everything (V2X) sidelink synchronization,

wherein the subcarrier spacing index for sidelink comprises a subcarrier spacing index for NR V2X sidelink,

wherein the slot number for sidelink communication comprises a slot number for NR V2X sidelink communication, and

wherein the sidelink synchronization signal comprises an NR V2X sidelink synchronization signal.

9. The method of claim 1 , further comprising:

establishing a link between the wireless user device and a base station,

wherein the link between the wireless user device and the base station comprises at least one of:

a Long-Term Evolution (LTE) Uu link; or

a New Radio (NR) Uu link.

10. A method comprising:

determining, by a wireless user device, a global navigation satellite system (GNSS) as a synchronization reference source associated with a sidelink synchronization;

determining a slot number for sidelink communication, based on:

the GNSS being the synchronization reference source associated with a sidelink synchronization; and a modulo operation associated with a subcarrier spacing index for sidelink;

transmitting, based on the slot number, a sidelink synchronization signal from the wireless user device to a second wireless user device, and wherein the determining the slot number is based on Floor((Tcurrent−Tref−OffsetDFN)*2 μ )mod(10*2 μ ), where Tcurrent is a current Coordinated Universal Time (UTC) time obtained from the GNSS, Tref is a reference UTC time, OffsetDFN is, if configured, a direct frame number (DFN) offset value associated with a sidelink DFN or, if not configured, zero, and wherein u is the subcarrier spacing index for sidelink.

11. The method of claim 10 , wherein the determining the slot number for sidelink communication comprises using, for the modulo operation, a plurality of parameters each associated with the subcarrier spacing index.

12. The method of claim 10 , further comprising:

determining, based on one or more time parameters associated with the GNSS and based on the GNSS being the synchronization reference source associated with a sidelink synchronization, a direct frame number (DFN) of a frame,

wherein the transmitting the sidelink synchronization signal is further based on the DFN, and

wherein the determining the slot number is further based on the one or more time parameters associated with the GNSS.

13. The method of claim 10 , wherein: μ=0 for 15 kHz of subcarrier spacing for sidelink; μ=1 for 30 kHz of subcarrier spacing for sidelink; μ=2 for 60 kHz of subcarrier spacing for sidelink; μ=3 for 120 kHz of subcarrier spacing for sidelink; and μ=4 for 240 kHz of subcarrier spacing for sidelink.

14. The method of claim 10 , further comprising:

determining a parameter indicating a starting point of a sidelink-synchronization signal block (SL-SSB) time window,

wherein the transmitting the sidelink synchronization signal comprises transmitting, based on the slot number and based on the parameter indicating the starting point of the SL-SSB time window, one or more SL-SSBs.

15. The method of claim 14 , further comprising:

receiving, from a base station, one or more messages comprising the parameter indicating the starting point of the SL-SSB time window.

16. The method of claim 10 , further comprising:

receiving, from a base station, configuration information for transmitting one or more sidelink synchronization signal,

wherein the transmitting the sidelink synchronization signal is further based on the configuration information.

17. The method of claim 10 , further comprising:

determining, based on not receiving from a base station configuration information for transmitting one or more sidelink synchronization signal, preconfigured configuration information for transmitting one or more sidelink synchronization signal,

wherein the transmitting the sidelink synchronization signal is further based on the preconfigured configuration information.

18. The method of claim 10 , wherein the sidelink synchronization comprises a New Radio (NR) vehicle-to-everything (V2X) sidelink synchronization,

wherein the subcarrier spacing index for sidelink comprises a subcarrier spacing index for NR V2X sidelink,

wherein the slot number for sidelink communication comprises a slot number for NR V2X sidelink communication, and

wherein the sidelink synchronization signal comprises an NR V2X sidelink synchronization signal.

19. The method of claim 10 , further comprising:

establishing a link between the wireless user device and a base station,

wherein the link between the wireless user device and the base station comprises at least one of:

a Long-Term Evolution (LTE) Uu link; or

a New Radio (NR) Uu link.