Sidelink synchronization signal block transmissions in a shared spectrum
Methods, systems, and devices for wireless communications are described. Generally, the described techniques provide for efficiently identifying resources for transmitting one or more sidelink synchronization signal blocks (S-SSBs) in the shared spectrum or efficiently beam sweeping multiple S-SSBs in the shared spectrum. In one aspect, a user equipment (UE) may transmit an S-SSB in a sidelink bandwidth part (BWP) in the shared spectrum such that a lower edge of the S-SSB is aligned with or offset from a lower edge of the sidelink BWP. In another aspect, a UE may beam sweep S-SSBs in one or more S-SSB bursts in a S-SSB period to improve the chances that another UE may receive the S-SSBs. In yet another aspect, resources allocated for S-SSB transmissions may facilitate flexible S-SSB transmissions while minimizing gaps to prevent other UEs from incorrectly determining that a sidelink BWP in a shared spectrum is clear for transmission.
1 . A method for wireless communication at a user equipment (UE), comprising:
identifying a discovery reference signal (DRS) window in a shared spectrum comprising a plurality of starting positions for transmitting one or more sidelink synchronization signal blocks;
performing a listen-before-talk procedure to gain access to the discovery reference signal window in the shared spectrum; and
transmitting the one or more sidelink synchronization signal blocks at a first starting position of the plurality of starting positions after gaining access to the discovery reference signal window in the shared spectrum, wherein the one or more sidelink synchronization signal blocks are transmitted in a sidelink bandwidth part, and a lower edge in a frequency domain of the one or more sidelink synchronization signal blocks is aligned with or offset from a lower edge in the frequency domain of the sidelink bandwidth part.
2 . The method of claim 1 , wherein transmitting the one or more sidelink synchronization signal blocks comprises:
transmitting a sidelink synchronization signal block of the one or more sidelink synchronization signal blocks in a physical sidelink broadcast channel with an indication of a slot that includes the synchronization signal block.
3 . The method of claim 1 , wherein transmitting the one or more sidelink synchronization signal blocks comprises:
transmitting a sidelink synchronization signal block of the one or more sidelink synchronization signal blocks in a physical sidelink broadcast channel with a demodulation reference signal scrambling sequence indicating a beam index of a beam used to transmit the synchronization signal block.
4 . The method of claim 1 , wherein the performing the listen-before-talk procedure comprises:
performing a category two listen-before-talk procedure to gain access to the discovery reference signal window in the shared spectrum.
5 . The method of claim 1 , wherein the performing the listen-before-talk procedure comprises:
performing a category four listen-before-talk procedure to gain access to the discovery reference signal window in the shared spectrum.
6 . The method of claim 1 , wherein the performing the listen-before-talk procedure comprises:
performing a category two or a category four listen-before-talk procedure with a highest available priority associated therewith to gain access to the discovery reference signal window in the shared spectrum.
7 . A user equipment (UE), comprising:
one or more memories storing processor-executable code; and one or more processors coupled with the one or more memories and individually or collectively operable to execute the code to cause the UE to:
identify a discovery reference signal (DRS) window in a shared spectrum comprising a plurality of starting positions for transmitting one or more sidelink synchronization signal blocks;
perform a listen-before-talk procedure to gain access to the discovery reference signal window in the shared spectrum; and
transmit the one or more sidelink synchronization signal blocks at a first starting position of the plurality of starting positions after gaining access to the discovery reference signal window in the shared spectrum, wherein the one or more sidelink synchronization signal blocks are transmitted in a sidelink bandwidth part, and a lower edge in a frequency domain of the one or more sidelink synchronization signal blocks is aligned with or offset from a lower edge in the frequency domain of the sidelink bandwidth part.
8 . The UE of claim 7 , wherein to transmit the one or more sidelink synchronization signal blocks, the one or more processors are individually or collectively operable to execute the code to cause the UE to:
transmit a sidelink synchronization signal block of the one or more sidelink synchronization signal blocks in a physical sidelink broadcast channel with an indication of a slot that includes the synchronization signal block.
9 . The UE of claim 7 , wherein to transmit the one or more sidelink synchronization signal blocks, the one or more processors are individually or collectively operable to execute the code to cause the UE to:
transmitting a sidelink synchronization signal block of the one or more sidelink synchronization signal blocks in a physical sidelink broadcast channel with a demodulation reference signal scrambling sequence indicating a beam index of a beam used to transmit the synchronization signal block.
10 . The UE of claim 7 , wherein to perform the listen-before-talk procedure, the one or more processors are individually or collectively operable to execute the code to cause the UE to:
perform a category two listen-before-talk procedure to gain access to the discovery reference signal window in the shared spectrum.
11 . The UE of claim 7 , wherein to perform the listen-before-talk procedure, the one or more processors are individually or collectively operable to execute the code to cause the UE to:
perform a category four listen-before-talk procedure to gain access to the discovery reference signal window in the shared spectrum.
12 . The UE of claim 7 , wherein to perform the listen-before-talk procedure, the one or more processors are individually or collectively operable to execute the code to cause the UE to:
perform a category two or a category four listen-before-talk procedure using a highest available priority associated therewith to gain access to the discovery reference signal window in the shared spectrum.
13 . A user equipment (UE) for wireless communications, comprising:
means for identifying a discovery reference signal (DRS) window in a shared spectrum comprising a plurality of starting positions for transmitting one or more sidelink synchronization signal blocks;
means for performing a listen-before-talk procedure to gain access to the discovery reference signal window in the shared spectrum; and
means for transmitting the one or more sidelink synchronization signal blocks at a first starting position of the plurality of starting positions after gaining access to the discovery reference signal window in the shared spectrum, wherein the one or more sidelink synchronization signal blocks are transmitted in a sidelink bandwidth part, and a lower edge in a frequency domain of the one or more sidelink synchronization signal blocks is aligned with or offset from a lower edge in the frequency domain of the sidelink bandwidth part.
14 . The UE of claim 13 , wherein the means for transmitting the one or more sidelink synchronization signal blocks comprise:
means for transmitting a sidelink synchronization signal block of the one or more sidelink synchronization signal blocks in a physical sidelink broadcast channel with an indication of a slot that includes the synchronization signal block.
15 . The UE of claim 13 , wherein the means for transmitting the one or more sidelink synchronization signal blocks comprise:
means for transmitting a sidelink synchronization signal block of the one or more sidelink synchronization signal blocks in a physical sidelink broadcast channel with a demodulation reference signal scrambling sequence indicating a beam index of a beam used to transmit the synchronization signal block.
16 . The UE of claim 13 , wherein the means for performing the listen-before-talk procedure comprise:
means for performing a category two listen-before-talk procedure to gain access to the discovery reference signal window in the shared spectrum.
17 . The UE of claim 13 , wherein the means for performing the listen-before-talk procedure comprise:
means for performing a category four listen-before-talk procedure to gain access to the discovery reference signal window in the shared spectrum.
18 . The UE of claim 13 , wherein the means for performing the listen-before-talk procedure comprise:
means for performing a category two or a category four listen-before-talk procedure with a highest available priority associated therewith to gain access to the discovery reference signal window in the shared spectrum.
19 . A non-transitory computer-readable medium storing code for wireless communications, the code comprising instructions executable by one or more processors to:
identify a discovery reference signal (DRS) window in a shared spectrum comprising a plurality of starting positions for transmitting one or more sidelink synchronization signal blocks;
perform a listen-before-talk procedure to gain access to the discovery reference signal window in the shared spectrum; and
transmit the one or more sidelink synchronization signal blocks at a first starting position of the plurality of starting positions after gaining access to the discovery reference signal window in the shared spectrum, wherein the one or more sidelink synchronization signal blocks are transmitted in a sidelink bandwidth part, and a lower edge in a frequency domain of the one or more sidelink synchronization signal blocks is aligned with or offset from a lower edge in the frequency domain of the sidelink bandwidth part.
20 . The non-transitory computer-readable medium of claim 19 , wherein the instructions to transmit the one or more sidelink synchronization signal blocks are executable by the one or more processors to:
transmit a sidelink synchronization signal block of the one or more sidelink synchronization signal blocks in a physical sidelink broadcast channel with an indication of a slot that includes the synchronization signal block.
21 . The non-transitory computer-readable medium of claim 19 , wherein the instructions to transmit the one or more sidelink synchronization signal blocks are executable by the one or more processors to:
transmit a sidelink synchronization signal block of the one or more sidelink synchronization signal blocks in a physical sidelink broadcast channel with a demodulation reference signal scrambling sequence indicating a beam index of a beam used to transmit the synchronization signal block.
22 . The non-transitory computer-readable medium of claim 19 , wherein the instructions to perform the listen-before-talk procedure are executable by the one or more processors to:
perform a category two listen-before-talk procedure to gain access to the discovery reference signal window in the shared spectrum.
23 . The non-transitory computer-readable medium of claim 19 , wherein the instructions to perform the listen-before-talk procedure are executable by the one or more processors to:
perform a category four listen-before-talk procedure to gain access to the discovery reference signal window in the shared spectrum.
24 . The non-transitory computer-readable medium of claim 19 , wherein the instructions to perform the listen-before-talk procedure are executable by the one or more processors to:
perform a category two or a category four listen-before-talk procedure with a highest available priority associated therewith to gain access to the discovery reference signal window in the shared spectrum.