System acquisition in a shared radio frequency spectrum band
Methods, systems, and devices for wireless communications are described. In some wireless systems utilizing shared radio frequency spectrum bands, base stations may operate in different listen before talk (LBT) modes. For example, a base station may operate in an LBT enabled mode or a non-LBT enabled mode. A UE may perform system acquisition with the base station based on receiving acquisition signals (e.g., synchronization signals and physical broadcast channel (PBCH) signals) from the base station. These acquisition signals may depend on the LBT mode of the base station. For example, the frame timing and number of subframes for the acquisition signals may be based on the LBT mode of the base station. In some cases, a base station may adaptively switch LBT modes, and the UE may re-synchronize with the base station based on an LBT configuration period or a paging message from the base station.
1. A method for wireless communications, comprising:
receiving, over a shared radio frequency spectrum band, a transmission from a base station comprising an indication of a listen before talk (LBT) mode of the base station, wherein the indication of the LBT mode indicates whether the base station is in an LBT enabled mode or a non-LBT enabled mode;
determining, based at least in part on the LBT mode of the base station indicated by the indication, a physical broadcast channel (PBCH) configuration of the base station, wherein the PBCH configuration is associated with one of an LBT enabled transmission schedule or a non-LBT enabled transmission schedule; and
receiving a PBCH transmission according to the determined PBCH configuration.
2. The method of claim 1 , wherein determining the PBCH configuration of the base station comprises determining a periodicity of a synchronization signal block based at least in part on the LBT mode of the base station.
3. The method of claim 1 , wherein determining the PBCH configuration of the base station comprises determining a periodicity of transmissions from the base station on an anchor frequency based at least in part on the LBT mode of the base station.
4. The method of claim 1 , wherein determining the PBCH configuration of the base station comprises determining, based at least in part on the LBT mode of the base station, a number of subframes that follow a synchronization signal transmission.
5. The method of claim 4 , wherein receiving the PBCH transmission comprises receiving, based at least in part on the determined number of subframes, the PBCH transmission over one or more subframes following the synchronization signal transmission, and the method further comprising:
decoding a master information block (MIB) based at least in part on the PBCH transmission.
6. The method of claim 1 , further comprising:
receiving a second PBCH transmission according to the determined PBCH configuration; and
decoding a MIB based at least in part on the PBCH transmission and the second PBCH transmission.
7. The method of claim 1 , further comprising:
receiving a paging message from the base station, the paging message indicating a change in the LBT mode of the base station.
8. The method of claim 7 , further comprising:
performing a re-synchronization process with the base station based at least in part on receiving the paging message.
9. The method of claim 1 , further comprising:
identifying an LBT mode configuration period of the base station, wherein determining the PBCH configuration of the base station is based at least in part on the identified LBT mode configuration period of the base station.
10. The method of claim 1 , wherein the PBCH transmission comprises subframe timing information, frame timing information, a frequency hopping bandwidth, a number of hopping frequencies, a location of system information, a frame structure for a data channel, or any combination thereof.
11. The method of claim 1 , wherein the transmission from the base station comprises a synchronization signal.
12. The method of claim 11 , wherein the synchronization signal comprises a cell identifier, the cell identifier comprising the indication of the LBT mode of the base station.
13. A method for wireless communications, comprising:
identifying, at a base station, a listen before talk (LBT) mode of the base station;
transmitting, over a shared radio frequency spectrum band, a transmission comprising an indication of the LBT mode of the base station, wherein the indication of the LBT mode indicates whether the base station is in an LBT enabled mode or a non-LBT enabled mode; and
transmitting a physical broadcast channel (PBCH) transmission according to a PBCH configuration, the PBCH configuration based at least in part on the LBT mode of the base station and associated with one of an LBT enabled transmission schedule or a non-LBT enabled transmission schedule.
14. The method of claim 13 , further comprising:
transmitting a synchronization signal block according to a synchronization signal block periodicity, the synchronization signal block periodicity based at least in part on the LBT mode of the base station.
15. The method of claim 13 , further comprising:
transmitting, on an anchor frequency, one or more transmissions according to a transmission periodicity, the transmission periodicity based at least in part on the LBT mode of the base station.
16. The method of claim 13 , further comprising:
performing an LBT mode switch comprising changing from the LBT mode of the base station to a second LBT mode of the base station, wherein the LBT mode switch is between the LBT enabled mode and the non-LBT enabled mode.
17. The method of claim 16 , wherein performing the LBT mode switch comprises transmitting a paging message to a user equipment (UE), the paging message indicating the LBT mode switch.
18. The method of claim 16 , wherein performing the LBT mode switch is based at least in part on an LBT mode configuration period.
19. The method of claim 18 , further comprising:
transmitting a message indicating the LBT mode configuration period.
20. The method of claim 16 , wherein performing the LBT mode switch is based at least in part on a channel congestion threshold associated with the shared radio frequency spectrum band.
21. The method of claim 13 , wherein the PBCH transmission comprises subframe timing information, frame timing information, a frequency hopping bandwidth, a number of hopping frequencies, a location of system information, a frame structure for a data channel, or any combination thereof.
22. The method of claim 13 , wherein the transmission further comprises a synchronization signal.
23. The method of claim 22 , wherein the PBCH transmission is transmitted in a number of subframes following the synchronization signal, wherein the number of subframes is based at least in part on the LBT mode of the base station.
24. The method of claim 22 , wherein the synchronization signal comprises a cell identifier, the cell identifier comprising the indication of the LBT mode of the base station.
25. An apparatus for wireless communications, comprising:
a processor;
memory in electronic communication with the processor; and
instructions stored in the memory, wherein the instructions are executable by the processor to:
receive, over a shared radio frequency spectrum band, a transmission from a base station comprising an indication of a listen before talk (LBT) mode of the base station, wherein the indication of the LBT mode indicates whether the base station is in an LBT enabled mode or a non-LBT enabled mode;
determine, based at least in part on the LBT mode of the base station indicated by the indication, a physical broadcast channel (PBCH) configuration of the base station, wherein the PBCH configuration is associated with one of an LBT enabled transmission schedule or a non-LBT enabled transmission schedule; and
receive a PBCH transmission according to the determined PBCH configuration.
26. The apparatus of claim 25 , wherein determining the PBCH configuration of the base station comprises determining a periodicity of a synchronization signal block based at least in part on the LBT mode of the base station.
27. The apparatus of claim 25 , wherein determining the PBCH configuration of the base station comprises determining a periodicity of transmissions from the base station on an anchor frequency based at least in part on the LBT mode of the base station.
28. The apparatus of claim 25 , wherein determining the PBCH configuration of the base station comprises determining, based at least in part on the LBT mode of the base station, a number of subframes that follow a synchronization signal transmission.
29. The apparatus of claim 25 , wherein the instructions are further executable by the processor to:
receive a second PBCH transmission according to the determined PBCH configuration; and
decode a MIB based at least in part on the PBCH transmission and the second PBCH transmission.
30. An apparatus for wireless communications, comprising:
a processor;
memory in electronic communication with the processor; and
instructions stored in the memory, wherein the instructions are executable by the processor to:
identify, at a base station, a listen before talk (LBT) mode of the base station;
transmit, over a shared radio frequency spectrum band, a transmission comprising an indication of the LBT mode of the base station, wherein the indication of the LBT mode indicates whether the base station is in an LBT enabled mode or a non-LBT enabled mode; and
transmit a physical broadcast channel (PBCH) transmission according to a PBCH configuration, the PBCH configuration based at least in part on the LBT mode of the base station and associated with one of an LBT enabled transmission schedule or a non-LBT enabled transmission schedule.