Techniques for transmitting and receiving synchronization signals over an unlicensed radio frequency spectrum band
Techniques are described for wireless communication. A first method may include receiving at a user equipment (UE) over an unlicensed radio frequency spectrum band an indication of a time window associated with a transmission of a synchronization signal, and monitoring the unlicensed radio frequency spectrum band during the time window to receive a synchronization signal from a base station. A second method may include transmitting an indication of a time window associated with a transmission of a synchronization signal; performing a plurality of clear channel assessments (CCAs) on an unlicensed radio frequency spectrum band during the time window; and transmitting the synchronization signal over the unlicensed radio frequency spectrum band at a transmission time during the time window. The transmission time may be based at least in part on a result of at least one of the CCAs.
1. A method for wireless communication, comprising:
receiving at a user equipment (UE) an indication of a time window associated with a transmission of a synchronization signal; and
monitoring a shared radio frequency spectrum band during the time window to receive the synchronization signal from a base station, wherein the time window comprises one or more periodic fixed locations and the synchronization signal is subject to clear channel assessment (CCA) from the base station.
2. The method of claim 1 , wherein monitoring the shared radio frequency spectrum band during the time window comprises:
waking up a receiver of the UE from a sleep state prior to the time window.
3. The method of claim 1 , further comprising:
receiving, during the time window, timing information from the base station, the timing information comprising an indication from one from a group consisting of: a current frame of the base station, a current subframe of the base station, or a current symbol.
4. The method of claim 3 , further comprising:
synchronizing the UE with the base station based at least in part on the timing information.
5. The method of claim 1 , further comprising:
monitoring the shared radio frequency spectrum band during a clear channel assessment (CCA)-exempt transmission (CET) of the base station to receive the synchronization signal from the base station.
6. The method of claim 1 , wherein the time window is associated with a different set of subcarrier frequencies of the shared radio frequency spectrum band than the transmission subject to CCA.
7. The method of claim 1 , wherein the time window replaces at least one clear channel assessment (CCA)-exempt transmission (CET) of the base station.
8. The method of claim 1 , wherein the indication of the time window is received in a system information block or a master information block.
9. The method of claim 1 , wherein the indication of the time window is received in a radio resource control (RRC) message.
10. The method of claim 1 , further comprising:
receiving system information for the base station during the time window, the system information received in a system information block or a master information block.
11. The method of claim 1 , further comprising:
performing radio resource management measurements on the synchronization signal.
12. The method of claim 1 , wherein the synchronization signal comprises one from a group consisting of: a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a cell-specific reference signal (CRS), and a channel state information reference signal (CSI-RS).
13. An apparatus for wireless communication, comprising:
means for receiving at a user equipment (UE) an indication of a time window associated with a transmission of a synchronization signal; and
means for monitoring a shared radio frequency spectrum band during the time window to receive the synchronization signal from a base station, wherein the time window comprises one or more periodic fixed locations and the synchronization signal is subject to clear channel assessment (CCA) from the base station.
14. The apparatus of claim 13 , wherein monitoring the shared radio frequency spectrum band during the time window comprises:
means for waking up a receiver of the UE from a sleep state prior to the time window.
15. The apparatus of claim 13 , further comprising:
means for receiving, during the time window, timing information from the base station, the timing information comprising an indication from one of a group consisting of: a current frame of the base station, a current subframe of the base station, or a current symbol.
16. The apparatus of claim 15 , further comprising:
means for synchronizing the UE with the base station based at least in part on the timing information.
17. The apparatus of claim 13 , further comprising:
means for monitoring the shared radio frequency spectrum band during a clear channel assessment (CCA)-exempt transmission (CET) of the base station to receive the synchronization signal from the base station.
18. The apparatus of claim 13 , further comprising:
means for monitoring the shared radio frequency spectrum band during a periodic fixed location to receive a transmission of the synchronization signal subject to CCA from the base station.
19. The apparatus of claim 18 , wherein the time window is associated with a different set of subcarrier frequencies of the shared radio frequency spectrum band than the transmission subject to CCA.
20. The apparatus of claim 13 , wherein the time window replaces at least one clear channel assessment (CCA)-exempt transmission (CET) of the base station.
21. The apparatus of claim 13 , wherein the indication of the time window is received in a system information block or a master information block.
22. The apparatus of claim 13 , wherein the indication of the time window is received in a radio resource control (RRC) message.
23. The apparatus of claim 13 , further comprising:
means for receiving system information for the base station during the time window, the system information received in a system information block or a master information block.
24. The apparatus of claim 13 , further comprising:
means for performing radio resource management measurements on the synchronization signal.
25. The apparatus of claim 13 , wherein the synchronization signal comprises one from a group consisting of: a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a cell-specific reference signal (CRS), and a channel state information reference signal (CSI-RS).
26. An apparatus for wireless communication, comprising:
a processor; and
memory coupled to the processor, wherein the processor is configured to:
receive at a user equipment (UE) an indication of a time window associated with a transmission of a synchronization signal; and
monitor a shared radio frequency spectrum band during the time window to receive the synchronization signal from a base station, wherein the time window comprises one or more periodic fixed locations and the synchronization signal is subject to clear channel assessment (CCA) from the base station.
27. The apparatus of claim 26 , wherein the processor is configured to:
wake up a receiver of the UE from a sleep state prior to the time window.
28. The apparatus of claim 26 , wherein the processor is configured to:
receive, during the time window, timing information from the base station, the timing information comprising an indication from one of a group consisting of: a current frame of the base station, a current subframe of the base station, or a current symbol.
29. The apparatus of claim 28 , wherein the processor is configured to:
synchronize the UE with the base station based at least in part on the timing information.
30. The apparatus of claim 26 , wherein the processor is configured to:
monitor the shared radio frequency spectrum band during a clear channel assessment (CCA)-exempt transmission (CET) of the base station to receive the synchronization signal from the base station.
31. The apparatus of claim 26 , wherein the processor is configured to:
monitor the shared radio frequency spectrum band during a periodic fixed location to receive a transmission of the synchronization signal subject to CCA from the base station.
32. The apparatus of claim 26 , wherein the processor is configured to:
receive system information for the base station during the time window, the system information received in a system information block or a master information block.
33. The apparatus of claim 26 , wherein the synchronization signal comprises one from a group consisting of: a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a cell-specific reference signal (CRS), and a channel state information reference signal (CSI-RS).
34. A non-transitory computer-readable medium for storing instructions executable by a processor, comprising:
instructions to receive at a user equipment (UE) an indication of a time window associated with a transmission of a synchronization signal; and
instructions to monitor a shared radio frequency spectrum band during the time window to receive the synchronization signal from a base station, wherein the time window comprises one or more periodic fixed locations and the synchronization signal is subject to clear channel assessment (CCA) from the base station.
35. The non-transitory computer-readable medium of claim 34 , wherein the instructions to monitor the shared radio frequency spectrum band during the time window comprise:
instructions to wake up a receiver of the UE from a sleep state prior to the time window.
36. The non-transitory computer-readable medium of claim 34 , further comprising:
instructions to receive, during the time window, timing information from the base station, the timing information comprising an indication from one of a group consisting of: a current frame of the base station, a current subframe of the base station, or a current symbol.
37. The non-transitory computer-readable medium of claim 34 , wherein the synchronization signal comprises one from a group consisting of: a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a cell-specific reference signal (CRS), and a channel state information reference signal (CSI-RS).