LISTEN-BEFORE-TALK FOR LTE DIRECT ON UNLICENSED RADIO FREQUENCY SPECTRUM BAND

• US 20170086194A1
• Filed: 09/22/2015
• Published: 03/23/2017
• Est. Priority Date: 09/22/2015
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Tavildar, Saurabha Rangrao, Li, Junyi, Walton, Jay Rodney, Abraham, Santosh Paul
• Granted Patent: US 9,924,511 B2
• Time in Patent Office: Days
• CPC Class Codes: H04L 67/104 Peer-to-peer [P2P] networks
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames
• CPC Class Codes: H04W 72/0453 Resources in frequency domain, e.g. a carrier in FDMA
• CPC Class Codes: H04W 74/0808 using carrier sensing, e.g. carrier sense multiple access [CSMA]
• CPC Class Codes: H04W 76/14 Direct-mode setup
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

Methods, systems, and devices are described for direct device-to-device (D2D) communications in a subframe on a channel in an unlicensed radio frequency spectrum band. A user equipment (UE) may perform a listen-before-talk (LBT) procedure on the channel in the unlicensed radio frequency spectrum band. The UE may identify a time period between a completion of the LBT procedure and a boundary of a second subframe. The UE may transmit a Wi-Fi preamble and a variable length message on the channel during the identified timer period. The variable length message may include a duration that is time aligned with the boundary of the second subframe.

Claims

1. A method for wireless communication, comprising:

performing a listen-before-talk (LBT) procedure on a channel in an unlicensed radio frequency spectrum band;

identifying a time period between a completion of the LBT procedure and a boundary of a second subframe; and

transmitting a Wi-Fi preamble and a variable length message on the channel during the identified time period, the variable length message comprising a duration that is time aligned with the boundary of the second subframe.

2. The method of claim 1, further comprising:

selecting the duration of the variable length message based at least in part on a fixed LBT procedure time, an actual LBT procedure time, and a Wi-Fi preamble time.

3. The method of claim 1, further comprising:

selecting the duration of the variable length message to time align frames transmitted on the channel with frames transmitted on a channel in a licensed radio frequency spectrum band.

4. The method of claim 1, further comprising:

selecting a pseudo-random backoff interval associated with the LBT procedure, the pseudo-random backoff interval selected based at least in part on a system time associated with communications on the channel.

5. The method of claim 1, further comprising:

transmitting a clear-to-send-to-self (CTS-S) information element in the Wi-Fi preamble, the CTS-S information element configured to reserve the channel during a remaining portion of the time period.

6. The method of claim 5, wherein the CTS-S information element comprises a fixed destination address selected to reserve the channel during the remaining portion of the time period.

7. The method of claim 1, further comprising:

decoding, during the LBT procedure, a header portion of one or more received Wi-Fi signals; and

determining that the LBT procedure is complete based at least in part on the decoded header portion.

8. The method of claim 1, wherein the channel is associated with device-to-device (D2D) direct communications in the unlicensed radio frequency spectrum band.

9. An apparatus for wireless communication, comprising:

a processor;

memory in electronic communication with the processor; and

instructions stored in the memory, the instructions being executable by the processor to;

perform a listen-before-talk (LBT) procedure on a channel in an unlicensed radio frequency spectrum band;

identify a time period between a completion of the LBT procedure and a boundary of a second subframe; and

transmit a Wi-Fi preamble and a variable length message on the channel during the identified time period, the variable length message comprising a duration that is time aligned with the boundary of the second subframe.

10. The apparatus of claim 9, further comprising instructions executable by the processor to:

select the duration of the variable length message based at least in part on a fixed LBT procedure time, an actual LBT procedure time, and a Wi-Fi preamble time.

11. The apparatus of claim 9, further comprising instructions executable by the processor to:

select the duration of the variable length message to time align frames transmitted on the channel with frames transmitted on a channel in a licensed radio frequency spectrum band.

12. The apparatus of claim 9, further comprising instructions executable by the processor to:

select a pseudo-random backoff interval associated with the LBT procedure, the pseudo-random backoff interval selected based at least in part on a system time associated with communications on the channel.

13. The apparatus of claim 9, further comprising instructions executable by the processor to:

transmit a clear-to-send-to-self (CTS-S) information element in the Wi-Fi preamble, the CTS-S information element configured to reserve the channel during a remaining portion of the time period.

14. The apparatus of claim 13, wherein the CTS-S information element comprises a fixed destination address selected to reserve the channel during the remaining portion of the time period.

15. The apparatus of claim 9, further comprising instructions executable by the processor to:

decoding, during the LBT procedure, a header portion of one or more received Wi-Fi signals; and

determining that the LBT procedure is complete based at least in part on the decoded header portion.

16. The apparatus of claim 9, wherein the channel is associated with device-to-device (D2D) direct communications in the unlicensed radio frequency spectrum band.

17. An apparatus for wireless communication, comprising:

means for performing a listen-before-talk (LBT) procedure on a channel in an unlicensed radio frequency spectrum band;

means for identifying a time period between a completion of the LBT procedure and a boundary of a second subframe; and

means for transmitting a Wi-Fi preamble and a variable length message on the channel during the identified time period, the variable length message comprising a duration that is time aligned with the boundary of the second subframe.

18. The apparatus of claim 17, further comprising:

means for selecting the duration of the variable length message based at least in part on a fixed LBT procedure time, an actual LBT procedure time, and a Wi-Fi preamble time.

19. The apparatus of claim 17, further comprising:

means for selecting the duration of the variable length message to time align frames transmitted on the channel with frames transmitted on a channel in a licensed radio frequency spectrum band.

20. The apparatus of claim 17, further comprising:

means for selecting a pseudo-random backoff interval associated with the LBT procedure, the pseudo-random backoff interval selected based at least in part on a system time associated with communications on the channel.

21. The apparatus of claim 17, further comprising:

means for transmitting a clear-to-send-to-self (CTS-S) information element in the Wi-Fi preamble, the CTS-S information element configured to reserve the channel during a remaining portion of the time period.

22. The apparatus of claim 21, wherein the CTS-S information element comprises a fixed destination address selected to reserve the channel during the remaining portion of the time period.

23. The apparatus of claim 17, further comprising:

means for decoding, during the LBT procedure, a header portion of one or more received Wi-Fi signals; and

means for determining that the LBT procedure is complete based at least in part on the decoded header portion.

24. The apparatus of claim 17, wherein the channel is associated with device-to-device (D2D) direct communications in the unlicensed radio frequency spectrum band.

25. A non-transitory computer-readable medium storing computer-executable code for wireless communication, the code executable by a processor to:

perform a listen-before-talk (LBT) procedure on a channel in an unlicensed radio frequency spectrum band;

identify a time period between a completion of the LBT procedure and a boundary of a second subframe; and

transmit a Wi-Fi preamble and a variable length message on the channel during the identified time period, the variable length message comprising a duration that is time aligned with the boundary of the second subframe.

26. The non-transitory computer-readable medium of claim 25, further comprising code executable by the processor to:

select the duration of the variable length message based at least in part on a fixed LBT procedure time, an actual LBT procedure time, and a Wi-Fi preamble time.

27. The non-transitory computer-readable medium of claim 25, further comprising code executable by the processor to:

select the duration of the variable length message to time align frames transmitted on the channel with frames transmitted on a channel in a licensed radio frequency spectrum band.

28. The non-transitory computer-readable medium of claim 25, further comprising code executable by the processor to:

select a pseudo-random backoff interval associated with the LBT procedure, the pseudo-random backoff interval selected based at least in part on a system time associated with communications on the channel.

29. The non-transitory computer-readable medium of claim 25, further comprising code executable by the processor to:

transmit a clear-to-send-to-self (CTS-S) information element in the Wi-Fi preamble, the CTS-S information element configured to reserve the channel during a remaining portion of the time period.

30. The non-transitory computer-readable medium of claim 29, wherein the CTS-S information element comprises a fixed destination address selected to reserve the channel during the remaining portion of the time period.