Listen before transmit (LBT) communication protocol for vehicle-to-vehicle communications

1. A method for communication, comprising:

accessing all sub-channels in a communication frame;

generating a counter that counts down beginning with a received first listen before talk (LBT) communication symbol, the counter decrementing by one for each received LBT communication symbol;

determining whether the counter reaches zero before receiving a second LBT communication symbol;

determining whether a desired number N of contiguous sub-channels are available in a communication resource bandwidth, the communication resource bandwidth comprising time and frequency resources corresponding to time and frequency resources used by each LBT communication symbol and a data communication channel; and

if the desired number N of contiguous sub-channels are available, transmitting an LBT symbol using the N contiguous sub-channels.

2. The method of claim 1 , further comprising:

if the desired number N of contiguous sub-channels are available, determining whether more than one set of the desired number N of contiguous sub-channels are available.

3. The method of claim 2 , further comprising:

if more than one set of the desired number N of contiguous sub-channels are available, transmitting the LBT symbol on the contiguous sub-channels lowest in frequency.

4. The method of claim 2 , further comprising:

progressing through available sub-channels using a sliding window of an integer number of sub-channels.

5. The method of claim 1 , further comprising:

if the desired number N of contiguous sub-channels are not available, determining whether a smaller number of contiguous sub-channels are available.

6. The method of claim 5 , further comprising:

if a smaller number of contiguous sub-channels are available, transmitting the LBT symbol on the available contiguous sub-channels.

7. An apparatus for communication, comprising:

a transmitter configured to access all sub-channels in a communication frame;

a processor configured to generate a counter that counts down beginning with a received first listen before talk (LBT) communication symbol, the counter configured to decrement by one for each received LBT communication symbol;

the processor configured to determine whether the counter reaches zero before receiving a second LBT communication symbol;

the transmitter configured to determine whether a desired number N of contiguous sub-channels are available in a communication resource bandwidth, the communication resource bandwidth comprising time and frequency resources corresponding to time and frequency resources used by each LBT communication symbol and a data communication channel; and

if the desired number N of contiguous sub-channels are available, the transmitter configured to transmit an LBT symbol using the N contiguous sub-channels.

8. The apparatus of claim 7 , further comprising:

if the desired number N of contiguous sub-channels are available, the transmitter configured to determine whether more than one set of the desired number N of contiguous sub-channels are available.

9. The apparatus of claim 8 , further comprising:

if more than one set of the desired number N of contiguous sub-channels are available, the transmitter configured to transmit the LBT symbol on the contiguous sub-channels lowest in frequency.

10. The apparatus of claim 8 , further comprising:

the processor configured to progress through available sub-channels using a sliding window of an integer number of sub-channels.

11. The apparatus of claim 7 , further comprising:

if the desired number N of contiguous sub-channels are not available, the transmitter configured to determine whether a smaller number of contiguous sub-channels are available.

12. The apparatus of claim 11 , further comprising:

if a smaller number of contiguous sub-channels are available, the transmitter configured to transmit the LBT symbol on the available contiguous sub-channels.

13. A device, comprising:

means for accessing all sub-channels in a communication frame;

means for generating a counter that counts down beginning with a received first listen before talk (LBT) communication symbol, the counter decrementing by one for each received LBT communication symbol;

means for determining whether the counter reaches zero before receiving a second LBT communication symbol;

means for determining whether a desired number N of contiguous sub-channels are available in a communication resource bandwidth, the communication resource bandwidth comprising time and frequency resources corresponding to time and frequency resources used by each LBT communication symbol and a data communication channel; and

if the desired number N of contiguous sub-channels are available, means for transmitting an LBT symbol using the N contiguous sub-channels.

14. The device of claim 13 , further comprising:

if the desired number N of contiguous sub-channels are available, means for determining whether more than one set of the desired number N of contiguous sub-channels are available.

15. The device of claim 14 , further comprising:

if more than one set of the desired number N of contiguous sub-channels are available, means for transmitting the LBT symbol on the contiguous sub-channels lowest in frequency.

16. The device of claim 14 , further comprising:

means for progressing through available sub-channels using a sliding window of an integer number of sub-channels.

17. The device of claim 13 , further comprising:

if the desired number N of contiguous sub-channels are not available, means for determining whether a smaller number of contiguous sub-channels are available.

18. The device of claim 17 , further comprising:

if a smaller number of contiguous sub-channels are available, means for transmitting the LBT symbol on the available contiguous sub-channels.

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

access all sub-channels in a communication frame;

generate a counter that counts down beginning with a received first listen before talk (LBT) communication symbol, the counter decrementing by one for each received LBT communication symbol;

determine whether the counter reaches zero before receiving a second LBT communication symbol;

determine whether a desired number N of contiguous sub-channels are available in a communication resource bandwidth, the communication resource bandwidth comprising time and frequency resources corresponding to time and frequency resources used by each LBT communication symbol and a data communication channel; and

if the desired number N of contiguous sub-channels are available, transmit an LBT symbol using the N contiguous sub-channels.

20. The non-transitory computer-readable medium of claim 19 , the code executable by a processor to:

if the desired number N of contiguous sub-channels are available, determine whether more than one set of the desired number N of contiguous sub-channels are available.

21. The non-transitory computer-readable medium of claim 20 , wherein the code is executable by a processor to:

if more than one set of the desired number N of contiguous sub-channels are available, transmit the LBT symbol on the contiguous sub-channels lowest in frequency.

22. The non-transitory computer-readable medium of claim 20 , wherein the code is executable by a processor to:

progress through available sub-channels using a sliding window of an integer number of sub-channels.

23. The non-transitory computer-readable medium of claim 19 , wherein the code is executable by a processor to:

if the desired number N of contiguous sub-channels are not available, determine whether a smaller number of contiguous sub-channels are available.

24. The non-transitory computer-readable medium of claim 23 , wherein the code is executable by a processor to:

if a smaller number of contiguous sub-channels are available, transmit the LBT symbol on the available contiguous sub-channels.