Contention-based co-existence on a shared communication medium

1. A communication method, comprising:

receiving information over a communication medium in accordance with a Time Division Duplexing (TDD) frame structure defining a series of frames and subframes;

determining a set of subframe resources within a subframe for carrying an acknowledgment channel over the communication medium, wherein the determined set of subframe resources occupies no more than a threshold fraction of the subframe and is spread in frequency over one or more interleaved blocks of OFDM tones; and

transmitting one or more acknowledgment messages associated with the received information over the acknowledgment channel via the determined set of subframe resources.

2. The communication method of claim 1 , wherein the threshold fraction of the subframe comprises two or fewer Orthogonal Frequency Division Multiplexed (OFDM) symbol periods.

3. The communication method of claim 1 , wherein the threshold fraction of the subframe corresponds to a contention-free period of time.

4. The communication method of claim 3 , wherein the contention-free period of time spans 5% or less of a duration of a frame defined by the TDD frame structure.

5. The method of claim 1 , wherein:

the receiving comprises:

receiving information on a first group of one or more downlink subframes, and

receiving information on a second group of one or more downlink subframes; and

the transmitting comprises:

transmitting an acknowledgment message on a first uplink subframe acknowledging the information received on the first group of one or more downlink subframes, and

transmitting an acknowledgment message on a second uplink subframe after the first uplink subframe acknowledging the information received on the second group of one or more downlink subframes and the information received on the first group of one or more downlink subframes.

6. The method of claim 1 , further comprising:

determining that the information is not received successfully during a first transmission opportunity (TXOP);

transmitting a positive acknowledgment message associated with the information to an access terminal over the acknowledgment channel based on the determining;

refraining from transmitting any transmission grants to the access terminal over a common control channel based on the determining; and

receiving, during a second TXOP, a retransmission of the information.

7. The method of claim 6 , wherein the first TXOP and the second TXOP are discontinuous in time.

8. The communication method of claim 1 , wherein the set of subframe resources includes a first OFDM tone and a second OFDM tone, wherein a third OFDM tone between the first OFDM tone and the second OFDM tone is not included in the set of subframe resources.

9. A communication apparatus, comprising:

at least one transceiver configured to receive information over a communication medium in accordance with a Time Division Duplexing (TDD) frame structure defining a series of frames and subframes;

at least one processor, and

at least one memory coupled to the at least one processor, the at least one processor and the at least one memory being configured to determine a set of subframe resources within a subframe for carrying an acknowledgment channel over the communication medium, wherein the determined set of subframe resources occupies no more than a threshold fraction of the subframe and is spread in frequency over one or more interleaved blocks of OFDM tones,

wherein the at least one transceiver is further configured to transmit one or more acknowledgment messages associated with the received information over the acknowledgment channel via the determined set of subframe resources.

10. The communication apparatus of claim 9 , wherein the threshold fraction of the subframe comprises two or fewer Orthogonal Frequency Division Multiplexed (OFDM) symbol periods.

11. The communication apparatus of claim 9 , wherein the threshold fraction of the subframe corresponds to a contention-free period of time.

12. The communication apparatus of claim 11 , wherein the contention-free period of time spans 5% or less of a duration of a frame defined by the TDD frame structure.

13. The apparatus of claim 9 , wherein the at least one transceiver is further configured to:

receive information on a first group of one or more downlink subframes;

receive information on a second group of one or more downlink subframes;

transmit an acknowledgment message on a first uplink subframe acknowledging the information received on the first group of one or more downlink subframes; and

transmit an acknowledgment message on a second uplink subframe after the first uplink subframe acknowledging the information received on the second group of one or more downlink subframes and the information received on the first group of one or more downlink subframes.

14. The apparatus of claim 9 , wherein:

the at least one processor and the at least one memory are further configured to determine that the information is not received successfully during a first transmission opportunity (TXOP); and

the at least one transceiver is further configured to:

transmit a positive acknowledgment message associated with the information to an access terminal over the acknowledgment channel based on the determining,

refrain from transmitting any transmission grants to the access terminal over a common control channel based on the determining, and

receive, during a second TXOP, a retransmission of the information.

15. The apparatus of claim 14 , wherein the first TXOP and the second TXOP are discontinuous in time.

16. A communication apparatus, comprising:

means for receiving information over a communication medium in accordance with a Time Division Duplexing (TDD) frame structure defining a series of frames and subframes;

means for determining a set of subframe resources within a subframe for carrying an acknowledgment channel over the communication medium, wherein the determined set of subframe resources occupies no more than a threshold fraction of the subframe and is spread in frequency over one or more interleaved blocks of OFDM tones; and

means for transmitting one or more acknowledgment messages associated with the received information over the acknowledgment channel via the determined set of subframe resources.

17. The communication apparatus of claim 16 , wherein the threshold fraction of the subframe comprises two or fewer Orthogonal Frequency Division Multiplexed (OFDM) symbol periods.

18. The communication apparatus of claim 16 , wherein the threshold fraction of the subframe corresponds to a contention-free period of time.

19. The communication apparatus of claim 18 , wherein the contention-free period of time spans 5% or less of a duration of a frame defined by the TDD frame structure.

20. The apparatus of claim 16 , wherein:

the means for receiving comprises:

means for receiving information on a first group of one or more downlink subframes, and

means for receiving information on a second group of one or more downlink subframes; and

the means for transmitting comprises:

means for transmitting an acknowledgment message on a first uplink subframe acknowledging the information received on the first group of one or more downlink subframes, and

means for transmitting an acknowledgment message on a second uplink subframe after the first uplink subframe acknowledging the information received on the second group of one or more downlink subframes and the information received on the first group of one or more downlink subframes.

21. The apparatus of claim 16 , further comprising:

means for determining that the information is not received successfully during a first transmission opportunity (TXOP);

means for transmitting a positive acknowledgment message associated with the information to an access terminal over the acknowledgment channel based on the determining;

means for refraining from transmitting any transmission grants to the access terminal over a common control channel based on the determining; and

means for receiving, during a second TXOP, a retransmission of the information.

22. A non-transitory computer-readable medium comprising code, which, when executed by a processor, causes the processor to perform operations for communication, the non-transitory computer-readable medium comprising:

code for receiving information over a communication medium in accordance with a Time Division Duplexing (TDD) frame structure defining a series of frames and subframes;

code for determining a set of subframe resources within a subframe for carrying an acknowledgment channel over the communication medium, wherein the determined set of subframe resources occupies no more than a threshold fraction of the subframe and is spread in frequency over one or more interleaved blocks of OFDM tones; and

code for transmitting one or more acknowledgment messages associated with the received information over the acknowledgment channel via the determined set of subframe resources.

23. The non-transitory computer-readable medium of claim 22 , wherein the threshold fraction of the subframe comprises two or fewer Orthogonal Frequency Division Multiplexed (OFDM) symbol periods.

24. The non-transitory computer-readable medium of claim 22 , wherein the threshold fraction of the subframe corresponds to a contention-free period of time.

25. The non-transitory computer-readable medium of claim 24 , wherein the contention-free period of time spans 5% or less of a duration of a frame defined by the TDD frame structure.

26. The non-transitory computer-readable medium of claim 22 , wherein:

the code for receiving comprises:

code for receiving information on a first group of one or more downlink subframes, and

code for receiving information on a second group of one or more downlink subframes; and

the code for transmitting comprises:

code for transmitting an acknowledgment message on a first uplink subframe acknowledging the information received on the first group of one or more downlink subframes, and

code for transmitting an acknowledgment message on a second uplink subframe after the first uplink subframe acknowledging the information received on the second group of one or more downlink subframes and the information received on the first group of one or more downlink subframes.

27. The non-transitory computer-readable medium of claim 22 , further comprising:

code for determining that the information is not received successfully during a first transmission opportunity (TXOP);

code for transmitting a positive acknowledgment message associated with the information to an access terminal over the acknowledgment channel based on the determining;

code for refraining from transmitting any transmission grants to the access terminal over a common control channel based on the determining; and

means for receiving, during a second TXOP, a retransmission of the information.