Wireless communication apparatus and interference detection method

1. A wireless communication apparatus comprising:

a first determination unit which determines based on a first carrier sense threshold whether a busy state is indicated, specifies a first time when the busy state is determined based on the first carrier sense threshold, determines based on a second carrier sense threshold which is smaller than the first carrier sense threshold whether a busy state is indicated, and specifies a second time when the busy state is determined based on the second carrier sense threshold; and

a second determination unit which determines, if at least the busy state is determined based on the second carrier sense threshold and the second time precedes a reference time equal to or earlier than the first time, to perform processing for avoiding interference.

2. The apparatus according to claim 1 , further comprising a receiving unit which performs reception processing for a frame, determines whether an error has occurred in the received frame, and sends error information,

wherein if the error information is received, an error has occurred in the received frame, the busy state is determined based on the second carrier sense threshold, and the second time precedes the reference time, the second determination unit determines to perform the processing for avoiding interference.

3. The apparatus according to claim 2 , wherein if it is identified based on the error information that the error has occurred in the received frame, the second determination unit sends, to the first determination unit, the first carrier sense threshold, the second carrier sense threshold, and an instruction to determine whether the busy state is determined based on the first carrier sense threshold and to specify a busy time when the busy state is determined based on the first carrier sense threshold and to determine whether the busy state is determined based on the second carrier sense threshold and to specify a busy time when the busy state is determined based on the second carrier sense threshold.

4. The apparatus according to claim 1 , wherein the reference time is the first time.

5. The apparatus according to claim 1 , wherein the reference time is a time when it is expected that a carrier sense determines a busy state based on the first carrier sense threshold.

6. The apparatus according to claim 5 , wherein the reference time, which is the time when it is expected that the carrier sense determines a busy state based on the first carrier sense threshold, is a time when a fixed period of time elapses after frame transmission processing is completed.

7. The apparatus according to claim 1 , further comprising:

a transmitting unit which performs transmission processing for a frame, and

a timer unit which manages at least one timer to be used for transmission/reception processing, and which starts, when the frame transmission processing by the transmitting unit is completed, a timer for expecting response frame reception, and notifies, when a time-out of the timer occurs, the first determination unit of the time-out,

wherein if the second time precedes a time when the timer unit notifies that the time-out has occurred, the second determination unit determines to perform the processing for avoiding interference.

8. The apparatus according to claim 1 , further comprising:

a demodulation unit which performs demodulation, and

a MAC processing unit which performs MAC processing,

wherein the MAC processing unit includes the first determination unit, and

wherein the demodulation unit or the MAC processing unit includes the second determination unit.

9. The apparatus according to claim 1 , wherein the second carrier sense threshold is determined based on a received signal strength indicator, a signal-to-interference-plus-noise ratio, and a required signal-to-interference-plus-noise ratio.

10. The apparatus according to claim 1 , further comprising at least one antenna.

11. An interference detection method for a wireless communication apparatus, comprising:

determining based on a first carrier sense threshold whether a busy state is indicated;

specifying a first time when the busy state is determined based on the first carrier sense threshold;

determining based on a second carrier sense threshold which is smaller than the first carrier sense threshold whether a busy state is indicated;

specifying a second time when the busy state is determined based on the second carrier sense threshold; and

determining, if at least the busy state is determined based on the second carrier sense threshold and the second time precedes a reference time equal to or earlier than the first time, to perform processing for avoiding interference.

12. The method according to claim 11 , wherein the wireless communication apparatus comprises a first determination unit and a second determination unit, and

wherein the method comprises:

performing, with the first determination unit, said determining based on the first carrier sense threshold whether a busy state is indicated, said specifying the first time when the busy state is determined based on the first carrier sense threshold, said determining based on the second carrier sense threshold whether a busy state is indicated, and said specifying the second time when the busy state is determined based on the second carrier sense threshold, and

performing, with the second determination unit, said determining, if at least the busy state is determined based on the second carrier sense threshold and the second time precedes the reference time equal to or earlier than the first time, to perform processing for avoiding interference.

13. The method according to claim 12 , further comprising performing reception processing for a frame, determining whether an error has occurred in the received frame, and sending error information,

wherein if the error information is received, an error has occurred in the received frame, the busy state is determined based on the second carrier sense threshold, and the second time precedes the reference time, it is determined to perform the processing for avoiding interference.

14. The apparatus according to claim 13 , wherein if it is identified based on the error information that the error has occurred in the received frame, the method comprises sending, with second determination unit, to the first determination unit, the first carrier sense threshold, the second carrier sense threshold, and an instruction to determine whether the busy state is determined based on the first carrier sense threshold and to specify a busy time when the busy state is determined based on the first carrier sense threshold and to determine whether the busy state is determined based on the second carrier sense threshold and to specify a busy time when the busy state is determined based on the second carrier sense threshold.

15. The method according to claim 11 , wherein the reference time is the first time.

16. The method according to claim 11 , wherein the reference time is a time when it is expected that a carrier sense determines a busy state based on the first carrier sense threshold.

17. The apparatus according to claim 16 , wherein the reference time, which is the time when it is expected that the carrier sense determines a busy state based on the first carrier sense threshold, is a time when a fixed period of time elapses after frame transmission processing is completed.

18. The method according to claim 12 , further comprising:

performing transmission processing for a frame, and

managing at least one timer to be used for transmission/reception processing, and starting, when the frame transmission processing by the transmitting unit is completed, a timer for expecting response frame reception, and notifying, when a time-out of the timer occurs, the first determination unit of the time-out,

wherein if the second time precedes a time of notifying that the time-out has occurred, the second determination unit determines to perform the processing for avoiding interference.

19. The method according to claim 12 , further comprising:

performing, with a demodulation unit, demodulation, and

performing, with a MAC processing unit, MAC processing,

wherein the MAC processing unit includes the first determination unit, and

wherein the demodulation unit or the MAC processing unit includes the second determination unit.

20. The method according to claim 11 , wherein the second carrier sense threshold is determined based on a received signal strength indicator, a signal-to-interference-plus-noise ratio, and a required signal-to-interference-plus-noise ratio.