Mitigating effects of identified interference with adaptive CCA threshold

• US 8,666,319 B2
• Filed: 07/15/2011
• Issued: 03/04/2014
• Est. Priority Date: 07/15/2011
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Kloper, David, Chan, Douglas, Stiff, David
• Primary Examiner(s): WEST, LEWIS G
• Application Number:
  US13/183,506
• Publication Number:
  US 20130017794A1
• Time in Patent Office: 963 Days
• Field of Search: 455/63.1, 455/67.11, 455/67.14
• US Class Current: 455/63.1
• CPC Class Codes: H04W 72/541 using the level of interference
• CPC Class Codes: H04W 74/006 in the downlink, i.e. towards the terminal
• CPC Class Codes: H04W 74/0808 using carrier sensing, e.g. carrier sense multiple access [CSMA]

Abstract

Techniques are provided to adaptively adjust a clear channel assessment threshold for use when a wireless device is to transmit in a wireless network that operates on a channel in a radio frequency band. A first wireless device, configured to wirelessly communicate with one or more second wireless device in the wireless network, receives energy on the channel in the frequency band, analyzes the received energy to detect interference on the channel and determines a type of interference detected in the received energy. The clear channel assessment threshold is adjusted by an amount depending on the type of interference detected.

Claims

1. A method comprising:

at a first wireless device that is configured to wirelessly communicate with one or more second wireless devices in a wireless network in a frequency band, receiving energy on a channel in the frequency band;

analyzing received energy to detect interference on the channel, including two or more interferers in the frequency band;

determining a type, a receive signal strength, and a duty cycle for each of the two or more interferers;

adjusting a clear channel assessment threshold used when accessing the channel by an amount depending on the type of interference detected, the adjusting including;

determining a proposed new channel assessment threshold individually for each interferer; and

determining an overall clear channel assessment threshold from the proposed new channel assessment thresholds for the individual interferers;

computing a projected throughput improvement based on the overall clear channel assessment threshold; and

using the proposed new clear channel assessment threshold at the first wireless device and/or one or more second wireless devices.

2. The method of claim 1, wherein the using further comprises using the proposed new clear channel assessment threshold at the first wireless device and/or second wireless device when the projected throughput improvement satisfies the predetermined criterion.

3. The method of claim 2, wherein computing the projected throughput improvement is based on at least one of:

the type of the interference and a radio frequency signature of the interference.

4. The method of claim 3, wherein computing the projected throughput improvement is based further on a duty cycle of the interference.

5. The method of claim 4, wherein computing the projected throughput improvement is based further on receive signal strength statistics that indicate that the receive signal strength associated with the interference is higher during certain time intervals than during other time intervals.

6. The method of claim 2, wherein adjusting comprises not increasing the clear channel assessment threshold when the projected throughput improvement does not satisfy the predetermined criterion.

7. The method of claim 1, and further comprising generating receive signal strength statistics that indicate that the receive signal strength associated with the interference is higher during certain time intervals than during other time intervals, and wherein adjusting comprises adjusting the clear channel assessment threshold to a value that is lower than the higher receive signal strength of the interference so that during some time intervals the interference is respected and during other time intervals a transmission is made over the interference.

8. The method of claim 1, and further comprising transmitting from the first wireless device to one or more of the second wireless devices a message containing information indicating a new clear channel threshold to be used by one or more of the second wireless devices when transmitting to the first wireless device.

9. The method of claim 1, and further comprising storing information at the first wireless device indicating one or more types of interferers in the presence of which adjustment of the clear channel assessment threshold is not made or is made up to a specific limit.

10. The method of claim 1, wherein adjusting comprises adjusting the clear channel assessment threshold by an amount that depends on the impact that the type of interference has on the wireless network.

11. The method of claim 1, and further comprising determining a clear channel assessment threshold that is specific to a particular second wireless device based on a location of the particular second wireless device relative to a location of a source of detected interference, and transmitting from the first wireless device to the particular second wireless device a message containing information indicating the clear channel assessment threshold to be used by the particular second wireless device when transmitting to the first wireless client device.

12. The method of claim 11, and further comprising computing a transmit power level to be used by the first wireless device when transmitting to the particular second wireless device or by the particular second wireless device when transmitting to the first wireless device based on a location of the particular second wireless device relative to the location of the source of the interference.

13. An apparatus comprising:

a radio receiver configured to downconvert received energy in a channel in a frequency band allocated for wireless communication in a wireless network;

a processor configured to;

analyze signals output by the radio receiver to detect interference on the channel, including two or more interferers in the frequency band;

determine a type, a receive signal strength, and a duty cycle for each of the two or more interferers;

adjust a clear channel assessment threshold used when accessing the channel by an amount depending on the type of interference by determining a proposed new clear channel assessment threshold individually for each interferer;

determine an overall clear channel assessment threshold from the proposed new channel assessment thresholds for the individual interferers; and

compute a projected throughput improvement based on the overall clear channel assessment threshold.

14. The apparatus of claim 13, and further comprising a spectrum analyzer unit coupled to the radio receiver and configured to analyze the received energy, and wherein the processor is configured to analyze data output by the spectrum analyzer unit in order to determine the type of interference detected in the received energy.

15. The apparatus of claim 14, wherein the processor is configured to compute the projected throughput improvement based on the type of the interference.

16. The apparatus of claim 15, wherein the processor is configured to compute the projected throughput improvement based further on a duty cycle of the interference.

17. The apparatus of claim 16, wherein the processor is configured to compute the projected throughput improvement based further on receive signal strength statistics that indicate that the receive signal strength associated with the interference is higher during certain time intervals than during other time intervals.

18. The apparatus of claim 13, wherein the processor is configured to generate receive signal strength statistics that indicate that the receive signal strength associated with the interference is higher during certain time intervals than during other time intervals, and to adjust the clear channel assessment threshold to a value that is lower than the higher receive signal strength of the interference so that during some time intervals the interference is respected and during other time intervals a transmission is made over the interference.

19. One or more computer readable storage media encoded with software comprising computer executable instructions and when the software is executed operable to:

analyze signals output by a radio receiver to detect interference on a channel in a radio frequency band, including two or more interferers in the frequency band;

determine a type, a receive signal strength, and a duty cycle for each of the two or more interferers;

adjust a clear channel assessment threshold by an amount depending on the type of interference when a wireless device accesses the channel in a wireless network operating on the channel in the radio frequency band by determining a proposed new clear channel assessment threshold individually for each interferer;

determine an overall clear channel assessment threshold from the proposed new channel assessment thresholds for the individual interferers; and

compute a projected throughput improvement based on the overall clear channel assessment threshold.

20. The computer readable storage media of claim 19, and further comprising instructions configured to determine whether the projected throughput improvement satisfies at least one predetermined criterion, and use the proposed new clear channel assessment threshold when the projected throughput improvement satisfies the predetermined criterion.

21. The computer readable storage media of claim 20, wherein the instructions that are operable to determine the proposed new clear channel assessment threshold comprise instructions operable to determine the proposed new clear channel assessment threshold based on the type, duty cycle and receive signal strength of the interference.

22. The computer readable storage media of claim 19, and further comprising instructions operable to generate receive signal strength statistics that indicate that the receive signal strength associated with the interference is higher during certain time intervals than during other time intervals, and the instructions that are operable to adjust comprise instructions operable to adjust the clear channel assessment threshold to a value that is lower than the higher receive signal strength of the interference so that during some time intervals the interference is respected and during other time intervals a transmission is made over the interference.