Dynamic Clear Channel Assessment Using Spectrum Intelligent Interference Nulling

• US 20130012134A1
• Filed: 07/07/2011
• Published: 01/10/2013
• Est. Priority Date: 07/07/2011
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Jin, Hang, Guo, Li, Stager, Paul J., Diener, Neil R., Silverman, Matthew A.
• Granted Patent: US 8,718,560 B2
• Time in Patent Office: Days
• US Class Current: 455/62
• CPC Class Codes: H04B 17/345 Interference values signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] H04B17/336
• CPC Class Codes: H04B 7/0845 per branch equalization, e.g. by an FIR-filter or RAKE receiver per antenna branch rake receivers as such H04B1/7115

Abstract

At a wireless device operating in an unlicensed frequency band, energy received at a plurality of antennas is analyzed to detect interference on a channel in the unlicensed frequency band. The type of interference detected in the received energy is determined. Parameters are then generated for a nulling filter based on the type of interference detected in the received energy. The nulling filter is applied to the received energy at the plurality of antennas to produce a spatially filtered output. The spatially filtered output is evaluated to determine whether to send a transmission on the channel in the unlicensed frequency band.

Claims

1. A method comprising:

at a wireless device, analyzing energy received at a plurality of antennas in an unlicensed frequency band to detect interference on a channel in the unlicensed frequency band;

determining the type of interference detected in the received energy;

generating parameters for a nulling filter based on the type of interference detected in the received energy;

applying the nulling filter to received energy at the plurality of antennas to produce a spatially filtered output; and

evaluating the spatially filtered output to determine whether to send a transmission on the channel in the unlicensed frequency band.

2. The method of claim 1, wherein evaluating comprises comparing a level of the spatially filtered output with a threshold.

3. The method of claim 2, wherein comparing comprises comparing the level of the spatially filtered output with a clear channel assessment threshold.

4. The method of claim 2, and further comprising refraining from sending the transmission in the channel when the level of the spatially filtered output is greater than the threshold.

5. The method of claim 1, wherein evaluating comprises evaluating the received energy prior to applying the nulling filter, the spatially filtered output and the type of interference detected in the received energy.

6. The method of claim 5, wherein when it is determined that the received energy contains a wireless network transmission, evaluating comprises comparing a level of the spatially filtered output with a first threshold.

7. The method of claim 5, wherein when it is determined that the received energy does not contain a wireless network transmission, evaluating comprises comparing a level of the received energy prior to applying the nulling filter with a second threshold.

8. The method of claim 7 and further comprising setting the second threshold to a first value when the type of interference is a first type, and setting the second threshold to a second value when the type of interference is a type other than the first type.

9. The method of claim 8, wherein setting comprises setting the second threshold to the first value which is based on an energy detect threshold without considering any gain associated with the nulling filter, and setting the second threshold to a second value which is based on a sum of the first value and a difference between the received energy prior to applying the nulling filter and a spatially filtered output.

10. An apparatus comprising:

a plurality of antennas;

a radio receiver coupled to the plurality of antennas and configured to downconvert signals detected by the plurality of antennas in an unlicensed frequency band;

a radio transmitter configured to transmit signals via at least one of the plurality of antennas;

a spectrum analyzer unit configured to analyze signals output by the radio receiver for at least one antenna to detect interference in the unlicensed frequency band; and

a processor coupled to the radio receiver, spectrum analyzer unit and radio transmitter, and configured to;

analyze energy received at a plurality of antennas to determine the type of interference detected in the received energy;

generate parameters for a nulling filter based on the type of interference in the received energy;

apply the nulling filter to received energy at the plurality of antennas to produce a spatially filtered output; and

evaluate the spatially filtered output to determine whether to send a transmission on the channel in the unlicensed frequency band.

11. The apparatus of claim 10, wherein the processor is configured to compare a level of the spatially filtered output with a threshold, and to refrain from sending the transmission in the channel when the level of the spatially filtered output is greater than the threshold.

12. The apparatus of claim 11, wherein the processor is configured to evaluate by evaluating the received energy prior to applying the nulling filter, the spatially filtered output and the type of interference detected in the received energy.

13. The apparatus of claim 12, wherein the processor is configured to compare a level of the spatially filtered output with a first threshold when it is determined that the received energy contains a wireless network transmission.

14. The apparatus of claim 12, wherein the processor is configured to compare a level of the received energy with a second threshold prior to applying the nulling filter, when it is determined that the received energy does not contain a wireless network transmission.

15. The apparatus of claim 14, wherein the processor is configured to set the second threshold to a first value when the type of interference is a first type, and setting the second threshold to a second value when the type of interference is a type other than the first type.

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

analyze energy received at a plurality of antennas of a wireless device to detect interference on a channel in an unlicensed frequency band;

determine the type of interference detected in the received energy;

generate parameters for a nulling filter based on the type of interference in the received energy;

apply the nulling filter to received energy at the plurality of antennas to produce a spatially filtered output; and

evaluate the spatially filtered output to determine whether to send a transmission on the channel in the unlicensed frequency band.

17. The computer readable storage media of claim 16, wherein the instructions that are operable to evaluate comprise instructions that are operable to compare a level of the spatially filtered output with a threshold, and to refrain from sending the transmission in the channel when the level of the spatially filtered output is greater than the threshold.

18. The computer readable storage media of claim 17, wherein the instructions that are operable to evaluate comprise instructions that are operable to evaluate the received energy prior to applying the nulling filter, the spatially filtered output and the type of interference detected in the received energy.

19. The computer readable storage media of claim 18, wherein the instructions that are operable to evaluate comprise instructions that are operable to compare a level of the spatially filtered output with a first threshold when it is determined that the received energy contains a wireless network transmission.

20. The computer readable storage media of claim 18, wherein the instructions that are operable to evaluate comprise instructions that are operable to compare a level of the received energy with a second threshold prior to applying the nulling filter when it is determined that the received energy does not contain a wireless network transmission.