Method and apparatus of low power energy detection for a WLAN

• US 6,760,671 B1
• Filed: 04/09/2002
• Issued: 07/06/2004
• Est. Priority Date: 04/09/2002
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Ecclesine, Peter W., Batcher, Kenneth W.
• Primary Examiner(s): Barlow, John
• Assistant Examiner(s): LE, JOHN H
• Application Number:
  US10/118,985
• Time in Patent Office: 819 Days
• Field of Search: 702/57, 702/60, 702/61, 702/62, 702/63, 702/66, 702/79, 340/286.02, 340/870.1, 370/332, 370/342, 370/350, 370/338, 375/202, 375/346, 455/126, 455/266, 455/423, 455/63
• US Class Current: 702/60
• CPC Class Codes: H04B 1/715 Interference-related aspects
• CPC Class Codes: H04B 17/345 Interference values signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] H04B17/336
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method and implementation disclosed for detecting interference. A state machine controller is provided for establishing an interference detection cycle including a power sample period and a periodic sampling interval. A receiver component, responsive to the state machine controller, performs an energy measurement at a predetermined wireless band during the power sample period. A threshold comparator determines whether the energy measurement exceeds a predetermined threshold. A processing implementation processes the energy measurement to determine whether it corresponds to interference on the predetermined wireless band, if the measurement exceeds the predetermined threshold. A deactivating implementation is used to instruct the state machine controller to await the next power sample period, if the energy measurement does not exceed the predetermined threshold.

Claims

1. A method of detecting interference comprising:

establishing an interference detection cycle, including a power sample period and a periodic sampling interval, wherein during the power sample period;

performing an energy measurement at a predetermined wireless band;

determining whether the energy measurement exceeds a predetermined threshold;

wherein If the energy measurement exceeds the predetermined threshold, processing the energy measurement to determine whether it corresponds to interference on the wireless band by analyzing the waveform characteristics of the energy measurement to determine whether the waveform characteristics are compatible with desired signals, wherein if the waveform characteristics are not compatible, the energy measurement is determined to correspond to interference; and

wherein if the energy measurement does not exceed the predetermined threshold, awaiting the next power sample period.

2. The method of claim 1 wherein the interference detection cycle is established in a circuit that shuts down between power sampling periods within the periodic sampling period.

3. The method of claim 1 wherein the step of performing an energy measurement comprises measuring received signal strength at a 5 GHz wireless band.

4. The method of claim 1 wherein the step of processing the energy measurement comprises activating a processing component and forwarding the energy measurement to the processing component.

5. The method of claim 1 wherein the step of analyzing comprises performing a Fast Fourier Transform on the energy measurement.

6. The method of claim 1 wherein the step of processing comprises determining the direction to the source of the energy measurement.

7. The method of claim 1 wherein the power sample period and the periodic sampling interval are constant over time.

8. The method of claim 7 wherein the power sample period and the periodic sampling interval are selected to be relatively prime so as to detect an interference source having a known frequency.

9. The method of claim 1 wherein at least one of the power sample period and the periodic sampling interval are variable over time.

10. The method of claim 9 wherein both the power sample period and the periodic sampling interval are selected so as to increase exponentially over time.

11. The method of claim 9 wherein only the periodic sampling interval is selected so as to increase exponentially over time.

12. The method of claim 1 wherein the steps for detecting interference are performed over at least one of a wireless client and a wireless access point in a wireless local area network.

13. The method of claim 12 wherein the steps for detecting interference are performed on the wireless client and, If Interference is determined, this determination is forwarded to a wireless access point.

14. The method of claim 13 wherein the determination is forwarded to the wireless access point in real time.

15. The method of claim 13 wherein the determination is logged with a plurality of determinations from respective other power sample periods, and wherein these determinations are sent to the wireless access points in a batch.

16. The method of claim 12 wherein the steps of establishing, performing and determining are performed at the wireless client and wherein raw energy measurements are forwarded to a wireless access point, wherein the step of processing is performed at the wireless access point.

17. A circuit for detecting interference comprising:

state machine controller, for establishing an interference detection cycle including a power sample period and a periodic sampling interval;

a receiver component, responsive to the state machine controller, for performing an energy measurement at a predetermined wireless band during the power sample period;

a threshold comparator for determining whether the energy measurement exceeds a predetermined threshold;

a processing implementation for processing the energy measurement to determine whether it corresponds to interference on the predetermined wireless band, If the energy measurement exceeds the predetermined threshold;

the processing implementation including an analyzing implementation for analyzing the waveform characteristics of the enemy measurement to determine whether the waveform characteristics are compatible with desired signals, wherein the waveform characteristics are not compatible, the analyzing implementation determines the energy measurement corresponds to interference; and

a deactuating implementation instructing the state machine controller to await the next power sample period if the energy measurement does not exceed the predetermined threshold.

18. The circuit of claim 17 wherein the state machine controller is responsive to a clock signal that determines the periodic clock signal that determines the periodic sampling period such that the circuit shuts down between power sampling periods.

19. The circuit of claim 17 wherein the receiver component is configured to measure received signal strength at a 5 GHz wireless band.

20. The circuit of claim 17 wherein the processing implementation actuates a processing component and forwards the energy measurement to the processing component.

21. The circuit of claim 17 wherein the analyzing implementation comprises a Fast Fourier Transform waveform analyzer.

22. The circuit of claim 17 wherein the processing implementation comprises means for determining the direction to the source of the energy measurement.

23. The circuit of claim 17 wherein the power sample period and the periodic sampling interval are constant over time.

24. The circuit of claim 23 wherein the power sample period and the periodic sampling interval are selected to be relatively prime so as to detect an interference source having a known frequency.

25. The circuit of claim 17 wherein at least one of the power sample period and the periodic sampling interval are variable over time.

26. The circuit of claim 25 wherein both the power sample period and the periodic sampling Interval are selected so as to increase exponentially over time.

27. The circuit of claim 25 wherein only the periodic sampling Interval is selected so as to increase exponentially over time.

28. The circuit of claim 17 wherein the circuit is a component of at least one or a wireless client and a wireless access point in a local area network.

29. The circuit of claim 28 wherein the circuit is a component of a wireless client and wherein the processing implementation forwards an interference determination to a wireless access point.

30. The circuit of claim 29 wherein the processing implementation is configured to forward the interference determination to the wireless access point in real time.

31. The circuit of claim 29 wherein the processing implementation logs the interference determination in memory with a plurality of interference determinations from respective other power sample periods, wherein the processing implementation sends these interference determinations to the wireless access points in a batch.

32. The circuit of claim 28 wherein the circuit is a component of a wireless client which forwards raw energy measurements to a wireless access point which includes a further processing implementation for processing the energy measurement to determine whether it corresponds to interference on the wireless band.