METHODS FOR DETECTING AND CLASSIFYING SIGNALS TRANSMITTED OVER A RADIO FREQUENCY SPECTRUM

• US 20090047920A1
• Filed: 08/15/2007
• Published: 02/19/2009
• Est. Priority Date: 08/15/2007
• Status: Active Grant

• Current Assignee: Shared Spectrum Company
• Original Assignee: Shared Spectrum Company
• Inventors: LIVSICS, Eugene, Steadman, Karl, Dain, Dmitry, McHenry, Mark A., Ritterbush, Olga
• Granted Patent: US 8,055,204 B2
• Time in Patent Office: Days
• US Class Current: 455/226.100
• CPC Class Codes: H04B 1/719 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: H04B 17/391 Modelling the propagation channel
• CPC Class Codes: H04W 24/04 Arrangements for maintaining operational condition

Abstract

A method for classifying a signal is disclosed. The method can be used by a station or stations within a network to classify the signal as non-cooperative (NC) or a target signal. The method performs classification over channels within a frequency spectrum. The percentage of power above a first threshold is computed for a channel. Based on the percentage, a signal is classified as a narrowband signal. If the percentage indicates the absence of a narrowband signal, then a lower second threshold is applied to confirm the absence according to the percentage of power above the second threshold. The signal is classified as a narrowband signal or pre-classified as a wideband signal based on the percentage. Pre-classified wideband signals are classified as a wideband NC signal or target signal using spectrum masks.

Claims

1. A method for classifying a signal within a channel, the method comprising:

receiving a radio frequency signal at a signal classifier;

determining whether the signal is a narrowband signal by applying a first threshold and a second threshold, wherein the second threshold is lower than the first threshold;

determining whether the signal is a target signal by applying a mask to the channel to determine a degree of correlation between the mask and the target signal; and

if the signal is not determined to be a narrowband or target signal, classifying the signal as a wideband signal.

2. The method of claim 1, further comprising classifying the signal as no signal by applying a third threshold and a fourth threshold.

3. The method of claim 1, further comprising looping to another channel from the channel.

4. The method of claim 1, wherein the determining whether the signal is a target signal comprises determining a type of the target signal according to the mask.

5. The method of claim 1, wherein the determining the signal is a narrowband signal comprises applying a channel mask to the channel to determine the narrowband signal.

6. The method of claim 1, further comprising computing a power spectrum envelope within the channel.

31. The method of claim 4, wherein the target signal is determined to be a cooperative signal.

32. The method of claim 4, wherein the target signal is determined to be a cognitive radio signal.

33. The method of claim 4, wherein the target signal is determined to be a next generation (XG) radio signal.

7. A method for detecting a narrowband signal within a channel, the method comprising:

receiving a radio frequency signal at a signal classifier;

applying a first threshold to the received signal in a channel;

determining whether the signal is a narrowband signal according to the threshold;

applying a second threshold to the signal; and

confirming the signal is the narrowband signal according to the second threshold.

8. The method of claim 7, wherein the second threshold is lower than the first threshold.

9. The method of claim 7, further comprising applying a mask to a spectrum within the channel.

10. The method of claim 9, wherein the determining step includes determining a percentage of the spectrum occupied by the signal according to the mask.

11. The method of claim 7, further comprising classifying the signal as a wideband candidate signal if the signal is not the narrowband signal.

12. The method of claim 7, further comprising declaring the signal is the narrowband signal to a device.

13. The method of claim 7, further comprising not allowing an operation on a device because of the narrowband signal.

34. The method of claim 7, further comprising identifying the channel as unavailable for use by a cognitive radio based on the presence of the narrowband signal.

14. A method for detecting a wideband signal within a channel, the method comprising:

receiving a radio frequency signal at a signal classifier;

applying a first threshold to the received signal within the channel;

determining whether the signal is a wideband signal according to the first threshold; and

if the first threshold indicates the signal is not the wideband signal;

applying a second threshold to the signal; and

confirming the signal is not the wideband signal according to the second threshold.

15. The method of claim 14, further comprising applying a mask to the signal in the channel.

17. The method of claim 14, wherein the second threshold is lower than the first threshold.

18. The method of claim 14, further comprising determining the signal is not a narrowband signal.

19. The method of claim 14, further comprising classifying the signal as “

no signal”

according to the first threshold and the second threshold.

35. The method of claim 14, further comprising identifying the signal as a non-cooperative signal.

16. (canceled)

20. A method for detecting a target signal, the method comprising:

receiving a radio frequency signal at a signal classifier;

determining whether the received signal is a narrowband signal;

determining whether the signal is a wideband signal if the signal is not the narrowband signal;

applying a channel mask to the signal if the signal is not the narrowband signal or the wideband signal; and

determining whether the signal is a target signal, wherein the target signal correlates to the channel mask.

21. The method of claim 20, further comprising classifying the target signal according to the channel mask.

22. The method of claim 20, further comprising determining a degree of correlation between the channel mask and the signal.

23. The method of claim 20, further comprising looping through a plurality of channel masks to select the channel mask.

36. The method of claim 20, further comprising classifying the target signal as a cooperative signal.

37. The method of claim 20, further comprising classifying the target signal as a cognitive radio signal.

38. The method of claim 20, further comprising classifying the target signal as a next generation (XG) radio signal.

24. A method for detecting and classifying a denial of service (DoS) attacker, the method comprising:

storing statistical data for signals received by a target radio over a frequency range of interest;

detecting a potential DoS attacker by identifying a change in communication quality based on the statistical data; and

classifying the potential DoS attacker based on the statistical data.

25. The method of claim 24, further comprising classifying the DoS attacker as an active DoS attacker if large amounts of interference are present over large varying parts of spectrum.

26. The method of claim 24, further comprising classifying the DoS attacker as static DoS attacker if large amounts of interference are present over static parts of spectrum.

27. The method of claim 24, further comprising classifying the DoS attacker as reactive DoS attacker if a number of connection re-establishment attempts are present.

28. The method of claim 24, further comprising or periodically maintaining a database of spectrum history and statistics.

29. The method of claim 24, wherein the statistics comprise an indication of how often the target radio changes frequency of operation due to poor network operation, poor connectivity, or both.

30. The method of claim 24, further comprising monitoring frequencies previously used by the target radio to validate whether the introduced interference is an attempted DoS attack.