Tracking short-term maximum power spectrum density for improved visibility of low duty cycle signals

• US 20060270371A1
• Filed: 05/09/2006
• Published: 11/30/2006
• Est. Priority Date: 05/31/2005
• Status: Abandoned Application

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Sugar, Gary L.
• Application Number:
  US11/430,014
• Publication Number:
  US 20060270371A1
• Time in Patent Office: Days
• US Class Current: 455/226.100
• CPC Class Codes: H04B 17/26 using historical data, averaging values or statistics
• CPC Class Codes: H04B 17/327 Received signal code power [RSCP]

Abstract

A method is provided for analyzing activity in a frequency band that improves over conventional spectrum analyzers by providing the ability to visualize signals or energy with short duty cycles. During a time interval, a sequence of short-time power spectrum estimates is computed for energy received in said frequency band. Each short-time power spectrum estimate comprises data representing power of the received energy at each of a plurality of frequency bins that span a frequency sub-band at different time instants during the time interval. Data associated with the sequence of power spectrum estimates is accumulated. This process is repeated for each of a plurality of different sub-bands that span a frequency band of interest. As a result, activity can be observed in the frequency band of interest over relatively short time intervals, even if the activity has a short duty cycle.

Claims

1. A method for analyzing wireless activity in a frequency band, comprising:

a. during a time interval, computing a sequence of short-time power spectrum estimates for energy received in said frequency band, each short-time power spectrum estimate comprising data representing power of the received energy at each of a plurality of frequency bins that span a frequency sub-band at different time instants during said time interval; and

b. accumulating data associated with said sequence of power spectrum estimates.

2. The method of claim 1, wherein (a) computing comprises computing a sequence of a plurality of short-time frequency transforms for energy received in said frequency band, each short-time frequency transform spanning said frequency sub-band but taken at said different time instants to produce said short-time power spectrum estimate.

3. The method of claim 1, and further comprising, for each frequency bin associated with the short-time power spectrum estimates, storing a value representing the maximum power that has occurred in each frequency bin in said sequence.

4. The method of claim 1, and further comprising generating data for displaying a trace representing the power values for each frequency bin over time.

5. The method of claim 1, and further comprising performing (a) computing during each of a plurality of time intervals, wherein the sequence of short-time power spectrum estimates during a time interval spans the same frequency sub-band, but the frequency sub-band is different across the plurality of time intervals.

6. The method of claim 5, wherein (a) computing comprises computing the sequence of short-time power spectrum estimates during the plurality of time intervals across the plurality of frequency sub-bands which are substantially contiguous and span a frequency band of interest.

7. The method of claim 5, wherein (b) accumulating comprises accumulating data associated with each of the sequences of short-time power spectrum estimates during each of the plurality of time intervals.

8. The method of claim 7, and further comprising, for each time interval, storing a value representing the maximum power that has occurred in each frequency bin over the sequence of short-time power spectrum estimates during that time interval.

9. The method of claim 8, and further comprising generating data for displaying a trace representing the power values for each frequency bin over time.

10. The method of claim 1, wherein said (a) computing comprises computing a sequence of short-time Fourier transforms.

11. The method of claim 1, wherein said (a) computing further comprises discarding some of the short-time power spectrum estimates.

12. The method of claim 1, wherein said (a) computing comprises computing said sequence of short-time power spectrum estimates such that they at least partially overlap in time.

13. A device, comprising:

a. a radio receiver that receives wireless energy in a frequency band and produces a receive signal representative thereof;

b. an analog-to-digital converter coupled to the radio receiver that converts the receive signal to digital data;

c. a power spectrum computation circuit coupled to the analog-to-digital converter that computes short-time power spectrum estimates for energy received in said frequency band from the digital data; and

d. a control unit connected to said power spectrum computation circuit and to said radio receiver, wherein the control unit controls the power spectrum computation circuit to compute a sequence of short-time power spectrum estimates for energy received in said frequency band, each short-time power spectrum estimate comprising data representing power of the received energy at each of a plurality of frequency bins that span a frequency sub-band at different time instants during said time interval.

14. The device of claim 13, wherein said power spectrum computation circuit computes short-time frequency transforms for energy in said frequency sub-band of said frequency band, each short-time frequency transform spanning said frequency sub-band but taken at said different time instants to produce said short-time power spectrum estimate.

15. The device of claim 13, wherein said control unit stores, for each frequency bin associated with the short-time power spectra estimates, data representing the maximum power that has occurred in that frequency bin in said sequence.

16. The device of claim 13, wherein said control unit controls the power spectrum computation circuit to compute the sequence of short-time power spectrum estimates during each of a plurality of time intervals, wherein the sequence of short-time power spectrum data during a time interval spans the same frequency sub-band, but the frequency sub-band is different across the plurality of time intervals.

17. The device of claim 13, wherein said control unit controls the power spectrum computation circuit to compute the sequence of short-time power spectrum estimates during the plurality of time intervals across the plurality of frequency sub-bands which are substantially contiguous and span a frequency band of interest.

18. The device of claim 17, wherein said control unit stores data associated with each of the sequences of short-time power spectrum estimates during each of the plurality of time intervals.

19. The device of claim 18, wherein said control unit stores, for each time interval, data representing the maximum power that has occurred in each frequency bin over the sequence of short-time power spectrum estimates during that time interval.

20. The device of claim 13, wherein said power spectrum computation circuit computes short-time Fourier transforms to produce said short-time power spectrum estimates.

21. A processor readable medium storing instructions, that when executed by a processor, cause the processor to perform functions of:

a. during a time interval, computing a sequence of short-time power spectrum estimates for energy received in said frequency band, each short-time power spectrum estimate comprising data representing power of the received energy at each of a plurality of frequency bins that span a frequency sub-band at different time instants during said time interval; and

b. accumulating data associated with the sequence of power spectrum estimates.

22. The processor readable medium of claim 21, and further comprising instructions that, when executed by a processor, cause the processor to, for each frequency bin associated with the sequence of short-time power spectrum estimates, store a value representing the maximum power that has occurred in each frequency bin in said sequence.

23. The processor readable medium of claim 22, and further comprising instructions that, when executed by a processor, cause the processor to generate data for displaying a trace representing the values for each frequency bin over time.

24. The processor readable medium of claim 21, wherein said instructions for computing comprise instructions that cause the processor to compute the sequence of short-time power spectrum estimates during each of a plurality of time intervals, wherein the sequence of short-time power spectrum estimates during a time interval spans the same frequency sub-band, but the frequency sub-band is different across the plurality of time intervals.

25. The processor readable medium of claim 24, wherein said instructions for computing comprise instructions that cause the processor to compute the sequence of short-time power spectrum estimates during the plurality of time intervals across the plurality of frequency sub-bands which are substantially contiguous and span a frequency band of interest.

26. The processor readable medium of claim 25, and further comprising instructions, that when executed by the processor, cause the processor to store a value representing the maximum power that has occurred in each frequency bin over during each of the plurality of time intervals.

27. The processor readable medium of claim 26, and further comprising instructions, that when executed by the processor, cause the processor to generate data for displaying a trace over time representing the maximum power at each frequency bin.

28. The processor readable medium of claim 21, wherein said instructions for computing comprise instructions that cause the processor to compute a sequence of short-time Fourier transforms.

29. The processor readable medium of claim 21, wherein said instructions for computing comprise instructions that cause the processor to discard some of the short-time power spectrum estimates.

30. processor readable medium of claim 21, wherein said instructions for computing comprise instructions that cause the processor to compute the sequence of short-time power spectrum estimates such that they at least partially overlap in time.