Method and apparatus for determining available bandwidth for wireless communication

1. A method of determining available bandwidth, comprising:

detecting, by a processor, energy in a next interval of bandwidth; and

determining, by the processor, if the next interval of a bandwidth is available if an interval of the bandwidth preceding the next interval was determined to be available such that the next interval is larger than the preceding interval, the determining determines whether the next interval is available based on the detected energy and a threshold.

2. The method of claim 1 , further comprising:

measuring noise energy in each channel of the bandwidth;

determining the threshold based on the measured noise energy associated with each channel in the next interval.

3. The method of claim 1 , wherein the determining comprises:

filtering a signal using an analog low-pass filter, the low-pass filter having the next interval as a pass-band; and wherein

the detecting detects energy output from the low-pass filter.

4. The method of claim 1 , wherein the determining comprises:

filtering a signal using a first analog low-pass filter, the first analog low-pass filter having a pass-band from a starting frequency to a first end frequency, the first end frequency being an end of the next interval;

filtering the signal using a second analog low-pass filter, the second analog low-Pass filter having a pass-band from the starting frequency to a second end frequency, the second end frequency being an end of the preceding interval;

detecting first energy in output from the first analog low-pass filter;

detecting second energy in output from the second analog low-pass filter; and

determining whether the next interval is available based on a difference between the first energy and the second energy.

5. The method of claim 1 , wherein the determining comprises:

filtering a signal using a first analog low-pass filter, the first analog low-pass filter having a pass-band from a starting frequency to a first end frequency, the first end frequency being an end of the next interval;

filtering the signal using a second analog low-pass filter, the second analog low-Pass filter having a pass-band from the starting frequency to a second end frequency, the second end frequency being an end of the preceding interval;

subtracting, in a time domain, output of the second analog low-pass filter from output of the first analog low-pass filter; and

detecting energy in output from the subtractor; and

determining whether the next interval is available based on the detected energy.

6. The method of claim 1 , wherein the next interval does not overlap the preceding interval.

7. The method of claim 1 , wherein the next interval is double a size of the preceding interval.

8. The method of claim 1 , further comprising:

identifying each channel in the next interval as available if the next interval is determined to be available.

9. The method of claim 1 , further comprising:

identifying at least one channel in the next interval as unavailable if the determining determines the next interval is not available.

10. The method of claim 9 , further comprising:

repeating the determining if a next interval of a bandwidth is available using a first available channel following an identified unavailable channel as the preceding interval.

11. A method of determining available bandwidth, comprising:

determining, by a processor, if a next interval of a bandwidth is available if an interval of the bandwidth preceding the next interval was determined to be available such that the next interval is larger than the preceding interval;

identifying, by the processor, at least one channel in the next interval as unavailable if the determining determines the next interval is not available;

reducing the next interval if the next interval is greater than one channel; and

determining if the reduced next interval is available.

12. The method of claim 11 , wherein the identifying comprises:

repeating the reducing and determining if the reduced next interval is available until one of (i) the reduced next interval is determined to be available, and (ii) the reducing the reduced next interval would reduce the reduced next interval to less than one channel.

13. The method of claim 12 , wherein the identifying comprises:

identifying the channel represented by the reduced next interval as unavailable if reducing the reduced next interval would reduce the reduced next interval to less than one channel.

14. The method of claim 13 , further comprising:

determining if a next channel succeeding the identified channel is available;

identifying the next channel as unavailable if the next channel is not determined to be available; and

repeating the determining if a next interval of a bandwidth is available using the next channel as the preceding interval if the next channel is determined to be available.

15. The method of claim 12 , wherein the identifying comprises:

determining whether a next channel succeeding the reduced interval is available if the reduced interval is determined to be available;

identifying the next channel as unavailable if the next channel is not determined to be available; and

repeating the determining whether a next channel is available and the identifying the next channel using the next channel as the preceding channel until an available channel is determined.

16. The method of claim 11 , wherein the reducing reduces only an end frequency of the next interval.

17. An apparatus for determining available bandwidth, comprising:

a tunable analog filter configured to selectively filter a received signal;

a detector configured to detect energy in output from the filter; and

a controller configured to determine if a next interval of a bandwidth is available if an interval of the bandwidth preceding the next interval was determined to be available such that the next interval is larger than the preceding interval, the controller configured to perform the determination based on output from the detector, and the controller configured to set the pass-band of the filter to the next interval.

18. The apparatus of claim 17 , further comprising:

a voltage controlled oscillator configured to generate a mixing signal;

a mixer configured to mix the mixing signal with a radio signal; and wherein

the filter is configured to receive output of the mixer as the received signal; and

the controller is configured to control the voltage controlled oscillator.

19. An apparatus for determining available bandwidth, comprising:

a plurality of filters, each configured to filter a received signal using a different pass-band;

a plurality of detectors, each detector associated with one of the plurality of filters and configured to detect energy in output from the associated filter; and

a controller configured to determine if a next interval of a bandwidth is available if an interval of the bandwidth preceding the next interval was determined to be available such that the next interval is larger than the preceding interval, the controller configured to perform the determination based on output from the plurality of detectors.

20. The apparatus of claim 19 , wherein

the plurality of detectors are further configured to,

filter a signal using a first analog low-pass filter, the first analog low-pass filter having a pass-band from a starting frequency to a first end frequency, the first end frequency being an end of the next interval, and

filter the signal using a second analog low-pass filter, the second analog low-pass filter having a pass-band from the starting frequency to a second end frequency, the second end frequency being an end of the preceding interval; and the controller is further configured to,

detect first energy in output from the first analog low-pass filter,

detect second energy in output from the second analog low-pass filter, and

determine whether the next interval is available based on a difference between the first energy and the second energy.

21. The apparatus of claim 19 , wherein

the plurality of detectors are further configured to,

filter a signal using a first analog low-pass filter, the first analog low-pass filter having a pass-band from a starting frequency to a first end frequency, the first end frequency being an end of the next interval, and

filter the signal using a second analog low-pass filter, the second analog low-pass filter having a pass-band from the starting frequency to a second end frequency, the second end frequency being an end of the preceding interval; and the controller is further configured to,

subtract, in a time domain, output of the second analog low-pass filter from output of the first analog low-pass filter,

detect energy in output from the subtractor, and

determine whether the next interval is available based on the detected energy.

22. The apparatus of claim 19 , wherein the next interval does not overlap the preceding interval.