Patent ID: 8718559

Claim:
A method comprising: searching a wideband spectrum with a first resolution to identify at least those bandwidth slices having low or no signal levels relative to other bandwidth slices of the wideband spectrum, in which the signal level per bandwidth slice according to the first resolution comprises a sum of signals detected in the bandwidth slice and weighted by signal strength; searching the identified bandwidth slices with a second resolution that is higher than the first resolution and selecting as candidate frequency slices those bandwidth slices having least signal levels after the second resolution searching; executing a spectrum detection algorithm on at least one of the selected candidate frequency slices and deciding that it has sufficiently free spectrum; transmitting in the decided candidate frequency slice; and after searching the identified bandwidth slices with the second resolution, ranking the candidate frequency slices in priority from a first bandwidth slice of the candidate frequency slices having a lowest signal level within the first bandwidth slice, to a second bandwidth slice of the candidate frequency slices having a highest signal level within the second bandwidth slice; wherein executing the spectrum detection algorithm is performed on the ranked candidate frequency slices in the order of the priority until it is decided that one of the candidate frequency slices has sufficiently free spectrum.