Method, apparatus and computer program for sensing spectrum in a cognitive radio environment
First Claim
1. 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.
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Abstract
To find frequency slots over which a cognitive radio can send an opportunistic transmission, a wideband spectrum is searched with a lower resolution to identify bandwidth slices having low or no signal levels. The identified bandwidth slices are searched with a higher resolution and candidate frequency slices are selected as those bandwidth slices having the least signal levels after the higher resolution searching, and ranked from the lowest signal level to the highest. A spectrum detection algorithm is executed on the selected candidate frequency slices in the order of the rank until it is decided that one of them has sufficiently free spectrum. A transmission is then opportunistically sent on the decided candidate frequency slice. Ongoing to the searching, intermittent signals are detected and a band about them is searched with the lower resolution to determine if the band about the detected intermittent signal is an identified bandwidth slice. Various techniques are shown for how the fine search is conducted.
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Citations
27 Claims
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1. A method comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An apparatus comprising:
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a coarse power detector configured to search 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; a fine power detector configured to search the identified bandwidth slices with a second resolution that is higher than the first resolution and to select as candidate frequency slices those bandwidth slices having least signal levels after the second resolution searching; a spectrum detector configured to execute a spectrum detection algorithm on at least one of the selected candidate frequency slices; a processor configured to decide that the at least one of the selected candidate frequency slices has sufficiently free spectrum; and a transmitter configured to transmit in the decided candidate frequency slice; wherein the processor is configured to rank 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; and wherein the spectrum detector is configured to execute the spectrum detection algorithm on the ranked candidate frequency slices in the order of the priority until the processor decides that one of the candidate frequency slices has sufficiently free spectrum. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A computer readable memory embodying a program of machine-readable instructions executable by a digital data processor to perform actions directed toward searching spectrum for a frequency band available for transmission, the actions comprising:
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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; 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. - View Dependent Claims (21, 22, 23, 24, 25, 26)
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27. An apparatus comprising:
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a processor and a memory including computer program code, the computer program code being configured, with the processor, to cause the apparatus to perform at least the following; 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; 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; detecting spectrum on the ranked candidate frequency slices in the order of the priority until one of the candidate frequency slices has been identified as having sufficiently free spectrum; and transmitting in the identified candidate frequency slice.
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Specification