Cognitive radio sensing method and system

In a cognitive radio system having a cognitive radio base station and a plurality of cognitive radio users operating in a cognitive radio coverage area overlapping a primary users' radio system coverage area, wherein the cognitive radio base station generates a low power wideband linear reference chirp signal extending over all channels and frequencies within the cognitive radio spectrum in the cognitive radio coverage area according to predetermined reference chirp signal parameters, a cognitive radio sensing method comprising the steps of:

• (a) receiving a signal in the cognitive radio spectrum in the cognitive radio coverage area at a cognitive radio user's receiver on a cognitive radio channel;
• (b) generating a local copy of a conjugate of the linear reference chirp signal in the cognitive radio user's receiver according to the predetermined reference chirp signal parameters;
• (c) cross-correlating the received signal with the local copy of the conjugate of the linear reference chirp signal in a matched filter in the cognitive radio user's receiver, the matched filter producing a cross-correlated chirp signal output;
• (d) estimating times of interference and noise from the primary users with a processor programmed to detect times at which the chirp cross-correlation output exceeds a predetermined envelope threshold level above an envelope of the cross-correlated chirp signal output;
• (e) transforming the cross-correlated chirp signal output from a time domain representation into a frequency domain representation;
• (f) determining frequencies of interference and noise from the primary users with the processor by detecting spectral components of the frequency domain representation of the cross-correlated chirp signal output exceeding the predetermined spectral threshold level above a flat top of the frequency domain representation of the cross-correlated chirp signal output;
• and
• (g) timing transmission and reception of the cognitive radio user's radio to avoid the interference frequencies determined in step (f) at the interference times determined in step (d).

A computer software product, comprising a medium readable by a processor, the medium having stored thereon a set of instructions for performing a cognitive radio sensing method, the set of instructions including:

• (a) a first sequence of instructions which, when executed by the processor, causes said processor to receive a low power reference chirp signal broadcast by a cognitive radio base station, the chirp signal being received in the presence of noise and interference from primary users of a predetermined multi-channel spectrum overlapping a spectrum of a cognitive radio system, the low power reference chirp signal having a bandwidth covering the entire spectrum of the cognitive radio system;
• (b) a second sequence of instructions which, when executed by the processor, causes said processor to correlate the chirp signal in the presence of noise and said interference from said primary users with a locally stored copy of the chirp signal, said correlating step providing a chirp correlation output;
• (c) a third sequence of instructions which, when executed by the processor, causes said processor to transform said chirp correlation output into a frequency domain;
• (d) a fourth sequence of instructions which, when executed by the processor, causes said processor to determine frequencies of interference and noise from said primary users by observing spectral components of said frequency domain transformed chirp correlation output which exceed a predetermined spectral threshold level above an expected flat top of said frequency domain transformed chirp correlation output;
• and
• (e) a fifth sequence of instructions which, when executed by the processor, causes said processor to tune said cognitive radio to transmission and reception frequencies that spectrally avoid the interference frequencies determined in step (d).