Improvement in Spectrum Sensing by Locally Optimal Detection Technique in Cognitive Radio

Spectrum sensing is one of the enabling functionalities for cognitive radio systems to operate in the spectrum white space. To protect the primary incumbent users from interference, the cognitive radio is required to detect incumbent signals at very low Signal-to-Noise Ratio (SNR). In this paper a study of Locally Optimal (LO) detection technique for spectrum sensing based on logarithmic - Likelihood Ratio Test (LLR) is given. LLR is a decision making technique used at the receiver system to decide the presence of the signal in the surrounding. The basic strategy is to correlate the received signal with the a priori known spectral features of the primary signal. This LO detection technique utilises the Likelihood Ratio Test (LRT) at very low SNR, but with less computational complexity.