Spectrum sensing in low SNR: Diversity combining and cooperative communications

In this paper, the detection performance of an energy detector used for cooperative spectrum sensing in cognitive radio networks is investigated under very low signal-to-noise ratio (SNR) levels. The analysis focuses on the derivation of closed-form expressions for the false-alarm and the average missed-detection probabilities for two cases over different fading channels: (i) with diversity combining; and (ii) with cooperative communications. The detection threshold is optimized by minimizing the total error rate. The analysis is validated by numerical and semi-analytical Monte-Carlo simulation results, which focus on the sensing requirements defined in IEEE 802.22.