Relay assisted spectrum sensing in cognitive radio

We consider a cooperative spectrum sensing problem in which a relay user (RU) assists a secondary user (SU) in order to detect the presence of a primary user (PU). We propose three different schemes, namely amplify-and-forward, compress-and-forward, and decode-and-forward, where the RU transmits an amplified, compressed or decoded version of the observed signal toward the SU, respectively. We investigate the Neyman - Pearson criterion for each scheme. The theoretical performance of the tests is then analyzed in terms of probability of false alarm and mis-detection and closed-form expressions are derived for Rayleigh fading channels. Simulation results illustrate significant cooperative gain achieved by the proposed strategies. Numerical results are provided that give insights into the trade-offs between the primary and RU´s transmit power and the performance of the proposed protocols in this three node network.