The Effect of Misdetection Probability on the Performance of Cooperative-Relaying-Based Cognitive Radio Systems

Cognitive radio (CR) is a promising solution to address the more and more congested radio spectrum. Cooperative relaying can provide a better transmission performance for the secondary user (SU), while the performance of the primary user (PU, also named licensed user) should be preferentially protected especially when there is misdetection probability. In this paper, in order to keep the PU away from outage caused by the interference from the SU under a certain signal-to-noise ratio (SNR), the maximum SNR for the SU can be derived by using the rate decaying factor (RDF). Then, based on the maximum channel gain and the maximum SNR, the outage probability is analyzed using decode-and-forward (DF) relaying and amplify-and-forward (AF) relaying schemes. Numerical results show that the outage probability decreases when the power allocation factor increases for DF strategy, while the outage probability has error floor when the power allocation factor increases for AF strategy. And the relaying scheme based on the maximum channel gain outperforms that based on the maximum SNR when the power allocation factor and detection probability are small, while the relaying scheme based on the maximum SNR outperforms that based on the maximum channel gain when the power allocation factor is large. What is more, AF relaying has better outage performance in the practical implementation.