Data rate and throughput analysis of cooperative cognitive radio under a collision model

We consider a cooperative cognitive radio system, where a secondary user may relay data for the primary user. Under the half-duplex assumption and packet collision model, the primary and secondary instantaneous data rates are derived, as a function of the power allocation factor by the secondary user to relay the primary user´s data. We study the optimal power allocation to maximize the secondary user´s instantaneous data rate and long-term throughput, without degrading the primary user´s spectrum utilization. Our numerical results suggest that these two performance criteria entail drastically different optimal behaviors by the secondary user. Furthermore, we observe that employing successive interference cancellation in relaying can significantly increase the instantaneous data rate, but after optimizing the power allocation factor, the simple decode-and-forward strategy almost always achieves the same throughput as the more complicated strategies.