Outage Analysis of Cognitive Relay Networks over Double Rayleigh Fading Channels

In this paper, the underlay cognitive relay network over double Rayleigh fading channels is investigated. For this network, we consider two cases: limited power case and unlimited power case. In the limited power case, the power of secondary user is constrained. On the other hand, the power of secondary user is not constrained in the unlimited power case. We derive the exact and approximate outage probabilities for two cases. It is shown that for limited power case, the approximate outage probability approaches the exact outage probability as the maximum tolerable interference level increases. Also, it is shown that for unlimited power case, the approximate outage probability is similar to the exact outage probability. Index terms — Cognitive radio network, relay, double Rayleigh fading, outage probability.