Cognitive cooperative networks with cluster-based relaying under interference constraints

In this paper, we consider the outage performance of a cognitive cooperative radio network (CCRN) in which the secondary base station (SBS) transmits signals to multiple secondary receivers (SU-Rx) through the help of multiple secondary relays (SRs). It is assumed that the SRs are geographically distributed in clusters and that the considered network operates in a Rayleigh environment. In addition, we assume that the transmit powers of the SBS and SRs are subject to peak interference power constraints of the primary users (PUs) in their respective coverage range. Specifically, a closed-form expression for the outage probability of the SU-Rx with the worst channel condition is derived for independently distributed Rayleigh fading. The obtained outage expression is further utilized to examine the impact of the channel mean powers, the number of SRs distributed in each cluster and the number of clusters on the system performance.