Exact Outage Analysis of Underlay Cooperative Cognitive Networks with Reactive Relay Selection Under Imperfect Channel Information

This paper investigates the effect of imperfect channel information on the outage performance of underlay cooperative cognitive networks with reactive relay selection under both primary outage constraint and maximum transmit power constraint. Towards this end, we firstly propose a power allocation scheme for secondary users to meet both constraints and take into account channel estimation error. Then, based on this scheme we propose an exact closed-form outage probability expression for secondary networks. This expression facilitates in quickly assessing the performance behaviour of underlay cooperative cognitive networks with reactive relay selection in different aspects and provides useful insights into the system performance. Various results show considerable system performance degradation due to imperfect channel information, a performance trade-off between the secondary network and the primary network, the performance saturation phenomenon in the secondary network, and the significant performance improvement with respect to the increase in the number of relays.