On the Performance of Opportunistic Relay Selection in Cognitive Radio Networks with Primary User’s Interference and Direct Channel

This paper analyzes outage performance of opportunistic relay selection in cognitive radio networks with primary user’s interference and direct channel over independent non-identically distributed fading channels and under maximum transmit power constraint and interference power constraint. Exact analysis is firstly proposed and then extended to asymptotic analysis to have insights into important performance metrics such as coding gain and diversity order. The proposed analysis can also be applied to corresponding analysis for opportunistic relay selection in cognitive radio networks with PU’s interference and without direct channel to highlight the usefulness of direct channel in relaying communications without any sacrifice of power and bandwidth. A multitude of results illustrate an achievable full diversity order, a considerable system performance deterioration due to primary user’s interference but this deterioration can be drastically remedied by increasing the number of involved relays, and the superiority of opportunistic relay selection with direct channel to that without it.