Cognitive DF generalized order relay selection networks with imperfect channel estimation and interference from primary user

Few papers in literature deal with interference in cognitive relay networks (CRNs) in both directions, i.e., interference from secondary user (SU) on the primary user (PU) and interference from PU on the SU. In this paper, we study the outage performance of cognitive decode-and-forward (DF) generalized order relay selection operating in secondary network with interference from PU transmitter on the SU receivers and assuming Rayleigh fading channels. Furthermore, we study the effect of imperfect channel estimation (ICE) on the system performance. Also, to get more insights about the system behavior, the performance is studied at the high signal-to-noise ratio (SNR) regime. Monte-Carlo simulations are given to validate the achieved results. Findings illustrate that with fixed interference power, the diversity order of the secondary system linearly increases with decreasing the order of the selected relay, and vice versa decreases. Also, the diversity order linearly decreases with decreasing the number of relays, and vice versa increases. Furthermore, results show that the interference from the PU transmitter at the SU relays is more severe on the system performance compared to the interference at the SU destination. Finally, when the interference at the SU relays or the SU destination or at both scales with SNR, the system achieves a zero diversity order due to the effect of interference on the system behavior.