On the Outage Performance of Reactive Relay Selection in Cooperative Cognitive Networks Over Nakagami-m Fading Channels

This paper evaluates outage performance of reactive relay selection in cognitive radio networks over Nakagami-m fading channels under consideration of imperfect channel information on both interference and transmission channels, peak transmit power constraint, long-term power constraint, interference from primary users (PUs), and direct channel between secondary source and destination. Toward this end, power allocation for secondary transmitters is first proposed to satisfy both power constraints and account for imperfect Nakagami-m channel information and interference from PUs. Then, exact closed-form outage probability representation for secondary destination is suggested to promptly assess system performance and provide useful insights into performance limits. Various results show validity of the proposed expressions, substantial system performance degradation due to imperfect channel information and interference from PUs, error floor in secondary network, performance trade-off between secondary and primary networks, and considerable performance enhancement with respect to the increase in the number of secondary relays and larger fading severity parameter.