Date Added: Nov 2012
Cooperative relay technology was recently introduced into cognitive radio networks in order to enhance network capacity, scalability, and reliability of end-to-end communication. In this paper, the authors investigate an underlay cognitive network where the quality of service of the secondary link is maintained by triggering an opportunistic regenerative relaying once it falls under an unacceptable level. They first provide the exact Cumulative Density Function (CDF) of Received Signal-to-Noise (SNR) over each hop with co-located relays. Then, the CDFs are used to determine very accurate closed-form expression for the outage probability for a transmission rate R. They validate their analysis by showing that simulation results coincide with their analytical results in Rayleigh fading channels.