Algorithm for re-use of shadowed CRs as relays for improving cooperative sensing performance

In cooperative spectrum sensing, information from deeply faded local cognitive radios (CRs) needs to be eliminated from contributing to the fusion pool at the fusion center. Most current works on the subject unrealistically assume that the reporting channels between the CRs and the fusion center are free of loss and fading. In order not to waste those deeply faded CRs, this paper proposes an efficient algorithm to re-use them by reassigning them to act as cooperative diversity relays to assist the surviving CRs in combatting outages due to Suzuki fading in the reporting channel. The algorithm involves the pairing of a surviving CR to a relay CR so as to select the lowest outage probability of the resulting cooperative diversity relaying network. The paper proposes a closed-form and accurate approximation for the outage probability of such a network in the composite Rayleigh-lognormal fading channel, thus rendering fast and simple execution of the pairing algorithm.