Best relay selection with interference power constraint in cognitive relay networks

In this paper, we consider a cognitive radio network where secondary (unlicensed) users can share the spectrum with the primary (licensed) user, under the interference power constraint. We assume that the primary user and all secondary users have a constant-rate, constant-power transmission, our purpose is to select a group of secondary relays which can maximize the throughput of the cognitive relay network, meanwhile ensuring the QoS of the primary user. We studied the performance of the best relay via computer simulation. The simulation results show that the proposed best relay selection scheme can significantly improve the system throughput compared to the random selection scheme. Furthermore, we find that increasing the number of available relays improves the overall system performance which is mainly because of the diversity order obtained via adding more relays.