Adaptive Link Selection for Cognitive Buffer-Aided Relay Networks

In this paper, we consider a block fading underlay cognitive radio network where the primary network (PN) consists of a source and a destination, and the secondary network (SN) has three nodes, namely a source, a half-duplex decode-and-forward relay, and a destination. We propose a novel link selection protocol for the SN such that the throughput of the SN is maximized while the average or instantaneous interference to the primary destination is kept below a certain threshold. In particular, in the proposed protocol, the secondary relay (SR) decides optimally when to transmit data, receive data, and be silent. To this end, the SR is equipped with a buffer for the storage of information. In the proposed policy, the interference from the PN to the SN is also taken into account and canceled by an opportunistic interference cancelation scheme. Our simulation results show that for a given interference threshold, the proposed link selection protocol outperforms the existing relaying policies reported in the literature in terms of the secondary throughput.