On the Performance of Relay Selection in Cognitive Radio Networks

In this paper, we investigate several relaying schemes for cooperative communications in Cognitive Radio Networks (CRNs) in order to improve the performances of secondary transmissions while respecting a certain Quality of Service (QoS) requirement at the primary transmissions. We propose relaying schemes where a number of relay nodes, randomly located, may help either the primary or the secondary transmission. By defining proper relay selection criteria and power allocation schemes, we illustrate the secondary outage probability performance while guaranteeing the primary QoS. Using simulations, we present the impact of different parameters, such as the QoS requirement, the chosen relay selection criteria, the number of available relays, the positions of the relays, etc., on the secondary transmission performance. The obtained results show the potential of the proposed relaying schemes, and provide guidelines about the expected secondary performance under the impact of several parameters.