Impact of Primary-User Interference on Multiuser Cognitive Relaying Networks

Abstract

This paper investigates the impact of primary-user interference on the performance of a cognitive relaying network consisting of a source, an amplify-and-forward relay and multiple destinations. With the aim of exploiting multiuser diversity at the secondary network, two different destination-selection policies are considered, which are based on partial channel state information of the network, accounting for either the direct links or the relaying links. In the setup under investigation, the source's information signal is conveyed to the selected destination by both the direct link and the relaying link, after which a maximal-ratio combining of the signals coming from the source and relay is performed. In addition, we consider that the transmit power of the secondary nodes is constrained by key aspects of underlay spectrum sharing, i.e.,  the  interference temperature at the primary network and the maximum transmit power available at the source and relay. The system performance of the considered destination-selection schemes is analyzed in terms of the outage probability and compared to the optimal criterion. Monte Carlo simulations are provided to verify the attained analytical results.