Seleção de Relay em Sistemas Cooperativos Cognitivos com Múltiplos Usuários Primários

Abstract

The performance of cooperative cognitive systems in the presence of multiple receivers is investigated. Assuming a spectrum sharing environment, in which the secondary network is composed by one source, N amplify-and-forward relays, and one destination, a relay selection strategy is proposed with the aim to maximize the end-to-end signal-to-noise ratio and, at the same time, to satisfy the interference constraints imposed by the M primary receivers. After performing the relay selection, the secondary destination chooses the best path (direct link or relaying link) by employing a selection combining scheme. An approximate, closed-form expression for the outage probability is derived, from which an asymptotic analysis is carried out, revealing that the system diversity order equals to N + 1, and showing that it is not affected neither by the number of primary receivers nor by the interference threshold. Monte Carlo simulations are presented to corroborate the proposed analysis.