Outage analysis of spectrum sharing relay systems with multiple secondary destinations under primary user's interference

In this paper, we investigate the impact of multiuser diversity on the performance of secondary users (SUs) in dual-hop decode-and-forward (DF) spectrum sharing systems over Nakagami- m fading channels, taking into consideration the interference from primary users (PUs). In particular, we present a detailed performance comparison for two different opportunistic scheduling algorithms, i.e., the signal-to-noise ratio (SNR)-based scheduling algorithm and the signal-to-interference-plus-noise ratio (SINR)-based scheduling algorithm. For both scheduling algorithms, exact and asymptotic analytical expressions for the outage probability are derived. Our findings show that the SINR-based scheduling algorithm always outperforms the SNR-based scheduling algorithm. Nevertheless, when the number of destination is large, both scheduling algorithms attain almost the same outage performance, which suggests that, in such a scenario, the SNR-based scheduling algorithm is preferred because it requires less channel state information.