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.