Performance evaluation of multi-user diversity in a SIMO spectrum sharing system with reduced CSI load

This paper presents performance evaluation of multi-user diversity in an underlay spectrum sharing system, over Rayleigh fading channels, in which primary and secondary receivers employ multiple antennas. For the user selection, we first consider an optimal selection scheme which requires the full channel state information (CSI). In order to decrease the computational complexity of user selection and to reduce the CSI load, we then use a threshold-based user selection scheme. For each user selection, we present performance evaluations using the following metrics: the average channel capacity and the outage probability, where mathematical expressions are derived. The performances of the considered systems are evaluated and compared using the derived mathematical formulas in different cases. We show using numerical analysis and simulations that the threshold-based user selection scheme, despite its lower complexity, in some cases, achieves the same outage probability performance of the user selection employing full CSI in considered cognitive radio (CR) system. To show the accuracy and the correctness of the performed analysis, Monte-Carlo simulation results are also provided.