Performance analysis of random beamforming for multiuser spectrum sharing networks

This study analyses a comprehensive performance of multiuser spectrum sharing networks using random beamforming (RBF). In the considered cognitive radio (CR) system, a secondary broadcast station (SBS) coexisting with a pair of primary transceivers broadcasts the information to multiple secondary users. The authors first consider that the CR-RBF system does not undergo interference from the primary network. In doing so, an exact expression is derived for the cumulative distribution function (CDF) of signal to interference plus noise ratio (SINR). Resorting to the derived CDF, the authors obtain an exact closed-form expression of outage probability. In addition, the closed-form expressions of the moment of SINR and other performance are provided, respectively, which provide an efficient method to evaluate key parameters on the considered system. Next, the authors also consider that the CR-RBF system undergoes interference from the primary network. Numerical simulations are presented to validate the correctness of the authors' analytical results. Unlike non-CR RBF system, increasing the number of antennas improves the performance achieved by CR-RBF systems when the maximum allowable power of SBS is less than a certain value. Otherwise, increasing the number of antennas decreases the performance achieved by CR-RBF systems.