Performance Analysis of MRC Diversity for Cognitive Radio Systems

In this paper, we analyze the effect of maximum ratio combining (MRC) diversity on the performance of cognitive radio systems, in which the cognitive user (CU) shares the same spectrum with a primary user (PU) and the transmit power of the CU satisfies both the transmit and interference power constraints. Utilizing the derived cumulative distribution function (cdf) of the received signal-to-noise ratio (SNR), we investigate the ergodic capacity and the average symbol error rate (SER) of the considered system and derive new expressions for their asymptotic performance. Both analytical and simulation results show that the MRC diversity can provide full diversity order and a capacity-scaling law as a logarithmic function of the number of cognitive receive antennas when the transmit power of the CU is dominated by the transmit power constraint.