Performance Analysis of MRC Diversity for Spectrum Sharing Systems with Imperfect Channel Estimation

In this paper, we analyze the performance of maximum ratio combining (MRC) diversity in spectrum sharing systems with imperfect channel estimation. Considering the limited power and number of pilot symbols, we study the impact of imperfect channel estimation about the secondary transmission link on the performance of the spectrum sharing system. Specifically, the exact closed-form expressions for the outage probability and average symbol error rate (SER) of spectrum sharing systems are derived, and the impact of various key system parameters, such as interference temperature, number of antennas, and channel estimation error, is investigated. Moreover, simple asymptotic expressions for the outage probability and average SER at the high signal-to-noise-ratio regime are provided, based on which the diversity and coding gains achieved by the secondary system are characterized. The finding of this paper suggests that zero diversity gain is attained due to imperfect channel estimation whereas a full diversity can be achieved under the perfect channel estimation case.