Ergodic capacity analysis of fading SIMO channel in spectrum sharing environment

In this paper, we consider the spectrum sharing cognitive radio system, wherein single-input multiple-output ergodic fading channel is assumed. Subject to the average interference constraint of primary user, the ergodic capacity of cognitive user involving joint beamforming and power control is analyzed. We derive the expressions of ergodic capacity under different channel fadings including Raleigh fading, Nakagami-m fading and Lognormal shadowing fading. Most of the expressions are presented in closed-form or with some special integral function. Large amount of numerical simulations show that larger number of antenna and more severe channel fading can provide some gain in ergodic capacity of cognitive radio.