Effect of primary power fluctuation on ergodic capacity of a secondary user in a spectrum sharing environment

This paper investigates the effect of the transmit power fluctuation of the primary user on the ergodic capacity of the secondary user in a spectrum sharing environment. Considering an average received-power constraint at the primary user receiver, we derive the closed-form expression for the ergodic capacity of the secondary user and the average received-power assuming Rayleigh fading channels. Numerical results show that the transmit power fluctuation can enhance the ergodic capacity of the secondary user if the secondary user properly control its transmit power so as to fully exploit the transmit power fluctuation.