Optimal power allocation in cognitive relay networks under different power constraints

In this paper, we study the optimal power control schemes for fading channels in cognitive relay networks under different power constraints of the primary user. Under the peak power and the average interference power constraints of the primary user, we derive the optimal power allocation strategies to maximize the ergodic achievable rate of the cognitive relay networks when the channel state information is available to both the cognitive transmitter and the receiver. Finally, the numerical results show the feasibility of our proposed power allocation schemes.