Optimal power control for secondary system based on spectrum sharing

In this paper, the optimal power control strategies under four different types of power constraints are derived via convex optimization to maximize the ergodic capacity of secondary system based on spectrum sharing while guaranteeing QoS of the primary system transmission. The interference from primary user to secondary system is simultaneously considered in the analysis process besides the interference from secondary user to primary system. It is shown that both the transmission power of primary user and different power constraint parameters affect the ergodic capacity of secondary system severely, furthermore, the proposed power control strategies outperform the existing schemes without considering the effects of the transmission power of primary user via the achievable capacities during the simulation results.