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Energy-efficient power allocation for simultaneous wireless information-and-energy multicast in cognitive OFDM systems

In this paper, we investigate power allocation for simultaneous wireless information-and-energy multicast in cognitive OFDM systems. Our objective is to maximize the energy efficiency (EE) subject to the maximum power constraint at cognitive base station (CBS), maximum receiver interference constraint at each primary user (PU) and minimum harvested energy constraint at each energy receiver (ER). Due to the non-convexity of objective function, fractional programming is adopted to transform the nonconvex problem to a convex one. However, the complexity of the traditional optimization method, i.e., interior point method, is still too high to solve the transformed problem. To this end, a bisection-search-based suboptimal algorithm is proposed. Simulation results show that the proposed algorithm can greatly reduce the complexity (up to 1/12 at most) at the cost of tiny performance loss (less than 2%) compared with traditional convex optimization algorithms.