Sum Rate Maximization for Multi-Carrier SWIPT Relay System With Non-Ideal Power Amplifier and Circuit Power Consumption

In this paper, we investigate the resource optimization algorithm design in a multicarrier relay system with simultaneous wireless information and power transfer (SWIPT). The relay is capable of harvesting energy from the source's signals by using the power splitting method. The non-ideal energy consumption including both the non-ideal power amplifier and non-ideal circuit power consumption is considered. First, we study the transmission rate maximization problem (TRMP) in an asymmetric decodeand-forward (DF) relay transmission, where the transmission power at the source, the transmission power at the relay, the power splitting ratio, and the transmission time are jointly optimized. The formulated problem is a non-convex problem, and it is generally quite difficult to solve it. By exploiting the structure of the problem, we propose two methods (logarithmic operation on constraints and logarithmic change of variables) to transform it into the corresponding difference of convex (DC) optimization problems. Then, we extend the TRMP to an amplify-and-forward (AF) relay transmission. Furthermore, we propose an effective algorithm to solve the DC optimization problem and prove that the algorithm can converge to a stationary point. Finally, extensive simulations are conducted to verify the performance of the proposed algorithm. The simulation results show that the asymmetric DF relay transmission achieves the highest sum rate and the AF relay transmission achieves a much lower sum rate than both the asymmetric and symmetric DF relay transmissions under different conditions.