Resource allocation for multicarrier secure communications in energy harvesting decode-and-forward relay network

In this paper, considering the decode-and-forward (DF) relay scheme, we study the optimal design of power allocation for orthogonal frequency division multiplexing (OFDM) secure communication, where the relay carries out wireless information and power transfer (WIPT) by time switching(TS) scheme. Our objective is to maximize the achievable secrecy rate subject to the power constraint of the source and the energy harvesting (EH) relay. However, the problems are non-convex. By exploiting their special structure, we equivalently transform the non-convex optimization problem into a quasi-convex problem and solve it by a simple algorithm using bisection. At each step of the algorithm, we will solve a convex feasibility problem by the Karush-Kuhn-Tucker (KKT) conditions and obtain the closed-form solution. At the end, simulation results verify that the proposed optimal solution outperforms that for conventional equal power solutions.