Joint power splitting and power allocation for two-way OFDM relay networks with SWIPT

This paper studies power-splitting relaying (PSR) in an orthogonal-frequency-division-multiplexing (OFDM) amplify-and-forward (AF) two-way relay network (TWRN) which implements simultaneous wireless information and power transfer (SWIPT), with the goal of maximizing information exchanging rates of two terminals in the network. To achieve this, we investigate the joint optimization of power-splitting (PS) ratio of the relay and power allocation over subcarriers. The formulated optimization problem not only bears a non-convex energy-harvesting constraint of the relay but also tightly couples the PS ratio and power allocation variables in the non-convex objective function. To tackle this challenging problem, we show that it can be transformed into a problem which fits well in the d.c.(difference of two convex functions) programming framework by two different approaches, and thus can be effectively solved by two constrained concave-convex procedure based algorithms, respectively. Simulation results show that the performance of the PSR-based OFDM AF TWRN employing our proposed schemes is not only better than that of the existing time-switching based relaying OFDM AF TWRN, but also superior over that of the PSR-based OFDM AF TWRN employing the simple scheme with fixed PS ratio.