Energy-efficient two-way transmission in regenerative full-duplex relaying systems

In this paper, considering non-ideal power amplifier (PA) and circuit power, we optimize the energy efficiency (EE) of two-way full-duplex relaying (FDR) systems with decode-and-forward (DF) protocol. With higher cooperative gain, the direct link (DL) of the regenerative FDR is decoded at the receiver and can contribute to the useful signal rather than the interference, which can further improve the system performance significantly. With this mechanism, the joint transmit power and duration optimization problem is formulated to maximize the EE of the FDR system, which is proved to be non-convex and cannot be resolved by the standard convex methods. Therefore, a two step optimization algorithm (TSOA) is proposed to solve the original non-convex problem, where the optimality of the solution is ensured due to the rigorously proved convexity. Simulations are carried out to verify the EE performance of our proposed scheme, compared with the existing schemes. It is also revealed that the FDR systems are basically comparable to the half-duplex relaying (HDR) counterparts in terms of EE if the residual self-interference (RSI) is below a certain level, and have the ability to achieve higher data rate demand.