Energy-Efficient Power Allocation in Energy Harvesting Two-Way AF Relay Systems

In this paper, we focus on the issue of energy efficiency (EE) optimization of amplify-and-forward-based energy harvesting two-way relaying systems. Utilizing the statistical channel state information, we first build a statistical EE model, which is applicable to practical environments under fast fading channels. Then, a power allocation problem is formulated to maximize the EE under the constraints of total power and sum rate. Particularly, we have taken the asymmetric traffic requirements into account in our design, considering that the two sources may have different data rates. With the help of nonlinear fractional programming and Karush-Kuhn-Tuchker conditions, closed-form solution is achieved, thus providing valuable guidelines into practical system designs. For wider applications, we have shown that our results can be extended to multi-relay multi-user scenarios. Simulation results highlight the effect of our analytical results.