Energy efficiency analysis of practical two-way relay system with decode-and-forward protocol

In this paper, we consider the Energy Efficiency (EE) of a two-way decode-and-forward relay system with three nodes. For comparison, we also take the direct transmission system into account. The system EE is maximized by jointly optimizing the transmission power and the duration of each working state in case of two typical kinds of non-ideal Power Amplifier (PA) model, Traditional PA (TPA) and Envelope Tracking PA (ETPA) models. Theoretical analysis and simulation results show that the joint optimization of both parameters achieves better EE than the equal allocation of time with a marginal optimization of transmit power. In addition, the use of non-ideal PA models and the increase of downlink to uplink data rate ratio decrease the system EE. ETPA achieves much higher EE than TPA in variable optimization schemes. Finally, TWRT can achieve better EE and SE than DT in case of non-ideal PA model from the comparison.