Analysis of energy efficiency for packet-based transmission

In this paper, we propose a new definition of energy efficiency with respect to a given target packet error rate (PER). It is shown that some previous reported definitions are actually special cases of our definition. Consequently we use the definition to analyze the energy efficiency of Multilevel quadrature amplitude modulation (MQAM) and find that for a specific transmission there exists an energy efficient optimal initial PER which is independent of the traffic QoS. Then we derive the optimal PER and corresponding transmission power, and analyze the properties under various channel gain conditions. We believe that the result may help improve the energy efficiency of adaptive modulation. Finally, we consider the delay constraints and propose an optimization method based on PER to achieve extra energy efficiency gain while satisfying the delay requirements.