Influence of Modulation Rate on Energy Efficiency for Relay-aided Transmission: Decode-and-forward Protocol
Rui Sun, Tao Wang, Fangfang Chen, Qinghua Huang · 2016
In this paper, we investigate the effect of modulation rate on the energy efficiency of a two-hop communication system with the assistance of a half-duplex decode-and-forward (DF) relay, considering the given bit error rate (BER) and using the M-QAM modulation.First, we formulate the optimum model of transmission power, subject to the given BER.Then the minimum transmission power under the constraint of the given BER is obtained.For energy efficiency problem, the circuit power consumption of devices can not be ignored, so with the circuit power consumption considered, we derive and analyze the expression of energy efficiency based on the modulation rate.According to convex optimization theory, energy efficiency is a quasi-concave function of modulation rate has been proved.We find that when the modulation rate increases, the energy efficiency will be first increases and then decreases.Finally, the theoretical analysis is corroborated by simulation results.Moreover, it is shown that the location of relay node has effect on system energy efficiency.