Energy Efficiency Analysis in Amplify-and-Forward and Decode-and-Forward Cooperative Networks

TL;DR

This paper evaluates the energy efficiency of cooperative relay networks using AF and DF modes, optimizing modulation schemes to reduce energy consumption while considering practical factors like circuit and retransmission energies.

Contribution

It introduces an energy efficiency analysis framework for cooperative networks that accounts for modulation optimization and practical energy components under Rayleigh fading.

Findings

Large constellations are optimal at short distances.

Constellation size decreases with increasing distance.

Cooperative gain varies with transmission distance.

Abstract

In this paper, we have studied the energy efficiency of cooperative networks operating in either the fixed Amplifyand- Forward (AF) or the selective Decode-and-Forward (DF) mode. We consider the optimization of the M-ary quadrature amplitude modulation (MQAM) constellation size to minimize the bit energy consumption under given bit error rate (BER) constraints. In the computation of the energy expenditure, the circuit, transmission, and retransmission energies are taken into account. The link reliabilities and retransmission probabilities are determined through the outage probabilities under the Rayleigh fading assumption. Several interesting observations with practical implications are made. It is seen that while large constellations are preferred at small transmission distances, constellation size should be decreased as the distance increases; the cooperative gain is computed to compare direct transmission and cooperative transmission.