Rate Optimization for Energy Efficient System with M-QAM

In this paper, we have considered the optimization of the data rate in the case of point-to-point transmission with M-ary quadrature amplitude modulation (M-QAM). The main goal is to minimize the bit energy consumption under an average bit error rate (BER) constraint in additive white gaussian noise (AWGN) and Rayleigh channel. With the evolution of wireless communication towards shorter transmission distances, the circuit energy in system hardware becomes significant in the computation of the energy expenditure as well as the transmission energy. We use an accurate power model for the circuit energy consumption. The total energy consumption is then formulated as a function of the constellation size, distance, bandwidth and other channel parameters. Optimal data rate is obtained in closed form expression and the effect of bandwidth, distance and channel path loss is studied.