New energy efficiency metric with imperfect channel considerations for OFDMA systems

Considering recent important efforts on green radio technologies this letter deliberates on imperfect channel realisations to propose a new effective-energy-efficiency metric for downlink transmissions in multi-user, multi-carrier orthogonal frequency division multiple access (OFDMA) systems. To comply with the traditional energy efficiency formula under the assumption of perfect channel knowledge available, this new metric is designed on the fractional relation between the effective throughput and the total power consumed at the transmitter. Mathematical proofs are presented to confirm such compliance in terms of the impact of the channel coefficients on the energy efficiency performance. In order to prove the property, the letter also presents a profound insight on the monotonicity of the noncentralised chi-squared distribution