Energy Efficient Precoder in Multi-User MIMO Systems With Imperfect Channel State Information

This letter is on the energy efficient precoder design in multi-user multiple-input multiple-output systems which is also robust with respect to the imperfect channel state information at the transmitters. In other words, we design the precoder matrix associated with each transmitter to maximize the general energy efficiency of the network. We investigate the problem in two conventional cases. The first case considers the statistical characterization for the channel estimation error that leads to a quadratically constrained quadratic program with a semi-closed-form solution. Then, we turn our attention to the case which considers only the uncertainty region for the channel estimation error; this case eventually results in a semi-definite program.

I. Introduction

Due to the increasing interest in green wireless networks, the energy efficiency (EE) criterion has attracted significant attention in both academia and industry [1]. In general, EE is defined as the ratio of the sum-rate to the total power consumption and is measured in bits/Hz/Joule. The fractional form of this utility function causes additional difficulty in the design procedure [1].¹

In this letter, rate means spectral efficiency, in line with the literature on this subject. Please refer to (5) for the definition of rate.

²

EE unit can also be expressed by bps/Hz/watt.