Determining the energy efficiency of femtocell base stations with multiple antennas

Multiple antenna techniques such as MIMO are key to achieving promised high data rates in 4G LTE and LTE-A systems. In addition they can be used to reduce total transmit power by use of beamforming or diversity schemes. This paper investigates their role and use in maximizing the energy efficiency of femtocell base stations and presents a range of considerations that must be made in order to achieve their full potential. Suitable expressions for total consumed power, when using multiple antennas, are provided. Used with power consumption models, a predicted energy saving of 15% for an LTE femtocell employing 2 Tx, 1 Rx transmit diversity is shown. Extending the analysis shows there is a diminishing return on energy savings as the number of antenna elements increases.