Large scaled multi-user MIMO system so called massive MIMO systems for future wireless communication networks

The massive or large scaled multiple input multiple output (MIMO) systems have gained huge consideration due to high achievable data rates and connection reliability for future wireless networks. Multiple signal paths due to multiple antennas positioned at transmitter or receiver are responsible for large throughput. The eventual objective of using array of small antennas is that each single antenna will have small power consumption. The rapid increase in the number of wireless applications has put some limitations on conventional MIMO systems on channel capacity, energy and spectral efficiency. One of the possible solutions to overcome these limitations is to use large antenna arrays at the base stations or to some extent on the user equipments (UEs). The essential factors that must be considered before the deployment of massive MIMO systems include the broadcast models, channel estimation, placement ways with applications, uplink & downlink benefits and precoding procedures, expected achievable energy & spectral efficiencies, etc. In this article a comparison of massive MIMO is made with conventional MIMO. The authors discussed the massive MIMO system deployment scenarios, the best possible downlink precoding scheme for maximum achievable throughput, energy and spectral efficiency.