Towards 5G

15Massive MIMO Communications

Frederick W. Vook, Amitava Ghosh, and Timothy A. Thomas

Nokia Networks, Illinois, USA

15.1 Introduction

Over the last two decades, multiple input multiple output (MIMO) technology has been successfully deployed on a wide scale in cellular communication systems all over the world. MIMO technology involves the use of multiple antennas at one or both ends of a communication link to boost the performance and reliability through strategies, such as beamforming, diversity transmission, spatial multiplexing, and interference suppression. The currently-deployed 4G/LTE cellular standards (LTE Rel-8/9/10) support a comprehensive suite of MIMO techniques for up to eight antenna ports in a single sector on the downlink and up to four transmit antennas at a mobile station. An antenna port is defined as a logical entity distinguished by a separate reference signal sequence. Later LTE releases (Rel-11/12) enhance these MIMO techniques by coordinating the transmissions from multiple transmission points through the use of coordinated multipoint (CoMP) technology. Even with the comprehensive suite of MIMO techniques already defined for LTE, the limitation to a maximum of eight antenna ports provides an upper limit to the performance benefits of antenna array technology.

For 5G cellular communications, massive MIMO, sometimes called full dimension MIMO (FD-MIMO), is a promising technology for enhancing system performance. Massive MIMO involves the use of antenna ...