Appendix BIntroduction to MIMO and Massive MIMO
Research Fellow, NorthCap University, Haryana, India
B.1 Introduction
This topic briefly reviews the technology of multiple‐input multiple‐output (MIMO) in wireless communication. It also discusses the rationale behind why MIMO evolves into massive MIMO with the evolution of wireless technology.
MIMO is a multiple antenna technique used in wireless communication. Multiple antenna techniques are categorised as ‘diversity techniques’ and ‘spatial multiplexing techniques’. In the former technique, the same signal is received through multiple antennas at the receiver or transmitted through multiple antennas at the transmitter thereby increasing transmission reliability. Thus, multiple antennas can be used to provide diversity gain and increase the reliability of wireless links if both transmit and receive diversity are considered. In spatial multiplexing, multiple independent streams can be transmitted simultaneously thereby increasing transmission speed. In the spatial multiplexing technique, maximum achievable transmission speed can be same as the capacity of the MIMO channel, but in the case of the diversity technique the achievable transmission speed is much lower than the capacity of the MIMO channel. There are several different uses of multiple antennas in wireless communication. With channel state information at the transmitter, multiple transmit antennas provide channel gain with transmit beamforming. Herein, ...