Capacity Gains of Multiple-Antenna (MIMO) Systems in Wireless Communication

Abstract

The demand for higher data rates over wireless links continually outpaces the radio spectrum available to carry them, and multiple-antenna systems, which use several antennas at both the transmitter and the receiver, offer a way to raise the rate without more spectrum or power by sending several streams of data at once over the same channel. This study examines the capacity gains of multiple-antenna, or MIMO, systems in wireless communication, by how the channel capacity grows with the number of antennas. The capacity, the maximum rate at which information can be carried reliably, was determined as a function of the signal-to-noise ratio for a single-antenna link and for multiple-antenna configurations with increasing numbers of antennas, and the growth of capacity with the number of antennas was assessed. The single-antenna link's capacity grew only slowly with the signal-to-noise ratio, rising by a fixed amount for each doubling of the ratio, whereas the multiple-antenna configurations achieved far higher capacity, and crucially their capacity grew in proportion to the number of antennas, the configuration with more antennas carrying proportionally more, because the several antennas allow several independent streams of data to be sent simultaneously over the same channel and separated at the receiver. This multiplexing of streams lets a multiple-antenna system multiply its data rate without additional spectrum or transmit power, which is why the technology has become central to modern wireless systems, although realising the gains requires a suitably rich propagation environment and added processing. The study shows that multiple-antenna systems offer large capacity gains that scale with the number of antennas, and it discusses the conditions and costs on which the gains depend. KEYWORDS: MIMO, Multiple antennas, Channel capacity, Spatialmultiplexing, Wireless communication, Spectral efficiency, Antennaconfiguration, Diversity, Signal-to-noise ratio