Handbook on Array Processing and Sensor Networks

CHAPTER 3

MIMO Radio Propagation

Tricia J. Willink

Communications Research Centre, Ottawa, Ontario, Canada

3.1 INTRODUCTION

With the proliferation of wireless devices and the continuing introduction of new, higher bandwidth services, there is a need for high-data-rate technologies that can achieve high spectral efficiency. Multiinput multioutput (MIMO) communications systems are a strong contender to satisfy this need in many propagating environments. MIMO systems use diversity in space and time (and are hence also called space–time systems) to achieve higher capacities, which translates into improved error rates, larger range, and/or higher throughputs than conventional systems. The diversity results from the scattering of signal energy from objects in the surrounding environment and is exploited by using multiple antenna elements at both the transmitter and receiver.

Channel capacity analysis with early, idealized MIMO channel models suggested that huge gains could be achieved—up to a linear increase with the number of antenna elements in the smaller of the two arrays. These idealized models assumed that the channel responses between each pair of transmitter/receiver antenna elements were independent: This follows from the assumptions that there is an infinite number of scatterers distributed around the antenna arrays and that the antenna elements are separated enough to make ...