ABSTRACT
This chapter describes the need to go for Multiple-input multiple-output (MIMO) systems and summarizes how the communication paradigm shifted from single antenna systems to MIMO systems. It presents the readers familiar with different channel models being used for the analysis of MIMO systems. The chapter discusses various variants of MIMO systems in two broad categories, as open loop MIMO systems and closed loop MIMO systems. It also discusses the paradigm shift from analog communication systems to digital communication systems and from single-input single-output systems to MIMO systems. The most commonly studied methods to overcome the effect of fading are the diversity combining schemes such as spatial diversity scheme, temporal diversity scheme, spectral diversity scheme, and polarization diversity scheme. Equal Gain Combining also takes advantage of different strengths at different locations. MIMO systems can be classified as open loop MIMO systems or closed loop MIMO systems based on the scheme used for transmission of information.
