Fundamentals of MIMO Wireless Communications

In this chapter, we will give introduction to MIMO (pronounced “My-Moe”, J. G. Andrews et al., 2007) systems. First we will summarize some of the background in wireless communications which are required for better understanding of MIMO systems. We will start with three diversity, viz. frequency, time and space diversity to combat detrimental effects of wireless fading channels. Then we will discuss about the fading channel characteristics. We will define two important terms, viz. coherence bandwidth and coherence time. Then we will define what are frequency-flat and selective fading and slow and fast fading. Then we will discuss about multi-antenna systems like Multiple-Input Multiple-Output (MIMO), Multiple-Input Single-Output (MISO) and Single-Input Multiple-Output (SIMO) systems. In SIMO systems, we will briefly discuss about the receiver diversity techniques like Equal-Gain Combining (EGC), Selection Combining (SC) and Maximal Ratio Combining (MRC). In MIMO transmit diversity schemes we will define Open Loop, Close Loop and Blind MIMO systems. MIMO systems have rate and diversity gain over Single-Input Single-Output (SISO) systems. We will define rate and diversity gain and discuss concisely about the diversity multiplexing trade-offs. Finally we will mention some of the applications of MIMO systems.