MULTIPLE‐INPUT MULTIPLE‐OUTPUT (MIMO) TECHNOLOGY

This chapter introduces the multiple-input multiple-output (MIMO) technologies. The goal is to prepare the reader for further study of the subject by explaining the most common MIMO schemes and providing a general theoretical framework. The chapter presents a naive idea of using multibeam transmission to increase system capacity. Such an idea introduces spatial multiplexing, one of the key MIMO concepts. The chapter also introduces the two most important concepts of MIMO (spatial multiplexing and space-time diversity) by describing two MIMO schemes (Bell Laboratories Layered Space-Time and Alamouti code). It also outlines the landscape of major theoretical topics in MIMO. The chapter discusses MIMO channel models, channel capacity, the theoretical framework of space-time diversity and space-time coding, links the concepts of spatial multiplexing and space-time diversity and presents a tradeoff bound. To build a MIMO system, the reader needs to investigate more, especially on the tradeoff of performance and complexity and on radio frequency issues.