Precoding design

Armed with the theoretical limits of MIMO wireless performance from Chapter 2, we now embark on the design of specific system blocks. At the transmitter, two major MIMO processing components at the symbol level are precoding and spacetime coding. Precoding, the last digital processing block at the transmitter (see Figure 1.2), is a technique that exploits the channel information available at the transmitter. Such information is generally referred to as transmit channel side information, or CSIT (this definition is more general than that in Chapter 2). In MIMO wireless, spatial CSIT is particularly useful in enhancing system performance. Space-time coding, on the other hand, assumes no CSIT and focuses on enhancing reliability through diversity. In addition to these two components, regular channel coding is required for bit-level protection. This chapter focuses on precoding design, and space-time coding is discussed in Chapter 4.