TABLE OF CONTENTS In Chapter 5 we studied the fundamental limits/performance of MIMO systems, in the situation where the transmitter has no knowledge about the channel. In particular, we have seen that MISO or MIMO systems are capable of achieving full diversity gain, provided that the data is transmitted using codewords that span the space-time domain, jointly. Furthermore, we have observed that a MIMO system has the potential to increase capacity well beyond the value achievable with a SISO system, provided that the transmitter encodes the data properly. We have drawn these conclusions without referring to any specific transmission strategy. We had only anticipated that to achieve the promised benefits, it is necessary to adopt some kind of joint space-time coding. In this chapter, we describe and analyze alternative space-time coding strategies that allow us to achieve the full diversity gain and/or the maximum rate gain for systems having no information about the channel. We assume that the channels are flat-fading and the system is single-user. The extension to frequency-selective channels as well as to multiuser systems will be studied in Chapters 8 and 9.
The choice of the specific space-time encoder depends on which performance parameter we wish to improve, for a given set of constraints, such as transmit power and MIMO configuration. As performance parameter, we can use, for example, average error probability or information rate. One more important parameter, albeit not easy to be quantified, is the receiver complexity. Indeed, alternative space-time coding techniques should always be...
