TABLE OF CONTENTS Given the attractive capabilities of space-time coding to increase the information rate, for a given bandwidth, or reduce the transmission power to guarantee a required BER, it is not surprising that STC is an appealing candidate for applications in third generation cellular systems as well as for broadband wireless LANs. In both cases, the incorporation of space-time coding techniques has to face compatibility with currently standardized systems or systems under standardization. Clearly, the simpler is the compatibility with current systems, the most likely is the possibility of including space-time coding techniques. From this perspective, the first basic step to making space-time coding an appealing candidate is its extension to frequency-selective channels and multiuser systems. As mentioned in Chapter 3, the current standardization for broadband wireless LAN, see IEEE 802.11a for example, tends to use OFDM as a powerful tool to counteract channel frequency selectivity and still allow for simple receiving structures. For these reasons, this chapter is devoted to the generalization of space-time coding to frequency-selective systems. We will pay special attention to the application of space-time coding to block transmission systems using cyclic prefixes, as a way to have the benefits of space-time coding, with affordable complexity at the receiver side. The multiuser case will be then specifically analyzed in Chapter 9.
As already observed in Chapter 7, the choice of the space-time encoder depends on the performance parameter that is considered to be the most important to optimize, for the application at hand (i.e., diversity gain,...
