Multichannel TransmissionTransmit Diversity and SpaceTime Coding

In this chapter, we first introduce the notion of transmit diversity, which shifts the complexity associated with the implementation of a diversity receiver to the transmitter with the hope of accomplishing the same purpose, specifically, providing diversity gain, with as little compromise as possible in average SNR performance. In the simplest of terms, we transmit the same signal information (over a multitude of symbol intervals and not necessarily in the same sequence) simultaneously from a multitude of antennas and appropriately combine the faded versions of these transmissions received in the multitude of symbol intervals in such a way as to provide a diversity gain.