Diversity analysis of single and multiple beamforming

Multi-antenna communication systems have the potential to play an important role in the design of the next generation broadband wireless communication systems. In this paper, we study a single-user multi-antenna system with perfect channel state information (CSI) both at the transmitter and the receiver. Beamforming is used to exploit the perfect channel knowledge at both ends. We show that beamforming achieves the maximum diversity in space when only the best eigenmode is used (i.e., single beamforming). We extend our analytical results to multiple beamforming (i.e., sending more than one symbol simultaneously). Our main contribution is the analysis of the maximum achievable diversity order of beamforming systems.