Multiantenna communications in the presence of feedback

Multiantenna technology offers the advantages of increased data transmission rates and reliability for many existing and next-generation wireless systems. It has therefore become an important element in the design of communication schemes for wireless systems. Channel state information (CSI) at the transmitter end is often an essential requirement when one wishes to fully utilize the potential gain promised by multiantenna technology. This requirement has sparked enormous interest in the design of practical transmission schemes (most notably, the design of transmit beamforming) in the presence of a reverse feedback link that conveys partial CSI from the receiver to the transmitter. This work presents a comprehensive study of optimal transmission schemes in the general class of linear space-time codes when there is a partial CSI feedback link in the point-to-point multiple-input multiple-output (MIMO) system. The analysis provides insights into the optimality of the low-complexity transmit beamforming scheme in the presence of partial CSI feedback. The study of benefits of multiantenna technology is then extended to the design of distributed transmission algorithms in wireless sensor/relay networks. In such networks, a general framework is proposed for systematically analyzing the fundamental properties of distributed beamforming algorithms.