Beamformer Structures for General MISO/MIMO Channels with Imperfect Feedback

Description

The channel capacity of multiple-input multiple-output (MIMO) wireless communications in Rayleigh fading with perfect channel state information (CSI) or with no CSI at the transmitter is well understood in the literature. In many practical situations, only imperfect CSI is available at the transmitter (CSIT) and it is important to optimize the signal covariance matrix to achieve the channel capacity. For independent information streams, the optimized transmitted signal covariance matrix essentially defines a beamforming network such that each parallel symbol is transmitted along a different direction with different power. The general optimization issue for a beamformer network remains unsolved in the literature except for some special channel environments. In this project, the researchers tackle this general issue by introducing appropriate transformation and incorporating the method of characteristic functions. The results are expected to be useful for the design of high-rate wireless communications systems.