Space-time transmit strategies and channel feedback generation for wireless fading channels

The performance of future cellular and personal communications is expected to be limited by the "down-link" from the base station to the mobile. In this context, using sophisticated processing at the base station transmitter represents a promising method for enhancing the downlink capacity. Specifically, we consider space-time transmit processing, which exploits antenna arrays at the base station. Two extreme strategies for achieving this are space-time codes, which provide transmit diversity for combating Rayleigh fading without requiring knowledge of the space-time channel to the receiver, and transmit beamforming, which uses feedback regarding the space-time channel to increase the effective channel gain to the user of interest. We review some results regarding both space-time codes and transmit beamforming, including information-theoretic insights that show that transmit beamforming offers significant performance gains even with imperfect channel feedback. We then present the main result of the paper, which is a novel method for generating space-time channel feedback.