Design and Analysis of Two-Way Limited Feedback Beamforming Systems

Limited feedback beamforming is a simple technique to supply channel state information at the transmitter (CSIT) of a multiple-input-multiple-output (MIMO) system using beamforming. Feedback relies on the existence of a two-way communication system, which has two users conveying data to each other. As resources allocated to feedback and to transmitting data assist transmissions in two different directions, a fundamental tradeoff exists between the achievable rates in both directions. In this paper, we focus on beamforming systems with limited feedback where all transmissions, including feedback, use beamforming. We propose an anlytical framework to analyze such a system using simple effective SNR expressions. Closed- form results for the local tradeoff boundary for each user are found. Simulations illustrate system behavior for various configurations. The system becomes less coupled as available power on each side increases.