Sum-Rate Distortion for a Multiantenna Broadcast Channel due to Limited Feedback

Realization of large capacity gains offered by multiple antenna systems depends upon the presence of channel state information (CSI) at the transmitter. However, very recently the overall impact of feedback on system capacity has been examined in order to highlight the hidden aspect of data rate loss due to feedback in general. In this paper, we extend the system model, called a duplex model that was introduced for a single-user point to point system, to a system for a multiple user scenario as seen in a typical downlink of cellular communications system. A distortion function based on prior results for the Gaussian vector broadcast channel and feedback sum-rate optimization design is subsequently presented. This system model is used to derive bounds on the amount of feedback that can be supported under various antenna, channel and signal-to-noise ratio scenarios. Simulation results are presented to show the impact of feedback on the sum-rate for multi-antenna wireless systems with multiple users.