WLC26-2: Limited Feedback in Multiple Antenna Broadcast Channels

In this paper, we consider limited feedback for multiple antenna broadcast channels: each user quantizes its channel vector according to a rotated codebook which is optimal in the sense of mean square error and feeds back the codeword index. The paper is focused on characterizing the sum rate performance of zero-forcing dirty paper coding (ZFDPC) systems under limited feedback. We derive sum rate upper bound for systems employing Gaussian random codebooks and minimum distance decoding and link the throughput performance to some basic properties of the quantization codebook. Interestingly, we find that limited feedback employing a fixed codebook leads to a sum rate ceiling for asymptotically high SNR.