Performance of hybrid codebook techniques for MISO downlink channels with limited feedback

Multi-antenna downlink system with limited feedback can provide enormous capacity gains. In practical, two systems can be considered. One is zero-forcing beamforming (ZFBF), and the other is per user unitary rate control (PU
²
RC) which has been proposed for emerging cellular standards. In order to have good performance, ZFBF requires many feedback bits, and PU
²
RC requires many users. Recently, the authors proposed a hybrid multi-user MISO system which has merits of those two schemes simultaneously. In this paper, we analyze the sum-rate performance and quantization error of the hybrid scheme. The throughput scaling laws are also derived in high and medium SNR regimes.