On the Throughput of Zero-Forcing Beamforming Using Random Vector Quantization Limited Feedback in MIMO Broadcast Channels

In wireless broadcast (downlink) channels, multiple transmit antennas can provide tremendous throughput (i.e., multiplexing) gain, even if each accessed user has only one receive antenna. Recent work has shown that zero-forcing beamforming (ZF-BF) based on random vector quantization (RVQ) limited feedback is a simple and effective transmission technique for broadcast systems. This paper analyzes the long-term average throughput of such systems. We model the throughput of each user as the difference of that between the two "virtual" single user multiple-input single-output (MISO) systems, and the total throughput as that of any user scaled by the number of accessed users. Based on this model, a semi-closed form expression of the system throughput is derived. The near-exact match of the expression is verified by the numerical results and simulations.