Nearly Doubling the Throughput of Multiuser MIMO Systems Using Codebook Tailored Limited Feedback Protocol

TL;DR

This paper introduces Rate Approximation (RA), a robust feedback strategy for multiuser MIMO systems that improves throughput by focusing on rate approximation rather than channel approximation, with proven performance gains in LTE simulations.

Contribution

The paper proposes a novel RA scheme that separates transmit and feedback codebooks, optimizing rate delivery under limited feedback and demonstrating significant throughput improvements.

Findings

Performance gains of up to 70% over zero-forcing in LTE simulations.

RA scheme outperforms classical methods below certain interference thresholds.

Developed a feedback protocol considering transmit codebook complexity.

Abstract

We present and analyze a new robust feedback and transmit strategy for multiuser MIMO downlink communication systems, termed Rate Approximation (RA). RA combines the flexibility and robustness needed for reliable communications with the user terminal under a limited feedback constraint. It responds to two important observations. First, it is not so significant to approximate the channel but rather the rate, such that the optimal scheduling decision can be mimicked at the base station. Second, a fixed transmit codebook at the transmitter is often better when therefore the channel state information is more accurate. In the RA scheme the transmit and feedback codebook are separated and user rates are delivered to the base station subject to a controlled uniform error. The scheme is analyzed and proved to have better performance below a certain interference plus noise margin and better behavior than the classical Jindal formula. LTE system simulations sustain the analytic results showing performance gains of up to 50% or 70% compared to zeroforcing when using multiple antennas at the base station and multiple antennas or a single antenna at the terminals, respectively. A new feedback protocol is developed which inherently considers the transmit codebook and which is able to deal with the complexity issue at the terminal.