Multi-Access MIMO Systems with Finite Rate Channel State Feedback

TL;DR

This paper analyzes how finite rate channel state feedback impacts the sum rate in multi-access MIMO systems, proposing joint user selection and beamforming control methods with new mathematical tools to quantify performance loss.

Contribution

It introduces the composite Grassmann manifold and matrix to model and analyze the sum rate, providing a new approximation method for finite feedback effects.

Findings

Loss due to finite beamforming feedback decreases exponentially with more feedback bits

Proposes joint user selection and beamforming control for improved sum rate

Derives sum rate approximation using composite Grassmann manifold and matrix

Abstract

This paper characterizes the effect of finite rate channel state feedback on the sum rate of a multi-access multiple-input multiple-output (MIMO) system. We propose to control the users jointly, specifically, we first choose the users jointly and then select the corresponding beamforming vectors jointly. To quantify the sum rate, this paper introduces the composite Grassmann manifold and the composite Grassmann matrix. By characterizing the distortion rate function on the composite Grassmann manifold and calculating the logdet function of a random composite Grassmann matrix, a good sum rate approximation is derived. According to the distortion rate function on the composite Grassmann manifold, the loss due to finite beamforming decreases exponentially as the feedback bits on beamforming increases.