Quantization Bounds on Grassmann Manifolds of Arbitrary Dimensions and MIMO Communications with Feedback

TL;DR

This paper derives a general volume formula for small metric balls on Grassmann manifolds of any dimension, enabling precise bounds on quantization and feedback in MIMO systems with finite antennas.

Contribution

It provides the first closed-form volume formula for small balls in Grassmann manifolds of arbitrary dimensions, extending previous results and improving MIMO feedback analysis.

Findings

Derived a closed-form volume formula for small metric balls in Grassmann manifolds.

Established tight bounds on distortion-rate tradeoff for quantization.

Quantified MIMO system information rate with finite feedback for arbitrary antenna configurations.

Abstract

This paper considers the quantization problem on the Grassmann manifold with dimension n and p. The unique contribution is the derivation of a closed-form formula for the volume of a metric ball in the Grassmann manifold when the radius is sufficiently small. This volume formula holds for Grassmann manifolds with arbitrary dimension n and p, while previous results are only valid for either p=1 or a fixed p with asymptotically large n. Based on the volume formula, the Gilbert-Varshamov and Hamming bounds for sphere packings are obtained. Assuming a uniformly distributed source and a distortion metric based on the squared chordal distance, tight lower and upper bounds are established for the distortion rate tradeoff. Simulation results match the derived results. As an application of the derived quantization bounds, the information rate of a Multiple-Input Multiple-Output (MIMO) system with finite-rate channel-state feedback is accurately quantified for arbitrary finite number of antennas, while previous results are only valid for either Multiple-Input Single-Output (MISO) systems or those with asymptotically large number of transmit antennas but fixed number of receive antennas.