An Enhanced Polar-Domain Dictionary Design for Elevated BSs in Near-Field U-MIMO

TL;DR

This paper introduces a generalized grid design framework for near-field U-MIMO systems that accounts for arbitrary base station heights, improving channel estimation accuracy and spectral efficiency at sub-THz frequencies.

Contribution

It proposes a novel grid design method based on minimizing normalized mean squared error, addressing limitations of previous approaches that assumed ground-level base stations.

Findings

Enhanced channel estimation accuracy

Improved spectral efficiency

Effective at sub-THz frequencies

Abstract

Near-field U-MIMO communications require carefully optimized sampling grids in both angular and distance domains. However, most existing grid design methods neglect the influence of base station height, assuming instead that the base station is positioned at ground level - a simplification that rarely reflects real-world deployments. To overcome this limitation, we propose a generalized grid design framework that accommodates arbitrary base station locations. Unlike conventional correlation-based approaches, our method optimizes the grid based on the minimization of the optimal normalized mean squared error, leading to more accurate channel representation. We evaluate the performance of a hybrid U-MIMO system operating at sub-THz frequencies, considering the P-SOMP algorithm for channel estimation. Analytical and numerical results show that the proposed design enhances both channel estimation accuracy and spectral efficiency compared to existing alternatives.