Channel Charting-assisted Non-orthogonal Pilot Allocation for Uplink XL-MIMO Transmission

TL;DR

This paper introduces a novel CC-assisted pilot scheduling method for XL-MIMO systems that reduces pilot overhead and improves channel orthogonality by leveraging near-field channel features and a polar-domain codebook.

Contribution

It develops a polar-domain codebook and a near-field CC-assisted pilot allocation algorithm to enhance channel estimation and reduce pilot overhead in XL-MIMO systems.

Findings

The NCC-PA algorithm significantly improves transmission performance.

The approach effectively reduces pilot overhead in near-field XL-MIMO.

Numerical results show marked performance gains over conventional methods.

Abstract

Extremely large-scale multiple-input multiple-output (XL-MIMO) is critical to future wireless networks. The substantial increase in the number of base station (BS) antennas introduces near-field propagation effects in the wireless channels, complicating channel parameter estimation and increasing pilot overhead. Channel charting (CC) has emerged as a potent unsupervised technique to effectively harness varying high-dimensional channel statistics to enable non-orthogonal pilot assignment and reduce pilot overhead. In this paper, we investigate near-field channel estimation with reduced pilot overhead by developing a CC-assisted pilot scheduling. To this end, we introduce a polar-domain codebook to capture the power distribution of near-field XL-MIMO channels. The CC-assisted approach uses such features as inputs to enable an effective low-dimensional mapping of the inherent correlation patterns in near-field user terminal (UT) channels. Building upon the mapped channel correlations, we further propose a near-field CC-assisted pilot allocation (NCC-PA) algorithm, which efficiently enhances channel orthogonality among pilot-reusing UTs. Numerical results confirm that the NCC-PA algorithm substantially elevates the wireless transmission performance, offering a marked improvement over the conventional far-field CC-PA approach.