# Multiple-Cumulant-Matrices-Based Method for Exact NF Polarization Localization with COLD Array

## TL;DR

This paper introduces a new method for accurately locating near-field signals using a special antenna array, improving performance in 5G communication systems.

## Contribution

A novel multiple-cumulant-matrices-based method for exact near-field polarization localization using a COLD array is proposed.

## Key findings

- The proposed method constructs multiple polarization cumulant matrices and cascades them into a long matrix for signal subspace analysis.
- The method achieves joint estimation of angle, range, and polarization parameters using ESPRIT.
- The proposed approach outperforms existing methods in parameter estimation and matches theoretical asymptotic performance.

## Abstract

As a key technology for the fifth-generation of mobile communications, massive MIMO systems enable massive user access via large-scale arrays. However, their dense deployment extends the near-field (NF) region, introducing new localization complexities. Based on an exact spherical wavefront model, this paper proposes a multiple-cumulant-matrices-based method for NF source localization using a Co-centered Orthogonal Loop and Dipole (COLD) array. Firstly, following the physical numbering of array elements, we can construct multiple polarization cumulant matrices, which can then be cascaded into a long matrix. Next, the signal subspace can be obtained through eigen-decomposition of this long matrix, from which the horizontal and vertical components can be further separated. By applying ESPRIT, joint angle, range, and polarization parameters can be estimated. In addition, the asymptotic variances for joint spatial and polarization parameters are analyzed. Compared with existing NF polarization algorithms, the proposed method exhibits better parameter estimation and is consistent with a theoretical asymptotic performance.