# Multipath Credibility Selection for Robust UWB Angle-of-Arrival Estimation in Narrow Underground Corridors

## TL;DR

This paper introduces a new method for accurately estimating angles of arrival in underground tunnels using ultra-wideband signals, improving upon existing techniques.

## Contribution

The novel multipath credibility selection (MCS) algorithm improves angle-of-arrival estimation by evaluating and fusing multiple CIR components without requiring LOS/NLOS classification.

## Key findings

- MCS-AoA achieves 1.00°/1.46° azimuth/elevation MAE in underground corridors, outperforming existing methods.
- In logistics tunnels, MCS-AoA achieves 1.19° azimuth MAE, significantly better than other techniques.
- Simulations show a 69.3% reduction in azimuth RMSE compared to PDOA at 80 m.

## Abstract

Waveguide-like propagation in elongated underground environments—utility corridors, logistics tunnels—generates dense multipath that can cause the earliest or strongest resolvable channel impulse response (CIR) component to originate from a specular reflection rather than the direct line-of-sight (LOS) path. In the single-anchor CIR-tap-based implementations common to practical ultra-wideband (UWB) systems, baseline estimators such as phase-difference-of-arrival (PDOA) and MUSIC rely on selecting a single dominant CIR component, producing large angle-of-arrival (AoA) errors whenever the selected path is a reflection. We propose a multipath credibility selection (MCS) AoA estimator, MCS-AoA, that does not require explicit LOS/NLOS classification. The algorithm scores each resolvable CIR component with four credibility factors—amplitude significance, time-of-flight (TOF) consistency, inter-baseline phase–geometry agreement, and cross-baseline coherence—and fuses retained candidates into a credibility-weighted spatial covariance matrix for 2D MUSIC search. Field experiments on a custom five-channel coherent UWB platform compare MCS-AoA against six baselines—PDOA, MUSIC, MVDR/Capon, TLS-ESPRIT, PwMUSIC, and DNN-AoA. In an underground corridor (5–40 m), MCS-AoA achieves an azimuth/elevation MAE of 1.00°/1.46°, outperforming all baselines (PDOA: 2.26°/2.49°; MUSIC: 1.76°/2.40°; next-best PwMUSIC: 1.44°/2.17°); in a logistics tunnel (5–80 m), it achieves a 1.19° overall azimuth MAE. Simulations corroborate these gains, with a 0.71° azimuth RMSE at 80 m (69.3% reduction over PDOA) and 86.6% of estimates falling within 1°.