A Variational Message Passing Framework for Multi-Sensor Multi-Object Tracking using Raw Radar Signals

TL;DR

This paper introduces a variational message passing framework for direct multi-object tracking from raw radar signals, effectively handling unknown object counts and low-SNR conditions in multi-radar systems.

Contribution

It develops a novel probabilistic VMP-based method that processes raw radar data directly, outperforming traditional approaches in challenging cluttered environments.

Findings

Outperforms conventional super-resolution and belief propagation methods in low-SNR scenarios.

Effectively models object existence, reflectivities, and link reliability with hierarchical Bernoulli-Gamma models.

Demonstrates improved detection and tracking accuracy in synthetic cluttered scenarios.

Abstract

The growing proliferation of unmanned aerial vehicles (UAVs) poses major challenges for reliable airspace surveillance, as drones are typically small, have low radar cross-sections, and often move slowly in cluttered environments. These characteristics make the joint tasks of detecting, localizing, and tracking multiple objects difficult for conventional detect-then-track (DTT) approaches, which rely on pre-processed measurements and may discard informative low-signal-to-noise ratio (SNR) signal components. To overcome these limitations, we propose a variational message passing (VMP)-based direct multiobject tracking (MOT) method that operates directly on raw radar signals and explicitly accounts for an unknown and time-varying number of objects. The proposed method is formulated for MIMO multi-radar systems and performs data fusion by jointly processing the signals of all radar sensors using a probabilistic model. A superimposed signal model is employed to capture correlations in the raw sensor data caused by closely spaced objects, and a hierarchical Bernoulli-Gamma model is introduced to jointly model object existence, reflectivities, and the reliability of individual radar-object links. Using a mean-field approximation, we derive message updates, yielding a computationally efficient VMP algorithm that simultaneously performs object detection, track formation, state estimation, and nuisance parameter learning directly from the radar signal. Simulation results in synthetic scenarios with weak and closely-spaced objects show that the proposed direct-MOT method outperforms a conventional pipeline based on super-resolution estimation followed by belief propagation (BP)-based tracking, particularly in low-SNR and clutter-rich conditions, demonstrating the advantages of direct signal-level inference and coherent multi-radar fusion.