Robust position sensing with wave fingerprints in dynamic complex propagation environments

Philipp Del Hougne

doi:10.1103/physrevresearch.2.043224

Abstract

Irregular propagation environments with complex scattering effects challenge traditional ray-tracing-based localization. However, the environment's complexity enables solutions based on wave fingerprints (WFPs). Yet, since WFPs rely on the extreme sensitivity of the chaotic wave field to geometrical details, it is not clear how viable WFP techniques may be in a realistic dynamically evolving environment. Here, we reveal that environmental perturbations reduce both the diversity of the WFP dictionary and the effective signal-to-noise ratio (SNR), such that the amount of information that can be obtained per measurement is reduced. This unfavorable effect can, however, be fully compensated by taking more measurements. We show in simulations and experiments with a low-cost software-defined radio that WFP localization of non-cooperative objects is possible even when the scattering strength of the environmental perturbation significantly exceeds that of the object to be localized. Our results underline that diversity is only one important ingredient to achieve high sensing accuracy in compressed sensing, the other two being SNR and the choice of decoding method. We find that sacrificing diversity for SNR may be worthwhile and observe that artificial neural networks outperform traditional decoding methods in terms of the achieved sensing accuracy, especially at low SNR.

Highlights

Precise position sensing is a highly sought ability for countless context-aware devices in our modern life, including wireless communication with new-generation protocols relying on beam forming, high-value asset tracking and customer analytics in retail, ambient-assisted living solutions for remote health care, untethered virtual reality, intruder localization in classified facilities, and victim-detection technologies for first responders
We investigate an interpretation of the perturber as effective source of noise and the extent to which the perturber affects the diversity of the wave fingerprints (WFPs) dictionary
Dynamic perturbations of the propagation environment are introduced in our experiment with a metallic object of variable size mounted on a stepper motor which can place the object in an arbitrary angular orientation

Summary

Introduction

Precise position sensing is a highly sought ability for countless context-aware devices in our modern life, including wireless communication with new-generation protocols relying on beam forming, high-value asset tracking and customer analytics in retail, ambient-assisted living solutions for remote health care, untethered virtual reality, intruder localization in classified facilities, and victim-detection technologies for first responders. Microwave-based sensing solutions are appealing due to their ability to operate through optically opaque materials or fog, their independence of external illumination and target color, limited potential privacy infringements, and the nonionizing nature of microwaves. Existing wireless infrastructure can often be leveraged, endowing it with a dual communication and sensing functionality. Traditional microwave position sensing relies on ballistic wave propagation and leverages ray-tracing approaches, the simplest example being triangulation. The above-listed applications involve irregular propagation environments which give rise to significant multipath effects.

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Conclusion