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Design of Passive Radars based on Wi-Fi 802.11ax Signals

par Yildirim, Hasan Can
Président du jury Craeye, Christophe
Promoteur Horlin, François ;Louveaux, Jérôme
Co-Promoteur De Doncker, Philippe
Publication Non publié, 2022-09-26

Thèse de doctorat

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Résumé :

In the past 20 years, Wi-Fi technologies have evolved to satisfy the high throughput demands in wide variety of scenarios. In the meantime, Passive WiFi-based Radars (PWRs) and related applications attracted the attention of both the academy and the industry. The goal in PWR is to detect and track humans and/or other objects by applying radar processing schemes to existing Wi-Fi signals. However, the newly introduced technologies that solve Wi-Fi traffic issues, bring challenges for PWR processing and reliability.This thesis addresses challenges related to the PWRs, and aims at transforming it from an academical topic to a practical real-life system. In order to achieve this, there are three crucial ingredients: i) we have to understand the 802.11ax standard; ii) we have to be able to make realistic experiments, and iii) we have to provide insights as well as solutions to the problems introduced by the standard. To this extent, Chapter 2 and 3 summarizes the fundamentals of radars and the Wi-Fi signals, respectively. When brought together, these chapters form the pillars of the PWR framework. Chapter 4 details more practical issues faced when designing/experimenting with Software Defined Radios in the context of PWRs. In Chapter 5, a novel super-resolution parameter estimation algorithm is proposed, as well as a novel Model Order Selection metric. Extensive numerical analyses show that the proposed algorithm yields radar parameter estimates with sub-meter/meter-per-second accuracy which are validated with experimental results. Chapter 6 addresses the two major issues brought by the introduction of MU-MIMO to the Wi-Fi standards: i) the decreased radar coverage due to digital beamforming, and ii) the aggregation of data and radar channel coefficients, yielding range estimation errors. Finally, Chapter 7 addresses the impact of interference on the PWR reliability through numerical analyses and experimental results.