Array-gebaseerde hybride RF-akoestische positionering van zeer lage energie apparaten

From navigating urban environments to tracking deliveries and optimizing supply chains, the ability to pinpoint and leverage location data is essential in today's interconnected world. These applications also extend to indoor areas, where the demand for location-based services is rapidly growing. Increasingly, these services demand for precise and energy-efficient localization - both needs that are not adequately met by the solutions currently available in today's market. To address this challenge, this work focuses on a hybrid solution based on acoustic and radio frequency waves. The presented system leverages the slower propagating acoustic signals to achieve centimeter ranging and a radio frequency link to provide synchronization and energy-efficient data transfer. Moreover, low-complexity components are used, consuming relatively little energy as they operate at low system frequencies. Accurate acoustic localization becomes challenging when the energy consumption of the mobile, tracked device is pushed to its lower limits. A recent hybrid RF-acoustic ranging scheme based on the pulse compression of ultrasound chirps has shown great potential in this regard. By limiting the active time of the tracked device, the energy consumption can be kept significantly low, but it leaves the time-constrained, captured acoustic signal vulnerable to multipath interference. To increase the ranging performance without deteriorating energy consumption, this work introduces an original design based on ultrasound phased arrays. Phased loudspeaker arrays provide dynamic control over the spatial distribution of ultrasound transmissions. They not only make it possible to increase the signal power in the direction of the tracked device, but they are also able to mitigate multipath propagation. This improves the signal-to-noise ratio of the captured acoustic signal, and ultimately the overall ranging performance. Aiming towards complete energy-neutral positioning in which the mobile device is wirelessly energized, an innovative ultra-low power hardware design with RF energy harvesting is established. Furthermore, a novel ultrasound phased array prototype optimized for indoor ranging is presented, featuring commercial off-the-shelf components. In search of an optimal array design, the performance of various array configurations is evaluated in terms of ranging accuracy within several shoe-box rooms. Both geometrical acoustic-based simulations and practical experiments have shown their employability to improve accuracy at low energy consumption. Measurements analyzing the energy consumption and RF charge time of the presented ultra-low power hardware show insights in the practicality of the presented technology. In conclusion, this approach not only advances the field of indoor localization but also sets the stage for future developments in energy-efficient, accurate positioning systems.