Abstract
Hybrid acoustic-RF systems offer excellent ranging accuracy, yet they typically come at a power consumption that is too high to meet the energy constraints of mobile IoT nodes. We combine pulse compression and synchronized wake-ups to achieve a ranging solution that limits the active time of the nodes to 1 ms. Hence, an ultra low-power consumption of 9.015 µW for a single measurement is achieved. The operation time is estimated on 8.5 years on a CR2032 coin cell battery at a 1 Hz update rate, which is over 250 times larger than state-of-the-art RF-based positioning systems. Measurements based on a proof-of-concept hardware platform show median distance error values below 10 cm. Both simulations and measurements demonstrate that the accuracy is reduced at low signal-to-noise ratios and when reflections occur. We introduce three methods that enhance the distance measurements at a low extra processing power cost. Hence, we validate in realistic environments that the centimeter accuracy can be obtained within the energy budget of mobile devices and IoT nodes. The proposed hybrid signal ranging system can be extended to perform accurate, low-power indoor positioning.
Highlights
Accurate positioning of users and devices plays a major role in the growing number of location-aware applications
The operation time is estimated on 8.5 years on a CR2032 coin cell battery at a 1 Hz update rate, which is over 250 times larger than state-of-the-art Radio frequency (RF)-based positioning systems
Hybrid signal ranging [2, 3] combines the advantages of both wave types: an RF signal is used as timing reference and the time difference with the slower propagatingsound signal is used to calculate the distance
Summary
Accurate positioning of users and devices plays a major role in the growing number of location-aware applications. In time-based localization ranging systems, acoustic signals are inherently interesting candidates for precise ranging thanks to their relatively low propagation speed. They do not require high processing speeds, nor the same level of synchronization accuracy as RF-based systems. The first is a novel hybrid RFacoustic signaling that performs a just-in-time wake-up of the nodes This concept enables ultra low power consumption at the mobile node. The presented technology enables ultra low power localization in several industrial and healthcare applications like wayfinding and contact tracing in large venues, real-time customer behavior analysis in retail, indoor positioning in large warehouses and production sites, and wander detection and localization of residents in assisted living facilities. The section introduces the chirpbased ranging concept, focusing on high accuracy and ultra-low power consumption. The last section of this paper summarizes the conclusions and discusses the potential future work
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