Energy Neutral Devices: Can Hybrid RF Acoustic Signals Point Them Out?

TL;DR

This paper introduces a hybrid RF-acoustic positioning system for energy-neutral devices that improves localization accuracy and energy harvesting efficiency using advanced beamforming and a novel energy buffer.

Contribution

It presents a new hybrid signaling approach combining RF and acoustic signals, with an energy loading method and architecture that enhance positioning and energy harvesting.

Findings

Achieves 10 position updates per hour within regulatory constraints

Extends RF backscattering-based localization to 4.5 meters

Provides a comprehensive energy and power performance model

Abstract

We present a hybrid signaling approach to position energy-neutral devices. Our method combines the best of two worlds: instant RF signals for both communication and energy transfer, and slower propagating acoustic waves for accurate distance measurements. We introduce advanced energy loading of an 'E-buffer' through beamformed RF signals. The scientific contribution of our approach is twofold, advancing both the positioning performance and the energy harvesting efficiency. On the one hand, we overcome current distance limitations in RF backscattering-based indoor localization. On the other hand, it enhances the energy harvesting by using the calculated position and beamforming a higher amount of directed RF energy into the mobile node. We provide a functional architecture for both sides of the system and present a proof-of-concept. Practical measurements in representative use cases show an update rate of 10 positions per hour within the regulatory constraints in the 868MHz band for distances up to 4.5 m. An energy and power model are drawn up to provide insights into the performance trade-offs.