Through-Substrate Event Reporting Using Harvested Energy in Ultrasound Sensor Networks

This paper develops an energy-aware and through- substrate sensor network using a Pulse Switching (PS) architecture for Structural Health Monitoring applications. Pulse Switching based protocols as developed in our prior work use single pulses instead of multi-bit packets for information delivery with ultra high energy-efficiency. Such packet-less networking is shown to be sufficient for event monitoring applications with binary sensing requirements. Pulse Switching using ultrasound, in particular, is well suited for communication through metal/composite substrates used in structures such as bridges, aircraft wings, etc. This paper presents a joint MAC- Routing architecture and its associated algorithms for Pulse Switching using an ultrasonic through- substrate physical layer. It also develops novel energy-aware protocol syntaxes in the PS domain for reliable operation in intermittently energy- constrained systems such as those powered by vibration energy harvesting. Experimental evaluation of a through-substrate pulse modem and ultrasonic pulse data-link is presented for demonstrating the feasibility of a pulse based ultrasonic physical layer. Using simulation experiments, it is shown that the proposed energy- aware mechanisms can offer a performance-enhanced through-substrate network that can be reliably used for structural health monitoring using energy harvested from structure vibrations.