Abstracts Category : Other

Design of energy-efficient ultrasonic communication systems on steel pipes

by Sijung Yang

Ultrasonic communication provides an alternative to radio-frequency (RF) by transmitting guided ultrasonic signals along installed or buried metallic pipes. Buried pipe corrosion monitoring and intermittent infrastructure data collection are potential application areas, for which reliable wireless links are unavailable, due to strong RF attenuation in soil, or through shielded building infrastructure. When designing a network of such links, energy efficiency, defined as the average energy per transmitted bit, can be far more important than Shannon capacity, for such battery-powered, relatively inaccessible links. This work focuses on the low-rate, total life-time energy-limited regime to maximize battery life, while maintaining reliable information transfer at a nominal average rate. The strong frequency selectivity of the through-pipe ultrasonic channel poses several challenges for low-power systems, including strong intersymbol interference (ISI). Previous works have suggested a variety of ad hoc design schemes to implement low-power communication systems satisfying minimum data rate requirements under highly frequency selective and lossy conditions, but failed to propose a systematic methodology to optimize design parameters for energy efficiency. In this work, we apply the concept of energy efficiency maximization to ultrasonic communication over steel pipe channels. A cross-layer approach accounting for both transmit power and signal processing power is suggested, where frequency division multiplexing is explored to counter frequency selectivity. Finally, bits-per-Joule capacity of this channel, based on experimentally measured channel responses, are determined numerically, and an example of an optimized multi-tone frequency shift keying (MFSK) scheme is suggested.Advisors/Committee Members: Singer, Andrew C (advisor).