Communication through multi-layered acoustic electric channels

Abstract

Single layered acoustic-electric channels have been used in the recent past to send power and data through metallic barriers wirelessly. These penetration-free solutions are valuable for maintaining the structural integrity while providing needed connec- tivity. Most of the previous work has considered single-layered channels, though in many applications one will encounter multi-layered channels that include one or more metallic barriers and fluid layers like water etc. This work presents communi- cation schemes that can be used to send data through such multi-layered acoustic- electric channels. First, the measured characteristics of several multi-layered acous- tic electric channels are presented and modeled, including those consisting water sandwiched between steel plates and concentric pipes as well as those that extend axially along a steel pipe. The channels are found to be very frequency selective. Second, low data rate, low complexity communication techniques are developed for these channels. Chirp-FSK and Chirp-OOK with non-coherent detection are studied through theoretical analysis and Monte-Carlo simulations using measured channel data. Chirp-OOK with energy detection is found to provide a good compromise be- tween performance and implementation simplicity. Hardware implementations are designed, constructed and tested on the actual channels. A standalone embedded design of the communication link is used to send at a rate of 100 bps using 5 mW of transmit power. Lastly, communication schemes to send data at higher rates (tens of kbps) through such multi-layered channels are considered. One such scheme, using a Decision Feedback Equalizer with 16-QAM modulation is found to be effective for one of the channels.