Communication using GNU Radio and Ultrasound Practical Application

Abstract

This research is based on using modulated ultrasound
at high frequency in the audio band as a way to
communicate between devices located in air, liquid,
containers (such as shipping) and rail vehicles. It is
an alternative solution to using a traditional radio
system in places where RF does not propagate well
such as enclosures, or structures that obstruct the
radio signals.
The project was initially based on shipping
containers that normally use 4G modems mounted on
the outside of the containers as a way to
communicate its ID along with environment data to
the asset manager allowing cargo that may be
sensitive to heat, humidity, vibration to be monitored.
If the containers are stacked in rows adjacent to each
other, the communication system can fail when the
container in the middle cannot transmit a signal out
of the stack or connect to the local mobile base
station. Ad Hoc sensor networks can be created to
allow audio communication to nodes (containers)
located on the outside of the stack where that
information would re-transmitted using the 4G
modem that has a network connection.
Acoustic communication is also a great solution in
water or other liquids where radio signals degrade
quickly over short distances. The GNU radio FSK
solution provided some excellent results for liquids
and allowed me to leverage from this to using OFDM
at a later phase in steel rail. This paper focuses on
modulating data through water and other liquids.
The advances in software (GNU radio/Linux OS),
D/A converters and micro-PCs that have fast
processors allowing these devices to be sourced at
reasonable cost, operate at low power along with a
compact robust design makes them suitable for this
type of application.
It is now possible to utilize these advances in
software that could not have been possible 10 years
ago.