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Underwater Acoustics

What is Underwater Acoustics 

Underwater Acoustics encompasses all communications performed in an underwater environment using acoustic pressure waves as information carrying signals. Acoustics are well suited to the underwater environment because they do not suffer from the high attenuation experienced by radio waves in a conducting medium, enabling the possibility of long-range communications. However, the field is not without its own set of unique challenges. The low frequencies required for long-range communications, the long propagation times associated with transmission of acoustic waves, motion of the transceivers, and the numerous reflections and scattering caused by the surface and seabed make high data rate communications difficult in this environment. 

Why are we Interested

Underwater Acoustics have a number of interesting applications and present a number of complex challenges, which are not faced in the traditional radio environment. Overcoming these challenges is of great interest to the team at UMDCC and our industrial partners. Significant work has been done in this area but there remains a large gap between what is currently available and what is possible; our goal is to close that gap.

How are we Contributing

By starting at the fundamentals we are developing a statistical model, which encompasses all the channel impairments. With this model we will be able to develop an intelligent modem capable of adapting to the ever-changing conditions encountered in the underwater environment. To accomplish this the team is focusing primarily on the development and testing of OFDM signaling methodologies for underwater communications and advanced estimation techniques capable of tracking the constantly changing underwater environment. 

Recent Resources:

1. Poster for National Science Foundation Conference on Underwater Acoustics in Washington, D.C. March 19-20, 2018. 

2. Schlegel, Christian and Marat Burnashev, "The Interplay Between Error Control Coding and Iterative Signal Cancelation," IEEE Transactions on Signal Processing, Vol. 65, Lo. 11, June 1, 2017. This paper discusses the type of codes that are most effective in cancelation systems, to wit: either low rate repetition coding or high-rate low-density parity-check codes. Link to Paper

3. Schlegel, Christian, Dmitri Truhachev, and Lukasz Krzymien, "A Two-Stage Capacity-Achieving Demodulation/Decoding Method for Random Matrix Channels," IEEE Transactions on Information Theory, Vol. 55, No. 1, January 2009. This paper describes how adaptive modulation is achieved by generalized modulation superposing independent data streams with iterative demodulation. Link to Paper

4. Schlegel, Christian, Marat Burnashev, and Dmitri Truhachev, "Generalized Superposition Modulation and Iterative Demodulation: A Capacity Investigation," Journal of Electrical and Computer Engineering Volume 2010, August 2010. Link to Paper