Dr. Stojanovic of Northeastern University/IEEE Oceanic Engineering Society

Underwater Acoustic Communications: Fundamentals and New Results

Milica Stojanovic

Northeastern University

millitsa@ece.neu.edu

Underwater wireless communications rely on transmission of acoustic waves, since electro-magnetic waves propagate only over very short distances. Acoustic communications thus form an integral part of autonomous undersea systems, which find application in basic sciences (oceanography, marine biology), industry (off-shore oil, aquaculture), environment monitoring (climate, pollution, seismic disturbances) and security (search-and-rescue, surveillance).

Acoustic waves, however, are confined to low frequencies because of energy absorption (usually no more than several tens of kHz), and the bandwidth available for communication is extremely limited. Sound travels underwater at a very low speed (nominally 1500 m/s) and propagation occurs over multiple paths. Delay spreading over tens or even hundreds of milliseconds results in a frequency-selective signal distortion, while motion creates an extreme Doppler effect. The worst properties of radio channels—poor link quality of a mobile terrestrial channel, and long delay of a satellite channel—are thus combined in an underwater acoustic channel, which is often said to be the most difficult communication medium in use today.

The quest for bandwidth-efficient acoustic communications has progressed over the past few decades from an initial feasibility proof of phase-coherent detection, to the development of the first high-speed acoustic modem, and finally to a plethora of innovative solutions on both the signal processing and the networking fronts. In this presentation, we begin with an overview of channel characteristics, focusing on the major differences between underwater acoustic and terrestrial radio channels. We follow with a discussion of signal processing methods, briefly overviewing single-carrier broadband equalization used in an existing acoustic modem, and focusing on recent research results in multi-carrier signal detection on highly time-varying, Doppler-distorted channels. The performance of various techniques is illustrated through experimental results, which include transmissions over few kilometers in shallow water to hundreds of kilometers in deep water, at highest bit-rates demonstrated to date. We conclude by outlining the open research problems.

Biography:

Milica Stojanovic graduated from the University of Belgrade, Serbia, in 1988, and received the M.S. and Ph.D. degrees in electrical engineering from Northeastern University in Boston, in 1991 and 1993. She was a Principal Scientist at the Massachusetts Institute of Technology, and in 2008 joined Northeastern University, where she is currently a Professor of electrical and computer engineering. She is also a Guest Investigator at the Woods Hole Oceanographic Institution. Her research interests include digital communications theory, statistical signal processing and wireless networks, and their applications to underwater acoustic systems. Milica is a Fellow of the IEEE, and serves as an Associate Editor for its Journal of Oceanic Engineering (and in the past for Transactions on Signal Processing and Transactions on Vehicular Technology). She also serves on the Advisory Board of the IEEE Communication Letters, and chairs the IEEE Ocean Engineering Society’s Technical Committee for Underwater Communication, Navigation and Positioning. Milica is the recipient of the 2015 IEEE/OES Distinguished Technical Achievement Award.

Email:

Address:Northeastern University, , Boston, United States

Dr. Stojanovic of Northeastern University/IEEE Oceanic Engineering Society

Biography:

Email:

Address:Boston, United States