Prof. Milica Stojanovic

Northeastern University

Milica Stojanovic (SM’08, F’10) graduated from the University of Belgrade, Serbia, in 1988, and received M.S. (’91) and Ph.D. (’93) degrees in electrical engineering from Northeastern University, Boston, Massachusetts. 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. She is an Associate Editor for the IEEE Journal of Oceanic Engineering and has also served on the editorial boards of the IEEE Transactions on Signal Processing, Vehicular Technology, Communication Letters and Signal Processing Magazine. She chairs the IEEE Ocean Engineering Society’s (OES) Technical Committee for Underwater Communication, Navigation and Positioning. Milica is the recipient of the 2015 IEEE OES Distinguished Technical Achievement Award,  2018 IEEE OES Distinguished Lectureship, 2019 IEEE WICE Outstanding Achievement Award, and 2023 IEEE Communications Society’s Stars in Computer Networking and Communications Award.  In 2022, she was awarded an honorary doctorate from the Aarhus University in Denmark, and was elected to the Academy of Engineering Sciences of Serbia.

Underwater wireless communication is an enabling technology for applications ranging from basic sciences such as oceanography and marine biology, to offshore oil and gas industry, fish farming, exploratory missions, discovery of objects on the seafloor, as well as climate monitoring and pollution control. Electro-magnetic waves do not propagate through water except over short distances, leaving acoustic waves as the preferred choice for many of these applications.

Acoustic waves, however, are confined to low frequencies (usually up to a few tens of kHz), and the communication bandwidth is limited.  Sound travels underwater at a very low speed (1500 m/s) and propagation occurs over multiple paths. Delay spreading results in a frequency-selective channel, 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 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 acoustic and radio channels. We follow with a discussion of signal processing methods, including both single-carrier and multi-carrier signal detection on 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.  Finally, we discuss several issues important for the design of underwater acoustic networks. We conclude by outlining the open research problems.