Underwater Acoustic Communications: Building a Universally Accessible Repository of Standard Channel Models
Abstract
The goal of this project is to build a repository of underwater acoustic channel models for purposes of testing and comparing candidate communication, networking, and other signal processing algorithms in a common framework. The repository will be publicly available through an open-access website. It will contain a variety of channel models that are typical of diverse environments (shallow/deep water, short/long range, mobile/fixed platforms, geographically diverse locations, etc.). The models will include multipath, Doppler, and noise characteristics. The repository will also contain a comprehensive and simple-to-use interface that will facilitate application of the channels to the users# signals. The motivation for our work is that widely accepted, standardized acoustic channel models do not exist at this time, yet they are sorely needed by researchers and practitioners around the world, notably those who donot have access to at-sea experiments or real data. Although major advanceshave been made in underwater acoustic communications andseveral channel modeling tools have recently been developed, the community has never agreed on a set of standard channel models. The need for common channel models has meanwhile been repeatedly emphasized in publications, workshops, and meetings. This situation is in stark contrast to terrestrial radio communications, where standard channel models have existed for decades. These models are not only standard in practice but are also standardized by international bodies such as ITU (International Telecommunications Union), IEEE, and others. Wide availability of such models was instrumental in the development of radio communication systems as we know them today. Widespread adoption of common models notably enables a democratization of research, making it possible for those without extensive experimental facilities to participate in the advancement of the field.Two approaches can be considered in building a communication channel model. The first is to provide the channel as-recorded, i.e., estimated from the at-sea recordings and stored as a series (a matrix) of impulse responses evolving over time. The response captures the instantaneous delay spreading (multipath), whilethe time variation captures Doppler effects. The latter consist of motion-induced frequency shifting which can be decoupled from the rest of the channel, and frequency spreading such as that caused by surface scattering which results in random signal fluctuations. Instead of providing a record of random variations, the second approach to channel modeling instead provides the parameters of an underlying statistical model. While each approach has its strengths and weaknesses, we will initially focus on the first approach, as it provides actual channel observations, and can subsequently be used to infer statistical models. The acoustic channel models will be derived from existing at-sea recordings, which include several ONR-supported experiments (e.g., KAM#11, MACE#10 and SPACE#08), as well as experiments conducted in Norwegian waters, in the Mediterranean Sea and in the waters of Singapore. Upon defining a set of channels typical of certain locations and propagation conditions, the salient responses will be extracted from the recordings using state-of-the-art methods for Doppler and channel estimation. The models will capture all the difficulties of acoustic propagation but will at the same time be simple enough to use, thus having a chance of being embraced by a large community. If successful, our hope is that the repository will become a go-to resource for researchers and practitioners around the world, and that the channel models will become a standard for design, testing, comparison, and performance prediction of acoustic communication systems and other underwater acoustic signal processing tasks.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 11, 2023
- Source ID
- N000142312852
Entities
People
- Milica Stojanovic
Organizations
- Northeastern University
- Office of Naval Research
- United States Navy