The objective of this research is to address one of the greatest challenges that hinder the development of underwater sensor networks into practical systems: How to ensure data reliability and delivery efficiency over unreliable acoustic links with large error rates, low available bandwidth, and long propagation delays. The project proposes an integrated coding approach, seamlessly combining digital fountain, and network and channel coding schemes with complementary strengths, across the application, network, and physical layers.
The intellectual merit of this project lies in the rigorous study of the underwater network limits and a systematic design of powerful fountain and network coding schemes to address the challenging issues facing underwater sensor networks. The project outcomes will include physical layer network coding theoretical results, novel non-binary fountain codes, sparse linear network codes, and physical-layer network coding schemes for underwater channels, as well as networking protocols for underwater unicast scenarios. The theoretical results, coding, and protocol designs will be evaluated through real world experiments.
The broader impact of this project is reflected in two aspects. First, this project is expected to accelerate the development of emerging underwater sensor networks, which will have major impact on scientific communities, national security, and the society as a whole. Second, this project will expose graduate students to new challenging research problems, fostering them to become leading experts in the fast-growing field of underwater acoustic networks. It will also support undergraduates, women and other under-represented groups, allowing them to participate in advanced research and its practical applications.
Underwater sensor network applications can contribute to solve a wide range of problems, such as estuary (river, lake, or other water resource) monitoring, tracking pollution flows, such as oil spills, marine biology applications such as sampling the marine microorganisms. However, the water world represents a dynamic and harsh physical environment. Further, in underwater environments, radio does not work well and must be replaced by acoustic communications. Acoustic channels are much more unstable relative to radio channels. How to ensure data reliability and delivery efficiency over unreliable acoustic links represents one of the greatest challenges that hinder the development of UWSNs into practical systems. NSF-funded researchers at the University of Connecticut project tackle this challenge through an integrated coding approach, integrating digital fountain, network, and channel coding schemes across the application, network, and physical layers. Over the past three years, several innovative coding and protocols have been developed, and disseminated into the community via seven journal papers, nine conference presentations and one tutorial. Some selected designs have also been validated using field networking testbeds. One notable example is a dynamic coded cooperation (DCC) scheme, which allows relay diversity without altering the transmission procedure from the source to the destination. For example, a surface node with more capabilities can help the communication of two underwater nodes, without introducing any changes to the communication procedure between the nodes. A practical orthogonal-frequency-division-multiplexing (OFDM) modulated DCC scheme was proposed for underwater relay networks, where OFDM modulation accommodates multipath fading channels with large delay spread. This design has been tested in a recent sea experiment in Kaohsiung, Taiwan, May 26, 2013, which is the first real-time sea test of cooperative underwater communications in the community. The project has also supported the training of many graduate students as well as undergraduate students at the Department of Electrical and Computer Engineering and the Department of Computer Science and Engineering at the University of Connecticut. The research work directly trains and helps the graduate students towards their degree objectives. Undergraduate students have been involved through senior design projects. Graduate students have been tutoring undergraduate class projects, fostering synergic and productive teamwork.