Underwater Communications

There is substantial interest in the design and deployment of underwater acoustic communication networks. Even though a number of acoustic modems to be used to create these networks are currently available as commercial and academic projects, these existing modems suffer from a major drawback; they are expensive, costing thousands to tens of thousands of dollars. In many application scenarios, including coral reefs, autonomous drifter swarms, and shallow water moorings, cost plays a significant role in the ability to use acoustic modems. For example, the additional money required to develop a wireless thermistor chain is substantial when the acoustic modem costs an order of magnitude more ($100s vs. $1000s) than the individual temperature sensor. A low cost, short range, wireless underwater modem will fill a significant void in aquatic technology, and provide substantial opportunities for building novel underwater sensor networks.

Underwater acoustic modems consist of three main components: 1. the analog front end consisting of an underwater transducer and matching pre-amp and amplifier for acoustic communication, 2. a hardware platform (microcontroller, digital signal processor (DSP), or field programmable gate array (FPGA)) for control and signal processing, and 3. interfaces to oceanographic sensors. The costs of the hardware platform and interfaces are negligible compared to the cost of the analog front end. Custom commercial transducers cost on the order of $2000 primarily because of the relatively low market demand for these devices. Therefore, the key component of a low-cost underwater modem is an inexpensive transducer. Our modem is built around a $10 piezoelectric ceramic element. While this does not make for an ideal transducer, it is capable of meeting all design specifications by carefully customizing the analog and digital modem design. This custom transducer functions effectively in a few kHz band around 35 kHz and can safely transmit at least 50 W of power in an omni-directional manner. Preliminary functional testing has shown that it is easily capable of transmitting and receiving data across Mission Bay (350 meters).

Presentation at CalIT2 10th Anniversary

Relevant Publications

Bridget Benson, Ying Li, Brian Faunce, Kenneth Domond, Don Kimball, Curt Schurgers and Ryan Kastner, “Design of a Low-Cost Underwater Acoustic Modem“, IEEE Embedded Systems Letters, to appear

Feng Tong, Shengyong Zhou, Bridget Benson and Ryan Kastner, “Development of a Dual Mode Acoustic Modem Testbed for Shallow Water Channels“, International Workshop on Underwater Networks (WUWNet), September 2010

Ying Li, Xing Zhang, Bridget Benson and Ryan Kastner, “Hardware Implementation of Symbol Synchronization for Underwater FSK“, IEEE International Conference on Sensor Networks, Ubiquitous, and Trustworthy Computing, June 2010 (pdf)

Feng Tong, Bridget Benson, Ying Li and Ryan Kastner, “Channel equalization based on data reuse LMS algorithm for shallow water acoustic communication“, IEEE International Conference on Sensor Networks, Ubiquitous, and Trustworthy Computing, June 2010

Bridget Benson, Ying Li, Ryan Kastner, Brian Faunce, Kenneth Domond, Donald Kimball and Curt Schurgers, “Design of a Low-Cost, Underwater Acoustic Modem for Short-Range Sensor Networks“, IEEE Oceans, May 2010 (pdf)

Ying Li, Bridget Benson, Ryan Kastner and Xing Zhang, “Bit Error Rate, Power and Area Analysis of Multiple Implementations of Underwater FSK“, International Conference on Engineering of Reconfigurable Systems and Algorithms (ERSA), July 2009 (pdf)

Bridget Benson, Ali Irturk, Junguk Cho and Ryan Kastner, “Energy Benefits of Reconfigurable Hardware for Use in Underwater Sensor Nets“, IEEE Reconfigurable Architectures Workshop (RAW), May 2009 (pdf, slides)

Bridget Benson, Ali Irturk, Jung Uk Cho and Ryan Kastner, “Survey of Hardware Platforms for an Energy Efficient Implementation of Matching Pursuits Algorithm for Shallow Water Networks”, International Workshop on Underwater Networks (WUWNet), September 2008 (pdf)

Bridget Benson, Frank Spada, Derek Manov, Grace Chang and Ryan Kastner, “Real Time Telemetry Options for Ocean Observing Systems”, European Telemetry Conference, April 2008 (pdf, slides)

Frank Spada, Derek Manov, Grace Chang, Bridget Benson, and Ryan Kastner, “Real-time Telemetry Technologies for Moored Oceanographic Applications“, Ocean Sciences Meeting, March 2008 – poster presentation

Bridget Benson, Grace Chang, Derek Manov, Brian Graham and Ryan Kastner, “Design of a Low-cost Acoustic Modem for Moored Oceanographic Applications”, International Workshop on Underwater Networks (WUWNet), September 2006 (pdf, slides)

Hua Lee, Tricia Fu, Daniel Doonan, Christopher Utley, Ronald A. Iltis and Ryan Kastner, “Design and Development of a Software-Defined Underwater Acoustic Modem for Sensor Networks for Environmental and Ecological Research”, MTS/IEEE Oceans, September 2006 (pdf)

Ronald A. Iltis, Hua Lee, Ryan Kastner, Daniel Doonan, Tricia Fu, Rachael Moore and Maurice Chin, “An Underwater Acoustic Telemetry Modem for Eco-Sensing”, MTS/IEEE Oceans, September 2005 (pdf, slides)

Acknowledgements

This work was funded in part by the National Science Foundation.