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Tutorial-01: Acoustic Networking in MOOS using pAcommsHandler

Toby Schneider
MIT, Dept. of Mechanical Engineering, Laboratory for Autonomous Marine Sensing Systems

Wed Jul 20th, 1230pm-130pm, MIT Building 32 Room 124 (Stata Center)

Abstract:
Acoustic waves are often the only practical carrier for sub-sea communica- tions due to the short propagation distances of light and radio waves in sea water. Using acoustics, however, has its limitations. Due to the realities of sound propagation, the acoustic channel is severely limited in throughput and typically has high latency. These constraints require special treatment at all levels of the network from hardware to the application layer.

In this tutorial we will focus on the application pAcommsHandler [1], which is the MOOS interface to a suite of C++ acoustic networking libraries called goby-acomms [2]. Currently, the hardware supported is the WHOI Micro- Modem. We will learn how to

• Define structures for compact short messages suitable for sending over the acoustic channel using the Dynamic Compact Control Language (DCCL) (which extends XML). DCCL is implemented in goby-acomms libdccl and discussed in [3].
• Configure message queues for different types of messages to dynamically assign priorities to messages based on the overall value and time-sensitivity of the data using goby-acomms libqueue.
• Deal with medium access control (MAC) in the underwater channel using goby-acomms libamac.
• Discuss issues pertaining to using the WHOI Micro-Modem and how we can to extend goby-acomms to work with other hardware.

At the end of the tutorial, you will be able to configure and use pAcommsHandler to communicate seamlessly amongst MOOS-based undersea vehicles and other acoustic modem equipped nodes.

Related Material:

• Tutorial material given at MOOS-DAWG 2010

References

[1] T. Schneider and H. Schmidt, “A compact control language for autonomous underwater vehicles,” MIT, Tech. Rep. LAMS-09-03, 2010. [Online]. Available: http://gobysoft.com/resources/docs/comms_stack.pdf

[2] T. Schneider, “Goby underwater autonomy project.” [Online]. Available: https://launchpad.net/goby

[3] T. Schneider and H. Schmidt, “The Dynamic Compact Control Language: A compact marshalling scheme for acoustic communications,” in Proceedings of the IEEE Oceans Conference 2010, Sydney, Australia, 2010. [Online]. Available: http://gobysoft.com/resources/dccl_oceans10.pdf