Underwater communications is a challenge. Radio waves quickly attenuate and visible light doesn't penetrate very far. To get high speed robust communications at any depth you need to be tethered by a cable. Of course that is too limiting for many applications.
Acoustic waves can propagate for long distances and people have built acoustic modems for some time. These are challenging to design and have tended to be application specific. So it is interesting to see a commercial undersea modem modified to use an IP compatible protocol stack -- the Internet underwater... (pdf)
The Internet Underwater: An IP-compatible Protocol Stack for Commercial Undersea Modems
Yifan Sun Department of Electrical Engineering State University of New York at Buffalo
Tommaso Melodia Department of Electrical Engineering State University of New York at Buffalo
Recent underwater sensor network research has focused on developing physical, medium access control, and network layer protocols to enable high data rate, energy-efficient and reliable acoustic communications. However, it is now essential to design and standardize architectures that will enhance the usability and interoperability of underwater networks.
This paper proposes a networking architecture to efficiently provide interoperability with traditional TCP/IP protocol stacks for commercial underwater modems. The proposal is based on an adaptation layer located between the data link layer and the network layer, such that the original TCP/IP network and transport layers are preserved un-altered to the maximum extent. The adaptation layer performs header compression and data fragmentation to guarantee energy efficiency. Furthermore, the proposed architecture includes mechanisms for auto-configuration based on router proxies that can avoid human-in-the-loop and save energy when broadcast is needed. The proposed architectural framework was implemented as a Linux device driver for a commercial underwater network modem SM-75 by Teledyne Benthos. Testing and simulation results illustrate that the architecture efficiently provides interoperability with TCP/IP.