ABOUT THE IMAGE
This is a schematic outline of the ITR Project ROADNet (Real-time Observatories, Applications, and Data management Network): Bringing the Information Superhighway to the Dirt Road and the High Seas. The goal is to develop both the wireless networks and integrated, seamless, and transparent information management system that will deliver seismic, oceanographic, hydrological, geodetic, ecological, and physical data to a variety of end users in real-time. The project is funded by the NSF and ONR with matching funds from the UCSD California Institute for Telecommunications and Information Technology [Cal-(IT)2], Scripps and IGPP. Much of the land-based network has already been installed by the SDSC/IGPP HPWREN (High Performance Wireless Research and Education Network) funded by the NSF.

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Cost of Link = Fcn {Satellite resources used; duration of lease}

Satellite resources used = MAX [link bandwidth; required satellite power]

Ship to Shore
Limiting
Factor
Link
Data
Rate
(kbps)
Equivalent Bandwidth (Satellite Resources)

Beam Edge
(kHz)
Relative
Cost
Beam Center
(kHz)
Relative
Cost
Link
Bandwidth
6.4
97.2
1.0
97.2
1.0
256
388.9
4.0
388.9
4.0
Shore to Ship
 
Satellite
Power
19.2
187.2
1.9
29.2
0.3
6.4
619.2
6.4
97.2
1.0
LINK ECONOMICS
The satellite resources required for a given link, usually expressed in terms of equivalent satellite bandwidth, are a function of the link data rate and the power of the received satellite signal that, in turn, depends upon the ship's location. In the table above examples of satellite resources required are given for different link rates at beam edge and beam center on the INTELSAT global beam (see figure below). For a 19.2 kbps data rate on the shore-to-ship link, which is satellite power limited as the ship moves from beam edge to beam center example, the equivalent satellite bandwidth decreases from 187.2 kHz to 29.2 kHz! Because cost is proportional to equivalent bandwidth, this is a big difference.

 

THE HIGH-SEAS EXTENSION OF ROADNet
Using the global beam of the Intelsat satellite at 180° longitude, ROADNet is able to cover most of the Pacific Ocean. Shown schematically are several ships, fixed island stations and deep ocean moored buoys (DEOS). From the hub station in La Jolla, the network can be dynamically configured to make the best use of leased satellite bandwidth as the ships move within the satellite's beams and traffic demands change.

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