|
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.
View a larger version
of this image.
|
|
|
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.
View a larger version
of this image.
PAGE
4 >
|
|
 |
