Navy lab: 'I want my HDTV'

At the recent ComNet trade show in Washington, Fore Systems Inc. of Warrendale, Pa.,
and the Naval Research Laboratory transmitted live, high-definition television images via
asynchronous transfer mode switches.


The demonstration network that carried the images between Washington and Newport News,
Va., consisted of commercial products and prototype technologies developed with federal
funding.


NRL helped show off the high-resolution pictures because it hopes to use HDTV
networking for military purposes, NRL electronics engineer Basil A. Decina said.


“We are trying to seed R&D efforts in industry and have them turned into
products,” Decina said. “We have to buy off-the-shelf gear, and, if we can
affect the market, it will help us.”


The HDTV pictures delivered twice the resolution of a standard broadcast picture by
refreshing every horizontal line 60 times per second. In a standard television picture,
only alternating lines are refreshed for an overall rate of 30 new frames per second.
Industry standards exist for broadcast HDTV, but very little receiving equipment has sold
and few commercial broadcasts have been made.


NRL demonstration that streamed HDTV over an ATM network was an entirely new use. Key
to the demo was a prototype video network access unit (VNAU) developed by Tektronix Inc.
of Wilsonville, Ore., with help from the National Institute for Standards and Technology.
NIST officials saw the VNAU in September. The ComNet demo was the first to use a public
network.


Tektronix is still evaluating the VNAU’s commercial potential, product manager
George Pubanz said.


Also part of the demo were HDTV video cameras made by Philips Electronics North America
Corp. of Knoxville, Tenn., developed with funding from NASA and the Defense Advanced
Research Projects Agency.


The cameras were set up over Reagan Washington National Airport and on an airship above
the harbor at Newport News. The camera signals fed into a VNAU box, which converted them
for network transport.


The 720 horizontal and 1,280 vertical video lines generated a 1.5-Gbps data stream that
traveled via DARPA’s Advanced Technology Demonstration Network, a Synchronous Optical
Network OC-48 ATM test bed, into a Fore Systems ASX-4000 switch at NRL in Washington. The
switch, developed with DARPA funding, passed the signal to a GigaMux dense-wave-division
multiplexer from Osicom Technologies Inc. of Santa Monica, Calif.


The GigaMux can transport up to 80 Gbps in 32 optical channels over a single optical
fiber.


The HDTV signal made repeated trips in three wavelength channels over a fiber network
provided by Bell Atlantic Corp., traveling 460 kilometers before an ASX-4000 switch at
ComNet sent it to another VNAU, which reconverted it for two HDTV monitors at Fore
Systems’ booth.


The demonstration used no signal compression. If such a setup were commercially
available, Decina said, the military might use it for surveillance, training and
simulations.  





About the Author

William Jackson is a Maryland-based freelance writer.

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