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DAILY NEWS AND INFORMATION
FOR THE GLOBAL GRID COMMUNITY /
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Breaking News -
Networking:
Copper Wire Competitive With Fiber
Optic Cable For LANS
Penn State engineers have developed and simulation tested a copper wire
transmission scheme for distributing a broadband signal over local area
networks (LANS) with a lower average bit error rate than fiber optic cable
that is 10 times more expensive.
Dr. Mohsen Kavehrad, the W. L. Weiss professor of electrical engineering
and
director of the Center for Information and Communications Technology Research
who led the study, said, "Using copper wire is much cheaper than fiber optic
cable and, often, the wire is already in place. Our approach can improve the
capability of existing local area networks and shows that copper is a
competitor for new installations in the niche LAN market."
Kavehrad presented the Penn State team's results in a paper, 10Gbps
Transmission over Standard Category-5, 5E, 6 Copper Cables, Dec.4 at the IEEE
GLOBCOM Conference. His co-authors are: Dr. John F. Doherty, associate
professor of electrical engineering; Jun Ho Jeong, doctoral candidate in
electrical engineering; Arnab Roy, a master's candidate in electrical
engineering; and Gaurav Malhotra, a master's candidate in electrical
engineering.
The Penn State approach responds to the IEEE challenge to specify a
signaling
scheme for a next generation broadband copper Ethernet network capable of
carrying broadband signals of 10 gigabits per second. Currently, the IEEE
standard carries one gigabit over 100 meters of category 5 copper wire which
has four twisted pairs of wire in each cable.
"In the existing copper gigabit systems, each pair of wires carries 250
megabits per second. For a 10 gigabit system, each pair will have to carry 2.5
gigabits per sec," Kavehrad explained. "At these higher speeds, some energy
penetrates into the other wires and produces crosstalk."
The Penn State scheme eliminates crosstalk by using a new error correction
method they developed that jointly codes and decodes the signal and, in
decoding, corrects the errors.
Kavehrad said, "Conventional wisdom says you should deal with the wire
pairs
one pair at a time but we look at them jointly. We use the fact that we know
what signal is causing the crosstalk interference because it is the strongest
signal on one of the wires." The Penn State approach also takes account of the
reduction or loss of signal energy between one end of the cable and the other
that can become severe in 100 meter copper systems.
"We jointly code and decode the signals in an iterative fashion and, at the
same time, we equalize the signals," added the Penn State researcher. "The new
error correction approach acts like a vacuum cleaner where you first go over
the rough spots and then go back again to pick up more particles."
A MATLAB simulation has shown that the scheme is possible and can achieve
an
average bit error rate of 10 to the minus 12 bits per second. Fiber optic
cable typically achieves 10 to the minus nine. The work is continuing.
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