|
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, says, "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, at the IEEE GLOBCOM
Conference in San Francisco, Calif., Thursday, Dec. 4. 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 explains. "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 says, "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," adds 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.
The project receives support from Cisco, Tyco, Nexan and
the International Copper Association.
Weitere Informationen finden Sie im WWW:
| 