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Researchers push transmission rate of copper = cables

Science=20 Centric
=E2=80=94 14 November 2007 | 16:58 GMT

You may not be able to get blood out of a turnip, but = according to=20 Penn State engineers, you can increase the data transmission of = Category-7=20 copper cables used to connect computers to each other and the=20 Internet.

=E2=80=98Working with NEXANS, the company that manufactures the = cable, we have=20 examined the possibility of sending digital data at a rate of 100 = gigabits=20 per second over 100 meters of Category-7 copper cable,=E2=80=99 = says Mohsen=20 Kavehrad, the W.L. Weiss Endowed Chair professor of electrical=20 engineering. =E2=80=98These are the current, new generation of = Ethernet=20 cables.=E2=80=99

These cables are used to connect computers within a room or a = building=20 or to create parallel computing systems.

While the long distance lines of most Internet systems are = glass fiber=20 optic cables, which are very fast, copper cable is generally used = for=20 short distances. =E2=80=98In home networks, for example, it is = expensive to use=20 fiber optic cabling,=E2=80=99 says Ali Enteshari, graduate student = in electrical=20 engineering who presented the team=E2=80=99s methods to the IEEE = High Speed Study=20 Group today (14 November) in Atlanta.

All transmission cables are limited by the distance they can = transmit=20 data without degradation of the signal. Before errors and = interference=20 make the signals non-recoverable, cable systems use repeaters = =E2=80=94 which are=20 similar to computer modems =E2=80=94 to capture, correct or = recover data, and=20 resend it. The distance between repeaters depends on the cable and = the=20 approach used by the modem to correct errors.

=E2=80=98What we are offering is a less expensive solution and = one that is=20 easier to build,=E2=80=99 says Jarir Fadlullah, graduate student = in electrical=20 engineering.

Using information on specifications and characteristics of the = cables=20 from NEXANS, the researchers modelled the cable with all its = attributes=20 including modelling crosstalk. They then designed a = transmitter/receiver=20 equipped with an interference canceller that could transfer up to = 100=20 gigabits using error correcting and equalising approaches. = Ethernet cable=20 like the Category 7 is made up of four pairs of twisted wires = shielded to=20 reduce crosstalk. Category 7 is heavier weight wire with better = shielding=20 than Category 5 cable. Kavehrad=E2=80=99s group did similar = analysis on the=20 Category 5 cables in 2003.

=E2=80=98A rate of 100 gigabit over 70 meters is definitely = possible, and we=20 are working on extending that to 100 meters, or about 328 = feet,=E2=80=99 says=20 Enteshari. =E2=80=98However, the design of a 100 gigabit modem = might not be=20 physically realisable at this time as it is technology limited. We = are=20 providing a roadmap to design a high speed modem for 100 = gigabits.=E2=80=99

The researchers believe that two or three generations in the = future,=20 the technology of chip circuitry will allow these modem designs to = be=20 built. Currently, chip design is at about 65 nanometers, but they = expect=20 in the next two generations to get to what is required, says = Kavehrad.

The amount of data encompassed by 100 gigabits is amazing. The = entire=20 Encyclopaedia Britannica contains 1 gigabyte of information. A = byte is=20 equivalent to 8 bits, so 1 Gigabyte is equal to 8 gigabits. A rate = of 100=20 gigabits per second over 100 meters is the transmission of 12.5=20 Encyclopaedia Britannica sets per second.

Source: Penn = State

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