IEEE 10GBASE-T Task Force Approved

The demand for higher data rates and faster applications over cost-effective unshielded twisted-pair cabling continues. And solutions being formatted by the IEEE 802.3 committee will have a major impact on the way customers think about and plan networks.

At the IEEE 802 Plenary Meeting last November in Albuquerque, N.M., the IEEE 802.3 10GBASE-T study group presented a new project proposal consisting of a PAR (project authorization request) and five criteria to develop a new Ethernet standard for transporting 10 Gigabits per second (Gb/s) over balanced twisted-pair copper cabling. This proposal was approved by the IEEE 802.3 working group and the IEEE 802 plenary and is currently in the final stages of being approved by the IEEE standards executive committee. Meanwhile, the 10GBASE-T members conducted an interim meeting in January in Vancouver, British Columbia, and are on track to develop a first draft of the technical specification by this summer. The standard will cover UTP cabling of distances up to 100 meters.

Technical challenges

Delivering 10 Gb/s over balanced twisted-pair cabling, originally designed to support voice applications, is no easy task. Several 10GBASE-T task force members have done multiple simulations using various protocols, signal processing and noise cancellation schemes to establish the feasibility. The objective is to develop the application to work over 55 to 100 meters of Class E (category 6) cable and 100 meters of Class F (category 7) cable.

After considerable modeling, the study group determined that they could support the transfer of high-speed data over at least 55 meters of existing category 6 cabling. This number is based on achieving the desired signal-to-noise ratio at the receiver to ensure a bit error rate of 10 (-12). Depending on the individual installation, this distance can increase.

However, to support a 100-meter channel with four connections, an enhanced category 6 system is needed. Fortunately, a standard to support such a notion is under development. Both Class E and Class F networks will require extensive digital signal processing (DSP) to reduce the noise from adjacent pairs—NEXT and ELFEXT, for example—backward reflection or echo (return loss) and signal reconstruction or equalization at the receiver (insertion loss). DSP, as a result, will be two to three times as complex.

Cabling standards update

The cabling standards committees are scrambling to develop additional requirements and test procedures needed to support the 10GBASE-T application. At the January meeting, the committee agreed to use the equations for the existing category 6, but extrapolated to 625 Mhz. The cabling committees are developing test procedures and fixtures that can measure cabling and components out to 625 MHz. Additionally, 10GBASE-T requires measures to prevent ANEXT, or Alien Cross Talk, the noise source from adjacent cables. This noise source from adjacent cables, however, cannot be cancelled effectively by DSP. The solution is to provide increased isolation of cables from one another either by increased separation, use of shielding, or improved cable constructions that reduce ANEXT.

Projects have been started in the Telecommunications Industry Assn. and the International Organization for Standardization to improve the Alien NEXT of Class E/category 6 cables so that this enhanced category 6 cabling can support 10GBASE-T up to the full 100 meters with four connections.

Customer impact and choices

The 10-Gb/s application will have a major impact on the way customers think and plan enterprise networks. To optimize costs, Class E/category 6 cabling continues to be the best choice to support the IEEE 10GBASE-T for at least 55 meters. In the future, augmented category 6 with improved Alien NEXT performance, and transmission specified up to 625 MHz, will become the recommended choice to ensure robust and reliable performance up to 100 meters.

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