The publication of the Category 6 standard is upon us. Here is a look at what has been achieved so far -- and what has yet to be accomplished.
May 1, 2001
As the Category 6 standard nears publication, it seems timely to provide an update on the development of the Category 6 standard within the Telecommunications Industry Association (TIA) TR-42.7 subcommittee.
The Category 6 standard will eventually be published as an Addendum to the TIA/EIA 568-B standard. The most recent document is Draft 8 and is currently being circulated for an industry ballot. Many of the technical issues have already been resolved, and I can honestly say that we are in the final stretch towards completing the document.
The work on the Category 6 standard started at the end of 1997. The original objective of Category 6 cabling was to provide an available bandwidth of at least twice that of Category 5/5e cabling. That objective still remains, and has been achieved within the parameters currently specified for a Category 6 channel, including a worst-case configuration with four connectors at a maximum distance of 100 meters.
The key parameters specified for Category 6 are Insertion Loss, Insertion Loss Deviation, Return Loss, Power Sum Near End Crosstalk, Power Sum Far End Crosstalk and Delay Skew. All of these parameters are specified over a swept frequency range from 1 MHz up to 250 MHz for connectors, cable, permanent link and channel. In addition, a new parameter called Longitudinal Conversion Loss (LCL) is specified for connecting hardware. LCL relates to the balance of a pair of conductors with respect to the surrounding conductors and the reference ground. It is an important parameter in consideration of electromagnetic interference and noise immunity. A similar parameter for cables is currently being studied.
The TR-42.7 subcommittee has reached agreement on the requirements for a permanent link and a channel — these have been stable for some time. What is still being discussed is the allowance for component impedance mismatch effects, namely the Insertion Loss Deviation (ILD).
There is also still a lot of discussion on the test methods and test requirements for connecting hardware to ensure backward compatibility and interoperability. By backwards compatibility, I mean that any Category 6 component, such as a patch cord or a connector, can be substituted in a Category 5/5e channel and achieve a minimum Category 5/5e performance. By interoperability, I mean that when any Category 6 component (such as a patch cord from one vender) is mated with another Category 6 component (such as an 8-pin modular jack from a different vendor), it will be compliant to the Category 6 specification. Interoperability is more difficult to achieve, since connecting hardware of different designs exhibit different behaviour, depending on the plug that is used to establish a connection.
In fact, most of the effort within the past year has been carried out by a group of experts that participate in the de-embedded task group. This group has been looking at the accuracy and methodology for measuring crosstalk performance of test plugs that are used for qualifying Category 6 connecting hardware performance. There have been two intensive face-to-face meetings of this task group to reduce the variability and to complete all of the fine points of the measurement procedure. In the most current draft, significant progress was achieved to eliminate many TBDs (to be determined) values that can hold up the standard from being issued.
NEARING THE END
We are now in the home stretch — the final stages before the Category 6 standard is published. It is anticipated that there will be at least one more ballot cycle. That would optimistically mean that the Category 6 standard could be approved at the TIA meeting in August of this year.
When approval is reached, it will open the door to future applications that can take advantage of the additional bandwidth and the improved signal-to-noise ratio of Category 6 cabling. One such application has already been approved by TIA TR-41.5, which implements a Physical Media Dependent (PMD) specification for 1000BASE-TX using simpler electronics.CS
Paul Kish is Director of IBDN Systems & Standards at NORDX/CDT in Pointe Claire, PQ. He is also Chair of the TR-42 engineering committee.
Disclaimer: The information presented is the author’s view and is not official TIA correspondence.