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The Cat 6 advantage

Those still playing the 'Category 6 waiting game' should take a good look at the benefits the cabling provides.

September 1, 2001  

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During this scorching time of year, it seems fitting to write about a “hot” topic. And as few topics are hotter than Category 6 cabling, I thought I would use this space to clarify some of the perceptions out there about Category 6.

PERCEPTION NO. 1 – Category 6 is still a long way off from being a standard. Why should I install a Category 6 system today before a standard is published? If I install it today, I risk having a non-compliant system.

There is talk in the media that the cabling manufacturers can’t seem to agree on the parameters for a Category 6 cabling standard. This is an exaggeration. What we are still discussing are the component values that are required to ensure that Category 6 components are interoperable between different vendors.

The most important point for the end user is that the ‘end-to-end’ parameters currently specified for a Category 6 Channel (SP-3727-AD1 Draft 9) will not change to any significant extent from now until the time that the TIA standard is eventually published.

PERCEPTION NO. 2 – Category 5e is sufficient to meet my existing application requirements including Gigabit Ethernet (1000BASE-T). What are the benefits of installing Category 6 cabling?

This is a very good question and one that is prevalent in the industry. The situation today is similar to that of 10 years ago when 10BASE-T Ethernet was first introduced over the installed base of Category 3 cabling. Today, Category 5 is the new installed base and Category 5e is recommended as a minimum for new installations to meet the more stringent demands for 1000BASE-T. It does not, however, leave much headroom for more demanding applications in the future.


To compare the benefits of Category 6 and Category 5e, I generated two key charts based on channel performance. The first chart shows the Signal-to-Noise Ratio (SNR) over the frequency band from 1 MHz to 200 MHz. The SNR is the difference in dB between the signal power and the total noise power at the receiver. At 100 MHz, the improvement in SNR performance is 12 dB, or 16 times better than Category 5e. This means more reliable transmission, fewer errors and higher data rate throughput for existing applications. It also means a higher performance margin against unpredictable variations such as external noise sources and transceiver impairments.

The second chart shows the Information capacity in Mb/s as a function of the Bandwidth in MHz. In deriving this relationship it was assumed that in practice, the information capacity is about 50 per cent of the Shannon limit (the theoretical maximum for any channel). As seen in Figure 2, a Category 6 channel effectively doubles the information capacity compared to Category 5e.


So is there any reason to put off the decision to install a Category 6 system today? There is no technical reason based on channel performance. The performance of a Category 6 channel can be readily verified in the field today and is unlikely to change.

Is there any value in installing a Category 6 system? The value can be measured in terms of network performance and data throughput.

A good analogy might be to compare your cabling system installation to the installation of a plumbing system in your home. You could install either 1/2-inch pipe or the larger capacity 3/4-inch pipe. Although the plumbing will work with 1/2-inch pipe, the 3/4-inch choice will certainly serve you better on the occasion when you are in the shower and someone turns on the washing machine! Like the plumbing in your home, your data network must have the reserve capacity to meat the peak demand without a drop in performance.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.

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