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A Cat 6 Primer

It has many common features with Category 5/5e ... and also notable differences.


September 1, 2002  


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After a long time in the making, the Category 6 cabling standard was published as TIA/EIA-568-B.2-1 (Addendum No. 1 to ANSI/TIA/EIA-568-B.2) in June. Now that the standard is a reality, it is normal to ask questions about Category 6 cabling, how is it different from Category 5 / 5e cabling and what is the significance to the industry?

WHAT IS CAT 6?

From the outside, Category 6 components may not look much different than Category 5/ 5e; but it is what is on the inside that makes the difference. Category 6 has many features in common with Category 5 / 5e and some notable differences.

First of all, Category 6 components are specified to be interoperable between different vendor’s products and are fully backward compatible with all lower categories. Although it seems obvious in today’s world of ‘open architectures,’ these concepts presented significant challenges for both TIA and the manufacturers alike.

Like most good things, these features were not easy to create, but worth the benefits that they bring to the end-user community.

Second, all Category 6 components have the same Impedance of 100 Ohms as Category 5 and 5e components, but have a tighter tolerance on Impedance variations. As a result, Category 6 provides better Bit Error Rate (BER) performance.

Fewer bit errors means that your network is accurately and rapidly transferring the information that drives your business and improves productivity.

Third, all the transmission parameters for Category 6 channels, permanent links and components are specified up to 250 MHz compared to 100 MHz for Category 5 and 5e. Category 6 systems deliver a bandwidth of 200 MHz compared to a bandwidth of 100 MHz for Category 5 / 5e.

WILL IT SUPERCEDE CAT 5 / 5E?

The answer is yes; it is only a question of when. Today, the choice for Category 6 tends to be an economic one. Like most newly introduced technologies, Category 6 systems currently command a price premium in the market. Experience tells us that prices will decrease over time as acceptance and volume increases. Regardless of traditional technology life-cycle pricing, the benefits of Category 6 in terms of bandwidth, performance headroom, reliability and application support, need to be weighed against end user needs, planning horizon and budgetary constraints.

DOES IT DELIVER WHAT IS PROMISED?

Again, the answer is ‘yes.’ There are no technical obstacles in the way. What took so long in completing the standard was the development of the test parameters and the test procedures that are used to qualify Category 6 components to ensure interoperability between different vendor’s products.

These specifications are in place and very much detailed. Category 6 connecting hardware needs to be qualified with a range of “high” and “low” test plugs that simulate worst case variations in the field.

WHAT ABOUT NETWORK PERFORMANCE?

Whether Cat 6 or Cat5/5e, network performance effectively boils down to Signal-to-Noise Ratio at the Receiver. Both internal and external noise sources need to be taken into account. The biggest benefit of Category 6 cabling is the much-improved Signal-to-Noise Ratio (SNR).

The net result is that Category 6 provides about 12 dB (or 16 times) better Signal-to-Noise Ratio compared to Category 5 / 5e over a wide frequency range.

For today’s applications, there has been some work done by others that indicates Category 6 provides higher Data Throughput (fewer bit errors) than Category 5e for 100BASE-TX and 1000BASE-T applications.

For future applications, Category 6 is well positioned to support more demanding applications such as multi-channel broadband video with an extended frequency range up to 550 MHz and digital video signals as high as 2 Gb/s for HDTV and future multi-Gigabit applications.

Also, the new IEEE standards for remote powering of DTE equipment would be better served with Category 6 cabling because of the lower power dissipation for Category 6 cables and the improved balance recommendations for Category 6 components.

CONCLUSIONS

The key difference is in performance. Category 6 cabling provides twice the Bandwidth (200 MHz) and 16 times (12 dB) better than Signal-to-Noise margins compared with Category 5e cabling. These additional performance margins compensate for deficiencies in the equipment and external noise and temperature variations in the environment. hey also provide the roadway to support more demanding applications in the future.

Paul Kish is Director of IBDN Systems & Standards at NORDVCDT in Pointe Claire, Que. He is also Vice-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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