This new standard was developed in
order to support the more rigorous demands of Gigabit Ethernet
but because of its improved signal-to-noise ratio all networks
perform better because of the maximized throughput it provides.
The current standard, 568-B.2, requires the use of Category 5e
cabling and for good reason too. It meets the extra performance
requirements that not only double its usable bandwidth but also
reduce the noise level, making the data signal more easily detected
at the receiving end. TIA / EIA has relegated Category 5 cabling
to "legacy" status and no longer supports its use in
for Enhanced Category 5e cables were clearly defined by the TIA
with the publication last November of the 5th addendum
to TIA 569A, known as ANSI/TIA/EIA – 568-A-5. This specification
was driven by the need to support higher performance / higher
speed LAN systems, specifically Gigabit Ethernet.
TIA 568-A-5 adjusts an existing characteristic,
Near-End Crosstalk (NEXT) so that it is 3 dB more stringent than
before. This increases the attenuation to crosstalk ratio (ACR)
of cable, effectively reducing the noise level and making the
data signal easily detected at the receiving end.
The addendum also adds several other characteristics.
These are Equal Level Far End Crosstalk (ELFEXT), Power Sum ElFEXT
)PSELFEXT), Power Sum NEXT (PSNEXT), and Return Loss.
While all of the aforementioned characteristics
have a role in defining the performance of the cable, it’s Headroom,
(or ACR/PSACR margin over spec.) that defines how high the signal
level is relative to the noise level and thus provides the simplest
measure of how well the cable will provide a strong signal profile.
With good Return Loss values, the cable is reducing
signal reflections that result in a attenuation of the signal
and cause echoes that become noise. As with ACR, good RL values
mean a very robust signal compared to noise.