23
WIRELESS TECHNOLOGY
By Gianluca Musetti, Specification
Sales Engineer, Leviton Network
Solutions
Higher performance networks and greater bandwidth
that can meet growing wireless data needs are
essential for everyone
www.leviton.com
This option is ideal for networks that anticipate a moderate
increase in bandwidth demand. It can also be useful for
facilities needing a short-term, easily adopted solution
that provides greater bandwidth until a full infrastructure
upgrade can be implemented. In either case, additional
considerations should be taken prior to deployment.
Alien Crosstalk
Since Cat 5e/Class D and Cat 6/Class E are designed to
support 1000BASE-T, alien crosstalk (AXT) is not typically
specified. When running higher data rates over existing Cat
5e/Class D and Cat 6/Class E cabling, AXT may become
an issue, especially for longer cable runs with significant
bundled cable lengths. AXT limits are not directly specified
for 2.5GBASE-T or 5GBASE-T. However, Alien Limited Signal-
to-Noise Ratio (ALSNR) or exogenous Signal-to-Noise ratio
as mentioned in ISO/IEC — a new measure based on AXT,
attenuation, and other factors — was developed to assess
a channel’s susceptibility to AXT, as well as its ability to
support 2.5 Gb/s and 5 Gb/s speeds. A recent risk assessment
of ALSNR testing, as noted in Tables 1 and 2, shows there is a
medium to high risk for Cat 5e and Cat 6 infrastructures not
meeting the ALSNR requirement at longer channel lengths.
Tables 1 and 2 are based on modelling, testing, and the
ALSNR calculation included in TSB-5021. They indicate typical
risks associated when a 2.5 Gb/s or 5 Gb/s system is not
operating correctly for a Cat 5e or Cat 6 channel, given overall
channel length and bundled length of cable in the channel.
Generally, the longer the overall channel length and the
more bundled length of cable in the channel (shown as Victim
Length in the tables), the greater the risk. Cat 6 poses less
risk than Cat 5e; using either for 5 Gb/s poses more risk than
2.5 Gb/s. For example, a 100m Cat 5e channel with 75m of
bundled cable poses a high risk of not performing correctly for
5 Gb/s. A 75-metre Cat 6 channel with 20m of bundled cable
poses only a negligible risk when used for 2.5 Gb/s. There is no
risk when using Cat 6A, as shown in Table 3.
If a channel fails to operate correctly for the application
intended, field testing and mitigation steps may be required.
This can include anything from separating a limited amount
of existing cables up to and including replacement of all
channel components (cable and jacks) with Cat 6A. For these
reasons, upfront replacement/upgrade of links to Cat 6A and
running dedicated 10 Gb/s active equipment may be the
lowest cost solution for large networks and networks with
links greater than 50m. This alternative can be cost modelled
before making a final decision.
Power over Ethernet
For most enterprise applications, Power over Ethernet (PoE)
remains a convenient method for powering network devices,
especially wireless access points (WAP). Approximately 18
million PoE enabled access points ship annually, and that
number is expected to increase to 25 million by 2020. This
increase in access point PoE consumption directly correlates
with a greater need for more cabling. Additional cabling can
create issues with regards to heat generation/dissipation. To
offset these issues, a larger gauge size is required.
Experiments with new and future iterations of IEEE
PoE systems, including power up to 200 watts have been
conducted. During these tests, it was found that there are
significant differences in temperature increases between
Category 5e, 6, and 6A.
Existing Cat 5e or Cat 6 cabling can, in many instances,
support 2.5GBASE-T and 5GBASE-T in regards to transmission
performance. However, because of the technical designs
implemented to support higher speeds, newer WAPs require
more power and generate more heat. Traditional Cat 5e and
Cat 6 cables generate more heat than Cat 6A. When used in
large bundles, the cable’s temperature could increase enough
to significantly impact performance and in some cases,
exceed the temperature rating of the cable.
Wireless demand
The biggest driving factor for 2.5 Gb/s and 5 Gb/s deployment
is also its greatest challenge. The bandwidth demand for
Table 1: Category 5e Alien Limited SNR Risk Matrix
CATEGORY 5E
Bundled distance up to 20m
Bundled distance up to 20m - 75m
Bundled distance up to 75m - 100m
VICTIM LENGTH
SPEED
1m - 20m 20m - 75m 75m - 100m
2.5 Gb/s Negligible Negligible Negligible
5 Gb/s Negligible Negligible Low
2.5 Gb/s N/A Low Medium Low
5 Gb/s N/A Medium Low Medium Low
2.5 Gb/s N/A N/A Medium
5 Gb/s N/A N/A High
Note: Risk refers to risk of bundled cable configurations not
supporting an ALSNR min greater than or equal to 28 dB.
Information gathered from Table 22 of TIA TSB-5021.
HIGH
MEDIUM HIGH
MEDIUM
MEDIUM LOW
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LOW
NEGLIGIBLE