Tài liệu On Data Throughput in Structured Cabling Systems pptx

ZERO BIT ERROR RATE
On Data Throughput
in Structured Cabling Systems
Released by KRONE Australia
Asia Pacific Test Laboratory
(Certified by Underwriters Laboratories)
February, 2001
WHITE PAPER
More and more network managers are demanding
that their networks operate to their maximum
potential, rather than merely operate as a standards-
compliant solution. Downtime or a slowdown in
network performance can be crippling to an
organisation in today’s global e-commerce
environment.
The network cabling infrastructure must be able to
support an enterprise’s increasing rates of data
transmission now and in the future. It’s imperative
that mission-critical information which is transmitted in
packages of bits is delivered immediately, without
costly delays. Bit Error Rate (BER) testing is one way of
measuring a network’s performance - of seeing how
quickly and efficiently information is delivered from
sender to receiver. Zero Bit Error Rate (ZBER) has been
the goal that now is a practical reality, thanks to
KRONE’s TrueNet solution.
However, controversy reigns in the cabling industry
today disputing the ability to actually measure an
absolute zero. Amid claims that ZBER is no more than
a new buzz-acronym and, therefore, cannot be
achieved, this White Paper outlines KRONE’s

methodology of testing for, achieving and, indeed,
guaranteeing Zero Bit Error Rate.
WHAT THE STANDARDS SAY
The IEEE 802.3 Standard defines the lowest acceptable
value for Bit Error Rate (BER) for 1000 Base-T as being
10
-
10
. This BER limit is set for levels of line encoding
using pulse amplitude modulation (PAM-5). This is the
encoding scheme for Gigabit Ethernet.
WHAT IS BER?
A bit error occurs when the transmitted signal is
corrupted by an event which changes the voltage level
of the signal. Events such as noise, impulses due to
switching surge or lightning, transmission equipment
fault plus others can all cause a bit error (eg. it is the
reception of 0 when 1 was transmitted or vice versa).
The Bit Error Rate (BER) is a measure of how often
these errors occur.
Statistical Method
Some measurement techniques are based on statistical
analysis which predict the number of bit errors with a
certain degree of accuracy using common statistical
distribution methods. For example:
Pb(e) is bit error probability which equals BER.
P(e) is the probability that a waveform is detected
incorrectly.
M is the number of discrete signal levels (eg 3 for
PAM-3, 5 for PAM-5).

Practical Method
Although KRONE uses both statistical and practical
methods, we put more emphasis on
the measurement of real errors as a way of
understanding the nature of an error. Any modern
LAN hardware and network analysis software can
perform this real physical measurement.
Practical measurement techniques use the cyclic
redundancy check (CRC) to determine actual bit error
failures in any period of time.
For example, there may be two CRC failures after
running a system using PAM-5 encoding for, say, 100
hours. CRC uses a frame check sequence, developed
by the transmitter, that is checked by the receiver to
see if it is valid or not. If it is not valid, because at
least one bit contains an error, the receiver rejects the
ZERO BIT ERROR RATE
Cabling infrastructure providers are following KRONE’s lead regarding the
importance of having the lowest bit error rate possible. This white paper confirms
that zero bit error rate is a practical reality that Network managers can rely on.
P (e)_
Log
2
M
< Pb (e) < P (e)
whole packet of data that may contain up to 1500
bytes x 8 bits = 12,000 bits for an Ethernet Frame.
This means that one bit error can cause up to 12,000
bits to be re-transmitted.
WHAT IS A ZERO BIT ERROR RATE?

IEEE 802.3 defines the occurrence of errors at 10-
10
as
being its worst case. At this condition any bit errors
which may exist do not degrade the performance of
the network because all network hardware and
software is built to meet this condition. Therefore, any
noise present at this condition will be insufficient to
alter the bit value at the receiver and cause an error.
KRONE has selected a level 100 times lower than the
worst case in the Standard and has called this BER
condition of 10-
12
as ZERO BIT ERROR RATE.
Zero Bit Error Rate (ZBER) means less than one error in
a million-million bits.
WHAT KRONE DOES
In-House Testing
We consider field network testing to be the most
accurate way to correlate theoretical base to real world
performance. To do this, we measure the product
performance in the laboratory under severe noise
conditions (simulating worst case real life environment)
and then we test the installed cabling systems at the
customer’s site to verify the laboratory performance in
no-load and live network conditions (eg the network is
fully functional).
When testing, KRONE uses the latest test technologies
and the most sophisticated digital measurement
equipment available on the market such as Netcom

Systems Smartbits SMB-2000, Vigilant Big Tangerine,
and Fluke DSP 4000. These tools are recognised as
the best by all international test laboratories such as
The Tolly Group, BiCSi, Bell Laboratories, etc.
In the example below, KRONE used Smartbits SMB-
2000 Signal Generators generating up to
19 Gigabits of continuous traffic in both directions at
once. A Pentium 200MHz laptop computer was used
to monitor the traffic for four days while the site was
influenced by neighbouring external noise sources.
There were zero delivery errors.
KRONE went even further, analysing network latency
using advanced Netcom SmartFlow v. 1.14 network
analysis software generating different groups
of data streams.
The results showed that during the tests no frames were
lost on KRONE’s TrueNet
™
cabling system.
Field Testing
For field testing of commercial and industrial sites,
KRONE uses an advanced 24-port Vigilant Network
Monitor to evaluate the health and integrity of a
customer’s structured cabling system on a
continuous basis. From this testing, measurements
of impedance versus distance and frequency are
made, finding the impedance mismatches and
discontinuities in a network channel that cause
network traffic to slow down.
We found that impedance mismatch was the main

factor that caused performance loss in
Test 1 Test 2 Test 3
Gigabit Card No 01 GX-1420B 01 GX-1420B 01 GX-1420B
Tx Frames 237,644,979 13,115,406 11,393,017
Rx Frames 233,998,500 12,648,131 11,631,058
Rx Bits 14,975,904,000 19,199,862,858 17,655,946,044
Rx Triggers 0 0 0
CRC Errors 0 0 0
Over Size 0 0 0
Frag/Under Size 0 0 0
BER 000
TrueNet C6T
KRONE Platinum Solution
a structured cabling system. TIA/EAI-568A standard
specifies the impedance variation to be +/-15 Ohms
but KRONE’s TrueNet
™
Cabling System goes even
further, restricting it to
±
3 Ohms.
The test equipment captures noise, interference and
cross-talk events in the network and analyses the
effect they have on performance. From these
measure-ments we have been able to verify that
correctly installed TrueNet
™
Cabling Systems have
impedance which is within
±

3 Ohms throughout
the cabling channel.
The graph below shows test results from a TrueNet
cable run in a customer’s structured cabling system.
Most impedance mismatch problems happen in the
cross-connect patch cord in the closet, the
consolidation point, and the connectors at the
telecommunications outlet. The first few metres on
the graph relate to the temporary use of the
injecting patch cord - which is the connection
between the tester and the cable run. The rest of
the graph shows that the cable run and all
components are within
±
3 Ohms resulting in
negligible impedance mismatches that will not
cause bit errors and thereby data retransmissions.
THE RESULT
Both in-house testing and on-site testing confirm
KRONE’s technical approach to proving the feasibility
of achieving Zero Bit Error Rates is correct. More
importantly, KRONE customers confirm that Zero Bit
Error Rates are achievable on their installed sites.
Because KRONE components are tuned to remove
impedance mismatches, the TrueNet
™
Cabling System
does perform with a bit error rate lower than 10-
12
.

This well exceeds the standards requirements of 10-
10
.
Therefore, KRONE can offer a 5-year “ZBER”
throughput warranty to sites that install
a KRONE TrueNet
™
structured cabling system.
For further information please contact:
KRONE (Australia) Holdings Pty Limited
PO Box 335, Wyong NSW 2259
2 Hereford Street, Berkeley Vale NSW 2261
Tel: 02 4388 4422
Fax: 02 4388 4499
Email:
Web: www.krone.com.au
5549 10/01
KRONE (N.Z.) Technique Limited
PO Box 38-177
Wellington Mail Centre
Wellington, New Zealand
Tel: 0800 657 663
Fax: 0800 355 100
Email:
Berkeley Vale, Australia
February, 2001
By
Boris Torban Peter Meijer
Telecommunications Engineer Technical Training Manager
KRONE (Australia) Holdings Pty Limited KRONE (Australia) Holdings Pty Limited

Injecting
patchcord Cable run