Network Cabling http://www.innovaglobal.com 877-448-4968

The Future of Network Cabling
By Paul Kish, NORDX/CDT
June 2000

Table of Contents

INTRODUCTION ……………………………………………………………………… 2

Gigabit Networking Technology ……………………………………………………. 2

Evolution of Cabling Standards …………………………………………………….. 3

Advances in Cabling Technology ………………………………………………….. 3

Shaping the Future ……………………………………………………………….….. 4

Channel Performance ………………………………………………………………. 5

Signal-to-Noise Ratio due to NEXT and FEXT …………………………………… 6

Bandwidth and Information Capacity ……………………………………………..... 9

Test Results Summary ……………………………………………………………… 11

CONCLUSIONS..…………………………………………………………………….. 14

1

Introduction
A lot has been written recently about better cabling to support gigabit networking.
TIA published a new cabling standard for gigabit networking over copper in
January 2000. It is available through Global Engineering Documents as
Addendum No. 5 (TIA/EIA 568-A-5) to the TIA/EIA 568-A standard. It builds
upon the installed base of Category 5 cabling and is called Category 5e, or
“enhanced Category 5”.

The TIA/EIA Category 5e cabling standard was developed by TIA in harmony
with the IEEE 802.3 committee responsible for the 1000BASE-T Ethernet
standard. It incorporates several new transmission parameters that are required
to support full duplex, parallel transmission systems, namely: Power Sum Near
End Crosstalk (PSNEXT), Power Sum Equal Level Far End Crosstalk
(PSELFEXT) and Return Loss. These are additional transmission parameters
and are intended to complement and not to supercede the transmission
parameters already specified for Category 5 cabling.

I will not spend much time in this paper to explain or define these new
transmission parameters for Category 5e. Rather, the focus of this paper will be
on what’s ahead for the next generation copper cabling standard. What types of
cables and connecting hardware will be required to support the multi-gigabit
applications that are coming in the future? What transmission parameters are
particularly important to system designers of these future networks?

Gigabit Networking Technology
Gigabit networking over copper will employ parallel, full-duplex transmission. For
example, 1000BASE-T will simultaneously transmit and receive 250 Mb/s of
information on each pair of a 4-pair Category 5 channel to achieve an aggregate
data rate of 1000 Mb/s. It will employ a five-level Pulse Amplitude Modulation
(PAM-5) line code for transmission over each cable pair. PAM-5 encodes 2 bits
of information into one symbol. Thus, the actual line rate is 125 Mbaud or 125
Mega-symbols per second, the same as 100BASE-T. This facilitates the
implementation of common circuitry for both 100BASE-TX and 1000BASE-T. In
fact, it is envisaged that a 1000BASE-T network card will support both 100BASE-
TX and 1000BASE-T data connections using an auto-sensing feature. The first
networks based on the new gigabit Ethernet technology over copper became
commercially available in 1999
(see http://www.gigabit-ethernet.org/news/releases/090399.html).

*
TIA/EIA Category 6 working draft 6 (May 2000)

2

Evolution of Cabling Standards
Category 5 cabling has evolved over the last 10 years to become the workhorse
in the industry. Category 5e completes the picture for Category 5 by filling in the
missing pieces that are essential to support advanced networking protocols such
as gigabit Ethernet. Looking back at the evolution of Category 5, Category 5e is
what Category 5 should have been all along once all the pieces had been put
together.

Before the ink is even dry on the Category 5e cabling standard, both TIA and
ISO are already hard at work developing the next generation standard for
Category 6 (UTP/ScTP) and Category 7 (STP) cabling. These new cabling
categories will have an extended bandwidth of at least 200 MHz. It is expected
that the standards for Category 6 and 7 cabling will be approved sometime in the
year 2001. There are many technical issues that are still open. For example,
the issue of interoperability between different vendor’s products and the issue of
backward compatibility with Category 5 and 5e connecting hardware need to be
resolved before a standard can be published. The next generation cabling
standard will also need to set a useful performance benchmark for designers of
future networking applications.

Advances in Cabling Technology
Cabling technology is advancing at a very rapid pace. The cabling industry is
undergoing an exciting phase in the development of a standard for Category 6*.
The door is open to many innovative new product ideas for cables and
connecting hardware. These have resulted in various proposals that are under
consideration by TIA TR 42.7, the Copper Cabling Systems sub-committee. One
such proposal is from NORDX/CDT for an alternate low attenuation Category 6*
cable with improved crosstalk performance.

At NORDX/CDT, we have completed an extensive series of tests in our IBDN
systems laboratory on a variety of channel configurations using a low attenuation
Category 6* cable that incorporates 23 AWG copper conductors a cross-web
separator. Our test results demonstrate that a channel comprised of IBDN
4800LX cable and newly developed PS6LX cords and GigaFlex PS6+
connectivity hardware can provide an available bandwidth of 300 MHz for a
worst case 4-connector topology. This is 50% higher than the objective for a
minimally compliant Category 6* channel (see http://www.beyondcat6.com). The
test results for the new IBDN System 4800LX are presented later in this paper.

One of the transmission parameters of paramount importance for Category 6* is
the channel attenuation. A more correct term would be the channel insertion
loss since insertion loss, by definition, includes the effects of impedance
mismatch between components and cabling terminations. Most people in the

*

3

industry incorrectly use the term attenuation to be synonymous with insertion
loss. The TIA TR 42.7 sub-committee members recognize this inconsistency
and intend to clarify the usage of these terms in future editions of the standard.

The IEEE 802.3 committee responsible for the gigabit Ethernet standard is on
record stating that a 1 dB improvement in cabling attenuation is more valuable to
designers of future systems than a 1 dB improvement in crosstalk performance.
This is because of advances in digital signal processing (DSP) techniques that
can be used to cancel out certain types of correlated noise such as NEXT and
echoes. Therefore, the overriding constraint becomes channel attenuation or
insertion loss as well as insertion loss deviation that is a new parameter under
study for Category 6*. NORDX/CDT understands and openly supports the IEEE
position. It is the basis of our Category 6* cable proposal to the TIA committee.
It is also the cornerstone of our IBDN System 4800LX offering.

Shaping the Future
The IBDN 4800LX Cable from NORDX/CDT sets a new performance benchmark
compared to Category 5 & 5e cables. More detailed information on the cable
construction and performance is presented in a companion article [1 ]. The new
cable provides 4 dB lower attenuation at 100 MHz and at least 6 dB lower
attenuation at 200 MHz. What does this mean to the network system designer?

First, system designers are constrained by the maximum transmit signal that can
be applied at the active equipment interface. This is because of EMC guidelines
for computer equipment and peripherals that limit the radiated emissions above
30 MHz. Typically, the output signal amplitude is constrained to about 1 volt
peak-to-peak (ATM 155) or 2 volts peak-to-peak (100BASE-TX or 1000BASE-T).

Second, system designers are constrained by the minimum level of the receive
signal because of environmental noise and receiver sensitivity. Environmental
noise is principally caused by power line disturbances, RFI, and alien crosstalk
from adjacent cabling. Other sources of noise that must be considered include
thermal noise and stray couplings within the equipment.

The above constraints place an upper bound on the level of the transmit signal
and a lower bound on the level of the receive signal. The difference between
transmit signal output and the receive signal input is the insertion loss of a
channel. Let’s assume that the maximum insertion loss of a channel is limited to
35 dB because of these constraints. This limitation would restrict the applicability
of finer gauge cables at high frequencies and is independent of any other
transmission constraints such as PSACR (Power Sum Attenuation-to-Crosstalk
Ratio).

*
The insertion loss of a channel is particularly important for future applications
that will employ crosstalk cancellation techniques. For such applications,

4

insertion loss, insertion loss deviation and environmental noise are the governing
factors that limit the available bandwidth of a system and not the PSACR.

Channel Performance
The transmission parameters for the IBDN System 4800LX are summarized in
table 1 below. There are major improvements in all the transmission parameters
for the IBDN System 4800LX compared to the Category 5e standard and
Category 6* proposal. The significance of this can be appreciated by looking at
the signal-to-noise ratio (SNR) at the receiver. The signal-to-noise ratio
determines the ultimate information capacity of the channel and the system error
rate performance.

Channel Parameter Category 5e Category 6* IBDN System Comment
4800LX
Insertion Loss @ 100 MHz 24.0 21.3 18.4 The
(dB/100m) @ 200 MHz 35.3 31.5 27.0 lower
@ 300 MHz 39.7 34.1 the better
PSNEXT @ 100 MHz 27.1 37.1 42.0 The
(dB) @ 200 MHz 31.9 37.0 higher
@ 300 MHz 34.2 the better
PSACR @ 100 MHz 3.1 15.8 23.6 The
(dB) @ 200 MHz 0.4 10.0 higher
PSELFEXT @ 100 MHz 14.4 20.3 24.4 The
(dB) @ 200 MHz 14.2 18.4 higher
Return Loss @ 100 MHz 10.0 12.0 12.8 The
(dB) @ 200 MHz 9.0 9.8 higher
Table 1 - Worst case channel performance (4-connector topology)
*

5

Signal-to-Noise Ratio due to NEXT and FEXT
To illustrate the point, I will derive the SNR due to NEXT and FEXT. It may
seem laborious to go through this exercise, however, I have found in discussions
with my colleagues that these concepts are not well understood, particularly as it
relates to PSFEXT and PSELFEXT. Therefore, I feel that going through a
mathematical derivation will help to clarify these concepts.

First, let’s designate the two ends of the channel as end A and end B
respectively. The four pairs will be designated as pair 1,2,3 and 4 respectively.
All values derived in the following expressions are given in decibels (dB).

Tx(4A) Tx(4B)
Hybrid

Hybrid
Tx(3A) Tx(3B)
Hybrid

Tx(2A) Hybrid
Hybrid

Hybrid Tx(2B)

ΣNx(1A) ΣFx(1B)
Hybrid

Hybrid

Tx(1B)

Rx(1A) IL(1)

Figure 1 - Parallel, full duplex transmission using a hybrid coupler

Note: The following derivations do not include the added loss of the hybrid
circuit. The added loss of the hybrids do not affect the SNR due to NEXT and
FEXT since the signal and the noise are attenuated by the same amount.

As illustrated in Figure 1, let us designate the receive signal on pair 1A as
Rx(1A) and the transmit signal at the opposite end of pair 1A as Tx(1B).
By definition, the receive signal is

Rx(1A) = Tx(1B) - IL(1) …………………………….…………………………(1)
*
where,

6

IL(1) is the insertion loss for pair 1, often referred to as attenuation

The Near End Crosstalk noise on pair 1A due to a near-end transmit signal on
pair 2A is

Nx(2A,1A) = Tx(2A) - NEXT(2A,1A) ………….…..…………………………(2)

where,

NEXT(2A,1A) is the NEXT coupling loss between pair 2A and pair 1A

The total Near End Crosstalk noise on pair 1A calculated as a power sum is

ΣNx(1A) = 10*log(10Nx(2A,1A)/10 + 10Nx(3A,1A)/10 +10Nx(4A,1A)/10) ……………(3)
For the purpose of simplifying the equations, let’s assume that all the transmit
signals on all pairs are at the same level at both ends of the channel, i.e.

Tx = Tx(1A)=Tx(2A)=Tx(3A)=Tx(4A)=Tx(1B)=Tx(2B)=Tx(3B)=Tx(4B)

Using this simplification in equation (3), it follows that the total NEXT noise on
pair 1A is

ΣNx(1A) = Tx + 10*log(10-NEXT(2A,1A)/10 + 10-NEXT(3A,1A)/10 +10-NEXT(4A,1A)/10)

ΣNx(1A) = Tx - PSNEXT(1A) ……….………………..………………………..(4)

The signal-to-noise ratio due to NEXT is

SNRNx = Rx(1A) - ΣNx(1A)

SNRNx = Rx(1A) -Tx + PSNEXT(1A)

SNRNx = PSNEXT(1A) - IL(1) ………………….……….……………………(5)

SNRNx = PSACR

The Far End Crosstalk noise on pair 1A due to a far-end transmit signal on pair
2B is
*
Fx(2B,1A) = Tx(2B) - FEXT(2B,1A) …………….…..………………………..(6)

The total Far End Crosstalk noise on pair 1A calculated as a power sum is
7

ΣFx(1A) = 10*log(10Fx(2B,1A)/10 + 10Fx(3B,1A)/10 +10Fx(4B,1A)/10) …..………(7)

If all the transmit signals are at the same level, then the total FEXT noise power
on pair 1A is

ΣFx(1A) = Tx + 10*log(10-FEXT(2B,1A)/10 + 10-FEXT(3B,1A)/10 +10-FEXT(4B,1A)/10)

ΣFx(1A) = Tx - PSFEXT(1A) …………..………………..…………………..(8)
The signal-to-noise ratio due to FEXT is

SNRFx = Rx(1A) - ΣFx(1A)

SNRFx = PSFEXT(1A) - (Tx - Rx(1A))

SNRFx = PSFEXT(1A) - IL(1)……..…..….……………………………(9)

SNRFx = PSELFEXT

Both equation (5) and equation (9) can be used to determine the available
bandwidth of a channel. PSNEXT is usually the dominant noise source at higher
frequencies and determines the available bandwidth. If NEXT and echo
cancellation are used in the active electronics, then PSFEXT and other
environmental noise sources become the governing factors that determine the
bandwidth and the ultimate data rate capability.

From Table 1 above, the signal-to-noise ratio due to PSNEXT (PSACR) for the
IBDN System 4800LX remains positive right up to 300 MHz and establishes the
NEXT limited bandwidth for a worst-case channel configuration. At 200 MHz
there is an additional headroom of 10 dB compared with the current Category 6*
proposal.

PSELFEXT can be considered as the signal-to-noise ratio due to PSFEXT and is
important for networks that employ advanced DSP technology for NEXT
cancellation and echo cancellation. The IBDN System 4800LX provides about
the same PSELFEXT at 300 MHz as the Category 6* proposal at 200 MHz and
Category 5e at 100 MHz. The improved PSELFEXT performance ensures more
*
reliable transmission for today’s applications and additional information capacity
for multi-gigabit applications in the future.

8

Bandwidth and Information Capacity
There is a fundamental relationship between the bandwidth of a channel
expressed in MHz and the information capacity expressed in Mb/s. This
relationship was discovered a long time ago by Claude Shannon in his famous
work published in 1948. The maximum information capacity of a noisy channel
(C) according to Shannon is given by:

SNR

w. log2 1
10
C 10
…………………..…………..…………….(10)

where,
w is the bandwidth

S
SNR 10 . log
N

f0 w
S Signal f) d f
(
f0

f0 w
N Noise( f) d f
f0

Shannon’s equation was used to calculate the maximum information capacity for
Category 5, 5e, 6* and for an IBDN System 4800LX Channel. The data rate
capability relative to Category 5 is shown in Figure 2 and Figure 3. Figure 2
represents the data rate capability for a channel that is limited by power sum
NEXT noise, i.e. SNRNX as given by equation (5). Figure 3 represents the data
rate capability for a channel that is limited by PSFEXT noise, i.e. SNRFX as given
by equation (9) or by the Insertion Loss which is assumed to be 35.3 dB
maximum due to EMC considerations and receiver sensitivity.

Figure 2 below, is applicable for simple electronics. Figure 3 below, is applicable
for sophisticated electronics which uses digital signal processing techniques for
NEXT cancellation.

From Figure 2, an IBDN System 4800LX Channel provides the capability of
supporting almost 2 ½ times the data rate of basic Category 5 for a bandwidth of
100 MHz and up to 4 times the data rate for a bandwidth of 300 MHz. Figure 3
illustrates that it is possible to increase the data rate of a Category 5 channel by
almost 2 times by using sophisticated electronics and an extended bandwidth of
9

200 MHz. The comparable increase with the IBDN System 4800LX is 6 ½ times
for an extended bandwidth of 300 MHz.

Maximum Information Capacity
(PSNEXT limited bandwidth)
450%

400%

350%

300%
P Cat 5
e 250% Cat 5e
r
c 200% Cat 6
e 4800LX
n 150%
t
100%

50%

0%
100 200 300
Bandwidth (MHz)

Figure 2 - Maximum information capacity for a channel limited by PSNEXT

*

10

Maximum Information Capacity
(PSFEXT and Insertion Loss limited bandwidth)
700%
IL = 35.3 dB @ 320 MHz

600%

500%

P IL = 35.3 dB @ 240 MHz
e 400% Cat 5
r Cat 5e
c Cat 6
e 300% 4800LX
n IL = 35.3 dB @ 200 MHz
t
200%

100%

0%
100 200 240 300 320
Bandwidth (MHz)

Figure 3 - Max. info. capacity for a channel limited by PSFEXT & Ins. loss

Test Results Summary
The test results for the IBDN System 4800LX Channel are presented in Figures
5 through 7 for the test configuration shown in Figure 4.

Figure 5 is a plot of the PSNEXT and Insertion loss as a function of frequency.
The two curves intersect at a frequency of about 300 MHz which is the PSNEXT
limited bandwidth for the channel under test. At high frequencies it is observed
that the connector NEXT is the major contributor to the PSNEXT of a channel.
For example, we have noticed a very sharp drop in performance above 200 MHz
for certain designs of proposed Category 6 connecting hardware on the market.
The results obtained for the IBDN System 4800LX Channel are contingent upon
having well behaved connecting hardware with extended performance up to 300
MHz. Another important point is the insertion loss. The relatively smooth
insertion loss traces at frequencies above 100 MHz are contingent upon having
well matched components with good return loss performance.

*
The PSELFEXT results shown in Figure 6 and the Return Loss results shown in
Figure 7 significantly exceed the proposed Category 6* requirements.
11

GigaFlex GigaFlex GigaFlex
PS6+ PS6+ PS6+

Optional CP
PS6LX
Eq. Cbl. Patch Cord 4800LX IBDN cable WA cord

3m ½, 1, 2 & 3m 90m 3m

TC TO
Figure 4 - IBDN System 4800LX Channel Test Configuration

Channel Insertion Loss vs. PSNEXT
(measured from TC)
100

90 PSNEXT Pr 1
PSNEXT Pr 2
80
PSNEXT Pr 3
70
PSNEXT Pr 4

60 Ins. Loss Pr 1

dB Ins. Loss Pr 2
50
Ins. Loss Pr 3
40 Ins. Loss Pr 4

30 Ins. Loss C6a
PSNEXT C6a
20
Ins. Loss C5e
10 300 MHz PSNEXT C5e

0
1 10 100 1000 PS-6
9-Oct-98
Frequency (MHz)

Figure 5 - IBDN System 4800LX [Power Sum NEXT and Insertion Loss Results]
*

12

Channel PSELFEXT

0

-10

-20

-30
PSELFEXT Pr 1
PSELFEXT Pr 2
dB

-40 PSELFEXT Pr 3
PSELFEXT Pr 4
-50 PSELFEXT Cat 6

-60

-70

-80
1 10 100 1000
PS-6
Frequency (MHz) 9-Oct-98

Figure 6 - IBDN System 4800LX [Power Sum ELFEXT Results]

Channel Return Loss
(measured from TC)
0

-10

-20
RL Pair 1
RL Pair 2
dB

-30 RL Pair 3
RL Pair 4
RL Cat 6
-40

-50

-60
1 10 100 1000
PS-6
Frequency (MHz) 9-Oct-98

Figure 7 - System 4800LX [Return Loss Results]
*

13

Conclusions
Cabling technology is progressing at a rapid pace. The development work on a
new cabling standard for Category 6* is nearing completion. NORDX/CDT is at
the forefront of this technology by announcing two new products. The first is an
innovative UTP cable design with a cross-web filler that provides the highest
signal strength and the highest signal-to-noise performance in the industry. The
second is a new series of GigaFlex PS6+ connecting hardware and PS6LX patch
cords. The new connectivity hardware is small in size and big on performance.
The mated plug-jack connection is fully backward compatible with Category 5 as
specified in TIA/EIA 568-A, A2, A4 & A5.

The new 4800LX cable, GigaFlex PS6+ connectivity hardware and PS6LX cords
make up the IBDN System 4800LX which delivers an unsurpassed bandwidth of
300 MHz and an information capacity up to 4 times that of Category 5.
NORDX/CDT has taken a strong position in the marketplace and in the
standards forums to recognize and promote better cabling. We support the IEEE
recommendation that the next generation of cables should have a lower
attenuation performance. Our IBDN System 4800LX meets this objective while
providing more headroom. The channel attenuation (insertion loss) is 4.5 dB
lower and the PSACR is 10 dB higher than the current Category 6* proposal at
200 MHz. The additional headroom in channel attenuation and PSACR is a
safeguard against adverse environmental conditions such as elevated
temperatures, installation variables and alien crosstalk that can degrade system
performance and data throughput. It is especially important to take into account
the maximum cable operating temperature, which can significantly 20 degrees C
that is currently specified in the draft Category 6* standard.

We believe that a Category 6* channel that meets 200 MHz of bandwidth under
all worst case conditions, will become the embedded base cabling for system
designers developing new applications. Whatever the future brings, whether it’s
2.4 Gb/s, 4 Gb/s or 4.8 Gb/s, the next generation cabling system will need to
have the reserve capacity built-in for what’s coming next.

References

[1] Article “The Next Generation of Cable Technology” A technology primer from
NORDX/CDT, November 1998

Acknowledgements
The author is grateful to the all the members of the PLM, Marketing and
Technology team who contributed to the success of this project.

*

14

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