Broadband Video over Category 6 UTP Cabling
Paul Kish
Michel Bohbot
NORDX/CDT
Pointe-Claire, Quebec, Canada
+1-514-822-2345
paul.kish@nordx.com
michel.bohbot@nordx.com
Abstract
Category 6 as well as a low loss Category 6 cable with
improved crosstalk performance.
We tested each of the
three channels under two different configurations. The first
configuration evaluated the picture quality using a modulated
signal carrier at 547 MHz (Channel 78). The second
configuration evaluated the picture quality using a modulated
signal carrier at 55 MHz (Channel 2) while simultaneously
applying a 100BASE-TX Ethernet signal on the same cabling.
In this paper, we will provide information on the application
of broadband video over high performance Category 6 UTP
cabling. We will describe the implementation of a broadband
video distribution system over twisted pair cabling and some
applications where it might be used. We will look at the
advantages of running broadband video transmission over a
parallel network (RF highway) compared to running video
over the corporate LAN highway.
We have recently
completed a series of comprehensive tests to demonstrate the
technical feasibility of running broadband video (CATV) over
a high-end Category 6 cabling system up to a frequency of
550 MHz (78 channels of NTSC video). This paper will show
the results of these tests in a real-time environment including
signal level measurements, alien noise measurements, and the
effect of simultaneous LAN and video transmission in the
same cable.
An appreciable difference in picture quality was observed for
the three different channels that were tested, due to the effect
of signal interference or due to the signal losses in the cabling.
It is not sufficient to demonstrate qualitative differences in
picture quality. It is also necessary to verify that the UTP
cabling complies with the stringent requirements of CATV
distribution systems. To this end all the parameters required
for satisfactory video performance were determined and
independently verified by an independent laboratory. These
tests include signal level measurements and tilt adjustment for
the video and audio carrier levels across the frequency band up
to 550 MHz, noise ingress measurements due to different
noise sources and signal leakage measurements to establish
compliance with regulatory emissions requirements.
Keywords
Category 6; Broadband video; UTP; CATV; IP video; RF
transmission, NTSC; video distribution; twisted-pair; balun.
1. Introduction
The recent publication of the Category 6 standard by TIA
marks an important milestone in the evolution of network
cabling. Category 6 provides a significant improvement in
transmission performance compared with Category 5/5e
cabling with a specified frequency range of 250 MHz and a
capability extending much higher in practice.
What
applications can take full advantage of the higher bandwidth
and improved performance of Category 6 cabling? One of
the most demanding applications on the market today is
broadband video, commonly known as CATV or cable
television. It carries a broad range of signals extending to 650
MHz and beyond.
Coaxial cable (RG-59 or RG-6) is
commonly used for these applications, primarily for home
networks. Most people are not aware that high performance
twisted pair cabling can also support broadband video.
2. Broadband video distribution
Figure 1 illustrates how broadband video can be distributed in a
business environment. Potential applications would include
Cable TV/ Satellite newscasts, stored or live video broadcast,
distance learning, security monitoring and video conferencing.
Satelite, Antenna
or CATV input
Patch Panel
Cat 5e / 6 / 6+
UTP
Combiner
Distribution Hub
Modulator
DVD Player
Video Camera
...
To simulate a worst-case scenario, we tested 100-meter
channels that were representative of typical Category 5e,
1
BB Video
balun
DTV & NTSC
channels
Figure 1 – Broadband video distribution in a business
environment
5e, 500 MHz for Category 6 and 650 MHz for a high-end
Category 6 channel, such as the NORDX/CDT 4800LX
System, which has a very low Insertion Loss and about 10 dB
improved SNR beyond the Category 6 standard. This is the
theoretical upper limit based on signal quality. For this graph,
it is assumed that the transmission characteristics of the
cabling are well behaved beyond the maximum frequency
specified for Category 5e (100 MHz) and Category 6 (250
MHz). Other transmission impairments can further restrict
either the maximum reach (100 meters) or the maximum
number of channels supported.
A big advantage of broadband video over twisted pair is that it
has the capability to transmit many channels simultaneously
using only a single pair in a 4-pair cable for broadcast video
distribution or two pairs for bi-directional interactive video
transmission.
What is the composition of a broadband video signal? A
standard-definition composite video signal is composed of the
video information (luminance and chroma) and the audio
information. The composite video signal is then modulated
on a carrier as shown in Figure 2. Different channels are
spaced at 6 MHz intervals. Therefore, depending on the
bandwidth of the cabling, many channels can be carried at the
same time. A typical allocation would carry from channel 2
to channel 78 using a frequency band from 54 MHz to 550
MHz.
Worst-case Channel Insertion Loss
including balun losses
100.0
Cat 5/5e
Weak signal
snowy picture
Cat 6
80.0
Loss (dB)
Cat 6+
6 MHz
Video Carrier
Color
Audio
60.0
40.0
20.0
e.g.
Luminance
Chroma
0.0
Channel 2
54 MHz
0
1.25 MHz
3.58 MHz
60 MHz
100
200
300
400
500
600
700
800
900
Frequency (MHz)
4.5 MHz
Figure 3 – Insertion Loss for different cable categories
Figure 2 – Composite video bandwidth allocation
What are the different options for delivering video to the
desktop and what are some of the advantages of a broadband
video (CATV) distribution network? One option is Video
over IP using the corporate LAN.
To some extent this
option is already in use today with video clips, newscasts and
web camera images available through the Internet. The video
images tend to be of a lower resolution than broadcast quality
video, e.g. a DVD movie requires a transmission capacity of 6
– 8 Mb/s using MPEG-2 video compression. A major
deterrent for implementing Video over IP over the corporate
LAN is that real time video imposes severe demands on
bandwidth and Quality of Service (QoS) for your network.
The broadband video systems on the market today are
designed to be used with 75 Ohm coaxial cables. To transmit
these signals over 100 Ohm balanced twisted pair cabling
requires a high quality broadband balun (Balanced to
unbalanced transformer) at either end of the channel to adapt
a 75 Ohm coaxial input using an F-connector to a 100 Ohm
balanced output using a modular 8-position connector.
How far can you transmit video signals over Category 5e and
Category 6 cabling? Most video receivers (e.g. TV sets) are
designed to accommodate a wide dynamic range of signals.
The minimum signal level at the remote television receiver is
around 1 mV pk-pk (-10 dBmV). With weaker signals, the
picture is snowy and also much more susceptible to external
noise. The maximum output level from the local amplifier is
around 1 V pk-pk (50 dBmV), giving a dynamic range of up to
60 dB for the cabling. It should be noted that the signal level
may need to be reduced below 50 dBmV because of radiated
emission requirements that can further limit the dynamic
range for the application.
QoS is extremely important when implementing a converged
network in which video, voice and data share the same IP
circuit. Without effective QoS, bursty data traffic can disrupt
video traffic, causing glitches, cutouts, frame loss, and other
consequences. This results in severe quality degradation and
user dissatisfaction. It can be an expensive proposition to
upgrade an existing LAN to support high quality video. That
is why it makes sense to consider a parallel broadband
network, to deliver video to those locations that need it,
conference rooms, class rooms, bulletin boards, select users.
Another advantage of doing it over high performance UTP
cabling is that the Category 5e and higher cabling is already
Figure 3 is a graph of the frequency range that can be
accommodated for a 100-meter Category 5e, Category 6 and
a high-end Category 6 channel based on a 60 dB Insertion
Loss limit. The frequency range is 400 MHz for a Category
2
installed in commercial buildings, is easy to administer an does
not require the disruption of installing new coaxial cabling.
Figure 4 illustrates conceptually the advantages of a parallel
RF highway, analogous to a high speed train that is called the
Broadband Express, which can deliver up to 3.4 Gb/s of
dedicated transmission capacity for broadcast quality video
and
audio.
Figure 6 – Broadband video application – Satellite feeds
Broadband Express
Control
LAN
Modulators
Multiplexers
RF Highway
LAN
Hi
gh
y
wa
RF
High
Combiner
- Reserved bandwidth
- Allocated space
(up to 40 Mb/s per channel)
- No congestion / no delays
- Optimized for high volume
- IP control / scheduling
- Large capacity
~ 85 analog channels
~ 500 digital channels
way
T Channels
MHz Channel
7.00
13.00
19.00
25.00
31.00
37.00
43.00
49.00
Figure 4 –Advantages of a separate broadband video network
How do you implement a broadband video distribution system
to support streaming video applications under IP control, to
deliver satellite feeds and for security monitoring? Without
getting into too many details as to the type of equipment
required, Figure 5, 6 and 7 illustrate a block diagram of how
the system is implemented for different applications.
ATM,
T1, DSL, ISDN
RF Wireless
3. Performance evaluation
3.1 Test configuration and results - Video
To evaluate the performance of broadband video distribution
over Category 6 UTP cabling, we used the test configuration
and the components shown in Figure 8. The broadband video
distribution hub (16-port) and the balun adapter at the work
area location are manufactured by Z-Band Corporation. We
installed seven IBDN 4800LX cables in a 1-inch conduit to
simulate a worst-case installation with 90 meters of cable and
10 meters of patch cords. This allowed us to perform the
testing in a worst-case scenario while simultaneously loading
all the cables with video and or LAN signals to take into
account the effect of alien crosstalk between cables.
Video Server
Router
BB Video
Distribution
Network
40 GB
drive
~ 40 hrs
of content
at 6 Mbps
Modulator
Combiner
multi-channel
MPEG-2 decoder
PCI cards
Modulator
...
Hard drive
T7
T8
T9
T10
T11
T12
T13
T14
Figure 7 – Broadband video application – Security monitoring
LAN
1, 2, 4, 8, 12, or 16
video channels
Test Configuration
(Signal Level and Alien Crosstalk)
Modulator
Figure 5 – Broadband video application - Streaming video
Digital Video Broadcast
Sweep
Generator
L Band
950-2150 MHz
Digital QAM
set-top terminal
L Band QPSK
Tuner Demod.
QAM
Mod.
Upconverter
(50-860 MHz)
L Band QPSK
Tuner Demod.
QAM
Mod.
Upconverter
(50-860 MHz)
L Band QPSK
Tuner Demod.
QAM
Mod.
Upconverter
(50-860 MHz)
...
All other CATV channels
RF Combiner
Splitter
QPSK to QAM Transmodulator
BB Video
Distribution
Network
Vid
Aux
...
G-BUD
BB Video
Distribution
Network
3
G-Flex
Patch Panel
PS6LX
cords
5m
a 4800LX 90 m
b
c
d
e
f
g 4800LX 90 m
1" conduit
a
b
c
d
e
f
g
5m
Wall
Aux
G-BOB
Level
Meter
Figure 8 – Setup for signal level and alien crosstalk
measurements
The first series of tests performed included measuring the
signal level at the input of the distribution hub and at the
output of the balun in the work area over the frequency range
from 50 MHz to 550 MHz. The alien crosstalk was measured
by applying a signal on channel B through G respectively and
measuring the noise coupled on channel A. The results are
shown in Figure 9. After completion of these tests quality of
the picture from a DVD player modulated on channel 2
(55,25 MHz) and channel 78 (547.25 MHz) was observed and
noted with and without alien noise present.
Figure 10 – Setup for signal level and ingress measurements
When the broadband video and LAN signal are present
simultaneously in the same cable, we observed that measured
ingress generated by the 100BASE-TX signal was limited to a
frequency range under 200 MHz, and therefore, the main
effect was at lower channels (NTSC channel 2 – 6). The
ingress from LAN signal on adjacent cables (Alien NEXT) is
insignificant.
Signal Level and Alien Noise
The ingress measurements are shown in Figure 11 and 12
respectively, for 100BASE-TX signals in the same cables and
in adjacent cables, respectively.
40
30
20
Level (dBmV)
10
GigaBUD I/P
Rx A
0
Nx B=>A
Nx C=>A
-10
-20
Nx D=>A
Nx E => A
-30
Nx F=>A
N G=>A
Ingress measurements - Case I
30
-40
Ch 2
20
-50
10
-60
100
200
300
400
500
600
Level (dB)
0
Frequency (MHz)
Figure 9 – Signal level and alien noise measurements
0
Vid + LAN
-10
Vid only
LAN only
Ambient
-20
Chn 2
-30
-40
The main effect of the alien noise was changing the level of
the signal slightly, either higher or lower compared to the
receive signal without alien noise present mainly at the higher
frequencies. There was no significant effect on picture quality
that was noticeable.
-50
0
50
100
150
200
250
Frequency (MHz)
Figure 11 – Ingress from LAN and Video in same cable
3.2 Test configuration and results - LAN and
Video
Ingress measurements - Case II
To evaluate the performance of broadband video distribution
and LAN over the same cabling or over separate cabling, we
used the test configuration and the components shown in
Figure 10. For this test, the 100BASE-TX signal was injected
into the auxiliary ports of the Broadband video distribution
hub using a crossover patch cord (pairs 2, 3 à pairs 1,2).
The other two pairs, pair 4 and pair 3 are used for outgoing
and incoming video respectively.
30
Ch 2
20
Level (dB)
10
0
Ambient
Vid + LAN(alien)
-10
LAN(alien)
Chn 2
-20
-30
-40
Test Configuration
(LAN & Video)
Sweep
Generator
PS6LX
cords
Vid 5 m
a
Aux
b
c
d
e
f
g
G-BUD
-50
0
...
1" conduit
100
150
200
250
Frequency (MHz)
G-Flex
Patch Panel
4800LX 90 m a
b
c
d
e
f
4800LX 90 m g
50
Figure 12 – Ingress from LAN and Video in separate cables
What is the effect on picture quality of running LAN and
video in the same cable? First of all, it requires a cabling
5m
Wall
Aux
G-BOB
Level
Meter
BoseLAN
VoIP Switch
SmartBits
100BASE-TX
Traffic Generator
4
3.3 Additional testing
system with very good crosstalk isolation between pairs. For
the cabling used in these tests, the NEXT crosstalk isolation is
about 8 dB better than specified by the TIA 568-B.2.1
(Category 6) standard.
This paper presents some of the main parameters that were
tested in a real time environment to evaluate the technical
feasibility of broadband video transmission over high-end
UTP cabling. The authors would like to mention the results
of other independent tests that were performed in our
laboratory that are provided in an independent third party
test report (see reference 1). These additional tests include
leakage measurements in compliance with FCC part 15 –
Radio Frequency devices, subpart B, unintentional radiators.
This report is available on our web site at www.nordx.com.
At the time of this writing, a more comprehensive series of
emissions test is in progress at an independent test laboratory
and will be reported during the IWCS proceedings.
To look at the effect on picture quality we varied the level of
the video signal until there was a perceptible interference
pattern on the received picture on the TV monitor. This
effect is illustrated in Figure 13 and Figure 14 when applying a
video signal on channel 2 (55,25 MHz). For a weak signal,
e.g. –1 dBmV (Figure 13), the interference in quite visible.
For a stronger signal, e.g. 16 dBmV, the interference is not at
all noticeable. For video transmission over this type of
cable, it is recommended to adjust the amplifier gain to
provide a minimum of + 20 dBmV on channel 2 and – 5
dBmV on channel 78 for good picture quality. Note: These
pictures are captured images from a DVD movie entitled
“Back to the Future”
4. Conclusions
Broadband video is definitely one application that can take
full advantage of the improved transmission performance
offered by Category 6 cabling and beyond. A low Insertion
Loss and a high Signal-to-Noise Ratio are the most important
cabling parameters for the broadband video application.
Although the composite video signal is an analog signal today,
future digital television signals will use the same broadband
frequency spectrum and channel allocation but a different
digital modulation scheme (MPEG-2 / 8-VSB or 256- QAM).
Digital television offers the potential to carry up to 500
standard definition channels using the frequency range from
50 MHz to 550 MHz bandwidth.
LAN
Ch2
-1 dBmV
No LAN
Ch2
-1 dBmV
Broadband video can find all kinds of applications in a
business environment including specialty news channels, video
conferencing, distance learning and security monitoring.
There is an advantage to having the video application running
on a separate broadband network to prevent network
congestion and bottlenecks. High quality video will be the
next wave of applications that will have a dramatic impact on
your network. High performance Category 6 cabling is well
positioned to meet the bandwidth requirements for these
applications.
Figure 13 – Effect of LAN interference for a weak signal
LAN
Ch2
16 dBmV
4.1 Authors
No LAN
Ch2
-1 dBmV
Figure 14 – The effect of LAN interference for a stronger
signal
5
magazines and technical conferences. He has presented
seminars at BICSI and other industry forums to promote
cabling standards and the need for higher performance cabling.
Michel Bohbot graduated in electrical engineering from the
University of Montreal, Quebec, Canada in 1985. He also
graduated in Nuclear engineering from Geneva Engineering
School, Switzerland in 1982. He started to work as a design
engineer in the development of passive and active networking
product in 1985. He joined Northern Telecom in 1989 to
work on cabling system testing. He has held a number of
positions at Northern Telecom including Product Manager for
Networking Equipment and Manager for the IBDN Systems
and Applications Laboratories.
Paul Kish is Director, IBDN Systems and Standards with
NORDX/CDT. He is the current vice-chairman of the TIA
TR-42
engineering
committee
responsible
for
telecommunications cabling standards for commercial and
residential installations.
He has been active in the
development of cabling standards since 1989 with TIA. He
has also participated in standards development at CSA,
ISO/IEC and IEEE. He initiated the work that led to the
publication of additional specifications for Category 3, 4 & 5
cables, which have had a major impact in the cabling industry.
Paul Kish is also a member of the BICSI TIM Committee that
is responsible for the Chapters on Cable Transmission and
Electromagnetic Compatibility.
5. Acknowledgments
Special thanks to Christian Yamego of NORDX/CDT staff for
his help in the development of the test setup and for assisting
with the lab measurements.
Paul Kish graduated with an M.A.Sc. Degree in electrical
engineering from the University of Waterloo, Ontario,
Canada in 1972.
He started to work as a cable design
engineer with Bell Northern Research in 1972. He joined
Northern Electric a year later to work on cable development
projects. He has held a number of positions at Northern
Telecom including Manager of the Cable Development
Laboratories, Manager of Cable Design and Product Manager
for IBDN Cabling. Paul Kish is recognized in the industry as
an expert in “cable transmission”. He has authored many
technical papers that have been published in various industry
DVD movie entitled “Back to the Future”, 2002 Copyright,
Universal Studios.
6. References
[1] Intertek ETL Semko, “Broadband Video Over Twisted
Pair Cabling,” ETL Report No. 3040657, May 7, 2003.
www.nordx.com/public/htmen/Broadband_Video.htm
6