SIST EN 50083-10:2003
(Main)Cable networks for television signals, sound signals and interactive services -- Part 10: System performance for return paths
Cable networks for television signals, sound signals and interactive services -- Part 10: System performance for return paths
Standards of EN 50083 series deal with cable networks for television signals, sound signals and interactive services including equipment, systems and installations
for headend-reception, processing and distribution of television and sound signals and their associated data signals, and
for processing, interfacing and transmitting all kinds of signals for interactive services using all applicable transmission media.
All kinds of networks like
CATV-networks
MATV-networks and SMATV-networks
individual receiving networks
and all kinds of equipment, systems and installations installed in such networks, are within this scope.
The extent of these standardisation work is from the antennas, special signal source inputs to the headend or other interface points to the network up to the system outlet or the terminal input, where no system outlet exists.
The standardisation of any user terminals (i.e. tuners, receivers, decoders, multimedia terminals etc.) as well as of any coaxial and optical cables and accessories therefor is excluded.
Kabelnetze für Fernsehsignale, Tonsignale und interaktive Dienste -- Teil 10: Rückkanal-Systemanforderungen
Réseaux de distribution par câbles pour signaux de télévision, signaux de radiodiffusion sonore et services interactifs -- Partie 10: Caractéristiques des systèmes de voie de retour
Kabelska omrežja za televizijske in zvokovne signale ter interaktivne storitve - 10. del: Lastnosti sistema za povratne poti
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 50083-10:2003
01-december-2003
1DGRPHãþD
SIST EN 50083-10:2000
Kabelska omrežja za televizijske in zvokovne signale ter interaktivne storitve - 10.
del: Lastnosti sistema za povratne poti
Cable networks for television signals, sound signals and interactive services - Part 10:
System performance for return paths
Kabelnetze für Fernsehsignale, Tonsignale und interaktive Dienste - Teil 10: Rückkanal-
Systemanforderungen
Réseaux de distribution par câbles pour signaux de télévision, signaux de radiodiffusion
sonore et services interactifs - Partie 10: Caractéristiques des systèmes de voie de
retour
Ta slovenski standard je istoveten z: EN 50083-10:2002
ICS:
33.060.40
SIST EN 50083-10:2003 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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EUROPEAN STANDARD EN 50083-10
NORME EUROPÉENNE
EUROPÄISCHE NORM March 2002
ICS 33.060.40 Supersedes EN 50083-10:1999
English version
Cable networks for television signals,
sound signals and interactive services
Part 10: System performance for return paths
Réseaux de distribution par câbles Kabelnetze für Fernsehsignale,
pour signaux de télévision, Tonsignale und interaktive Dienste
signaux de radiodiffusion sonore Teil 10: Rückkanal-Systemanforderungen
et services interactifs
Partie 10: Caractéristiques des systèmes
de voie de retour
This European Standard was approved by CENELEC on 2001-10-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands,
Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2002 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 50083-10:2002 E
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EN 50083-10:2002 - 2 -
Foreword
This European Standard was prepared by CENELEC Technical Committee TC 209, "Cable
networks for television signals, sound signals and interactive services" on the basis of
EN 50083-10:1999 and the first amendment to EN 50083-10.
The text of this first amendment was submitted to the Unique Acceptance Procedure and was
approved by CENELEC on 2001-10-01 to be published as part of a second edition of
EN 50083-10.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2002-10-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2004-10-01
Annexes designated "normative" are part of the body of the standard.
Annexes designated "informative" are given for information only.
In this standard, Annex B is normative and Annexes A and C are informative.
__________
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Contents
Page
1 Scope. 4
1.1 General. 4
1.2 Specific scope of this part 10. 4
2 Normative references . 5
3 Terms, definitions, symbols and abbreviations . 6
3.1 Terms and definitions . 6
3.2 Symbols. 8
3.3 Abbreviations. 9
4 Methods of measurement . 10
4.1 Setup of the network. 10
4.2 Measurement of signal level . 12
4.3 Measurement of amplitude response variation . 13
4.5 Measurement of multiple interference. 16
4.6 Measurement of impulse noise. 17
4.7 Measurement of echo ratio. 18
4.8 Measurement of group delay variation. 19
4.9 Measurement of frequency error . 19
4.10 Measurement of Bit Error Rate (BER) . 20
5 System performance requirements. 22
5.1 Introduction. 22
5.2 Analogue parameters influencing system performance . 23
5.3 General requirements. 24
5.4 Specific system performance requirements. 24
6 System performance recommendations. 25
6.1 Proposal for the use of the return path bandwidth . 25
Annex A (informative) System performance requirements for different
modulation techniques.…. 27
Annex B (normative) Correction factors for noise. 28
Annex C (informative) Bibliography. 30
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EN 50083-10:2002 - 4 -
1 Scope
1.1 General
Standards of EN 50083 series deal with cable networks for television signals, sound signals and
interactive services including equipment, systems and installations
− for headend-reception, processing and distribution of television and sound signals and their
associated data signals, and
− for processing, interfacing and transmitting all kinds of signals for interactive services using all
applicable transmission media.
All kinds of networks like
− CATV-networks
− MATV-networks and SMATV-networks
− individual receiving networks
and all kinds of equipment, systems and installations installed in such networks, are within this
scope.
The extent of these standardisation work is from the antennas, special signal source inputs to the
headend or other interface points to the network up to the system outlet or the terminal input,
where no system outlet exists.
The standardisation of any user terminals (i.e. tuners, receivers, decoders, multimedia terminals
etc.) as well as of any coaxial and optical cables and accessories therefor is excluded.
1.2 Specific scope of this part 10
This standard is dealing with the transparent return path of cable networks operated in the
frequency range between 5 MHz and 65 MHz or parts thereof. Higher frequencies may be used in
fibre based networks.
NOTE In addition it is possible to use the frequency range from 0 MHz to 5 MHz for return path transmissions, e.g. for
NMS or other control, monitoring and signalling purposes. Applications below 5 MHz are not covered by this standard.
An active return path carries typically only return signals. A passive return path can be used for
both return and forward signals.
This standard lays down the basic methods of measurement for signals typically used in the return
path of cable networks in order to assess the performance of those signals and their performance
limits.
All requirements refer to the performance limits which shall be obtained between the reference
points (Figure 1) of the return path system.
One reference point is the network termination close to the subscriber. It is the last point where all
forward and return signals are present and carried on the same cable. If no network termination
point exists, the reference point is the system outlet.
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The other reference point is the input of the return signal receiver (or transceiver). At this point the
transparent signal path ends and behind this point the signal is treated in a non-transparent way.
The return signal receiver can be situated at the headend but can also be at the node of the
coaxial cell or at any other point of the network.
TV
O
E
Network termination
Reference point
Figure 1 - Reference points of an active return path system (example)
In addition to the system performance requirements for the transparent return path, system
performance recommendations were laid down in this standard e.g. for the overall frequency
allocation, for the use of specific modulation techniques for different interactive multimedia
services or for different sub-bands within the return path frequency range, etc.
Specific equipment installed in cable networks for the operation of such return paths is
standardised in the relevant equipment standards, parts 3 to 6 of the EN 50083 series.
Transmission systems are not within the scope of this standard.
2 Normative references
This European Standard incorporates, by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of
any of these publications apply to this European Standard only when incorporated in it by amendment
or revision. For undated references, the latest edition of the publication referred to applies.
EN 50083 Cable networks for television signals, sound signals and
interactive services
EN 50083-1 1993 Part 1: Safety requirements
+ A1 1997
+ A2 1997
EN 50083-2 2001 Part 2: Electromagnetic compatibility for equipment
EN 50083-3 2002 Part 3: Active wideband equipment for coaxial cable networks
EN 50083-4 1998 Part 4: Passive wideband equipment for coaxial cable
networks
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EN 50083-10:2002 - 6 -
EN 50083-5 2001 Part 5: Headend equipment
EN 50083-6 1997 Part 6: Optical equipment
EN 50083-7 1996 Part 7: System performance
+ A1 2000
EN 50083-8 2002 Part 8: Electromagnetic compatibility for networks
ES 200 800 2001 Digital Video Broadcasting (DVB); DVB interaction channel for
V1.3.1 Cable TV distribution systems (CATV)
3 Terms, definitions, symbols and abbreviations
3.1 Terms and definitions
3.1.1
amplitude response variation
peak-to-peak variation in frequency amplitude response of a specified signal path over a specified
frequency band, expressed in dB
3.1.2
broadcast signal
signal comprising of video and/or audio and/or data content which is distributed to several
receivers simultaneously
3.1.3
channel availability
percentage of the time during which the channel fulfils all performance requirements. The duration
of the observation time has to be published
3.1.4
downstream direction
direction of signal flow in a cable network from the headend or any other central point (node) of a
cable network to the subscribers´ area
3.1.5
forward path (downstream)
part of a cable network by which signals are distributed in the downstream direction from the
headend or any other central point (node) of a cable network to the subscribers´ area
3.1.6
frequency error
quality of supply evaluated on the basis of the actual frequency of an electrical system compared
to the nominal value. Frequency error consists of initial error, short term and long term frequency
stability
3.1.7
headend
equipment which is connected between receiving antennas or other signal sources and the
remainder of the cable network, to process the signals to be distributed
NOTE The headend may, for example, comprise antenna amplifiers, frequency converters, combiners, separators and
generators.
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3.1.8
hybrid fibre coaxial network (HFC)
cable network which is comprised of optical equipment and cables and coaxial equipment and
cables in different parts
3.1.9
impulse noise
noise which is caused by electromagnetic interference into cable networks. Impulse noise is
characterised by pulses with a duration of typically < 10 µs
3.1.10
ingress noise
noise which is caused by electromagnetic interference into cable networks. Its power decreases
with increasing frequency. It is permanently present but slowly varies in its intensity as a function
of time
3.1.11
interaction path
part of a cable network by which interactive signals are transmitted in the downstream direction
(from the headend or node to the subscriber) and in the upstream direction (from the subscriber to
the headend or node)
3.1.12
location specific noise
noise which occurs at a specific area of a cable network or which occurs in a cable network
located in a specific environment
3.1.13
multiple interference
interfering signal which consists of ≥ 2 signals which originate from ≥ 2 sources
NOTE On return path the multiple interference consists of ingress noise and intermodulation distortion products.
3.1.14
multimedia signal
signal comprising of two or more different media contents e.g. video, audio, text, data, etc.
3.1.15
network management system (NMS)
software based system for controlling and supervising cable networks
3.1.16
network segment
part of a cable network comprising a set of functions and/or a specific extent of the complete cable
network
3.1.17
network termination
electrical termination of a cable network at any outlet on subscribers' side and headend or node
side
3.1.18
node
central point of a network segment at which signals could be fed into the forward path or could be
gathered from a number of subscribers out of the return path
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EN 50083-10:2002 - 8 -
3.1.19
return path (upstream)
part of a cable network by which signals are transmitted in the upstream direction from any
subscriber, connected to the network, to the headend or any other central point (node) of a cable
network
3.1.20
upstream direction
direction of signal flow in a cable network from a subscriber to the headend or any other central
point (node) of a cable network
3.2 Symbols
Symbols Terms Symbols Terms
Optical receiver Spectrum analyser
O
P(f)
E
Test waveform generator Passive distribution
network
Variable signal generator Oscilloscope
G
∼
Variable attenuator Low pass filter
A ∼
∼
High pass filter System Under Test
∼
SUT/NU
Network Under Test
∼
T
Demodulator Modulator
Amplifier with return path Bit Error Rate Detector
BER
amplifier
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3.3 Abbreviations
BER Bit Error Rate
BW Bandwidth, equivalent noise bandwidth
CATV Community Antenna Television
CB Citizen Band
CDMA Code Division Multiple Access
C/MI Carrier-to-Multiple Interference ratio
C/N Carrier-to-Noise ratio
COFDM Coded Orthogonal Frequency Division Multiplexing
CSO Composite Second Order
CTB Composite Triple Beat
DC Direct Current
DVB Digital Video Broadcasting
EMC Electromagnetic Compatibility
FM Frequency Modulation
FSK Frequency Shift Keying
HFC Hybrid Fibre Coaxial
IF Intermediate Frequency
IM Intermodulation
I/Q In-phase/Quadrature signals
ISM Industrial, Scientific, Medical
LPF Low-Pass Filter
MATV Master Antenna Television (Network)
MMDS Multichannel Multipoint Distribution System
MPEG Motion Picture Experts Group
MUX Multiplex(er)
MVDS Multichannel Video Distribution System
NMS Network Management System
NUT Network Under Test
OFDM Orthogonal Frequency Division Multiplexing
PAL Phase Alternating Line
PRBS Pseudo Random Binary Sequence
QAM Quadrature Amplitude Modulation
QPSK Quaternary Phase Shift Keying
RF Radio Frequency
RMS Root Mean Square
RBW Resolution Bandwidth
S Signal level, before corrections
SHF Super High Frequency
SI Service Information
SL Signal level (corrected)
SMATV Satellite Master Antenna Television (Network)
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EN 50083-10:2002 - 10 -
S/N Signal-to-Noise ratio
SUT System Under Test
TS Transport Stream
TV Television
UHF Ultra-High Frequency
VBW Video Bandwidth
VHF Very-High Frequency
4 Methods of measurement
4.1 Setup of the network
Even if the main target of this part four of this standard is to describe the measurement methods
for the performance of the return path it is very important to do this on a properly aligned network
plant. The following setup and operational procedures is a guideline for that.
The return path differs in several ways from the forward path, even though they share mostly the
same physical network. Table 1 gives some hints.
Table 1 - Characterisation criteria for downstream and upstream operations
Criteria Downstream Upstream
signals present continuously intermittently or continuously
power levels well-defined varying
channel allocation well-defined may vary over time
signal bandwidth well-defined application dependent
modulation scheme fixed application dependent
amplifier input single several inputs
As can be seen from the table the variable factors require that the procedures used to operate the
return path plant differ from those used in downstream direction.
One major difference is that the amplifiers in downstream direction are aligned by adjusting their
output signals to predetermined levels and in the return direction the network plant is adjusted so
that the input signals from different sources are equalised at the amplifier input. Different type of
signals may be at different levels.
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4.1.1 Steps to set up properly the upstream plant
Figure 2 gives a rough procedure for the setup.
Network with fibre Network without fibre
1 1
Determine input level for Determine input level for
all active equipment all active equipment
2
Inject test signal to optical
transmitter input, level: see step 1
3
Measure the level at the
headend, adjust to planned value
4 2
Inject a signal to the amplifier Inject a signal to the amplifier
closest to the optical transmitter, closest to the headend,
input level: see step 1 input level: see step
1
5 3
Measure the level at the
optical transmitter input or
Measure the level at the headend
at the headend
6 4
Adjust the output of the Adjust the output of the ampli-
amplifier so that the input level fier so that the input level at the
at the optical transmitter or at the headend is according to step 1
headend is according to step 1
7 5
Continue with the following Continue with the following
amplifier in the downstream amplifier in the downstream
direction direction
Figure 2 - Procedure for setup and adjustment of an upstream plant
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EN 50083-10:2002 - 12 -
4.2 Measurement of signal level
4.2.1 Introduction
The method described is applicable to the measurement of the level of RF signals which do not
have a clear carrier (e.g. QPSK and QAM modulated carriers).
4.2.2 Equipment required
The equipment required is a spectrum analyser having a known noise bandwidth and a calibrated
display. The calibration accuracy should be preferably within 0,5 dB.
4.2.3 Connection of the equipment
Connect the measuring equipment to the point where the measurement shall be performed by
using a suitable connection lead. Take care of correct impedance matching.
4.2.4 Measurement procedure for RF signals without carriers
a) If a high level ambient field is present, check that the measuring equipment has no spurious
readings. Connect a shielded termination to the connection lead, place the test equipment and
the connection lead approximately in their measuring positions and check that there is a
negligible reading at the frequency(ies) and on the meter ranges to be used.
b) Tune the spectrum analyser to the channel that shall be measured (by selecting the centre
frequency of the spectrum analyser) and select the span and level settings to show the whole
channel. Examples of the Nyquist bandwidth of digitally modulated carriers are given in
Table 2.
Table 2 - Examples of the Nyquist bandwidth of digitally modulated carriers
Type of digital channel Nyquist bandwidth
MHz
QPSK 0,256 Mbit/s 0,128
QPSK 1,544 Mbit/s 0,772
QPSK 3,088 Mbit/s 1,544
Cable DECT 1,728
16QAM 12,8 Mbit/s 3,2
c) Set the resolution bandwidth (RBW) of the spectrum analyser to 30 kHz (or lower than one
tenth of the equivalent bandwidth) and the video bandwidth to 1 kHz (or lower to obtain a
smooth display). Use an rms-type detector.
d) Measure the signal level (S) at the centre frequency of the channel in dB(µV).
e) Measure the -3 dB frequencies of the channel. The difference between these two frequencies
is assumed to be the equivalent signal bandwidth (BW).
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NOTE This measurement is important for the QPSK modulation format where the equivalent signal bandwidth
depends on the bit rate of the transmitted signal and the inner code rate used.
f) Calculate the signal level (SL) by using formula:
SL = S + 10 lg (BW / RBW) + K
The correction factor (K) depends on the measuring equipment used and shall be provided by
the manufacturer of the measuring equipment or obtained by calibration. The value of the
correction factor for a typical spectrum analyser is about 1,7 dB.
If the measuring equipment can display the level in dB(mW/Hz), the correction factor K is not
needed and the level (SL) in dBm can be obtained from the measured level (S) by using the
formula:
SL = S + 10 lg (BW)
NOTE This measuring method actually measures the S+N level. The contribution of noise is considered negligible
if the level of noise outside the equivalent channel band is at least 15 dB lower than the measured level (S).
4.2.5 Presentation of the results
The measured level shall be expressed in dB(µV) referred to 75 Ω.
4.3 Measurement of amplitude response variation
4.3.1 Background
There are a number of propriety test equipment(s) available which are specifically designed for
this purpose. However, since these may not be readily available, the method, which is described
here, uses test equipment that is usually in service by CATV engineering staff.
NOTE The proposed method of measurement can not be used in networks under service.
4.3.2 Equipment required
a) All equipment and cables needed for this method of measurement shall have 75 Ω impedance
(with matching attenuators if required).
b) A signal generator covering at least 3 MHZ to 80 MHz. This should have an output level of at
least 114 Db(µV) and must be capable of sweeping automatically.
c) A spectrum analyser covering the frequency range of interest. This shall have a peak hold and
storage facility and be capable to sweep at a slow speed (greater than 30 s for a horizontal
trace).
d) A calibrated attenuator which can be changed in 1 dB steps. This shall be suitable for the
frequency range of interest and may be built into the spectrum analyser.
e) A plotter or printer, which can be used to store the spectrum analyser screen trace. This is
optional but desirable.
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EN 50083-10:2002 - 14 -
4.3.3 Connection of the equipment
The equipment shall be connected as in Figure 3.
G
A A P(f)
∼
Printer
or
NUT
Plotter
Figure 3 - Arrangement of test equipment
for measurement of amplitude response variation
4.3.4 Calibration of the equipment
a) Set the sweep generator to cover the frequency range to be measured and the output to the
design reference level.
b) Set the sweep time to 50 ms or less.
c) Connect the sweep output from the generator to the input of the spectrum analyser.
Calibrated variable attenuators may be required if these are not built into the spectrum
analyser.
d) Adjust the analyser display such that the sweep is on the screen with the vertical resolution
set to 1 dB per division. The frequency span should be set to sweep at least 2 MHz above and
below of the range of interest.
e) Set the resolution bandwidth (RBW) of the spectrum analyser to 1 MHz and the video
bandwidth to 100 kHz. Reduce the analyser sweep time to 50 s or greater.
f) Set the display to "maximum hold" and single sweep. Clear the screen.
g) Trigger the analyser and capture the reference sweep on screen. Record the result. Where
the spectrum analyser has a “Normalise” function this may be used at this point.
h) Increase the path loss by 1 dB and repeat step g). Repeat to obtain calibration lines from 0 dB
to -10 dB.
i) Return the attenuator to the initial setting (0 dB calibration).
4.3.5 Method of measurement
Connect the analyser and sweep generator to the network points to be measured. Ensure that
both the sweep injection level and analyser input levels are at the correct settings. Repeat the
single sweep and plot the result. The amplitude response variation can be read from the final plot.
4.3.6 Presentation of the results
The amplitude response variation is expressed in dB as the maximum to minimum excursion. The
injection and measurement points shall be stated together with the frequency limits.
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4.4 Measurement of signal to noise ratio (S/N)
4.4.1 Introduction
The C/N measurement of an analogue television channel is described in EN 50083-7. The same
method can be used also on the return path for signals which have a clear carrier. Noise
bandwidth which is applicable for the channel under test shall be used.
This part 10 describes a method of measurement for channels, which have a frequency spectrum
without a clear carrier (e.g. QPSK or QAM modulated channels). The S/N-ratio of such channels is
the modulated channel power divided by the channel noise power. The channel noise power is the
power of the noise which is present within the whole bandwidth of the modulated channel.
Ingress noise may interfere with C/N and S/N measurements. To minimise the influence of ingress
noise C/N and S/N should be measured at frequencies above 15 MHz or at frequencies for which
the return service is designed.
4.4.2 Equipment required
The equipment required is a spectrum analyser having a known noise bandwidth and a calibrated
display. The calibration accuracy should be preferably within 0,5 dB.
4.4.3 Connection of the equipment
Connect the measuring equipment to the point where the measurement shall be performed by
using a suitable connection lead. Take care of correct impedance matching.
4.4.4 Measurement procedure
a) Tune the spectrum analyser to the channel that shall be measured (by selecting the centre
frequency of the spectrum analyser) and select the span and level settings to show the whole
channel.
b) Set the resolution bandwidth (RBW) of the spectrum analyser to 30 kHz (or lower than one
tenth of the equivalent bandwidth) and the video bandwidth to 1 kHz (or lower to obtain a
smooth display). Use a rms-type detector.
c) Read the level of the signal (S) at the centre frequency of the channel.
d) Switch-off the channel at the input of the system or by terminating the input port with a
matched impedance. If necessary, fine-tune the centre frequency of the spectrum analyser to
avoid ingress carriers. Use otherwise the same settings of the spectrum analyser as described
in 4.4.4.2 and read the noise level (N) in dB(µV). If the signal cannot be switched off during
measurements, measure the noise level at a frequency, which is close to the channel and
includes only gaussian noise.
e) The spectrum analyser should have a noise level which is more than 10 dB lower than the
measured noise level (N). Check it by terminating the input of the spectrum analyser. If the
difference between N and spectrum analyser noise is 3 to 10 dB, correct the value of N as
advised in Annex B.
f) Calculate the signal to noise ratio (S/N) by using the following formula:
(S/N) = S - N
dB dB(µV) dB(µV)
4.4.5 Presentation of the results
The measured signal to noise ratio (S/N) shall be expressed in dB.
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EN 50083-10:2002 - 16 -
4.5 Measurement of multiple interference
4.5.1 Introduction
The multiple interference consists of ingress noise and intermodulation distortion products. It is
measured with a spectrum analyser. For 24 hours the interference spectrum is stored in a data
memory every 10 seconds.
As forward path signals may
...
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