IEC 60728-10:2001

Cabled distribution systems for television and sound signals - Part 10: System performance of return path

Deals with the transparent return path of cable networks operated in the frequency range 5 MHz to 65 MHz. Lays down basic methods of measurement for signals used in the return path, in order to assess the performance and performance limits.

General Information

• Status: Published
• Publication Date: 06-Mar-2001
• ICS: 33.060.40 - Cabled distribution systems
• Technical Committee: TC 100 - Audio, video and multimedia systems and equipment
• Current Stage: DELPUB - Deleted Publication
• Start Date: 27-Jun-2005
• Completion Date: 26-Oct-2025

Relations

• Revised: IEC 60728-10:2005 - Cable networks for television signals, sound signals and interactive services - Part 10: System performance of return paths
• Effective Date: 05-Sep-2023

Overview

IEC 60728-10:2001 defines performance assessment and measurement methods for the transparent return path (upstream) of cabled distribution systems (e.g., CATV, HFC, MATV/SMATV) operating in the 5 MHz to 65 MHz frequency range. The standard specifies how to measure return-path signals and how to judge system performance limits between defined reference points (typically the network termination near the subscriber and the input of the return-signal receiver at the head-end or node). It covers active and passive return paths, gives performance requirements and recommendations (including bandwidth allocation and modulation guidance), and excludes applications below 5 MHz and terminal device standardization.

Key topics and technical requirements

• Frequency scope: Return path operation from 5 MHz to 65 MHz (higher frequencies may apply in fibre-based networks); <5 MHz not covered.
• Measurement methods: Standardised procedures to evaluate upstream signals, including:
  • Signal level and amplitude response
  • Signal-to-noise ratio (S/N)
  • Multiple interference (e.g., ingress noise + intermodulation)
  • Impulse noise and location-specific noise
  • Echo ratio and group delay variation
  • Frequency error / stability
  • Bit error rate (BER) for digital upstream signals
• Reference points: Clear definition of where performance is measured - the subscriber-sided network termination (or system outlet) and the input to the return-signal receiver.
• Performance limits & recommendations: Requirements for acceptable upstream transmission quality and suggested use of return-path sub-bands and modulation techniques (informative annexes provide modulation-related guidance; a normative annex provides noise correction factors).

Practical applications and users

Who uses IEC 60728-10:

• Cable operators / network designers for upstream bandwidth planning and acceptance testing
• Head-end and node engineers for setting receiver input limits and tuning upstream paths
• Test & measurement engineers to perform standardised measurements (S/N, BER, impulse/ingress noise)
• Equipment manufacturers of amplifiers, return-path receivers, CMTS-like devices and optical node interfaces
• Installers and maintenance teams for fault diagnosis and commissioning

Practical benefits:

• Consistent, repeatable measurement procedures for upstream quality
• Improved interoperability between network elements and equipment
• Clear criteria to diagnose ingress, impulse noise and intermodulation affecting return channels

Related standards

• IEC 60728-1, -3, -4, -5, -6, -11 (series on cabled distribution systems)
• EN 50083 series (cable networks)
• ETS 300 800 (DVB interaction channel for CATV)
• ITU recommendations referenced for transmission and TV systems

Keywords: IEC 60728-10, return path, upstream, cable networks, 5–65 MHz, BER, ingress noise, impulse noise, S/N, echo ratio, CATV, HFC, measurement methods.

Standards Content (Sample)

INTERNATIONAL IEC
STANDARD
60728-10
First edition
2001-03
Cabled distribution systems for television
and sound signals –
Part 10:
System performance of return path

Reference number
Publication numbering
As from 1 January 1997 all IEC publications are issued with a designation in the
60000 series. For example, IEC 34-1 is now referred to as IEC 60034-1.

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edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the base publication, the
base publication incorporating amendment 1 and the base publication incorporating
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INTERNATIONAL IEC
STANDARD
60728-10
First edition
2001-03
Cabled distribution systems for television
and sound signals –
Part 10:
System performance of return path
:
 IEC 2001  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission 3, rue de Varembé Geneva, Switzerland
Telefax: [phone] e-mail: [e-mail] IEC web site http://www.iec.ch
Commission Electrotechnique Internationale
PRICE CODE
U
International Electrotechnical Commission
For price, see current catalogue

– 2 – 60728-10  IEC:2001(E)
CONTENTS
Page
FOREWORD .3

INTRODUCTION.4

Clause
1 Scope.5

2 Normative references .6

3 Terms, definitions, symbols and abbreviations .7

3.1 Terms and definitions .7

3.2 Symbols .9
3.3 Abbreviations .9
4 Methods of measurement .10
4.1 Set-up of the network .10
4.2 Measurement of signal level .11
4.3 Measurement of amplitude response .13
4.4 Measurement of signal to noise ratio (S/N) .13
4.5 Measurement of multiple interference .14
4.6 Measurement of impulse noise .15
4.7 Measurement of echo ratio .16
4.8 Measurement of group delay variation .17
4.9 Measurement of frequency error .17
4.10 Measurement of bit error rate (BER) .18
5 System performance requirements .20
5.1 Introduction .20
5.2 Analogue parameters influencing system performance.21
5.3 General requirements.22
5.4 Specific system performance requirements.22
6 System performance recommendations .23
6.1 Proposal for the use of the return path bandwidth .23
Annex A (informative) System performance requirements for different modulation techniques.25
Annex B (normative) Correction factors for noise.26
Bibliography.28

Figure 1 – Reference points of an active return path system (example).5
Figure 2 – Procedure for set-up and adjustment of the upstream system .11
Figure 3 – Arrangement of test equipment for measurement of echo ratio.17
Figure 4 – Test set-up for frequency stability measurement .18
Figure 5 – Principle of BER measurement .18
Figure 6 – Upstream signals affecting downstream signals .20
Figure 7 – Downstream signals affecting upstream signals .21
Figure 8 – Upstream signals of service 1 affecting upstream signals of a different service
(e.g. service 2).21
Figure 9 – Upstream signals of a specific service (e.g. service 2) affecting upstream signals
of the same service.21
Figure 10 – Identification of the most common sub-bands within the return path band with
limited transmission quality .24
Figure B.1 – Noise correction factor (CF) versus measured level difference (D) .27
dB dB
60728-10  IEC:2001(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
CABLED DISTRIBUTION SYSTEMS FOR TELEVISION

AND SOUND SIGNALS –
Part 10: System performance of return path

FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising all
national electrotechnical committees (IEC National Committees). The object of the IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in
addition to other activities, the IEC publishes International Standards. Their preparation is entrusted to technical
committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory
work. International, governmental and non-governmental organizations liaising with the IEC also participate in this
preparation. The IEC collaborates closely with the International Organization for Standardization (ISO) in
accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form of
standards, technical specifications, technical reports or guides and they are accepted by the National Committees
in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any divergence
between the IEC Standard and the corresponding national or regional standard shall be clearly indicated in the
latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of
patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60728-10 has been prepared by TA 5: Cable networks for television
signals, sound signals and interactive services, of IEC technical committee 100: Audio, video and
multimedia systems and equipment.
The text of this standard is based on the following documents:
FDIS Report on voting
100/200/FDIS 100/224/RVD
Full information on the voting for the approval of this standard can be found in the report on voting

indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 3.
Annex A is for information only.
Annex B forms an integral part of this standard.
The committee has decided that the contents of this publication will remain unchanged until 2003.
At this date, the publication will be
reconfirmed;
withdrawn;
replaced by a revised edition, or
amended.
A bilingual version of this standard may be issued at a later date.

– 4 – 60728-10  IEC:2001(E)
INTRODUCTION
Standards of the IEC 60728 series deal with cable networks for television signals, sound signals

and interactive services including equipment for:

– head-end -reception, processing and distribution of television and sound signals and their

associated data signals;
– processing, interfacing and transmitting all kinds of signals for interactive services using all

applicable transmission media.

They apply to all kinds of networks such as:

– CATV-systems;
– MATV-systems and SMATV-systems;
– individual receiving systems and
– all kinds of equipment installed in such systems.
The extent of this standardization work is from the antennas and special signal source inputs to
the head-end or other interface points to the network up to the system outlet or, where no system
outlet exists, the terminal input.
The standardization of any user terminals (i.e. tuners, receivers, decoders, multimedia terminals,
etc.) is excluded.
60728-10  IEC:2001(E) – 5 –
CABLED DISTRIBUTION SYSTEMS FOR TELEVISION

AND SOUND SIGNALS –
Part 10: System performance of return path

1 Scope
This part of IEC 60728 deals 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, for
example for NMS or other control, monitoring and signalling purposes. Applications below 5 MHz are not covered by
this standard.
An active return path typically carries only return signals. A passive return path can be used for
both return and forward signals.
This part of IEC 60728 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 have to 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.
The other reference point is the input of the return signal receiver (or transceiver). At this point the
transparent signal path ends and beyond this point the signal is treated in a non-transparent way.
The return signal receiver can be situated at the head-end 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
IEC  330/01
Figure 1 – Reference points of an active return path system (example)

– 6 – 60728-10  IEC:2001(E)
In addition to the system performance requirements for the transparent return path, system

performance recommendations are laid down in this part of IEC 60728, for example 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

standardized in the relevant equipment standards, parts 3 to 6 of the IEC 60728 series.

Transmission systems are not within the scope of this part of IEC 60728.

2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this part of IEC 60728. For dated references, subsequent amendments to,
or revisions of, any of these publications do not apply. However, parties to agreements based on
this part of IEC 60728 are encouraged to investigate the possibility of applying the most recent
editions of the normative documents indicated below. For undated references, the latest edition of
the normative document referred to applies. Members of IEC and ISO maintain registers of
currently valid International Standards.
IEC 60728-1, Cabled distribution systems for television and sound signals – Part 1: Systems
primarily intended for sound and television signals operating between 30 MHz and 1 GHz
IEC 60728-3, Cabled distribution systems for television and sound signals – Part 3: Active coaxial
wideband distribution equipment
IEC 60728-4, Cabled distribution systems for television and sound signals – Part 4: Passive
coaxial wideband distribution equipment
IEC 60728-5, Cable networks for television signals, sound signals and interactive services –
Part 5: Head-end equipment
IEC 60728-6, Cable networks for television signals, sound signals and interactive services –
Part 6: Optical equipment
IEC 60728-11, Cabled distribution systems for television and sound signals – Part 11: Safety
EN 50083, Cable networks for television signals, sound signals and interactive services
EN 50083-2, Cable networks for television signals, sound signals and interactive services – Part

2: Electromagnetic compatibility for equipment
ETS 300 800:July 1998, Digital Video Broadcasting (DVB); Interaction channel for Cable TV
distribution systems (CATV)
ITU-T Recommendation J.61, Transmission performance of television circuits designed for use in
international connections
ITU-R Recommendation BT.470, Conventional television systems

60728-10  IEC:2001(E) – 7 –
3 Terms, definitions, symbols and abbreviations

For the purpose of this part of IEC 60728, the following terms, definitions, symbols and

abbreviations apply.
3.1 Terms and definitions
3.1.1
broadcast signal
signal comprising video and/or audio and/or data content which is distributed to several receivers

simultaneously
3.1.2
downstream direction
direction of signal flow in a cable network from the head-end or any other central point (node) of a
cable network to the subscribers’ area
3.1.3
forward path (downstream)
part of a cable network by which signals are distributed in the downstream direction from the
head-end or any other central point (node) of a cable network to the subscribers’ area
3.1.4
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
3.1.5
head-end
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 head-end may, for example, comprise antenna amplifiers, frequency converters, combiners, separators
and generators.
3.1.6
hybrid fibre coaxial (HFC) network
cable network which comprises optical equipment and cables and coaxial equipment and cables in
different parts
3.1.7
impulse noise
noise caused by electromagnetic interference into cable networks. Impulse noise is characterized
by pulses with a duration of typically <10 μs
3.1.8
ingress noise
noise 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
3.1.9
interaction path
part of a cable network by which interactive signals are transmitted in the downstream direction
(from the head-end or node to the subscriber) and in the upstream direction (from the subscriber
to the head-end or node)
– 8 – 60728-10  IEC:2001(E)
3.1.10
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

3.1.11
multiple interference
interfering signal which consists of two or more signals which originate from two or more sources

NOTE On the return path the multiple interference consists of ingress noise and intermodulation distortion products.

3.1.12
multimedia signal
signal comprising two or more different media contents, for example video, audio, text, data, etc.
3.1.13
network management system (NMS)
software based system for controlling and supervising cable networks
3.1.14
network segment
part of a cable network comprising a set of functions and/or a specific extent of the complete
cable network
3.1.15
network termination
electrical termination of a cable network at any outlet on subscribers' side and head-end or node
side
3.1.16
node
central point of a network segment at which signals can be fed into the forward path or can be
gathered from a number of subscribers out of the return path
3.1.17
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 head-end or any other central point (node) of a cable
network
3.1.18
upstream direction
direction of signal flow in a cable network from a subscriber to the head-end or any other central
point (node) of a cable network

60728-10  IEC:2001(E) – 9 –
3.2 Symbols
Symbol Term Symbol Term
O
BER
Optical receiver Bit error rate detector
E
Test waveform generator Passive distribution network

SUT
System under test Oscilloscope
Demodulator Low pass
Amplifier with return path amplifier
High pass
Modulator
3.3 Abbreviations
BER bit error rate
BW bandwidth, equivalent noise bandwidth
community antenna television
CATV
CB citizens' band
carrier-to-multiple interference ratio
C/MI
C/N carrier-to-noise ratio
EMC electromagnetic compatibility
frequency modulation
FM
FSK frequency shift keying
HFC hybrid fibre coaxial
intermediate frequency
IF
ISM industrial, scientific, medical
MATV master antenna television (network)
network management system
NMS
OFDM orthogonal frequency division multiplexing
PRBS pseudo random binary sequence

– 10 – 60728-10  IEC:2001(E)
quadrature amplitude modulation
QAM
QPSK quaternary phase shift keying

RF radio frequency
root mean square
RMS
RBW resolution bandwidth
signal level, before corrections
S
SL signal level (corrected)
SMATV satellite master antenna television (network)

signal-to-noise ratio
S/N
SUT system under test
TS transport stream
television
TV
4 Methods of measurement
4.1 Set-up of the network
Although the main purpose of this part of IEC 60728 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.
The following set-up and operational procedures provide guidelines.
The return path differs in several ways from the forward path, even though they mostly share the
same physical network. Table 1 gives some indications.
Table 1 – Characterization 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 differ from those used in the downstream direction.
One major difference is that the amplifiers in the downstream direction are aligned by adjusting
their output signals to predetermined levels and in the return direction the network is adjusted so
that the input signals from different sources are equalized at the amplifier input. Different types of
signals may be at different levels.
4.1.1 Steps to set up the upstream properly
Figure 2 gives a rough procedure for the set-up.

60728-10  IEC:2001(E) – 11 –
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
head end, 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 head end,
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 head end
at the head end
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 head
at the optical transmitter or at the end is according to step 1
head end is according to step 1
7. 5.
Continue with the following Continue with the following
amplifier in the downstream direction amplifier in the downstream
direction
IEC  331/01
Figure 2 – Procedure for set-up and adjustment of the upstream system
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 analyzer having a known noise bandwidth and a calibrated
display. The calibration accuracy should be preferably within 0,5 dB.

– 12 – 60728-10  IEC:2001(E)
4.2.3 Connection of the equipment

Connect the measuring equipment to the point where the measurement is to be performed by

using a suitable connection lead. Ensure correct impedance matching.

4.2.4 Measurement procedure for RF signals without carriers

4.2.4.1 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.

4.2.4.2 Tune the spectrum analyzer to the channel that is to be measured (by selecting the
centre frequency of the spectrum analyzer) 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 0.288 Mbit/s 0,1875
QPSK 0.576 Mbit/s 0,375
QPSK 1.152 Mbit/s 0,750
QPSK 1,544 Mbit/s 0,772
QPSK 2.304 Mbit/s 1,5000
QPSK 3,088 Mbit/s 1,544
QPSK 4.608 Mbit/s 3,000
16 QAM 12,8 Mbit/s 3,2000
4.2.4.3 Set the resolution bandwidth (RBW) of the spectrum analyzer 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.
4.2.4.4 Measure the signal level (S) at the centre frequency of the channel in dB(μV).

4.2.4.5 Measure the –3 dB frequencies of the channel. The difference between these two
frequencies is assumed to be the equivalent signal bandwidth (BW).
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.
4.2.4.6 Calculate the signal level (SL) by using the 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 analyzer is about 1,7 dB.

60728-10  IEC:2001(E) – 13 –
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
4.3.1 Under consideration
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 IEC 60728-1. The same
method can also be used on the return path for signals which have a clear carrier. The noise
bandwidth which is applicable for the channel under test shall be used.
This part of IEC 60728 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 minimize 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 analyzer 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 is to be performed by
using a suitable connection lead. Ensure correct impedance matching.
4.4.4 Measurement procedure
4.4.4.1 Tune the spectrum analyzer to the channel that is to be measured (by selecting the
centre frequency of the spectrum analyzer) and select the span and level settings to show the
whole channel.
4.4.4.2 Set the resolution bandwidth (RBW) of the spectrum analyzer 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.
4.4.4.3 Read the level of the signal (S) at the centre frequency of the channel.

– 14 – 60728-10  IEC:2001(E)
4.4.4.4 Switch-off the channel at the input of the system or by te
...