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DS-information
DS/CLC/TS 50083-3-3:2014
1. udgave 2014-11-19
Kabelnetværk til tv-signaler, lydsignaler og
interaktive anvendelser – Del 3-3: Aktivt bredbåndsudstyr til kabelnetværk – Metoder til måling af det maksimale driftsudgangsniveau i returvejen
Cable networks for television signals, sound signals and interactive services – Part 3-3: Active wideband equipment for cable networks – Methods of measurement of the maximum operating output level in the return path
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TECHNICAL SPECIFICATION
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
CLC/TS 50083-3-3
November 2014
ICS 33.060.40
English Version
Cable networks for television signals, sound signals and interactive services - Part 3-3: Active wideband equipment for cable networks - Methods of measurement of the maximum
operating output level in the return path
Réseaux de distribution par câbles pour signaux de télévision, signaux de radiodiffusion sonore et services
interactifs - Partie 3-3: Matériel actifs à large bande utilisés dans les réseaux de distribution - Méthodes de mesure du
niveau de sortie maximal de fonctionnement dans la voie de retour
Kabelnetze für Fernsehsignale, Tonsignale und interaktive Dienste - Teil 3-3: Aktive Breitbandgeräte für Kabelnetze -
Messverfahren für den maximalen Betriebs-Ausgangspegel im Rückweg
This Technical Specification was approved by CENELEC on 2014-09-30. CENELEC members are required to announce the existence of this TS in the same way as for an EN and to make the TS available promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force. CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2014 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. CLC/TS 50083-3-3:2014 E
CLC/TS 50083-3-3:2014 - 2 -
Contents Page
Foreword............................................................................................................................................................. 3
Introduction ........................................................................................................................................................ 4
1 Scope ..................................................................................................................................................... 5
2 Normative references ........................................................................................................................... 5
3 Terms, definitions, symbols and abbreviations ................................................................................ 5
3.1 Terms and definitions .......................................................................................................................... 5
3.2 Symbols ................................................................................................................................................. 7
3.3 Abbreviations ........................................................................................................................................ 8
4 Method of measurement of the maximum operating output level in the return path .................... 8
4.1 General................................................................................................................................................... 8
4.1.1 Channel load and modulation format ................................................................................................. 8
4.1.2 Return path frequency ranges ............................................................................................................ 8
4.1.3 Applied limit values .............................................................................................................................. 8
4.2 Measurement parameters for full channel load (N = 6 or N = 8) ...................................................... 9
4.3 Equipment required .............................................................................................................................. 9
4.4 Connection of the equipment ............................................................................................................ 10
4.5 Measurement procedure .................................................................................................................... 10
4.6 Presentation of the measurement results ........................................................................................ 11
4.7 Maximum operating output level for reduced channel loads ........................................................ 11
Annex A (normative) Null packet and PRBS definitions ............................................................................ 12
A.1 Null packet definition ......................................................................................................................... 12
A.2 PRBS definition ................................................................................................................................... 13
Annex B (informative) Calculation formula for the maximum operating output level for reduced channel loads ...................................................................................................................................... 14
B.1 General................................................................................................................................................. 14
B.2 Measurement results as basis for calculation formula for reduced channel loads .................... 14
B.3 Calculation formula for median value .............................................................................................. 15
B.4 Calculation formula for worst-case value ........................................................................................ 15
Bibliography ..................................................................................................................................................... 16
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Foreword
This document (CLC/TS 50083-3-3:2014) has been prepared by CLC/TC 209 “Cable networks for television signals, sound signals and interactive services”.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent rights.
CLC/TS 50083-3-3:2014 - 4 -
Introduction
Standards and deliverables of EN 60728 series and EN 50083 series deal with cable networks including equipment and associated methods of measurement for headend reception, processing and distribution of television and sound signals and for processing, interfacing and transmitting all kinds of data signals for interactive services using all applicable transmission media. These signals are typically transmitted in networks by frequency-multiplexing techniques.
This includes for instance
• regional and local broadband cable networks,
• extended satellite and terrestrial television distribution systems,
• individual satellite and terrestrial television receiving systems,
and all kinds of equipment, systems and installations used in such cable networks, distribution and receiving systems.
The extent of this standardization work is from the antennas and/or special signal source inputs to the headend or other interface points to the network up to the terminal input of the customer premises equipment.
The standardization work will consider coexistence with users of the RF spectrum in wired and wireless transmission systems.
The standardization of any user terminals (i.e. tuners, receivers, decoders, multimedia terminals etc.) as well as of any coaxial, balanced and optical cables and accessories thereof is excluded.
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1 Scope
This Technical Specification is applicable to the method of nonlinearity measurement for active cable network equipment which carry a digital channel load in the return path. The digital channel load is represented by standard DVB-C signals. The method of measurement of the maximum operating output level takes account of a full channel load in the return path frequency range although different applications of return path amplifiers with partial channel load or single channel load are also in practical use. The maximum operating output level for applications with reduced channel loads could be derived from the result with a full channel load by applying a given calculation formula.
The method considers the specific signal form and behaviour of digitally modulated signals and can be applied in the return path frequency range (5 MHz to 65 MHz) as well as in the extended return path frequency range (5 MHz to 85 MHz) according to EN 60728-10.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
EN 60728-10, Cable networks for television signals, sound signals and interactive services – Part 10: System performance for return paths (IEC 60728-10)
ISO/IEC 13818-1, Information technology — Generic coding of moving pictures and associated audio information: Systems — Part 1
3 Terms, definitions, symbols and abbreviations
For the purposes of this document, the following terms, definitions, symbols and abbreviations apply.
3.1 Terms and definitions
3.1.1 attenuation ratio of the input power to the output power of an equipment or system, usually expressed in decibels
3.1.2 bit error ratio BER ratio between erroneous bits and the total number of transmitted bits
3.1.3 gain ratio of the output power to the input power, usually expressed in decibels
3.1.4 level decibel ratio of any power P1 to the standard reference power P0, i.e
0
1lg10PP
decibel ratio of any voltage U1 to the standard reference voltage U0, i.e
0
1lg20UU
Note 1 to entry: The power level may be expressed in decibels relative to P0 = (U02/R) = (1/75) pW, i.e. in dB(P0), taking into
account that the level of P0 corresponds to 0 dB(P0) or, as more usually, in dB(pW), taking into account that the level of P0 corresponds to –18,75 dB(pW). The voltage level is expressed in decibels relative to 1 μV (across 75 Ω), i.e. in dB(μV).
CLC/TS 50083-3-3:2014 - 6 -
3.1.5 maximum operating output level (worst-case) Umax (N) worst-case of maximum channel output level of a digitally modulated signal in the 64 QAM format with a symbol rate of 6,9 MSymb/s with 15 % cosine roll-off, measured with full digital channel load
3.1.6 maximum operating output level Umax,i (N) measured maximum operating output level of a single measurement channel i with full digital channel load
3.1.7 modulation error ratio MER sum of the squares of the magnitudes of the ideal symbol vectors is divided by the sum of the squares of the magnitudes of the symbol error vectors of a sequence of symbols, the result being expressed as a power ratio in dB
( )
( )dBin
δδ
lg10
1
22
1
22
+
+
=
∑
∑
=
=N
jjj
N
jjj
QI
QI
MER
3.1.8 modulation error ratio of EUT MEREUT calculated value of modulation error ratio of the EUT following Figure 1 and using the following formula
Figure 1 − Interrelation between different MER contributions
Meas Source10 10
EUT 10 lg 10 10MER MER
MER− −
= − −
Note 1 to entry: The calculation with 10⋅lg is used for simplification reasons although it is well known that the disturbing signal comprises of noise and nonlinear portions.
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3.1.9 modulation error ratio of complete measurement setup MERMeas measured value of modulation error ratio of the complete measurement setup according to Figure 1 including the equipment under test (EUT)
3.1.10 modulation error ratio of signal source MERSource measured value of modulation error ratio of the signal generator when signal generator and measurement receiver are directly connected
3.1.11 slope difference in gain or attenuation at two specified frequencies between any two points in an equipment or system
Note 1 to entry: The slope sign is considered
a) negative when the attenuation increases with frequency (cables) or the gain (amplifiers) decreases with frequency,
b) positive when the gain (amplifiers) increases with frequency (compensating slope).
3.2 Symbols
The following graphical symbols are used in the figures of this Technical Specification. These symbols are either listed in IEC 60617 or based on symbols defined in IEC 60617.
Symbols Terms Symbols Terms
Equipment Under Test based on [IEC 60617-S00059 (2001–07)]
Combiner based on [IEC 60617-S00059 (2001–07)]
Variable attenuator [IEC 60617-S01245 (2001–07)]
Amplifier [IEC 60617-S01239 (2001–07]
Modulator [IEC 60617-S01278 (2001–07)]
Demodulator [IEC 60617-S01278 (2001–07]
CLC/TS 50083-3-3:2014 - 8 -
3.3 Abbreviations
BER bit error ratio
BERSource bit error ratio of source and measurement equipment
BERMess measured bit error ratio value on measuring set
DOCSIS Data Over Cable Service Interface Specification
DVB Digital Video Broadcasting
DVB-C Digital Video Broadcasting, Cable
EUT equipment under test
MER modulation error ratio
MEREUT modulation error ratio of EUT
MERMeas modulation error ratio of complete measurement setup
MERSource modulation error ratio of signal source
PRBS pseudo-random bit sequence
QAM quadrature amplitude modulation
RF radio frequency
Umax (N) worst-case of maximum operating output level with channel load of N carriers in the 64 QAM format
Umax,i (N) measured maximum operating output level of a single measurement channel i with N channels load
Un Calculated output level for n channels
4 Method of measurement of the maximum operating output level in the return path
4.1 General
4.1.1 Channel load and modulation format
The method of measurement describes the measurement of the bit error ratio (BER) (before Reed Solomon decoder of the measurement receiver) of the output signal of the equipment under test (EUT) (e.g. a return path amplifier) when handling a full load of digitally modulated DVB-C signals.
To simplify matters, DVB-C signals are used to simulate DOCSIS signals (according to e.g. ETSI EN 302 878, all parts) usually used in cable networks for data transmission purposes.
4.1.2 Return path frequency ranges
The method of measurement is applicable in the return path frequency range (5 MHz to 65 MHz) as well as in the extended return path frequency range (5 MHz to 85 MHz) according to EN 60728-10.
For EUT designed for the return path frequency range (5 MHz to 65 MHz), this test is able to define the performance (maximum output level) of the EUT when loaded with a number N = 6 of digitally modulated signals in the 64 QAM format covering a maximum frequency range from 16 MHz to 64 MHz for full channel load with a raster of 8 MHz.
For EUT designed for the extended return path frequency range (5 MHz to 85 MHz), this test is able to define the performance (maximum output level) of the EUT when loaded with a number N = 8 of digitally modulated signals in the 64 QAM format covering a maximum frequency range from 16 MHz to 80 MHz for full channel load with a raster of 8 MHz.
4.1.3 Applied limit values
The maximum operating output level is defined for a limit value of the bit error ratio BER ≤ 1 × 10−8. This limit value corresponds with correct operation and a good quality output of the EUT.
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In addition to this BER limit value, a limit value for the modulation error ratio of MEREUT > 35 dB shall be achieved according to the definition in 3.1.7. This limit value is above the minimum system requirement for 64 QAM signals which is MER > 26 dB and allows a margin to cascade several active equipment in the return path.
The measurements shall be performed using the measurement parameters as described hereafter.
4.2 Measurement parameters for full channel load (N = 6 or N = 8)
The measurement parameters for full channel load are given in Table 1.
Table 1 ‒ Measurement parameters for full channel load
Return path frequency range (5 MHz to 65 MHz)
Extended return path frequency range (5 MHz to
85 MHz)
Modulation format 64 QAM
Symbol rate 6,9 MSymb/s
Channel bandwidth 8 MHz
Number of channels N 6 8
Channel raster with centre frequencies
20, 28, 36, 44, 52 and 60 MHz 20, 28, 36, 44, 52, 60, 68 and 76 MHz
BER limit value ≤ 1⋅10−8
MEREUT limit value > 35 dB
One channel (i) is taken as the measurement channel and the remaining five or seven channels are for load. The measurement channel shall be varied through all six (eight) channels.
The worst-case value of Umax,i (N) of the EUT out of the measured values of the different measurement channels shall be presented as Umax (N).
4.3 Equipment required
The equipment required is as follows:
a) a number N of 64 QAM modulators (with channel coders) having a suitable linearity (BER better than 1 × 10−10 and MER > 40 dB) and an occupied bandwidth of 8 MHz.
b) a number N of null packet or of pseudo-random bit sequence (PRBS) generators (see Annex A);
c) a combiner for the output signals of the 64 QAM modulators with negligible distortion;
d) a wide band amplifier with suitable linearity and gain over the full bandwidth of the EUT;
e) precision attenuators (1 dB steps) to be placed in front of and behind the EUT;
f) a test receiver able to measure the BER of the received 64 QAM signals; where the receiver’s distortion performance should be sufficiently lower than that to be measured (e.g. a BER better than 1 × 10−10);
g) a test receiver able to measure the MER of the received 64 QAM signals; where the receiver’s own MER should be sufficiently better than that to be measured (e.g. MER > 40 dB).
All applied QAM channels (load channels and measurement channels) shall have the same output level within a deviation of a maximum of ± 0,5 dB.
The total BERSource introduced by source and measurement equipment shall not exceed 1 × 10−10.
CLC/TS 50083-3-3:2014 - 10 -
4.4 Connection of the equipment
Connect the measuring equipment as indicated in Figure 2. The input signal is applied to the equipment under test (EUT) input and its output signal level is measured by means of a suitable measuring receiver, connected to a BER measuring set if not included in the measuring receiver itself.
In addition, an MER measuring set shall be provided and connected to the output of the measuring receiver to measure the output signal level either in relation to a fixed MER limit value or to measure MER in correspondence to the fixed BER limit value.
NOTE The measuring receivers for BER measurements and for MER measurements could be combined in one measuring set.
Figure 2 – BER/MER measurement test configuration
4.5 Measurement procedure
The measurement shall be performed according to the steps described hereafter.
a) Tune the measuring receiver to an operating channel.
b) Measure the performance of the test configuration by connecting the output of the variable attenuator A directly to the input of the variable attenuator B, Reduce the attenuation of the variable attenuator A to 0 dB and set the variable attenuator B to a value that allows the best performance of the measuring receiver in terms of BERSource (<1 × 10−10 measured over an observation time > 10 min). Note the level of the signal applied to the measuring receiver and the BER value obtained.
c) Measure the MERSource performance of the test configuration. A value of > 40 dB shall be achieved.
d) Connect the EUT between the variable attenuator A and the variable attenuator B.
e) The EUT shall be operated at nominal gain and with nominal slope. All settings (variable gain and/or slope) shall be set to zero.
f) Using the variable attenuator A, set the channel output signal level of the EUT to a value at least 10 dB lower than the expected maximum value. Set the variable attenuator B so as to obtain the previously determined optimum signal level at the input of the measuring receiver.
g) Read the BERMeas on the measuring set, which shall be ≤ 1 × 10−8 (measured over an observation time > 60 s). Read the MERMeas on the measuring set, which shall be > 35 dB.
h) Using the attenuator A, increase the output level of all applied channels by 1 dB and set the variable attenuator B so as to obtain the previously determined optimum signal level at the input of the measuring receiver.
i) Repeat procedures g) and h) until the BER measuring set shows a value > 1 × 10−8 or the MER measuring set shows a value < 35 dB.
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j) Now reduce the output level of all applied channels by 1 dB and set the variable attenuator B so as to obtain the previously determined optimum signal level at the input of the measuring receiver.
k) Read the BERMeas on the measuring set which once more shall be ≤ 1 × 10−8 (measured over an observation time of > 60 s) and the MERMeas which shall be > 35 dB and, if not, repeat step j.
l) Note the output level Umax,i (N) of the EUT which represents the maximum operating output level of the EUT at channel i and calculate the corresponding MEREUT according to 3.1.8.
This procedure shall be repeated for each channel as defined in 4.2. The worst case (lowest value of the maximum operating output level) shall be determined as Umax (N).
4.6 Presentation of the measurement results
The worst-case value of the maximum operating output level Umax (N) of the EUT, with N channels applied (N = 6 or N = 8) and expressed in dB(µV), as defined in 4.1 shall be published.
If the N test channels are applied to an amplifier with frequency slope, the same method of measurement can be applied as for amplifiers without frequency slope. However, in this case, the maximum operating output level of the EUT shall be stated for the highest measurement channel, taking into account the relative slope value (slope value difference) between the worst-case channel and the highest measurement channel.
The frequency response (slope) of the EUT used for the measurements shall be published.
The MEREUT for the worst-case channel of the EUT shall be published.
4.7 Maximum operating output level for reduced channel loads
Annex B gives a calculation formula for the maximum operating output levels for reduced channel loads, e.g. partial channel load with 3 channels and single channel load with only one channel in the return path.
CLC/TS 50083-3-3:2014 - 12 -
Annex A (normative)
Null packet and PRBS definitions
A.1 Null packet definition
The null packet definition from ISO/IEC 13818-1 is extended for the purpose of the recommended test mode.
ISO/IEC 13818-1 defines a null transport stream packet for the purpose of date rate stuffing.
Table A.1 shows the structure of a null transport stream packet using the method of describing bit stream syntax defined in 2.4 of ISO/IEC 13818-1.
This description is derived from Table 2-2 in ISO/IEC 13818-1. The abbreviation “bslbf” means “bit string, left bit first”, and “uimsbf” means “unsigned integer, most significant bit first”.
The column titled “Value”, gives the bit sequence for the recommended null packet.
A null packet is defined by ISO/IEC 13818-1 as having
payload_unit_start_indicator = '0';
PID = 0x1FFF;
transport_scrambling_control = '00';
adaptation_field_control value = '01'. This corresponds to the case “no adaptation field, payload only”.
The remaining fields in the null packet that shall be defined for testing purposes are:
transport_error_indicator which is '0' unless the packet is corrupted: for testing purposes this bit is defined as '0' when the packet is generated;
transport_priority which is not defined by ISO/IEC 13818-1 for a null packet. For testing purposes this bit is defined as '0';
continuity_counter which ISO/IEC 13818-1 states is undefined for a null packet. For testing purposes this bit field is defined as '0000';
data_byte which ISO/IEC 13818-1 states may have any value in a null packet. For testing purposes this bit field is defined as '00000000'.
- 13 - CLC/TS 50083-3-3:2014
Table A.1 – Null-transport-stream packet definition
Syntax No of bits Identifier Value
null_transport_packet(){ sync_byte transport_error_indicator payload_unit_start_indicator transport_priority PID transport_scrambling_control adaptation_field_control continuity_counter for (i = 0;i < N;i++){data_byte} }
8 1 1 1 13 2 2 4 8
bslbf bslbf bslbf bslbf
uimsbf bslbf bslbf
uimsbf bslbf
'0960111' '0' '0' '0'
'1111111111111' '00' '01'
'0000' '00000000'
A.2 PRBS definition
A PRBS (pseudo random bit sequence) generator can be used instead of a null packet generator. A PRBS of 1023 – 1 inverted is recommended.
CLC/TS 50083-3-3:2014 - 14 -
Annex B (informative)
Calculation formula for the maximum operating output level
for reduced channel loads
B.1 General
In special cases, it may be of interest to specify the maximum operating output level for an active return path equipment which is only operated with a reduced number of channels. These cases were investigated by applying the method of measurement described in Clause 4 and using only a reduced number of return path channels. The following two cases were considered:
• Partial channel load with three channels (one measurement and two load channels), one at the lower edge, one in the middle and one at the upper edge of the return path frequency band and occupied with 64-QAM DVB-C signals.
• Single channel load using one 8-MHz channel occupied with 64-QAM DVB-C signal.
B.2 Measurement results as basis for calculation formula for reduced channel loads
The results of measurements with a large number of return path amplifiers applying the methods for full, partial and single channel loads are shown in Figure B.1. From this array of curves, a calculation formula can be derived allowing the calculation of the maximum operating output level for partial and single channel load from the measurement result achieved with full channel load.
Figure B.1 − Results of measurements with full, partial and single channel load
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B.3 Calculation formula for median value
The median value of the maximum operating output level for partial channel load and single channel load could be calculated using the following formula:
( ) 14 )/( lg n max NU U N n= + ×
where
Un Calculated operating output level for n channels (median value)
Umax (N) Worst-case of maximum operating output level for N channels
N Number of measurement and load channels (N = 6 or N = 8)
n Number of reduced channels for partial or single channel load (n ≤ N) Table B.1 shows an example for the corresponding median values of the maximum operating output level
Table B.1 − Calculated median values
Level/dB(μV) Number of channels
Umax (6) 112,0 6
U3 116,2 3
U1 122,9 1
B.4 Calculation formula for worst-case value
The worst-case value of the maximum operating output level for partial channel load and single channel load could be calculated using the following formula:
( ) 10 )/( n max NU U lg N n= + ×
where
Un Calculated output level for n channels
Umax (N) Worst-case of maximum operating output level for N channels
N Number of measurement and load channels (N = 6 or N = 8)
n Number of reduced channels for partial or single channel load (n ≤ N) Table B.2 shows an example for the corresponding worst-case values of the maximum operating output level.
Table B.2 − Calculated worst-case values
Level/dB(μV) Number of channels
Umax (6) 112 6
U3 115,0 3
U1 119,8 1
CLC/TS 50083-3-3:2014 - 16 -
Bibliography
IEC 60617, Graphical symbols for diagrams
EN 60728-3, Cable networks for television signals, sound signals and interactive services - Part 3: Active wideband equipment for cable networks (IEC 60728-3)
ETSI EN 302 878, Access, Terminals, Transmission and Multiplexing (ATTM); Third Generation Transmission Systems for Interactive Cable Television Services - IP Cable Modems
