EN 60835-1-4:1995
(Main)Methods of measurement for equipment used in digital microwave radio transmission systems - Part 1: Measurements common to terrestrial radio-relay systems and satellite earth stations - Section 4: Transmission performance
Methods of measurement for equipment used in digital microwave radio transmission systems - Part 1: Measurements common to terrestrial radio-relay systems and satellite earth stations - Section 4: Transmission performance
Deals with the measurement of transmission performance and applies to simulated digital microwave transmission systems or sub-systems.
Meßverfahren für Geräte in digitalen Mikrowellen-Funkübertragungssystemen - Teil 1: Messungen an terrestrischen Richtfunksystemen und Satelliten-Erdfunkstellen - Hauptabschnitt 4: Übertragungsqualität
Méthodes de mesure applicables au matériel utilisé pour les systèmes de transmission numérique en hyperfréquence - Partie 1: Mesures communes aux faisceaux hertziens terrestres et aux stations terriennes de télécommunications par satellite - Section 4: Qualité de transmission
Traite de la mesure de la qualité de transmission des systèmes ou sous-systèmes de transmission numérique en hyperfréquence en condition de fonctionnement simulé.
Methods of measurement for equipment used in digital microwave radio transmission systems - Part 1: Measurements common to terrestrial radio-relay systems and satellite earth stations - Section 4: Transmission performance (IEC 60835-1-4:1992)
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Standards Content (Sample)
SLOVENSKI STANDARD
01-oktober-2002
Methods of measurement for equipment used in digital microwave radio
transmission systems - Part 1: Measurements common to terrestrial radio-relay
systems and satellite earth stations - Section 4: Transmission performance (IEC
60835-1-4:1992)
Methods of measurement for equipment used in digital microwave radio transmission
systems -- Part 1: Measurements common to terrestrial radio-relay systems and satellite
earth stations -- Section 4: Transmission performance
Meßverfahren für Geräte in digitalen Mikrowellen-Funkübertragungssystemen -- Teil 1:
Messungen an terrestrischen Richtfunksystemen und Satelliten-Erdfunkstellen --
Hauptabschnitt 4: Übertragungsqualität
Méthodes de mesure applicables au matériel utilisé pour les systèmes de transmission
numérique en hyperfréquence -- Partie 1: Mesures communes aux faisceaux hertziens
terrestres et aux stations terriennes de télécommunications par satellite -- Section 4:
Qualité de transmission
Ta slovenski standard je istoveten z: EN 60835-1-4:1995
ICS:
33.060.30 Radiorelejni in fiksni satelitski Radio relay and fixed satellite
komunikacijski sistemi communications systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
NORME CEI
INTERNATIONALE IEC
60835-1-4
INTERNATIONAL
Première édition
STAN DARD
First edition
1992-04
Méthodes de mesure applicables au matériel
utilisé pour les systèmes de transmission
numérique en hyperfréquence
Partie 1:
Mesures communes aux faisceaux hertziens
terrestres et aux stations terriennes de
télécommunications par satellite
Section 4: Qualité de transmission
Methods of measurement for equipment used in
digital microwave radio transmission systems
Part 1:
Measurements common to terrestrial radio-relay
systems and satellite earth stations
Section 4: Transmission performance
© IEC 1992 Droits de reproduction réservés — Copyright - all rights reserved
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835-1-4 ©I EC – 3 –
CONTENTS
Page
FOREWORD 5
INTRODUCTION 7
Clause
1 Scope 9
2 Bit error ratio 9
2.1 Definition and general considerations 9
2.2 Method of measurement 11
2.3 Presentation of results 13
2.4 Details to be specified 13
3 Additional parameters 13
4 Timing jitter 13
4.1 Definition and general considerations 13
4.2 Method of measurement 15
4.3 Presentation of results 15
4.4 Details to be specified 17
5 Acceptable input interruption 17
5.1 Definition and general considerations 17
5.2 Method of measurement 19
5.3 Presentation of results 19
5.4 Details to be spec ified 19
Figures 20
Annex A – Bibliography 25
835-1-4 ©IEC — 5 —
INTERNATIONAL ELECTROTECHNICAL COMMISSION
METHODS OF MEASUREMENT FOR EQUIPMENT USED IN
DIGITAL MICROWAVE RADIO TRANSMISSION SYSTEMS
Part 1: Measurements common to terrestrial radio-relay systems
and satellite earth stations
Section 4: Transmission performance
FOREWORD
1)
The formal decisions or agreements of the IEC on technical matters, prepared by Technical Committees on
which all the National Committees having a special interest therein are represented, express, as nearly as
possible, an international consensus of opinion on the subjects dealt with.
2) They have the form of recommendations for international use and they are accepted by the National
Committees in that sense.
3)
In order to promote international unification, the IEC expresses the wish that all National Committees
should adopt the text of the IEC recommendation for their national rules in so far as national conditions will
permit. Any divergence between the IEC recommendation and the corresponding national rules should, as
far as possible, be clearly indicated in the latter.
This section of International Standard IEC 835-1 has been prepared by Sub-
Committee 12E: Radio relay and fixed satellite communications systems, of IEC Technical
Committee No. 12: Radiocommunications.
The text of this section is based on the following documents:
DIS Report on Voting
12E(CO)136
12E(CO)140
Full information on the voting for the approval of this section can be found in the Voting
Repo rt indicated in the above table.
Annex A is for information only.
835-1-4©IEC – 7 –
INTRODUCTION
The transmission performance of a digital transmission system is expressed by several
parameters, such as bit-error ratio (BER), jitter and acceptable input interruption.
The BER
is the most important parameter related to system transmission pe rformance.
Parameters other than the BER,
for example, error-free seconds, are applicable to trans-
mission rates up to 64 kbit/s. Their application to higher bit rates is under consideration
(see [2]*).
References in brackets are given in annex A: Bibliography.
835-1-4 © I EC — 9 —
METHODS OF MEASUREMENT FOR EQUIPMENT USED IN
DIGITAL MICROWAVE RADIO TRANSMISSION SYSTEMS
Part 1: Measurements common to terrestrial radio-relay systems
and satellite earth stations
Section 4: Transmission performance
1 Scope
This section of IEC 835-1 deals with the measurement of transmission pe
rformance and is
applicable to simulated digital microwave transmission systems or sub-systems.
The transmission parameters should normally be measured at inte
rface points recom-
mended by the CCITT (see [1]). In special cases when equipment specifications require
measurements at other ports (e.g. between modulator input and demodulator output termi-
nals), interface circuits between the measuring equipment and the equipment under test
may be necessary.
2 Bit error ratio
2.1
Definition and general considerations
The bit-error-ratio, BER,
is defined as follows (see [3]):
Ne _ Ne
BER =
(3-1)
Nt Bto
where:
Ne is the number of bit errors in a time interval
to
Nt
is the total number of transmitted bits in a time interval to
B is the bit-rate of the signal at the point where the measurement is made
to
is the measurement time interval in seconds (error-counting time)
BER
The is measured by comparing, bit by bit, the coincidence, or non-coincidence, of the
transmitted and received bit streams. The arrangement for BER measurement is shown in
figure 1. The comparison of the transmitted and received bit streams is made and the
number of errored bits is counted.
The preferred test signal to be applied to the equipment under test is one having a pseudo-
random pattern with a pattern length of either 2 15-1 or 2 23-1, depending on the nominal
bit-rate of the transmission system (see [4]), but a selectable or programmable word
pattern is sometimes used for testing the effect of specific patterns on the
BER charac-
teristics.
835-1-4 ©I EC - 11 -
Equation (3-1) can give an estimate of the error probability. The accuracy of this estimate
increases as Ne
increases, but the practical limitations of the measurement time interval
usually set a limit to th
e' value of Ne.
Assuming a random distribution of errors independent of each other and with a constant
probability, i.e. according to Poisson's law, the minimum acceptable value of
Ne is approxi-
mately 10. In this case, the true error probability is contained in a range equal to ±50
around NeINt
with a confidence coefficient of 90 % (see [3]).
Depending on the circuit configuration, for example high spectral efficiency systems, the
distribution of errors may be structured. In such cases the minimum acceptable value
of Ne should be correspondingly increased.
The measurement time interval of the BER
needs to be long enough to obtain the required
accuracy. If a BER of n x 10-P
is to be measured on a bit-stream having a bit rate B, the
required measuring time t
° is given by:
N x
10P
t >_ (3-2)
° nB
For example, assuming Ne = 10 and a BER of 10-7
is to be measured at 6,3 Mbit/s, t°
shall be longer than 16 s.
2.2
Method of measurement
The arrangement for the measurement of BER
is shown in figure 1. The measuring instru-
ment has a transmit portion comprising a pseudo-random test-pattern generator, a receive
portion comprising an identical local reference-pattern generator and a comparator for
comparing the received and locally generated reference patterns.
An error counter counts the errors whenever the received and locally generated bits are
not identical, and the ratio of the errored bits to the total number of bits, i.e. the BER, is
displayed by the error counter.
The bit rate of the test pattern is usually selectable to permit the generation of the
hierarchical bit rates given in [1]. However an external clock input is also usually available
for generating non-hierarchical bit rates. The receive pattern generator is normally
synchronized by the clock signal extracted from the incoming bit stream. A
BER measure-
-8
ment range of at least 10
-2 or 10-3 to 10 or 10-9 should be covered. The choice of the
extreme values depends on the hardware configuration and on the digital rate.
In making the test, the demodulator input should be connected and disconnected several
times and the highest measured
BER should be recorded.
When there are two or more baseband channels in the equipment under test, sufficiently
uncorrelated pulse streams need to be applied to the channels and the measurements
made one channel at a time.
The BER
is measured as a function of the specified receiver input conditions as described
in the appropriate sections of parts 2 and 3 of IEC 835.
835-1-4 © I EC — 13 —
2.3
Presentation of results
The BER is expressed as a function of some appropriate parameter of the equipment
being measured, such as receiver input level.
2.4
Details to be specified
The following items should be included, as required, in the detailed equipment speci-
fication:
a) ports between which the measurement is to be made;
main inte
b) rface conditions, e.g. bit rate, level, impedance and coding of the signal;
c) specified receiver input levels, as appropriate;
d)
type and length of the test pattern;
e)
limiting bit error ratio characteristic;
f) measurement time interval or number of errors by measurement.
3 Additional parameters
Additional parameters such as error-free seconds, are under consideration.
4 Timing jitter
4.1 Definition and general considerations
Timing jitter is defined as the short-term deviation of the significant instants of a digital
signal from their ideal positions in time. The jitter as a function of time can be charac-
terized in terms of frequency and amplitude, as shown in the example of figure 2.
Two types of jitter may be distinguished according to the jitter generating process:
Justification jitter —
which is caused by the insertion and extraction of justification bits in
time-division multiplexing and de-multiplexing processes, and
Timing jitter —
which is due to the imperfection of the timing recovery circuits in the
regeneration process. Only timing jitter measurements are of importance for determining
the performance of digital microwave radio transmission systems.
Three timing jitter parameters are normally measured:
i) Output jitter in the absence of input jitter, which is the jitter originating in the
equipment under test.
ii) Maximum tolerable input jitter, which shows the immunity of the equipment under
test to a jittered input signal.
iii)
The jitter transfer function which characterizes the change of jitter amplitude due to
the equipment under test when it is driven by a jittered input signal.
The arrangement for measuring these three jitter parameters is shown in figure 3 (see
also [5]).
835-1-4 ©IEC - 15 -
The transmitter part of the instrument used to produce a jittered pseudo-random bit
sequence comprises a pattern generator driven by a phase-modulated clock signal. This is
accomplished with a modulated clock generator driven by a modulation source. The magni-
tude and the frequency of the phase-modulation is adjustable.
The receiver part of the instrument is a jitter measurement circuit comprising a wide-band
phase detector. This drives a measuring device containing circuits for limiting the
bandwidth of the jitter spectrum. An analogue output is usually provided which supplies
the demodulated jittered waveform for investigation using an oscilloscope, spectrum
analyzer or selective level meter.
The frequency range of the jitter measurement instrument and the associated selectable
high-pass filters for setting the lower limit to the frequency range should be in accordance
with [5].
4.2 Method of measurement
The method of measurement depends upon which of the jitter parameters is to be
measured as follows:
Measurement of output jitter in the absence of input jitter
The phase modulation of the clock generator is switched off, a suitable measurement
bandwidth according to [5] is selected and the peak-to-peak value of the output jitter is
noted.
Measurement of maximum tolerable input jitter
The receiver part of the jitter measuring instrument (figure 3) is replaced by the receiver
part of the BER measuring instrument (figure 1). The clock waveform is modulated
sinusoidally, and the input jitter amplitude is increased until a specified threshold BER,
e.g. 10-3
, is reached. The jitter amplitude is noted. The measurement is then repeated at
several frequencies within the specified jitter frequency range.
Measurement of the jitter transfer function
The clock
...
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