EN 60835-2-6:1995
(Main)Methods of measurement for equipment used in digital microwave radio transmission systems - Part 2: Measurements on terrestrial radio-relay systems - Section 6: Protection switching
Methods of measurement for equipment used in digital microwave radio transmission systems - Part 2: Measurements on terrestrial radio-relay systems - Section 6: Protection switching
This measurement methods for an N+1 switching configuration are also applicable to N+2 switching arrangements, to 1+1, twin-path and hot standby arrangements.
Meßverfahren für Geräte in digitalen Mikrowellen-Funkübertragungssystemen - Teil 2: Messungen an terrestrischen Richtfunksystemen - Hauptabschnitt 6: Schutzschaltungen
Méthodes de mesure applicables au matériel utilisé pour les systèmes de transmission numérique en hyperfréquence - Partie 2: Mesures applicables aux faisceaux hertziens terrestres - Section 6: Commutation de protection
Ces méthodes de mesure correspondent à une configuration de commutation de type N+1 mais sont aussi applicables aux configurations de commutation de type N+2, de type 1+1, à transmission doublée et à élément de réserve sous tension.
Methods of measurement for equipment used in digital microwave radio transmission systems - Part 2: Measurements on terrestrial radio-relay systems - Section 6: Protection switching (IEC 60835-2-6:1995)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-oktober-2002
Methods of measurement for equipment used in digital microwave radio
transmission systems - Part 2: Measurements on terrestrial radio-relay systems -
Section 6: Protection switching (IEC 60835-2-6:1995)
Methods of measurement for equipment used in digital microwave radio transmission
systems -- Part 2: Measurements on terrestrial radio-relay systems -- Section 6:
Protection switching
Meßverfahren für Geräte in digitalen Mikrowellen-Funkübertragungssystemen -- Teil 2:
Messungen an terrestrischen Richtfunksystemen -- Hauptabschnitt 6: Schutzschaltungen
Méthodes de mesure applicables au matériel utilisé pour les systèmes de transmission
numérique en hyperfréquence -- Partie 2: Mesures applicables aux faisceaux hertziens
terrestres -- Section 6: Commutation de protection
Ta slovenski standard je istoveten z: EN 60835-2-6:1995
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
60835-2-6
INTERNATIONAL
Première édition
STAN DARD
First edition
1995-03
Méthodes de mesure applicables au matériel
utilisé pour les systèmes de transmission
numérique en hyperfréquence
Partie 2:
Mesures applicables aux faisceaux hertziens
terrestres
Section 6: Commutation de protection
Methods of measurement for equipment used in
digital microwave radio transmission systems
Part 2:
Measurements on terrestrial radio-relay systems
Section 6: Protection switching
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835-2-6 © IEC:1995
-
CONTENTS
Page
FOREWORD 5
INTRODUCTION
Clause
1 General 11
1.1 Scope 11
1.2 Normative references 11
2 Switching 11
2.1 Switching configurations 11
2.2 Pre-setting facilities 13
3 Non slipless protection switching 15
3.1 Switch operation - manual mode 15
3.2 Switch operation - automatic mode 15
4 Slipless protection switching 19
4.1 General considerations 19
4.2 Switch operation - manual mode 19
4.3 Switch operation - automatic mode 21
5 Channel priority status 23
5.1 Method of measurement 25
5.2 Presentation of results 25
5.3 Details to be specified 25
Figures 27
835-2-6 © IEC:1995 - 5 -
INTERNATIONAL ELECTROTECHNICAL COMMISSION
METHODS OF MEASUREMENT FOR EQUIPMENT USED
IN DIGITAL MICROWAVE RADIO TRANSMISSION SYSTEMS —
Part 2: Measurements on terrestrial radio-relay systems —
Section 6: Protection switching
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 cooperation 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, 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.
3) They have the form of recommendations for international use published in the form of standards, 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.
International Standard IEC 835-2-6 has been prepared by sub-committee 12E: Radio-relay
and fixed satellite communication systems, of IEC technical committee 12: Radio-
communications.
The text of this standard is based on the following documents:
DIS
Report on voting
12E(CO)168 12E/251/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.
IEC 835 consists of the following parts, under the general title: Methods of measurement
for equipment used in digital microwave radio transmission systems and satellite earth
stations.
- Part 1: 1990, Measurements common to terrestrial radio-relay systems and satellite
earth stations.
-
Part 2: 1990, Measurements on terrestrial radio-relay systems.
- Part 3: 1990, Measurements on satellite earth stations.
835-2-6 © IEC:1995 - 7 -
INTRODUCTION
The CCIR Recommendation 753* provides a general background to protection methods and
characteristics. In particular, section 3 of the annex 1 of this recommendation outlines the
methods of protection and gives an overview of the types of protection arrangements. The
principal factors influencing the choice of switching criteria are also stated.
Classes of protection switching equipment
The main classes of automatic protection switching equipment are associated with digital
radio-relay systems. In the first type, a no-break, slipless change-over is effected in con-
ditions where the main channel performance degrades sufficiently slowly to allow a
standby channel of equal transmission delay to be made ready and duly substituted. In the
second type, switching to the standby path takes no account of transmission delay differ-
ence and consequently, the change-over generally results in a short break of transmis-
sion, accompanied by a delay difference in the transmission path. When this delay
difference exceeds a ce rtain threshold, this may result in a slip (i.e. the addition or loss of
one or more bits) in the downstream equipment. A switching operation may be termed hit-
less if the change-over is slipless, and is such that no errors are introduced when both the
operating and standby channel have no errors, and the switching is effected without over-
riding the switching logic.
A typical automatic slipless protection system in which a number of channels are protected
for example by a single protection channel (N+1 system) is described in the following sub-
clause. Protection systems using two protection channels (N+2 systems) operate in a
similar manner.
For a given direction of transmission between two adjacent terminal equipments in a
digital radio-relay system, one of a group of channels is dedicated to serve as a standby
channel. Each channel to be protected may be assigned a priority rating in respect of its
ability to command the use of the standby channel. Channels with equal priority status are
protected on a "first come, first served" basis. When not used for protection, the standby
channel may carry occasional traffic; in this case, the occasional traffic has no priority,
and will be removed as soon as any operating channel needs the standby channel. The
principal criteria for initiating a switchover between any one of the main channels and the
standby channel are as follows:
a) loss of signal, i.e. data missing or loss of synchronization;
b)
degradation of the operating channel, resulting in a BER in excess of a pre-
determined value (within a range of 10
-3 to 10-6 , for example);
c)
restoration of a previously failed main channel, i.e. an improvement of the BER to
better than a predetermined value (typically one-to-two orders of magnitude better than
in item b).
* CCIR Recommendation 753:
Preferred methods and characteristics for the supervision and protection of
digital radio-relay systems.
(Geneva, 1992)
835-2-6 © IEC:1995 - 9 -
When protection is required at the receive terminal and when the protection channel is in
normal condition and not occupied, the transmit terminal is instructed, via an associated
control signal, to apply the traffic of the appropriate channel to the standby channel input.
Traffic continues to be applied in parallel to the original channel so that both channels are
carrying nominally identical traffic.
At the receive terminal, the signal of the standby channel (and in some implementations,
the operating channel also) passes via a variable delay element. As the digital signal is
present both at the output of the main channel and the standby channel, they are
compared bit by bit, and the delay difference is systematically removed until an acceptable
correlation is measured between the two inputs to the comparator. When this is achieved,
the standby channel is switch-selected at the receive terminal in place of the main
channel. The change-over is thus arranged to give only an acceptable number of errors.
The change-over is also called slipless if bit coincidence is achieved immediately prior to
switching.
If loss of signal in a main channel occurs, no comparison can take place. In such cases,
the receive terminal will automatically force a change-over after a given delay has
occurred. Confirmation of successful change-over is exchanged via the supervisory control
signal.
Once the performance of the main channel is deemed to be satisfactory, receive-end
slipless switch-back from the standby channel to the appropriate main channel follows. In
the case of N+1 or N+2 protection systems, confirmation of successful change-over is then
passed, via the supervisory control signal, to the transmit terminal where switching is also
restored to free the standby channel, and thus make it available for the protection of other
channels.
In some protection switching systems, two BER switching criteria are applied in the range
of 10
-6 to 10-3. In this case, if the standby channel is occupied by the channel in which
only the lower BER is exceeded, and another main channel with a BER exceeding the
higher criterion or in the "loss-of-signal" condition needs protection, the former channel is
switched back to its original position and the standby channel will be occupied by the latter
channel.
In comparison with the above slipless protection switching system, non-slipless protection
switching systems are simpler in concept. Upon request from the receive terminal to imple-
ment a change-over, the transmit terminal switches the traffic to the standby channel (i.e.
parallel transmission over main and standby channels takes place). The receive terminal
then switches to the standby channel once satisfactory transmission is confirmed. No
attempt is made to remove the transmission delay difference between the main and
standby channel. This may result in a brief interruption or even a slip in the operating
path.
In addition to automatic protection switching facilities, most equipment offers the facility
for switching under manual control. This control may be carried out directly at the
terminals, and in some cases also by means of an associated supervisory and control
channel.
835-2-6 © IEC:1995 - 11 -
METHODS OF MEASUREMENT FOR EQUIPMENT USED
IN DIGITAL MICROWAVE RADIO TRANSMISSION SYSTEMS –
Part 2: Measurements on terrestrial radio-relay systems –
Section 6: Protection switching
1 General
1.1 Scope
This section of IEC 835-2 deals with the measurement of terminal-to-terminal protection
switching equipment associated with digital radio-relay systems.
The measurement methods described in this section of IEC 835-2 for an N+1 switching
configuration but are also applicable to N+2 switching arrangements. The same
measurement methods are applicable to 1+1, twin-path and hot standby arrangements.
The channel priority status tests described in clause 5 are only applicable to the N+1 and
N+2 switching arrangements. In configurations where the protection switching equipment
is physically separable from the radio terminal equipment (see figure 1), the inte
rfaces at
the input and output po rts of the switching equipment shall be measured in accordance
with IEC 835-2-5.
1.2
Normative references
The following normative documents contain provisions which, through reference in this
text, constitute provisions of this section of IEC 835-2. At the time of publication, the edi-
tions indicated were valid. All normative documents are subject to revision, and pa
rties to
agreements based on this section of IEC 835-2 are encouraged to investigate the
possibility of applying the most recent editions of the normative documents indicated
below. Members of IEC and ISO maintain registers of currently valid International
Standards.
IEC 835-1-3: 1992,
Methods of measurement for equipment used in digital microwave
radio transmission systems - Part
1: Measurements common to terrestrial radio-relay sys-
tems and satellite earth stations - Section 3: Transmission characteristics
IEC 835-2-5: 1993, Methods of measurement for equi
...
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