1、BRITISH STANDARD BS EN 60835-2-6:1996 BS7573-2.6: 1996 IEC835-2-6: 1995 Methods of measurement for equipment used in digital microwave radiotransmission systems Part 2: Measurements on terrestrial radio-relay systems Section 2.6 Protection switching The European Standard EN60835-2-6:1995 has the sta
2、tus of a BritishStandard ICS 33.060.30BSEN60835-2-6:1996 This BritishStandard, having been prepared under the directionof the ElectrotechnicalSector Board,was published undertheauthority of the StandardsBoard and comesintoeffect on 15 February1996 BSI01-2000 The following BSI references relate to th
3、e work on this standard: Committee reference EPL/12 Draft for comment95/210407DC ISBN 0 580 25166 7 Committees responsible for this BritishStandard The preparation of this BritishStandard was entrusted to Technical Committee EPL/12, Radio communication, upon which the following bodies were represent
4、ed: British Broadcasting Corporation British Radio and Electronic Equipment Manufacturers Association British Telecommunications plc ERA Technology Ltd. Institution of Electrical Engineers Radio, Electrical and Television Retailers Association Radiocommunications Agency Amendments issued since publi
5、cation Amd. No. Date CommentsBSEN60835-2-6:1996 BSI 01-2000 i Contents Page Committees responsible Inside front cover National foreword ii Foreword 2 Text of EN60835-2-6 3 List of references Inside back coverBSEN60835-2-6:1996 ii BSI 01-2000 National foreword This BritishStandard has been prepared b
6、y Technical Committee EPL/12 and is the English language version of EN60835-2-6:1995 Methods of measurement forequipment used in digital microwave radio transmission systems Part2: Measurements on terrestrial radio-relay systems Section6: Protection switching, published by the European Committee for
7、 Electrotechnical Standardization (CENELEC). It is identical with IEC835-2-6:1995, published by the International Electrotechnical Commission (IEC) and is part of a series. BS EN60835 is published in three Parts. The other Parts are: Part 1: Measurements common to terrestrial radio-relay systems and
8、 satellite earth stations; Part 3: Measurements on satellite earth stations. This Section of BS EN60835-2 covers measurement of terminal-to-terminal protection switching equipment associated with digital radio-relay systems. The methods described are for an N+1 switching configuration but are also a
9、pplicable to N+2 switching arrangements and to1+1, twin-path and hot standby arrangements. The channel priority status tests described in clause5 are applicable only to the N+1 and N+2 switching arrangements. In configurations where the protection switching equipment is physically separable from the
10、 radio terminal equipment (see Figure 1,) the interfaces at the input and output ports of the switching equipment shall be measured in accordance with BS EN60835-2-5. It is expected that other Sections of IEC Publication835 will be published as identical BritishStandards, subject to their harmonizat
11、ion by CENELEC. Some Sections of this BritishStandard have already been published as Sections of BS7573. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Stan
12、dard does not of itself confer immunity from legal obligations. Cross-references International Standard Corresponding BritishStandard BS EN60835 Methods of measurement for equipment used in digital microwave radio transmission systems Part 1: Measurements common to terrestrial radio-relay systems an
13、d satellite earth stations EN60835-1-3:1995 (IEC835-1-3:1992) Section 1.3:1995 Transmission characteristics a EN60835-2-5:1995 (IEC835-2-5:1993) Part 2: Measurements on terrestrial radio-relay systems Section 2.5:1995 Digital signal processing sub-system a In preparation. Summary of pages This docum
14、ent comprises a front cover, an inside front cover, pagesi andii, theEN title page, pages2 to16, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cove
15、r.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN60835-2-6 April1995 ICS 33.060.30 Descriptors: Radiocommunications,telecommunications, communication equipment, digital technics, radio-relay systems, microwave frequencies, measurements, switching, protection English version Methods of measureme
16、nt for equipment used in digital microwave radio transmission systems Part2: Measurements on terrestrial radio-relay systems Section6: Protection switching (IEC835-2-6:1995) Mthodes de mesure applicables au matriel utilis pour les systmes de transmission numrique en hyperfrquence Partie2: Mesures ap
17、plicables aux faisceaux hertziens terrestres Section6: Commutation de protection (CEI835-2-6:1995) Meverfahren fr Gerte in digitalen Mikrowellen-Funkbertragungssystemen Teil2: Messungen an terrestrischen Richtfunksystemen Hauptabschnitt6: Schutzschaltungen (IEC835-2-6:1995) This European Standard wa
18、s approved by CENELEC on1995-03-06. 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
19、 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 la
20、nguage and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden,
21、 Switzerland and UnitedKingdom. CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B-1050 Brussels 1995 Copyright reserved to CENELEC members Ref. No
22、. EN60835-2-6:1995 EEN60835-2-6:1995 BSI 01-2000 2 Foreword The text of document12E(CO)168, future edition1 of IEC835-2-6, prepared by SC12E, Radio relay and fixed satellite communication systems, of IEC TC12, Radiocommunications, was submitted to the IEC-CENELEC parallel vote and was approved by CE
23、NELEC as EN60835-2-6 on1995-03-06. The following dates were fixed: Annexes designated “normative” are part of the body of the standard. In this standard, Annex ZA is normative. Annex ZA has been added by CENELEC. Contents Page Foreword 2 Introduction 3 1 General 4 1.1 Scope 4 1.2 Normative reference
24、s 4 2 Switching 4 2.1 Switching configurations 4 2.2 Pre-setting facilities 5 3 Non slipless protection switching 5 3.1 Switch operation manual mode 5 3.2 Switch operation automatic mode 5 4 Slipless protection switching 6 4.1 General considerations 6 4.2 Switch operation manual mode 7 4.3 Switch op
25、eration automatic mode 7 5 Channel priority status 8 5.1 Method of measurement 8 5.2 Presentation of results 8 5.3 Details to be specified 8 Annex ZA (normative) Normative references to international publication with their corresponding European publication 15 Figure 1 Typical N+1 protection switchi
26、ng arrangement 9 Figure 2 Typical twin-path protection switching arrangement 9 Figure 3 Arrangement for testing manual operation of non-slipless switch 10 Figure 4a Arrangement for testing automaticoperation of non-slipless switch 10 Figure 4b Typical oscilloscope or logic analyserdisplay obtained w
27、ith the arrangementshown in Figure 4a 11 Figure 5 Arrangement for testing manualoperation of slipless switch 12 Figure 6 Arrangement for testing detectiontimeinterval of slipless switch 13 Figure 7 Arrangement for testing automaticoperation of slipless switch 14 latest date by which the EN has to be
28、 implemented at national level by publication of an identical national standard or by endorsement (dop)1996-03-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow)1996-03-01EN60835-2-6:1995 BSI 01-2000 3 Introduction The CCIR Recommendation753 1)provides
29、a general background to protection methods and characteristics. In particular, section3 of the annex1 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 s
30、tated. 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 conditions where the main channel performance degrades sufficiently slowly
31、 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 difference and consequently, the change-over generally results in a short break of transmission, accompanied by a de
32、lay difference in the transmission path. When this delay difference exceeds a certain 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 erro
33、rs 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 d
34、escribed 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 stan
35、dby 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 occasi
36、onal 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.d
37、ata 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 of10 3to10 6 , for example); c) restoration of a previously failed main channel, i.e.an improvement of the BER to better than a predetermined value
38、(typically one-to-two orders of magnitude better than in itemb). 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
39、 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
40、 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 i
41、s 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 sig
42、nal 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
43、 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 switc
44、hing is also restored to free the standby channel, and thus make it available for the protection of other channels. 1) CCIR Recommendation753: Preferred methods and characteristics for the supervision and protection of digital radio-relay systems. (Geneva,1992)EN60835-2-6:1995 4 BSI 01-2000 In some
45、protection switching systems, two BER switching criteria are applied in the range of10 6to10 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” cond
46、ition 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
47、the receive terminal to implement 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
48、 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. Th
49、is control may be carried out directly at the terminals, and in some cases also by means of an associated supervisory and control channel. 1 General 1.1 Scope This section of IEC835-2 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 IEC835-2 for an N+1 switching configuration but are also applicable to N+2 switching arrangements. The same measurement methods are applicable to1+1, twin-path a
