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Integrated Maintenance of Transmission Systems in AXE 10 Networks Mats Eneborg, Jan Insulander and Walter Widl The maintenance of digital telephone networks, built up of AXE 10 exchanges and the digital transmission systems between them, can be rationalized by combining the maintenance functions of the exchanges with other computercontrolled maintenance systems. The rationalization can include several routines in the field of operation and maintenance. This article, however, only discusses functions concerned with fault-location in digital transmission systems. The fault location can be carried out from centralized work stations or locally, near the equipment. The flexibility of the maintenance systems makes it easy to adapt them to different network structures and maintenance organizations. A paper with mainly the same content will be presented at ICC'84 in Amsterdam, in May 1984. UDC 621 395.74 004 54 From the point of view of maintenance digital transmission systems are divided into a number of maintenance entities, ME 1 . Each maintenance entity has an input, an output and one or several functional units in between. The function is tested by means of internal measurements, the results of which can be read off, either continuously or on request. A basic principle is that if a fault occurs in the system it must be possible to trace the fault to the correct maintenance entity or part of an entity. How well a fault can be pinpointed depends on the efficiency of the internal maintenance functions of the particular entity. The basic methods for the maintenance of digital transmission systems recommended by CCITT are performance monitoring and alarm based maintenance 2 . Performance monitoring uses direct measurements, such as the bit error rate, which are a measure of the transmission quality. Alarm based maintenance, on the other hand, is based on the principle that an alarm is initiated automatically as soon as the quality levels fall below preset values. Which method is to be preferred depends on such factors as the structure of the network, type of equipment and the maintenance philosophy used within the maintenance organization. In AXE 10 networks alarm-based maintenance is used for the digital system terminals, and performance monitoring for the maintenance of digital repeaters and cable sections. Alarms and monitoring results can be presented at the maintenance entity, locally in exchanges or, with the aid of computer-controlled maintenance systems, in specially arranged transmission maintenance centres. AXE 10 networks Fig. 1 shows a hypothetical section of an AXE 10 network with digital network components for switching and transmission. The AXE 10 components consist of - local exchanges, LE, transit exchanges, TE, and combined local/ transit exchanges, LE/TE - remote digital subscriber stages, RSS, for between 64 and 2048 subscribers - remote subscriber multiplexers, RSM, for the connection of 30 subscribers. The connecting line systems, the multiplexers and the transmultiplexers can belong to the 1544 or 2048kbit/s hierarchy. Within an area with only one AXE 10 exchange, for example in a rural or local network, faults in the connected digital transmission systems can be located from the work station in the exchange. The maintenance is centralized and thetransmission maintenance system ZAN 201 ensures efficient fault location, fig. 2. Fig.1 Components in an AXE 10 network TE Transit exchange LE Local exchange RSS Remote digital subscriber stage RSM Remote subscriber multiplexer — Digital line systems
MATS ENEBORG Fibre Optics and Line Transmission JAN INSULANDER WALTER WIDL Public Telecommunications Division Telefonaktiebolaget LM Ericsson Fig. 2, left An example of a rural or local network (a network with a single AXE 10 exchange) Fig. 3, centre An example of a trunk or junction network (a network with several AXE 10 exchanges) Fig. 4, right An example of an urban or metropolitan network (a network with several AXE 10 exchanges) In an area with several AXE 10 exchanges, for example a junction or trunk network, fig.3, or an urban or metropolitan network, fig.4 fault location can be carried out from a centralized workstation, with the aid of the operation and maintenance system AOM101 and thetransmission maintenance system ZAN101. The degree of integration is open to choice. Separate work stations can be arranged for fault location in digital transmission equipment, or alternatively all maintenance activities can be fully integrated. Digital line systems are terminated in exchange terminals, ET, in exchanges and RSS, and in PCM multiplexers and signal conversion equipment in RSM. Exchange terminals are included in the exchanges, but from the point of view of maintenance they form part of the connected digital transmission systems. Thus a digital transmission path usually consists of both internal and external maintenance entities, i.e. entities placed in an exchange and remote from exchanges respectively. In the case of a fault each maintenance entity initiates the alarms and has the functions defined in CCITT recommendations series G and Q. Maintenance of transmission equipment A fault that occurs in a transmission system can be located by analysing the alarms from the internal and external transmission equipment. In certain cases, for example when a fault occurs in a line system containing regenerators, the alarm information must be supplemented by measurements of the line bit error rate (BER). The alarms and measurement results are collected, processed, interpreted and then transmitted to and presented at a work station for fault location. This process can include - AXE 10 exchanges - the operation and maintenance system AOM101 - the transmission maintenance systems ZAN 101 and ZAN 201 The choice of a maintenance system or combination of systems is dependent on such factors as the type and size of the network and the desired degree of automation. Moreover the suitability of different systems is dependent on the actual siting of the transmission equipment. Different placing of transmission equipment leadstoslighty different alarm routines, for example: - internal AXE 10 equipment, in which the alarms detected in exchange ter-
Page 1: ERICSSON REVIEW Integrated Maintena
Page 5 and 6: ERICSSON REVIEW Number 1 1983 Volum
Page 7 and 8: The unique facility of a satellite
Page 9 and 10: Technical data for a station Antenn
Page 11 and 12: Technical data for the feeder link
Page 13: 9 Fig. 7 Mixer and preamplifier The
Page 17 and 18: 13 Fig. 6 The structure of system Z
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Page 21 and 22: Fig. 11 Part of an urban and trunk
Page 23 and 24: 19 MATS ENEBORG BJORN JOHANSEN Depa
Page 25 and 26: Fig. 6 An example of a printout of
Page 27 and 28: Technical data for ZAN 101 Maximum
Page 29 and 30: Fig. 14 The Transmission maintenanc
Page 31 and 32: 27 BJORN LENGQUIST PER AKE WIBERG E
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Page 35 and 36: 31 ules can be used to successively
Page 37 and 38: BENGTJANSSON KENT JOHANSSON TOMMY O
Page 39 and 40: 35 The control individuals are divi
Page 41 and 42: 37 Fig. 10 LPB 110 used in an AXE 1
Page 43 and 44: 39 BENGT LAGERSTEDT Public Telecomm
Page 45 and 46: 41 Fig. 6 With multiplexer ZAH 1.5/
Page 47 and 48: Fig. 10 In this example of the use
Page 49 and 50: 45 HARALD BRANDT ALEKSANDER MARLEVI
Page 51 and 52: 47 Fig. 5 Stored program controlled
Page 53 and 54: 49 quency jumps and no transmission
Page 55 and 56: Hotel Communication System Robert D
Page 57 and 58: 53 Fig. 3 The answer telephones at
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Page 61 and 62: 57 Fig. 7 The hotel computer, Erics
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ERICSSON ISSN 0014-0171 Telefonakti
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