Dichroic Antenna Reflector for Space Applications CCITT ...

ERICSSON REVIEWNumber 2 1991 Volume 68Responsible publisher GostaLindbergEditor GoranNorrmanEditorial staff MarttiViitaniemiSubscription Peter MayrSubscription one year $30Address S-12625 Stockholm, SwedenPublished in Swedish, English, French and Spanish with four issues per yearCopyright Telefonaktiebolaget L M EricssonContents22 • Dichroic Antenna Reflector tor Space Applications34 • CCITT Standardisation of Telecommunications Management Networks52 • Power Supply System BZA 106 for Small Telecommunications Plant57 • ZAN 202, a System for Operation and Maintenance of TransmissionEquipmentCoverThere is a growing need for small, reliable powersupply systems. Ericsson has developed threenew systems that meet the more stringent demandsfor high reliability, small volume and lowradio interference now being made by the market.The systems are described in the article onpage 52

Dichroic Antenna Reflector Tor spaceApplicationsAnders Derneryd and Hans WilhelmssonIn three decades Ericsson Radar Electronics AB has built up considerable expertise inthe field of radar and communications antennas. The manufacturing range alsoincludes sophisticated antenna systems for commercial and scientific satellites. Theexpert knowledge is the result of close collaboration between radar and space antennadevelopment sections and contact with national and international research centres.The authors describe the design, manufacture and testing of a dichroic subreflectorbuilt UD of freauencv-selective surfaces in a sandwich construction.reflector antennassatellite antennascomposite materialsFuture communications satellites will containtransponders for telephony, television,data etc. and will therefore communicateon several different frequency bands. Presenttechnology would require several antennasystems. The antennas, which usuallyconsist of large, folding reflectorsystems, take up a large part of the overallcost and of the weight and volume of thetotal system. All these parameters can bereduced through the use of a single antennasystem for several frequency bands.Frequency-selective subreflectors, functioningas diplexers, make this possible.Frequency-selective surfaces are built upof periodic metallic patterns. They behaveas reflecting mirrors in one frequency bandand as transparent windows in another. Asubreflector built up of frequency-selectivesurfaces was first used in space technologyfor data transmission from the Voyagerspace probes to earth. The two frequencybands used were widely separated. In thecommunications field the required frequencyratios are normally relatively small; in theorder of 1.6:1.This new field of antenna technology hasbeen studied on behalf of the EuropeanSpace Agency, ESA, in a joint project carriedout by Stefan Johansson and Nic Shuleyat the Chalmers University of Technologyin Gothenburg and Lars Petterssonat the National Defence Research Institute(FOA) in Linkoping.A frequency-selective subreflector, Fig. 1,with a diameter of 1.1 m has been designed,manufactured and successfullytested for space applications in the communicationsfield.The prime requirement is in terms of performance:it must be on a par with that of asingle-reflector system or a dual-reflectorsystem with a metallic subreflector. Also,the weight must be minimised and the environmentalrequirements of an Arianespacecraft launch must be met. Finally, thesubreflector must be mechanically stable inthe geostationary orbit in space.Fig. 1The frequency-selective subreflector

ANDERS DERNERYDHANS WILHELMSSONEricsson Radar ElectronicsOne antenna serves as twoThe metallic subreflector in a dual-reflectorsystem is replaced by a frequency-selectivesurface, consisting of a metallic patternon a carrier made of dielectric material. Thefrequency-selective subreflector gives accessto both the primary and the secondaryfocus, Fig. 2. Near the resonance frequencyof the periodic metal pattern the surfaceis reflecting as if it were made of homogeneousmetal. Signals from the feed horns inthe secondary focus are reflected.At the same time the surface is almost completelytransparent to the lower frequenciesfrom the feed horns in the primary focus.This means that the antenna system canbe used for two different frequency bandssimultaneously. Fig. 3 shows the frequencycharacteristics of the manufactured frequency-selectivesubreflector. Its performancehas been optimised primarily for thefrequencies 18.1-20.2 GHz and 10.7-11.7GHz, and secondarily for 17.7-18.1 GHzand 12.5-12.85 GHz. Also, two linear polarisationmodes can be used simultaneously,thereby increasing transmission capacityfurther.Box 1TERMS AND DEFINITIONSCTECoefficient of thermal expansionDiplexerDevice that permits parallelfeeding of one antenna fromtwo transmitters at the sameor different frequencies withoutthe transmitters interferingwith each otherGrating lobes Secondary main lobesCross polarisation Polarisation perpendicular toa reference polarisationmodePlyOne layer in a compositeLaminateThe whole structure in themould, consisting of severalpliesMatrixThe encompassing materialin the composite (i.e. the plastic)Offset geometry Shadow-free geometry. Thefeeder in the primary focus ismounted so that the effect ofits shadow on the secondaryradiation is negligibleRadomeProtective antenna cover thathas little effect on the radiationpattern of the antennaSkinSurface layer in a sandwichstructureFig. 2Reflector system with a frequency-selectivesubreflector

24Fig. 3Frequency characteristic of the subreflectorDesignRequirementsThe subreflector must be strong and stiff inorder to survive vibration and noise duringthe launch. The requirements are specifiedin detail in the Ariane IV manual. The vibrationlevels are so high that only very strong,stiff and light construction materials arefeasible.During the launch the subreflector must befolded towards the satellite, partly to beaccommodated in the nose cone and partlyto be properly secured. In space, the subreflectoris unfolded (through the release ofa spring-loaded mechanism) and mustthen end up in the correct position. At themoment of unfolding, the subreflector issubjected to a heavy shock load.The subreflector must also retain its accurategeometry when exposed to the environmentalstresses in space. The moststringent requirement concerns the longtermtemperature cycling. In the geostationaryorbit, the temperature at the subreflectorvaries between +160 C during theday and -180 C during the 72-minutenight. This makes great demands on thematerials. However, the temperature variationsat the subreflector can be reduced ifsun screens and insulating materials areused.The cosmic radiation in space affects thesurface materials. Particular attention mustbe paid to electrostatic charge caused byelectron bombardment, which results indischarges that may damage the electronicsin the satellite.Another requirement for space equipmentis minimum outgassing of the materials; or,to be precise, no more than one per cent oftheir weight. Volatile constituents may condenseon the solar panels of the satelliteand reduce their efficiency.The subreflector must have the correct geometricform in order to function. Manufacturingdistortion, inaccuracies in themould shape, material creep, bulking, andthermal distortion in space are factors thatinfluence the shape of the reflector. In orderfor the subreflector to meet the electricalrequirements, any deviation with respect toform, calculated as the root-mean-squarevalue, must be less than 0.1 mm.The weight of the subreflector must be low.ESA's requirement-less than 3 kg/m 2 - israther on the tough side, however.The necessary electrical characteristics ofthe antenna mean exacting requirementsfor materials and construction. A frequency-selectivesubreflector must be transparentin one frequency band, where lossesmust be reasonable low. Even in the reflectedfrequency band, signals will penetratethe construction and be affected bythe material.The manufacture of the antenna necessitatesthe use of composite materials andmetallisation methods. It is particularly difficultto produce metallised patterns on asurface with a double curvature.In conclusion it may be stated that the demandson the design are many and partlyincompatible. Most of them trace back torequirements for materials. It is clear thatdesigns like this would be impossible withoutsophisticated materials and manufacturingmethods.ConstructionThe subreflector has frequency-dependentreflection and transmission characteristics,achieved through a regular pattern of thin,crossed dipoles. The size and periodicity ofthe dipoles are critical parameters for theelectric characteristics. A single layer of

25Fig. 4Different sandwich structures. The fibre directionsare shown in brackets for the differentlaminates. Alternative A is the structure chosenfor the subreflectorcrossed dipoles meets the reflection requirementsbut gives too large losses in thetransmission band. The solution is to includea second layer of crossed dipoles.The resonance frequency chosen for thesecond pattern is the same as that for thefirst layer. This gives a broad transmissionband. The distance between the dipole layersis approximately 5mm, correspondingto a quarter of a wavelength. Transmissionlosses are then minimised, since the subreflectorbehaves like a sandwich radome.The general frequency dependence of thefrequency-selective surface is calculatedon the basis of equivalent circuit models.Capacitance and inductance values areobtained with the aid of a theoretical modelfor a simplified, one-dimensional structure.However, the validity of this model is limitedto flat surfaces and normal incident rays. Itprovides preliminary dimensions, whichserve as initial values for more accurateoptimisation, using integral calculus for arbitrarypolarisation and angle of incidence.The length of the dipole arms mainly affectsthe resonance frequency of the surface.The bandwidth of the reflected band is dependenton the packing density of thecrossed dipoles and on the angle of incidenceof the rays. The frequency bandbecomes larger if the dipoles are close, butat the same time the separation betweenthe reflection and transmission bands isincreased. A sparse pattern, on the otherhand, reduces transmission losses butgenerates undesirable grating lobes.The dipole length is 5.25 mm in the upperlayer and 5.10 mm in the lower. The resonancefrequency will then be the same forthe two layers, since the difference inlength is compensated by the surroundingdielectric skins. The centre distance betweenthe dipoles is 5.6 mm in both layers.In order to reduce frequency sensitivity atlarge angles of incidence the dipoles areturned 17° in relation to the axes of theperiodic pattern. Reflection and transmissionlosses, exclusive of dielectric losses,are estimated to be less than 0.2 dB forangles of incidence less than 42° to thenormal.The mechanical design makes for severalbasic properties of the subreflector, suchas:-electrical function- environmental endurance- low weight, thermal stability- processability.Sandwich constructions using compositesare common in space reflectors. Sufficientstiffness can be obtained with a sandwichof approximately 25 mm if the stiffest fibrematerials are used. The very strong andstiff Kevlar fibre was chosen. Each ply is0.125 mm thick and contains 60% fibres.Several different sandwich structures werestudied, Fig. 4.In alternative A four plies are used in eachlaminate. The lay-up of each ply is symmetrical(0790°/9070°). The disadvantagesof this structure is that the sandwichbecomes unsymmetrical and that the normalplane of the mechanical stresses deviatesfrom the geometrical mean plane,since there are more plies at one side of thesandwich. The material is not used optimally;the fibres at the front take less load thanthose at the back.Alternative B does not have these disadvantages,since the two skins at the front ofthe subreflector together have the samethickness as the rear skin. However, threelayerskins cannot be made symmetricaland they will therefore be skew after manufacture.In view of this complication and thesubsequent metallisation, alternative Bwas dropped.Alternative C offers an attractive solutionwhere the electrically active surfaces areplaced symmetrically and protected in thecentre of the sandwich. However, it requiresfour skins and more adhesive layersin order to keep the structure together. Thisalternative therefore gives higher dielectricmaterial losses.

Table 1STRUCTURE OF THE SUBREFLECTORLayer Material ThicknessFig. 5Structure of the frequency-selective subreflector

Fig. 6The lowest self-resonance of a subreflectorexposed to sinusoidal vibrationThe structure of alternative A was chosenbecause of the low reflection losses, inspite of the somewhat greater weight. Thegeneral structure is shown in Fig. 5.Honeycomb made of Nomex was chosenas distance material. The height of the distanceswas adjusted to minimise reflectionand transmission losses.The thinnest adhesive film in the marketwas used for bonding. The carriers andmetallisation protection layers consist ofadditional layers of adhesive and thin fibrerug. Table 1 lists all materials used.During a launch the subreflector is held inplace by three metal inserts. They are approximately50 mm and bonded betweentwo of the skins at the edge of the subreflector.A general type of unfolding devicefor the subreflector was designed.The subreflector design was subjected toextensive thermal and mechanical analyses.The weight of the subreflector wasestimated to be 4.5 kg and its lowest selfresonancefrequency 73 Hz. The highestand lowest temperature was calculated tobe +62°C and -77°C respectively. Themaximum geometric error in the thermalFig. 7Temperature distribution when half the subreflectoris in shadow

Fig. 8Framework of the steel mouldFig. 9The finished steel mouldenvironment was calculated to be 0.3 mmroot-mean-squared. Figs. 6 and 7 show theresults of some of the calculations. Aftermanufacture, the characteristics of thesubreflector were verified in environmentaltests.Processes and methodsThe subreflector was made in a large,stainless steel moulding tool. The mouldconsists of a framework and a welded shell,Fig. 8. The shell was preformed plasticallyout of 20 mm sheet steel; a process thatshaped it to a tolerance of 2 mm. The weldedmould blank was then milled and polishedto the correct shape, Fig. 9.The surface accuracy of the mould, calculatedas the root-mean-square error, is0.06 mm. It is very important that the tolerancesare met in the preforming process,since the thickness of the shell will otherwisebe uneven, resulting in uneven heatingwhen the blank is cured. Thermal expansionhas to be considered whenprocessing the mould, so that the correctshape will be obtained at the curing temperature.The metal pattern on the double-curve surfaceis applied by means of a special method.It is based on co-curing, Box 3, andexploits the fact that the curvature is small.Patterns are etched flat. The detailed patternis drawn on a film by a computer-controlledphoto plotter. Each cross in the patternis drawn with a 0.1 mm pen to ensuresharp corners. The contour of a cross isdrawn first and filled in afterwards. Thesubreflector consists of approximately30 000 crosses and the photo plotter needs48 hours to draw the pattern.Composite materials and the pattern carrierare laid up on the mould and cured in anautoclave, Fig. 10. Pressure and temperaturein the autoclave (which is also used tobond the sandwich) are adjusted in accordancewith a program so that a pore-freecomposite with the correct fibre contentand good characteristics is obtained.Fig. 10Ericsson's autoclave workshop

29Fig. 12The frequency-selective subreflector installed inFOA s test hall, for recording of its radiationpatternFig.11A section of the finished frequency-selectivesubreflector1 Copper crosses2 Individual Kevlar fibre from fibre rug3 Plastic matrix in the pattern carrier4 Lamina with fibres across the cut5 Lamina with fibres along the cut6 Distance materialThe two patterned skins are made individuallyon the mould; the third skin is cureddirectly on the honeycomb.The manufacturing process is interspersedwith inspections to secure product quality.The finished subreflector has a form error,root-mean-squared, of 0.09 mm. Fig. 11shows a section of the finished frequencyselectivesubreflector.Radiation characteristicsThe radiation pattern for the frequency-selectivesubreflector was measured inFOA's large anechoic room. The subreflectorwas illuminated by circular, corrugatedfeed horns placed in both the primary andthe secondary focus. This type of horn generateslow cross-polarisation levels; in theorder of -35dB. The edge illumination onthe subreflector from the feed horns is-20dB in the transmission band and -7dBin the reflection band. Fig. 12 shows thesubreflector during the recording of the radiationpattern. The feed horn is placed inthe primary focus and the radiation is recordedas a function of the azimuth andelevation angles. The supporting structureis covered with absorbing material in orderto reduce interference.The performance of the subreflector isevaluated by comparing the actual radiationwith the ideal cases. The reflectioncharacteristics are determined by means ofa comparison with the radiation patterns fora metallic subreflector, and the transmissioncharacteristics are obtained throughcomparison with the radiation from the feedhorn without subreflector.Typical measured radiation patterns for thesubreflector are recorded as a function ofthe elevation angle with a vertically polar-

30Table 2Calculated radiation characteristics In the transmissionband, tor a complete antenna system. Vertical polarisationTable 3Calculated radiation characteristics in the reflectionband, for a complete antenna system. VerticalpolarisationFig. 13Recorded radiation patterns as a function of theelevation angle for frequency-selective (-) andmetallic (....) subreflectors. The measurementfrequency was 17.7 GHz; vertical polarisationised feed horn in the secondary focus,Fig. 13. The amplitude variation in the diagramis caused by interference betweenthe signals reflected from the surface of thesubreflector and those diffracted at itsedge. The cross polarisation level is -30 dBrelative to the main polarisation. The levelis determined primarily by the offset geometryof the reflector system and secondarilyby the frequency-selective dipole pattern.The difference in level between the tworecordings in the figure corresponds to aloss of 0.3 dB. The corresponding value forthe transmission mode has been measuredto 0.5 dB.The performance of the complete reflectorantennasystem with the main reflector inplace is assessed by means of theoreticalanalyses. Calculated reflection and transmissioncoefficients for a flat, infinite frequency-selectivesurface are integrated intoan analysis program for reflectorantennas. The subreflector is then considereda local plane. This approximation ispermissible, since the periodicity of the patternis considerably less than the smallestcurvature radius of the subreflector and thedistances to the feed horns.The results with vertical polarisation andwith the feed horns in the foci are summarisedin Tables 2 and 3. The complete reflectorsystem has been analysed at 11.2 GHzfor the transmission mode and at 19.1 GHzfor the reflection mode. The characteristicsof the frequency-selective subreflectorhave been calculated at three frequencieswithin each band. The introduction of thesubreflector has a marginal effect on systemperformance: the antenna gain is unchangedexcept for the attenuation in thesubreflector. As has been mentioned already,it is estimated - on the basis ofseparate measurements on the subreflector- to be 0.5 dB in the transmission bandand 0.3 in the reflection band.The maximum increase of side lobe levelswas from -24.4 to -23.8 dB in the transmis-

Fig. 14Calculated radiation patterns for a completeantenna system as a function of the azimuthangle for a frequency-selective subreflector (....)and without subreflector (-). The frequency is 11.2GHz; vertical polarisationsion band and from -22.6 to -21.2dB in thereflection band. This is equivalent to a disturbancelevel of -47dB and -38 dB respectively.The corresponding disturbancelevels for the cross-polarisation lobes are-36dB and -30dB respectively. Fig. 14shows an example of calculated radiationpatterns from the reflector system, includingthe main reflector, with a vertically polarisedfeed horn placed in the primary focus.SummaryThe main purpose of the described projectwas to develop frequency-selective surfacesand evaluate their use in space applications.Analysis methods and manufacturingprocesses have been verified by meansof measurements on a hyperbolic subreflectorwith a sandwich structure. The electricalperformance of a dual-reflector systemwith offset geometry is slightlyimpaired by the introduction of a frequencyselectivesubreflector.Frequency-selective surfaces offer the designernew possibilities in the antenna field.Radomes, polarisers, flat reflectors andfrequency-scanned reflector antennas aresome examples of applications where thisnew technology is being studied. Paralleldevelopment of materials and manufacturingprocesses is under way, and this progressis being exploited for other types ofantenna too; for example printed circuit antennas.Further developmentThe frequency-selective subreflector describedabove was developed and manufacturedin 1986. ESA has commissionedfurther development of the technology. Thepurpose of the continuation project is todevelop new manufacturing methods forapplying patterns to surfaces with pronounceddouble curvature and to reducethe number of adhesive and dielectric layers.The aim is to refine the technology soas to be able to meet new demands forproducts.

32Fig. A for Box 2Specific strength and specific stiffness of somecommon construction materialsCFRP Carbon-fibre-reintorced plasticGFRP Glass-fibre-reintorced plasticBox 2COMPOSITE MATERIALSComposite materials consist of two or more components.They make it possible to combine the bestproperties of different materials; for example, thecompression strength and low price of concretewith the tensile strength of reinforcing rods. Compositematerials include- reinforced concrete- fibre-reinforced plastic-fibre-reinforced metals-wood- plywood, chipboard- ceramics.The composites mainly considered for antennasare fibre-reinforced plastics. They combine the lowweight and protective properties of plastics with thestiffness and strength of fibre.Fig. A shows the specific strength and stiffness ofsome common construction materials. Composites,particularly carbon-fibre-reinforced plastic,have extreme properties in the direction along thefibre. The difference between composites and metalsis accentuated when the properties are givenrelative to the weight.The material properties vary considerably with thefibre direction, Fig.B. In order to achieve a laminatethat is isotropic in the plane, it is necessary to lay upfibres along at least three different axes: e.g. (0°/60°/-60°) or (0 0 /90°/45 0 /-45°). The dependenceon direction makes it possible to control the propertiesof the material so that they are matched to theload on the finished product. The dependence alsoentails risks if the construction is not correct. Forexample, mechanical stresses in different directionsmust be checked carefully.Fig. B for Box 2Polar diagram showing the dependence ondirection of the stiffness (E-Modulus) of a materialwith a single fibre directionComposite materials have built-in stresses becausefibre and matrix material (plastic) have differentcoefficients of thermal expansion, CTE. Thismeans that each ply has different CTEs in differentdirections. Non-symmetrical laminates may thereforecurve and show other deformations when coolingfrom the curing temperature to room temperature,Fig. C.

33Fig. C for Box 2Examples of symmetrical and unsymmetricallaminates1 A single ply expands mainly across the fibre direction2 A (0/90) laminate is balanced and expands equallyalong the 0 and 90 axes, but the structural asymmetrywill cause it to curve3 A (0/90/90/0) laminate is both balanced and symmetrical.It will stay flat during temperature changesand change dimensions equally along the 0 and 90axesBox 3METALLISATIONMetallisation is necessary if composites are to beused in antenna applications. Antennas are mainlymetallised with copper or gold. Composite systemsthat lend themselves to metallisation are those ofepoxy and thermoplastic composites with Kevlar,glass or carbon fibre reinforcement.The requirements for good metallisation are:- Even distribution of metal- High surface smoothness- Good bonding- Low porosity- No blisters- Good environmental endurance (especially whensubjected to temperature cycling).Ericsson Radar electronics uses three differentmetallisation methods for antennas. The simplestmethod is bonding. A metal foil is bonded to thecomposite. The matrix material of the composite isoften used as the adhesive in what is called cocuring.This method can only be used for flat orsingle-curved surfaces.indirect metallisation is done in pre-preparedmoulds. The mould, which is made of aluminium orstainless steel, is given a deposit of copper or gold.When the composite material is laid up and cured,the metal bonds to the composite, aided by a specialadhesive layer. Aluminium moulds do not haveto be pulled off. They can instead by dissolvedchemically, which makes it possible to metallise theinside of complicated structures.The third method is a direct galvanic method,through which metallisation is applied to the finishedcomposite. The main disadvantage of thismethod has been bad bonding, but it is very usefulfor increasing the thickness of existing metallisation.References1. Derneryd, A.G., Ingvarson, P., Johansson,F.S., Pettersson, L.E. and Shuley,N.V.Z.: Design of a dichroic subreflectorfor an offset reflector antenna. Jina, Nice,1986.2. Derneryd, A.G., Ingvarson, P., Johansson,F.S., Pettersson, L.E. and Shuley,N.V.Z. Dichroic subreflector for satellitecommunications antenna applications.ICEAA, Turin, 1989.3. DahlsjS, 0., LjungstrSm, B and Magnusson,H.: Fibre-Reinforced Plastic Compositesin Sophisticated Antenna Designs.Ericsson Review 64 (1987) 2, pp50-57.

CCITT Standardisation ofTelecommunications ManagementNetworksWalter WidlEffective administration and management of complex telecommunication networksrequires sophisticated management systems. The ongoing deregulation in manycountries means that network providers are free to buy equipment from severalsuppliers. This has led to increasing demands for standardisation in the fields ofoperation, administration and maintenance.CCITT started to study these questions in 1985, using a basic concept calledTelecommunications Management Network (TMN). The complexity of the problemsinvolved makes it likely that the standardisation work will be going on for several years.The author describes the situation in this standardisation domain in the middle of 1991.The first telecommunication networks to bebuilt were completely analog Plesiochronousdigital networks were then developed,and now the time is ripe for synchronousdigital networks. Future telecomnetworks will contain equipment of all threetypes. This poses a question: How arethese complex networks to be administeredand maintained at a reasonable cost?Some important reasons for the introductionof sophisticated network managementsystems are demands for:- possibilities of introducing new services- high quality of service-efficient working methods in the operationof networks- possibilities of reconfiguring networksand-competition from private network operators.Box 1Organisations involved in TMN standardisationCCITTComite Consultant InternationaleTelegraphique et TelephoniqueISOInternational StandardizationOrganizationETSI European TelecommunicationsStandards InstituteANSIAmerican National StandardsInstituteRACEResearch and Developmentin Advanced Communicationsfor EuropeEUROTELDEV European TelecommunicationsDevelopment (ITU)EURESCOM European Institute for Researchand Strategic Studiesin TelecommunicationMany network operators use different managementsystems for operation, maintenanceand adminstration. Centralisation ofmanagement is difficult, because differenttypes of terminals, transmission systemsand databases are used for the three categoriesof activities. One solution to theproblem is to introduce a management systemcapable of coping with all the tasksinvolved. The system should permit centralisedmanagement based on decentralised,computer-controlled functions.In 1985, CCITT Study Groups IV and XVbegan to discuss matters related to theoperation and maintenance of intelligenttransmission equipment. This led to the introductionof the Telecommunication ManagementNetwork (TMN) concept, i.e.management systems with standardisedfunctions and interfaces. In 1988, the workof the study groups resulted in CCITT Rec.M.30 2 , which defines the basic principles ofTMN. Rec. M.30 is an "umbrella recommendation",introducing a number of TMNrelated M-recommendations, such asM term listing a set of TMN terms on whichCCITT has agreedM meth defining a method of selecting protocolsM app defining a limited set of TMN managementservicesM lunc defining a limited set of TMN managementfunctionsM gnm defining a generic network informationmodelM cal a catalogue of management informationstored in the ManagementInformation Base (see below).Recommendations G.771 and G.773 werealso issued in 1988. Rec. G.773 definesprotocols for standardised interfaces betweenmanagement and transmissionequipment.Management according to the TMN conceptcovers a wide range of operation andmaintenance activities, e.g. fault management,performance management, configurationmanagement, accounting management,and security management. Serviceand business aspects are also considered.It is therefore a matter of course that theTMN should be studied not only by CCITTbut also by other national and internationalstandardisation bodies, e.g. ISO, ETSI,ANSI, Network Management Forum,RACE, EUROTELDEV and EURESCOM,Box1.

35WALTER WIDLEricsson Telecom ABPrinciples and Architecture of aTelecommunicationsManagement NetworkThe purpose of a TelecommunicationsManagement Network is to support administrationsand private network operators inthe management of their telecom networksin a flexible and effective way. A TMN providesthe telecom network with managementfunctions and offers facilities for communicationbetween the TMN and thetelecom network. The basic principle underlyingthe TMN is therefore to provide anorganised network structure that allowsvarious types of Operations Support Systemsto be connected to telecommunicationsequipment. This is achieved by usingan agreed architecture with standardisedprotocols and interfaces.An important feature of the TMN is the separationof management and telecommunicationfunctions. A network operatorshould be able to manage a wide range ofdistributed equipment from a limited numberof management nodes. The TMN willessentially function as an open system withfull connectivity between all managementnodes and all managed equipment.A TMN can vary in size from a simple connectionbetween one single OperationsSystem (OS) and a single piece of telecommunicationequipment to complex networksinterconnecting many different typesof OS and telecommunication equipment.It can provide a number of administrativefunctions and offer communication bothbetween the OSs themselves and betweenthe various parts of the telecom network.Fig. 1 is an overview of the structure of aTMN and the telecommunication equipmentit interworks with. The communicationnetwork of the TMN can include manytypes of digital transmission equipmentand associated support equipment, suchas plesiochronous and synchronous transmissionsystems, switching systems, multiplexers,and signalling terminals. In thecontext of TMN, each set of managedequipment is called a Network Element.The TMN is essentially a separate networkthat interfaces a telecom network at severalpoints to receive information from it andto control its operation. However, a TMNoften uses different parts of the telecomnetwork for its communication.Three basic aspects must be consideredwhen planning and designing a TMN-functional architecture- physical architecture- information architecture.TMN functional architectureThe functional architecture describes thedistribution of functionality within the TMN.Fig. 1General relationships between a TMN and atelecom network. Complicated terminal equipment,such as PABXs, can belong to the TMNOS Operations SystemDCN Data Communication NetworkEXCH ExchangeTRANS Transmission systemWS Work Station

36Box 2SURVEY OF TMN FUNCTION BLOCKSBox 4FUNCTIONAL SUBCOMPONENTS within theTMNFig. 2Function Blocks in the TMNOSFMFNEFOAFWSFOperations System Function blockMediation Function blockNetwork Element Function blockQ-Adapter Function blockWork Station Function blockOSFMFNEFQAFWSFOperations System Function blockhandles application processes visibleto the users, such as business,service and network managementMediation Function blockconverts information, e.g. translationbetween Managed Objectshandles data, e.g. data concentration,reduction, editingmakes decisions, e.g. regardingthreshold values, routingstores data, e.g. data identifyingequipment and networksNetwork Element Function blockhandles telecommunication processes,e.g. for switching and transmission- is involved in telecommunicationsupport processes, e.g. fault localisationand protection switchingQ-Adapter Function- converts non-standardised MCFs(Message Communication Function),transmitted via non-standardisedM-interfaces, into standardisedMCFs, transmitted viastandardised interfacesWork Station Function blockmanages user terminals, e.g. displayof information, transfer of users\ r\ m m 1 r\ f-i oMAFMIBICFPFMCFqHLPIHMAManagement Application Functions- needed for management functions,such as Manager (M) and Agent (A).MAF appears in NE as NEF-MAF, inMD as MF-MAF, and in OS as OSF-MAF. NEF-MAF performs functionsnecessary for serial connection of severalNEs. MF-MAF handles and storesdata and makes decisions. OSF-MAFperforms functions necessary for serialconnection of several OSsManagement Information Base- stores management information relatedto Information modelsInformation Conversion Function- gives the relationships between differentinformation models, e.g. betweenobject-oriented and non-object-orientedmodels as well as between modelswith different types of object-orientationPresentation Function- converts information into a formatwhich is intelligible to the userMessage Communication Function- is used by function blocks for informationhandling. MCF is structured accordingto the OSI reference model,with seven layers. Information is transferredby means of the Data CommunicationFunction, DCF, which uses layers1-3High Level Protocol Interworking- is needed when the highest levels ofMCF (layers 4-7) are to be convertedHuman-Machine Adaptation- is required for conversion from the TMNinternal Q-intertace information modelinto the F-interface information modelBox 3REFERENCE POINTS BETWEENBLOCKSFUNCTIONTEFqxgfmTMN external function blocksreference point between TMN entitiesreference point between separate TMNsreference point between WSF and operatorreference point between WSF and TMNinternal function blocksreference point between QAF and TMNexternal function blocksBox 5FUNCTIONAL COMPONENTS outside the TMNMEFSEFMCFmMaintenance Entity Function- contains the functions of the transmissionnetwork, e.g. for transmission andswitchingSupport Entity Function- contains support functions for thetransmission network, e.g. power supplyMessage Communication Function- is used by function blocks for informationhandling. MCF is structured accordingto the OSI reference model

This functionality is represented by FunctionBlocks consisting of Functional Subcomponents.Function Blocks are containedin building blocks through which aTMN of optional complexity can be implemented.A TMN comprises the following functionblocks. Fig. 2:OSF Operations Systems Function blockMF Mediation Function blockNEF Network Element Function blockQAF Q-Adapter Function blockWSF Work Station Function block.NEF, QAF and WSF are partly outside theTMN. Box 2gives an overview of the purposeof the different function blocks. Thefunction blocks represent general basicfunctions which are used in different managementactivities.Function Blocks/Functional Subcomponentsare separated from each other byReference Points. The different referencepoints, designated q, f, g and x, are listed inBox 3. For example, between WSF andOSF there are reference points f, and betweendifferent OSFs there may be referencepoints x andq depending on whetheror not the OSFs belong to the same TMN.Function Blocks within a TMN can be describedin more detail by the FunctionalSubcomponents shown in Boxes 4 and 5.The physical implementation of a referencepoint is called interface. An interface cantransfer information to several TMN entities,as exemplified in Fig. 22.Function Blocks and physical implementationscan be defined by means of FunctionalSubcomponents. Box 6 exemplifies theimplementation of TMN entities throughfunction blocks and functional subcomponents.Fig. 3 exemplifies the connection of networkelements to the TMN. The relationshipsbetween function blocks and theirphysical implementations are shown, aswell as the relationships between functionalreference pointsq and the physical Q-interfaces. TMN entities require for theircommunication the functional subcomponentMCF (Message CommunicationFunction). MCF uses the Data CommunicationFunction, DCF, for transfer of information.Fig. 4 shows how Maintenance Entities,ME, and Support Entities, SE, with non-Box 6aEXAMPLES OF FUNCTION BLOCKS AND FUNCTIONAL COMPONENTSBox 6bEXAMPLES OF IMPLEMENTATIONS WITHFUNCTION BLOCKSMOMandatory (Main Function Block)OptionalFor the WSF to be present, either the MF orOSF must also be present.Within this table, where more than one name ispossible, the choice of the building block nameis determined by the predominant usage of theblock.IMPLEMENTATIONSOS Operations SystemWS Work StationMD Mediation DeviceNE Network ElementQA Q-Adapter

Fig. 3Example of TMN physical implementation. Thecorrelations between implementation and functionblocks are shownFig. 4Maintenance and support entities without standardisedQ-interfaces are connected to the TMNvia Q-adaptersstandard interfaces, M, are connected tothe TMN via Q-adapters and Mediation Devices.The functional subcomponents responsiblefor transfer of information are notshown in this figure.Fig. 5 illustrates the connection of Q-Adaptersin the case of parallel and series M-interfaces, respectively.The function blocks are connected to eachother through communication functions.This leads to a number of different communicationdemands which are described insection "Communication Model".TMN physical architectureThe physical architecture describes physicalentities and interfaces within a TMN.TMN functions can be implemented i a varietyof physical configurations. Fig. 6shows a generalised physical architectureof a TMN containingOS Operations SystemsMD Mediation DevicesDCN Data Communication NetworksNE Network ElementsQA Q-AdaptersWS Work Stations.The interfaces shown on either side of DCNare actually one single interface betweenend systems for layers 4 and above. Forlayers 1 to 3 they represent the physical,link and network interface between an endsystem and DCN.TMN entities are connected via standard-

Fig. 5Example of connection of maintenance entitiesvia Q-adapters when the M- interfaces are paralleland serial respectivelySEQ Support EquipmentMCN M-Communication NetworkM(P) Parallel M-interfaceM(S) Serial M-interfaceised Q-interfaces. F-interfaces are used forconnection of workstations, and X-interfacesare used when several TMNs are to beinterconnected. In some cases, the Q-interfacealso transfers information related toF- or X-interfaces, as indicated in parenthesisin Fig. 6. Other examples of implementationare shown in Figs. 3 and 4.TMN information architectureThe information architecture describes thedifferent types of management informationthat have to be exchanged between thefunction blocks. Transfer of managementinformation is based on Manager/Agent relationships,management domains, sharedmanagement knowledge (SMK), objectorientation,and entity-relations. The informationarchitecture is based on- a Management Layer Model-an Information Model-an Organisational Model.These models are described below.TMN specificationThe introduction of TMN in a telecom networkinvolves the intricate task of applyingand amalgamating the various architectures.A complete specification of all TMNresources needed to ensure a functional,flexible and expandable TMN will be facil-Fig. 6Generalised physical architecture of the TMN withthe different interfaces indicatedO Q-interfaceF F-interfaceX X-interface

40TMN Management services:• paths in the transport network• customer access• switching network• tariffs and charging• trafficTMN Management Components that are part ofthe service "Management of Paths in the TransportNetwork"• Performance measurement• Bringing into service• Protection switching• Protection routing• Failure detection• Fault localisation• Fault correction• Verification• Restoration of network• Configuration of terminating equipmentTMN Management Functions that are part of theservice "Management of Paths in the TransportNetwork"• Performance Management• Fault Management• Configuration ManagementFig. 7Examples of TMN Management Services, Componentsand Functions. The terms are the subject ofCCITT discussions and may be changeditated if a number of models are made.Compatibility between the following modelsis necessary:- Management Layer Model- Information Model-Organisational Model-Communication Model-Transport Network Architecture Model.The models are partly based on the TMNinterface specification methodology, whichdescribes the procedure for defining TMNinterfaces. 4 The content of the differentmodels has not yet been fully defined.Management Layer modelEach management activity to be supportedby the TMN is described as a TMN ManagementService. The service, in turn, isbuilt up of TMN Management Components(the same component may appear in variousservices), and each component can bedivided into TMN Management Functions(the same function may appear in variouscomponents). Fig. 7 exemplifies someTMN Management Services and the TMNManagement Components included in theTMN Management Service "Managementof Paths in the Transport Network".The Management Layer model describes-a suitable division of the total managementsystem in a number of layers- which tasks are handled in the respectivelayers.A network operator's business objectivesand operational strategies determine thecomposition of his maintenance requirementsand, consequently, the TMN ManagementServices he needs. The ManagementLayer model permits a particularmanagement activity to be divided intofunctions which are placed in a series ofrecursively nested domains, Fig. 8. Eachdomain is under the control of an OperationsSystem Function Block (OSF) and iscalled an OSF domain. All information conveyedwithin a domain is transferred at referencepoints q. An OSF domain may communicatewith one or more subordinateOSF domains. The model of the controllingOSF domain (Manager) includes the objectsthat belong to the subordinate OSFdomain (Agent). The ultimate objective is tomanage physical or logical resources - inthe TMN called Managed Objects (MO).The Management Layer Model in Fig. 9shows that there are several OSFs in aTMN. They cooperate according to theprinciples shown in Fig. 8. As demonstratedin Fig. 3, Network Elements (NE) can beconnected to OSF directly or via an MD.Fig. 9 corresponds to the "complete" case.Fig. 8 corresponds to the case of directconnection of NE, which elucidates the recursivityof the nesting of domains.Fig. 8The functions needed for a management activitycan be located in a series of OSF domains, whereone domain is pari of the next, etc. Each domainis controlled by its own OSFThe functions in the different layers performthe following tasks:The Network Element Layercontains the Network Elements and isresponsible for the management of thesmallest entities and functions in NEsThe Network Element Management Layercontrols and coordinates a subset ofNetwork Elements. It compiles statistics,logging data and other data relatedto its Network Elements, and permitsinteraction between the Network ManagementLayer and the Network ElementsThe Network Management Layercontrols and coordinates all NetworkElements in the network. It permits networkmodification and interacts with theService Management Layer in mattersrelated to performance, usage and networkavailability

41The Service Management Layerhandles the contractual aspects of services,such as interfaces between customersand the network operator; interactionwith service providers; whatstatistical data a customer should haveaccess to; and interaction with the BusinessManagement LayerThe Business Management Layerhandles the network operator's totalcommitment vis-a-vis customers, suchas agreements between network operators.Some TMN Management Services - andthus TMN Management Components andTMN Management Functions - can befound in a number of Management Layersas illustrated in Fig. 10a. Fig. 10b shows asan example the TMN Management Service"Management of Paths in the TransportNetwork", which involves the three lowestManagement Layers.Information ModelThe Information model deals with the ManagedObjects and their relationships.Fig. 9TMN Management Layer modelIn certain cases, a Management Layer may beomittedFig. 10aManagement Layer modelTMN Management Services include TMN ManagementComponents which in turn consist ot TMNManagement Functions. A TMN ManagementService can be located in several managementlayersFig. 10bThe TMN service "Management of Paths in theTransport Network" employs three of the managementlayers. Examples of TMN service componentsand functions are given

42Fig. 11Example explaining the concept Object-orientatedmodelling. A Managed Object is the data image ofa resource. Each Managed Object belongs to anobject class; an object class may be a subclass ofanother object class. The subclass inherits all theproperties from the superior class; the class treeshows the inheritance hierarchy. An object classis characterised by attributes, categories andvalues. An attribute may be the object-relateddistinguishing namePhysical and/or logical items that can bemanaged and supervised are called manageableresources. Typical examples arecircuits, equipment, event logs, event reports,and end points of trails. In each ManagementLayer there are management interfacesfor communication between managingand managed systems. Viewed fromthe managing system, through the managementinterface, the resources in thecontrolled system appear as Managed Objects.The Managed Objects are thereforedata images of the physical and logical resources.There is not necessarily one-to-one mappingbetween Managed Objects and resources,i.e. a resource may be related tonone, one or several Managed Objects,and a Managed Object may be related tonone, one or several resources.The information model handles ManagedObjects and their relationships by employingobject-orientation and entity-relationtechniques. Object- orientation is a methodfor methodical description of the ManagedObjects. Entity-relations indicate the relationshipsbetween the two objects in a pair.Object-orientationEach Managed Object belongs to an objectclass, which may be a subclass of anotherclass. The subclass inherits all the propertiesof the class from which it has beenderived. The subclass refines the class definitionby new properties being added tothose included in the superior class. A particularobject of an object class is called anObject Instance.The different classes can be arranged toform a Class Tree, which shows the inheritancehierarchy. The Class Tree is basedon relationships of the "ISA" type. Fig. 11illustrates the rules of object-orientation.The Class Tree shows, for example, that acoaxial transmission system ISA transmissionequipment; in other words, that acoaxial transmission system is "derived"from transmission equipment. Class Treespermit the reuse of specifications, whichsimplifies data handling and reduces theneed for data storage.A Managed Object has the following characteristics:- the attributes visible at its boundary. Attributescan be assigned one or more values- the management operations that may beapplied to the Managed Object. Someoperations manipulate the values of aManaged Object; for example, GET,SET, ADD, REMOVE a value. Other operationsaffect the Managed Object itself:CREATE or DELETE the Managed Object- the notifications emitted by the ManagedObject-the behaviour exhibited by a ManagedObject in response to management operations.

43Fig. 12Example of entity-relations and relationship rulesLTREGAPTrailLine terminalRegeneratorClient-to-Server Access PointEnd-to-end connection in a transport networklayerEntity RelationsA model is created which defines the relationshipsbetween Managed Objects, anda set of rules is used to define the EntityRelations that may exist. A relationshipbinds attributes of two objects to each other;the objects may belong to the same ordifferent Management Layers. The numberof Object Instances involved in a relationshipis identified. Relationships may evenexist between instances of the same object;they are then called recursive relationships.Relationships can be described by applyingthe following orthogonal relationshiprules:-containingan object contains another object (physicalor logical decomposition)-terminatinga logical connection between logical objects-linkinga physical connection between physicalobjects- managinga managing relationship between objects-listinga point-to-multipoint relationship betweenobjects.Fig. 12 shows the basic rules for Entity Relations.In order to be consistent, the term"entity" has been replaced by "object". TheFigure shows examples of relationshiprules and an example of a ManagementInformation Tree based on the relationshiprule "containing".The Figure shows, for example:- A first object containing n Object Instancesis related by certain rules to a secondobject containing m Object Instances- A line terminal is linked to a regenerator.A Client-to-Server Access Point terminatesa Trail- An Operations System controls a MediationDevice, which controls a NetworkElement- A bay contains shelves.The containment relationship can be usedto obtain the Management InformationTree shown in Fig. 12:DIG-MUX (which IS A transmission equipmentaccording to Fig. 11) contains replaceableunits, or a replaceable unit ispart-ofDIG MUX.Each Managed Object is identified by aname. The name can be derived by combiningthe name of the superior object in theManagement Information Tree with a namingattribute (name binding). The ManagementInformation Tree can be used forname binding.There are manageable resources in thedifferent Management Layers, both in telecomnetworks and TMN networks. Thefunction of the telecom network is based onthe resources of the telecommunicationequipment. The equipment appears as resourcesin Network Elements, and Network

44Fig. 13Interworking between Manager, Agent andManaged ObjectsFig. 14Shared Management Knowledge (SMK)SMK is related to a pair of communicatingfunction blocks. Each function block has to usethe same SMK to ensure communication. If theManager and Agent processes are located indifferent physical TMN entities, they communicatevia Q-interfaces. If they are located within thesame TMN entity, they are interconnected bymanagement functions via internal referencepointsElements appear as resources in networks.Several detail functions in a lowermanagement layer may, in a higher layer,be treated as combined functions in a blackbox. Descriptions of the functions of thedifferent resources as Managed Objetsand their interconnections are stored inseparate Management Information Bases(MIB). Correspondingly, an MIB containsdetailed specifications for all Managed Objectsin the TMN. It is also to contain specificationsof the functions and configurationof the TMN entities that control the NetworkElements. An MIB therefore provides thebasis for the information model.Organisational ModelThe organisational model describes-the ability of the managing process totake on a controlling role (Manager) and/or to be controlled (Agent)-the interworking between the Managerand Agent parts of the process-what is needed to make interworkingpossible.For a specific management action the TMNprocess will take on either of the two possibleroles of Manager and Agent. TheManager controls objects in its part of theprocess. An Agent follows the TMN directivesgiven by a Manager. Part of the role isto return the data image of Managed Objectsto the Manager. The principal relationshipsbetween Manager, Agent and Objectsare shown in Fig. 13.Multipoint relationships can exist betweenManager and Agent. One Manager may beinvolved in information exchange with severalAgents, and one Agent may exchangeinformation with several Managers.For systems to be capable of interworking,they must use the same protocol and TMNFunctions, and have common ManagedObjects, Object Instances, and Containingrelationships (name binding).Systems that have these concepts in commonare said to have the same SharedManagement Knowledge (SMK). Fig. 14shows that SMK is related to one pair ofcommunicating functions. SMK12 is differentfrom SMK23. If the Manager and Agentprocesses take place in physically separatedTMN entities, communication betweenthem will be via Q-interfaces. If Managerand Agent are in the same TMN entity, theyare connected by management functionsvia internal reference points (r).Start of information exchange requiresprocesses which ensure that the sameSMK is used by the interworking interfaces.These processes are called static or dynamiccontext negotiations. A static processnegotiates SMK at the beginning of theinformation exchange. In a dynamic process,SMK is affected by several conditionsand is modified during the exchange of information.The Managed Objects can be assigned differentManagement Domains, each ofwhich corresponds to a specific functional,geographical and/or organisational area.Exemples of functional areas are faultmanagement, billing management, and security.Within a Domain, the managementprocess can be adapted to specific requirementsof the network operator - related tofunctions, for example. The roles of Managerand Agent can be temporarily assignedand possibly also modified.Management Domains can be overlapping,contained in each other, or interacting.Managed Objects in overlapping domainsbelong to various domains simultaneously.The main reason for introducing the Domainconcept is to make it possible for net-

Fig. 15Exchange of information between NE and OS. TheMessage Communication Function (MCF) and theData Communication Function (DCF) are used.DCF is implemented in the data communicationnetwork, DCN, and located in the lower layers ofthe OSI reference model.The TMN entities OS, MD and NE contain MessageCommunication Functions, MCFFig. 16Survey of standardised protocol suiteswork operators to divide their objects accordingto their own requirements, policy,etc.Communication ModelThe communication model describes thefunctions, protocols and messages involvedin the exchange of information betweenTMN entities.Fig. 15 shows, as an example, the exchangeof information between a Managerin OS and an Agent in NE, by means of theMessage Communication Function, MCF,and the Data Communication Function,DCF. DCF is implemented in the DataCommunication Network, DCN. LAN,WAN, SS#7, X25 or embedded communicationfunctions can be used for DCN. TheDCF functions are to be found in the lowerlayers of the OSI reference model. OS, MDand NE contain message communicationfunctions (MCF), Fig. 3. The MCF conceptcan even be used outside the TMN, Fig. 4.A set of requirements has to be establishedfor the most likely communication needs,e.g. simple transactions, file handling, filetransfer, file access, or combinations ofthese procedures. Other characteristicsmust also be specified: transfer capacity,reliability and transit delay.Q-interfaces are used for exchange of informationbetween Network Elements andTMN entities, and between TMN entitiesthemselves. F-interfaces are used betweenworkstations and Network Elementsor TMN entities, and X-interfaces are usedbetween different TMNs. So far, CCITT hasonly specified Q-interfaces for managementof transmission systems.The Q-interface is defined in Rec. G.773 asfollows:-full 7-layer stack protocol suites B1, B2and B3, used in applications for e.g. synchronousnetworks- short-stack protocol suites A1 and A2,used primarily in applications for e.g. plesiochronousnetworks.Fig. 16 gives a survey of the proposed protocolsuites. An extensive list of referencesdefining protocols is included in Rec.G.773.The protocols used in the upper part of theapplication layer in the OSI ReferenceModel are CMIP (Common ManagementInformation Protocol) and FTAM (FileTransfer, Access and Management). 8CMIP is a transaction-oriented protocol

46Fig. 17Layers N and N+1 in the OSI reference modelcommunicate by means ot service primitives.A Request is sent from one unit. On the receivingside it is interpreted as an Indication. Thereceiving side gives a Response. The Response isreceived as a ConfirmBox 7EXAMPLES OF SERVICESCMISE servicesACSE servicesROSE servicesM-CREATEM-DELETEM-SETM-GETM-ACTIONM-EVENT-REPORTA-ASSOCIATEA-RELEASEA-ABORTRO-INVOKERO-RESULTRO-ERRORRO-REJECTsuitable for alarm transmission and changeof subscriber data. FTAM is expected to beused for transmission of large quantities ofdata, e.g. charging data and statistics.The work on a complete TMN standard isnow concentrated on the preparation ofmessage descriptions for different applications.The Common Management InformationService Element (CMISE)- provides a set of general-purpose communicationservices used for the exchangeof information and commands inthe administration of systemsThe Association Control Service Element(ACSE)- provides services for the establishmentand break-up of relationsships betweenManager and AgentThe Remote Operations Service Element(ROSE)- provides a set of general-purpose servicesused by CMISE to invoke remoteoperations and receive the results ofthese operations.Examples of services rendered by CMISE,ACSE, and ROSE are given in Box 7.Fig. 17 illustrates the Service Primitivesused for communication between layers inthe OSI Reference Model. The primitivesare used by layers on the initiating side of aconnection to demand services from thenext lower layer. The following procedureapplies:The N+1 layer invokes an N-layer servicewith REQUESTThe N-layer indicates to the N+1 layer theservice with INDICATIONThe N+1 layer gives an answer to the N-layer with RESPONSEThe N-layer confirms the execution of theservice with CONFIRM.The communication by means of primitivesis repeated layer by layer through the completeOSI stack.The transmission of an alarm from NE toOS is illustrated in Fig. 18 as an example ofthe use of service primitives. This exampleshows only the use of primitives in the applicationlayer, but similar processes takeplace between other layers too. The transmissionis described in itemised form. It is atwo-stage process: connection is establishedby means of a handshake procedure,and the TMN message is then transmitted.Handshake-A Managed Object in NE emits a notificationto an Agent in NE, indicating thatan abnormal condition (resulting in analarm) has been detected- The Management Application Function inNE (NEF-MAF) sends a request (1) toCMISE in order to establish a connectionbetween NE and OS-CMISE forwards the request to ACSEusing the primitive A-ASSOCIATE request(2)- ACSE - containing the service A-ASSO­CIATE, which is capable of establishingconnections - forwards the connectionrequest to the next lower layer. After therequest has passed several layers, anindication is received by OS on the receivingside. It has been sent on throughthe OSI stack and finally reached CMISEby means of the primitive A-ASSOCIATEindication (3)- OSF-MAF acknowledges the request bysending an answer which is received inNE. The connection is completed whenthe NEF-MAF receives the confirmation(4).TMN message transmission- An alarm is now to be transmitted. NEF-MAF sends an M-EVENT-REPORT requestto CMISE (5)-CMISE receives the request and callsROSE with an RO-INVOKE request (6)- After a procedure similar to that for establishingthe connection, the alarm messagereaches OSF-MAF by means of theprimitive M-EVENT-REPORT indication(7).As can be seen from this example, theservices CMISE, ACSE and ROSE areused in different stages of the communicationprocess.Telecommunication networkarchitectureThe managed and supervised telecom networkcan be described by means of differentarchitectures 7 , such as

Fig. 18Transmission of an alarm from a network elementto the TMN. Exchange of information betweenadjacent layers is by means of service primitivesMAFCMISEACSEROSEManagement Application FunctionCommon Management Information ServiceElementAssociation Control Service ElementRemote Operations Service ElementFig. 19Telecommunication network management withTMN, exampleMARManagerAgentResource-a transport network architecture, whichdefines a number of layers for different bitrates and services-a regional network architecture, whichdefines layer parts containing organisational,hierarchical and geographical regions.Application principles for TMNThe architectures and models previouslydescribed are tools which facilitate the introductionof the TMN. Depending on thenetwork operator's management demandsand organisation, and on the complexity ofthe managed network, application of thedifferent models will be an iterative process.The TMN methodology can be based onthe following sequence of steps:-the TMN Management Layer modeldefines the TMN layers, TMN servicesand components- the organisational modeldefines the structure of the TMN and theTMN functions within and between ManagementLayers-the information modelconverts the resources to Managed Objectsand defines object classes, attributesand values. Each Object Instancein a Managed Object class is identifiedthrough name binding. TMN operationsand notifications to and from ManagedObjects lead to TMN Management Functions,which are transmitted over Q-interfacesthrough standard messages andprotocol suites.The managed telecommunication andTMN resources, and their relationshipswithin each TMN Management layer orbetween TMN layers, are stored in MIB.

48Fig. 20Entity-relations for Equipment FragmentObject classes in the Network box and in theTermination Point box may appear in otherfragments tooFig. 21Entity-relations for Alarm Surveillance FunctionalArea Fragment

Box 8EXAMPLE OF OBJECT CLASSES FOR THE"EQUIPMENT" FRAGMENTEQUIPMENTThe "Equipment" object class is a class of ManagedObjects that is contained within the "ManagedElement" class and represents physical unitswhich perform telecommunications and/or TMNfunctions. "Equipment" may be nested within other"Equipment" object classes, thereby creating acontaining relationship. An Object Instance belongingto this class is a single-location one.MANAGED ELEMENTThe "Managed Element" object class is a class ofManaged Objects that contains other ManagedObjects, which represent telecommunication and/or TMN implementations and functions. An ObjectInstance belonging to this class is a single-locationone.SOFTWAREThe "Software" object class is a class of ManagedObjects that represents an arbitrary set of storedinstructions, which can be used as programs anddata tables. "Software" may be nested within other"Software" object classes, thereby creating a containingrelationship. "Software" can be contained in"Equipment", for example.Fig. 22Use of the Organisational modelExample of Manager-Agent processesMCF Message Communication FunctionMAF Management Application FunctionMO Managed ObjectBox 9EXAMPLES OF OBJECT CLASSES FOR THE"ALARM SURVEILLANCE FUNCTIONAL AREA"FRAGMENTALARM RECORDThe "Alarm Record" object class is used to definethe information stored in the log of received alarmreports. The semantics of the object class - itsattributes and behaviour - is derived from the alarmreports (Alarm notification) described in RecommendationX.733 (ISO/IEC101 64-5).EVENT FORWARDING DISCRIMINATORThe "Event Forwarding Discriminator" object class- a subclass of "Discriminator" - is used to definethe conditions that must be satisfied by potentialevent reports before a report is forwarded to aparticular destination. The semantics o( this objectclass - its attributes, management operations andbehaviour - is described in RecommendationX.734 (ISO/IEC 101 64-5).Application of the TMN methodology issimplified by diagrams specifying the relevantEntity Relations. This leads to-a Class Tree, defining the InheritanceHierarchy-a Management Information Tree, to beused for name binding-a syntax (Abstracts Syntax Notation,ASN-1) used to provide a uniform way ofspecifying object classes, attributes, notifications,and operations.In future, a catalogue containing ManagementInformation, such as Managed Objects,Relationships, TMN ManagementServices, Components and Functions, willfacilitate the introduction of TMN.The "Discriminator" object class is used to definethe conditions governing the management services.The semantics of this object class - its attributesand behaviour - is described in RecommendationX.734 (ISO/IEC 101 64-5).LOGThe "Log" object class is used to define the conditionsgoverning the logging of information in themanagement APDUs. The semantics of this objectclass - its attributes and behaviour- is described inRecommendation X.735 (ISO/IEC 101 64-6).The "Log Record" object class is used to define therecords contained in a class "Log" Managed Object.The semantics of this object class - its attributesand behaviour- is described in RecommendationX.735 (ISO/IEC 101 64-6).The "Event Log Record" object class is used todefine the information stored in the log as a result ofreceived events. This is a superordinate class (Superclass)from which reports (Records) on specifictypes of event are derived.Generic application exampleThe example in Fig. 19 illustrates a genericcase of network management by TMN.The Network Element Layer contains themanaged resources of the telecommunicationnetwork, i.e. the equipment that performstelecommunication and supportfunctions.The Network Element Management Layercontains the Mediation Devices (andsometimes Operations Systems) with theirresources, e.g. databases with informationabout the function of managed NetworkElements.The Network Management Layer containsOperations Systems with their resources,e.g. databases with information about thefunction of the network. Telecom networkscan be divided into transport layer networks,one for each characteristic signal(bit rate, framing). Each transport layercontains subnetworks covering specific geographicalregions. The Network ManagementLayer can therefore contain a numberof Operations Systems, each handling itsown transport layer with various regions orits own region covering various transportlayers.The Managed Objects in each ManagementLayer can be combined in Entity-Relationdiagrams in order to establish theInformation model. Different aspects maybe considered, depending on the purposein view. Details of the telecommunicationand supervisory functions must be knownin the case of fault and performance management.For routing, it might be necessaryto consider only the end points oftrails.Fig. 20 shows Entity Relations - for transmissionequipment - and Fig. 21 those for

Telecommunication Network LayersTMN Management LayersFig. 23Relationships between telecommunicationnetwork layers and TMN Management Layersalarm supervision equipment. Boxes 8and 9 exemplify classes of Managed Objectsand their associated functions. 6The use of the organisational model is illustratedin Fig. 22, which shows the communicationbetween OS and two differentNetwork Elements, NE1 and NE2. Thecommunication paths to NE1 and NE2 arelogically independent of each other, althoughthe same Q-interface and MediationDevice are used. The Figure showsthat communication between OS and NE2only uses the three lowest layers of theMessage Communication Functions in MDand NE1. Communication between OS andNE1 involves the Management ApplicationFunction in MD.TMN principles applied toFMASFig. 23 shows the relationship between thearchitecture of the telecom network and theTMN architecture. 7 The telecom networkhas separate layers for the physical transmissionnetwork, the logical transport networkand the service network. The transportnetwork, in turn, is divided into severaltransport network layers - three in the example.Each transport network layer carriessignals belonging to a certain category,defined by bit rate, coding and frame structure.Each layer has its own Managed Objects.Fig. 24 illustrates, as an example, Ericsson'sTMN system FMAS (Facility ManagementSystem) managing, supervisingand controlling a three-layer transport network.FMAS interworks with Ericsson'sTMN system for switched networks, NMAS(Network Management System), and thatfor the Intelligent Network, SMAS (ServiceManagement System). The three layers ofthe transport network in the example carrybit rates 2, 155 and 2500 Mbit/s respectively.Each of the transport network layerscontains parts corresponding to local, regionaland national networks (network partitioning).The national network consists ofseveral regional networks, each of whichcontains a number of local networks.FMAS is divided into a number of functionalunits, corresponding to the number of layers,parts of layers and networks for eachlayer part. An FMAS contains a combinationof functional units. Which units are chosendepends on the application and on theeconomic factors to be considered.- An FMAS for the national network thuscontains the following blocks: FMAS-N/2,FMAS-N/155, and FMAS-N/2500-An FMAS for the 155Mbit/s layer containsthe following blocks: FMAS-N/155,FMAS-R/155, and FMAS-L/155.FMAS corresponds to OS in TMN and interworksvia Mediation Devices (MD) withNetwork Elements (NE) and Q-Adapters(QA).

Fig. 24An example of the use of Ericsson's managementsystem FMAS to provide operations support to athree-layer transport networkSSP Service Switching PointSCP Service Control PointFN Feature NodeN National networkR Regional networkL Local networkReferences1 Widl, W.: Standardization of TelecommunicationManagement Networks. EricssonReview 65 (1988) :1, pp. 17-23.2 CCITT Rec. M.30: Principles for a TelecommunicationsManagement Network.Doc 80, 83, 86, 87, 89, Q.23/IV ExpertsGroup, Aveiro, June, 1991.3 CCITT Rec. G.773: Protocol Suites forQ-lnterfaces for Management of TransmissionSystems. TD7, WP XV/6, Geneva,July, 1990. CCITT Rec. G.771: O-Interface Protocol Selection Process forTransmission Equipment. COM XV-R33E, Geneva, Nov, 1989.4 CCITT SGIV Geneva 23-26.1.90 Temp.Doc. 23: Revised TMN Interface SpecificationMethodology.5 CCITT Delayed Contribution by UnitedKingdom, Geneva 26-28.3.90, D49: ALayered Hierarchy for the TMN.6 CCITT Working Document by the Netherlands,Tokyo 23-26 Oct, 1990: ObjectClass Description for Equipment andSupport Object-Fragments.7 Widl, W.-.Telecommunications NetworkArchitecture. Ericsson Review 67(1990):4, pp. 148-162.8 Abramowicz, H. and Lindberg, A.: OSIforTelecommunications Applications. EricssonReview 66(1989):1, pp.2-12.SummaryTMN will have a strong impact on the technologyemployed to manage the complicatedtelecom networks of the future. Thesenetworks will have to combine the functionsof the Plesiochronous Digital Hierarchy(exchanges, multiplexers and line systems)with the functions of the new SynchronousDigital Hierarchy (cross-connects,multiplexers and line systems). Theintroduction of TMN principles for existinganalog and plesiochronous systems is expectedto extend the economic service lifeof the networks. For network operators, theadvent of TMN will ensure maximum returnson network investments, benefitsfrom reduced administrative costs, and improvedpossibilities of centralisation andautomation of network management functions.The TMN studies are making good progressand are at present primarily focusedon- information models for Network Elementsand Network Management Layers(SDH and PDH equipment)- definition of the protocols and messagesto be transported in the TMN-definition of Operations Systems in theTMN Hierarchy.-establishment of Management InformationBasesThe complexity of the studies is partly dueto conflicts of interest. Some administrationsare in favour of solutions which permitmulti-faceted network management with awide range of applications, whereas others- for the time being - are content with limitedTMN applications, albeit they want standardsin the near future. In any case, itseems likely that TMN will continue to bestudied for a long time to come.

Power Supply System BZA106 forSmall Telecommunications PlantJohan Frandfors and Niklas HafdellThe need for small, reliable power supply systems is growing, concomitantly with atrend towards smaller and more compact telecommunications equipment.Telecommunications products for new applications are also being developed. Theequipment often consumes very little power, and the reduction in volume meansgreater freedom of choice as regards installation. It must be possible to place theequipment in offices or basements; on roofs or in any place where there is sufficientspace. When sets of equipment are placed close together, ECM requirements becomemore stringent.The authors describe power supply systems based on high-frequency rectifiers,designed for small telecommunications equipments which demand high reliability,small volume and low radio interference.The systems consist of 12 A high-frequencyrectifiers which, in different applications,are combined with different types of distributionunit. The flexibility of the systemsmakes them suitable for different types oftelecommunications equipment, such asremote subscriber switches, PABXs, transmissionequipment, radio base stations,etc. Their power consumption may be betweena few hundred W and 3 kW.Many of the features demanded by themarket can now be offered. The use ofelectronics in rectifiers has resulted in reducedvolume, which is partly attributableto high-frequency conversion. Previousthyristor rectifiers were considerably largerand heavier.Fig. 1Power supply system BZA 10612, complete withrectifier and main distribution unitIn order to meet the intensified market demandsfor greater reliability, small volumeand less radio interference, the Power Divisionof Ericsson Components AB has developedthree new power supply systemsfor -48 V DC in the the BZA 106 family: BZA106 12, BZA 106 13 and BZA 106 14.Some important system characteristics-The systems have high reliability. Contributingfactors are the principle of n+1redundancy, uninterruptible power andhigh rectifier MTBF-The rectifier gives very low electromagneticinterference, both conducted andradiated. It is essential that this type ofinterference is taken into considerationwhen power systems are installed closeto - or feeding - sensitive equipment- The systems are small and light, partlythanks to the hf technology. The rackscan be placed against a wall or back toback. These characteristics make forgreat installation flexibility- All system handling is simple, both duringinstallation and extension. All units areinstalled from the front, in 19" racks, typeBAF601 or equivalent. All cable connectorsare accessible from the rack fronts- The systems are virtually noiseless sincethe rectifier conversion frequency is morethan twice the highest frequency audibleto human beings. This is very important ifpeople have to stay for any length of timein the room where the power equipmentis installed- Service and installation is simple. Therectifiers are complete units which, incase of failure, can easily be removedand replaced. All electric connections areof the plug-in type, and can thus be handledby staff with limited authorisation.Units can be changed during operation,thus avoiding costly service interrupts.BZA 106 12 for low powerconsumptionBZA 106 12 is the smallest of the threesystems. It consists of a 12 A rectifier and adistribution unit, BMG 662 001, mountedon one side of the rectifier, Fig. 1.

JOHAN FRANDFORSNIKLAS HAFDELLEricsson Components AB53The system, which is fed with 230 VAC, is Distribution unit BMG 662 001designed for small equipment, for example BZA 106 12 is intended to work only withPABX and transmission equipment. The valve-regulated batteries. Such batteriesmechanical design and the small volume must not be completely discharged, sinceenable the system to be installed at the this would shorten their life drastically. Thebottom of a telephone cabinet, at one side batteries could even be ruined. In order toof a wall-mounted cabinet or in any other avoid this, the distribution unit is equippedsuitable space.with an undervoltage monitor that issuesan undervoltage alarm at 43.0 V and disconnectsthe load at 40.5 V. The load isSystem functionMost power supply equipment for telecommunicationsplant contains batteries be­voltage is restored and the battery voltageautomatically reconnected when the mainscause of the high reliability requirements. has risen to 51.0 V. The hysteresis enablesIn order to ensure high reliability, BZA the rectifier to recharge the battery for a10612, as well as the other two new systems,has been designed as an ordinaryshort period.full-float system. The rectifier continuously The distribution unit contains a 20 A batterymaintains, through floating charge, a constantDC voltage across both the battery distribution branches and for alarms fromfuse as well as connection points for threeand the load, Fig. 2. In the case of a mains the rectifier. All connectors are placed onor rectifier failure the battery feeds the load. the front of the unit.This principle is called uninterruptible powersupply.The front contains four alarm indicators:- Battery fuse trippedThe availability of battery-powered telecommunicationsequipment is dependent - Undervoltage- Load disconnectedon the capacity of the battery. This capacity,in turn, is dependent on the battery size, The unit contains jacks for distribution of all- Overvoltage.measured in ampere hours, and the conditionof the battery. The system float-charg­alarms to a remote operations centre.es the battery with 2.27 V/cell for 24 cells orwith 6.81 V/block for eight block containers. BZA 10613 for maximumreliabilityThe condition of the battery may be improvedwith the aid of Ericsson Compo­System BZA 10613 is designed for telecommunicationplants with very high requirementsas regards limiting of transientsnents' patented cell voltage equaliser. It isdesigned for mounting across each batteryon the distributed voltage, such as PABXs.block and ensures that each block obtainsexactly the required charging current. 1 Like the others, this is an ordinary full-floatsystem.The system comprises one rack and can beequipped with up to six parallel 12A rectifiers,distribution units for direct current tothe load, and mains distribution,Fig. 2Block diagram of an ordinary full-float systemSYSTEM FUNCTIONDuring normal operation the rectifiers compensatefor the self-discharge of the batteryand thus maintain a constant DC voltage.The float-charging level varies slightlydepending on the number of cells in thebattery. The battery feeds the load during amains failure - the system is uninterruptible.The battery used in BZA 10613 maybe ventilated or valve-regulated.Charging a ventilated batteryWhen the mains is restored after a failure,the ventilated battery is automatically recharged.This is done either through peri-

Fig-3Electronic fuse BGB 950 10/- distributes a transient-limitedvoltage to the load. The fuse isplaced in the main distribution unitFig. 4Power supply system BZA 10614 can feed remotesubscriber switches, transmission equipment andradio base stationsFig. 5Rectifier BML 211 001/- may be used as an independentunit or mounted in a power cabinettogether with other rectifiers. It meets stringentrequirements as regards reliability, performanceand radio interferenceodic charging at regular intervals orthrough voltage and time-controlled charging.The method used depends on whattype ot charging equipment the customerhas chosen for the system. During chargingthe charging equipment sends a controlsignal to the rectifiers so that they increasethe output voltage to a preset charging levelof between 2.30 and 2.35V/cell. Thecharging level can be adjusted on the frontof the rectifier.Charging of a valve-regulated batteryThe voltage across a valve-regulated batterymust not be increased during charging,since this would ruin the battery. Cell voltageequalisers should be used for floatchargingof valve-regulated batteries in orderto obtain the optimum result.DistributionBZA 106 13 may be equipped with either oftwo types of main distribution unit. TypeT/BMG 661210 contains battery fuseswhile T/BMG 661 211 does not. In bothtypes the voltage is distributed to the loadvia an electronic fuse unit type BGB950101-, which contains two 10 A fuses.The electronic fuses replace the traditionalautomatic fuses that are used in systemBZA 10614, because of the stringent requirementsfor transient limiting in systemsfed by BZA 10613, Fig. 3.OperationThe electronic fuse monitors the distributedcurrent. In the case of a short circuit thecurrent is limited for a short period. If theshort circuit persists, the fuse is tripped andan alarm is initiated. Restart after failureshould be done manually. 2During a mains failure, when the batteryprovides all power, some parts of the loadcan be disconnected. This extends the reservetime for prioritised equipment. Alarmboard ROF 1370605/- has two undervoltagemonitors, 43 V and 40 V. They can controlan electronic fuse so that its load isdisconnected. The load is automatically reconnectedwhen the mains is restored.ExtensionIn addition to the main distribution unit,which is always included, BZA 10613 canbe equipped with an extension distributionunit that accommodates sixteen 10 A electronicfuses.Power system BZA 106 14 hasa large range of applicationsSystem BZA 106 14 consists of a rack thatcan be equipped with up to six parallel 12 Arectifiers, distribution units for feeding directcurrent to the load and a mains distributionunit, Fig. 4.BZA 106 14 is a flexible system that can beused in many different applications, suchas remote subscriber switches, transmissionequipment, radio base stations andother equipment powered with -48 Vthrough low-resistance distribution. Systemfunctions for battery maintenance,charging and alarm are the same as insystem BZA 10613.DistributionBZA 106 14 is equipped with either of twotypes of main distribution unit. Type 1 /BMG661110 contains 2x100 A battery fuseswhile 1/BMG 661 111 has none. Both typesdistribute the voltage to the load via automaticfuses, type BGB 951. The automaticfuses, rated at between 5 and 30 A, are

Technical Data for Rectifiers55Input dataMains voltage, single-phaseBML211 001/2BZA211 001/3Frequency rangeInput current with full load andminimum input voltageBML 211001/2BML211 001/3Power factor with 80 % loadEfficiency with full loadAbility to withstand transients from the mainsAsymmetric, phase-to-earthamplituderise timepulse durationimpedanceSymmetric, phase-to-zeroamplitudepulse durationimpedanceMeets standards for radio interferenceAC and DC sideElectrical safetyRectifierBML 211001/2BML 211001/3Output dataSystem voltageFloat charging voltageOperating charging voltageOutput currentCurrent limitingStatic regulation accuracyDynamic variation with load changesof 50-75-50%Response time with 25 % changein the loadNoise voltagePsophometric valuePeak-to-peak valueGeneral dataPermissible ambient temperatureoperationnon-destructivestorageCoolingReliabilityMTBFEncapsulation classDimensionsWidthHeightDepthWeight115 ±15% V230 ±15% V47-63 Hz9 A5.5 A0.60>0.893 kV0.5 (is50 (is45 ohms1 kV50 jis5 ohmsVDE 0878, curve BCISPR 22, curve BFCC, curve BIEC950UL listedSEMKO statement-48 V51.2-54.5 V52.8-56.5 V12 A12 ±0.3 A200 mV

56Fig. 6Efficiency curve for rectifier BML211 001/3Fig. 7Rectifier, block diagramagainst overload and short circuit. Whenthe overload or short circuit ceases, therectifier returns to normal operation.Overvoltage protectionOvervoltages may occur because of a faultin the rectifier. The load is protected fromharmful voltages by an overvoltage protectionthat is activated when the output voltageexceeds 57.3 ±0.3 V. The output voltageremains at this level for maximum fiveseconds; it then drops to approximately50 V, and an overvoltage alarm is initiated.This protective action is performed if theoutput current is higher than 0.6 ±0.4 A. Ifthe output current is below this threshold,the overvoltage protection level is raised byapproximately 1.0 V. A system containingparallel rectifiers is thus provided with selectivity.When the cause of the overvoltage hasbeen removed, the alarms must be reset byremoving the mains plug and tripping theoutput fuse for at least 30 seconds.The rectifier's "messages" as regards itsoperating status report on:-Operation-Mains failure-Overvoltage.References1. Ericsson, M. and Samsioe, P.: SupervisionSystem for Energy Equipment.Ericsson Review 64 (1987):1, pp. 2-8.2. Aksberg, A., Lundstram, H. and Samsioe,P.: Electronic Fuse lor Power Distributionin Systems Sensitive to Transients.Ericsson Review 63 (1986) :1, pp. 32-40.

ZAN 202, a System for Operation andMaintenance of TransmissionEquipmentKjell Sundberg and Kidane WoldegiorgisIn the middle of the 1980s, Ericsson introduced systems ZAN 101 and ZAN201 foroperation and maintenance of transmission equipment. Demands for functional contenthave since then grown; for example as regards facilities for assuring and monitoringthe transmission quality of the supervised network. Ericsson has now developedsystem ZAN202 to meet these new requirements.The authors describe the architecture, characteristics and functions of the system.maintenance engineeringtelecommunication transmission linestelecommunication network managementEricsson has previously introduced transmissionmaintenance system ZAN 101 andfault location system ZAN 201. Operationand maintenance system ZAN 202 is a successorto these systems. It can be used tooperate and maintain Ericsson's series7000 transmission systems and to monitoralarms from equipment from other vendors.In addition to the fault location andalarm monitoring functions provided by theearlier systems, ZAN 202 comprises functionsfor-quality measurements in accordancewith CCITT recommendation G.821- remote control of objects capable of beingso controlled.Unlike the two earlier systems, which onlyhad Ericsson interfaces, ZAN 202 will havestandardised Qx interfaces conforming tothe TMN standard now being developed byCCITT. ZAN 202 may be connected toEricsson's network management systemFMAS via the Qx interface.Development driven bycustomer requirementsThe traditional telecommunications administrationsneed to be able to-monitor their transmission networks, inorder to detect equipment and cable failuresand to maintain the transmissionquality for the telecommunications servicesthey offer their customers- quickly localise faults in the network- use the same operations support systemto supervise both older and new transmissionnetwork elements and also tointegrate the operation and maintenanceof equipment from different vendors.ZAN 202 meets these requirements by- providing functions for continuous supervisionof alarms and transmission qualityin accordance with CCITT RecommendationsG.821 and M.550- being able to localise faults in networkelements in complex networks and thusaid rapid fault clearing- providing standardised TMN interfacesso that ZAN 202 can be integrated withthe customer's own operations supportsystem or Ericsson's FMAS.Fig. 1ZAN 202 has a menu-based man-machine interfacetor the operators, which facilitates handlingof the system. The VDU terminal is compatiblewith VT100. The display is divided into astatus and a work window. The status windowshows the status of the supervised network. Thework window shows alarm and result reports andis used to input operator commands

KJELLSUNDBERGKIDANE WOLDEGIORGISEricsson Telecom ABFig. 2System architecture tor ZAN 202MMD Central computer in ZAN 202PU Peripheral UnitVDU Terminal with Visual Display UnitLT Line TerminalMUX MultiplexerRE Regenerator (two-way)Network operators who are already employingZAN201 can upgrade their systemsto ZAN 202 standard, with a minimumof reconfiguration work and discardedequipment.ZAN 202 has a menu-based man-machineinterface, which simplifies system handling.System architectureFig. 2 shows the architecture of ZAN 202.The system consists of a central computerMMD (Management Mediation Device)and a number of peripheral units, PU.Each PU is installed close to the equipmentit is to supervise and communicates withthe MMD via an analog modem interface ora serial interface in accordance with RecommendationRS485.Communication between a PU in one stationand the MMD in another employs oneof the following channels, depending on thenetwork configuration:-An Embedded Operations Channel,EOC- Free-bit channels in the bit stream at differentmultiplexing levels-Extra 0-4 kHz or 4-8 kHz channels orextra physical pairs in symmetrical-paircables.The MMD may be connected to a TMNmediation device or a router, which - viathe Q3 interface - can be connected to acentralised operations system (OS), Fig. 2.Locally, a number of VDUs and a printermay be connected to the MMD.A ZAN 202 system with an MMD can supervisetransmission equipment in several stations.Equipment that can be monitoredcomprises- Digital line systems over fibre, coaxialand pair cables- Primary and digital multiplexers- Signalling converters- Protection switching equipment-"External objects", such as power anddoor alarms, etc.In large transmission networks, severalZAN 202 may be interconnected to form anetwork, Fig. 3. Such a network conformswell to the TMN architecture in CCITT RecommendationM.30, Fig.4, and can bearranged within the framework of Ericsson'sFMAS, ref. 3, which forms part of theTMOS family or an alternative centralisedoperation and maintenance system availableto the administration. FMAS can beused for operation and maintenance ofPDH (Plesiochronous Digital Hierarchy) aswell as SDH (Synchronous Digital Hierarchy)and DXC (Digital Cross-Connect)

Fig. 3Several ZAN 202 may be used in a TMN in accordancewith CCITT Recommendation M.30OS Operations SystemDCN Data Communications NetworkWS Work StationMO Mediation DeviceQ Standardised interfaceequipment, i.e. provide integrated operationssupport to the entire transport network.System functionsZAN 202 provides functions for-collection, processing, presentation andlogging of alarms-pinpointing faulty regenerators in linesystems- bit error ratio (BER) diagnosis of line systems-measurement, processing, presentationand storing of quality data in accordancewith CCITT Recommendation G.821-generating alarms when the thresholdvalue of any of the quality parameters inRecommendation G.821 is exceeded- remote control of remote-controllable objectsvia relay contacts.In addition to these functions, which areused for the transmission network, the systemprovides functions for control andmaintenance of the supervising network.They include-configuration of user and terminal interfaceswith authorisation check (passwords)- collection of statistics relating to the communicationbetween the MMD and differentPUs.Alarm processingAlarms are connected to a PU in either oftwo ways, depending on the type of supervisoryequipment.Discrete alarms from equipment are connectedto ACU/ACM (Alarm CollectionUnit/Alarm Collection Magazine). Fig. 5.ACU/ACM scans and filters status changesFig. 4The physical architecture of TMNOA Q-interface AdapterNE Network Element

Fig. 5Discrete alarms are connected to ZAN 202 viaACU/ACMACUACMEXTAlarm Collection UnitAlarm Collection MagazineExternal equipment1LT1DIGMUXr irACM/ACU1EXT1Discrete alarminterface_JFig. 6PUs are built into the Ericsson equipment to besupervised by means of ZAN 202. PUs monitoralarmsand reports them to the MMD, which continuesthe processing so that alarm reportsare created. Alarms are also monitored viathe PU, which is integrated with the supervisedequipment, Fig. 6. Hence no externalconnections are necessary. The procedureis the same as for discrete alarms.When the MMD receives a report of a statuschange, it- identifies the equipment that has generatedthe alarm, with the aid of the informationprovided by the PU-decides whether the status changemeans that an alarm has been activatedor whether a previously detected and reportedalarm has ceased-spontaneously generates an alarm reportwhich indicates date, time, theequipment concerned and the alarmidentity and class, Fig. 7, and routes thereport to a registered receiver (VDU orprinter)- enters the report in an alarm log.The operator can request, by means of acommand,-a summary of all active alarms in thenetwork. Fig.8- a printout of the alarm log.Fault locationIn ZAN 202 the fault location concept comprisesfunctions thata indicate a faulty regenerator sectionthrough BER (Bit Error Ratio) measurementson the regenerators included inthe line system concernedb measure the BER on a whole line systemor in line sections. The operatorALARM STATE CHANGE REPORT1991-APR-23 12:15TRANSMISSION EQUIPMENT ALARMSTIME OFEVENTALARMSTATEALARMCLASSALARMPOINTEQPIDENTITYFig. 7Example of an alarm printoutAPR-23 12:12APR-23 12:13APR-23 12:13ENDACTACTDEACTA1A2A1LOSPFL6PFLTUMBA,LT140,15EDBG,LT140,4SNDBG,MUX8,23

61ACTIVE ALARMS1991-APR-23TRANSMISSION EQUIPMENT ALARMSTIME OFACTIVATIONALARMCLASSALARMPOINTEQPATLIDENTITYFig. 8Example of a printout showing active alarmsAPR-15 18:35APR-23 12:13APR-23 12:13A3A1A2AISLSRPFL6VISBY, MUX34.11STHLM,LT140,15EDBG, LT140.4Fig. 9Fault location procedure for an optical fibre linesystem, 140Mbit/sa A fault occurs in one of the regenerators intransmission direction A-Bb LT in station B detects the loss of the signal andactivates an alarm. This alarm is detected andreported and then starts fault location in the MMDc On the basis of the alarm information and thecontents of the network database, the MMD decidesto measure the BER for all regenerators in directionA-B. The MMD fetches FDU and regeneratoraddresses from the network databased The MMD orders BER measurements for therelevant FDUse BER is measured simultaneously in all FDUsconcernedf The MMD collects the measurement value fromeach regenerator, calculates the relative BER foreach regenerator section and compares it with thethreshold valueg The BER values for the regenerators in FDUs nos.100 and 101 do not exceed the threshold, but thevalues for regenerators nos. 102, 103 and 104 doh The MMD concludes that the fault is in regeneratorno. 102 and presents the result on the VDUs andprinters that have been defined as recipients of thistype of reportLT Line TerminalRE Regenerator (two-way)h> Regenerator (one-way)FDU Fault Detector Unit, built into LT or RE100 FDU address1,2 Regenerator addressspecifies when the measurements areto start and how many times they are tobe repeatedc indicate the faulty cable section in thecase of a cable failure.The process that indicates a faulty regenerator(a) can be initiated in two differentways. ZAN 202 can initiate the process autonomouslyas soon as an alarm from a linesystem is detected. The fault location procedureinvolves the measuring of bit errorratio in the relevant regenerators and comparingthe results with a threshold value.The regenerator whose BER exceeds thethreshold value is indicated as faulty. Faultlocation may also be initiated by operatorcommand. The operator then has thechoice to run the measurement processonce or let it be repeated continuously untilthe system has pinpointed a fault. The lattermethod is suitable if the fault is intermittent.An example is shown in Fig. 9: the faultlocation process for a line system consistingof two line terminals and a number ofregenerators.Diagnosis - b above - can only be initiatedby the operator, who orders one or moremeasurements. Any line system deteriorationis detected, and the measurement re-suits can be used in trend analyses. Theresult of the diagnosis is stored in theZAN 202 buffer store. The contents of thebuffer are displayed and/or printed out byoperator command.If there is a cable break, all line systems inthe cable are usually affected. ZAN 202then detects all alarms that are generatedand reports them to the operator. Instead ofthe ordinary fault location procedure describedabove, the operator may order a"cable test" which -through a simpler diagnosisprocess - locates the affected cablesection.Remote controlThe MMD can remote-control equipmentwith the aid of a unit (Remote Control unit,RCU) equipped with 16 individually controllableoutputs. Two activation methods areavailable:- activation/deactivation without time limits- scheduled activation/deactivation.Performance monitoringPerformance Monitoring involves continuouscollection of data concerning thequality of the transmission network. Thecollected data is used to-determine the quality of the services offeredby the network-decide when to initiate alarms indicatingthat the quality fails to meet requirements-analyse trends and prepare predictions,which make it possible to clear faults be-Station AStation BL_D4 interface; *LT2 12

Fig. 10VDU presentation of quality data (performancemonitoring data)fore the traffic over the transmission linksis affected.ZAN202 can collect quality data continuouslyfrom the supervised equipment,whether supplied by Ericsson or other vendors.Ericsson equipment has integratedmodules for the interworking with ZAN 202.As regards equipment from other vendors,ZAN 202 has modules that measure theCRC (Cyclic Redundancy Code) and/orFAS (Frame Alignment Signal) at the G.703interfaces.ZAN 202 measures the quality parametersspecified by CCITT in RecommendationG.821.- Errored seconds (ES). An ES is one secondduring which one or more bit errorsare detected-Severely errored seconds (SES). AnSES is one second during which BER isgreater than 1 x 10' 3 .-Degraded minutes (DM). A DM is oneminute during which BER is greater than1 x 10 6 , excluding unavailable time measuredas UAS- Unavailable seconds (UAS). A UAS is 10consecutive seconds during which BERis greater than 1 x 10 3 .At the initial level, the above-mentionedquality data is collected by the PUs. Thedata is then fetched by the MMD at certainintervals - the accumulation intervals.These are defined by the operator and maybe between 15 minutes and four hours.MMD-adds all measurement values that havebeen collected during the measurementperiod set by the operator. For example, ifthe accumulation interval is 15 minutesand the measurement period one hour,the MMD will add the measurement valuesfrom four intervals and give "onehour"values- compares the measurement values withpreset threshold values stored in theMMD. An alarm is generated if the thresholdvalue for any G.821 parameter is exceeded.Two threshold values and two measurementperiods may be defined for each qualityparameter. One threshold value marksthe boundary between "good" and "deteriorated"quality and the other between"deteriorated" and "unacceptable" quality.Completed measurement results are presentedon a VDU or printer. Fig. 10 showsan example of a quality parameter display.Man-machine interfaceVisual display units of type VT100 are usedfor man-machine communication. Upto sixVDUs may be connected to an MMD, eitherdirectly via V24/V28 interfaces or via standardmodems. A printer may also be connected.Alarms and other information maybe presented on one or several of the I/Odevices. ZAN 202 permits three differentuser categories. A unique password can bedefined for each category.REQUEST PM DATAEQP IDENTITYPRESENTATIONPM TEMPLATEACCUMULATIONSTART TIMEAPR-10 08:00APR-10 09:00APR-10 10:00APR-10 11:00APR-10 12:00APR-10 13:00APR-10 14:00PM HISTORY DATAINTERVALLENGTH00 01:0000 01:0000 01:0000 01:0000 01:0000 01:0000 01:00APR-10 00:00 00 14:00APR-09 00:00 01 00:00EDBG,LT140,4PERCENTAGE VALUES6DM1.6600003.333.330.00360.0013PM-PARAMETERSES SES0.056 00.028 00.028 00 00.028 04.326 0.4443.753 0.5550.01240.00280.00120.00031991-APR-10 15:11UAS000000.1130.089BER1E-082E-093E-09

63ZAN 202-ver2 Internal Alarm Printer ON SYS Report: OVERF1990-FEB-09 EQP Alarm: PM Alarm: Bl Mon OFF FL Result: 27%10:28 A1 A2 A3MENU MODE TOP: ALARM-SURV: REQ-ACTIVEWork windowFig. 11The display is divided into a status window and awork windowlogue with the operator in the menu modeor for presentation of alarms etc. in thereport mode. Fig. 11 shows the variousfields of the status window and the informationthey contain.HardwareAlarm collectionTwo types of alarm collection unit are used.In small stations with limited requirementsan ACU (Alarm Collection Unit) is used,with 7x4 = 28 alarm inputs per board.Large stations need an ACM (Alarm CollectionMagazine), which can be extendedto up to 16 modules, each with 7x8 = 56alarm inputs.Fault location and qualitymeasurementThe hardware for fault location and qualitymeasurements is integrated with the equipmentit supervises. These units are calledFDU (Fault Detector Unit), SU (SupervisionUnit) and CU (Control Unit). They come indifferent versions for different types oftransmission equipment.Remote controlRemote control by means of relay contactclosure requires an RCU (Remote ControlUnit), which has 16 individually controllablerelay contacts.References:Network adaptation1 Silvergran, U. and Woldegiorgis, K.: Fault The communication network between theLocation system ZAN201. Ericsson Review61 (1984):4, pp. 162-169.MMD and PUs may be extensive, dependingon the geographical configuration of the2 Eneborg, M. and Johansen, B.: TransmissionMaintenance System ZAN 101.Ericsson Review 61 (1984):1, pp. 18-25.3 Tarle, H.: FMAS An Operations SupportSystem for Transport Networks. EricssonReview 67(1990):4, pp. 163-182.4 CCITT Recommendation G.821.5 CCITT Recommendation M.30.supervised transmission network. It mayalso use communication channels in differentmedia. Modem Repeater Magazines,MRM, may be used to ensure flexibility andoperational reliability throughout the network.A Line Adapter, LA, is required whenthe service channel in radio relay linkequipment is to be used. An Input/OutputConverter, IOC, is necessary when freetime slots in the transmission systems orleased channels are to be utilised.Upgrading ZAN 201 to ZAN 202Existing ZAN 201 installations can be upgradedto ZAN 202 standard, which meansthat new functions are added. Upgrading isaccomplished through the replacement ofthe Fault Location Magazine, FLM, inZAN 201 by the MMD. In addition, the softwarein the line terminal FDUs is replacedby software that permits quality measurements.The programs for both ZAN 201 andZAN 202 are stored in PROMs.System capacityMany factors influence the capacity of aZAN 202 system, for example the networktopology and the amount of equipment beingsupervised as regardss alarms andquality. Generally speaking, 800 equipments- 200 of which are line systems -can be given operational support. Theequipments may be of 40 different typesand placed in 30 different stations.

ERICSSON^ISSN 0014-0171 Telefonaktiebolaget LM Ericsson 91419 Ljungforetagen, Orebro 1991