Switching Networks AGH Eng, telekomunikacja, 0, httpstudent.agh.edu.pl~piex, semestr 5, Systemy Komutacji, ...
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//-->Switching NetworksblankStanisław StochSwitching Systems1General (theoretical) model of the exchangeLine UnitSwitching Network ServingUnitExtended (practical) model of the exchangeLine UnitConcentratorSwitching NetworkServingUnitLULUSUSNSUSUConnectingPaths(Sieć DrógRozmównych)to otherexchangesTrunkUnitLULUTUTUCU(SN)insideSUSNSUSUto otherexchangesTrunkUnitTUTUCUControl UnitCUCUControl UnitCUCUStanisław StochSwitching Systems3Stanisław StochSwitching Systems4Number of terminals involved in the connectionNumber of terminals involved in the connectionIn digital telephony a conference is task of a “conferencebridge” and NOT – of the SN. From the SN point of view,conference of N subscribers is set of N single connectionsbetween subscribers and the “conference bridge”.– single connection– multiconnection(=conference)In digital telephony “multicast” is to be found onlyby delivering of signalling from one tone generatorto multiple subscribers (or tone receivers).Stanisław StochSwitching Systems5Stanisław StochSwitching Systems61One-sided vs. two-sided unitsPossible misunderstandinglocal connectionLineTrunkto otheroffices– Two-sided = rectangular(is able to connect onlyinput with output)transit connection– One-sided = triangular(homogeneous terminals,not divided into some groups)Stanisław StochSwitching Systems7outgoing or incomingconnectionSymbol of triangle is used for one-sided units in theoretical documents only.In the documentation of switching systems all units are drawn as rectangles.The real “triangular” nature of one-sided unit is to deduce from text description.Stanisław StochSwitching Systems8The same switching unit drawn as a triangleLineNumber of inputs to number of outputs ratio– traffic compression2:1 or greater, e.g. 8:1local connections( Line-Line)– traffic expansion1:2 or lesser, e.g. 1:8outgoing and incomingconnections ( Line-Trunk)transit connections ( Trunk-Trunk)to otheroffices– traffic distributionbetween 2:1 and 1:2TrunkStanisław StochSwitching Systems9sub.Asub.BStanisław StochSwitching Systems10Transmission directionalityexchangeexchangeexchangepustytelephone circuitmade onbidirectional pathtelephone circuit (transmissionally bidirectional)made ontwo unidirectional pathshybrid(rozgałęźnik)trunk exchange(centralamiędzymiastowa)Switching Systemshybrid(rozgałęźnik)Stanisław Stoch122Digital “elementary” switchDigital two-sided (rectangular) switch• transmisionally bidirectional –telephonyservice is bidirectional• transmisionallyunidirectional–because of digital technology• two-sided (rectangular) –partition into inputs and outputsis the result of unidirectional transmissionStanisław StochSwitching Systems13switchingmemoryStanisław StochSwitching Systems14Digital one-sided (triangular) switchDigital one-sided (triangular) switch“Looping” of certain circuitis practically used in switching equipmentto check partly set connection path.• transmisionally bidirectional –telephonyservice is bidirectional412341234321123412344321switchingmemoryswitchingmemoryStanisław StochSwitching Systems15Stanisław StochSwitching Systems16Switching directionalitySwitching directionalityseizure is possibleby control unit Y onlycontrolunitYexchangeexchangeexchangesub.Asub.Bunidirectional circuitsBecause every telephone circuitmust be transmissionally bidirectional,designation of directionality oftelephonecircuitrefers always to switching directionality.Switching directionality of a circuit is a matter ofcontrol unitsabilitiesandsignalingbetween them.Stanisław StochSwitching Systems17controlunitXseizure is possibleby control unit X onlybidirectional circuitscontrolunitXsignaling(avoids danger ofdouble seizure)Switching SystemscontrolunitYStanisław Stoch183Structures of stepping and crossbar exchangesStructures of digital exchanges5ESSFSGSto other officesto other officesLFGSEWSDto other officesto other officesIn the past almost all circuits (excluding subscriber lines) were unidirectional(switching unidirectionality), so practically all units were two-sided (rectangular).Stanisław StochSwitching Systems19Today almost all telephone circuits are bidirectional (switching and transmissiondirectionality) – so typical are one-sided (triangular) units.Stanisław StochSwitching Systems20Explanation of the difference5ESSFinal remarksPossible reasons to differentiate terminals,what implies switching unit to be bidirectional(rectangular):– unidirectionaltransmissionto other officesEWSD– switching unidirectionalcircuits–positionin theswitching networkto other officesStanisław StochSwitching Systems21Stanisław StochSwitching Systems22Chicken diagram (symbolikaszwedzka)Chicken diagram (cont.)25 circuits25 Out1 circuit25 circuits 25 circuits1 circuit10 circuits10 In12525110251Stanisław Stoch25Switching Systems2512310Stanisław StochSwitching Systems25244Joinig of inputs1025502525105010 In5025Joining of outputs10201010 In202520 In10 In252510Stanisław StochSwitching Systems25252510Stanisław Stoch10Switching Systems2526Joinig of inputs and outputs1025251025blank255010 In20 In10 In10Stanisław Stoch10Switching Systems252527Single-stage network (example no. 1)N2OutSingle-stage one-sided networkN1N2N1InNN• To make one connection – only one crosspoint(punkt komutacyjny) should be closed• All outputs are fully available• Number of crosspoints is a reasonableapproximate indication of the network cost:L1= N1• N2(for N1= N2:L1= N2)Stanisław StochSwitching Systems29• Number of crosspoints is a reasonableapproximate indication of the network cost :L = N • (N – 1) / 2(L ~ N2)For two-sided and one-sided networks:• Preserving full availability–• we seek an opportunity to reduce the cost L.Stanisław StochSwitching Systems305
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