现代通信网络-ppt课件

现代通信网络ModernTelecommunicationNetworkLecture3(CS)电路交换与软交换北邮软件学院：陈候武[e-mail]电话：CommunicationNetworks【通信网络的分类】CommunicationNetworkSwitchedCommunicationNetworkVirtualCircuitNetwork:MPLSBroadcastCommunicationNetwork广播，电视，卫星PacketSwitch(PS)-分组交换DatagramNetwork:Internet:IP因特网Circuit-Switched(CS)-电话通信业务网(ServiceNetwork)：分类：SwitchedNetwork：【通信交换网络】NodeSwitching（节点交换）•Anode(switch)inacircuitswitchingnetworkincominglinksoutgoinglinksNodeNodes【交换节点】•Nodesmayconnecttoothernodesonly,ortostationsandothernodes•Nodetonodelinksusuallymultiplexed【复用】•NetworkisusuallypartiallyconnectedSomeredundantconnections【冗余连接】aredesirableforreliability•TwodifferentswitchingtechnologiesCircuitswitching【电路交换】Packetswitching【分组交换】CS:CircuitSwitch电路交换【Overview】CS:CircuitSwitching【电路交换】•Dedicatedcommunicationpathbetweentwostations【专用/独享的通信通道】•Threephases【呼叫建立：3个阶段】EstablishTransferDisconnect•Musthaveswitchingcapacityandchannelcapacitytoestablishconnection•Musthaveintelligencetoworkoutrouting必须具有智能以对呼叫进行选路CircuitSwitching-Applications•InefficientChannelcapacitydedicatedfordurationofconnectionIfnodata,capacitywasted•Setup(connection)takestime•Onceconnected,transferistransparent•Developedforvoicetraffic(phone:电话网)CS：PSTN–网络结构PSTN–PublicSwitchedTelephoneNetworkUsesdigitaltrunksbetweenCentralOfficeswitches(CO)UsesanaloglinefromphonestoCODigitalTrunks数字中继AnaloglineCentralOfficeCentralOfficePSTN:PublicCircuitSwitchedNetworkCS:Components【网络组成】•Subscriber【用户：电话】Devicesattachedtonetwork•Subscriberline【用户连线】LocalLoop【本地环路】Subscriberloop【用户环路】ConnectiontonetworkFewkmuptofewtensofkm•Exchange/Switch【交换机】SwitchingcentersEndoffice-supportssubscribers•Trunks【中继线】BranchesbetweenexchangesMultiplexed【复用】LegacyDigitalCircuitSwitchCentralizedIntelligenceProprietaryCodeProprietaryservicedeploymentVeryexpensiveTrunkCardTrunkCardTrunkCardLineCardLineCardLineCardSwitchControllerNextSwitchNextSwitchNextSwitchSS7NetworkCircuitSwitchElements【电路交换组成】CircuitSwitchingConcepts•DigitalSwitch【数字交换】Providetransparentsignalpathbetweendevices•NetworkInterface【网络接口】•ControlUnit【控制单元】Establishconnections•Generallyondemand•Handleandacknowledgerequests•Determineifdestinationisfree•constructpathMaintainconnectionDisconnectNodeswitchingSystem:CS：SPC:电话数字程控交换机–模块CS:CirtuitSwitch【SwitchFabric：交换矩阵】SwitchFabric:MxNSwitchFabric:Mathgraphpresentation•Ainputmaysetuponeconnection(1,3,6,7),multipleconnections(4),ornoconnection(2,5,8).SwitchFabric:数学模型•Inputset:T={0,1,2,…,M-1}•Outputset:R={0,1,2,…,N-1}•Definition:•t∈Tandr∈Rt，Rt∈R，then:c=|t,Rt|isaconnection.•tisstartpointoftheconnection,r∈Rtistheendpoint.•ifr∈Rt,Rtcontainsonlyoneitem,thisconnectionispointtopoint.•ifr∈Rt,Rtcontainsmorethanoneitem,thisconnectionispointtomulti-point.•Multicast:Rt≠R;Broadcast:Rt=R•connectionsetinswitchfabric:C=|c0,c1,c2,…|SwitchFabric:连接函数•连接函数:inputlink:x(0=x=M-1)•Outputlinkf(x)(0=f(x)=N-1).•例如：连接函数:δ(x2,x1,x0)=x1,x0,x2•δ(000)=000,δ(001)=010,δ(010)=100,δ(111)=111SwitchingFabric:TimeDivision•Time-slotswitchingisadevice,whichbuffersmincomingtime-slots,arrangesnewtransmitorderandtransmitsntime-slots•UsedinPacketswitchandATMaswellasdigitaltelephoneswitchSwitchingFabric:SpaceDivisionTime/SpaceDivisionMultiplexingTIMESWITCHTIMESWITCHTIMESWITCHTIMESWITCHTIMESWITCHTIMESWITCHSPACESWITCHCS：BlockingorNon-blocking•Blocking【阻塞】AnetworkisunabletoconnectstationsbecauseallpathsareinuseAblockingnetworkallowsthis【网络允许Blocking】Usedonvoicesystems•Shortdurationcalls•Non-blocking【无阻塞】Permitsallstationstoconnect(inpairs)atonceUsedforsomedataconnectionsSwitchingFabric:Blocking•如果：I0正在连续到O0,•问：I1可以连接到O0orO1???•结果：内部阻塞解决方案：MultistageSwitchReducednumberofcrosspointsMorethanonepaththroughnetworkIncreasedreliabilityMorecomplexcontrolMaybeblocking解决方案：两级交换矩阵解决方案：ThreeStageSwitchxxxxCS：TST交换矩阵-实例：•TST-TimeswitchandSpaceswitch•(1)T接线器:Auserinfo.Occupyatimeslot8bitscode.（3）TST接线器－512x512TimeSlotsCS:电路交换【PSTN:TrunkMultiplexing】CO1–CO2:TruckMultiplexingMux….….….….….11111222….64kb/svoicechannelt4t3t2t12Mb/soutputsignal同步时分复用：SynchronousTDME1:2Mb/sframestructureAllTimeslotscontain8bitwords(PCM,Data,Subrate,nx64kb/s)NetworkSignaling-CASorCCS0123…14151617…30310…1frame-256bits-125msFrameAlignmentWord3.9usNetworkSignalingChannels1to15Channels16to30MUXMUXMUXMUXMUX12341234E1E1E1E1E2E2E2E2E52.0488.44834.368139.264561.480MbpsMbpsMbpsMbpsMbpsCH2CH1CH32E31E32E33E34E41E42E43E44ITU-TE1DIGITALMULTIPLEXINGHIERARCHYE1E2E3E4E5ANSI：T1-T-carriersystem1.544MEachframecarriesonesample(8bits)foreach24channels,plusoneframingbit=193bits193*8000(samples/sec)=1.544Mbit/sec=T-1Channel1Channel2Channel3Channel24…Channel1Channel2Channel3Channel24…FramingBit1D4FrameTDMANSI:T1/DS1FrameStructure-1.544Mbps•Every8thbitusedforsignalinginefficient01221226…2023…1frame-193bits-24channelsBit8-reservedforsignalingFramingbit34501Bits1-7PayloadANSI:DIGITALMULTIPLEXINGHIERARCHYT1T2T3T4T5MUXMUXMUXMUXMUX12T313T324T335T346T357T36123412T1T1T1T1T2T2T2T2T2T2T2T4T4T5CH1CH2CH2424VF1.5446.31244.736274.176560.160MbpsMbpsMbpsMbpsMbpsStatistica