Digital Data Communications LEVEL ONE FCS-4500 Uživatelský manuál Strana 1

Jamadagni H S DC/V1/2004 1Digital Communication SystemsH. S. Jamadagni, CEDT, IISc, Bangalore

AnaloginputA/DDigitallyencodedsamplesD/AAnalog OutputAnalogAnalogPAM samplesSampleclockPulse Code Modulation (PCM)Low passfilterLow passfilterJamadagn

Jamadagni H S DC/V1/2004 9ADSL• Asymmetric data streamszMost applications fit this modelz video on demandz home shoppingz Internet accessz remote LAN

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Jamadagni H S DC/V1/2004 11ADSL will play a crucial role over the next ten or more years for delivering information in video and multimedia formats.

Jamadagni H S DC/V1/2004 12ADSL basics (contd 2)Three information channels a high speed downstream channelSpeed ranges from 1.5 to 6.1 Mbpsa medium sp

Jamadagni H S DC/V1/2004 13ADSL in operationBroadbandNetworkNarrowbandNetwork(PSTN)DSLAMPOTS splitterPOTS splitterExisting copper linedown1.5 to 6 Mbp

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Jamadagni H S DC/V1/2004 15ADSL reachData Rate Distance Wire Size Distance1.5 or 2 Mbps 18,000 ft 0.5 mm 5.5 km 1.5 or 2 Mbps 15,000 ft 0.4 mm 4.6

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Jamadagni H S DC/V1/2004 18ADSL (spectrum)UpstreamData spectrumDownstreamData spectrumPOTS20Khz 1.1 Mhz4KhzFrequency SpectrumT1/T3 circuits, Bridge Ta

010011011010001001000101101000Quantisation of analog samplesQuantisation of speech signal samplesQuantisation errors011010001000100101110111Jamadagni

Jamadagni H S DC/V1/2004 19Modulation Techniques (ADSL)• Discrete Multitone modulation (DMT)zmulticarrier sub-channels (256 downstream, 32 upstream)

Jamadagni H S DC/V1/2004 20Modulation Techniques (ADSL)• Carrierless Amplitude/Phase modulation (CAP)zproprietary, mature technologyzsingle carrier sy

Jamadagni H S DC/V1/2004 21Competing Technologies• Cable Modemsz 18,000 ft limit (head-end)z Most cable operators need to upgrade their networks to su

Jamadagni H S DC/V1/2004 22Competing Technologies• Digital Satellite transmissionz Still need upstream data provider (usually handled through modem or

Protocol discriminator0000LengthCall reference valueF0Message typeOther infromationelements if requiredQ. 931 Message format1Info. elementidentifierCo

Bearer capability infromation element identifier1 00000100 Bearer capability info.element identifier2 Length of bearer capability contents3 1 XXXXXXX

Procedure for a circuit-switched callData Flowoff hkSet upSet upRingingRing backCall proceedingAlertingRB stopconnectConnectS1 ST1 ET1 ET2 ST2 S2Jamad

Terminal CallProcessingBasic ServiceProtocol(Q.931)SupplementaryServicesProtocol(Facility)Q.931 MessagesLAPD1.430/1.431Exchange Call ProcessingBasic S

Layer 3 FunctionsJamadagni H S DC/V1/2004 2RoutingNetwork connection establishmentConnection releaseMultiplexingCongestion controlAddressing

Layer 2 FunctionsJamadagni H S DC/V1/2004 3Traffic over D channel (control Info and data over D) Q 921Q921 servicesÊConvey user Info between layers en

Quantisation error in PCMQuantized outputsignalInput signalouInput amplitudeJamadagni H S DC/V1/2004 12Decoder tputQuantisation error as a function of

Function of other layersJamadagni H S DC/V1/2004 4layer 4 : error detection / recoveryflow controllayer 4 connection, release, muxingLayer 5 : session

Jamadagni H S DC/V1/2004 51. Protocol reference model I320zCircuit - switched connection under common channel signallingzPacket - switched comm over B

Basic Call ControlJamadagni H S DC/V1/2004 6zinteract with layer 2 (LAPD) to transmit / receive messageszgenerate and interpret layer 3 messageszadmin

Layer 1 FunctionsJamadagni H S DC/V1/2004 7ÊEncoding of digital data for transmission across the interfaceÊFull-duplex transmission of B channel dataÊ

Jamadagni H S DC/V1/2004 8Circuit - mode connection control functions needed for circuit-switched B channel callsPacked - mode connection control fun

Jamadagni H S DC/V1/2004 9Signaling exchanged between user - network, network - network.Protocol discriminator (0001000) for Q931 call referenceMessag

Q931 messages for circuit mode connectionsJamadagni H S DC/V1/2004 10Call Establishment MessagesMessage Significance Direction FunctionALERTING global

Jamadagni H S DC/V1/2004 11Message Significance Direction FunctionRESUME local u n Requests resumption of previously suspended callRESUME local n u In

Jamadagni H S DC/V1/2004 12Message Significance Direction FunctionDISCONNECT global both Sent by user to request connectionclearing; sent by network t

Jamadagni H S DC/V1/2004 13FLAG ADDRESS CONTROL INFORMATION FCS FLAG 8 bits 16 8 or 16 Variable

PCM system - Typical parameters4 KHz Speech signal8 KHz Sampling8 bits / sample digitisingper speech channel 8 x 8 bits = 64 kbpsT1 carrier: 24 channe

Jamadagni H S DC/V1/2004 140N(S)P/FN(R)1 0 SS0 0 0 0 P/F N(R)11MM P/FMMMInformationtransferSupervisoryUnnumberedN(S) = Transmitter send sequence num

Jamadagni H S DC/V1/2004 15Name Control Field C/R DescriptionInformation formatI (Information) 0-N(S)--P-N(R)-- C Exchange user dataSupervisory Format

Unnumbered formatJamadagni H S DC/V1/2004 16SABME (Set Asyn 1111P110 C Request logical connectionchronous BalancedMode)DM (Disconnected 1111F000 R Una

Jamadagni H S DC/V1/2004 17(a) SAPI AssignmentsSAPI Value Related Protocol or Management Entity0 Call-control procedures16 packet communication confor

Jamadagni H S DC/V1/2004 18******** ** * * *SAPI = 0 SAPI = 16SAP identifierDatalinklayerSI: Signalling informationPD: Packet dataData linklayer

Jamadagni H S DC/V1/2004 19NRZ-LBipolar-AMIPseudo-ternary0 1 0 0 1 1 0 0

Jamadagni H S DC/V1/2004 20Contact Assignments for Plugs and Jacks of ISDN ContactNumber TE NTa Power Source 3 Power Sink 3b Power Source 3 Power Sink

Jamadagni H S DC/V1/2004 21Fixed by local administrationz4 wire interface no echo cancellation procedures, simple line terminationz2 wire interfacePin

Jamadagni H S DC/V1/2004 22+RX DataDecisionFeedbackEqualisationLineEncodingEchoCancellorHybridDSLTX DataΣADU interface circuit

Jamadagni H S DC/V1/2004 23ISWSWSWSWSWSWSWSW123456782B + D2B + D2B + D2B + D2B + D2B + D2B + D2B + D2B + D2B + D2B + D2B + D2B + D2B + D2B + D2B + D2B

Idle channel noise minimisationJamadagni H S DC/V1/2004 14Mid-riser quantizerMid-tread quantizerIdle channel noise: Caused by uncertainty in coding a

Signal to quantizing noise of uniform PCMnumber of bits / sample13119A/Amax (dB)SNR (dB)80-10-20-30-40204060Jamadagni H S DC/V1/2004 15

Non-linear AD conversionJamadagni H S DC/V1/2004 16Uniform QuantisationInput sample valuesCompressed sample values

Compression law - µ law00.20.40.60.810 0.2 0.4 0.6 0.8 1Normalised inputNormalised outputJamadagni H S DC/V1/2004 17

Compression law - A law00.20.40.60.8100.20.40.60.81Normalised inputNormalised outputJamadagni H S DC/V1/2004 18

Non linear AD conversion laws used in PCM for speechFz(x)=sgn(x)ln(1+z.|x|)ln(1+z)FA(x)=sgn(x)A|x|1+lnAµ lawA lawJamadagni H S DC/V1/2004 19

Topics in Digital CommunicationszDigital communication system advantages and disadvantageszDigital communication system classificationzDigitization of

Low bit rate coding: DPCM, Differential PCM A/DD/A+-ΣSpeech signalBand limitingfilterDifferentiatorSamplerquantizerencoderPreviousinputestimateAccumu

ΣΣ+-++Σ++EncoderDecoderADC DAC S & HS & H DACDPCM implementationLPF LPFJamadagni H S DC/V1/2004 21

Delta modulationJamadagni H S DC/V1/2004 22Σ+-Pulse generator-+10"1"InputOutputDecoderIntegratorIntegratorLPF LPF

Slope overload distortion in Delta modulationSlope over loadGranular noiseJamadagni H S DC/V1/2004 23

Low Data Rate ModulationzCVSD (Continuous Variable Slope Delta Modulation)S-++-10C2PG10C1PGStepsizecontrolAll 1sAll 0sEncoderFFSample clockPGPGDecoder

Conceptual view of ISDNJamadagni H S DC/V1/2004 1PBXLocal area networkPacket switched networkCircuit switched networkOther networksData basesOther s

Block diagram of ISDN functionsCommonphysicalinterfaceISDNcentralofficeDigital circuit -switched backbonePacket-switchedbackboneNetwork-basedprocessin

ISDN principlesÊISDN is based on concepts developed for telephony. Therefore, evolutionary changesÊTransition from the present network to ISDN may req

Principles of ISDN (Cont.)ÊSupports a wide range of voice and non-voice applicationsÊSwitched and non-switched connections Circuit switching and pack

ISDN evolutionzDigital exchanges commissioned in late 60's and 70'sIntegrated digital transmission and switching established (IDN)zIntegrati

Digital Communication advantageszReliable communication; less sensitivity to changes in environmental conditions (temperature, etc.)zEasy multiplexing

ISDN services: Definition of attributeszAll services on the ISDN network are characterised by "attributes" defined in ITU 1.130 standardszAt

ISDN services: AttributesAttribute Name ValuesInfo. transfer mode Circuit, packetInfo. transfer rate Bit rateInfo. transfer capability Speech,

ISDN service classificationServices defined by attributesÊBearer servicesÊTeleservicesÊSecondary servicesBearer services provide capability to transfe

ISDN teleservicesÊLow layer attributesÊHigh layer attributesÊType of user informationÊLayer 4 protocolsÊLayer 5 protocolsÊLayer 6 protocolsÊLayer 7 pr

Customer access to services supported by ISDNTEI NT2 NT1TE2 TA54RS32S1TJamadagni H S DC/V1/2004 10

Functional groupingzTE: Terminal equipmentTE1: S interface terminalTE2: R interface terminalzTA: Terminal adapteradapts TE2 to S interfacezNT: Network

Network functional principleszServices to be internationally compatiblezUNI standardised so that TE is portablezStandardise network capabilityHigh Lay

Access channel and rateChannel name Bit rateD 16 Kbps64 KbpsB 64 KbpsH0 384 KbpsH1H11 1536 KbpsH12 1920 KbpsJamadagni H S DC/V1/2004 13

Bearer servicesz64 Kbps unrestricted, 8 KHz structuredz64 Kbps 8 KHz structured, speechz64 Kbps 8 KHz structured, 3.1 KHz audioz384 Kbps unrestrictedz

ISDN subscriber premises connectionsTENTTRTR(a) Point-to-pointTETETENTTRTR<100-200m(b) Short passive bus<1 kmTR = Terminating ResistorJamadagni

zIncreased bandwidth64 KB for a 4 KHz channel, without compression (However, less with compression)zNeed for precision timing Bit, character, frame

Extended passive busTETENTTRTR<500m< 25-50mJamadagni H S DC/V1/2004 16

NT1 starTRTRTETRTRTENTI<1 kmJamadagni H S DC/V1/2004 17

User - Network Interface: Layer 1 specificationsB channel: 64 Kbps, two channelsBit timing and rate: 192 KbpsOctet timingFrame alignmentD channel:

Layer 1 functionsÊEncoding of digital data for transmission across the interface.ÊFull-duplex transmission of B channel dataÊFull-duplex transmission

ISDN Layer 2Traffic over D channel (control Info and data over D) Q 921Q921 servicesÊConvey user Info between layers entities using D channelÊSupport

Function of other layerslayer 3 : routingnetwork connection establishmentreleasemultiplexingcongestion controladdressinglayer 4 : error detection / re

Modelling of basic and supplementary servicesTerminal CallProcessingBasic ServiceProtocol(Q.931)SupplementaryServicesProtocol(Facility)Q.931 MessagesL

Basic Call Controlzinteract with layer 2 (LAPD) to transmit / receive messageszgenerate & interpret layer 3 messageszadmin of times and logical en

Protocol reference model I 3201. Protocol reference model I320zCircuit - switched connection under common channel signallingzPacket - switched comm ov

Frame format in ISDN layer 2FLAG ADDRESS CONTROL INFORMATION FCS FLAG 8 bits 16 8 or 16 Variabl

Types of Digital Communication SystemsSignal Type Transmission ExampleAnalog Analog Classical telephonyAnalog Digital PCM TDM Digital Analog ModemsDig

LAPD format0 N(S) P/F N(R)1 0 SS0 0 0 0 P/F N(R)11MM P/FMMMInformationtransferSupervisoryUnnumberedN(S) = Transmitter send sequence numberN(R) = Tra

Name Control Field C/R DescriptionInformation formatI (Information) 0-N(S)--P-N(R)-- C Exchange user dataSupervisory FormatRR (Receive Ready) 10000000

Unnumbered formatSABME (Set Asyn 1111P110 C Request logical connectionchronous BalancedMode)DM (Disconnected 1111F000 R Unable to establish or mainMod

Q931 message typesCircuit - mode connection control functions needed for circuit-switched B channel callsPacked - mode connection control functions n

MessagesSignalling exchanged between user - network, network - network.Protocol discriminator (0001000) for Q931 call referencemessage typelength (1 f

SAPI and TEI assignmentsJamadagni H S DC/V1/2004 31(a) SAPI AssignmentsSAPI Value Related Protocol or Management Entity0 Call-control procedures16 pac

Q931 messages for circuit mode connectionsCall Establishment MessagesMessage Significance Direction FunctionALERTING global both Indicates that user

Call information phase messagesMessage Significance Direction FunctionRESUME local u n Requests resumption of previously suspended callRESUME local n

Message Significance Direction FunctionDISCONNECT global both Sent by user to request connectionclearing; sent by network to indicateconnection cleari

Digital Signal Encoding Format in ISDNNRZ-LBipolar-AMIPseudo-ternary0 1 0 0 1 1 0

Time AmplitudeDigitization of analogue signalsTime AmplitudezSignal samplingJamadagni H S DC/V1/2004 6

Physical connector in ISDNContact Assignments for Plugs and Jacks of ISDN ContactNumber TE NTa Power Source 3 Power Sink 3b Power Source 3 Power Sink

The U interfaceFixed by local administrationz4 wire interface no echo cancellation procedures, simple line terminationz2 wire interfacePing-Pong opera

U interface circuit+RX DataDecisionFeedbackEqualisationLineEncodingEchoCancellorHybridDSLTX DataΣADJamadagni H S DC/V1/2004 38

ANSI U interface frame and superframe structureISWSWSWSWSWSWSWSW123456782B + D2B + D2B + D2B + D2B + D2B + D2B + D2B + D2B + D2B + D2B + D2B + D2B + D

TEI and SAPI assignmentJamadagni H S DC/V1/2004 40******** ** * * *SAPI = 0 SAPI = 16SAP identifierDatalinklayerSI: Signalling informationPD: Pa

Asymetric Digital Subscriber LineJamadagni H S DC/V1/2004 1

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ADSL will play a crucial role over the next ten or more years for delivering information in video and multimedia formats. New broadband cabling will

ADSL basics (contd 2)Three information channels a high speed downstream channelSpeed ranges from 1.5 to 6.1 Mbpsa medium speed duplex channelSpeed ran

Nyquist Criterion, AliasingTime AmplitudeTime AmplitudeOriginal signalAliased signalNyquist sampling rate fs > 2. fbJamadagni H S DC/V1/2004 7

ADSL reachData Rate Distance Wire Size Distance1.5 or 2 Mbps 18,000 ft 0.5 mm 5.5 km 1.5 or 2 Mbps 15,000 ft 0.4 mm 4.6 km 6.1Mbps 12,000 ft 0.5

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Jamadagni H S DC/V1/2004 1POINT-TO-POINT BROADCASTÊONE SOURCE ONE SOURCEÊONE SINK MANY SINKSFOR INFORMATIO

Jamadagni H S DC/V1/2004 2zManual - through operator 1880 onwardszStep-by-Step Strowger ~1897zFirst "big" strowger exchange

Jamadagni H S DC/V1/2004 3SWITCHINGSYSTEMSNON-CIRCUITSWITCHESCIRCUITSWITCHESMainly for interactivecommunicationVoice, Video, etc.Mainly for non-intera

Jamadagni H S DC/V1/2004 4EPABXTrunks10 to 15% of sub linesPrimaryLocal Exchange1000's of linesSecondarySwitching system topology

Jamadagni H S DC/V1/2004 5Switching system objective: To interconnect twocircuits for information exchangeInformation: Voice, Data, FAX, Still Video,

Jamadagni H S DC/V1/2004 62. SIGNALLINGCHANNEL ASSOCIATED - COMMUNICATIONCHANNEL (ZW) USED FOR SIGNALLINGFEED TONESREMOVE TONESDTMF, PULSE DIALLINGFL

Jamadagni H S DC/V1/2004 7CALLINGSWITCHCALLEDOFF-HOOK (ORIGINATE) DIAL TONE DIAL DIGITS RING BACK TONECONVERSEO

Jamadagni H S DC/V1/2004 8SPACE DIVISIONzestablish connectionthrough' galvanic connectionszonce established, contactremains till disconnectionzde

Amplitude-B+BFrequencySpectrum of the properly sampled base bandSpectrum of the under sampled base bandSpectrum of baseband signalsJamadagni H S DC/V

Jamadagni H S DC/V1/2004 9ÊPath establishment - using extensive signallingÊInformation interchange - using error free communicationÊFacilities - offer

Jamadagni H S DC/V1/2004 10zCOMMON CONTROLzCONTROL through' COMPUTER HW + SWzBOTH TIME DIVISION & SPACE DIVISION POSSIBLESPACE DIVISION SWITC

Jamadagni H S DC/V1/2004 11ÊLow cost for small switches (say up to 64 subscribers)ÊLow distortion due to direct speech switchingÊIntroducing tones ver

Jamadagni H S DC/V1/2004 12N input linesN output linesA generic N by N switch

Jamadagni H S DC/V1/2004 13First stage Second stage Third stageThree-stage space-division switchSpace division switch

Jamadagni H S DC/V1/2004 14Lines Single-Stage Three stage128 7,680 16,384512 63,488 262,144 2,048 516, 096

Jamadagni H S DC/V1/2004 15SUBLINETERMINATESUBLINESWITCHMATRIXANALOGTRUNKTERMINATECONTROLSWITCH CONTROL SYSTEMTERMINALSCONSOLESSUBSPC Digital Switch B

Jamadagni H S DC/V1/2004 16YXO/PStreamChannelNo.* One Frame delayXTime1 2 3 4 5 1 2 3 4 5 TimeXYI/

Jamadagni H S DC/V1/2004 171 8 19 24 1 8 19 24 198PCM INPUT BUSINFORMATION MEMORYCONTROL MEMORYCONTROLPCM output bus)Implementation of a digital TSI

Jamadagni H S DC/V1/2004 18n inletsn outletsn I O PairsA Simple Folded Time-Division SwitchA Simple Time-Division SwitchTDM Bus switch

Speech signal digitisationLPFInput signalPulse trainOutput signalPulse amplitude modulationPAM samplesJamadagni H S DC/V1/2004 9

Jamadagni H S DC/V1/2004 19TML1TML25 38 520 14

Jamadagni H S DC/V1/2004 20...SPACETIMESPACE2 TML11 3 16 16 3 K TML2TMLnTMLOUTPUT13 16 TMLOUTPUT2TMLOUTPUTn16 3 Space-time-space s

Jamadagni H S DC/V1/2004 1Overview•Copper Access• Bandwidth Requirements• Distance vs. Rate• ADSL• Modulation Techniques• Competing Technologies

Jamadagni H S DC/V1/2004 2Copper Access Technologies // Voice• Voice Grade ModemszV.22 // V.32 // V.34z 1,200 to 28,800 bps (33,600 bps)z Full Duplexz

Jamadagni H S DC/V1/2004 3Copper Access Technologies // Voice (V-series)<300 600 1200 2400 4800 9600 14.4K 28.8K V.

Jamadagni H S DC/V1/2004 4Copper Access Technologies // DSL (ISDN)• Digital Subscriber LinezDSL (ISDN BRI)z 160 kbps (two 64 kbps (B) +

Jamadagni H S DC/V1/2004 5Copper Access Technologies // HDSL and SDSL• High Data Rate and Single Line (Symmetric)zHDSL and SDSLz 1.544 Mbps // 2.048 M

Jamadagni H S DC/V1/2004 6Copper Access Technologies // ADSL and RADSL• Asymmetric Digital Subscriber Line (Rate Adaptive)zADSL // RADSLz 1.5 Mbps to

Jamadagni H S DC/V1/2004 7Bandwidth RequirementsApplicationTypeFileSizeModem ISDN128kbpsDSL384kbpsDSL768kbpsDSL1.544Mbps DSL6.144MbpsE-mail30k 8.3 s 1

Jamadagni H S DC/V1/2004 8Distance vs. Rate (downstream)•VDSL (24g wire)z 12.96 Mbps @ 4,500 ftz 25.82 Mbps @ 3,000 ftz 51.84 Mbps @ 1,000 ft• ADSL (2