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1、PrinciplesofModernCommunicationsChapter1-introductionChapter1:IntroductionDr.LiHaoEmail:SchoolofInformationScienceandTechnologySouthwestJiaotongUniversity2012Spring1-2-现代通信原理Principles of Modern Communications-Li Hao,2012CourseInformationPrerequisiteSignals and SystemsRandom ProcessesTextbook and Re
2、ferences周迥磐等，通信原理（第3版），北京邮电大学出版社Leon W.Couch II,Digital and Analog Communication Systems,Sixth EditionSimulation ToolSystemView(required)Matlab(optional)1-3-现代通信原理Principles of Modern Communications-Li Hao,2012CourseInformation(Contd)GradingAttendance(5%)Exercise,homework,question answer(10%)Quiz an
3、d midterm examinations(15%)Final examination(70%)1-4-现代通信原理Principles of Modern Communications-Li Hao,2012CourseContentsChapter 1:IntroductionAppendix I:Introduction to SystemViewChapter 2:Analysis of deterministic signals Chapter 3:Random processAppendix II:ChannelChapter 4:Analog modulation system
4、sAppendix III:Information measure and channel capacityAppendix IV:Terms of Digital Communication SystemChapter 5:Baseband digital systemsChapter 6:Bandpass digital systemsChapter 7:Analog source coding(PCM)1-5-现代通信原理Principles of Modern Communications-Li Hao,2012Chapter1Introduction1.1 What is a com
5、munication system?1.2 Historical background1.3 Digital and analog sources and systems1.4 Deterministic and random waveforms1.5 Block diagram of a communication system1.6 Examples1-6-现代通信原理Principles of Modern Communications-Li Hao,20121.1Whatisacommunicationsystem?Two types of ECE(electrical and com
6、puter engineering)systemsProductionandtransmissionofelectricalenergywaveformsareusuallyknown,andoneisconcernedwithdesigningthesystemforminimum energy lossTransmissionorprocessingofinformationthewaveformpresentatthereceiver(user)isunknownuntilafteritisreceivedNoise limits our ability to communicateWh
7、atwillhappenifthereisnonoiseinthecommunicationsystem?1-7-现代通信原理Principles of Modern Communications-Li Hao,2012Whatisacommunicationsystem?Communicationsystemsaredesignedtotransmit information.Fourmainconcernsinvolvedindesigningacomm.systemSelectionoftheInformation-bearingwaveformBandwidthandpowerofth
8、ewaveformEffectofsystemnoiseonthereceivedinformationCostofthesystemTypesofcommunicationsystemsdigital/analogbaseband/bandpassWireline/wireless1-8-现代通信原理Principles of Modern Communications-Li Hao,20121.2HistoricalperspectiveTelegraphRadioTelephoneElectronicsTelevisionDigitalCommunicationsComputerNetw
9、orksSatelliteCommunicationsOpticalCommunications1-9-现代通信原理Principles of Modern Communications-Li Hao,2012TelegraphMorsesideawastostringawirebetweentwopoints,maybemilesapart.Akeyatoneendispressedanditclosestheelectricalcircuitwhichsendsapulseofelectricitythroughthewire.Whenthekeyisletgoveryfast,thepu
10、lseofelectricitysentthroughthewireisadot.Ifthekeyishelddown3timeslonger,thepulseisadash.Dashesanddotsmixedtogetherformdifferentlettersofthealphabetandwhensentfromapersonatoneendofthewiretoanotherpersonattheotherendofthewire,thesedashesanddotswouldspelloutwords.*-*-*-1-10-现代通信原理Principles of Modern C
11、ommunications-Li Hao,2012Radio1864,Maxwellpredictselectromagneticradiation1887,HerzverifiesMaxwellstheory1900,Marconitransmitsthefirsttransatlanticwirelesssignal1905,speechandmusicweretransmittedviaradio1920,thefirstscheduledradiobroadcasts1926,televisionwasdemonstrated1936,BBCbeganthefirsttelevisio
12、nbroadcasts1-11-现代通信原理Principles of Modern Communications-Li Hao,2012TelephoneWhatwerethefirstwordseverspokenonthetelephone?TheywerespokenbyAlexanderGrahamBell,inventorofthetelephone,whenhemadethefirstcallonMarch10,1876,tohisassistant,ThomasWatson:Mr.Watson-comehere-Iwanttoseeyou.“Bell on the teleph
13、one in New York(calling Chicago)in 1892 Bells first design sketch of the telephone Bellsfirsttelephonecallwassofamous,herepeatedthephrasein1915intheformalopeningofthecompletedtranscontinentaltelephonelinesconnectingAmericasEastandWestcoasts.PickingupthephoneinNewYork,Mr.Bellsaid,Mr.Watson,comehere,I
14、wantyou.ButthistimeWatsonrepliedthatitwouldtakehimaweek;hewasontheotherendofthelineinSanFrancisco.1-12-现代通信原理Principles of Modern Communications-Li Hao,20121.3DigitalandanalogsourcesandsystemsDigitalinformation sourceandanaloginformationsourceSourcegeneratemessagesdigitalsourcegenerateafinitesetofpo
15、ssiblemessagesAnalogsourcegeneratemessagesdefinedonacontinuumDigitalcommunicationsystemandanalogcommunicationsystemAdigitalsystemmayhaveananalogsource!e.g.digitalmobilecommunication(GSM)DigitalwaveformandanalogwaveformAdigitalsystemmayuseanalogwaveform!e.g.2FSKmodulationwaveform1-13-现代通信原理Principles
16、 of Modern Communications-Li Hao,2012AdvantagesofdigitalcommunicationRelativelyinexpensivedigitalcircuitsmaybeusedRelativelysmallsizePrivacyispreservedbyusingdataencryptionGreaterdynamicrangeispossibleDatafromvoice,video,anddatasourcesmaybemergedandtransmittedoveracommondigitaltransmissionsystemInlo
17、ng-distancetransmission,noisedoesnotaccumulatefromrepeatertorepeaterErrorsindetecteddatamaybesmall,evenwhenthereisalargeamountofnoiseonthereceivedsignalErrorsmayoftenbecorrectedbytheuseofcoding1-14-现代通信原理Principles of Modern Communications-Li Hao,2012DisadvantagesofdigitalcommunicationGenerally,more
18、bandwidthisrequiredSynchronizationisrequired1-15-现代通信原理Principles of Modern Communications-Li Hao,20121.4DeterministicandrandomwaveformsAdeterministic waveformcanbemodeledasacompletelyspecifiedfunctionoftimeArandom(stochastic)waveformcannotbecompletelyspecifiedasafunctionoftimeandmustbemodeledprobab
19、ilistically.Theinformation-bearingwaveformmustberandomtosomeextentNoiseisalsorandomwaveform1-16-现代通信原理Principles of Modern Communications-Li Hao,20121.5BlockdiagramofacommunicationsystemSignal processingCarriercircuitsTransmissionMedium(channel)CarriercircuitsSignal processingInformationInputTransmi
20、tternoiseTo informationsink(user)Receiver1-17-现代通信原理Principles of Modern Communications-Li Hao,2012模拟通信系统一般模型信信息息源源调制调制器器信信道道解调解调器器收收信信者者噪声源噪声源模拟广播通信系统模拟广播通信系统1-18-现代通信原理Principles of Modern Communications-Li Hao,2012数字通信系统一般模型信信息息源源信信道道噪声源噪声源信信源源编编码码信信道道编编码码调调制制器器解解调调器器信信道道译译码码信信源源解解码码收收信信者者GSM通信系统
21、计算机通过网线连接1-19-现代通信原理Principles of Modern Communications-Li Hao,20121.6Example:RadiobroadcastTwomodesareusedAMAmplitudemodulation535-1605kHz10kHzchannelsFMFrequencymodulation88-108MHzChannelscenteredat200kHzintervalsstartingat88.1MHz1-20-现代通信原理Principles of Modern Communications-Li Hao,2012Example:PS
22、TNLocalexchangeInternationalexchangeLong distanceexchangeLocalexchangeLocal lineLong distance lineLong distance lineInternational linePublicSwitchedTelephoneNetworkComponentsPhoneset(analogsignalisgenerated)Localexchange(A/Dconversion)Long-haulexchangeCharacteristicsCircuit-switchednetworkDesignedfo
23、rvoicecommunicationsFaxesandmodemsusePSTNfortransmissionofdigitaldatainanalogformModem1-21-现代通信原理Principles of Modern Communications-Li Hao,2012Example:CellularBeijing MTSOPSTNMTSOChengdu MTSO:Mobile TelephoneSwitching OfficeCellularCommunicationSystemAcellisassignedsomenumberofchannelsTypicallyonec
24、hannelisallocatedtoauserUserscommunicatewithabasestationBasestationisconnectedtoMTSO/PSTNAMPSisananalogsystemUsesFMandfrequency-divisionmultipleaccessDigitalsystemsusedigitalmodulation1-22-现代通信原理Principles of Modern Communications-Li Hao,2012Example:ComputerNetworksSwitch802.11 APLocalAreaNetworks(LANs)Connect“closely”locatedcomputersVariousLANprotocolsareusedinpracticeIEEE802.11b(WLAN)11Mb/sdatarate2.4-2.4835GHzbandModulation:Directsequencespreadspectrum(DSSS)IEEE802.11a(WLAN)55Mb/sdatarate5.725-5.825GHzband(inU.S.)Usesorthogonalfrequencydivisionmultiplexing(OFDM)