,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,现代通信原理课件,Chapter One,1,Introduction,Chapter One,Why?,Information Age,Information Superhighway,2,Application,military application;,common application;,Chapter One,3,What is a,communication system,?,Communication,systems,is used to transmit information.,1.1 Introduction,4,Key conceptions or words,(1)Information;,(2)Message;,(3)Signal;,(4)Waveforms,1.1 Introduction,5,1 Jimes C.Maxwell（1864）,2 Heinrich Hertz（1887）,Claude E.Shannon(1948),4.Winner,1.1 Introduction,6,Perspective of communication,Wire,optic-fiber and networks,wireless,1G-2G-3G-B3G,WLAN;MIMO and MIMO-OFDM,UWB,optic wireless communication,1.1 Introduction,7,What must be considered when you design a communication system?,1.,Selection of the information-bearing,waveform,2.Bandwidth and power of the,waveform,3.Effect of system noise on the received,information,4.Cost of the system,1.1 Introduction,8,1.2,Digital and Analog source and system,The generation of communication system,9,signal processor,In analog system it may be an analog low-pass filter;In hybrid one,it may be analog-to-digital converter(ADC),2)Function of signal-processing block in hybrid one,Source coding,Channel coding(adding parity and others),3)Function of Carrier Circuits,modulation,Function of transmitter,10,1）,Classification:wire and wireless,Wire channel including twisted-pair telephone line/Coaxial cables,waveguides and fiber-optic cables,Wireless channel having air,vacuum and seawater,2),Note,:The general principles of digital and analog modulation apply to all types of channels,although channel characteristics may impose constraints that favor a particular type of signaling,Channel,11,The receiver takes the corrupted signal at the channel output and converts it to a baseband signal that can be handled by the receiver baseband processor,and then the receiver baseband processor estimate the source information and output the estimation result,Receiver,12,The goal is to design communication system that transmit information to the receiver with as little deterioration as possible while satisfying design constrains such as allowable transmitted energy,allowable signal bandwidth and cost.,In digital system measure of deterioration is taken to be,bit error rate,(BER),while in analog system the performance measure is usually taken to be the,signal-to-noise ratio,(SNR)at the receiver output.,Summary,13,1.2,Digital and Analog source and system,Model of analog communication system,14,1.2,Digital and Analog source and system(model of digital communication system),15,1）Relatively inexpensive digital circuits,may be used,2）Privacy is preserved by using,data encryption,3）Greater dynamic range is possible,4）Data from different sources my be,transmitted over a common digital,transmission system,2,the advantage of digital system,1.2,Digital and Analog source and system,16,5）Noise does not accumulate in,long-distance systems by repeater,6）Error in detected data may be,small,even in large amount of noise,on the received signal,7）Error may often be corrected,by the use of coding,2,the advantage of digital system,1.2,Digital and Analog source and system,17,1)More bandwidth is required generally,2)Sychronization is required,3.,Disadvantages of Digital communication,1.2,Digital and Analog source and system,18,1.2,Digital and Analog source and system,(classification of communication system),according to physical properties of information,:,Telephone/data/image and so on,according to frequency,:,baseband transmitting/bandpass transmitting system,according to transmitting medium,:,wire/wireless,according to multiplexing patterm,:,Frequency division multiplexing access(FDMA),Time division multiplexing access(TDMS),Code division multiplexing access(CDMA),19,1.2,Digital and Analog source and system,Classification of communication patterm,Peer to peer communication,:,simplex;,half duplex;,duplex,Parallel transmitting communication,Series transmitting communication,20,Key conception,Digital information source,produces a finite set of possible messages.Such as typewriter and keyboard,Analog information source,produces messages that are defined on continuum.,Digital communication system,transfers information from a digital source to the intended receiver(sink),Analog communication system,transfers information from a analog source to the intended receiver(sink),1.2,Digital and Analog source and system,21,Deterministic waveform It can be modeled as a completely specified function of time,Random waveform(stochastic waveform),It can not be completely specified as a function of time and must be modeled probabilistically,Example:,1.3 Deterministic and Random waveforms,22,1)Property of the book,a.from easiness to difficulty,b.from concept to performance analysis,2)Methods of learning it,a.reading it again and again,b.grasping the important concept,c.understanding the basic communication system by deriving some key formula,d.,simulation using Matlab,1.4,The property of the book