Examples of communication Diagram and elements of Comm.Sys Digital Comm.Sys. Channels and their characteristics UESTC-Introduction Prof李晓峰 2
Elements of Comm.Sys Communication systems are electronic systems designed to transmit information UESTC-Introduction Prof李晓峰 3
Elements of Comm.Sys Communication systems are electronic systems designed to transmit information In general,the infor/msg is Noise TRANSMITTER n(t) RE said to be generated by a information/msg source. Information Transmission r( Info must be something input Signal Carrier s( 1) processing medium circuits unknown and mathematically (channel) described by random signals, also called random processes. m The information or massage may be voic Information/message text,or a file. signal:to represent the .Voice:in telephony,a microphone is us information or message. Transmission signal:to 2.Text:in mobile SMS,a keypad system i go through the channel 3.Video:in network,a video-camera is.. UESTC-Introduction Prof李晓峰 4
Elements of Comm.Sys Communication systems are electronic systems designed to transmit information Noise TRANSMITTER n(t) RECEIVER Information input Transmission Signal Carrier s( r(t Carrier Signal m() medium 11） processing circuits circuits processing (channel) iTo information sink(user) A waveform is basically a time-continuous signal,called analog signal. A seq of data is basically a time-discrete signal with finite values,called digital signal. UESTC-Introduction Prof李晓峰 5
Elements of Comm.Sys Communication systems are electronic systems designed to transmit information Noise TRANSMITTER n(t) RECEIVER Information input Signal Carrier s(I Transmission r() Carrier Signal m() medium 1） processing circuits circuits processing (channel) iTo information sink(user) Channel:the physical media to transmit Say,wire-lines,cables,open space and optical fiber cables Channel is often non-ideal,introducing distortion and noise. UESTC-Introduction Prof李晓峰 6