Digital Comm.Sys. Transmitter src encoder,channel encoder and digital mod. Receiver is expanded accordingly. 1.Source encoder:represent the info in an efficient way,called compression.ADC for analog info. 2.Channel encoder:introduce some rule such that the receiver can detect or even correct errors 3.Digital modulator:converts the information into signals suitable for channel. Binary modulation maps a bit 1 or 0 into s1(t)or s0(t)respectively. M-ary modulation sends k bits at a time (M=2k)using M waveforms. UESTC-Introduction Prof李晓峰 12