1.ADC PCM The unit doing the conversion is called ADC. There are 2 important operations, 1. discrete in TIME; 0→[ 2. discrete in Value; xn川]→x[n Analog waveform Discrete sequence Digital sequence Sampling Quantizing t1:-04.88V t2:+21.43v 21 Sampling:to sample the analog waveform every Ts and outputs a sequence of samples. Quantizing:to approximating the continuous value by using finite numbers of levels UESTC-Digital transmission through the AWGN channel Prof李晓峰 9