Digital Comm.Sys. A analog communication system transfers analog msg signals. For analog info,we measure the difference of the restored signal and the src signal,or the SNR(ratio of the signal pwr to the pwr of the difference). A digital communication system transfers digital msg signals. The performance is often evaluated in term of rate of error in bits(BER),equivalent to the probability of the bit error,Pb. 100-1111-100-1111-100-1111 UESTC-Introduction Prof李晓峰 5