5.6.10 Comparison of modulations 1)Efficiency,Rb 2)Reliability,Pb Recall a general block diagram of digital communication {,-1,0,a41H s,(t) n() {,an} Mod. Channel Recv 1R,=1/T Digital communication system It is natural to evaluation the whole systems in 2 aspects: 1)Efficiency,how fast?Rs 2)Reliability,how many errors?Pe More generally,we talk about the bit-rate Rb and bit-err Pb respectively We see that,1)R=kR,=(log2 M)R,,k=log:M 2)B=?P.With Gray code,we have P=P/k. UESTC-Digital transmission through the AWGN channel Prof李晓峰 4