2.Modeling of digital source A simple model for the digital information source is the DMS(discrete memoryless source). {xn}=xo,1,X2,x3,…Xn,… A random process Let 4={a,a2,...,av}denote the set; p,P2,....P denote probabilities of the occurrence of the afs respectively. Suppose X is a rv.from the DMS.We have, P[X=a]=p(i=1,2,,M) A is called the alphabet of the DMS and a,a symbol.The src is said to be a M-ary source,while M is the size of the alphabet. UESTC-Digital transmission through the AWGN channel Prof李晓峰 7