Introduction Many info signals are naturally in the forms of sequence,such as 1.A digital picture in JPEG file; 2.A video file in H.264 format; 3.A music file in MP3 format; 4. An email 00000120h:31393B36383B34323B3132323B32313B:19:68:42:122:21: 00000130h:31333B3130383B3137313B33393B3139:13:108:171:39:19 00000140h:363B3135335D2A343B0D0A0D0A726762:6:153]*4:,.,.rgb 00000150h:203D205B7267625F722C7267625F672C;=[xgbr,rgb_g, 00000160h:7267625F625D3B20256C6566742D3E72:xgbb]:1eft->x 00000170h:696768742052204720422E2075702D3E:1 ght R G B.up-> 00000180h:646F776E20626C61636B206669727379:down b1ackf1r3t 00000190h:2E0D0A0D0A25203234636F6C6F72204a:.···.号24co1orJ 000001a0h:50473F3F0D0A726762203D20205B0D0A:PG??..rgb=【.· This type of info signals is called digital signal and They are time- discrete and has finite values. UESTC-Digital transmission through the AWGN channel Prof李晓峰 5