资源描述：
《Homework.doc》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。
1、DiscussionTopicsLiangHao142107201811.Whatthebasicfunctionalblocksareincludedinadigitalcommunicationsystem?Sourceencoder,channelencoder,digitalmodulator,digitaldemodulator,channeldemodulator,sourcedecoder.2.Whataretheaveragemutualinformation,entropy,andconditionalentropy?Whatistherelationshipofthes
2、ethreeconcepts?FortwodiscreterandomvariablesXandY,ThemutualinformationisdefinedasWherep(x,y)isthejointprobabilitydistributionfunctionofXandY,andp(x)andp(y)arethemarginalprobabilitydistributionfunctionsofXandYrespectively.Animportantcharacteristicoftheaveragemutualinformationisthat.WhenXandYarestat
3、isticallyindependent,wedefineaverageself-informationas:WhenXrepresentsthealphabetofpossibleoutputlettersfromasource,representstheaverageself-informationpersourceletter,anditiscalledtheentropyofthesource.Anaverageconditionalself-informationiscalledconditionalentropy.It’sdefinedas:Therelationshipbet
4、weenthemutualinformation,entropyandconditionalentropyis:3.WhatistheShannonsourcecodingtheorem?In informationtheory, Shannon'ssourcecodingtheorem (or noiselesscodingtheorem)establishesthelimitstopossible datacompression,andtheoperationalmeaningofthe Shannonentropy.The sourcecodingtheorem showsthat(
5、inthelimit,asthelengthofastreamof independentandidentically-distributedrandomvariable(i.i.d.) datatendstoinfinity)itisimpossibletocompressthedatasuchthatthecoderate(averagenumberofbitspersymbol)islessthantheShannonentropyofthesource,withoutitbeingvirtuallycertainthatinformationwillbelost.Howeverit
6、ispossibletogetthecoderatearbitrarilyclosetotheShannonentropy,withnegligibleprobabilityofloss.1.Howtorepresenttheband-passsignalusinglow-passsignal?Firstlydevelopamathematicalrepresentationofsuchsignalsconstructasignalthatcontainsonlythepositivefrequenciesins(t).ThesignalSt(t)iscalledtheanalyticor
7、thepre-envelopeofs(t):Defineasthesignalmaybeviewedastheoutputofthefilterwithimpulseresponseh(t).Theanalyticisaband-passsignal，wemayobtainanequivalentlow-passrepresentationbyperformingafrequencytranslation：DefineS
