资源描述：
《无线网络中的voip服务质量仿真分析》由会员上传分享，免费在线阅读，更多相关内容在学术论文-天天文库。
1、1.1.1TypesofVoIPVoiceoverIP,asitsliteralmeaningsuggests,isatechnologythattransformsthevoicesignaltoIPpacketsanddeliveredbyIPinnetworks.Itpavedthewayforacomprehensiveapproachtothedesignofplatformsforvoicecommunicationsservices.Buttherealengineistheconverg
2、encebetweenheterogeneouscommunicationsnetworktechnology[4]-[5].VoIPservicehasseveraldifferenttypesdependingontheinfrastructureusedforthecommunication:computer-to-computerbasedVoIP,computer-to-PhonebasedVoIPandPhone-to-PhonebasedVoIP.Eachtypeofthemhasdiff
3、erentsetofrequirements.PC-to-PCIPNetworkISPISPInternetIPTelephonyIPTelephonyPC-PhoneenablePCenablePCIPNetworkPSTNISPInternetISPGatewayTerminalphoneIPTelephonyPhone-to-PhoneenablePCPSTNIPNetworkPSTNISPISPGatewayInternetGatewayTerminalphoneTerminalphoneFig
4、ure1.2ThreeCategoriesofVoIPservicesComputertocomputer:VoIPservicesusinginternettelephonytechnologyviacomputersaretotallycostfree.ThistypeofVoIPapplicationsmakeuseofspecializedsoftware(softphonesoftware)suchasSkype,AOLInstantMessenger,MSNMessengerandetc,t
5、hatrequireuserstodownloadandinstalltheirsoftwareonthePC,thecallerandreceivermustusethesameVoIPsoftwareapplication(Forexample,SkypetoSkype,MSNtoMSN,etc.),thecallerandreceiverareprovidedbasedonanapproachofpeer-to-peerviatheInternet.Therequirementsforthecom
6、putertotheInternettelephonyforthecomputerincludeasoftphonesoftware,soundcardandInternetaccess.Computertophone:BecausetheInternetandcircuit-switchedsystemsusingconventionalphonesystemsaredifferentfromsoftphonesoftware,theyneedroutethecallviaInternetprotoc
7、olandhandsitofftoaconventionaltelephonenetwork.Skype,MSN,GoogleTalkandalsoprovideservicestouserstomakecallsfromcomputerstotraditionalphones.Requirementsinclude:theVoIPservices,Internetaccess,amodemandanAnalog2TerminalAdapter(ATA),whichconvertstheanalogsi
8、gnaltodigitalsignal(andviceversa).TelephonetoComputer:WiththisserviceuserscanmakephonecallsfromtraditionalphonestocomputersandaphonenumberwillbeassignedtotheIPaddressofacomputerandtheusercandialthenumber,likemakingphonecal
