Research and Implementation of Multimedia Fallback and Service Change Technology in WCDMA CS Domain
|Course||Computer Software and Theory|
|Keywords||Multimedia down Multimedia rebound Business change Carrying capacity User plane WCDMA|
With the development of 3G Mobile Network and the advancement ofMultimedia technology, also with the presence of more and more MobileTerminations, which have the multimedia capability, multimedia service,absolutely, will become the most important application of 3G .The presenceof3GMobileNetwork,resultinaproblem,whichisthemultiplexofexistingtelecommunicationnetwork,andmorethanfiveorsixnetworks coexist.As aresult, the people, who want to try a multimedia call, often encounter aproblem of calling failed. This is bad for experience of people who pay fortheservice,withoutquestion,thesatisfactionofclientwillbedroppeddown.whatismore,themobilecompany’scompetitivestrengthisdepressedbadly.The evolution of mobile telecommunication network, destine themultiplex of network, and the inevitability of communication betweendifferent type of network. As you know, multimedia call with mobilityis oneof the most important characters of 3G. Now multimedia call in 3G has beensupported, ISDN also support this service, but 2G network doesn’t.Unfortunately, the rate of land covered with 3G is limited, so the user of 3Gwhowant communicationwithuserof2G,ortheuserof3Gwhohandoverto2Gnetworkwhilemultimediacallisplaying,willencounterfailedcall,badlythis things strike the satisfaction of clients, and the usability of network wasdepressed.Because of the absence of mobile termination, which supportsmultimedia fallback, it is necessary for the mobile network to provide thisfunction, and also this is the mandatory function of soft-switch in 3GPPprotocol. Multimedia fallback is the change from multimedia call to speechcall during call setup; service change is the change from speech call tomultimedia call when call in active state, or back to speech. With respect tothe satisfaction of client and the usability of network, service change is asimportantasmultimediafallback.Obviously,mostofclientsisapttofallbackto speech instead of call released if a multimedia call can no longer besupported, while the call in active call. Perhaps after fallback the resource of network is upgrade, and a multimedia call can be supported again, then thenetwork may initiate a service change from speech to multimedia, and thechange need confirmed by user. Service upgrade has important significationfor the usabilityof network, also this is a essential character of soft-switch in3GPPprotocol.Soft-switch who is an open system, achieve the aim of separationbetween service and control, also between control and bearer.In other word,change the architecture of switch, separate the function of network entities,and standardize the interface between them. All of the changes bring anadvantage that everynetwork entities can develop and applynew technologyindependently. The separation of MSC and MGW is the main differencebetween R4 and R99, and this difference carry out the separation betweencontrolandbearer.Similarly, IUinterfacesplittocontrolplanelayeranduserplane layer. Therefore, correct transporting of parameters, and theunderstanding of process of codec or UP in MGW and RNC is an importanttache, which decide the result of the project, above all, we should know thatmultimediacallisatransparentandsynchronizedbearerservice.As you know, telecommunication service is a real time service. ATM isan optimal choice for telecommunication, because of good assurance of QoS,butopticalfiberisveryexpensive,sopopulationofATMisimpossible.TDM,because of the disadvantage of unshared circuit during call, will be fall intodisuse. Come to light, IP overcome the entire disadvantage, so all IP in corenetwork is proposed. Nb interface, which is the interface between MGW andMGW, support IP, so do Nc interface, which is the interface between MSCand MSC.Consequently, the mastery of UP or CODEC parameter of NbinterfaceisasimportantasIUinterface.The latest 3GPP protocol proposed two concepts, that is DummyCodec1 and DummyCodec2.Those concepts make processing of multimediacall like speech possible. Up to now, OoBTC and in-call modificationprocedure just do speech codec and service change from multimedia tospeech well. Mastering of the mechanism and current state of OoBTC orin-call modification procedure, also the research of Dummy codec concept,makesuretheprogressoftheproject.Duringthe development of this project, author taked part in requirement analysis, system design, coding and system testing. Concretely, include fiveaspectswork:Firstly, reference a suppose in 3GPP OoBTC protocol, proposed anmethod, which make Call-Proceeding message send lately. Then multimediafallbackwithouttouchingoffModifyProcedurecametrue.Secondly, implement Dummy codec1 and Dummy Codec2 in OoBTCprocedure, then we can operate multimedia call negotiation, just like speechcall.Thirdly, implement service change from speech to multimedia, andenhanced the function, make MSC have the capability to avoid servicechangerepeatoccur,suchas,fallback,upgrade,thenfallback.Fourthly, with respect to inter-system handover, author implements thesolution and improved it. Use a global switch to control the Modifyprocedure.Lastly, author proposed a method, which resends SRI message after thefirstservicedidn’tregister.Late call-proceeding solution betters the direct Release process,implement the multimedia fallback function, and raise the satisfaction ofclientandtheusabilityofnetwork.While a multimedia call is active, inter-system handover happened, ifwe fallback the call, and wait next relocation, perhaps make conflict withsomebody’s understand, because of the blurry of 3GPPprotocol .so we use aglobal switch to control this procedure, then we can adapt people’srequirementflexibly.After system testing, we have implemented all of the function, whichlisted in scenario analysis. Interface parameter and function is correct. Now,this version has passed Technology Review Point, and applies in manycountries’mobile company, such as, Bahrain, Qatar, and Arab. This versionsatisfies the requirement of market, and successfully drops down the clients’complaints. We think that our work enhanced the competitive strength ofmobilecompany,andmakecommunicationsmootherthaneverbefore.