IMS-based Fixed-mobile Network Convergence And Evoluton

Fixed Mobile Convergence (FMC) refers to a given network, to provide end users with theability and mechanisms of the business or application, independent with fixed/mobile accesstechnologies and the location of the user. From the user’s perspective, the purpose of FMC is toenable users to enjoy the same services, access to the same business through different accessnetworks. FMC is becoming the inevitable trend of the development of next-generationcommunications networks.IP Multimedia Subsystem(IMS) is a subsystem,proposed by the third Generation PartnershipProject R5version, to support IP multimedia services. As its control layer functions is furtherdecomposed,it makes the network more open and smart, IMS actually performs more“soft’’thanthe traditional Softswitch. Besides，the adaptability to a variety of access technologies has madeIMS as the evolution fundament of Fixed Mobile Convergence. IMS is considered to be the coretechnology of next generation networks、 the solutions of Fixed Mobile Convergence, theimportant mode of introducing voice, data and video triple fusion business， It can besaid that the IMS system matches the next generation network NGN principle.The current status and and standardization of IMS based Fixed-Mobile Convergense was describedat first of this paper.Additional，we described IMS in detail, the key technologies to achieve FMC,including the IMS network architecture, functional entities and protocol.Secondly, this paper proposes two kinds of fixed-mobile convergence solutions: basedon Unlicensed Mobile Access UMA of fixed-mobile convergence and IMS-based fixed-mobileconvergence. Through analyzing and comparing these two kinds of solutions, We point out IMS isthe best choice to achieve the full range of network integration.But the quality of service(Qos) provided by IMS now is less than the traditional voice quality.So the legacy circuit switch domain will coexist with IMS domain in a long time. When thesubscriber transfers between the two domains,how to keep the continuity of the voice call is aproblem that should be solved quickly. Based on the research of IMS,this paper gave a detaileddesign of the service handle process of VCC solution,and estimate the handoff delay when thedomains transfer occuerring,and established the mathematical model using the probabilitytheory and network queuing theory,quantifiably analyzed the domain switching delay. The analysis shows that the main factors to affect the VCC domain handoff latency include:wirelesslink transmission rate, frame error probability, the Session Initiati on Protocol SIP compressionmechanism, the maximum retransmission number of frame. Through the numerical simulationshows that, the wireless link transmission rate and frame error probability deeply influenced VCCdomain handoff delay, while the use of SIP compression mechanism can greatly reduce the domainhandoff delay in the3G environment. Finally,take the CM-IMS networkconstruction for example,we talk about the specific Application of IMS-based Fixed MobileConvergence, obtained from the network integration strategy of China Mobile and CTT,and giventhe recommendations of the future evolution of the program.