The Realization Of The Presence Service System Based On The IMS Territory And The Improvement Of The Roaming Control

Along with the widespread application of Internet and the fast development of the telecom, people's demand on communications increasingly becomes abundant, which impulses the development of the new telecom technology and service. IP multimedia system (IMS) is the important platform of the NGN which is representative of the direction of the future mobile and multimedia services development. The horizontal way of service providing which makes the call control and the service application evolvable is used in IMS. The multimedia service can be flexibly customized and rapidly brought to market. The service can be effectly managed and controlled simultaneity. In various 3G services ,the presence service is most important application of IP multimedia system(IMS)of 3G in the future.The supporting ability to service of the IMS and how to introduce IMS into the new service of 3G. are studied in the dissertation.The main works are described as follows:①The project design of the Presence service based on the IMS territory is brought forward , and the service is carried out.1) In this dissertation, in order to realize the Presence service based on the IMS, the IMS network is taken as the background. The network system architecture of the Presence service is analyzed.2) The design of the Presence service based on the IMS territory is brought forward.3) The presence service is carried out. In the system, the logical function is realized by the x-CSCF combination in the IMS network. The function includes the information issue, the policy setting, the notification and the resource list.②The improved way of the roaming control for the fixed subscriber of the IMS network is brought forward.In the forepart of the IMS deployment, the IMS core network element is deployed centralized whereas the SBC is deployed dispersedly. The register flow which is defined by the 3GPP standard couldn't judge the position information of the subscriber, so the roaming control couldn't be realized. So the improved way of the roaming control of the fixed subscriber for the presence service is brought forward to resolve the problem. The network ID of the corresponding SBC is added to the list according to the allowable roaming area which is signed by the user. The HSS can judge whether the SBC exists in the allowable network list of the user or not according to the Visited-Network-Identifier ID in the UAR message. The roaming actions of the subscribers are effectly controlled. The network access with exceeding authority is prevented. The abuse of the network resource is avoided which is utilized to developing correlative service of the roaming subscriber.The system was used in the sub-project of the CHONGQING branch of the CHINA UNICOM IMS experimental project. The instant message service controlled by the IMS core is carried out.There is still respectable technology difficulty . More attention should be paied to the process of the Presence service development. The future work mainly lies in exploring the network which is available for the operating and the performance improvement of the Presence service system.