Design And Implementation Of Presence Server In IP Multimedia Subsystem Of 3G Core Network

The mobile communication technology is evolving from 2G towards 3G, and the core network is evolving from Circuit Switch towards Package Switch. To provide multimedia services, the 3GPP (the Third Generation Partner Plan) has introduced the concept of IMS (IP Multimedia Subsystem) in the Release 5 of its 3G Specifications. As the main part of the 3G Core Network, IMS will converge multimedia services including video, audio, message, data, etc. based on the IP packaged domain. So it will become a key technology of convergence and a main developing trend of NGN (Next Generation Network). SIP Application Sever (SIP AS) is one kind of Application Server that hosts and executes IMS special services using SIP (Session Initiation Protocol). And Presence is a typical value-added service. As a basic service, it provides a foundation for developing rich enhanced multimedia services. This paper focuses on the design and implementation of such a kind of SIP AS that provides Presence Service, called Presence Server.In the first part, the paper introduces the system architecture of IP Multimedia Subsystem, the 3G Core Network. And then it analyses the Application Server and Presence Service in IMS. Based on these issues, the requirement of Presence Server in IMS is put forward.In the second part, after thorough researches and analysis of the Presence Service, a function model of Presence Server is provided. This provides the foundation for design to fulfill the Presence Service requirement.Based on the function model, in the third part, this paper presents the design details of Presence Server in the view of layered architecture, including the Protocol Layer, the Access Layer, the Control Layer, the Service Layer and the Data Layer. And also presents the design details in the view of message process, such as the subscription state machine.Finally, the paper describes the implementation and test of Presence Server. The test results prove that the design and implementation of Presence Server is feasible for Presence Service in IMS system.