The Design And Implement Of SIP-based IMS

IMS(IP Multimedia Subsystem) is a subsystem which supports to IP multimedia operation that is brought forward by 3GPP. Its marked characteristic is that it adopt SIP(Session Initiation Protocol) system, correspondence is not related to connecting mode, it has multimedia operation controlling function is separated from carrying capacity, calling is separated from conversation, applicationl is separated from service, operation is separated from network, mobile network is synchronized with internet, etc.SIP is proposed by IETF as IP phone call order protocol which is totally a text modality that to be used to establish, modify and terminate multimedia calls and conversation. It has many characters, for example: Request and Response Protocol, Simple and Extensible, Design for Mobility, Capability Negotiation, etc. It has been defined as one of the standard protocols over the 3G telecommunication.For the Presence Service, it's a typical service of the "Observer Pattern". The traditional method to implement it is to use RMI or CORBA, or install some plugs to send and receive information using socket. However, the methods above add the load to the client, and make the experience of costomer some kind of bad. Besides, in a traditional Web Conference System, the audio and video of a participant are shared by default with all the other participants. But as the development of the Web Conference in the business field, this kind of sharing should be controlled.This paper researched the system architecture and features of IMS and the structure of SIP, and also researched the architecture and technology of SIP-based IMS.This paper brought forward architecture of SIP-based IMS and implemented the functions on the Application Server end of the architecure, which included Instant Message, Buddy List, Presence Service, P2P VoP, Web Conference, etc. This paper did some attempt to combine the existed Web Service with the telecommunication Service. The users can communicate with friends on line using this system. For the Presence Service, in order to reduce the load of client, and improve the experience of costomer, this paper brought forward the architecture of implementing Server Push technology which is HTTP long-polling based to implement the Presence Service. For the Web Conference, in order to let the users control the sharing of audio, this paper researched the narrowband broadcast, and brought forward power predication to describe the control policy of the sharing of the audio. This paper also brought forward Policy Matrix to express, analyse and transfer the control policy of sharing of audio. By the creating and calculate the Policy Matrix, we can get the final policy of mixing the audio, create the mixing request, and send it to the Media Server which is in charge of mixing of audio. So the particiants of the conference can control the sharing of audio among the other participants according to the wish of him.