The Research And Implementation Of The Interworking Between IMS And The CS Network Based On 3GPP R4

With the rapid advancement of technology and the increasing demand of customer,the IMS(IP Multimedia Subsystem)which can provide the overall multimedia services of speech,data and video with high quality is becoming the trend of the development of telecom network.The CS(Circuit-Switched)network based on 3GPP R4 can still develop potentially,and it has many new customers to expand,the speech operations are still the main profits to telecom dealer.It will be a big cost and waste if two networks access separately.Therefore,it is very important to realize the interworking between IMS and the CS network based on 3GPP R4.IMS is based on SIP(Session Initiation Protocol)protocol,but the CS network based on 3GPP R4 adopts BICC(Bearer Independent Call Control)protocol for interworking between the ports,it does not support SIP protocol.Therefore,one key point for interworking between IMS and the CS network based on 3GPP R4 is to realize the interworking between SIP and BICC.The thesis which is a part of the project of IMS in Alcatel Shanghai Bell elaborates the interworking between SIP and BICC based on the interworking of IMS, designs and implements the interworking unit IWU between SIP and BICC.The main contributions are as follows:1.Analyzes the architecture,the consulting model and consulting points of the interworking between IMS and the CS network based on 3GPP R4 referring to the scheme of IMS in Alcatel Shanghai Bell,and the interworking of the controlling layers between SIP and BICC is also discussed.2.Elaborates the interworking between SIP and BICC both in the basic speech operations and the complementary speech operations,which include the analysis of the working flows and the mapping of the messages.3.Referring to the scheme of IMS in Alcatel Shanghai Bell,the interworking unit IWU between SIP and BICC,which mainly includes the implementary mechanism,the logic of class flows,the corresponding interfaces,the mapped codes and the message handling flows,are designed and implemented based on the analysis of the interworking between IMS and the CS network 3GPP R4-based.In order to improve the efficiency,the IWU adopts the way of multithreading to implement the interworking between SIP and BICC;And the IWU accommodates the SIP terminals with SDP which include 180 Ringing,183 Session Progress and 200 OK according to the different bearer methods of BICC;In order to enhance the program's stability and robustness,the IWU sets the judgments of the state machines in the message handling flows.4.The interworking of the complementary speech operations,which include call hold,call diversion and calling number presetntation/restriction,is also implemented in IWU.