Research And Implementation Of Call Control In Softswitch

NGN(Next Generation Network )is a service-driven network.How to open up the network capability,provide all kinds of multiparty and multimedia services flexibly has been the research focus for years.Also,NGN is a converged network,it is requested to converge different networks,different protocols and different services.And these are all to some extent depends on the disgn of the call control model.While traditional call control model is based on the caller-callee,it is not suitable for multiparty and multimedia calls.This thesis is focused on how to design a common call control model which is suitable for multimedia and multiparty services.NGN Softswitch and Service Provide System is designed to provide a common,flexible,efficent Softswitch and service provide platform,which can easily provide all kinds of multiparty and multimedia services.This thesis tries to research on a enhanced call control model and design a Softswitch call control subsystem based on the model to enable the Softswitch with multiparty and multimedia services.To do this ,we desgned a ContextView-Session-CallLeg control mechanism. We designed an Enhanced Call Control Model based on the results of call control model fields especially the CS-2 BCSM and the call control model in Project916.The Enhanced Call State Model not only describes the state of the call parties but also describes their relationships.The ECSM is composed of 3 sub-models:Call State Model which describes the signal state of call party,Media State Model which describes the media state and Session State Model which describes the session state.The ECSM doesn't focus on the calling pair(caller and callee),but based on independent call party so that it break the rule of traditional call control model,what's more ,it provides call relationship models which is never described before so it is very suitable for multiparty services. Also,the model greatly improves the capability of TLeg,and it introduces a special call party MS leg in case of multimedia call.The ECSM also includes a unified Media State Model based on SIP Offer-Answer model which is also suitable for other protocols.Based on the ECSM, a new call control subsystem is designed and described.Finally we proved the models and system by all kinds of services.With services and calls in real environment ,we can say that the models and the system is correct.