On Service Triggering In IMS Network

With the evolution of communication networks, the requirement of the services provided becomes much higher than before. As IMS (IP Multimedia Subsystem) enables 3G (Three Generation) network to be a full-service converging network, it is doubtlessly becoming the focus of technical research. The success of an IMS network depends on the variety and QoS (Quality of service) of its services. A QoS guarantee must provide fast and effective service triggering support. Service triggering includes ATA (Application Triggering Architecture), STD (Service Triggering Data), STA (Service Triggering Algorithm) and STP (Service Triggering Protocol), etc. This thesis concentrates on the research of IMS service triggering, involving: 1. ATA, focusing on the research on the application triggering architecture enhancement and proposing a new ATA to solve the problem of existing ATA; 2. STD, focusing on the research on the existing 3GPP (3rd Generation Partnership Project) service triggering data, analyzing its problems and proposing a Service-Key based service triggering data; 3. STA, focusing on the research on the triggering performance, analyzing the performance problems of the exsiting 3GPP STA and proposing several optimized service triggering algorithm to improve the performance of the IMS service triggering system;4. SLT (Service Logic Triggering), analyzing the nonstandard part of the 3GPP specification, proposing an SLTM (Service Logic Triggering Mechanism) of SIP AS (Application Server) and studying the performance of the IMS service triggering based on SLTMThe principal contributions of the work presented in this thesis are:1) ATA in IMS: In the exsiting 3GPP ATA, the 3GPP has only defined and implemented the iFC (nitial Filter Criteria). 3GPP has also defined the sFC (subsequent Filter Criteria), but given no implementation. To solve this problem and enhance the existing 3GPP ATA, a SIP (Session Initiation Protocol) header based implementation of sFC is proposed, which can effectively control the triggering of subsequent SIP messages and increase the routing flexibility of subsequent SIP messages;The service triggering based on iFC and sFC is analyzed, which is lack of flexibility and exists unnecessary service triggering. To solve the problem of the extra signaling traffic load of S-CSCF and AS and network processing delay caused by the unnecessary service triggering, a CATA (Call-state based ATA) is proposed. After illustrating how to trigger a service in CATA, the relationship of iFC, sFC and cFC (call-state based Filter Criteria) is discussed.2) STD in IMS: To solve the problem of the exsiting 3GPP service triggering data, a SIP header based implementation of Service-Key is proposed. By expanding the new Service-Key data, the following advantages are achieved: a) S-CSCF and AS can finsish the service/service logic triggering in an simple and effective way and improve the performance of service triggering; b) the conflict of iFC between new services and old ones when deploying new services is solved; c) the multiple services are triggered by the S-CSCF at one time becomes true.3) STA in IMS: After the performance of iFC based service triggering algorithm which is proposed by the 3GPP is studied, three STAs are proposed to improve the performance of the service triggering: a) Based on the proposed implementation of sFC, a NDSTA (New Dynamic STA based on iFC and sFC) is proposed. Performance analysis indicates that NDSTA can efficiently reduce the signaling traffic load of the S-CSCF and AS, increase the throughput of the system and significantly reduce the session setup delay. b) A GSTA (Group based STA) is proposed. In GSTA, the S-CSCF can trigger a group AS/service to reduce the times of service triggering and further decrease the signaling traffic load of the S-CSCF and improve the throughput and performance of the S-CSCF. c) In CATA, a CSTA (Call-state based STA) is proposed. Performance analysis indicates that CSTA is a flexible and effective STA. And the technology of AS/service grouping and sFC can be integrated into the CSTA to futher impove the system performance and the Qos of IMS.4) SLTM in IMS: The concept of service logic triggering and SLTM (Service Logic Triggering Mechanism) of SIPAS are proposed. In SLTM, the detailed service logic triggering data is defined and a SLTA (Service Logic Triggering Algorithm) is proposed. And then the performance compare between service triggering of multiple service logic environment with SLTA and the existing 3GPP service triggering without SLTA is performed. Performance analysis indicates that the service triggering with SLTA can considerably imprve the efficiency of service triggering, the throughput of the S-CSCF and the system performance. The proposed service logic triggering mechanism perfects service triggering mechanism in IMS, and provides guidance to the design of SIP AS from the perspective of service triggering in IMS network.