Research On IMS-Based Service Discovery Architecture For Next-Generation Networks

IP multimedia subsystem (IMS) realizes the end-to-end IP multimedia communications, and extends the applications of 3G networks from the simple voice and data services to multimedia area. Besides providing traditional multimedia services, IMS has the capabilities to exploit the novel services and reuse the third-part-exploited services which based on Internet. Because IMS is independent of access technologies and has far-ranging adaptability to all kinds of access, the standardization organizations, such as 3GPP, 3GPP2, ETSI TISPAN and ITU-T, have started the in-depth research on IMS defined by 3GPP, in order to realize the uniform support to fixed and mobile users which based on different access technologies by extending the IMS functions. The aim is providing multimedia services to both the fixed and mobile access users simultaneously by developing IMS as the universal platform and using IMS as the fixed-and-mobile-converged common core network. It is considered that the core network architecture based on IMS is the fixed-and-mobile-converged uniform target architecture, and the research of the architechture becomes the hotspot in communications area these years.According to the development of the international and internal standard researches, IMS is confirmed to be the uniform core architecture of NGN which based on all kinds of service networks, but the NGN standards based on all kinds of access technologies (including wire and wireless access) are not mature and the researches related to NGN based on the IMS core network architecture still need a long time. One of the most important problems which need to be solved urgently is described as follows. After IMS realizes the convergence of the fixed and mobile networks, and has the capabilities to provide diversified multimedia services and uniform service and application platform, how does the IMS-based network provide service discovery (SD) function with great efficiency when services become more numerous, various and complicated.Based on above analyses, this dissertation mainly focuses on the IMS-based SD architecture for next-generation networks and the interrelated technology points in details. The major content and framework are listed in following aspects,(1) Analyze the status of IMS-based SD research in deep. The analyses indicate that, the related standards organizations, such as 3GPP, have not confirmed the solution which for the SD based on IMS networks until now. At present, the heterogeneous network which applies IMS usually completes the SD function by transforming the different-network-technology-based services to the uniform IMS-based services. In order to complete the functions of SD and service provision, the network needs to import the added functionalities and even additional application platform. The cost is much expensive. There is a paper which ever refers to the way to realize the SD function using IMS architecture itself, but it just points out some conceivable choices. There is no description or argumentation in details, and no feasible research on the IMS-based SD architecture.(2) Widely investigate the main research fields and the latest development of SD. The results indicate that, studies of SD in recent years had been mainly emphasized on some specific and simplex network or system, such as mobile ad-hoc networks, web services frameworks and grid systems, and peer-to-peer overlay networks. These systems are comparatively simplex, and the corresponding design methods have certain restrictions. Further more, all of these researches tend to the architecture design and realization. Few are focused on logical theoretical analyses and optimal considerations of the SD mechanism or system.(3) Based on the integrative consideration of (1) and (2), this dissertation puts forward a novel service discovery architecture (SDA) which can be applied to NGN, and describes the realization of the SD function in details. The main idea is that, according to the characteristics of IMS, use the existing IMS functionalities to establish a novel SDA and realize the SD function quickly and efficiently. Because the realization of SD needs no added entities, the cost is comparatively less, and the SD function can be integrated well in the IMS-based network. Moreover, the SD function only works in the IP Multimedia Core Network Subsystem, and can coexist with any existing SD technology which is the solution for certain specific access network. The new SDA provides a global user approach, independent of any specific network access. It is a universal solution of SD.(4) Due to import the new function, analyze the influences to the IMS network of the novel SDA in (3). Do the comprehensive evaluations of the SDA by using mathematical modeling, theoretical analyses, and numerical simulations. The evaluations include the added cache cost in HSS for caching service information, the success rate of SD, and the traffic load caused by SD procedure. All the performance analyses are based on the condideration of the influences of the average update interval of service announcements (SAs) I_SA, the mean interval between two adjacent service requests I_SrvRqt, and the network condition variability. The results of the evaluations indicate that, the added cache cost in HSS is less and the added traffic load caused by the SD procedure is not high. That is, the influences to the existing IMS network are on the small side. But the success rate of the SD is much higher.(5) Considering the analyses in (4), optimize the performances of SDA by the mathematical consequences and arithmetical simulations. It is worth to mention that an optimum value of I_SA was found. This value makes the performances reach trade-off. As for a certain given IMS-based network, the selection of optimum I_Sa is just related to the value of the average lifetime of SAs T_L. I_sa and T_L are correspondingly fixed and all can be set by Application Servers. So, the value of I_sa can be assigned and adjusted by the IMS network operator, and then make all the IMS-based SD be controlled. Comparing optimizing the performances by controlling I_SrvRqt (determined by the users) and the network condition (real-time changing), it is quite a simple and practical policy for IMS network operator to set and adjust the network variational parameters to obtain the optimum performances according to the network requirements.