Proposal for Distributed IMS by Hierarchical Administrative Domain

In recent years, IMS architectures standardized by 3GPP have gained importance as the key technologies for the Next Generation Network that will provide high quality services over an IP network. These systems are being put to practical use and are mainly maintained and operated by telecommunication operators. In the future, deployment of new IMS services such as an IMS-based IPTV service and IMS-based office network will substantially increase the number of IMS-compatible devices. Such an increase raises concerns about overloading the telecommunication operator's IMS facilities, which are maintained in a centralized manner. On the other hand, in-house communications, such as an extension line via a PBX, can be managed internally. In this paper, we propose a method to distribute the maintenance of subscribers and localize the control traffic by separating the IMS into hierarchical and internally-controllable IMSs based on administrative domains in order to reduce the load on the telecommunication operator's facilities. Further, we implement and evaluate the proposed method, and show its benefits.