Satoshi Komorita

Self organizing IP Multimedia Subsystem

While there have been tremendous efforts to develop the architecture and protocols to support advanced Internet-based services over 3G and 4G networks, IMS is far from being deployed in a wide scale manner. Effort to create an operator controlled signaling infrastructure using IP-based protocols has resulted in a large number of functional components and interactions between those components. Thus, the carriers are trying to explore alternative ways to deploy IMS that will allow them to manage their network in a cost effective manner while offering the value-added services. One of such approaches is self organization of IMS. The self organizing IMS can enable the IMS functional components and corresponding nodes to adapt them dynamically based on the features like network load, number of users and available system resources. This paper introduces such a self organizing and adaptive IMS architecture, describes the advanced functions and demonstrates the initial results from the prototype test-bed. In particular, we show how all IMS functional components can be merged and split among different nodes as the network demand and environment change without disrupting the ongoing sessions or calls. Although it is too early to conclude the effectiveness of self organizing IMS, initial results are encouraging and it may provide additional incentives to the operators for network evolution.

Loosely coupled service composition for deployment of next generation service overlay networks

In order to provide various attractive services to users, a user-centric approach such as usergenerated contents and services and a platform which can create a service easily and efficiently have been studied and designed during the past two decades. The IEEE NGSON standard has defined a functional architecture that provides advanced overlay functions for value-added services by collaboration of services with features of context awareness, dynamic adaptation and self-organizing management. Its service composition mechanism is comparable with service oriented architecture. However, due to SOAs complexity, it has not become as popular for user-generated services and contents as so-called mashup technologies, which also provide attractive and simple service creation. In this article we propose the adoption of loosely coupled service composition into the NGSON framework that can easily integrate existing communications and data services with little to no dependence on the underlying implementation and service description language details. Furthermore, the NGSON prototype supporting our proposal is presented as a proof of concept and to verify its advantages for operators, service providers, and end users.

Service continuity support in self-organizing IMS networks

With the increasing interest in deploying 4G/LTE networks, IMS has a potential to be deployed in a wide scale in order to support mobile Internet and value-added services over next-generation networks. Moreover, the effort to create an operator-controlled signaling infrastructure using IP-based protocols has resulted in a large number of functional components and interactions between core networks elements. Thus, the carriers are trying to explore alternative ways to deploy IMS that will allow them to manage their network in a cost effective manner while offering rich communications services. One of such approaches is self-organization of IMS (SOIMS). The self-organizing IMS can enable the IMS functional components to adapt dynamically based on the features like network load, number of users, node failures and available system resources. This paper proposes different mechanisms to handle self-organizing IMS with usage of load balancing paradigm. The proposed solution enables topology hiding, IMS nodes failure recovery, session continuity support, and IMS scalability.

Enhanced Next-Generation Service Overlay Networks architecture

The Web Services composition paradigm has been widely used in Information Technology (IT) and Internet environments to create Web applications that both flexible and rapidly deployable. Web Services are a key way to realize Service-Oriented Architectures (SOA). In Telecom, on the other hand, the IMS (IP Multimedia Subsystem) architecture enables valued-added services composition for IP-based networks. Several ongoing efforts - referred to as “SOA for telecom” (SOA-TEL) - are attempting to merge SOA with telecom. The objective of these attempts is to enable Telecom operators and service providers to re-use existing service building blocks while building valued-added converged Web and telephony services. These services offer seamless experiences across various networks and, therefore, richer experiences, but are more complex than typical Web Services (e.g., transaction-based). The IEEE Next-Generation Service Overlay Networks (NGSON) working group is focusing on this integration and an architecture has been proposed. In addition, NGSON specifies context-aware, dynamically adaptive, and self-organizing networking capabilities. There are, however, a number of shortcomings in the NGSON architecture. This paper identifies these shortcomings and describes a possible solution. Finally, we discuss an illustrative use case scenario to help bring clarity to our proposed “enhanced” NSGON architecture.

User-transparent reconfiguration method for self-organizing IP multimedia subsystem

The NGN (Next Generation Network), which can provide advanced multimedia services over an all-IP based network, has been the subject of considerable attention for several years. While there have been tremendous efforts to develop its architecture and protocols, especially for IMS, a key technology of the NGN, its wide deployment is still a long way off. However, efforts to create an advanced signaling infrastructure able to meet many requirements have resulted in a large number of functional components and interactions between these components. Thus, the carriers are trying to explore effective ways to deploy IMS while offering value-added services. As one such approach, we have proposed a self-organizing IMS. A self-organizing IMS enables IMS functional components and corresponding physical nodes to adapt dynamically and automatically based on actual conditions such as network load and available system resources while continuing IMS operation. To realize this, service continuity for users is an important requirement when a reconfiguration occurs during operation. In this paper, we propose a mechanism that will provide service continuity to users without any impact on clients by extending the SBC (Session Border Controller). Furthermore, we implement it, show its behavior and evaluate its processing time.

Congestion-based automatic calling for improving call establishment in VoLTE

Through the introduction of LTE (Long Term Evolution), which is a next-generation radio access network, the traditional circuit switching system in cellular telephony networks is migrating to VoLTE (Voice over LTE). Although LTE can provide high quality and high bandwidth, the call processing capacity of a VoLTE system is designed for normal traffic density, as is the traditional cellular network. However, its performance, measured by the successful call rate, deteriorates when overwhelmed by the large number of calls generated by the special circumstances such as large gatherings and disasters. At such times, users continue to retry calls until the call goes through, resulting in additional degradation of system performance. In this paper, we propose a novel method to improve performance in such circumstances by placing a hold on calls that are likely to fail, and automatically making those calls in IMS (IP Multimedia Subsystem), which is the main call-control function in VoLTE. Finally, we present a simulation of our proposal that demonstrates its effectiveness when users are persistent with their calls.

IMS-based Fast Session Handover with Available Network Resources Discovery of Access Networks

The rapid spread of smart phones causes the explosion of media traffic. This encourages mobile network operators (MNOs) to coordinate multiple access networks. For such an MNO, the IP Multimedia Subsystem (IMS) is a promising service control infrastructure to ensure a QoS guaranteed communication path for the media in the multi-access network. IMS-based service continuity enables user equipments (UEs) to continuously use IMS-based services (e.g., VoIP) even when the UEs make handovers between different access networks where the UE is assigned the different IP address, respectively. In the case where the UE cannot simultaneously use multiple wireless devices, there is the possibility of a long media disruption time during handovers. This is caused by several consecutive handovers as a result of attempting to discover the access network where the UE can have the QoS-guaranteed communications. In this paper, we propose a method for reducing the media disruption time when the UE makes handovers between different access networks. In the proposal, the UE proactively performs the service continuity procedure, and selects an access network that can provide the required network resources to the UE. We implement and evaluate the proposed method, and show how the media disruption time can be reduced.

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 operators 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 operators facilities. Further, we implement and evaluate the proposed method, and show its benefits.

Proxy-based MOBIKE fast handoff for femtocell integrated mobile network

Recently, small base stations such as femtocell and picocell are drawing attention as new components of wireless access networks. These small base stations are used not only to expand the wireless area within a large building, but also to increase bandwidth capacity and reduce the load on the core network. If multiple femtocells are deployed in an office building to expand the communication area, a handoff mechanism between femtocells is required to support the continuity of data communication. Especially, real-time applications such as VoIP require a seamless handoff mechanism. In this paper, we propose Proxy MOBIKE mechanisms that can realize an efficient handoff between femtocells and mitigate the difficulty of femtocell implementation resulting from supporting multiple protocols. We also implement our proposed mechanisms to verify and compare their effectiveness.