IP Multimedia Subsystem Research Articles

VSS based session setup mechanism in IMS

This paper proposes a novel session setup mechanism in IMS (IP Multimedia Subsystem) by introducing the functional entity termed VSS (Visitor Subscriber Server) which is used to provide registration and location management. The new mechanism aims at improving session setup procedure by a betterment of location management in IMS. Through the use of two-tier subscriber information database constituted by the HSS (Home Subscriber Server) and the VSS, the new mechanism seperates the registration procedure and location management from the S-CSCF (Serving-Call’session Control Function), and makes them be handled by the VSS. At the same time, the new mechanism updates the signaling procedure of registration and session setup. With VSS based location management, the cost of registeration and session setup procedure as well as the delay of session setup procedure become lower. The cost and delay functions of the new session setup mechanism as well as the cost function of new registeration are deduced. Then, simulations and analysis verify that the performance of this new mechanism gets the benefit in cost and time.

Interworked WiMAX-3G cellular data networks: An architecture for mobility management and performance evaluation

This paper proposes an architecture for interworking heterogeneous all-IP networks with an in-depth analysis of its performance. The novelty of this framework is that it freely enables any 3G cellular technology, such as the Universal Mobile Telecommunications System (UMTS) or the CDMA 2000 system, to interwork with a given broadband wireless access (BWA) system, such as the Worldwide interoperability for microwave access (WiMAX) network or the wireless local area network (WLAN) via a common signaling plane. As a universal coupling mediator for real-time session negotiation and management between these dissimilar networks, the IP multimedia subsystem (IMS) has been exploited. The analytical evaluation investigates the behavior of handoff delay, transient packet loss, jitter, and signaling cost during a vertical handoff for the given framework. Finally, an OPNET based simulation platform has been introduced for the verification of the analytical model and results.

Quality of protection analysis and performance modeling in IP multimedia subsystem

IP Multimedia Subsystem (IMS) is widely considered as the main solution for the next generation multimedia rich communication. In order to provide multi-level security service in IMS to mobile users for multimedia applications, it is insufficient to take the security benefits into consideration, but adequately analyzing the impact of security policies in IMS on the performance cost quantitatively is also necessary and significant. In this paper, we first propose a novel study of IMS performance by a QPN model to much more precisely describe SIP signaling in IMS, and made performance evaluation. Then we defined totally seven levels of IMS security policies according to IMS specifications in 3GPP and proposed QoP partition model which quantitatively reflects strength of protection of SIP signaling and users’ security needs. Further more, we did our original contributions to use the QPN model to evaluate the impacts of security mechanism on system performance cost quantitatively. With the multi-view security partition introduced, different security policies could be adjusted according to the application and users’ security requirements, so that multi-level security service can be provided to diverse users and applications for a better tradeoff between security requirements and system performance in IMS.

IMS 기반 차세대 통신 환경에서 서비스 연속성을 위한 서비스 세션제어 기법

최근 디지털 정보통신 기술의 발전으로 네트워크 기술 및 성능의 적용 범위가 모든 분야로 확대됨에 따라 모든 정보단말, 가전기기, 사물 등이 하나의 네트워크로 연결되는 차세대 통신환경으로 진화되고 있다. 이러한 차세대 통신 환경에서의 핵심기술인 IMS(IP Multimedia Subsystem) 기반 네트워크에서 원활한 통합서비스(convergence service)의 제공을 위해서는 사용하던 정보단말이 바뀌거나 네트워크가 변화하더라도 이용 받던 서비스들을 그대로 제공 받을 수 있는 끊김없는(seamless) 서비스가 가능하여야 한다. 본 논문은 IMS Enabler를 통한 통합서비스 제공환경에서 사용자의 네트워크 환경의 변화나 정보단말의 변화에도 끊김없는 서비스를 제공하기 위한 세션제어기법과 그 구조를 제안하고 그에 따른 서비스 세션 제어 프로토콜(Service Session Control Protocol : SSCP)을 제시한다. Recently, the application of network technology extends to all areas because of development of digital information technology. Thus, networks are being evolved towards a next-generation communication environments where all information devices, home appliances, and object are connected and interoperated. In order to provide adequate convergence services in IMS-based networks that are the core technology of the next-generation communication environments, seamless service should be possible although the underlying network and the device in use may change in the networks. In this paper, we propose an efficient architecture, algorithm, and protocol of service session control for seamless service in such networks.

From IMS Management to SOA Based NGN Management

Although IP Multimedia Subsystem (IMS) based Next Generation Networks (NGNs) are already emerging as the common session control platform for converging fixed, mobile and cable networks, harmonized ...

Voice call handover mechanisms in next-generation 3GPP systems

The evolved 3GPP system is a hybrid mobile network architecture supporting several radio access technologies and several mobility mechanisms. In this article we briefly review the architecture and key components of this system, with particular emphasis on how it can support voice call mobility in several deployment scenarios. First, we present the so-called single-radio voice call continuity mechanisms that enable mid-call handover of VoIP calls from E-UTRAN access to the legacy UTRAN/GERAN or lxRTT access. Then we focus on deployment scenarios that do not support voice services on E-UTRAN and present the so-called fallback mechanisms that enable handover from E-UTRAN to UTRAN/GERAN or lxRTT at the beginning of a voice call. Finally, we address the application- layer voice call handover mechanisms enabled by the IP multimedia subsystem. Our conclusion is that the next generation of 3GPP systems are highly sophisticated mobile communication systems that support extended voice call mobility mechanisms, capable of addressing all commercial deployment needs.

A Caching Scheme for Session Setup in IMS Network

In IP Multimedia Subsystem (IMS), the session setup delay is a critical value for Quality of Service (QoS). The existing approaches to improve this metric depend on optimization of Session Initiation Protocol (SIP) message transmitting and signaling flows. Unfortunately, some service features are missing considered al-though they have been used widely in traditional 2G networks. This paper proposes a novel session setup scheme based on caching, upon the investigation of the performance of IMS session establishment. This mechanism involves cache based local routing policy and an adaptive caching algorithm, which can decrease call setup delay effectively as cached information in the terminating Serving-Call Session Control Function (S-CSCF) hit. The analytical model is deduced, as well as the delay and cost ratio functions are presented based on the model. Moreover, the analytical model is validated through the performance simulation in which the performance of the proposed novel method is evaluated against the basic session setup mechanism in terms of cost and delay.

Securing IMS against novel threats

Fixed mobile convergence (FMC) based on the 3GPP IP Multimedia Subsystem (IMS) is considered one of the most important communication technologies of this decade. Yet this all-IP-based network technology brings about the growing danger of security vulnerabilities in communication and data services. Protecting IMS infrastructure servers against malicious exploits poses a major challenge due to the huge number of systems that may be affected. We approach this problem by proposing an architecture for an autonomous and self-sufficient monitoring and protection system for devices and infrastructure inspired by network intrusion detection techniques. The crucial feature of our system is a signature-less detection of abnormal events and zero-day attacks. These attacks may be hidden in a single message or spread across a sequence of messages. Anomalies identified at any of the network domain's ingresses can be further analyzed for discriminative patterns that can be immediately distributed to all edge nodes in the network domain.

On performance of application triggering architecture in IMS network

The modeling of Application Triggering Architecture (ATA) in the IP Multimedia Subsystem (IMS) is presented. The session setup delay and system throughput are employed as the measurement to investigate the performance of ATA and the Serving Call Session Control Function (S-CSCF). With theoretical analysis and simulation results, we find that, the number of the ASs (Application Servers), the use of the subsequent Filter Criteria (sFC) and the arrival rate have heavy impact on the session setup delay and the S-CSCF is the major bottleneck in IMS network. The results are useful in constructing IMS network. At last, we propose several possible solutions to reduce the session setup delay and decrease the load of the S-CSCF.

Intrusion Detection System for Denial-of-Service flooding attacks in SIP communication networks

Security threats to Voice-over IP (VoIP) or IP Multimedia Subsystem (IMS) networks are becoming a major concern as their popularity increases. New attacks are being developed that directly target the underlying SIP protocol. To detect such kinds of attacks we are presenting a specification-based Intrusion Detection System (IDS) to recognise deviation from its expected protocol behaviour. We will present an implementation and show with measurements that this method is capable of attack detection and mitigation for different kinds of attacks directed towards a SIP infrastructure, with a focus on Denial-of-Service (DoS) message flooding.

Architectural aspects of automated network selection in heterogeneous wireless systems

Next-generation heterogeneous wireless systems using an all-IP transport allow converged services such as those based on IP Multimedia Subsystem (IMS) to be delivered over a variety of access technologies. These services however require underlying access technologies to support certain capabilities like Quality of Service. For devices supporting multiple access technologies this results in a complex problem of selection of an optimal service delivery access network. This paper addresses the architectural aspects of the problem by enhancing the roles of policy related components defined in cellular standards and by combining them with novel network selection components to enable automated network selection.

Standardization Paths for NGN IMS-Based Architecture

Thanks to the rapid development of technology and increased availability of bandwidth, today more than ever, multiple services such as voice, video and data can be integrated and efficiently carried over a single infrastructure based on a packet network. An NGN (Next Generation Network) is able to deploy those services independently from underlying transport-related technologies, giving fixed or mobile users an access to different providers with the adequate QoS and security. In fact, it is the IMS (IP Multimedia Subsystem) inside the NGN that enables and drives efficient converged service offerings. IMS provides the framework for a common service and session control layer standardized on IP, with SIP controlling all media sessions. The IMS standardization breaks down all the functions necessary to support multimedia applications and to provide standardized (open) interfaces towards application servers enabling enhanced premium services as well as the interworking with other (legacy) networks such as the PSTN/PLMN (Public Switched Telephone Network/Public Land Mobile Network. The paper is describing the current state of the art in the NGN standardization within the ETSI and related standardization bodies.

An analytical evaluation of mobility management in integrated WLAN-UMTS networks

Ensuring uninterrupted service continuity for handoff calls in an all-IP inter-networked heterogeneous environment requires successful session management among participating access networks. As such, a mobility-aware novel interworking architecture is presented in this article that facilitates session management including session establishment and seamless session handoff across different networks. This framework conveniently enables any 3G cellular technology such as the Universal Mobile Telecommunications System (UMTS) to interwork with a given Broadband Wireless Access (BWA) technology such as the Worldwide Interoperability for Microwave Access (WiMAX) network or the Wireless Local Area Network (WLAN) under a common signaling platform. This framework exploits the IP Multimedia Subsystem (IMS) as a universal coupling mediator for real-time session negotiation and management. Next, a Queuing Theory based analytical model for evaluating the performance of vertical handoff management between these interworked 3rd Generation (3G) cellular networks and the WLANs is presented. The analysis includes vertical handoff performance measures such as delay, transient packet loss, jitter, and signaling overhead/cost. The latter part of this paper presents some results from OPNET based simulations for the verification of the analytical model and results.

Difference-less mobility management network

Core system technology is a key factor in the next generation network (NGN). A difference-less mobility management network is proposed to better support the mobility of an IP multimedia subsystem (IMS). This kind of network can provide good service and user mobility, enabling local user access to the network anywhere.User locationmanagement and session creation are analyzed. The results show that under this network architecture, the cost of the user location registration and session creation is lower than that of the home control model employed by the IMS.

Open IMS

The IP Multimedia Subsystem (IMS) delivers an architecture for supporting multimedia services using Session Initiation Protocol (SIP) over Internet Protocol (IP) networks with managed quality of service (QoS). However, the IMS network was not designed to be “open” and therefore does not allow interworking with “non-IMS” user elements or networks. The IMS standards basically assume that media-rich end-to-end sessions over IP are only possible between IMS subscribers. We believe that this assumption is unnecessarily restrictive, since it does not allow IMS subscribers to interwork with the fast growing base of non-IMS IP broadband subscribers, who nevertheless are equipped to perform media-rich voice and video SIP sessions. This paper will show that allowing IMS subscribers to interwork with non-IMS (but still SIP-enabled) broadband subscribers is easy to achieve from a technical and architectural point of view. The proposed solution is safe, provides authentication, and allows IMS subscribers to take advantage of their terminating QoS even though they are accessed from the public IP network by a non-IMS subscriber. We will also show that this capability can generate new revenues in several ways and may also help to discourage wireless and wireline broadband subscribers from embracing nontraditional service providers such as Google, Skype, and Vonage.

SIP Multicast-Based Mobile Quality-of-Service Support over Heterogeneous IP Multimedia Subsystems

The Universal Mobile Telecommunications System (UMTS) all-IP network supports IP multimedia services through the IP multimedia subsystem (IMS). This paper proposes a mobile quality-of-service (QoS) framework for heterogeneous IMS interworking. To reduce the handoff disruption time, this framework supports the IMS mobility based on the concept of session initiation protocol (SIP) multicast. In our approach, the mobility of a user equipment (UE) is modeled as a transition in the multicast group membership. With the concept of dynamic shifting of the multicast group's members, the flow of actual data packets can be switched to the new route as quickly as possible. To overcome mobility impact on service guarantees, UEs need to make QoS resource reservations in advance at neighboring IMS networks, where they may visit during the lifetime of the ongoing sessions. These locations become the leaves of the multicast tree in our approach. To obtain more efficient use of the scarce wireless bandwidth, our approach allows UEs to temporarily exploit the inactive bandwidths reserved by other UEs in the current IMS/access network. Analytic and simulation models are developed to investigate our resource reservation scheme. The results indicate that our scheme yields comparable performance to that of the previously proposed channel assignment schemes.

IMS-TV: An IMS-based architecture for interactive, personalized IPTV

This article describes a novel architecture for delivering personalized IPTV experiences to end users. The framework leverages the IP Multimedia Subsystem to quickly enable new innovative, multi-media services. We describe the session flows for important use cases, such as accessing the electronic service guide, VoD, fast channel changing, and enhanced parental control services. Important parameters are quantified for the session experience in each of these use cases.

A call‐state‐based service triggering algorithm for IMS network

AbstractTo determine the potential signaling traffic reductions, the session establishment procedures were investigated. The investigation showed that the serving call session control function (S‐CSCF) is the major bottleneck in IP multimedia subsystem (IMS) network and the existing third‐generation partnership project (3GPP) service triggering algorithm (3GPP STA) based on initial filter criteria (iFC) increases largely the end‐to‐end session setup delay (SSD). To reduce the SSD and improve the system performance, a call‐state‐based application triggering architecture (CATA) was proposed. In CATA, the call‐state‐based filter criteria and the call‐state‐based service triggering algorithm (CSTA) were proposed, and then the modeling of 3GPP STA and CSTA was presented. Theoretical analysis and simulation results showed that the CSTA avoids the additional signaling traffic load of the S‐CSCF and application server effectively, which exists in 3GPP STA, reduces the SSD considerably, increases the throughput of the S‐CSCF and improves the quality of service of IMS network. Copyright © 2008 John Wiley & Sons, Ltd.

Reducing Signaling Traffic for the Authentication and Key Agreement Procedure in an IP Multimedia Subsystem

In the IP multimedia subsystem (IMS) of UMTS, two authentication procedures are necessary for IMS subscribers before accessing IMS services: (i) packet-switch domain authentication using the authentication and key agreement of the 3rd Generation Partnership Projects (3GPP AKA), and (ii) IMS authentication using IMS AKA. However, since IMS AKA is based on 3GPP AKA, almost all of the operations are the same. Besides, IMS AKA needs two round-trips to carry out. Therefore, it is inefficient that almost all involved steps in IMS AKA are duplicated. Therefore, we propose a one-pass IMS AKA instead of IMS AKA. The one-pass IMS AKA can keep the security properties of IMS AKA, such as mutual authentication and key agreement. Furthermore, the one-pass IMS AKA not only has at least 45% improvement over IMS AKA in terms of authentication signaling, but also has 76.5% improvement over IMS AKA in terms of storage space.

S3: Smart Session Selection for Voice Communications in Next Generation Wireless Network

Selecting transparently a proper network connection for voice communication will be a fundamental requirement in future multimode heterogeneous wireless network. This paper presented a smart session selection (S3) scheme to meet this requirement. Instead of selecting a best access network as in conventional Always Best Connected (ABC) paradigm, S3 enables users to select a best network connection, which consists of source and destination access network pair, to satisfy quality constraint and users' preference. To support S3, we develop a user profile to specify network connection priority. Meanwhile IP multimedia subsystem (IMS) is extended to make smart decision for users. Finally, Analytic Hierarchy Process (AHP) is used to recommend a network connection with assistance of user profile and IMS signaling. An example is illustrated to show that AHP can successfully select a good network connection that fulfills the requirement of users.