IP Multimedia Subsystem Architecture Research Articles

An Experimental Evaluation and Characterization of VoIP Over an LTE-A Network

Mobile telecommunications are converging towards all-IP solutions. This is the case of the Long Term Evolution (LTE) technology that, having no circuit-switched bearer to support voice traffic, needs a dedicated VoIP infrastructure, which often relies on the IP Multimedia Subsystem architecture. Most telecom operators implement LTE-A, an advanced version of LTE often marketed as 4G+, which achieves data rate peaks of 300 Mbps. Yet, although such novel technology boosts the access to advanced multimedia contents and services, telco operators continue to consider the VoIP market as the major revenue for their business. In this work, the authors propose a detailed performance assessment of VoIP traffic by carrying out experimental trials across a real LTE-A environment. The experimental campaign consists of two stages. First, we characterize VoIP calls between fixed and mobile terminals, based on a dataset that includes more than 750,000 data-voice packets. We analyze quality-of-service metrics such as round-trip time (RTT) and jitter, to capture the influence of uncontrolled factors that typically appear in real-world settings. In the second stage, we further consider VoIP flows across a range of codecs, looking at the trade-offs between quality and bandwidth consumption. Moreover, we propose a statistical characterization of jitter and RTT (representing the most critical parameters), identifying the optimal approximating distribution, namely the Generalized Extreme Value (GEV). The estimation of parameters through the Maximum Likelihood criterion, leads us to reveal both the short- and long-tail behaviour for jitter and RTT, respectively.

EVALUATION OF SERVICES QUALITY IN IMS

The main stages of the historical development of telecommunication networks are shown. It is noted that today the most common concepts are NGN (Next Generation Network), supporting the functionality of Triple-Play Services (triple services – voice, video and data transmission), as well as IMS (IP Multimedia Subsystem), which combines cellular technology and landline communications. They are able to provide a wide range of services: basic, additional, intelligent. In addition, IMS is able to provide mobile services. The IMS architecture layers are presented – transport layer, control layer; layer of service and application servers. Particular attention is paid to the layer of service and application servers. Based on the analysis of ITU recommendations, the main telecommunication services quality indexes are determined, namely, the time of service provision, the length of the queue that the service request falls into to wait for service on the server, and the probability of refusing to provide services. Based on the proposed mathematical models of the NGN intelligent superstructure, analytical expressions are presented for calculating the quality indexes of intelligent services in NGN for one type of service and for K types of services, taking into account the self-similarity of traffic, and without taking into account. To evaluate the quality of services in IMS, it is proposed to use the approaches of queuing theory and tensor analysis. Tensor analysis offers a mathematical apparatus for transforming coordinate systems, considering IMS as a set of geometric objects whose projections are different in different coordinate systems, but the physical properties of the objects themselves do not change. Expressions are proposed that make it possible to calculate the following QoS indexes in IMS: average queue length, average residence time of an application in the system for all types of services in IMS. It is considered that the incoming traffic is the simplest. Further development of the work is to take into account the self-similar nature of traffic, which is created by the flow of requests for services that come to IMS, as well as the limitations of the server buffer, which will allow a more accurate assessment of the quality of services in IMS.

Impact of Security in QoS Signaling in NGN: Registration Study

New generation networks (NGN) use an IP base to transmit their services as well as voice, video and other services. The IP Multimedia Subsystem (IMS) which represents the network core, allowed controls and accesses into various services through a set of signalling protocols, the most common of which is Session Initiation Protocol (SIP). After securing the most vulnerable interfaces in the core of the NGN: IMS architecture. The idea is to improve QoS in SIP signalling, especially in authentication and registration that represent the first step to access. The proposed approach is used as encryption asymmetry in the SIP registration process and study the performance of the system in terms of QoS parameters.

Providing IPTV in the IMS network

Providing IPTV in the IMS network is increasingly a problem solved today. All households are gradually passing through innovation and slowly every equipment becomes the so-called intelligent or smart and can be connected to a private or public network where it can be monitored, configured, diagnosed and then repaired.. This same upgrading takes place in television, and its current output is in the form of IPTV (Internet Protocol Television) provided in the IP Multimedia Subsystem Network, a new generation network that provides both audio and video data. IMS has originated in 1999 for the 3GPP standard in the 5th edition when switching from a 2G network to a 3G network. It has supported the older GSM and GPRS networks, but also a new UMTS network. In the sixth edition, it also has began to work on WLAN networks, more voice-oriented, or speech recognition services. This paper focuses on the provision of IPTV (Internet Protocol Television) in the IMS (IP Multimedia Subsystem) network. The aim of our paper is to design IPTV services in the IMS network, define the IMS architecture and the IMS network components such as HSS (Home Subscriber Server), various types of CSCF (Call State Control Function), describe the functionality and services provided by IMS and IPTV and, finally, compare the quality of the IPTV service provided by our network and by network of selected operator.

CogIMS: an active service-oriented cognitive networks over IP multimedia subsystems

Cognitive Network (CN) focus on the end-to-end communications for the global optimization and policy enforcement. However, there is a lack of the global control channel or middleware for the cognitive optimization in CN environment. In this paper, we proposed an Active Service-oriented Cognitive IP Multimedia Subsystem framework called CogIMS, which consists of benefits from CN and IP Multimedia Subsystem (IMS). In this active framework, the cognitive optimization is modeled as an active service over IMS architecture. By adopting the proposed active service-oriented framework, the global optimization is simple to achieve under standardized architecture and the computation requirement is reduced from users to core networks. We also simulate wireless users who using active services to compare CogIMS with CN and IMS. The simulation results show that the proposed CogIMS can achieve the optimization of wireless resource allocation with different network situations.

A Novel Secure Framework for Ip Multimedia Subsystem

In complex environments like the IP multimedia Subsystem (IMS), state of the art security solutions cannot always provide satisfactory protection against any type of attack. This paper addresses the security mechanisms utilized by IMS with respect to their susceptibility to SIP based attacks that have been described in the literature. This analysis also studies the effects of 3GPP’s security directions (i.e., IMS architectures) on limiting the attack chances. The protection mechanisms involved are evaluated considering three distinct and crucial factors: (i) whether the attacker is an insider or an external one, (ii) the time frame of the attack and (iii) how these attacks affect the messages’ confidentiality, authenticity and integrity as well as architecture’s availability and users’ privacy. A thorough review of the proposed protection framework is also provided together with an evaluation of the protection level they offer to the IMS architecture.

An IMS Architecture and Algorithm Proposal with QoS Parameters for Flexible Convergent Services with Dynamic Requirements

Quality of Service (QoS) provisioning is one of the main requirements in the 3GPP IP Multimedia Subsystem (IMS) and it has been addressed in different works since the beginning of the IMS standardization process. As a result of the fixed and mobile networks evolution, the parameters standardized in IMS have changed constantly until the specification of the Policy and Charging Control (PCC) architecture that integrates IMS QoS and charging functionalities. However, current IMS QoS specifications still have some limitations to handle service flexibility that is required to provide Internet services over IMS. In this work, we propose an enhanced IMS QoS architecture to support efficient QoS providing for flexible services with dynamic requirements. This proposal is compared against different approaches to evaluate their behavior under network saturation conditions. Simulations results show that the architecture we propose achieves efficiency and flexibility, maintaining the number of blocked and active sessions, and increasing the number of high priority sessions activated in a saturated network.

Performance evaluation of an authentication solution for IMS services access

The IP Multimedia Subsystem (IMS) is an access-independent, IP based, service control architecture. Users' authentication to the IMS takes place through the AKA (Authentication and Key Agreement) protocol, while Generic Bootstrapping Architecture (GBA) is used to authenticate users before accessing the multimedia services over HTTP. In this paper, we focus on the performance analysis of an IMS Service Authentication solution that we proposed and that employs the Identity Based Cryptography (IBC) to personalize each user access. We carry out the implementation of this solution on top of an emulated IMS architecture and evaluate its performance through different clients' access scenarios. Performance results indicate that increase in the number of clients does not influence the average processing time and the average consumed resources of the GBA entities during the authentication. We also notice that the Bootstrapping Server Function (BSF) presents a bottleneck during the service authentication which helps in giving some guidelines for the GBA entities deployment.

Towards Service Sontinuity in IMS Heterogeneous Access Networks

In this paper we tackle the mobility issue in IP Multimedia Subsystem (IMS). Although IMS was designed to integrate different access networks, mobility management among these networks is still unresolved. We propose a novel hybrid mobility management scheme, based on tight cooperation between fast handovers for mobile IPv6 (FMIPv6) and session initiation protocol (SIP) to ensure an uninterrupted real-time service. Moreover, the new Media Independent Handover (MIH) service is integrated into IMS architecture in order to perform intelligent and accurate horizontal and vertical handovers. We investigate two handover cases: selected handover and forced handover. Selected handover takes place when user equipment (UE) is connected to the network via two interfaces at the same time and decides to upgrade the quality of its connection following a given criterion (i.e. cost, bandwidth…etc) without having any difficulty in the previous link. As far as forced handover is concerned, it occurs when the signal reaches a critical level and UE is forced to make a handover in order to maintain the ongoing communication. This case is managed in two phases. The first one or the fast phase is handled by FMIPv6 protocol to preserve as soon as possible packets of the ongoing communication. The second one or the slow phase is handled by SIP protocol to optimize packet delivery route. By doing so, we exploit the benefits of both network layer and application mobility protocols to ensure a continuous session over the two networks without imposing new elements to the network. Through a comparison with other mobility mechanisms, we show in the analytic analysis that our hybrid scheme presents better results in terms of handover latency and packet loss.

Adaptive IPTV services based on a novel IP Multimedia Subsystem

Heterogeneous communication devices are emerging and changing the way of communication. Innovative multimedia applications are now accessible through these embedded systems. The 3GPP IP Multimedia Subsystem (IMS) provides a basic architecture framework for the Next Generation Network (NGN) supporting the convergence platform for service provisioning in heterogeneous networks. ETSI TISPAN standardization effort focuses on delivering IPTV services on such platform. Nevertheless, IPTV on IMS standardization suffers from a lack of efficient user-centric network management mechanisms as the end-user may consume IPTV service from different access networks, on different mobile devices, at anytime. User's Perceived Quality of Service (PQoS) or Quality of Experience (QoE) of IPTV service may also suffer from wireless access network impairments. This paper introduces new functionalities in IPTV over IMS architecture which optimize satisfaction of the end-user and resource utilization of the operator's networks. A context-sensitive User Profile (UP) model is used to deliver IPTV streams adapted to the user's environment. In order to optimize the operator network usage, the impact of spatiotemporal dynamics of the video content on the deduced perceptual quality is considered. A Multimedia Content Management System (MCMS) is proposed to perform dynamic cross-layer adaptation of the IPTV stream based on PQoS measurements at the end-user side.

IMS Application Servers: Roles, Requirements, and Implementation Technologies

The IP multimedia subsystem (IMS) defines a generic architecture to support communication services over a Session Initiation Protocol (SIP) infrastructure. In the IMS architecture, application servers host and execute the IMS service logic. These servers can be SIP application servers, open services architecture (OSA) application servers, or a customized applications for mobile networks using enhanced logic (Camel) service environment. Some technologies used in telephony and voice-over-IP (VoIP) application servers are also applicable to IMS application servers, but such servers have some unique requirements that could limit the extent to which these technologies can meet them.

Real-Time Resource Availability Signaling in IP Multimedia Subsystem Networks

IP Multimedia Subsystem (IMS) allows the use of unlicensed, non-dedicated and nondeterministic access networks for delivering IP multimedia services. Providing end-to-end Quality-of-Service (QoS) for resource demanding real-time services (e.g. real-time multimedia) over such networks is a challenging task due to varying resource availability of the network and the end-device i during a single session ii . A common solution to this problem is adapting service quality and type according to availability of system resources, which requires end-to-end monitoring and signaling of resource availability during a single session. This paper presents an extension of the IMS architecture for real-time resource availability monitoring and signaling. The novelty of the proposed extension is twofold. It takes into account uncontrolled access networks with no resource reservation on the one hand, and end devices on the other. Two system architecture components are introduced for monitoring and signaling of the real-time resource availability in both networks (e.g. bandwidth, buffer space), and end-devices (e.g. battery, CPU, memory, storage), namely a Resource Manager (RM) and a Resource Availability Server (RAS). Our solution does not require any modifications of the IMS architecture and can be implemented as a plug-in.

’Reachability’ in converged IMS services — a BT Alcatel-Lucent collaboration

BT has commenced the switch-over to its 21st Century Network — an all-IP based network which will reduce costs and provide a more ‘innovation-friendly’ platform where exciting new services can be rolled out much more quickly and cost effectively. Increasing computing power and openness on the client device coupled with the move to an IP environment fundamentally alters the competitive landscape for service provision, making it much harder to control the customer’s service experience. Further complexity is introduced by convergence — the requirement for services to run across a multitude of networks and devices. The challenge is to create an infrastructure capable of delivering the exciting new own-build and third-party converged services users want while preserving ease of use and security. The IP multimedia subsystem (IMS) element of the 21CN architecture is a key enabler in reaching these goals. Alcatel-Lucent is a vendor with a strong track-record both in supplying IMS products and in ongoing research activities, considering improvements and extensions to the current IMS standards. This paper summarises activities to date in a research collaboration between BT and Alcatel-Lucent which is looking at the area of improved intelligence in the provision of converged services over an IMS architecture. The collaboration utilises capabilities produced by Alcatel-Lucent’s research department called the Reachability Server to implement a number of novel converged service scenarios. The paper introduces the Reachability Server, describes the collaboration, summarises the scenario implementation work completed to date and presents a number of conclusions and observations.

Dual mode service: Learning from integrating an IP multimedia subsystem service into existing live networks

The IP Multimedia Subsystem (IMS) is an open, standards-based solution for delivering advanced communications services over IP networks. One such service is the dual mode service (DMS), that allows a subscriber to roam across multiple access networks, including Wi-Fi and macro-cellular, using a dual mode handset (DMH). In addition, fixed residential and enterprise numbers receive telephony services through Voice over Internet Protocol (VoIP). The service includes the ability to simultaneously ring multiple endpoints, ring them distinctively for different called numbers, and view logs of all calls. Several deployable architecture options are possible for building DMS, ranging from legacy, circuit switched network solutions through next-generation network solutions using an IMS architecture. Integrating new services and network elements is typically a time consuming and costly endeavor. In this paper, we report our experiences designing, integrating, and deploying a carrier-grade DMS based on an IMS architecture that overcomes many limitations found in other solutions. Our experience with DMS shows that cost and service development time is reduced by leveraging the IMS core's scalability, failover mechanisms, and service provisioning, rather than recreating all these mechanisms in service-specific platforms. © 2007 Alcatel-Lucent.

Improving performance and reliability of an IMS network by co-locating IMS servers

The IP Multimedia Subsystem (IMS) is an architecture for supporting multimedia services via a Session Initiation Protocol (SIP) infrastructure. IMS, specified by the 3rd Generation Partnership Project (3GPP), is increasingly adopted as the reference multimedia network architecture by providers of wireline and wireless infrastructure and associated multimedia application services. One of the characteristics of the IMS architecture is that many different and mandatory SIP proxies are used for each end-to-end SIP session. This may adversely impact the overall IMS call processing performance, which is already affected by the universal usage of SIP. This also makes each end-to-end SIP session dependent on the good functioning of many hosts, which decreases reliability while increasing significantly the end-to-end message latency. This paper analyzes the performance and quantifies the benefits of having the SIP servers running on the same host. It then explains which types of SIP calls in the IMS network can benefit from the co-location of IMS servers and shows how to design the IMS network to maximize IMS server co-location. Finally, it introduces Lucent Technologies' SIPia BUS software architecture, which implements the co-location capability by introducing a new SIP transport in a way that is both natural and non-disruptive for the SIP stack and the SIP user agent.