Towards Quality of Experience-aware networks

Rapid service creation stemmed from the convergence of fixed line and mobile telephony with the Internet has made user acceptance to be a crucial factor for the success of the telecommunication business. Telecommunications research, therefore, can no longer be considered only from the pure engineering perspective. Within this paper, we present the concept of service quality for future NGN networks called Quality of Experience QoE, which is different from the wellknown notion of QoS (Quality of Service). We demonstrate an example of the user-centric network design called “QoE-aware IMS-based IPTV network”. The designed IPTV framework allows flexible user tests of IPTV applications, continuous evaluation of service quality from users’ perspective (Quality of Experience QoE), and dynamic system adaptability according to user satisfaction Keywords— QoE, IPTV, IMS I. QUALITY OF EXPERIENCE IN A NGN NETWORK Over the last several years, the world of telecommunications has been undergoing a significant paradigm shift from an engineering discipline of architectures and protocols towards a userand service-oriented business field. The merger of Information, Communication and Entertainment applications has formed “a new I.C.E age”. Similarly, the joint business field of Telecommunications, Information Technology, Media and Entertainment has carved “T.I.M.E” industries [18]. In fact, with the rapid expansion of networked applications and services along with their underlay ICT infrastructures in recent years, service quality and user satisfaction are important research interests for researchers and also competitive factors for service providers, especially in the rich content delivery segment. This is especially manifest in the context of the convergence between fixed-line and mobile telephony with the Internet technology. As an example of a NGN network, recently the IP Multimedia Subsystem (IMS), a 3GPP initiative as a control plane for multimedia services, is a promising candidate for such a convergent Next Generation Network (NGN). IMS provides true convergence of fixed-line telephony, mobile telephony and Internet towards a mobile multimedia platform. From another T.I.M.E aspect, as an instance for a multimedia system, Internet Protocol Television (IPTV) is one of the most exciting new IP-based services, which started from more than 10 years ago, but majorly boosted from the mass deployment of residential IP broadband and the introduction of NextGeneration Networks (NGN). Recently, IMS has been proposed to facilitate modern IPTV networks to provide more flexible service deployment and user control, mobility management with fixed-mobile convergence and seamless integration with other service concepts using SIP signaling like VoIP. Work [6] describes the IMS-based IPTV architecture and its service varieties. IPTV has evolved through various architectures and device capabilities, with its standard being harmonized by ITU-T FG-IPTV group since 2006. IPTV technology its own has been advancing to expand its capabilities as well as to its feature sets to raise the service attractiveness to users. IPTV, as a mixed real-time/on-demand bandwidthexhaustive application, requires a controllable audio/video quality and smooth user interaction. Therefore it raises an important challenge while running on the best-effort, flexible IP networks. The quality problem is more concerned for IMSbased IPTV due to the re-use of IMS functions together with other services and due to new dimensions like mobility and seamless handover. The aforementioned convergence alone does not solve the open question for future killer applications. One of the key success discriminators for future communication services is that they have to provide a satisfying and enjoyable quality experience (QoE) for end customers. Traditionally, the well-established Quality of Service (QoS) metrics and control methods have been thoroughly studied but they only represent the network-centric view and are moving far from being the effective service management components because of the fast-evolving underlying heterogeneous infrastructures while services get converged in the user view (e.g. triple-play, quadruple-play service models...). Nowadays, service quality cannot be taken simply as objective quality parameters of the service. We must also take into consideration every factor that contributes to overall user service perception. The network-centric Quality of Service metrics are not enough to represent the service satisfaction anymore. Consequently, Quality of Experience (QoE) has emerged to be a clear important quality factor, being defined as a user-centric assessment of service expectation and satisfaction and represents the underlying QoS impacts, device capabilities as well as the human perception factors [3][4]. In the quality competition of IP-based service providers, QoE is increasingly critical and tractable to help providers to leverage service quality and user satisfaction while being price-competitive, which is critical in the diversified IP-based service provision competition. Service providers naturally desire to control and ensure a good QoE level while keeping the QoS-related network resources optimized and under control. Unfortunately, most research in the field of networked services so far has primarily focused on these technical QoS aspects of quality, thus lacking sufficient evidence regarding the user’s actual quality perception. In this article, we will describe our work of designing a QoEaware IMS-based IPTV network as well as demonstrate some results as an example of a QoE-aware system. Our aim is to explore the potential links between IMS-based IPTV user experience and the networked service delivery, and to pave the way for service providers to ensure the competitive quality and identify related service optimization approaches. As a matter of fact, QoE for multimedia services including IPTV has already been studied in ITU-T (SG12) to seek the requirements and analysis methods. Research on QoE has contributed from foundation ideas to measurement techniques, from qualitative design concepts to quantitative models to identify QoE properties and their links to lower layers, especially to the network-level QoS as seen from [3] to [15]. However, to the best of our knowledge, study of QoE/QoS correlation in different network/service contexts can be only seen in papers [5][12]. Both works in [5][12] tried to establish a generic function of the QoS/QoE correlation for the video streaming service and made some case studies. But they lack of validating the proposed functions in many other contexts, for example, IMS-based IPTV network context. The remaining of the paper is structured as follows. The next section explains the general QoE-aware IMS-based IPTV architecture. In section III, we describe more in detailed how QoE functionalities are built up in the network prototype and some significant results. The final section is for the conclusion and possible future extension of this topic. II. FRAMEWORK FOR QOE-BASED SERVICE PROVISIONING A. Service Architecture IMS-based IPTV is the next generation IPTV architecture that makes use of the advanced NGN functionalities to provide novel, interactive and blending IPTV services. It can also facilitate QoS guarantee based on the existing IMS service control capabilities. Fig. 1 shows a high-level functional IPTV network architecture being supported by an IMS infrastructure. The model provides multimedia services to the end user by means of the SIP Application Server (SAS). The SAS implements the service logics which users interact and request the movies and/or other online contents in the personalized and intelligent ways. Important logics have been implemented for the special features like enhanced electronic program guide (eEPG), interactive (parental) authorization, blending sessions, etc. SAS interacts with the IPTV Terminal Functionality (IUF) that handles the display and interactivity functions for viewers. SIP (IPTV) Application Server