Pubs:journal

<bibtex> @article{484, author={Frank A. Zdarksy, Sebastian Robitzsch, Albert Banchs}, title={Security Analysis of Wireless Mesh Backhauls for Mobile Networks}, journal={Journal of Network and Computer Applications}, year={2010}, pages={--}, volume={In Press}, abstract={Radio links are used to provide backhaul connectivity for base stations of mobile networks, in cases in which cable-based alternatives are not available and cannot be deployed in an economic or timely manner. While such wireless backhauls have been predominantly used in redundant tree and ring topologies in the past, mobile network operators have become increasingly interested in meshed topologies for carrier-grade wireless backhauls. However, wireless mesh backhauls are potentially more susceptible to security vulnerabilities, given that radio links are more exposed to tampering and given their higher system complexity.

This article extends prior security threat analyses of 3rd generation mobile network architectures for the case of wireless mesh backhauls. It presents a description of the security model for the considered architecture and provides a list of the basic assumptions, security objectives, assets to be protected and actors of the analysis. On this foundation, potential security threats are analyzed and discussed and then assessed for their corresponding risk. The result of this risk assessment is then used to define a set of security requirements. Finally, we give some recommendations for wireless mesh backhaul designs and implementations following these requirements.}, keywords={Security analysis, Wireless mesh backhauls, Mobile networks}, pdf={2010 - Zdarsky, Robitzsch, Banchs.pdf}, } </bibtex> <bibtex> @article{244, author={Seung-Bum Lee;Gabriel-Miro Muntean;Alan F. Smeaton}, title={Performance-aware Replication of Distributed Pre-recorded IPTV Content}, journal={IEEE Transactions on Broadcasting Special Issue}, year={2009}, pages={-}, volume={(in press)}, abstract={Video recording in IPTV systems is a promising service that provides time-shifted services in relation to storing TV content closer to user devices such as set-top boxes. Existing approaches do not support collaboration between nodes which have correlated contents, a fact that can affect the performance of the overall system. To make this service more interactive and proactive, this paper presents the architecture using the Smart Personal Information Network (Smart PIN) as a novel performance-based content sharing network for IPTV content which uses a user-centric utility-based Multimedia Data Replication Scheme (MDRS). This allows the exchange of data based on both network performance and user interest in exchanged multimedia content in order to achieve ef?cient content sharing. The proposed solution is evaluated through extensive simulations and results show much improved behaviour in comparison with two other existing general purpose data replicat on schemes.}, keywords={IPTV, Data replication, Content management, Peer-to-peer}, } </bibtex> <bibtex> @article{253, author={Bogdan Ciubotaru; Gabriel-Miro Muntean}, title={SASHA - A Quality-Oriented Handover Algorithm for Multimedia Content Delivery to Mobile Users}, journal={IEEE Transactions on Broadcasting Special Issue}, year={2009}, pages={-}, volume={(in press)}, abstract={The convergence of the existing network access technologies to a common IP-based architecture and the increase in popularity of accessing video content over the Internet makes IPTV a promising solution for media and entertainment industries. Additionally, video content delivery to the increasingly popular mobile devices over heterogeneous wireless networks makes IPTV even more appealing. However the distribution of multimedia content over heterogeneous wireless networks to mobile devices involves significant technical challenges related to mobility management and quality of service provisioning. The existing solutions do not consider quality of service as a decision making parameter for mobility management in general and handover management in particular. This paper proposes the Smooth Adaptive Soft Handover Algorithm (SASHA), a novel quality-aware approach to handover based on load balancing among different networks using a comprehensive, Quality of Multimedia Streaming (QMS), function for decision making. SASHA represents the handover management solution at the core of the more comprehensive Multimedia Mobility Management System (M3S), a quality oriented mobility management framework for multimedia applications which maximizes user perceived quality by efficiently exploiting all available communication resources. Simulation-based testing results are presented, outlining the performance of SASHA in different mobility scenarios. The evaluation is performed for different number of nodes performing handover simultaneous and for various situations in terms of networks’ overlapping area. The results shown indicate how SASHA outperforms other three mobility management solutions in terms of quality, scalability and resilience to the dynamics of the networks’ overlapping area. }, keywords={Multimedia streaming, IPTV, Heterogeneous networks, Mobility, Handover}, pdf={Ciubotaru_Muntean_IPTV.pdf}, } </bibtex> <bibtex> @article{338, author={Fitzpatrick,J.;Murphy,S.;Atiauzzaman,M.;Murphy,J.}, title={Using Cross-Layer Metrics to Improve the Performance of End-to-End Handover Mechanisms}, journal={Computer Communication Preprint Online}, year={2009}, pages={13 Pages}, volume={10.1016}, abstract={Network centric handover solutions for all IP wireless networks usually require modifications to network infrastructure which can stifle any potential rollout. This has led researchers to begin looking at alterna- tive approaches. Endpoint centric handover solutions do not require network infrastructure modification, thereby alleviating a large barrier to deployment. Current endpoint centric solutions capable of meeting the delay requirements of Voice over Internet Protocol (VoIP) fail to consider the Quality of Service (QoS) that will be achieved after handoff. The main contribution of this paper is to demonstrate that QoS aware handover mechanisms which do not require network support are possible. This work proposes a Stream Control Transmission Protocol (SCTP) based handover solution for VoIP called Endpoint Centric Handover (ECHO). ECHO incorporates cross-layer metrics and the ITU-T E-Model for voice quality assessment to accurately estimate the QoS of candidate handover networks, thus facilitating a more intelligent handoff decision. An experimental testbed was developed to analyse the performance of the ECHO scheme. Results are presented showing both the accuracy of ECHO at estimating the QoS and that the addition of the QoS capabilities significantly improves the handover decisions that are made.}, keywords={Echo,SCTP,VoIP,E-Model,Sigma}, pdf={using cross.pdf}, } </bibtex> <bibtex> @article{339, author={Qiao,Y.;Fallon,E.;Murphy,L.;Murphy,J.;Hanley,A.;Shi,Z.}, title={Transmission Scheduling for Multihomed Transport Protocols with Network Failure Tolerance}, journal={Telecommunication Systems Journal}, year={2009}, pages={10 pages}, volume={40}, abstract={In heterogeneous network environments, the network connections of a multi-homed device may have significant bandwidth differential. For a multihomed transmission protocol designed for network failure tolerance, such as SCTP, path selection algorithms for data transmission drastically affect performance. This article studies the effect of path bandwidth differential on the performance of retransmission strategies in multi-homing environments. It identifies that fast retransmission on an alternate path may cause receive buffer blocking when path bandwidth differential is significant and the receive buffer is limited. A theoretical model is proposed for selecting retransmission path during the fast retransmission phase, based on receive buffer and path conditions. From these observations and analysis results, this article proposes that path selection strategies for transmitting new data and retransmitted data should be decoupled. A new path selection scheme is proposed and evaluated through SCTP simulations.}, keywords={Multi-homing, Transmission Protocol, SCTP}, pdf={transmission.pdf}, } </bibtex> <bibtex> @article{408, author={C.H.Muntean;Gabriel-Miro Muntean}, title={Open Corpus Architecture for Personalised Ubiquitous e-Learning}, journal={Personal & Ubiquitous Computing }, year={2009}, pages={197-205}, volume={13}, abstract={As the e-learning area matures, there are a growing number of e-learning content providers that produce and distribute material that covers a large range of topics, differs in quality and is represented in various formats. Lately, different devices and various network technologies allow extensive user access to educational content almost anywhere, anytime and from any device. Ubiquitous e-learning has the potential to provide continuous and context-based, educational material to human learners anytime, anywhere and on any device. Since each person has different expectations related to the content, the performance of the delivery and display of that content, it is desirable for an ubiquitous e-learning environment to provide user-oriented personalisation of e-learning material. However very often there are multiple sources of e-learning material at various web locations (open corpus resources) that cover the same topic, but differ in terms of quality, formatting and even cost. It is very difficult for learners to select the content that best suits their interests and goals, characteristics of the device used and delivery network as well as their cost budget. This paper proposes an innovative ubiquitous e-learning environment called Performance-based E-learning Adaptive Cost-efficient Open Corpus frameworK (PEACOCK) that provides support for the selection and distribution of personalised e-learning rich media content (e.g. multimedia, pictures, graphics and text) to e-learners such as it will best suit users’ interests and goals, meet their formatting preferences and cost constraints, while considering the limitations introduced by the end-user devices and the delivery networks to the user. PEACOCK’s main goal is to maximise the users’ e-learning experience and increase their learning satisfaction and learning outcome. }, keywords={Adaptive e-learning systems - User-oriented personalisation - Cost-efficiency - Ubiquitous e-learning environment }, pdf={open corpus.pdf}, } </bibtex> <bibtex> @article{456, author={C.Xu;Gabriel-Miro Muntean;E.Fallon;A.Hanley}, title={Distributed Storage-Assisted Data-Driven Overlay Network for P2P VoD Services}, journal={IEEE Trans. on Broadcasting}, year={2009}, pages={1-10}, volume={55}, abstract={Providing VCR-like operations in Peer-to-Peer (P2P) environments is a significant challenge. This paper proposes a distributed Storage-assisted Data-driven overlay Network (SDNet) to support P2P Video-on-Demand (VoD) services. It integrates two networks: a Data-driven Overlay Network (DONet) and a multi-way tree. DONet is enhanced and used for the routine video distribution based on the buffer overlapping mechanism and gossip protocol. A novel algorithm which uses a multi-way tree structure and extra pre-fetching buffers at the nodes is proposed to support efficient VoD operations. Videos are divided into uniform segments, pre-fetched and stored in a distributed manner along the tree topology. The cooperation between DONet-based video delivery and the tree-located multimedia components enable multimedia streaming interactive commands to be performed efficiently. This paper presents and discusses the structure of SDNet and the distributed storage scheme and details the cooperation procedure. Simulation-based testing results show how the proposed SDNet is an efficient interactive streaming solution in a P2P environment.}, keywords={DONet, multi-way tree, P2P VoD, VCR-like.}, pdf={distributed.pdf}, } </bibtex> <bibtex> @article{475, author={Arturo Azcorra; Thomas Banniza; David Chieng; John Fitzpatrick; Dirk von-Hugo; Marek Natkaniec; Sebastian Robitzsch; Frank Zdarsky}, title={Supporting carrier grade services over wireless mesh networks: The approach of the European FP-7 STREP CARMEN [Very Large Projects]}, journal={IEEE Communications Magazine}, year={2009}, pages={14-16}, volume={47}, abstract={CARMEN is a three-year Specific Targeted Research Project (STREP) funded by the European Commission within the 7th Framework Program. The CARMEN access network will complement existing access technologies by exploiting low cost mesh networking techniques, thus minimizing deployment and maintenance costs. The CARMEN architecture introduces an abstraction layer that hides the specifics of the underlying access technology providing an abstract interface on top of which higher layers can be easily developed. This allows for the integration of current and future heterogeneous wireless technologies to provide scalable and efficient mobile ubiquitous Internet access, able to adapt to different environments and user requirements. Following these goals, CARMEN aims to define, study and implement link and technology abstractions, mobility support, and quality of service. The architecture also includes advanced monitoring features that allow for dynamic self-configuration, thereby reducing the installation and operational costs.}, keywords={CARMEN, Specific Targeted Research Project, carrier grade services, metropolitan areas, wireless mesh networks }, } </bibtex> <bibtex> @article{220, author={A. Nafaa; S. Murphy; L. Murphy}, title={Analysis of a Large-Scale VOD Architecture for Broadband Operators: A P2P-Based Solution}, journal={IEEE Communications Magazine}, year={2008}, pages={47-55}, volume={46}, abstract={VOD services distribution is gaining unprecedented interest from the consumer communication industry due to its growing success in both the Internet and residential broadband market. In this article we present a scalable VOD distribution architecture for broadband operators. The solution is based on a P2P streaming concept in which a VOD streaming session requested by a given STB (Set-Top-Box) is actually provisioned via a multisource streaming session. This solution has the advantage of scaling naturally with the number of STBs in the network. In this article we focus on efficiently translating the popularity distribution into content availability in the network. Different aspects related to this issue are analyzed and challenges highlighted. }, keywords={video on demand, peer-to-peer, popularity distribution, content availability}, } </bibtex> <bibtex> @article{221, author={Y. Qiao; E. Fallon; J. Murphy; L. Murphy; X. Zhu; G. Hayes; A. Matthews; A. Hanley}, title={Performance Analysis of Multi-homed Transport Protocols with Network Failure Tolerance}, journal={IET Communications}, year={2008}, pages={336-345}, volume={2}, abstract={This paper studies the performance of multi-homed transport protocols tolerant of network failure. It evaluates the performance of different retransmission policies combined with path failure detection thresholds, infinite or finite receive buffers for various path bandwidths, delays and loss rate conditions through SCTP simulation. The results show that retransmission policies perform differently with different path failure detection threshold configurations. It identifies that retransmission of all data on an alternate path with the path failure detection threshold set to zero performs best in symmetric path conditions but its performance degrades acutely in asymmetric path conditions even when the alternate path delay is shorter than the primary path delay. It illustrates that retransmission of all data on the same path with the path failure detection threshold set to one or zero gives the most stable performance in all path configurations. }, keywords={Fault-tolerant computing, transport protocols}, pdf={performance analysis.pdf}, } </bibtex> <bibtex> @article{222, author={A. Nafaa; T. Taleb; L. Murphy}, title={Forward Error Correction Strategies for Media Streaming over Wireless Networks}, journal={IEEE Communications Magazine}, year={2008}, pages={72-79}, volume={46}, abstract={The success of next-generation mobile communication systems depends on the ability of service providers to engineer new added-value multimedia-rich services, which impose stringent constraints on the underlying delivery/transport architecture. The reliability of real-time services is essential for the viability of any such service offering. The sporadic packet loss typical of wireless channels can be addressed using appropriate techniques such as the widely-used packet-level Forward Error Correction. In designing channel-aware media streaming applications, two interrelated and challenging issues should be tackled: accuracy of characterizing channel fluctuations and effectiveness of application-level adaptation. The first challenge requires thorough insight into channel fluctuations and their manifestations at the application level, while the second concerns the way those fluctuations are interpreted and dealt with by adaptive mechanisms such as FEC. In this article we review the major issues that arise when designing a reliable media streaming system for wireless networks. }, keywords={Forward error correction, multimedia streaming, wireless channel conditions}, } </bibtex> <bibtex> @article{334, author={Trofin,M.;Murphy,J.}, title={Static Verification of Component Composition in Contextual Composition Frameworks}, journal={International Journal on Software Tools for Technology Transfers}, year={2008}, pages={247-261(15 pages)}, volume={10(3)}, abstract={Contextual component frameworks, such as Enterprise JavaBeans (EJB), allow for components to specify boundary conditions for the runtime context. These conditions are satisfied at runtime by services of the underlying platform, thus ensuring that the context in which components run exhibits properties that allow them to operate correctly. Depending on how components call each other, it is possible that satisfying such conditions lead to problems such as reduced performance due to redundant service execution, or permanent errors (composition mismatches), due to incompatible boundary conditions. Currently, the semantics of these boundary conditions are expressed in natural language only, making it impossible to incorporate them into an automatic analysis tool. Furthermore, early understanding of how components call each other would be necessary, but it is currently difficult to achieve by means of a tool, as the method dispatch rules in a component system differ from the dispatch rules of the programming language(s) in which they were developed. We have developed a metamodel, $${\mathbb{M}}$$ , for describing boundary conditions, an analysis method, $${\mathbb{A}}$$ , and a static component-level call graph extraction method for EJB applications, CHA EJB . $${\mathbb{A}}$$ uses $${\mathbb{M}}$$ models to analyze inter-component call graphs, and thus detect problems such as composition mismatches or redundancies, thus allowing for remedial action to take place. We present $${\mathbb{M}},{\mathbb{A}}$$ and CHA EJB in this article, show that $${\mathbb{A}}$$ produces correct results, and describe a prototype analysis tool implementing the three, which we used to validate our approach on two popular EJB applications. }, keywords={Software components - Contextual composition - Static analysis - Enterprise Java }, pdf={static verification.pdf}, } </bibtex> <bibtex> @article{336, author={Parsons,T.;Murphy,J.}, title={Detecting Performance Antipatterns in Component Based Enterprise Systems}, journal={Journal of Optical Technology}, year={2008}, pages={55-90(36 pages)}, volume={7(3)}, abstract={We introduce an approach for automatic detection of performance antipatterns. The approach is based on a number of advanced monitoring and analysis techniques. The advanced analysis is used to identify relationships and patterns in the monitored data. This information is subsequently used to reconstruct a design model of the underlying system, which is loaded into a rule engine in order to identify predefined antipatterns. We give results of applying this approach to identify a number of antipatterns in two JEE applications. Finally, this work also categorises JEE antipatterns into categories based on the data needed to detect them.}, keywords={Component Systems,Antipatterns}, pdf={detecting performance.pdf}, } </bibtex> <bibtex> @article{405, author={O.Ashagi;S.Murphy;L.Murphy}, title={Interference Mitigation in License-exempt 802.16 systems:a distributed approach}, journal={Unlicensed Mobile Access Technology}, year={2008}, pages={49-50}, volume={August }, abstract={Operating in license-exempt IEEE 802.16 wireless spectrum is a challenging research issue. The research focus is on deriving intelligent algorithms to mitigate the interference that occurs between different users. In this chapter, we propose an enhancement to our previously published distributed approach to mitigate interference between 802.16 systems operating in close proximity, by introducing a re-listening mechanism to determine whether there are more subcarriers available in the channel than what the base stations (BSs) are currently using. Simulation results show that the re-listening mechanism offers a 100 percent throughput increase for some BSs. Our results also show the general trend of throughput variations between the downlink and the uplink, due to the differences in transmission power.}, keywords={IEEE 802.16,}, pdf={interference.pdf}, } </bibtex> <bibtex> @article{425, author={C.H.Muntean}, title={Improving Learner Quality of Experience by Content Adaptation based on Network Conditions}, journal={Computers in Human Behaviour}, year={2008}, pages={1452-1472}, volume={24}, abstract={Apart from user characteristics, properties of the network over which the content is delivered and device on which the content is displayed affect end-user perceived quality. This paper presents a learner quality of experience (QoE) model that apart from the user-related content adaptation, considers delivery performance-based content personalisation in order to improve user experience when interacting with an online learning system. A comparison-based study on the benefit of using the proposed learner QoE model in adaptive and personalized education was conducted involving the original AHA! and QoEAHA – a version of AHA! enhanced with the learner QoE model. Testing results demonstrate significant benefits in terms of learning achievement, learning performance, learner navigation and user QoE in favour of the learner QoE model-enhanced solution.}, keywords={QoE}, pdf={Muntean_2008_Computers-in-Human-Behavior.pdf}, } </bibtex> <bibtex> @article{453, author={C.H.Muntean;Gabriel-Miro Muntean}, title={Open Corpus Architecture for Personalised Ubiquitous e-Learning}, journal={Personal & Ubiquitous Computing}, year={2008}, pages={197-205}, volume={13}, abstract={As the e-learning area matures, there are a growing number of e-learning content providers that produce and distribute material that covers a large range of topics, differs in quality and is represented in various formats. Lately, different devices and various network technologies allow extensive user access to educational content almost anywhere, anytime and from any device. Ubiquitous e-learning has the potential to provide continuous and context-based, educational material to human learners anytime, anywhere and on any device. Since each person has different expectations related to the content, the performance of the delivery and display of that content, it is desirable for an ubiquitous e-learning environment to provide user-oriented personalisation of e-learning material. However very often there are multiple sources of e-learning material at various web locations (open corpus resources) that cover the same topic, but differ in terms of quality, formatting and even cost. It is very difficult for learners to select the content that best suits their interests and goals, characteristics of the device used and delivery network as well as their cost budget. This paper proposes an innovative ubiquitous e-learning environment called Performance-based E-learning Adaptive Cost-efficient Open Corpus frameworK (PEACOCK) that provides support for the selection and distribution of personalised e-learning rich media content (e.g. multimedia, pictures, graphics and text) to e-learners such as it will best suit users’ interests and goals, meet their formatting preferences and cost constraints, while considering the limitations introduced by the end-user devices and the delivery networks to the user. PEACOCK’s main goal is to maximise the users’ e-learning experience and increase their learning satisfaction and learning outcome.}, keywords={Adaptive e-learning systems �}, pdf={open corpus.pdf}, } </bibtex> <bibtex> @article{454, author={Gabriel-Miro Muntean;G.Ghinea;T.N.Sheehan}, title={Region of Interest-based Adaptive Multimedia Streaming Scheme}, journal={IEEE Trans. on Broadcasting}, year={2008}, pages={296-303}, volume={54}, abstract={Adaptive multimedia streaming aims at adjusting the transmitted content based on the available bandwidth such as losses that often severely affect the end-user perceived quality are minimized and consequently the transmission quality increases. Current solutions affect equally the whole viewing area of the multimedia frames, despite research showing that there are regions on which the viewers are more interested in than on others. This paper presents a novel region of interest-based adaptive scheme (ROIAS) for multimedia streaming that when performing transmission-related quality adjustments, selectively affects the quality of those regions of the image the viewers are the least interested in. As the quality of the regions the viewers are the most interested in will not change (or will involve little change), the proposed scheme provides higher overall end-user perceived quality than any of the existing adaptive solutions.}, keywords={Content adaptation, multimedia streaming,}, pdf={region.pdf}, } </bibtex> <bibtex> @article{455, author={Gabriel-Miro Muntean;G.Ghinea;P.Frossard;M.Etoh;F.Speranza;H.R.Wu}, title={Advanced Solutions for Quality-Oriented Multimedia Broadcasting}, journal={IEEE Trans. on Broadcasting}, year={2008}, pages={494-498}, volume={54}, abstract={Multimedia content is increasingly being delivered via different types of networks to viewers in a variety of locations and contexts using a variety of devices. The ubiquitous nature of multimedia services comes at a cost, however. The successful delivery of multimedia services will require overcoming numerous technological challenges many of which have a direct effect on the quality of the multimedia experience. For example, due to dynamically changing requirements and networking conditions, the delivery of multimedia content has traditionally adopted a best effort approach. However, this approach has often led to the end-user perceived quality of multimedia-based services being negatively affected. Yet the quality of multimedia content is a vital issue for the continued acceptance and proliferation of these services. Indeed, end-users are becoming increasingly quality-aware in their expectations of multimedia experience and demand an ever-widening spectrum of rich multimedia-based services.}, keywords={Multimedia,Network}, pdf={advanced solution.pdf}, } </bibtex> <bibtex> @article{399, author={T.Taleb;A.Nafaa;L.Murphy;K.Hashimoto;N.Kato;Y.Nemoto}, title={Towards Efficient Service-Level QoS Provisioning in Large Scale 802.11-Based Networks}, journal={IEEE Network:Special Issue on Advances in Broadband Access Networks}, year={2007}, pages={42-48}, volume={21}, abstract={Along with recent advances in mobile networking and portable computing technologies, there is a trend in the telecommunications industry toward the development of efficient ubiquitous systems that can provide a set of bandwidth-intensive and real-time services to multiple users while supporting their full mobility. Largescale deployment of 802.11-based technologies will play an integral part in the construction of such ubiquitous wireless mobile systems. A challenging task in the development of such networks is efficient provisioning of QoS-enabled services for mobile users. In this context, we propose a scheme that constantly monitors the overall network performance to perform admission control and traffic conditioning at the 802.11-based access points and mobile terminals. The focus is on servicelevel fairness, where different flows from the same traffic class can still receive the same QoS level even if they have different bit rates. Furthermore, given the mobility of users, the success of any resource allocation and admission control model depends on the continuity of QoS guarantees across different WLANs. This article proposes a dynamic service level agreement negotiation protocol that allows mobile terminals to perform handoffs between different WLANs while maintaining the agreed level of service. End users also can change their service levels in response to changes in network conditions.}, keywords={Internet,802.11,Wireless Mobile,QoS}, pdf={toward efficient.pdf}, } </bibtex> <bibtex> @article{403, author={G.Muntean;P.Perry;L.Murphy}, title={A Comparison Based Study of Quality Oriented Video on Demand}, journal={IEEE Transactions on Broadcasting}, year={2007}, pages={92-102}, volume={53}, abstract={The Quality Oriented Adaptation Scheme (QOAS) is used for high bit-rate multimedia streaming in local broadband multi-service all-IP networks. It balances two opposing goals: providing high quality multimedia-based services to end-users, and increasing the infrastructure utilisation and number of customers simultaneously served. Extensive objective testing results presented in this paper show that QOAS achieves high performance in terms of end-user perceived quality, loss rate, throughput, link utilisation, and number of customers simultaneously served. These results were obtained even in highly loaded and variable delivery conditions caused by traffic of different types, sizes, and variation patterns. QOAS performance was assessed stand-alone and in comparison with other existing solutions, adaptive and non-adaptive.}, keywords={Adaptive video streaming, feedback control, grading scheme, end-user perceived quality.}, pdf={a comparison.pdf}, } </bibtex> <bibtex> @article{409, author={C.H.Muntean;G.M.Muntean;J.McManis;A.I.Cristea}, title={Quality of Experience-LAOS:Create Once,Use Many,Use Anywhere}, journal={International Journal of Learning Technology}, year={2007}, pages={209-229}, volume={3}, abstract={This paper proposes QoE-LAOS, a Quality of Experience-oriented adaptive authoring model that enables performance-aware adaptation. It extends the existing LAOS authoring model in order to consider display and delivery performance issues. QoE-LAOS involves the addition of three new QoE sublayers: QoE Content Features sublayer, QoE Characteristics sublayer and QoE Rules sublayer. These proposed QoE sublayers are deployed at LAOS's Domain, Adaptation and Presentation Models, respectively. This paper formalises and exemplifies QoE-LAOS and discusses authoring-related issues in relation to each new sublayer. }, keywords={adaptive hypermedia, adaptive educational hypermedia, AEH, adaptive author assistance, semi-automatic adding, authoring models, authoring tools, adaptive web application engineering, adaptive web application authoring, adaptive learning, adaptive systems,}, pdf={quality of experience.pdf}, } </bibtex> <bibtex> @article{396, author={N.Cranley;L.Murphy}, title={Incorporating User Perception in Adaptive Video Streaming Systems}, journal={Digital Multimedia Perception & Design}, year={2006}, pages={860-861}, volume={May 2006}, abstract={There is an increasing demand for streaming video applications over both the fixed Internet and wireless IP networks. The fluctuating bandwidth and time-varying delays of best-effort networks makes providing good quality streaming a challenge. Many adaptive video delivery mechanisms have been proposed over recent years; however, most do not explicitly consider user-perceived quality when making adaptations, nor do they define what quality is. This chapter describes research that proposes that an optimal adaptation trajectory through the set of possible encodings exists, and indicates how to adapt transmission in response to changes in network conditions in order to maximize user-perceived quality.}, keywords={Video Streaming,Internet,IP Networks}, pdf={incorporating.pdf}, } </bibtex> <bibtex> @article{410, author={C.H.Muntean;J.McManis}, title={End-User Quality of Experience Oriented Adaptive E-learning System}, journal={Journal of Digital Information}, year={2006}, pages={1}, volume={7}, abstract={In the context of new devices and with a variety of network technologies that allow access to the Internet, the providers of e-learning materials have to ensure that the users have a positive experience using their e-learning systems and they are happy to re-use them. Adaptive Hypermedia research aims to provide personalised educational material that ensures a positive learning experience for the end-users. However, user experience is dependent not only on the content served to them, but also on the user perceived performance of the e-learning system. This leads to a new dimension of individual differences between Web users: the end-user Quality of Experience (QoE). We have proposed a solution for Adaptive Hypermedia Systems (AHS) that provides satisfactory end-user QoE through the use of a new QoE layer. This layer attempts to take into account multiple factors affecting QoE in relation to the delivery of a wide range of Web components such as text, images, video, audio.

The effectiveness of our QoE layer has been tested in comparison to a standard educational AHS and the results of these tests are presented in this paper. Different educational-based evaluation techniques such as learner achievement analysis, learning performance assessment, usability survey and correlation analysis between individual student performance and judgment on system usability were applied in order to fully assess the performance of the proposed QoE layer. Results of the tests showed that the use of the QoE layer brought significant improvements in terms of user learning performance, system usability and user satisfaction with the personalised e-learning system while not affecting the user learning achievement }, keywords={end-user QoE, adaptive hypermedia, e-learning, end-user perceived performance, learning performance }, pdf={end user quality.doc}, } </bibtex> <bibtex> @article{419, author={N.Cranley;P.Perry;L.Murphy}, title={User Perception of Adapting Video Quality}, journal={International Journal of Human-Computer Studies/Knowledge Acquisition}, year={2006}, pages={637-647}, volume={64}, abstract={In general, video quality adaptation and video quality evaluation are distinct activities. Most adaptive delivery mechanisms for streaming multimedia content do not explicitly consider user-perceived quality when making adaptation decisions. Equally, video quality evaluation techniques are not designed to evaluate instantaneous quality where the quality is changing over time. We propose that an Optimal Adaptation Trajectory (OAT) through the set of possible encoding exists, and that it indicates how to adapt encoding quality in response to changes in network conditions in order to maximize user-perceived quality. The subjective and objective tests carried out to find such trajectories for a number of different MPEG-4 video clips are described. Experimental subjective testing results are presented that demonstrate the dynamic nature of user perception with adapting multimedia. The results demonstrate that adaptation using the OAT out-performs conventional adaptation strategies in which only a single aspect of the video quality is adapted. In contrast, the OAT provides a mechanism to adapt multiple aspects of the video quality thereby giving better user-perceived quality in both the short and long term.}, keywords={Video quality; Evaluation/methodology; Perception; Subjective and objective quality; Adaptation}, pdf={user perception.pdf}, } </bibtex> <bibtex> @article{420, author={N.Cranley;L.Murphy;P.Perry}, title={Dynamic Content-Based Adaptation of Streamed Multimedia,Intelligence-based Adaptation for Ubiquitous Multimedia Communications}, journal={Journal of Network & Computer Applications}, year={2006}, pages={983-1006}, volume={30}, abstract={Most adaptive delivery mechanisms for streaming multimedia content do not explicitly consider user-perceived quality when making adaptation decisions. We show that an optimal adaptation trajectory (OAT) through the set of possible encodings exists, and that it indicates how to adapt encoding quality in response to changes in network conditions in order to maximise user-perceived quality. The OAT is related to the characteristics of the content, in terms of spatial and temporal complexity. We describe a method to automatically determine the OAT in response to the time-varying characteristics of the content. In this way, as the characteristics of the content change over time, the system can dynamically and intelligently adjust the adaptation process in order to maximise the user-perceived quality. The OAT can be used with any sender-based transmission adaptation policy. We demonstrate content-based adaptation using the OAT in a practical system using two different adaptation algorithms. Furthermore, we show how this form of adaptation can result in differing adaptation behaviour not only as a result of the dynamics of the content but also as a result of the adaptation algorithm being used. Finally, we show how increased feedback frequency does not necessarily improve the behaviour of the adaptation algorithm being used.}, keywords={User perception; Video quality; Adaptive systems; Multimedia}, pdf={dynamic.pdf}, } </bibtex> <bibtex> @article{300, author={Brebner,P.; Cecchet,E.; Marguerite,J.; Tuma,P.; Ciuhandu,O.; Dufour,B.; Eeckhout,L.; Frenot,S.; Krishna,A.S.; Murphy,J.; Verbrugge,C.}, title={Middleware Benchmarking: Approaches, Results, Experiences,}, journal={Concurrency & Computation-Practice & Experience}, year={2005}, pages={1799-1805(7 pages)}, volume={17(15)}, abstract={The report summarizes the results of the Workshop on Middleware Benchmarking held during OOPSLA 2003. The goal of the workshop was to help advance the current practice of gathering performance characteristics of middleware implementations through benchmarking. The participants of the workshop have focused on identifying requirements of and obstacles to middleware benchmarking and forming a position on the related issues. Selected requirements and obstacles are presented, together with guidelines to adhere to when benchmarking, open issues of current practice, and perspectives on further research}, keywords={middleware benchmarking; middleware performance; middleware scalability; middleware evaluation; middleware benchmark design; benchmarking guidelines; benchmarking measurement; benchmarking metrics; OOPSLA 2003 workshop}, pdf={middleware benchmarking.pdf}, } </bibtex> <bibtex> @article{308, author={Klusek,B.;Murphy,J.;Barry,L.P.}, title={New Fiber Delay Line Usage Strategy in Optical Burst Switching Networks}, journal={Networks & Communication Systems}, year={2005}, pages={5 Pages}, volume={NCS 2005}, abstract={Optical Burst Switching (OBS) is a new paradigm for future all-optical networks. In an OBS node, a Fiber Delay Line may be used to delay a burst, effectively increasing its offset time. Traditionally, FDLs were used in contention resolution, i.e. a burst was only buffered if it would otherwise been dropped. We propose a different approach, where delay lines are used also to better arrange bursts in time. In our strategy both outgoing channels and FDL channels are assigned a price, according to their suitability for a particular burst. When a control packet arrives at a core node, all the possible ways of handling the corresponding burst are found (the outgoing channel, with or without a FDL), and the one with a lowest total price is chosen. This makes it possible to use most FDL channels for the majority of the time, reducing the probability of future contention. We present simulation results, showing how node performance depends on the size of a FDL bank, using either Last Available Unused Channel with Void Filling (LAUC-VF) and the traditional FDL usage strategy or our algorithm.}, keywords={High-speed Internet, Optical Burst Switching, Fiber Delay Lines, burst scheduling}, pdf={new fiber.pdf}, } </bibtex> <bibtex> @article{380, author={G.Muntean;P.Perry;L.Murphy}, title={Subjective Assessment of the Quality-Oriented Adaptive Scheme}, journal={IEEE Transactions on Broadcasting}, year={2005}, pages={276-286}, volume={51}, abstract={The Quality-Oriented Adaptation Scheme (QOAS) supports the distribution of high quality multimedia services to a large number of simultaneous customers via given broadband IP infrastructure. This paper presents subjective testing results that augment previously reported objective performance assessment. Clips representing different classes of multimedia sequences in terms of motion content and types were selected and streamed using a QOAS-based prototype system. Congested delivery network conditions were emulated and the effects of the consequent QOAS-driven adaptations were subjectively assessed by end-users. The test subjects have also graded their perceived quality when using a nonadaptive streaming approach. The QOAS-related results were much higher than those obtained for a nonadaptive approach, being above the “good” perceptual level for all multimedia clips and in all tested delivery conditions.}, keywords={Adaptive multimedia streaming, end-user perceived quality, feedback control, subjective testing.}, pdf={subjective.pdf}, } </bibtex> <bibtex> @article{382, author={N.Cranley;P.Perry;L.Murphy}, title={Optium Adaptation Trajectories for Streamed Multimedia}, journal={ACM Multimedia Systems }, year={2005}, pages={392-401}, volume={10}, abstract={Most adaptive delivery mechanisms for streaming multimedia content do not explicitly consider user-perceived quality when making adaptations. We propose that an optimal adaptation trajectory through the set of possible encodings exists and that it indicates how to adapt encoding quality in response to changes in network conditions to maximize user-perceived quality. Such an optimum adaptation trajectory can be used with any transmission adaptation policy. We describe the subjective tests we carried out to find such trajectories for a number of different MPEG-4 video clips and indicate how this knowledge could be used in the operation of a practical system.}, keywords={Perceptual video quality · Adaptive multimedia transmission · Subjective testing · Video encoding}, pdf={optium adaptation.pdf}, } </bibtex> <bibtex> @article{383, author={M.Narbutt;A.Kelly;L.Murphy;P.Perry}, title={Adaptive VoIP playout Scheduling :A new method for assesing user satisfaction}, journal={IEEE Internet Computing}, year={2005}, pages={28-34}, volume={July 2005}, abstract={Delay and packet loss dramatically affect the quality of a voice-over-IP (VoIP) call and depend on the playout buffer scheme implemented at the receiver. The choice of playout algorithm can’t be based on statistical metrics without considering the perceived end-to-end conversational speech quality. The authors present a method for evaluating various playout algorithms that extends the Emodel concept by estimating user satisfaction from time-varying transmission impairments. This article evaluates several playout algorithms and shows a correspondence between their results and those obtained via statistical loss and delay metrics.}, keywords={Delay,Jitter,Packet Loss}, pdf={adaptive voip.pdf}, } </bibtex> <bibtex> @article{285, author={Dantcha,A.;Barry,L.;Murphy J.;Dunne,J.;Mullane,T.;Mcdonald,D.}, title={BER Performance in Wavelength Packet Switched WDM systems during Nano-Second Wavelength switching Events}, journal={Journal of Optical Communication}, year={2004}, pages={171-177(7Pages)}, volume={242}, abstract={An important characteristic of wavelength tuneable laser transmitters is that as they tune between output wavelength channels they may generate light at a range of other wavelengths. This effect may ultimately influence the design of WDM wavelength packetswitched networks employing wavelength tuneable transmitters. We have investigated this effect by examining the BER transmission performance of a WDM channel as a function of the degree of attenuation of another WDM wavelength signal during fast wavelength switching events. Our results show the importance of attenuating the output signal from the wavelength switched laser in order to prevent performance degradations on the monitored data channel.}, keywords={Optical communications, networks, wavelength division multiplexing, tuneable laser, packet switching, cross-channel interference}, pdf={ber performance.pdf}, } </bibtex> <bibtex> @article{372, author={G.Muntean;P.Perry;L.Murphy}, title={Performance Comparison of Local Area Video Streaming Systems}, journal={IEEE Communications Letters}, year={2004}, pages={326-328}, volume={8}, abstract={The performance of our Quality Oriented Adaptation Scheme (QOAS) for multimedia streaming in local networks is compared with other existing solutions (TFRCP, LDA+, and non-adaptive). This comparison is done in terms of bandwidth utilization, number of concurrent clients, loss rate, and end-user perceived quality. Simulation results show that for the same average end-user quality, our QOAS system can accommodate a significantly higher number of simultaneous clients while also having higher bandwidth utilization. For the same number of clients, the average end-user quality is always higher for QOAS than for the other solutions studied.}, keywords={Adaptive video streaming, feedback control, grading scheme, end-user quality.}, pdf={performance comparison.pdf}, } </bibtex> <bibtex> @article{375, author={G.Muntean;P.Perry;L.Murphy}, title={A New Adaptive Multimedia Streaming System for ALL-IP Multi Service Networks}, journal={IEEE Transactions on Broadcasting}, year={2004}, pages={1-10}, volume={50}, abstract={A significant challenge in all-IP multi-service networks is to balance the goal of providing high-quality services to the end-users with the desire to maximize the number of end-users that can be simultaneously served. This paper presents a solution to this challenge by using the Quality-Oriented Adaptation Scheme (QOAS) for delivering multimedia streams. This adaptive mechanism uses feedback from clients regarding the quality of delivery to assist the server in making dynamic adjustments to the transmitted streams. Experimental objective and subjective test results illustrate the significant performance improvements achieved by QOAS, both in terms of number of simultaneous viewers served and of end-user perceived quality.}, keywords={Adaptive multimedia streaming, all-IP multi-service networks, dynamic feedback, grading scheme, statistical multiplexing.}, pdf={new adaptive.pdf}, } </bibtex> <bibtex> @article{357, author={G.Muntean;P.Perry;L.Murphy}, title={Quality Oriented Adaptation Scheme for Video-On-Demand}, journal={IEE Electronic Letters}, year={2003}, pages={1689-1690}, volume={39}, abstract={The QOAS system proposed in [1, 2] is used for MPEG2 Video-on-Demand (VoD) delivery in local multi-service IP networks. QOAS balances the need for high end-user quality with increased network utilisation, regardless of the nature of other cross traffic. A high utilisation would allow an increased number of customers to be served from a limited infrastructure, minimising the costs, but decreasing the end-user quality. The goal of QOAS is to maximise end-user perceived quality and links’ utilisation in the existing network conditions. QOAS varies the transmitted quantity of video data by dynamically adjusting the quality of the streamed video. In comparison with other approaches [3], its novelty is that these adjustments are carried out based on client-computed quality scores that describe the current quality of delivery sent via regular feedback. These scores include shortterm and long-term assessments of both the end-user perceived video quality [1] and IP performance parameters (e.g. delay, jitter, loss rate). During transmission the video quality is varied in a controlled manner according to the feedback reports. It requires fewer negative quality scores to trigger a quality decrease than positive for an increase. This ensures a fast reaction during bad delivery conditions helping to eliminate their cause and makes sure that quality upgrades are performed only after the network conditions have improved.}, keywords={MPEG,QoS,IP Networks}, pdf={quality oriented.pdf}, } </bibtex> <bibtex> @article{415, author={H.Melvin;L.Murphy}, title={Time Synchronization for VoIP Quality of Service}, journal={IEEE Internet Computing}, year={2002}, pages={6 Pages}, volume={25-26}, abstract={Although packet-based and unmanaged networks like the Internet are ideal for delivering timeinsensitive data such as e-mail or static Web traffic, the growing demand for Web-based multimedia data exposes the limitations of core Internet protocols. With no end-to-end delay bounds, the public Internet’s best-effort service is unsuitable for delivering time-sensitive data and for interactive applications such as voice-over-IP. Normal speech consists of talkspurts, which typically last a few hundred milliseconds, and silence periods, which occur both within a spoken word and between words. In a packet-based network, voice packets are generated periodically at the sender and transmitted across the network. To cope with the packet interarrival variance inherent in besteffort service, current VoIP implementations generally implement fixed buffer schemes. Fixed buffer schemes make no attempt to match receiver operation to current network performance. An alternative approach is to use a more complex adaptive buffer scheme. This continuously matches playout delay to network conditions, at the expense of some packet loss due to late arrivals and some distortion of intertalkspurt silence periods. Various approaches seek to optimize the quality of service of VoIP applications (see the sidebar, “Quality of Service for VoIP,” next page, for a categorization of QoS approaches). We propose a system that uses synchronized time to combine the useful characteristics of both fixed and adaptive buffer strategies, thereby improving VoIP quality of service. Using a combination of global positioning system (GPS) technologies and the network time protocol (NTP), hosts can learn the precise end-to-end delay for each packet. This information can benefit both domestic and business Internet telephony users. In this article, we outline our proposed system and discuss issues arising from the use of synchronized time.}, keywords={Web Traffic,Web-based Multimedia,VoIP}, pdf={time.pdf}, } </bibtex>