Pubs:2006

<bibtex> @inproceedings{170, author={C. Thorpe; S. Murphy; L. Murphy}, title={Seamless Handover in Heterogeneous Radio Access Networks}, booktitle={IT&T}, year={2006}, abstract={This paper provides a detailed discussion of the problem of Seamless Handover in Heterogeneous Radio Access Networks. Brief descriptions of several wireless access technologies are included to provide some background information and to illustrate the importance of solving the seamless handover problem for network subscribers. Several approaches to providing a handover solution have been proposed, some of which will be described and compared, in order to indicate possible directions for continuing to search for a seamless handover solution. Various problems are present in the existing solutions, and are discussed in this paper. These problems are significant enough to warrant further investigation in the handover area, and leave scope for modifications and improvements.}, keywords={Seamless Handover, Heterogenous Networks, SCTP}, pdf={christina-itt06-cameraReady.pdf}, } </bibtex> <bibtex> @inproceedings{161, author={C. Thorpe; L. Murphy}, title={A Survey of Seamless Handover in Heterogeneous Radio Access Networks}, booktitle={ACM/IEEE International Symposium on Modeling, Analysis and Simulation of Wireless and Mobile Systems}, year={2006}, abstract={This paper provides a detailed discussion of the problem of Seamless Handover in Heterogeneous Radio Access Networks. Several approaches to providing a handover solution have been proposed, some of which will be described and compared, in order to indicate possible directions for continuing to search for a seamless handover solution. Various problems are present in the existing solutions, and are discussed in this paper. }, keywords={Seamless Handover, Heterogenous Networks, SCTP}, pdf={Christina-MSWIM-Oct-2006.pdf}, } </bibtex> <bibtex> @inproceedings{213, author={J. Fitzpatrick, S. Murphy and J. Murphy}, title={An Approach to Transport Layer Handover of VoIP over WLAN}, booktitle={CCNC}, year={2006}, abstract={In this paper a transport layer handover mechanism for Voice over Internet Protocol (VoIP) using the Stream Control Transmission Protocol (SCTP) is proposed. This handover mechanism utilizes the multi-homing feature of SCTP to allow connection to multiple wireless networks. Each available wireless network is probed with simulated VoIP data to obtain network performance metrics. Handover decisions are made based on the Mean Opinion Score (MOS) calculated from the ITU-T E-Model for voice quality assessment using the obtained measurements. Implementation and simulations were carried out using the NS2 network simulator. The results show the MOS obtained using the proposed handover mechanism on IEEE 802.11b WLAN access points (APs) under varying load conditions. High correlation is shown between the MOS from the proposed handover scheme and the MOS experienced by a VoIP node present in the network. A simulation showing an SCTP endpoint handover between AP’s is presented.}, keywords={SCTP, E-Model, VoIP, Handover, Heterogeneous Networks}, } </bibtex> <bibtex> @inproceedings{214, author={J. Fitzpatrick, and S. Murphy, and J. Murphy,}, title={SCTP based Handover Mechanism for VoIP over IEEE 802.11b Wireless LAN with Heterogeneous Transmission Rates}, booktitle={Communications, 2006. ICC '06. IEEE International Conference on}, year={2006}, abstract={In this paper a transport layer handover mechanism for Voice over Internet Protocol (VoIP) in 802.11b using the Stream Control Transmission Protocol (SCTP) is proposed. The multi-homing feature of SCTP is used to allow connections to several 802.11b Access Points (AP's). Probing packets that model VoIP encoded data at various transmission rates are used to obtain quality metrics from each of the available networks. Handover decisions are made based on the Mean Opinion Score (MOS) calculated from the ITU-T E-Model for voice quality assessment using the obtained measurements. The handover mechanism is shown to operate in 802.11b networks with heterogeneous transmission rates using multiple VoIP codecs. The results show a high correlation between the MOS predicted by the proposed mechanism and the MOS experienced by a VoIP call present in the network. Results verify the accurate operation of the scheme using multiple VoIP codecs at various transmission rates. A simulation showing an SCTP endpoint handover between heterogeneous transmission rate AP's is presented.}, keywords={SCTP, VoIP}, } </bibtex> <bibtex> @inproceedings{215, author={J. Fitzpatrick, S. Murphy, J. Murphy}, title={RTS/CTS Based Endpoint Admission Control for VoIP Over 802.11e}, booktitle={MMNS}, year={2006}, abstract={In this paper an endpoint-based admission control mechanism for VoIP over WLAN is proposed. The mechanism operates by first measuring the utilisation of the channel and comparing this to a pre-determined threshold, if the channel utilisation exceeds this threshold, the call is rejected. One important aspect of the mechanism is that it can operate in the presence of hidden terminals. This is done by using the Request-to-Send/Clear-to-Send WLAN signalling to determine channel utilisation. The scheme is designed to be flexible; it can operate with heterogeneous data rates, with varying traffic types and in the presence of legacy 802.11 nodes. The scheme was developed and evaluated using the Qualnet network simulator. An empirical approach was used to determine appropriate admission thresholds. Then, simulations were performed to demonstrate the successful operation of the scheme.}, keywords={Call Admission Control, VoIP, 802.11e, RTS/CTS}, } </bibtex> <bibtex> @inproceedings{311, author={Carrig,B.;Denieffe,D.;Murphy,J.}, title={A Relative Delay Minimization Scheme for Multiplayer Gaming in Diffrentiated Services Network}, booktitle={ACM SIGCOMM Workshop on Network & System Support for Games}, year={2006}, abstract={Multiplayer gaming over the Internet continues to grow in popularity, despite a lack of Quality of Service (QoS) mechanisms. Future QoS-aware networks such as those based on the Differentiated Services (DiffServ) framework will provide an opportunity for gamers to enhance their game-playing experience. An important QoS metric for networked games is a user’s delay relative to the delay of other users. In this paper, we propose a Relative Delay Minimization (RDM) algorithm for use in DiffServ environments. Simulation results are described and presented showing that the algorithm can reduce the Relative Delay Variation (RDV) between users in a DiffServ environment.}, keywords={Network Games, Relative Delay, DiffServ, QoS}, pdf={a relative delay.pdf}, } </bibtex> <bibtex> @inproceedings{312, author={Noonan,J.;Perry,P.;Murphy,J.}, title={End-point Synchronisation & Handover For Multi-homed Services}, booktitle={IEE Proceedings-Communications}, year={2006}, abstract={It is proposed to implement a synchronised routing table at the transport layer, referred to as an Association Routing Table (ART), to improve the performance of multi-homed transport protocols. An algorithm is described that ensures that the routing tables can be synchronised, which is then used to implement a handover mechanism. The ART is implemented within SCTP. It is shown that by using a synchronised ART, it is possible to implement failover in cases where standard SCTP cannot, con¯gurations are more resilient to network errors, and it is possible to perform a handover without any network support.}, keywords={Multi-homing, routing, transport layer, SCTP, handovers}, pdf={end point-sychronization.pdf}, } </bibtex> <bibtex> @inproceedings{313, author={Hillestad,O.I.;Perkis,A.;Genc,V.;Murphy,S.;Murphy,J.}, title={Delivery of On-Demand Video Services in Rural Areas via IEEE 802.16 Broadband Wireless Access Networks}, booktitle={ACM 2nd Workshop on Wireless Multimedia Networking & Performance Modelling }, year={2006}, abstract={A simulation study of delivery of streaming video on-demand via IEEE 802.16 based technologies is described. A number of scenarios are simulated which are representative of rural area deployments of such technologies. The study finds that IEEE 802.16 can support up to 9/10 simultaneous users streaming typical cinematic video content in CIF resolution, 24 frames/s, at average rates of around 750 kbps. Further, the study demonstrates the utility of H.264/AVC Scalable Video Coding (SVC) and a buffer-based congestion control algorithm in an adaptive video streaming solution.}, keywords={IEEE 802.16, video streaming, scalable video coding}, pdf={delivering of on demand.pdf}, } </bibtex> <bibtex> @inproceedings{314, author={Ormond,O.;Muntean,G.;Murphy,J.}, title={Evaluation of an Intelligent Utility-Based Strategy for Dynamic Wireless Network Selection}, booktitle={Autonomic Management of Mobile Multimedia Services}, year={2006}, abstract={In the case of next generation wireless networks, different users with various multi-homed personal wireless devices will aim to exploit the full potential of the choice of services and applications available over different radio access networks. In their selection of a certain radio access network consumers will consider money and delay preferences for the current application and will rely on intelligent network-selection decision strategies to aid them in their choice. This paper describes the evaluation of an intelligent utility-based strategy for network selection in a multi-access network situation for transfer of large non real-time data files. A number of scenarios are examined which compare the proposed network selection strategy against other possible strategies. Test results show how by using this network selection strategy significant benefits in terms of combined average delay and cost per file transferred as well as transfer efficiency are obtained.}, keywords={Heterogeneous Wireless Networks, Multi-homed Radio Terminals, User-centric Network Selection.}, pdf={evaluation.pdf}, } </bibtex> <bibtex> @inproceedings{315, author={Parsons,T.;Mos,A.;Murphy,J.}, title={Non-Intrusive End to End Run-time Path Tracing for J2EE Systems}, booktitle={IEE Proceedings-Software}, year={2006}, abstract={An end-to-end runtime path-tracing approach for J2EE systems has been introduced. The approach is non-intrusive and thus does not require instrumentation of middleware or application source code. The implementation of the system has been realised in the COMPAS Java end-to-end monitoring tool that extends and integrates a number of open source projects. The first set of results shows the performance overhead associated with the tool. Further results show the portability of this approach, by applying it to a number of different application server implementations. Finally, it is also shown that runtime paths collected by the implementation can be used for reasoning about the overall system structure and design of complex enterprise applications.}, keywords={IEEE ,Server}, pdf={non-intrusive.pdf}, } </bibtex> <bibtex> @inproceedings{316, author={Barrett,R.;Pahl,C.;Patcas,L.M.;Murphy,J.}, title={Model Driven Distribution Pattern Design for Dynamic Web Service Compositions}, booktitle={ACM 6th International Conference on Web Engineering,ICWE}, year={2006}, abstract={Web service compositions are often used to realise servicebased enterprise applications. These enterprise systems are built from many existing discrete applications, often legacy applications exposed using Web service interfaces. Acceptance of these systems is often constrained by non-functional aspects, such as Quality of Service (QoS). A number of factors a�ect the QoS of an enterprise system, including availability, scalability and performance. There are a number of architectural con�gurations or distribution patterns, which express how a composed system is to be deployed. These distribution patterns have a direct impact upon the QoS of the composition. However, the amount of code required to realise these distribution patterns is considerable. Additionally, there is an increased deployment time associated with setting up di�erent distribution patterns. We therefore propose a novel approach which combines a Model Driven Architecture using UML 2.0 for modeling and subsequently generating Web service compositions, with a method for achieving dynamic decentralised interaction amongst services with reduced deployment overheads. These approaches combined provide for the generation of dynamic Web service compositions driven by a distribution pattern model.}, keywords={Distribution patterns, Web services, compositions, decentralisation, MDA}, pdf={model driven.pdf}, } </bibtex> <bibtex> @inproceedings{317, author={Ormond,O.;Murphy,J.;Muntean,G.}, title={Utility-based Intelligent Network Selection in Beyond 3G Systems}, booktitle={IEEE International Conference on Communications}, year={2006}, abstract={Development in wireless access technologies and multihomed personal user devices is driving the way towards a heterogeneous wireless access network environment. Success in this arena will be reliant on the ability to offer an enhanced user experience. Users will plan to take advantage of the competition and always connect to the network which can best service their preferences for the current application. They will rely on intelligent network selection decision strategies to aid them in their choice. The contribution of this paper is to propose an intelligent utility-based strategy for network selection in this multi-access network scenario. A number of utility functions are examined which explore different user attitudes to risk for money and delay preferences related to their current application. For example we show that risk takers who are willing to pay more money get a better service.}, keywords={Wireless Networks,3G}, pdf={utility.pdf}, } </bibtex> <bibtex> @inproceedings{318, author={Carrig,B.;Denieffe,D.;Murphy,J.}, title={Delivering Quality of Service for Gaming Applications in Best Effort Networks}, booktitle={13th International Conference on Telecommunications}, year={2006}, abstract={This paper describes a scheduler which provides non-elevated Quality of Service (QoS) for two different classes of traffic. A Delay-Sensitive (DS) class receives a low delay service at the expense of an increased probability of packet loss. The non-DS traffic receives at least the same level of throughput as it would in an ordinary best effort network. The design of the scheduler is presented and contrasted with similar schedulers such as the Alternative Best Effort (ABE) service. Simulation results for a network carrying a mixture of FTP and Quake 3 multiplayer gaming traffic are also shown. It was discovered that even for a heavily-loaded network, with a large proportion of non-DS traffic, there are benefits for interactive games traffic availing of the DS service.}, keywords={Networked Games, Non-elevated QoS, Quality of Service}, pdf={delivering quality.pdf}, } </bibtex> <bibtex> @inproceedings{319, author={Noonan,J.;Perry,P.;Murphy,S.;Murphy,J.}, title={Stall & Path Monitoring Issues in SCTP,IEEE Infocom}, booktitle={Conference on Computer Communications}, year={2006}, abstract={This paper presents how SCTP can stall in multihomed scenarios during failover and under certain circumstances. A stall is where an SCTP end-point ceases to communicate for an extended period of time, but does not report any error to the upper layer. This paper presents two different sets of circumstances where a stall can occur: firstly when there is an underestimation of the Retransmission Time-Out (RTO) value for a redundant network path; and secondly when a network error occurs that causes only SACKs to be lost, which confuses the SCTP sender about which network path is operational. Solutions to both of these stalls are presented that include modifying the RTO value, applying Karn’s algorithm to path monitoring and ensuring the destination address selection policy for SACKs is changed. This paper also presents a mechanism to de-couple data acknowledgement and path monitoring when using multi-homed transport protocols, which should remove the ambiguity about path monitoring and offers a universal solution to the stall.}, keywords={SCTP}, pdf={stall and path.pdf}, } </bibtex> <bibtex> @inproceedings{320, author={Ormond,O.;Murphy,J.;Muntean,G.}, title={Economic Model for Cost Effective Network Selection Strategy in Service Oriented Heterogenous Wireless Network Environment}, booktitle={10th IEEE/IFIP Network Operations & Management Symposium}, year={2006}, abstract={This paper describes and formalises the Service Oriented Heterogeneous Wireless Network Environment (SOHWNE)A the future service provision and delivery environment that will support ubiCuitous user access anywhere at any time from diverse devices to a broad range of services. These services can be offered by third parties and can be accessed via one of many available networks. This paper also proposes and describes a novel algorithm for intelligent costoriented and performance-aware selection between available networks. This user-centric strategy focuses on the maximisation of consumer surplus when selecting the best available connection for transferring non real-time dataA with user specified time constraintsA in a user-centric SOHWNE.}, keywords={Consumer SurplusA Decision-making StrategiesA Multi-provider Network EnvironmentA Non real-time Data.}, pdf={economic model.pdf}, } </bibtex> <bibtex> @inproceedings{321, author={Parsons,T.;Murphy,J.}, title={The 2nd International Middleware Doctoral Symposium:Detecting Performance Antipatterns in Component-Based Enterprise Systems}, booktitle={IEEE Distributed Systems Online }, year={2006}, abstract={Internet-enabled enterprise applications often fail to meet their performance requirements. This can lead to development delays or, even worse, loss of business due to customer dissatisfaction with sluggish or unreliable service. Inefficient enterprise systems are often the result of system developers making incorrect or suboptimal design decisions. Such decisions occur because today’s enterprise applications are extremely large and complex, and developers often don’t completely understand the entire application. Consequently, they often don’t completely understand the performance implications of their design decisions, and as a result, systems frequently fail to meet their performance agreements. }, keywords={Performance Oriented,}, pdf={2nd international.pdf}, } </bibtex> <bibtex> @inproceedings{391, author={A.Ufimtsev;L.Murphy}, title={Performance Modelling of a JAVAEE Component Application using Layered Queuing Networks:Revised Approach & a Case Study}, booktitle={Specification & Verification of Component-Based Systems(SAVCBS'06)}, year={2006}, abstract={Nowadays component technologies are an integral part of any enterprise production environment. Performance and scalability are among the key properties of such systems. Using Layered Queuing Networks (LQN), one can predict the performance of a component system from its design. This work revises the approach of using LQN templates and offers a case study by using the revised approach to model a realistic component application. Both strong points and shortcomings of the approach are discussed.}, keywords={performance modeling, JavaEE, component systems, ECPerf, Layered Queuing Network.}, pdf={performance.pdf}, } </bibtex> <bibtex> @inproceedings{392, author={A.Ufimtsev;T.Parsons;L.Patcas;J.Murphy;L.Murphy}, title={Introducing Performance Engineering by means of Tools & Practical Exercises}, booktitle={Annual International Conference on Computer Science & Software Engineering}, year={2006}, abstract={Many software engineers complete their education without an introduction to the most basic performance engineering concepts. IT specialists need to be educated with a basic degree of performance engineering knowledge, so they are aware of why and how certain design and development decisions can lead to poor performance of the resulting software systems. To help address this need, the School of Computer Science and Informatics at University College Dublin offered a final year undergraduate/first year postgraduate module on ”Performance of Computer Systems” in Autumn 2005. In this paper we document how performance engineering was introduced to the students through practical exercises, and how these exercises relate to industry problems.}, keywords={Software,J2EE}, pdf={introducing performance.pdf}, } </bibtex> <bibtex> @inproceedings{393, author={A.Ufimtsev;L.Murphy}, title={Automatic System for Linux Kernel Performance Testing}, booktitle={2006 Linux Symposium}, year={2006}, abstract={We introduce an automatic and open kernel testing system. We argue that only by opening a test system to the community and aggregating the results from a variety of sources can one get a comprehensive picture of the kernel’s performance status. Our system can also help identifying problems with specific parts of code whether it is a device driver, some other module, or platform-specific code. Design of both client and server parts of the system is described. Since system is open, specific emphasis in client part is placed on successful automation and configuration of the testing process. The emphasis of the server part is placed on regression detection and accidental/malicious input elimination. Current implementation status is presented.}, keywords={Kernel System,Linux}, pdf={automatic.pdf}, } </bibtex> <bibtex> @inproceedings{394, author={A.Ufimtsev;A.Kucherenko;L.Murphy}, title={Impact of Virtual Managers on Performance of J2EE Applications}, booktitle={9th International Symposium on Component-Based Software Engineering}, year={2006}, abstract={We investigate the impact of Operating System's Virtual Memory Managers (VMMs) on performance of enterprise applications. By taking various popular branches of the Linux kernel and modifying their VMM settings, one can see the e®ects it introduces on ECPerf J2EE Benchmark. JBoss application server is used to run ECPerf. Our tests show that even the change of one parameter in VMM can have signi¯cant performance impacts. Performance of various kernel branches is compared. Parameter sensitivity and in°uence of speci¯c settings are presented.}, keywords={Operating System,J2EE,Linux}, pdf={impact.pdf}, } </bibtex> <bibtex> @inproceedings{395, author={P.McGovern;S.Murphy;L.Murphy}, title={Protection Againest Link Adaptation for VoWLAN}, booktitle={15th IST Mobile & Wireless Communications Summit}, year={2006}, abstract={In this paper a scheme is proposed to deal with the problem of Link Adaptation (LA) of an ongoing call in a Voice over Wireless Local Area Network (VoWLAN) environment. The scheme operates by dropping the call from the system if the LA affects the call quality of the other ongoing calls. The proposed scheme was evaluated on an experimental test-bed and results show that it protected the quality levels of the other ongoing calls under various network configurations.}, keywords={Voice over IP (VoIP), IEEE 802.11, Admission Control (AC), Link Adaptation (LA)}, pdf={protection.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> @inproceedings{397, author={P.McGovern;S.Chung;S.Murphy;L.Murphy}, title={Endpoint Admission Control for VoIPoWLAN }, booktitle={13th International Conference of Telecommunications}, year={2006}, abstract={In this paper a Call Admission Control (CAC) scheme for Voice over Internet Protocol (VoIP) over a Wireless Local Area Network (WLAN) is proposed. The CAC scheme is based on the Endpoint Admission Control (EAC) paradigm where the endpoints, i.e. the WLAN terminals, probe the network to ascertain if the call can be supported with acceptable Quality of Service (QoS). The proposed scheme was evaluated on an experimental test-bed and test results show that correct Admission Control (AC) decisions were made under various network configurations.}, keywords={Voice over IP (VoIP), Wireless Local Area Network (WLAN), IEEE 802.11, Admission Control (AC)}, pdf={end point.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>