Pubs:2005

<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> @inproceedings{301, author={Diaconescu,A.;Murphy,J.}, title={Automating the Performance Management of Component-Based Enterprise Systems through the use of Redundancy}, booktitle={IEEE/ACM International Conference on Automated Software Engineering(ASE-2005)}, year={2005}, abstract={Component technologies are increasingly being used for building enterprise systems, as they can address complex functionality and flexibility problems and reduce development and maintenance costs. Nonetheless, current component technologies provide little support for predicting and controlling the emerging performance of software systems that are assembled from distinct components. This paper presents a framework for automating the performance management of complex, component-based systems. The adopted approach is based on the alternate usage of multiple component variants with equivalent functional characteristics, each one optimized for a different running environment. A fully-automated framework prototype for J2EE is presented, along with results from managing a sample enterprise application on JBoss. A mechanism that uses monitoring data to learn and automatically improve the framework’s management behaviour is proposed. The framework imposes no extra requirements on component providers, or on the component technologies.}, keywords={autonomic management, J2EE, decision policies}, pdf={automating performance.pdf}, } </bibtex> <bibtex> @inproceedings{302, author={Ashagi,O.;Ruzzelli,A.G.;Murphy,L.;Murphy,J.}, title={Performance Modelling of a Distributed Approach to Interference Mitigation in License-Exempt IEEE 802.16 Systems}, booktitle={IEEE International Symposium on New Frontiers in Dynamic Spectrum Access Networks(DySPAN 2005)}, year={2005}, abstract={In this paper, three approaches to modelling a distributed approach to interference mitigation in 802.16 Licenseexempt (LE) systems are described. An Interference-free (IF) approach in which no interference is permitted at any node of the system; a Controlled-interference (CI-T) and a Controlled- Interference with Fairness (CI-F) approaches where interference is permitted at nodes that do not benefit from receiving the current transmission. The results show that the CI-F and CI-T schemes result in much better overall performance that either the IF scheme or the distributed scheme. Further, they result in much greater levels of BS activity. Despite being very conservative, even the IF scheme performs better than the distributed scheme in terms of throughput. This can be attributed to the fact that the distributed scheme suffers from collisions.}, keywords={Wireless Communication}, pdf={performance modelling.pdf}, } </bibtex> <bibtex> @inproceedings{303, author={Graja,H.;Peery,P.;Murphy ,J. }, title={A Low Complexity Algorithm for Statistically Based Estimation of Average IP Packet Delay in Cellular Data Networks}, booktitle={International Teletraffic Congress,ITC-19}, year={2005}, abstract={A new, low computation complexity technique for prediction of the average delay of IP packets, transported over cellular data networks with SR-ARQ loop, is presented in this paper. This prediction takes into account the SR-ARQ in�uence on the average IP packet delay, assuming that the MAC works with a static schedule policy (offering a �xed periodic access to radio resources). This assumption allows the use of this prediction as a link performance descriptor that is complementary to C/I, BER and BLER. A series of simulations and calculations have been performed to analyze the error introduced by the prediction. The results of these tests prove that the proposed method introduces a negligible prediction error, while the computation complexity is kept at a reasonable low level. Keywords:ARQ, IP packet delay, wireless QoS}, keywords={IP packet delay, wireless QoS, mobile multimedia}, pdf={low complexity.pdf}, } </bibtex> <bibtex> @inproceedings{304, author={Ormond,O.;Perry,P.;Murphy,J.}, title={Network Selection Decision in Wireless Heterogenous Networks}, booktitle={IEEE 16th International Symposium on Personal.Indoor & Mobile Radio Communications}, year={2005}, abstract={In future wireless and mobile environments it is likely that users will have access to multiple networks at the same time. Therefore there is a need to have mechanisms in place to decide which network is the most suitable for each user at each moment in time for every application that the user requires. We propose a user-centric solution where users choose the radio access network which meets their data transfer terms best. Naturally, each user wants timely quality data delivery at a low cost. In the radio environment data rates can never be guaranteed due to the unreliable nature of the radio links. The user network selection algorithm needs to predict the data rate on offer in each of the available networks and make the decision based on those predictions. This paper allows the user to select the network that will maximise the consumer surplus for non real-time data, while taking into account the delays.}, keywords={Non real-time data, RAN Selection Decision, Service Oriented Heterogeneous Wireless Networks}, pdf={network selection.pdf}, } </bibtex> <bibtex> @inproceedings{305, author={Todinca,D.;Sora,I.;Perry,P.;Murphy,J.}, title={Supporting Flexible Network Operator Policies in EGPRS Through Admission Control}, booktitle={IFIP 10th International Conference on Personal Wireless Communications}, year={2005}, abstract={Many of the admission control strategies for cellular data networks proposed in the literature allow the network operator to use di®erent policies, depending on the network load, the number of users from each quality of service class, etc. Each policy is applied in a certain region, the regions being separated by thresholds. Those approaches su®er from a lack of °exibility: when the operating conditions change, the values for the thresholds have to be re-calculated. Our work supports °exible and adaptable network operator policies, overcoming the drawbacks of the existing algorithms through a fuzzy logic based solution.}, keywords={Network}, pdf={supporting flexible.pdf}, } </bibtex> <bibtex> @inproceedings{306, author={Klusek,B.;Murphy,J.;Barry,L.P.}, title={Cost-based burst dropping strategy in Optical Burst Switching Networks}, booktitle={IEEE 7th International Conference on Transport Optical Networks}, year={2005}, abstract={Optical Burst Switching (OBS) is a new paradigm for future all-optical networks. Intentional burst dropping is one of techniques used to achieve desired quality of service. In this paper we note that some bursts are more likely to cause contention. We propose a cost function that can be used to predict the likelihood that a given burst will interfere with other traffic, then we explain how, by using this information a new burst dropping strategy can be designed. We compare our method with a random burst dropping technique and show that the cost-based approach offers a significant performance improvement. Keywords: Optical Burst Switching (OBS), burst dropping, quality of service.}, keywords={Optical communications}, pdf={cost based burst.pdf}, pdf={statistical estimation.pdf}, } </bibtex> <bibtex> @inproceedings{307, author={Graja,H.;Peery,P.;Murphy ,J. }, title={A Statistical Estimation of Average IP Packet Delay in Cellular Data Networks}, booktitle={IEEE Wireless Communication & Network Conference}, year={2005}, abstract={A novel technique for estimating the average delay experienced by an IP packet in cellular data networks with an SRARQ loop is presented. This technique uses the following input data: a statistical description of the radio channel, ARQ loop design parameters and the size of a transported IP packet. An analytical model is derived to enable a closed form mathematical estimation of this delay. To validate this model, a computer based simulator was built and tests showed good agreement between the simulation results and the model. This new model is of particular interest in predicting the packet delay for conversational traffic such as that used for VoIP applications.}, keywords={ARQ,IP packet delay, wireless QoS, mobile multimedia}, pdf={statistical estimation.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> @inproceedings{309, author={Klusek,B.;Murphy,J.;Perry,P.}, title={Cost-based Wavelength Allocation Algorithms in Optical Burst Switching Networks}, booktitle={APOC 2004,SPIE,Optical Transmission,Switching & Subsystems II,LNCS}, year={2005}, abstract={Optical Burst Switching(OBS) is a new paradigm for future all optical networks.It has been noted that performance of an OBS nodedepends on the wavelength algorithms called cost based algorithms.We note that bursts compete for more type of resources than wavelength alone.For example if a given burst is to be allocated successfully,a Fiber Delay Line (FDL) or a wavelength convertor may have to be used.It can be expected however that the set of available resources will be limited.If at a given time all the convertors are used,then any arriving burst will have to be allocated on the same wavelength-if it is available.Similarly the unavailablity of FDLs will decrease the probablity of burst being accepted.In a cost-based algorithm,each resource is assigned a metric(or price).Channels arepriced according to their suitablity 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 or wavelength converter),and the one with the lowest metric is chosen.To show how the performance of a cost-based algorithm compares to other algorithm we present the result of our simulations for a node with full conversion capablity and a shared FDL.}, keywords={Wavelength}, pdf={cost based.pdf}, } </bibtex> <bibtex> @inproceedings{377, author={H.Melvin;L.Murphy}, title={Synchronisation of Internet Multimedia Streams:Some Issues & Solutions}, booktitle={26th IEEE Real-Time Systems Symposium}, year={2005}, abstract={Synchronised clocks and circuit switching constitute a basic building block within the heart of the traditional PSTN and this coupled with dumb terminals ensures that media synchronisation is not an issue. The same cannot be said of Internet Multimedia where delays are generally non-deterministic and where terminals are much more complex. Previous work by the authors has shown that by incorporating synchronised time into VoIP terminals, significant gains in voice quality can be achieved. Related work by the authors has examined the extent to which a lack of synchronisation (or skew) both within and between terminals can affect VoIP quality and has proposed and tested a high-level solution for skew detection/compensation. In this paper we present a number of more complex scenarios where the lack of clock synchronisation can impact on performance; these include PSTN/VoIP gateways, the use of media mixers for combining media streams and conferencing services. We describe a number of testbeds currently under development where the use of synchronised time and the high level skew detection/compensation approach will be evaluated as a means of dealing effectively with these scenarios.}, keywords={Media Synchronisation, Clock Skew, PSTN-VoIP Gateway, Media Mixers .}, pdf={synchronization.pdf}, } </bibtex> <bibtex> @inproceedings{378, author={G.Hanley;S.Murphy;L.Murphy}, title={Adapting WLAN MAC Parameters to Maximise VoIP Call Capacity }, booktitle={ACM/IEEE International Symposium on Modeling,Analysis & Simulation of Wireless & Mobile Systems}, year={2005}, abstract={This work describes a detailed simulation-based study of the performance of an IEEE 802.11e Medium Access Con- trol (MAC) layer over an IEEE 802.11g Physical (PHY) layer. The study focuses on the number of simultaneous bidirectional G.711 Voice over IP (VoIP) calls that can be supported by a Wireless Local Area Network (WLAN) us- ing the Extended Rate PHY - Orthogonal Frequency Division Modulation (ERP-OFDM) mode of 802.11g. A new scheme for adapting the WLAN MAC parame- ters is proposed in this work. The new scheme dynamically adapts the Contention Window (CW) based on the retrans- mission rate of the system. In addition, an adaptive Trans- mission Opportunity (TXOP) mechanism aids in balancing the uplink and downlink tra±c levels and so provides the equality in uplink and downlink performance that is required for bidirectional VoIP tra±c. The proposed scheme can thus maintain acceptable levels of QoS for higher call capacities, increasing the overall VoIP capacity of the system.}, keywords={Wireless LAN, VoIP, Medium Access Control, Quality of Service, Parameter Adaptation.}, pdf={adapting wlan.pdf}, } </bibtex> <bibtex> @inproceedings{379, author={G.Hanley;S.Murphy;L.Murphy}, title={Performance of VoIP over IEEE 802.11g DSSS-OFDM Mode with IEEE 802.11e QoS Support}, booktitle={2nd International Conference on E-Business & Telecommunication Networks(ICETE 2005)}, year={2005}, abstract={This paper examines, via simulation, the performance of an 802.11e MAC over an 802.11g PHY operating in DSSS-OFDM mode. The DSSS-OFDM scheme provides data rates of up to 54Mb/s as well as interoperability with 802.11b nodes. Due to the widespread use of 802.11b nodes, such interoperability is an important consideration. This paper involves a study of the number of simultaneous bidirectional G.711 VoIP calls that can be supported by such a WLAN. The results show that this mode of operation introduces a very significant overhead. The actual number of calls that can be carried is limited to 12 when using the 24Mb/s data rate and 13 when using either the 36Mb/s or 54Mb/s rates. These results demonstrate the well-known disparity between uplink and downlink performance, with the downlink imposing the limit on the number of calls that can be carried by the system in the cases studied. The results also show that when when a significant amount of lower priority traffic is introduced into the system, it can have a significant impact on VoIP call capacity despite the use of 802.11e.}, keywords={WLAN, IEEE 802.11e, QoS, Voice over IP, Medium Access Control}, pdf={performance.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> @inproceedings{381, author={J.Xu;A.Oufimtsev;M.Woodside;L.Murphy}, title={Performance Modeling & Prediction of Enterprise JavaBeans with Layered Queuing Network Templates }, booktitle={ACM Workshop on Specification & Verification of Component Based Systems}, year={2005}, abstract={Component technologies, such as Enterprise Java Beans (EJB) and .NET, are used in enterprise servers with requirements for high performance and scalability. This work considers performance prediction from the design of an EJB system, based on the modular structure of an application server and the application components. It uses layered queueing models, which are naturally structured around the software components. This paper describes a framework for constructing such models, based on layered queue templates for EJBs, and for their inclusion in the server. The resulting model is calibrated and validated by comparison with an actual system.}, keywords={Layered Queueing Network, template, Enterprise Java Bean, performance modeling, model calibration, software profiling.}, pdf={performance modelling.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> @inproceedings{384, author={H.Melvin;L.Murphy}, title={Exploring the Extent & Impact of Playout Adjustments within VoIP Applications on MOS Scores}, booktitle={Measurement of Speech & Audio Quality in Networks}, year={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 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 perceiv}, pdf={exploring extent.pdf}, } </bibtex> <bibtex> @inproceedings{385, author={G.Muntean;L.Murphy}, title={Solution Design for Efficient Distribution of Muktimedia-based Services to Home Residences}, booktitle={International Conference on Software Development}, year={2005}, abstract={This paper presents a design problem and its solution in form of the Quality Oriented Adaptation Scheme (QOAS), the client-server system that implements it and the related architecture for the delivery of multimedia-based services to residential users. QOAS was proposed to adaptively stream high quality multimedia-based services to home residences, adjusting the content based on existing delivery conditions. QOAS principle, the system that deploys it and the architecture of the system for the delivery of multimedia-based services are briefly described. Subjective testing results are also presented and show very good performance of the implemented QOAS-based multimedia delivery system.}, keywords={Software Development, Multimedia Streaming, Subjective Testing}, pdf={solution design.pdf}, } </bibtex> <bibtex> @inproceedings{386, author={D.McGuinness;L.Murphy}, title={A simulation model of a multi-server EJB system}, booktitle={Workshop on Advance in Model-Based Software Testing}, year={2005}, abstract={Despite the fact that EJB (Enterprise Java Beans) is a widely used technology, research in the area of performance modelling of EJB application servers is quite sparse. This paper will describe how WorkbenchTM, an advanced simulation modelling tool, can be used to build a scalable model of a multi-server EJB system that allows users to input variables that describe interactions and their constituent methods, as well as system parameters. The model will output the average time for each given user interaction and allow users to seek system improvements by changing the system parameters and workloads.}, keywords={EJB,JavaBeans}, pdf={simulation model.pdf}, } </bibtex> <bibtex> @inproceedings{387, author={O.Ashagi;S.Murphy;L.Murphy}, title={Mitigating Interference between IEEE 802.16 Systems Operating in License-exempt Mode}, booktitle={3rd International Conference on Wired/Wireless Internet Communications}, year={2005}, abstract={A rudimentary approach to mitigate interference issues in license-exempt 802.16 systems is presented. This approach operates by permitting each Base Station (BS), and associated Subscriber Stations (SSs) to remain inactive for a speci¯ed fraction of the time. Other systems can then transmit with a reduced likelihood of interference. A simulator was developed to determine how this system performs. The results show that the throughput of the system is very sensitive to the fraction of time each BS is active; the system throughput is maximised when each BS is active less than 40% of the time for the scenarios studied. The re- sults demonstrate a discrepancy between uplink and downlink through- put which can be attributed to the greater amount of overheads in the uplink. Finally, the results show that broadcast information being trans- mitted periodically at full power has a signi¯cant detrimental impact on the system.}, keywords={Internet,Base Station}, pdf={mitigating interference.pdf}, } </bibtex> <bibtex> @inproceedings{388, author={S.Murphy;S.Goor;L.murphy}, title={Performance Comparison of Multiplexing Techniques for MPEG-4 Object Based Content}, booktitle={IEEE International Workshop on Multimedia Systems & Networking(WMSN 05)}, year={2005}, abstract={A study of the performance of a number of different multiplexing schemes was conducted in the context of streaming of MPEG-4 object-based content, with particular emphasis on streaming content to mobile devices. The comparison involved six different schemes. The schemes differed in terms of how they packed the data for each arbitrarily shaped video object into packets. An experimental testbed was constructed to compare the performance of the different schemes. The experiments showed that the scheme in which no effort is made to maximise the amount of data in the packet performs worse than the others in terms of the amount of overhead it generates and the video quality obtained when it is used to stream content. The other schemes did exhibit small differences in terms of the amount of overhead generated and video quality obtained, but the differences were not sufficiently large to be able to identify any as being clearly better than the others.}, keywords={MPEG-4,Multiplexing}, pdf={performance comparison.pdf}, } </bibtex> <bibtex> @inproceedings{389, author={A.Oufimtsev;L.Murphy}, title={Method Input Parameters & Performances of EJB Applications}, booktitle={}, year={2005}, abstract={We investigated the impact of method input parameters on component performance, which is usually neglected during an application design stage. We evaluated a set of Commercial Off-The-Shelf (COTS) components which use Enterprise Java Beans (EJB) technology. These components were deployed on Web- Sphere Application Server and tested using a custom-built remote client. The client keeps track of execution times, while the server has JProbe Profiler embedded in the EJB container to monitor the interactions. For test purposes we used only stateless session beans, allowing us to concentrate on the possible dependency of server performance on input parameter variations. Test results show that significant performance impacts can be caused by a relatively small number of input parameter dependencies.}, keywords={EJB container, COTS, method input parameters, performance, profiling}, pdf={methos input.pdf}, } </bibtex> <bibtex> @inproceedings{390, author={G.Cunningham;S.Murphy;L.Murphy;P.Perry}, title={Seamless Handover of Streamed Video over UDP between Wireless LAN's}, booktitle={IEEE Consumer Communications & Networking Conference}, year={2005}, abstract={The seamless handover of streamed video in a WLAN with UDP as the transport layer is considered. The use of handover for stationary nodes in the case of network congestion is motivated. Next, the relationship between delay and loss in WLANs is studied, with the conclusion that delay can be used as an indicator of when loss is likely to occur. Delay can therefore be used as a basis of a handover scheme which can minimize loss. Such a handover scheme is proposed in which the client makes two simultaneous connections to the same server through two separate WLANs, and it is shown that the client can use the relative packet delay between the two streams to determine which network delivers the best performance; this information is then used to determine when to perform a handover. The proposed scheme is implemented and results are presented that show the successful handover of an RTP over UDP stream using this scheme in a live WLAN environment.}, keywords={Seamless Handover, Streamed Video, Wireless LAN.}, pdf={seamless handover.pdf}, } </bibtex> <bibtex> @inproceedings{421, author={G.Muntean;P.Perry;L.Murphy}, title={Objective & Subjective Evaluation of QAOS Video Streaming over Broadband Networks}, booktitle={IEEE Electronic Trans. on Network & Service Management}, year={2005}, abstract={This article presents objective and subjective testing results that assess the performance of the Quality-Oriented Adaptation Scheme (QOAS) when used for high quality multimedia streaming over local broadband IP networks. Results of objective tests using a QOAS simulation model show very efficient adaptation in terms of end-user perceived quality, loss rate, and bandwidth utilization, compared to existing adaptive streaming schemes such as LDA+, and TFRCP. Subjective tests confirm these results by showing high end-user perceived quality of the QOAS under various network conditions.}, keywords={QOAS,IP Networks}, pdf={objective.pdf}, } </bibtex> <bibtex> @inproceedings{434, author={O.Ormond;Gabriel-Miro Muntean;J.Murphy}, title={Network Selection Strategy in Heterogenous Wireless Networks}, booktitle={IT&T Conference }, year={2005}, abstract={Next generation communications will offer a wide range of services available to users anywhere at any time. How wireless users access those services depends on the current user context: location, characteristics of the available networks, user preferences, application requirements and terminal capabilities. The vision is that users will not be tied down to a long-term contract with one single operator and will instead be able to dynamically choose access provision on a per call basis. The evolving competitive marketplace will provide a choice of access networks in any given location, each offering different network technologies with varying characteristics to transport the user’s communications application. This paper highlights the need for an access network selection decision strategy to aid users operating in this heterogeneous multi-network wireless environment. We propose a consumer surplus based algorithm that selects the best available network for transferring non real-time data, with user specified time constraints. When compared to an always cheapest strategy simulation results show significant performance gains in transfer completion time for the consumer surplus based strategy.}, keywords={Wireless Network,Communication}, pdf={network.pdf}, } </bibtex> <bibtex> @inproceedings{438, author={L.M.Patcas;J.Murphy;Gabriel-Miro Muntean}, title={Middleware Support for Data-Flow Distribution in Web-Services Composition}, booktitle={European Conference on Object-Oriented Programming}, year={2005}, abstract={Composition ofWeb services helps to lower the time-to-market of service-based applications by reusing the functionality provided by ser- vices that are already deployed at geographically distributed locations. Due to the diversity of services, the client acceptance of new applica- tions is determined more and more by non-functional aspects, such as Quality of Service, or cost. The throughput, response time, and commu- nication cost of composite services depend on the characteristics of each component service involved, as well as on the manner these components are tied together. Research has shown that distributed data-°ow models can o®er better performance and lower communication costs in service composition than centralized models. However, an impediment towards data-°ow distribution in Web services composition is that the compo- nent services cannot exchange data directly without central mediation. We propose therefore a non-intrusive approach for achieving data distri- bution among Web services that are engaged in composition, bringing minimal extensions to the underlying middleware and not tightening the coupling between them}, keywords={QoS,Web Service}, pdf={middleware.pdf}, } </bibtex>