Pubs:2009

<bibtex> @inproceedings{229, author={Vasken Genc; Sean Murphy; John Murphy}, title={Analysis of Transparent Mode IEEE 802.16j System Performance with varying Numbers of Relays and Associated Transmit Power}, booktitle={Wireless Communications and Networking Conference (WCNC)}, year={2009}, abstract={In this paper, the system capacity of IEEE 802.16j systems operating in transparent mode is investigated under varying numbers of relays and associated transmit power. The study is based on an extended variant of an analytical model defined in previous work and used to determine the throughput gain that can be achieved under a max-min fairness constraint. The study finds that significant overall throughput gains can be achieved over 802.16e systems: 125% and 55% gain with and without spatial reuse, respectively. However, the overall throughput gain drops as the transmit power at the relays (RSs) decreases despite the fact that a greater number of concurrent transmissions can be achieved due to less interference among the RSs’ transmissions. Decreasing the transmit power at the RSs eventually leads to a significant reduction of the achievable throughput gain even though a large number of RSs are deployed in scenarios with or without spatial reuse.}, keywords={IEEE 802.16j, performance gain, transparent}, pdf={Vasken-wcnc-09.pdf}, } </bibtex> <bibtex> @inbook{232, author={Yang Yu; Vasken Genc; Sean Murphy; Liam Murphy}, title={Network Planning for IEEE 802.16j Relay Networks}, publisher={WiMAX Network Planning and Optimization }, year={2009}, abstract={In this chapter, a problem formulation for determining optimal node location for Base Stations (BSs) and Relay Stations (RSs) in relay-based 802.16 networks is developed. A number of techniques are proposed to solve the resulting Integer Programming (IP) problem - these are compared in terms of the time taken to find a solution and the quality of the solution obtained. Finally, there is some analysis of the impact of the ratio of Base Station (BS)/Relay Station (RS) costs on the solutions obtained. Three techniques are studied to solve the IP problem: (1) a standard branch and bound mechanism, (2) an approach in which state space reduction techniques are applied in advance of the branch and bound algorithm and (3) a clustering approach in which the problem is divided into a number of sub-problems which are solved separately, followed by a final overall optimisation step. These different approaches were used to solve the problem. The results show that the more basic approach can be used to solve problems for small metropolitan areas; the state space reduction technique reduces the time taken to ¯nd a solution by about 50%. Finally, the clustering approach can be used to find solutions of approximately equivalent quality in about 30% of the time required in the first case. After the scalability tests were performed, some rudimentary experiments were performed in which the ratio of BS/RS cost was varied. The initial results show that for the scenarios studied, reducing the RS costs results in more RSs in the solution, while also decreasing the power required to communicate from the mobile device to its closest infrastructure node (BS or RS).}, keywords={relay planning}, } </bibtex> <bibtex> @inproceedings{472, author={Mikolá? Janota; Fintan Fairmichael; Viliam Holub; Radu Grigore; Julien Charles; Dermot Cochran; Joseph Kiniry}, title={CLOPS: A DSL for Command Line Options}, booktitle={IFIP Working Conference on Domain Specific Languages}, year={2009}, abstract={Programmers often write custom parsers for the command line input of their programs. They do so, in part, because they believe that both their program’s parameterization and their option formats are simple. But as the program evolves, so does the parameterization and the available options. Gradually, option parsing, data structure complexity, and maintenance of related program documentation becomes unwieldy. This article introduces a novel DSL called CLOPS that lets a programmer specify command line options and their complex inter-dependencies in a declarative fashion. The DSL is supported by a tool that generates the following features to support command line option processing: (1) data structures to represent option values, (2) a command line parser that performs validity checks, and (3) command line documentation. We have exercised CLOPS by specifying the options of a small set of programs like ls, gzip, and svn which have complex command line interfaces. These examples are provided with the Open Source release of the CLOPS system.}, keywords={CLOPS, comman line options}, pdf={JanotaEtAl09.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> @inproceedings{254, author={Bogdan Ciubotaru; Gabriel–Miro Muntean}, title={Smooth Adaptive Soft Handover Algorithm for Multimedia Streaming over Wireless Networks}, booktitle={IEEE Wireless Communications & Networking Conference (WCNC)}, year={2009}, abstract={Inter-network mobility is achieved by allowing a mobile node to change its point of attachment to the network while preserving connectivity to its corresponding nodes. Most handover solutions proposed in the literature directly change the whole data flow from one network to another relying on only one network to transfer the entire data stream. These solutions involve a certain amount of quality degradation due to increasing loss and delay and suffer in terms of scalability, efficient resource allocation and resilience to different mobile node speeds. This paper proposes the Smooth Adaptive Soft-Handover Algorithm (SASHA) which increases the quality of the multimedia delivery process when performing handover in heterogeneous wireless environment by gracefully transferring the load from one connection to the other. }, keywords={Heterogeneous mobile networks, Handover, Load balance, Multimedia streaming}, pdf={Ciubotaru_Muntean_WCNC_09.pdf}, } </bibtex> <bibtex> @inproceedings{256, author={Vasile Horia Muntean and Gabriel-Miro Muntean}, title={A Novel Adaptive Multimedia Delivery Algorithm for Increasing User Quality of Experience during Wireless and Mobile E-learning}, booktitle={IEEE International Symposium on Broadband Multimedia Systems and Broadcasting (BMSB)}, year={2009}, abstract={Multimedia content is distributed via all types of networks to viewers found in a variety of locations and using different types of devices. Increasing the performance of multimedia stream delivery requires overcoming many technological challenges, all of them having a direct effect on the user perceived quality of experience. The quality of experience influences in turn the quality of any e-learning process. This is as users in general and learners in particular are becoming increasingly quality-aware in their expectations. Therefore delivering a good quality video stream as a part of any e-learning process is very important. This paper proposes a new adaptive multimedia delivery algorithm which can be used in the context of e-learning. The Dynamic Quality Oriented Adaptation Scheme (D-QOAS) adapts the multimedia content sent based on both user preferences and network conditions, while adjusting dynamically its adaptation policy during delivery. Simulation results show that for different user profiles and various network conditions the improvement in end-user perceived quality is significant. Important benefits are obtained in terms of the total number of simultaneous users and in the link utilization, as well as in quality as measured by some video quality metrics.}, keywords={dynamic content adaptation, e-learning, multimedia, rate control, wireless networks}, } </bibtex> <bibtex> @inproceedings{259, author={Brid Kilbane; Sabine Moebs; Jennifer McManis}, title={Learning Styles or Not? A Classroom Experience}, booktitle={EdTech 2009 - the Irish Educational Technology Users' Conference}, year={2009}, abstract={Secondary Teacher Assistant Researchers (STARs) is a program of Science Foundation Ireland (SFI) that supports research collaboration between secondary school teachers and SFI funded scientists and engineers. The main idea of the program is to disseminate new skills and knowledge to teachers, which can be passed on to their students, by providing them an opportunity to work in a research laboratory. The goal of the project “Social Media to Support Learning Styles of Secondary Students in the Junior Cycle” was to explore whether a blended learning setting consisting of online learning materials matching different learning styles in addition to a face-to-face class results in a significant impact on the learning results.}, keywords={learning styles, blended learning, social media}, pdf={poster_Kilbane_moebs_mcmanis_final_090501.pdf}, } </bibtex> <bibtex> @inproceedings{260, author={Andreea Molnar; Cristina Hava Muntean}, title={Enhancing Domain Model with Performance Oriented Metadata for Adaptive E-learning Systems }, booktitle={EdTech}, year={2009}, abstract={Due to the increasing complexity of web site navigation, but also as a response to the “one size fits all” approach, adaptation mechanisms have emerged and have started to be used by a large number of on-line educational systems. As educational content may be delivered though various types of networks that differ in characteristics and vary with the time, the quality of the transmitted information is affected. PAMAH (Performance-Aware Multimedia-based Adaptive Hypermedia) proposes to overcome this barrier by taking into consideration in the personalisation process not only the classic learner profile but also the performance of the network connection used by the learner, when rich media content is delivered. This paper focuses on presenting performance oriented metadata required for modelling the educational content and for enhancing the adaptation process. The goal is to provide a personalised media rich content suitable for the learner network connection. }, keywords={Adaptive and personalized e-learning, domain modelling, multimedia }, pdf={Enhancing Domain Model with Performance Oriented Metadata for Adaptive E-learning Systems.pdf}, } </bibtex> <bibtex> @inproceedings{261, author={Andreea Molnar; Cristina Hava Muntean}, title={Performance Aware and Cost Oriented Adaptive e-Learning Framework}, booktitle={IADIS International Conference e-Learning}, year={2009}, abstract={Nowadays learners have access to multiple wireless networks from the same hand held device challenging them to choose the best network in terms of cost and performance. However, the Internet billing plans are still difficult to understand, predict and control by most users. This paper presents a user oriented adaptive e-learning framework which takes into consideration: (i) the learner profile when content adaptation is done, (ii) user device that can have multiple wireless connections with different characteristics, (iii) how much the learner is willing to pay, and (iv) the network delivery performance. The goal is to ensure that the learner gets educational content that best suits his/her profile and that content will be delivered over the network which assures the best delivery performance, maintaining also a small price for getting the requested information.}, keywords={adaptive and personalised e-learning, wireless connectivity, budget, framework, user modelling}, pdf={Performance Aware And Cost Oriented Adaptive e-Learning Framework.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> @inproceedings{340, author={Genc,V.;Murphy,S.;Murphy,J.}, title={System-Level Performance Evaluation of Multi-Cell Transparent Mode Relay 802.16j Systems}, booktitle={IEEE Globecom 2009}, year={2009}, abstract={In this paper, the system capacity of a multi-cell IEEE 802.16j system operating in transparent mode is investigated. A previous published analytical model is used and incorporates interference from neighbouring cells. The model can be used to determine downlink performance under max-min fairness constraints for both sectored and omnidirectional systems with different amounts of relays. The study provides guidelines on the design of 802.16j systems operating in transparent mode – specifically, how to maximise throughput for such systems. It is shown that inter-cell interference from relays is limited in a suburban environment and that relays can deliver significant gains over single hop systems: gains of 30% and 60% can be achieved without and with spatial reuse in an omnidirectional system while 15% and 25% in a sectorised system.}, keywords={IEEE 802.16j, transparent relay, multicell, interference, spatial reuse, performance}, pdf={system level.pdf}, } </bibtex> <bibtex> @inproceedings{341, author={Holub,V.;Parsons,T.;O'Sullivan,P.;Murphy,J.}, title={Run-Time Correlation Engine for System Monitoring & Testing}, booktitle={IEEE International Conference on Autonomic Computing(ICAC-09)}, year={2009}, abstract={Today’s enterprise applications can produce vast amounts of information both during system testing and in production. Correlation of this information can be difficult as it is generally stored in a range of different event logs, the format of which can be application or vendor specific. Furthermore these large logs can be physically distributed across a number of different locations. As a result it can be difficult to form a coherent understanding of the overall system behaviour. This has implications for a number of domains (e.g. autonomic computing, system testers), where an understanding of the system behaviour at run-time is required (e.g. for problem determination, autonomic management etc.) This paper presents an approach and implementation of run-time correlation of large volumes of log data and symptom matching of known issues in the context of large enterprise applications. Our solution provides for automatic data collection, data normalisation into a common format, run-time correlation and analysis of the data to give a coherent view of system behaviour at run-time and a symptom matching mechanism that can identify known errors in the correlated data on the fly.}, keywords={System Monitoring and Testing, Event Correlation, Event Filtering}, pdf={real time.pdf}, } </bibtex> <bibtex> @inproceedings{342, author={Fallon,E.;Murphy,L.;Murphy,J.}, title={Optimising Metropolitan Area Wireless Path Selection using Media Independent Handover}, booktitle={International Workshop on Cross Layer Design}, year={2009}, abstract={The Stream Control Transmission Protocol (SCTP) is a transport layer protocol which can support mobility through its multi-homing feature. SCTP's mobility support can be subdivided into 2 areas: path performance evaluation and switch implementation. As a transport layer protocol, SCTP's path performance evaluation is limited by its end-to-end network view. In modern heterogeneous networks, it is likely that the wireless access element of an end-to-end association is the point of performance degradation. SCTP's adherence to protocol boundaries abstracts the precision and meaning of performance metrics. In this paper, we analyze how the emerging cross layer switch management approach, Media Independent Handover (MIH), can be used to optimize path selection for metropolitan area wireless broadband networks. In such an environment line of sight can easily be obstructed, causing temporary path communication failure. We investigate how Received Signal Strength (RSS) can be used as a performance indicator, which triggers MIH path migration events in such a scenario. Results are presented which illustrate that our MIH based approach has significant performance improvement over standard SCTP strategies.}, keywords={cross layer, MIH, SCTP, mobility, WiMax}, pdf={optimising.pdf}, } </bibtex> <bibtex> @inproceedings{343, author={Nowak,D.;Murphy,J.;Perry,P.}, title={Bandwidth Allocation in DiffServ Enabled Ethernet Passive Optical Networks}, booktitle={IET Communications}, year={2009}, abstract={Ethernet Passive Optical Networks (EPONs) have attracted consider- able attention from industry as they offer a simple, highly flexible and cost effective solution to the problem of providing broadband access to a customer. In this paper, a new approach to bandwidth allocation in EPONs is presented where the Optical Line Terminator (OLT) has full control over the access mechanism. This results in much simpler Optical Network Unit (ONU) architecture. It is shown in this paper that such an OLT-centric architecture offers full support for Differentiated Services and makes enforcement of Service Level Agreements possible. Extensive simulation experiments show that bandwidth allocation algorithms deployed in such a central- ized environment can deliver good performance in terms of average and maximum packet delay. In this paper two new algorithms are introduced that target SLA- aware EPONs and provide a good protection of offered quality of service against interference from other sources.}, keywords={Ethernet,LAN}, pdf={bandwidth allocation.pdf}, pdf={optimising.pdf}, } </bibtex> <bibtex> @inproceedings{407, author={S.Fallon;P.Jacob;Y.Qiao;L.Murphy}, title={An Adaptive Optimized RTO Algorithm for Multi-Homed Wireless Environments}, booktitle={7th International Conference on Wired/Wireless Internet Communications}, year={2009}, abstract={As a transport layer protocol SCTP uses end to end metrics, such as Retransmission Time Out (RTO), to manage mobility handover. Our investigation illustrates that Wireless LAN (WLAN) mobility causes continuously increased Round Trip Times (RTT) resulting from 802.11 MAC retransmissions, regardless of the service specified by upper layers. We present scenarios where the current understanding of SCTP switchover aggressiveness is invalid; spurious failovers together with excessive RTO result in new forms of receiver buffer blocking communication failure. Given wireless mobility performance issues, together with the ambiguity of end to end metrics, we propose an Adaptive Optimized RTO algorithm for wireless Access Networks (AORAN) which uses local as well as end to end metrics to manage mobility. AORAN measures RTT between the mobile node and Access Point (AP) to calculate wireless and Internet RTO subcomponents. We also show binary exponential backoff has negative effects on SCTP with increased wireless RTT; AORAN introduces a decision mechanism which implements backoff on RTO subcomponents only when appropriate.}, keywords={SCTP, mobility, multi-homing, failover, receiver buffer blocking}, pdf={adaptive.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> @inproceedings{449, author={C.Xu;E.Fallon;Y.Qiao;Gabriel-Miro Muntean;X.Li;A.Hanley}, title={Analysis of Real-Time Multimedia Transmission over PR-SCTP with Failover Detection Delay & Reliablity Level Diffrential}, booktitle={IEEE International Conference on Communication Software & Networks}, year={2009}, abstract={The growing availability of different wireless access technologies provides the opportunity for real-time distribution of multimedia content using multi-homing technology. Investigating the behaviors and quality of such applications under heavy network load is necessary. This paper studies the effect of path failure detection threshold and reliability level on Stream Control Transmission Protocol Partial Reliability Extension (PR-SCTP) performance in symmetric and asymmetric path conditions respectively with different path loss rates. The platform Evalvid-SCTP implemented in the University of Delaware’s SCTP ns-2 module performs the emulation experiment.}, keywords={Real-time; PR-SCTP; Evalvid-SCTP}, } </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> @inproceedings{460, author={G.Cunningham;P.Perry;J.Murphy;L.Murphy}, title={Seamless Handover of IPTV Streams in a Wireless LAN Network}, booktitle={}, year={2009}, abstract={A robust mechanism to enable seamless handover of streamed IPTV in a WLAN is presented. Handover in a wireless network is usually based on signal strength measurements, but that approach does not consider levels of congestion within the network. Here, the case of stationary nodes with varying levels of network congestion is considered. A scheme that analyses the jitter is used to establish the relationship between congestion and loss in WLANs. This Moving Average of Negative Jitter is used as the basis of a handover scheme which can minimize loss. The handover scheme uses a client with two simultaneous connections to the same server through two separate WLANs, and it is shown that the client can compare the jitter in 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 in a live WLAN environment. The test scenario used is aimed at “Over-The-Top” service delivery, but the core algorithm is expected to be more broadly applicable.}, keywords={IPTV, Handover, Streamed Video, Wireless LAN1.}, pdf={seamless.pdf}, } </bibtex> <bibtex> @inproceedings{461, author={S.Fallon;P.Jacob;Y.Qiao;A.Hanley;L.Murphy}, title={Using 802.11 MAC Retransmission for Path Selection in Multi-Homed Transport Layer Protocols}, booktitle={IEEE Globecom}, year={2009}, abstract={The Stream Transmission Control Protocol(SCTP)is a transport layer protocol which can support mobility through its multi-homing feature. One of the key parameters used by SCTP to manage path selection is Retransmission Time Out(RTO).We illustrate that SCTP evaluation of underlying paths using end to end metrics,results is the calculation of excessive RTO for degraded wireless paths.}, keywords={SCTP,RTO,MAC Retransmissions,Mobility}, pdf={using 802.11.pdf}, } </bibtex> <bibtex> @inproceedings{462, author={C.Lamoriniere;A.Nafaa;L.Murphy}, title={Dynamic Switching Between Adaptive FEC Protocols For Multi-Source Streaming}, booktitle={}, year={2009}, abstract={Multi-source streaming is essential for the design of a large-scale P2P streaming architecture. In this paper, we focus on improving the dependability of multi-source video streaming as an alternative to the more prevalent point-to-point streaming. We have designed and implemented a dynamic FEC (D-FEC) protocol for multi-source video streaming. Our D-FEC protocol has the ability to dynamically switch between 4 different FEC techniques to adapt to varying network conditions. A comprehensive performance evaluation was performed with a full-scale system prototype that gives insights into the behavior of the different adaptive FEC schemes, and shows the feasibility of the concept of switching FEC schemes during a streaming session. Guidelines are given in order to best design a FEC protocol switching strategy taking into account the experienced loss rate, the loss burstiness, and the original video stream rate.}, keywords={P2P,FEC,Multi-Source Streaming}, pdf={dynamic switching.pdf}, } </bibtex> <bibtex> @inproceedings{463, author={Y.Yu;S.Murphy;L.Murphy}, title={Interference Aware Relay Station Location Planning for IEEE 802.16j Mobile Multi-Hop Relay Networks}, booktitle={12th ACM International Conference on Modeling Analysis & Simulation of Wireless & Mobile Systems}, year={2009}, abstract={In this paper, an interference aware algorithm for multi-cell Relay Station (RS) location planning problem is proposed in order to investigate the capacity gains possible using transparent mode 802.16j. The study focuses on the problem of determining the best choice of locations for RS from a given set of candidate sites - Base Station (BS) and Subscriber Station (SS) locations are assumed given. The proposed algorithm evaluates each RS based on the channel conditions of the links between the RS and its surrounding Subscriber Stations(SS) and the throughput gain it could deliver, taking into account co-channel interference. The performance statistics were collected over a large amount of experiments with many different configurations, including Base Station(BS) antenna types, number of candidate RS sites, RS transmitting power, with/without spatial reuse, etc. The results can be divided into two sections. Firstly, the algorithm was tested for optimality and scalability and was shown to perform well compared to classical Integer Programming solution techniques. Secondly, the results generated by the algorithm when applied to different scenarios were analyzed. Results show that using spatial reuse could achieve a much higher throughput gain, 3-5 time, then without using spatial reuse, although sectorised BS antenna limits the separation of co-channel RSs in a sector. The results demonstrate the characteristics of the trade-off between number of RSs and throughput gain for different configurations.}, keywords={IEEE 802.16j, Spatial Reuse, Network Planning, Relay Station Location Problem}, pdf={interference aware.pdf}, } </bibtex> <bibtex> @inproceedings{467, author={C.Thorpe;S.Murphy;L.Murphy}, title={IEEE802.11k Enabled Adaptive Physical Carrier Sense Mechanism for Wireless Networks(K-APCS)}, booktitle={12th ACM International Conference on Modeling,Analysis & Simulation of Wireless & Mobile Systems}, year={2009}, abstract={The existence of hidden and exposed nodes can have a significantly negative impact on the performance of IEEE802.11 networks. Such nodes can increase the probability of collisions and limit the spatial reuse on the channel. The value of the Physical Carrier Sensing Threshold (PCST) is instrumental to the trade-off between the number of hidden and exposed nodes in a system. This paper presents a new adaptive physical carrier sensing mechanism for wireless networks. The K-APCS algorithm maximizes the aggregate system throughput by optimizing the balance between the spatial reuse and the collision rate of a system. It incorporates 802.11k radio resource measurements and a frame loss bound on each node to enable the on-line tuning of the PCST. Simulations were performed on five variants of carrier sensing mechanisms; results show that K-APCS achieves the maximum spatial reuse with a throughput gain of 28% and the minimum collision rate with a decrease of 0.01%.}, keywords={Performance optimization, Algorithm design, Simulation}, pdf={christina_mswim09-poster_PM2HW2N.pdf}, } </bibtex> <bibtex> @inproceedings{468, author={Scotton, J.; Moebs, S,; McManis, J.; Cristea, A.I.}, title={A Case Study on Merging Strategies for Authoring QoE-based Adaptive Hypermedia}, booktitle={ECTEL 2009}, year={2009}, abstract={This paper describes recent work on strategy merger development in the authoring process of adaptive hypermedia. The goal of a merging strategy is to break a complex adaptation decision into a number of simpler ones which may be reused more easily and applied in different orders. To demonstrate the proposed method we present an example case study and sample strategies written in the LAG language. The case study is based on a recently proposed model for Quality of Experience in e-learning. This model exposes the complex interaction between a number of factors affecting QoE and hence presents a good candidate for the application of a strategy merger. Finally some evaluation points are identified, a conclusion is drawn and next steps are outlined.}, keywords={LAG, Quality of Experience, Quality of Service, Multimedia Learning, Educational Adaptive Hypermedia, Adaptation, Strategy merger}, pdf={A3H09Paper_FinalPostReviewChanges_ScottonMoebsMcManisCristea.pdf}, } </bibtex> <bibtex> @inproceedings{469, author={Andreea Molnar; Cristina Hava Muntean}, title={Billing Issues when Accessing Personalised Educational Content}, booktitle={China-Ireland International Conference on Information and Communications Technologies (CIICT 2009)}, year={2009}, abstract={The increased affordability of mobile devices combined with the availability of the latest wireless technologies have made mobile devices an attractive tool for learning. Nowadays learners can choose between multiple wireless networks with different characteristics, belonging to the same or to different mobile operators. Unfortunately, the Internet billing plans are still difficult to predict and control by most users. This paper presents an algorithm which aims to determine the best network, from a list of available ones (in terms of price), for delivering the selected educational content.}, keywords={cost, mobile data billing plan, mobile learning, adaptive and personalised learning}, } </bibtex> <bibtex> @inproceedings{470, author={Andreea Molnar; Cristina Hava Muntean}, title={QoE-MOT – A Learner Quality of Experience- Oriented Authoring Tool}, booktitle={European Conference on Technology Enhanced Learning, A3H: 7th International Workshop on Authoring of Adaptive and Adaptable Hypermedia}, year={2009}, abstract={This paper introduces Quality of Experience My Online Teacher (QoE-MOT), a user quality of experience oriented version of the generic authoring tool MOT. QoE-MOT is an authoring tool which enables the creation of performance-aware adaptive courses, by adapting the educational content to the learner network conditions. MOT was developed based on LAOS, a complex five layer authoring model. In similar fashion, QoE-MOT was constructed following the QoE-LAOS, a learner quality of experience oriented authoring model. This paper illustrates how an adaptive educational course has been enhanced with performance oriented metadata and how this metadata and QoE parameters are used during the adaptation process.}, keywords={Authoring tool, Adaptive e-learning, LAOS, QoE, MOT, LAG}, pdf={QoE-MOT.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> @inproceedings{476, author={Sebastian Robitzsch; Christian Niephaus; John Fitzpatrick; Mathias Kretschmer}, title={Measurements and Evaluations for an IEEE 802.11a Based Carrier-Grade Multi-radio Wireless Mesh Network Deployment}, booktitle={Wireless and Mobile Communications, 2009. ICWMC '09}, year={2009}, abstract={Although there currently exists a number of Wireless Local Area Network based mesh network deployments most have been deployed to provide best effort broadband Internet access. Consequently, they cannot meet the requirements of network operators in order to utilise these networks to offer carrier grade services. The goal of providing carrier grade services over a wireless mesh infrastructure requires high performance in terms of throughput and reliability. One way of achieving this increase in performance is to utilise multi-radio Mesh Nodes, however, due to the Physical Layer layer limitations of 802.11a this can have significant problems. This paper analyses these issues and investigates what performance can be expected when frequency multiplexing is considered. The results presented in this paper are based on real measurements taken from multi-radio Mesh Nodes and are evaluated using statistical algorithms. The main contribution of this paper is an analysis of the impact of the Adjacent Channel Interference effect in 802.11a based multi-radio Mesh Nodes.}, keywords={802.11a, Measurement, Multi- Radio, Wireless Mesh Network, Wireless LAN }, pdf={ICWMC2009.pdf}, } </bibtex>