Now showing 1 - 10 of 29
  • Publication
    Bandwidth Allocation By Pricing In ATM Networks
    (Elsevier, 1994-03) ;
    Admission control and bandwidth allocation are important issues in telecommunications networks, especially when there are random fluctuating demands for service and variations in the service rates. In the emerging broadband communications environment these services are likely to be offered via an ATM network. In order to make ATM future safe, methods for controlling the network should not be based on the characteristics of present services. We propose one bandwidth allocation method which has this property . Our proposed approach is based on pricing bandwidth to reflect network utilization, with users competing for resources according to their individual bandwidth valuations. The prices may be components of an actual tariff or they may be used as control signals, as in a private network. Simulation results show the improvement possible with our scheme versus a leaky bucket method in terms of cell loss probability, and confirm that a small queue with pricing can be efficient to multiplex heterogeneous sources.
      166
  • Publication
    Leverage of extended information to enhance the performance of JEE systems
    This paper offers an overview of the performance engineering field, including some of its latest challenges. Then, it briefly describes the research area of enhancing the performance of JEE systems through leveraging its "Extended Information" and some recent investigation trends in that front. Finally some future research ideas are presented.
      135
  • Publication
    Scalable Correlation-aware Virtual Machine Consolidation Using Two-phase Clustering
    (Institute of Electrical and Electronic Engineers (IEEE), 2015-07-24) ; ; ;
    Server consolidation is the most common and effective method to save energy and increase resource utilization in data centers, and virtual machine (VM) placement is the usual way of achieving server consolidation. VM placement is however challenging given the scale of IT infrastructures nowadays and the risk of resource contention among co-located VMs after consolidation. Therefore, the correlation among VMs to be co-located need to be considered. However, existing solutions do not address the scalability issue that arises once the number of VMs increases to an order of magnitude that makes it unrealistic to calculate the correlation between each pair of VMs. In this paper, we propose a correlation-aware VM consolidation solution ScalCCon1, which uses a novel two-phase clustering scheme to address the aforementioned scalability problem. We propose and demonstrate the benefits of using the two-phase clustering scheme in comparison to solutions using one-phase clustering (up to 84% reduction of execution time when 17, 446 VMs are considered). Moreover, our solution manages to reduce the number of physical machines (PMs) required, as well as the number of performance violations, compared to existing correlation-based approaches.
      620Scopus© Citations 12
  • Publication
    The Role of Responsive Pricing in the Internet
    The Internet continues to evolve as it reaches out to a wider user population. The recent introduction of user-friendly navigation and retrieval tools for the World Wide Web has triggered an unprecedented level of interest in the Internet among the media and the general public, as well as in the technical community. It seems inevitable that some changes or additions are needed in the control mechanisms used to allocate usage of Internet resources. In this paper, we argue that a feedback signal in the form of a variable price for network service is a workable tool to aid network operators in controlling Internet traffic. We suggest that these prices should vary dynamically based on the current utilization of network resources. We show how this responsive pricing puts control of network service back where it belongs: with the users.
      742
  • Publication
    An Energy-efficient Mechanism for Increasing Video Quality of Service in Wireless Mesh Networks
    The continuous growth in user demand for high-quality rich media services puts pressure on Wireless Mesh Network (WMN) resources. Solutions such as those which increase the capacity of the mesh network by equipping mesh routers with additional wireless interfaces provide better Quality of Service (QoS) for video deliveries, but result in higher overall energy consumption for the network. This paper presents LBIS, a distributed solution which combines the benefits of both load-balancing and interface-shifting in order to enhance QoS levels for video services delivered over multi-hop WMNs, while maintaining low energy consumption levels within the network. Simulation-based results show very good performance of our proposed mechanism in terms of QoS metrics (delay, packet loss), Peak Signal-to Noise Ratio (PSNR) and energy consumption in mesh network topologies, and with varying video traffic loads and distributions. The results demonstrate how LBIS can increase the QoS for video deliveries by more than 30% at the cost of an insignificant increase of the overall network energy consumption compared to the WMN with multiple radio interfaces without the LBIS adaptation.
      473
  • Publication
    Towards an automated approach to use expert systems in the performance testing of distributed systems
    Performance testing in distributed environments is challenging. Specifically, the identification of performance issues and their root causes are time-consuming and complex tasks which heavily rely on expertise. To simplify these tasks, many researchers have been developing tools with built-in expertise. However limitations exist in these tools, such as managing huge volumes of distributed data, that prevent their efficient usage for performance testing of highly distributed environments. To address these limitations, this paper presents an adaptive framework to automate the usage of expert systems in performance testing. Our validation assessed the accuracy of the framework and the time savings that it brings to testers. The results proved the benefits of the framework by achieving a significant decrease in the time invested in performance analysis and testing
      445Scopus© Citations 5
  • Publication
    Reducing emergency services response time in smart cities: An advanced adaptive and fuzzy approach
    Nowadays, the unprecedented increase in road traffic congestion has led to severe consequences on individuals, economy and environment, especially in urban areas in most of big cities worldwide. The most critical among the above consequences is the delay of emergency vehicles, such as ambulances and police cars, leading to increased deaths on roads and substantial financial losses. To alleviate the impact of this problem, we design an advanced adaptive traffic control system that enables faster emergency services response in smart cities while maintaining a minimal increase in congestion level around the route of the emergency vehicle. This can be achieved with a Traffic Management System (TMS) capable of implementing changes to the road network's control and driving policies following an appropriate and well-tuned adaptation strategy. This latter is determined based on the severity of the emergency situation and current traffic conditions estimated using a fuzzy logic-based scheme. The obtained simulation results, using a set of typical road networks, have demonstrated the effectiveness of our approach in terms of the significant reduction of emergency vehicles' response time and the negligible disruption caused to the non-emergency vehicles travelling on the same road network.
      658Scopus© Citations 42
  • Publication
    National Clinical Review on the Impact of COVID-19 Restrictions on Children and Guidance on Reopening of Schools and the Normalisation of Paediatric Healthcare Services in Ireland
    (Health Service Executive, 2020-08-27) ; ;
    This National Clinical Review Document was developed in May/June 2020 following extensive consultation with Child Health Professionals with a deep and wide understanding of the needs of the child. The document has been updated in August 2020 to reflect more recent developments. It has been written to describe the impact of the COVID-19 lockdown measures on children and what needs to be done now. In essence the document explores where we have come from, where we are now, and where we should be in the coming months. It is our collective opinion that the two key adverse consequences for all children across the State are the prolonged closure of the schools and the curtailment of services to children - specifically paediatric medical services, GP services, and multidisciplinary community support services. We feel that there needs to be a recalibration of how children are catered for in this pandemic. The document provides a template for how best to address children’s needs during this difficult time. At present, children have become invisible despite the fact that they account for 25% of the country’s population. There needs to be more leadership and better co- ordination in both planning and implementation on their behalf. They need strong advocates. Children are not the face of this pandemic, but they risk being among its biggest victims. The short turnaround time between the inception and completion of the document is a reflection of our perceived urgency to set out what next must be done to halt and reverse the adverse effects of the current restrictions.
      666
  • Publication
    ABI: A mechanism for increasing video delivery quality in multi-radio Wireless Mesh Networks with Energy Saving
    Wireless Mesh Networks (WMNs) are becoming increasingly popular mostly due to their ease of deployment. One of the main drawbacks of these networks is that they suffer with respect to Quality of Service (QoS) provisioning to its clients. Equipping wireless mesh nodes with multiple radios for increasing the available bandwidth has become a common practice nowadays due to the low cost of the wireless chipsets. Even though the available bandwidth increases with each radio deployed on the mesh node, the energy consumed for transmission increases accordingly. Thus, efficient usage of the radio interfaces is a key aspect for keeping the energy consumption at low levels while keeping a high QoS level for the mesh network’s clients. In the light of the above presented aspects concerning WMNs, the contribution of this paper is two-fold: (i) ABI, a mechanism for efficient usage of the available bandwidth for the mesh nodes, and (ii) decreasing the energy consumption by activating the radios only when needed. The solution proposed is throughly evaluated and shows that the two contributions can provide good QoS and decrease the overall energy consumption.
      281Scopus© Citations 4
  • Publication
    A Fair Comparison of VM Placement Heuristics and a More Effective Solution
    (Institute of Electrical and Electronic Engineers (IEEE), 2014-06-27) ; ; ;
    Data center optimization, mainly through virtual machine (VM) placement, has received considerable attention in the past years. A lot of heuristics have been proposed to give quick and reasonably good solutions to this problem. However it is difficult to compare them as they use different datasets, while the distribution of resources in the datasets has a big impact on the results. In this paper we propose the first benchmark for VM placement heuristics and we define a novel heuristic. Our benchmark is inspired from a real data center and explores different possible demographics of data centers, which makes it suitable when comparing the behaviour of heuristics. Our new algorithm, RBP, outperforms the state-of-the-art heuristics and provides close to optimal results quickly.
      494Scopus© Citations 11