93 research outputs found

    Smart PIN: utility-based replication and delivery of multimedia content to mobile users in wireless networks

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    Next generation wireless networks rely on heterogeneous connectivity technologies to support various rich media services such as personal information storage, file sharing and multimedia streaming. Due to users’ mobility and dynamic characteristics of wireless networks, data availability in collaborating devices is a critical issue. In this context Smart PIN was proposed as a personal information network which focuses on performance of delivery and cost efficiency. Smart PIN uses a novel data replication scheme based on individual and overall system utility to best balance the requirements for static data and multimedia content delivery with variable device availability due to user mobility. Simulations show improved results in comparison with other general purpose data replication schemes in terms of data availability

    Adaptive Localized Active Route Maintenance Mechanism to Improve Performance of VoIP over Ad Hoc Networks

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    An important characteristic of a mobile ad hoc network routing protocol is connectivity maintenance. The protocol’s ability to maintain routes and react to topology changes due to link failures affects the delay, packet loss, and throughput of real-time applications. However, the time required to recover from a link failure in the current AODV protocol is too long for real-time applications. The objective of this paper is to develop a mechanism to allow fast response to link breaks to enable real-time communications, such as Voice over IP. We propose AODVM-ALARM, an adaptive localized route maintenance mechanism, over an existing ad hoc multipath routing protocol. The mechanism dynamically monitors and maintains on-going communications by utilizing special control messages and packet analysis techniques to enable fast response to link breaks. The mechanism can recognize, respond and recover quickly from link breaks due to topology changes. AODV-ALARM has been tested in an ad hoc experimental testbed, and compared with AODV-UU and AODVM protocols. Results show that AODVM-ALARM significantly improves the response time to link failures and achieves an overall improvement in the network performance in terms of the failover delay, failover loss and throughput when compared with the previous ad hoc routing protocols. AODVM-ALARM which is easily deployable, fault tolerant and have a fast response to topology changes can be used to rapidly establish VoIP communications, playing a significant role in emergency response for disaster recovery when the network infrastructure might be broken.YesPeer-reviewed journal articl

    Intelligent MANET optimisation system

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    This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.In the literature, various Mobile Ad hoc NETwork (MANET) routing protocols proposed. Each performs the best under specific context conditions, for example under high mobility or less volatile topologies. In existing MANET, the degradation in the routing protocol performance is always associated with changes in the network context. To date, no MANET routing protocol is able to produce optimal performance under all possible conditions. The core aim of this thesis is to solve the routing problem in mobile Ad hoc networks by introducing an optimum system that is in charge of the selection of the running routing protocol at all times, the system proposed in this thesis aims to address the degradation mentioned above. This optimisation system is a novel approach that can cope with the network performance’s degradation problem by switching to other routing protocol. The optimisation system proposed for MANET in this thesis adaptively selects the best routing protocol using an Artificial Intelligence mechanism according to the network context. In this thesis, MANET modelling helps in understanding the network performance through different contexts, as well as the models’ support to the optimisation system. Therefore, one of the main contributions of this thesis is the utilisation and comparison of various modelling techniques to create representative MANET performance models. Moreover, the proposed system uses an optimisation method to select the optimal communication routing protocol for the network context. Therefore, to build the proposed system, different optimisation techniques were utilised and compared to identify the best optimisation technique for the MANET intelligent system, which is also an important contribution of this thesis. The parameters selected to describe the network context were the network size and average mobility. The proposed system then functions by varying the routing mechanism with the time to keep the network performance at the best level. The selected protocol has been shown to produce a combination of: higher throughput, lower delay, fewer retransmission attempts, less data drop, and lower load, and was thus chosen on this basis. Validation test results indicate that the identified protocol can achieve both a better network performance quality than other routing protocols and a minimum cost function of 4.4%. The Ad hoc On Demand Distance Vector (AODV) protocol comes in second with a cost minimisation function of 27.5%, and the Optimised Link State Routing (OLSR) algorithm comes in third with a cost minimisation function of 29.8%. Finally, The Dynamic Source Routing (DSR) algorithm comes in last with a cost minimisation function of 38.3%

    Quality of service technologies for multimedia applications in next generation networks

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    Next Generation Networks are constantly evolving towards solutions that allow the operator to provide advanced multimedia applications with QoS guarantees in heterogeneous, multi-domain and multi-services networks. Other than the unquestionable advantages inherent the ability to simultaneously handle traffic flows at different QoS levels, these architectures require management systems to efficiently perform quality guarantees and network resource utilization. These issues have been addressed in this thesis. DiffServ-aware Traffic Engineering (DS-TE) has been considered as reference architecture for the deployment of the quality management systems. It represents the most advanced technology to accomplish either network scalability and service granularity goals. On the basis of DS-TE features, a methodology for traffic and network resource management has been defined. It provides some rules for QoS service characterization and allows to implement Traffic Engineering policies with a class-based approach. A set of basic parameters for quality evaluation has been defined, that are the Key Performance Indicators; some mathematical model to derive the statistical nature of traffic have been analyzed and an algorithm to improve the fulfillment of quality of service targets and to optimize network resource utilization. It is aimed at reducing the complexity inherent the setting of some of the key parameters in the NGN architectures. Multidomain scenarios with technologies different from DS-TE have been also evaluated, defining some methodologies for network interoperability. Simulations with Opnet Modeler confirmed the efficacy of the proposed system in computing network configurations with QoS targets. With regard to QoS performance at the application level, video streaming applications in wireless domains have been particularly addressed. A rate control algorithm to adjust the rate on a per-window basis has been defined, making use of a short-term prediction of the network delay to keep the probability of playback buffer starvation lower than a desired threshold during each window. Finally, a framework for mutual authentication in web applications has been proposed and evaluated. It integrates an IBA password technique with a challenge-response scheme based on a shared secret key for image scrambling. The wireless environment is mainly addressed by the proposed system, which tries to overcome the severe constraints on security, data transmission capability and user friendliness imposed by such environment

    An improved medium access control protocol for real-time applications in WLANs and its firmware development

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    The IEEE 802.11 Wireless Local Area Network (WLAN), commonly known as Wi-Fi, has emerged as a popular internet access technology and researchers are continuously working on improvement of the quality of service (QoS) in WLAN by proposing new and efficient schemes. Voice and video over Internet Protocol (VVoIP) applications are becoming very popular in Wi-Fi enabled portable/handheld devices because of recent technological advancements and lower service costs. Different from normal voice and video streaming, these applications demand symmetric throughput for the upstream and downstream. Existing Wi-Fi standards are optimised for generic internet applications and fail to provide symmetric throughput due to traffic bottleneck at access points. Performance analysis and benchmarking is an integral part of WLAN research, and in the majority of the cases, this is done through computer simulation using popular network simulators such as Network Simulator ff 2 (NS-2) or OPNET. While computer simulation is an excellent approach for saving time and money, results generated from computer simulations do not always match practical observations. This is why, for proper assessment of the merits of a proposed system in WLAN, a trial on a practical hardware platform is highly recommended and is often a requirement. In this thesis work, with a view to address the abovementioned challenges for facilitating VoIP and VVoIP services over Wi-Fi, two key contributions are made: i) formulating a suitable medium access control (MAC) protocol to address symmetric traffic scenario and ii) firmware development of this newly devised MAC protocol for real WLAN hardware. The proposed solution shows signifocant improvements over existing standards by supporting higher number of stations with strict QoS criteria. The proposed hardware platform is available off-the-shelf in the market and is a cost effective way of generating and evaluating performance results on a hardware system

    Quality of service support for multimedia applications in mobile ad hoc networks

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    EThOS - Electronic Theses Online ServiceGBUnited Kingdo

    Nuovi protocolli per gestione dati e comunicazione Real-time in ambito agricolo

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    In the last years, Precision Farming and Farm Automation in Agricultural field, have been requesting short range wireless communication systems for machine synchronization and long range wireless communication for fleet management, and for production and task control in real time. Existing protocols can meet the requirements only partially: different legislation and product availability in different countries make it difficult to identify a solution for the global market. TCP/IP protocol and GPRS/GSM networks meet some requirements for long range communication, but not for real time communication needed for short range communication. The synchronization specifications require a real time wireless communication protocol affordable, safe and with low latency, in order to ensure a minimum guaranteed throughput apt to synchronize the machine work and travel. Moreover there are some information security requirements to fulfill in order to guarantee safe data transmission. The paper presents a comprehensive proposal based on UDP and IP protocols with embedded controls, apt to create an isochronous wireless communication for machine synchronization, and some other methods and protocols to fulfill long range data communication requirements of the Agricultural field

    Gezgin ağ yönlendirme protokolleri için DEVS tabanlı benzetim aracı tasarımı

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    06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Ad Hoc ağlar; geçici formlarda, merkezi yönetimin bulunmadığı veya geleneksel ağlardaki düzenli servis desteklerinin olmadığı gezgin düğümlerden oluşan ağlardır. Düğümler rastgele ve keyfi olarak kendilerini organize ederek hareket etmekte serbesttir. Bu yüzden ağın topolojisi hızlı ve öngörülemeyen bir şekilde değişebilir.Ad Hoc ağlar gibi dağıtık sistemler, çeşitli teknolojiler kullanarak birbirleriyle iletişim yapan birimlerden oluşur. İletişim içerisinde bulunan sistemin uyarlanabilirlik, ölçeklenebilirlik, güvenilirlik gibi bir takım niteliklere sahip olması gerekmektedir. Artan karmaşıklık ve boyut nedeniyle ortaya çıkan sorunların üstesinden gelmek amacıyla geliştirilen çeşitli yöntemler bilgisayar ağlarının ihtiyaçlarına göre kullanılmaktadır. Bu yöntemlerin tasarım ve geliştirilmesinde modelleme ve benzetim araçlarının yeri büyüktür.Kablosuz sistemler için statik topoloji üreten benzeticiler (Qualnet, Omnet++, Ns-2, Opnet, vb.) küçük ağları çalışmak için ideal platformlarken, günümüzde üstel olarak artan ağ sistemlerini modellemede ve değişken yapılı ağ sistemlerinin başarımını test etmede yetersiz kalmaktadırlar. Ayrıca, bu benzeticilerin mimarilerinin birçoğu soyutlama ve hiyerarşiden yoksun olmaları yanında çok büyük hesaplama maliyeti oluşturmaktadırlar.Sunulan tezde, gezgin sistemlerin karmaşıklık, ölçeklenebilirlik, uyum yeteneği gibi sorunlarının incelenmesi, tasarım alternatiflerinin araştırılması ve farklı çözüm yaklaşımlarının test edilebilmesi için Ayrık Olaylı Sistem Tanımı (DEVS) kullanılarak bir MANET modeli ve benzeticisi geliştirildi.Geliştirilen benzeticinin üstünlüklerini ve başarımını göstermek amacıyla farklı ölçeklerden oluşan ağlar farklı trafik yükleri altında çalıştırılarak, en yaygın yönlendirme protokollerinden olan AODV'nin başarımı incelendi. Topoloji üreteci özellikle büyük modelleri otomatik oluşturabilmek için tasarlandı ve model geçerleme testleri gerçekleştirildi. Gerçekleştirilen uygulamalardan, geliştirilen benzeticinin son derece paralel, esnek ve hızlı çalıştığını, değişik teknolojileri barındıran uygulamaları geliştirebilme yeteneğine sahip olduğu gözlemlendi. Ayrıca kullanılan yöntemin bu gibi sistemleri modellemede üstünlükleri gösterilmeye çalışıldı.Mobile ad hoc wireless networks (MANETs) are autonomous collections of mobile nodes communicating via wireless antennas. Formal verification of routing protocols for MANETs requires modeling of every part correctly to verify. The characteristics of MANETs that bring challenge to the task of modeling are node mobility, scalability and broadcast. Consequently, to cope with management of such networks in presence of ever increasing complexity, various decentralized and centralized approaches are being used to address private and public organizations demands.To bring solutions to MANET challenges , simulators generating static topology such as ns-2, Glomosim, Omnet++, Qualnet and Opnet are ideal platforms for studying small MANET networks, but incapable of modeling and testing large-scale and dynamic structured networks. Furthermore, due to lack of hierarchy and abstraction in their structure, it is difficult to create, manage and compute large models.In this study, a parallel and distributed network simulator is developed to bring solutions to MANET systems by using Discrete Event System Specification (DEVS) formalism. Developed simulator is called MANET-DEVS in which network model is defined with its components (e.g. nodes and links) and their hierarchical structure.Using the DEVS hierarchical model composition concept, we develop simulation models of networks with varying topologies and scales. For example, we will use clusters to study its impact on reducing communication and increasing performance. The explicit and hidden behaviors of these networks are observed under various experimental configurations e.g., nodes and links are assigned different capacities. Topology generator is developed and validation experiments are also done

    Quality of Service for Multimedia and Control System Applications in Mobile Ad-hoc Network

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    A Mobile Ad-Hoc Network (MANET) is a collection of randomly distributed infrastructure-less mobile nodes that form a wireless network. These Mobile nodes have the capability to act as a host or relay. As a host, the mobile nodes can be the source and/or destination of traffic, and when acting as a relay, they can be an intermediate node that forwards the traffic to its destination. Some of the challenges of a MANET include the dynamic network topology, device discovery, power constraints, wireless channel conditions and limited network resources. These challenges degrade the network performance and thus affect the network stability and robustness. Therefore, it is difficult for a MANET to attain the Quality of Service (QoS) of a wired network. This thesis aims to address the problem of the limited wireless network resources by proposing two adaptive scheduling algorithms that can adapt in real-time to the changes in the network. To achieve the aim; this thesis first analyses the behaviour of various application profiles in a queue. It models Voice, Email, and Internet Browsing traffic (by specifying packet sizes, and inter-arrival rates based on various distributions) separately and then simultaneously in a common network for uncongested and congested conditions, after which scheduling is applied in order to improve the overall network performance. The Voice traffic profile is then added to the UDP/IP protocol stack and the network performance is compared to a simple node without the UDP/IP protocol stack. A realistic wireless propagation model for the simulation is developed from a point-to-point open-field outdoor experiment. This thesis proposes two adaptive priority fuzzy based scheduler for a MANET, the priority of packets in the queue are determined based on the real-time available network resources. The methodology for transmitting a live-feed video stream over OPNET to validate the scheduler is also presented. An interface between the simulation and hardware is created to send real-time video traffic through the simulation network. This thesis concludes by showing that the performance of a MANET network can be improved by applying an adaptive scheduler
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