A Survey of Medium Access Mechanisms for Providing QoS in Ad-Hoc Networks

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Implementing Institute of Electrical and Electronics Engineers (IEEE) 802.11 Standard Medium Access Control Protocol for Wireless Local Area Networks (LANS) on a Laboratory Hardware Prototype

Wireless Local Area Networks (LANs) are extremely convenient, flexible, and easy to deploy. All LANs in which multiple hosts must access the same medium use a Medium Access Control (MAC) protocol to coordinate channel access. The MAC is part of the Data Link Layer of the Open Systems Interconnection (OSI) Reference Model. One MAC protocol in extensive use today is the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. Since IEEE 802.11 devices are so prevalent in today s world, many researcher are exploring modifications and enhancements to the protocol. There are several well developed analytical and simulation models for IEEE 802.11 available to researchers, yet one significant obstacle remains: the lack of a means to obtain experimental data based on proposed protocol changes. Without real world experimental data, researchers lack the ability to test out their proposals in a real world environment. To fill this need, this thesis created a hardware prototype from which researchers can obtain experimental data about IEEE 802.11. This hardware prototype can now be used by researchers to gain real world data on their proposed modifications to IEEE 802.11

Réseaux de communication et applications de contrôle-commande

Cette thèse se situe dans le domaine des Systèmes Commandés en Réseaux, systèmes pluridisciplinairesqui connaissent un grand développement dans le contexte technologique actuel etqui introduisent de nouveaux problèmes de recherche, en particulier, pour les communautés Automatiqueet Réseau de Communication. L objectif est de montrer l intérêt de considérer un lienbidirectionnel entre la Qualité de Contrôle (QdC) (stabilité et performance des applications decontrôle-commande) et la Qualité de Service (QdS) (retards dans les transmissions) en se focalisantsur les réseaux locaux et plus particulièrement sur l ordonnancement des trames dans la souscouche MAC où on considère des protocoles MAC de type CSMA.Notre travail se situe tout d abord dans le cadre du réseau CAN où nous faisons trois propositions.La première proposition consiste en des solutions de QdS pour des applications decontrôle-commande sur la base du concept de priorité hybride, pour l ordonnancement de trames,dans laquelle nous définissons une partie priorité dynamique qui dépend d un paramètre de QdC.Ceci permet de réaliser une relation QdC->QdS. La deuxième proposition consiste en des solutionsde QdC par une méthode de compensation de retard (maintenance des pôles dominants)ce qui permet de réaliser une relation QdS->QdC. La troisième proposition consiste à réaliserune relation QdC QdS qui assure lors de l implantation de plusieurs applications, une propriétéd équité comportementale. Nous abordons ensuite le cadre particulier des réseaux locaux sans filoù, d une part, nous définissons des protocoles MAC de type CSMA sans collision sur la basede priorités et, d autre part, nous montrons la faisabilité des idées développées dans le cadre duréseau CANThis thesis is in the field of Networked Controlled Systems, which are multidisciplinary systemsand which experience a great development in the context of the current technology andintroduce new research problems, particularly for the communities of Automatic Control andCommunication Network. The aim is to show the interest in considering a bidirectional link betweenthe Quality of Control (QoC) (stability and performance of process control applications) andQuality of Service (QoS) (delays in the transmissions) and to focus on Local Area Networks and,more particularly, on the scheduling of frames in the MAC layer in which we consider CSMAMAC protocols.Our work first concerns a CAN network where we have three proposals. The first proposalconsists of solutions for QoS, for process control applications, which are based on the conceptof hybrid priority for the frame scheduling in which we define a dynamic priority part which dependson a QoC parameter. This allows to implement a relation QoC->QoS. The second proposalconsists of QoC solutions by using a compensation method for time delays (maintenance of dominantpoles) which allows to implement a relation QoS->QoC. The third proposal consists inimplementing a relation QoS QoC that ensures, for the implementation of several applications,a fairness property. We then discuss the specific context of Wireless LANs, where, on the onehand, we define collision-free CSMA MAC protocols on the basis of priorities and, on the otherhand, we show the feasibility of the ideas developed in the CAN networkTOULOUSE-INSA-Bib. electronique (315559905) / SudocSudocFranceF

OPTIMISING APPLICATION PERFORMANCE WITH QOS SUPPORT IN AD HOC NETWORKS

The popularity of wireless communication has increased substantially over the last decade, due to mobility support, flexibility and ease of deployment. Among next generation of mobile communication technologies, Ad Hoc networking plays an important role, since it can stand alone as private network, become a part of public network, either for general use or as part of disaster management scenarios. The performance of multihop Ad Hoc networks is heavily affected by interference, mobility, limited shared bandwidth, battery life, error rate of wireless media, and the presence of hidden and exposed terminals. The scheduler and the Medium Access Control (MAC) play a vital role in providing Quality of Service (QoS) and policing delay, end-to-end throughput, jitter, and fairness for user application services. This project aims to optimise the usage of the available limited resources in terms of battery life and bandwidth, in order to reduce packet delivery time and interference, enhance fairness, as well as increase the end-to-end throughput, and increase the overall network performance. The end-to-end throughput of an Ad Hoc network decays rapidly as the hop count between the source and destination pair increases and additional flows injected along the path of an existing flow affects the flows arriving from further away; in order to address this problem, the thesis proposes a Hop Based Dynamic Fair Scheduler that prioritises flows subject to the hop count of frames, leading to a 10% increase in fairness when compared to a IEEE 802.11b with single queue. Another mechanism to improve network performance in high congestion scenarios is network-aware queuing that reduces loss and improve the end-to-end throughput of the communicating nodes, using a medium access control method, named Dynamic Queue Utilisation Based Medium Access Control (DQUB-MAC). This MAC provides higher access probability to the nodes with congested queue, so that data generated at a high rate can be forwarded more effectively. Finally, the DQUB-MAC is modified to take account of hop count and a new MAC called Queue Utilisation with Hop Based Enhanced Arbitrary Inter Frame Spacing (QU-EAIFS) is also designed in this thesis. Validation tests in a long chain topology demonstrate that DQUB-MAC and QU-EAIFS increase the performance of the network during saturation by 35% and 40% respectively compared to IEEE 802.11b. High transmission power leads to greater interference and represents a significant challenge for Ad Hoc networks, particularly in the context of shared bandwidth and limited battery life. The thesis proposes two power control mechanisms that also employ a random backoff value directly proportional to the number of the active contending neighbours. The first mechanism, named Location Based Transmission using a Neighbour Aware with Optimised EIFS for Ad Hoc Networks (LBT-NA with Optimised EIFS MAC), controls the transmission power by exchanging location information between the communicating nodes in order to provide better fairness through a dynamic EIFS based on the overheard packet length. In a random topology, with randomly placed source and destination nodes, the performance gain of the proposed MAC over IEEE 802.11b ranges from approximately 3% to above 90% and the fairness index improved significantly. Further, the transmission power is directly proportional to the distance of communication. So, the performance is high and the durability of the nodes increases compared to a fixed transmission power MAC such as IEEE 802.11b when communicating distance is shorter. However, the mechanism requires positional information, therefore, given that location is typically unavailable, a more feasible power control cross layered system called Dynamic Neighbour Aware – Power controlled MAC (Dynamic NA -PMAC)is designed to adjust the transmission power by estimating the communicating distance based on the estimated overheard signal strength. In summary, the thesis proposes a number of mechanisms that improve the fairness amongst the competing flows, increase the end-to-end throughput, decrease the delay, reduce the transmission power in Ad Hoc environments and substantially increase the overall performance of the network