66 research outputs found
Advanced Wireless LAN
The past two decades have witnessed starling advances in wireless LAN technologies that were stimulated by its increasing popularity in the home due to ease of installation, and in commercial complexes offering wireless access to their customers. This book presents some of the latest development status of wireless LAN, covering the topics on physical layer, MAC layer, QoS and systems. It provides an opportunity for both practitioners and researchers to explore the problems that arise in the rapidly developed technologies in wireless LAN
Multipath routing and QoS provisioning in mobile ad hoc networks
PhDA Mobile Ad Hoc Networks (MANET) is a collection of mobile nodes that can
communicate with each other using multihop wireless links without utilizing any
fixed based-station infrastructure and centralized management. Each mobile node
in the network acts as both a host generating flows or being destination of flows
and a router forwarding flows directed to other nodes.
Future applications of MANETs are expected to be based on all-IP
architecture and be capable of carrying multitude real-time multimedia
applications such as voice and video as well as data. It is very necessary for
MANETs to have an efficient routing and quality of service (QoS) mechanism to
support diverse applications.
This thesis proposes an on-demand Node-Disjoint Multipath Routing protocol
(NDMR) with low broadcast redundancy. Multipath routing allows the
establishment of multiple paths between a single source and single destination
node. It is also beneficial to avoid traffic congestion and frequent link breaks in
communication because of the mobility of nodes. The important components of
the protocol, such as path accumulation, decreasing routing overhead and
selecting node-disjoint paths, are explained. Because the new protocol
significantly reduces the total number of Route Request packets, this results in an
increased delivery ratio, smaller end-to-end delays for data packets, lower control
overhead and fewer collisions of packets.
Although NDMR provides node-disjoint multipath routing with low route
overhead in MANETs, it is only a best-effort routing approach, which is not
enough to support QoS. DiffServ is a standard approach for a more scalable way
to achieve QoS in any IP network and could potentially be used to provide QoS
in MANETs because it minimises the need for signalling. However, one of the
biggest drawbacks of DiffServ is that the QoS provisioning is separate from the
routing process. This thesis presents a Multipath QoS Routing protocol for
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supporting DiffServ (MQRD), which combines the advantages of NDMR and
DiffServ. The protocol can classify network traffic into different priority levels
and apply priority scheduling and queuing management mechanisms to obtain
QoS guarantees
Quality of service provision in mobile multimedia - a survey
The prevalence of multimedia applications has drastically increased the amount of multimedia data. With the drop of the hardware cost, more and more mobile devices with higher capacities are now used. The widely deployed wireless LAN and broadband wireless networks provide the ubiquitous network access for multimedia applications. Provision of Quality of Service (QoS) is challenging in mobile ad hoc networks because of the dynamic characteristics of mobile networks and the limited resources of the mobile devices. The wireless network is not reliable due to node mobility, multi-access channel and multi-hop communication. In this paper, we provide a survey of QoS provision in mobile multimedia, addressing the technologies at different network layers and cross-layer design. This paper focuses on the QoS techniques over IEEE 802.11e networks. We also provide some thoughts about the challenges and directions for future research
Development of a Quality of Service Framework for Multimedia Streaming Applications
By the year 2012, it is expected that the majority of all Internet traffic will be video content. Coupled with this is the increasing availability of Wireless Local Area Networks (WLANs) due to their ease of deployment, flexibility and reducing roll out costs. Unfortunately the contention based access mechanism utilised by IEEE 802.11 WLANs does not suit the non-uniform or bursty bandwidth profile of a video stream which can lead to a reduced quality of service (QoS) being experienced by the end-user. In 2005, the IEEE 802.11e protocol was ratified in an attempt to solve this emerging problem. It provides for an access prioritization mechanism based upon four separate traffic classes or access categories (ACs). Each AC is characterised by a set of access parameters that determine its level of access priority which is turn determines the amount of bandwidth available to it. Computer simulation studies have shown that AC prioritisation can yield significant improvements in the QoS delivered over a WLAN. However, these studies have been based upon the use of static access parameters for the ACs. In practice, this is not a viable solution owing to the dynamic and unpredictable nature of the operating conditions on WLANs. In this thesis, an experimental study of AC prioritisation based upon adaptive tuning of the access parameters is presented. This new approach to bandwidth provisioning for video streaming is shown to yield significant improvements in the QoS under a wide range of different operating conditions. For example, it is shown that by adaptively tuning the access control parameters in response to the network conditions, the number of video frames delivered that satisfy QoS requirements is more than doubled
Cross-layer optimizations in multi-hop ad hoc networks
Unlike traditional wireless networks, characterized by the presence of last-mile, static and
reliable infrastructures, Mobile ad Hoc Networks (MANETs) are dynamically formed by
collections of mobile and static terminals that exchange data by enabling each other's
communication. Supporting multi-hop communication in a MANET is a challenging
research area because it requires cooperation between different protocol layers (MAC,
routing, transport). In particular, MAC and routing protocols could be considered
mutually cooperative protocol layers. When a route is established, the exposed and
hidden terminal problems at MAC layer may decrease the end-to-end performance
proportionally with the length of each route. Conversely, the contention at MAC layer
may cause a routing protocol to respond by initiating new routes queries and routing table
updates.
Multi-hop communication may also benefit the presence of pseudo-centralized virtual
infrastructures obtained by grouping nodes into clusters. Clustering structures may
facilitate the spatial reuse of resources by increasing the system capacity: at the same
time, the clustering hierarchy may be used to coordinate transmissions events inside the
network and to support intra-cluster routing schemes. Again, MAC and clustering
protocols could be considered mutually cooperative protocol layers: the clustering
scheme could support MAC layer coordination among nodes, by shifting the distributed
MAC paradigm towards a pseudo-centralized MAC paradigm. On the other hand, the
system benefits of the clustering scheme could be emphasized by the pseudo-centralized
MAC layer with the support for differentiated access priorities and controlled contention.
In this thesis, we propose cross-layer solutions involving joint design of MAC, clustering
and routing protocols in MANETs.
As main contribution, we study and analyze the integration of MAC and clustering
schemes to support multi-hop communication in large-scale ad hoc networks. A novel
clustering protocol, named Availability Clustering (AC), is defined under general nodes'
heterogeneity assumptions in terms of connectivity, available energy and relative
mobility. On this basis, we design and analyze a distributed and adaptive MAC protocol,
named Differentiated Distributed Coordination Function (DDCF), whose focus is to
implement adaptive access differentiation based on the node roles, which have been
assigned by the upper-layer's clustering scheme. We extensively simulate the proposed
clustering scheme by showing its effectiveness in dominating the network dynamics,
under some stressing mobility models and different mobility rates. Based on these results,
we propose a possible application of the cross-layer MAC+Clustering scheme to support
the fast propagation of alert messages in a vehicular environment.
At the same time, we investigate the integration of MAC and routing protocols in large
scale multi-hop ad-hoc networks. A novel multipath routing scheme is proposed, by
extending the AOMDV protocol with a novel load-balancing approach to concurrently
distribute the traffic among the multiple paths. We also study the composition effect of a
IEEE 802.11-based enhanced MAC forwarding mechanism called Fast Forward (FF),
used to reduce the effects of self-contention among frames at the MAC layer. The
protocol framework is modelled and extensively simulated for a large set of metrics and
scenarios.
For both the schemes, the simulation results reveal the benefits of the cross-layer
MAC+routing and MAC+clustering approaches over single-layer solutions
Bandwidth reservation in mobile ad hoc networks for providing QoS : adaptation for voice support
Le support de qualitĂ© de service (QoS) dans les rĂ©seaux MANETs (Mobile Ad-Hoc NETworks) a attirĂ© une grande attention ces derniĂšres annĂ©es. Bien que beaucoup de travaux de recherche ont Ă©tĂ© consacrĂ© pour offrir la QoS dans les rĂ©seaux filaires et cellulaires, les solutions de QoS pour le support du trafic temps rĂ©el dans les MANET reste l'un des domaines de recherche les plus difficiles et les moins explorĂ©s. En fait, les applications temps rĂ©el telles que la voix et la vidĂ©o ne pourrait pas fonctionner correctement dans les MANET sans l'utilisation d'un protocole de contrĂŽle d'accĂšs au support (MAC) orientĂ© QoS. En effet, les trafics temps rĂ©el demandent des exigences strictes en termes de dĂ©lai de transmission et de taux de perte de paquets qui peuvent ĂȘtre remplies uniquement si la sous-couche MAC fournit un dĂ©lai d'accĂšs au canal bornĂ©, et un faible taux de collision.
Le but de cette thĂšse est la proposition et l'analyse d'un protocole MAC basĂ© sur la rĂ©servation pour garantir la QoS dans les MANETs. Tout d'abord, nous Ă©tudions un problĂšme majeur dans la rĂ©servation de ressources dans les MANETs qui est la cohĂ©rence des rĂ©servations. Notre analyse des protocoles de rĂ©servation existant pour les MANETs rĂ©vĂšle que de nombreux conflits de rĂ©servations entre les nĆuds voisins se produisent pendant la phase d'Ă©tablissement de rĂ©servation. Ces conflits, qui sont principalement dues Ă la collision des messages de contrĂŽle de rĂ©servation, ont un impact important sur les performances du protocole de rĂ©servation, et conduisent Ă un taux de collision et de perte de paquet importants pendant la durĂ©e de vie de la connexion, ce qui n'est pas acceptable pour les trafics temps rĂ©els. Nous proposons un nouveau protocole MAC basĂ© sur la rĂ©servation qui rĂ©sout ces conflits. Le principe de notre protocole est d'Ă©tablir une meilleure coordination entre les nĆuds voisins afin d'assurer la cohĂ©rence des rĂ©servations. Ainsi, avant de considĂ©rer qu'une rĂ©servation est rĂ©ussite, le protocole s'assure que chaque message de contrĂŽle envoyĂ© par un nĆud pour Ă©tablir une rĂ©servation est bien reçu par tous ses nĆuds voisins.
Dans la deuxiÚme partie de cette thÚse, nous appliquons le protocole de réservation proposé au trafic de type voix. Ainsi, nous étendons ce protocole afin de prendre en compte les caractéristiques du trafic voix, tout en permettant le transport de trafic de données. Nous nous focalisons sur l'utilisation efficace de la bande passante et les mécanismes pour réduire le gaspillage de bande passante.
La derniĂšre partie de cette thĂšse concerne l'extension du protocole proposĂ© en vue de rĂ©server la bande passante pour une connexion temps rĂ©el sur un chemin. Ainsi, le protocole MAC de rĂ©servation proposĂ© est couplĂ© avec un protocole de routage rĂ©actif. En outre, le protocole est Ă©tendu avec des mĂ©canismes de gestion de Ă mobilitĂ© afin de faire face Ă la dĂ©gradation des performances due Ă la mobilitĂ© des nĆuds.
Nous évaluons les performances du protocole proposé dans plusieurs scénarios dans lesquels nous montrons sa supériorité par rapport aux standards existants.QoS provisioning over Mobile Ad-Hoc Networks (MANETs) has attracted a great attention in recent years. While much research effort has been devoted to provide QoS over wired and cellular networks, QoS solutions for the support of real-time traffic over MANETs remains one of the most challenging and least explored areas. In fact, real-time applications such as voice and video could not function properly on MANETs without a QoS oriented medium access control (MAC) scheme. Indeed, real-time traffics claim strict requirements in terms of transmission delay and packet dropping that can be fulfilled only if the MAC sub-layer provides bounded channel access delay, and low collision rate.
The purpose of this thesis is the proposal and analysis of an efficient reservation MAC protocol to provide QoS support over MANETs. Firstly, we study one major issue in resource reservation for MANETs which is reservation consistency. Our analysis of existing reservation MAC protocols for MANETs reveals that many reservation conflicts between neighbor nodes occur during the reservation establishment phase. These conflicts which are mainly due to collisions of reservation control messages, have an important impact on the performance of the reservation protocol, and lead to a significant collision and loss of packets during the life-time of the connection, which is not acceptable for real-time traffics. We design a new reservation MAC protocol that resolves these conflicts. The main principle of our protocol is to achieve better coordination between neighbor nodes in order to ensure consistency of reservations. Thus, before considering a reservation as successful, the protocol tries to ensure that each reservation control message transmitted by a node is successfully received by all its neighbors.
In the second part of this thesis, we apply the proposed reservation protocol to voice traffic. Thus, we extend this protocol in order to take into account the characteristics of voice traffic, while enabling data traffic. We focus on efficient bandwidth utilization and mechanisms to reduce the waste of bandwidth.
The last part of this thesis relates to the extension of the proposed protocol in order to reserve resources for a real-time connection along a path. Thus, the proposed reservation MAC protocol is coupled with a reactive routing protocol. In addition, the protocol is extended with mobility handling mechanisms in order to cope with performance degradation due to mobility of nodes.
We evaluate the performance of the proposed scheme in several scenarios where we show its superiority compared to existing standards
Proceedings of the Third Edition of the Annual Conference on Wireless On-demand Network Systems and Services (WONS 2006)
Ce fichier regroupe en un seul documents l'ensemble des articles accéptés pour la conférences WONS2006/http://citi.insa-lyon.fr/wons2006/index.htmlThis year, 56 papers were submitted. From the Open Call submissions we accepted 16 papers as full papers (up to 12 pages) and 8 papers as short papers (up to 6 pages). All the accepted papers will be presented orally in the Workshop sessions. More precisely, the selected papers have been organized in 7 session: Channel access and scheduling, Energy-aware Protocols, QoS in Mobile Ad-Hoc networks, Multihop Performance Issues, Wireless Internet, Applications and finally Security Issues. The papers (and authors) come from all parts of the world, confirming the international stature of this Workshop. The majority of the contributions are from Europe (France, Germany, Greece, Italy, Netherlands, Norway, Switzerland, UK). However, a significant number is from Australia, Brazil, Canada, Iran, Korea and USA. The proceedings also include two invited papers. We take this opportunity to thank all the authors who submitted their papers to WONS 2006. You helped make this event again a success
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