486 research outputs found
Medium Access Control Protocols for Ad-Hoc Wireless Networks: A Survey
Studies of ad hoc wireless networks are a relatively new field gaining more popularity for various new applications. In these networks, the Medium Access Control (MAC) protocols are responsible for coordinating the access from active nodes. These protocols are of significant importance since the wireless communication channel is inherently prone to errors and unique problems such as the hidden-terminal problem, the exposed-terminal problem, and signal fading effects. Although a lot of research has been conducted on MAC protocols, the various issues involved have mostly been presented in isolation of each other. We therefore make an attempt to present a comprehensive survey of major schemes, integrating various related issues and challenges with a view to providing a big-picture outlook to this vast area. We present a classification of MAC protocols and their brief description, based on their operating principles and underlying features. In conclusion, we present a brief summary of key ideas and a general direction for future work
MAC Protocols for Wireless Mesh Networks with Multi-beam Antennas: A Survey
Multi-beam antenna technologies have provided lots of promising solutions to
many current challenges faced in wireless mesh networks. The antenna can
establish several beamformings simultaneously and initiate concurrent
transmissions or receptions using multiple beams, thereby increasing the
overall throughput of the network transmission. Multi-beam antenna has the
ability to increase the spatial reuse, extend the transmission range, improve
the transmission reliability, as well as save the power consumption.
Traditional Medium Access Control (MAC) protocols for wireless network largely
relied on the IEEE 802.11 Distributed Coordination Function(DCF) mechanism,
however, IEEE 802.11 DCF cannot take the advantages of these unique
capabilities provided by multi-beam antennas. This paper surveys the MAC
protocols for wireless mesh networks with multi-beam antennas. The paper first
discusses some basic information in designing multi-beam antenna system and MAC
protocols, and then presents the main challenges for the MAC protocols in
wireless mesh networks compared with the traditional MAC protocols. A
qualitative comparison of the existing MAC protocols is provided to highlight
their novel features, which provides a reference for designing the new MAC
protocols. To provide some insights on future research, several open issues of
MAC protocols are discussed for wireless mesh networks using multi-beam
antennas.Comment: 22 pages, 6 figures, Future of Information and Communication
Conference (FICC) 2019, https://doi.org/10.1007/978-3-030-12388-8_
Link Availability Aware Routing Metric For Wireless Mesh Networks
International audienceThis paper investigates the design of effective routing metrics in the purpose of network resources optimization and the satisfaction of users QoS requirements. Using several real experiments, we point out the shortcoming of the Expected Transmission Count (ETX) metric for eventual optimizations towards a more efficient routing. Experiments were carried out into an heterogeneous IEEE 802.11n based network running with OLSR routing protocol and have shown that ETX presents several shortcoming resulting in inaccurate estimation of the link quality and then of the routing decision. This paper presents improvements of the ETX metric based on link availibility for accurately finding high-throughput paths in multihop wireless mesh networks
Design and evaluation of wireless dense networks : application to in-flight entertainment systems
Le rĂ©seau sans fil est l'un des domaines de rĂ©seautage les plus prometteurs avec des caractĂ©ristiques uniques qui peuvent fournir la connectivitĂ© dans les situations oĂč il est difficile d'utiliser un rĂ©seau filaire, ou lorsque la mobilitĂ© des nĆuds est nĂ©cessaire. Cependant, le milieu de travail impose gĂ©nĂ©ralement diverses contraintes, oĂč les appareils sans fil font face Ă diffĂ©rents dĂ©fis lors du partage des moyens de communication. De plus, le problĂšme s'aggrave avec l'augmentation du nombre de nĆuds. DiffĂ©rentes solutions ont Ă©tĂ© introduites pour faire face aux rĂ©seaux trĂšs denses. D'autre part, un nĆud avec une densitĂ© trĂšs faible peut crĂ©er un problĂšme de connectivitĂ© et peut conduire Ă l'optension de nĆuds isolĂ©s et non connectes au rĂ©seau. La densitĂ© d'un rĂ©seau est dĂ©finit en fonction du nombre de nĆuds voisins directs au sein de la portĂ©e de transmission du nĆud. Cependant, nous croyons que ces mĂ©triques ne sont pas suffisants et nous proposons une nouvelle mesure qui considĂšre le nombre de voisins directs et la performance du rĂ©seau. Ainsi, la rĂ©ponse du rĂ©seau, respectant l'augmentation du nombre de nĆuds, est considĂ©rĂ©e lors du choix du niveau de la densitĂ©. Nous avons dĂ©fini deux termes: l'auto-organisation et l'auto-configuration, qui sont gĂ©nĂ©ralement utilisĂ©s de façon interchangeable dans la littĂ©rature en mettant en relief la diffĂ©rence entre eux. Nous estimons qu'une dĂ©finition claire de la terminologie peut Ă©liminer beaucoup d'ambiguĂŻtĂ© et aider Ă prĂ©senter les concepts de recherche plus clairement. Certaines applications, telles que Ies systĂšmes "In-Flight Entertainment (IFE)" qui se trouvent Ă l'intĂ©rieur des cabines d'avions, peuveut ĂȘtre considĂ©rĂ©es comme des systĂšmes sans fil de haute densitĂ©, mĂȘme si peu de nĆuds sont relativement prĂ©sents. Pour rĂ©soudre ce problĂšme, nous proposons une architecture hĂ©tĂ©rogĂšne de diffĂ©rentes technologies Ă fin de surmonter les contraintes spĂ©cifiques de l'intĂ©rieur de la cabine. Chaque technologie vise Ă rĂ©soudre une partie du problĂšme. Nous avons rĂ©alisĂ© diverses expĂ©rimentations et simulations pour montrer la faisabilitĂ© de l'architecture proposĂ©e. Nous avons introduit un nouveau protocole d'auto-organisation qui utilise des antennes intelligentes pour aider certains composants du systĂšme IFE; Ă savoir les unitĂ©s d'affichage et leurs systĂšmes de commande, Ă s'identifier les uns les autres sans aucune configuration prĂ©liminaire. Le protocole a Ă©tĂ© conçu et vĂ©rifiĂ© en utilisant le langage UML, puis, un module de NS2 a Ă©tĂ© crĂ©Ă© pour tester les diffĂ©rents scĂ©narios.Wireless networking is one of the most challenging networking domains with unique features that can provide connectivity in situations where it is difficult to use wired networking, or when ! node mobility is required. However, the working environment us! ually im poses various constrains, where wireless devices face various challenges when sharing the communication media. Furthermore, the problem becomes worse when the number of nodes increase. Different solutions were introduced to cope with highly dense networks. On the other hand, a very low density can create a poor connectivity problem and may lead to have isolated nodes with no connection to the network. It is common to define network density according to the number of direct neighboring nodes within the node transmission range. However, we believe that such metric is not enough. Thus, we propose a new metric that encompasses the number of direct neighbors and the network performance. In this way, the network response, due to the increasing number of nodes, is considered when deciding the density level. Moreover, we defined two terms, self-organization and self-configuration, which are usually used interchangeably in the literature through highlighting the difference ! between them. We believe that having a clear definition for terminology can eliminate a lot of ambiguity and help to present the research concepts more clearly. Some applications, such as In-Flight Entertainment (IFE) systems inside the aircraft cabin, can be considered as wirelessly high dense even if relatively few nodes are present. To solve this problem, we propose a heterogeneous architecture of different technologies to overcome the inherited constrains inside the cabin. Each technology aims at solving a part of the problem. We held various experimentation and simulations to show the feasibility of the proposed architecture
Mobile Ad hoc Networking: Imperatives and Challenges
Mobile ad hoc networks (MANETs) represent complex distributed systems that comprise wireless mobile nodes that can freely and dynamically self-organize into arbitrary and temporary, "ad-hoc" network topologies, allowing people and devices to seamlessly internetwork in areas with no pre-existing communication infrastructure, e.g., disaster recovery environments. Ad hoc networking concept is not a new one, having been around in various forms for over 20 years. Traditionally, tactical networks have been the only communication networking application that followed the ad hoc paradigm. Recently, the introduction of new technologies such as the Bluetooth, IEEE 802.11 and Hyperlan are helping enable eventual commercial MANET deployments outside the military domain. These recent evolutions have been generating a renewed and growing interest in the research and development of MANET. This paper attempts to provide a comprehensive overview of this dynamic field. It first explains the important role that mobile ad hoc networks play in the evolution of future wireless technologies. Then, it reviews the latest research activities in these areas, including a summary of MANET\u27s characteristics, capabilities, applications, and design constraints. The paper concludes by presenting a set of challenges and problems requiring further research in the future
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A Cross Layer Solution to Address TCP Intra-flow Performance Degradation in Multihop Ad hoc Networks
Incorporating the concept of TCP end-to-end congestion control for wireless networks is one of the primary concerns in designing ad hoc networks since TCP was primarily designed and optimized based on the assumptions for wired networks. In this study, our interest lies on tackling the TCP instability and in particular intra-flow instability problem since due to the nature of applications in multihop ad hoc networks, connection instability or starvation even for a short period of time can have a negative impact on the Quality of Service and may not be acceptable for the end user. Through a detailed analysis, it will be shown that the main causes of TCP intra-flow instability lies in overloading the network by sending more packets than the capacity of the channel. Based on this, the paper proposes a novel cross layer solution called âTCP Contention Controlâ that dynamically adjusts the amount of outstanding data in the network based on the level of contention experienced by packets as well as the throughput achieved by connections. The simulation results show TCP Contention Control can drastically improve TCP stability over 802.11 multihop ad hoc networks
Improving the Performance of Wireless LANs
This book quantifies the key factors of WLAN performance and describes methods for improvement. It provides theoretical background and empirical results for the optimum planning and deployment of indoor WLAN systems, explaining the fundamentals while supplying guidelines for design, modeling, and performance evaluation. It discusses environmental effects on WLAN systems, protocol redesign for routing and MAC, and traffic distribution; examines emerging and future network technologies; and includes radio propagation and site measurements, simulations for various network design scenarios, numerous illustrations, practical examples, and learning aids
Performance improvement of ad hoc networks using directional antennas and power control
Au cours de la derniĂšre dĂ©cennie, un intĂ©rĂȘt remarquable a Ă©tĂ© Ă©prouvĂ© en matiĂšre des rĂ©seaux ad hoc sans fil capables de s'organiser sans soutien des infrastructures. L'utilisation potentielle d'un tel rĂ©seau existe dans de nombreux scĂ©narios, qui vont du gĂ©nie civil et secours en cas de catastrophes aux rĂ©seaux de capteurs et applications militaires. La Fonction de coordination distribuĂ©e (DCF) du standard IEEE 802.11 est le protocole dominant des rĂ©seaux ad hoc sans fil. Cependant, la mĂ©thode DCF n'aide pas Ă profiter efficacement du canal partagĂ© et Ă©prouve de divers problĂšmes tels que le problĂšme de terminal exposĂ© et de terminal cachĂ©. Par consĂ©quent, au cours des derniĂšres annĂ©es, de diffĂ©rentes mĂ©thodes ont Ă©tĂ© dĂ©veloppĂ©es en vue de rĂ©gler ces problĂšmes, ce qui a entraĂźnĂ© la croissance de dĂ©bits d'ensemble des rĂ©seaux. Ces mĂ©thodes englobent essentiellement la mise au point de seuil de dĂ©tecteur de porteuse, le remplacement des antennes omnidirectionnelles par des antennes directionnelles et le contrĂŽle de puissance pour Ă©mettre des paquets adĂ©quatement. ComparĂ©es avec les antennes omnidirectionnelles, les antennes directionnelles ont de nombreux avantages et peuvent amĂ©liorer la performance des rĂ©seaux ad hoc. Ces antennes ne fixent leurs Ă©nergies qu'envers la direction cible et ont une portĂ©e d'Ă©mission et de rĂ©ception plus large avec la mĂȘme somme de puissance. Cette particularitĂ© peut ĂȘtre exploitĂ©e pour ajuster la puissance d'un transmetteur en cas d'utilisation d'une antenne directionnelle. Certains protocoles de contrĂŽle de puissance directionnel MAC ont Ă©tĂ© proposĂ©s dans les documentations. La majoritĂ© de ces suggestions prennent seulement la transmission directionnelle en considĂ©ration et, dans leurs rĂ©sultats de simulation, ces Ă©tudes ont l'habitude de supposer que la portĂ©e de transmission des antennes omnidirectionnelles et directionnelles est la mĂȘme. Apparemment, cette supposition n'est pas toujours vraie dans les situations rĂ©elles. De surcroĂźt, les recherches prenant l'hĂ©tĂ©rogĂ©nĂ©itĂ© en compte dans les rĂ©seaux ad hoc ne sont pas suffisantes. Le prĂ©sent mĂ©moire est dĂ©diĂ© Ă proposer un protocole de contrĂŽle de puissance MAC pour les rĂ©seaux ad hoc avec des antennes directionnelles en prenant tous ces problĂšmes en considĂ©ration. ______________________________________________________________________________ MOTS-CLĂS DE LâAUTEUR : RĂ©seaux ad hoc, Antennes directives, ContrĂŽle de puissance
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