2,288 research outputs found

    Energy-efficient wireless communication

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    In this chapter we present an energy-efficient highly adaptive network interface architecture and a novel data link layer protocol for wireless networks that provides Quality of Service (QoS) support for diverse traffic types. Due to the dynamic nature of wireless networks, adaptations in bandwidth scheduling and error control are necessary to achieve energy efficiency and an acceptable quality of service. In our approach we apply adaptability through all layers of the protocol stack, and provide feedback to the applications. In this way the applications can adapt the data streams, and the network protocols can adapt the communication parameters

    A flexible medium access control framework for multimedia application support in wireless ATM

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    Includes bibliographical references.The field of wireless communications has seen phenomenal development over the last decade. With the current abundance of applications that use broadband multimedia over wired networks it is logical that users will want to have access to these same multimedia streams [rom a mobile terminal. Wireless solutions for connectivity to networks such as Ethernet networks already exist, however, a method of supporting access to an ATM network from a mobile terminal has not yet been standardised. Transporting ATM data over the wireless medium poses a number of problems. The Medium Access Control (MAC) layer of any proposed wireless ATM network would be responsible for resolving many of these problems. Unfortunately, research into MAC layers is hampered by the fact that most existing MAC layers cannot be modified in order to experiment with the effectiveness of the many MAC protocol techniques that exist

    Bandwidth reservation in mobile ad hoc networks for providing QoS : adaptation for voice support

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    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 nƓuds 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 nƓuds 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 nƓud pour Ă©tablir une rĂ©servation est bien reçu par tous ses nƓuds voisins. Dans la deuxiĂšme partie de cette thĂšse, nous appliquons le protocole de rĂ©servation proposĂ© au trafic de type voix. Ainsi, nous Ă©tendons ce protocole afin de prendre en compte les caractĂ©ristiques du trafic voix, tout en permettant le transport de trafic de donnĂ©es. Nous nous focalisons sur l'utilisation efficace de la bande passante et les mĂ©canismes pour rĂ©duire 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 nƓuds. Nous Ă©valuons les performances du protocole proposĂ© dans plusieurs scĂ©narios dans lesquels nous montrons sa supĂ©rioritĂ© 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

    A quantitative comparison of multiple access control protocols for wireless ATM

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    The multiple access control (MAC) problem in a wireless network has intrigued researchers for years. For a broad-band wireless network such as wireless ATM, an effective MAC protocol is very much desired because efficient allocation of channel bandwidth is imperative in accommodating a large user population with satisfactory quality of service. Indeed, MAC protocols for a wireless ATM network in which user traffic requirements are highly heterogeneous (classified into CBR, VBR, and ABR), are even more intricate to design. Considerable research efforts expended in tackling the problem have resulted in a myriad of MAC protocols. While each protocol is individually shown to be effective by the respective designers, it is unclear how these different protocols compare against each other on a unified basis. In this paper, we quantitatively compare seven recently proposed TDMA-based MAC protocols for integrated wireless data and voice services. We first propose a taxonomy of TDMA-based protocols, from which we carefully select seven protocols, namely SCAMA, DTDMA/VR, DTDMA/PR, DQRUMA, DPRMA, DSA++, and PRMA/DA, such that they are devised based on rather orthogonal design philosophies. The objective of our comparison is to highlight the merits and demerits of different protocol designs.published_or_final_versio

    A novel channel-adaptive uplink access control protocol for nomadic computing

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    We consider the uplink access control problem in a mobile nomadic computing system, which is based on a cellular phone network in that a user can use the mobile device to transmit voice or file data. This resource management problem is important because an efficient solution to uplink access control is critical for supporting a large user population with a reasonable level of quality of service (QoS). While there are a number of recently proposed protocols for uplink access control, these protocols possess a common drawback in that they do not adapt well to the burst error properties, which are inevitable in using wireless communication channels. In this paper, we propose a novel TDMA-based uplink access protocol, which employs a channel state dependent allocation strategy. Our protocol is motivated by two observations: 1) when channel state is bad, the throughput is low due to the large amount of FEC (forward error correction) or excessive ARQ (automatic repeated request) that is needed and 2) because of item 1, much of the mobile device's energy is wasted. The proposed protocol works closely with the underlying physical layer in that, through observing the channel state information (CSI) of each mobile device, the MAC protocol first segregates a set of users with good CSI from requests gathered in the request contention phase of an uplink frame. The protocol then judiciously allocates channel bandwidth to contending users based on their channel conditions. Simulation results indicate that the proposed protocol considerably outperforms five state-of-the-art protocols in terms of packet loss, delay, and throughput.published_or_final_versio

    Survey of Transportation of Adaptive Multimedia Streaming service in Internet

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    [DE] World Wide Web is the greatest boon towards the technological advancement of modern era. Using the benefits of Internet globally, anywhere and anytime, users can avail the benefits of accessing live and on demand video services. The streaming media systems such as YouTube, Netflix, and Apple Music are reining the multimedia world with frequent popularity among users. A key concern of quality perceived for video streaming applications over Internet is the Quality of Experience (QoE) that users go through. Due to changing network conditions, bit rate and initial delay and the multimedia file freezes or provide poor video quality to the end users, researchers across industry and academia are explored HTTP Adaptive Streaming (HAS), which split the video content into multiple segments and offer the clients at varying qualities. The video player at the client side plays a vital role in buffer management and choosing the appropriate bit rate for each such segment of video to be transmitted. A higher bit rate transmitted video pauses in between whereas, a lower bit rate video lacks in quality, requiring a tradeoff between them. The need of the hour was to adaptively varying the bit rate and video quality to match the transmission media conditions. Further, The main aim of this paper is to give an overview on the state of the art HAS techniques across multimedia and networking domains. A detailed survey was conducted to analyze challenges and solutions in adaptive streaming algorithms, QoE, network protocols, buffering and etc. It also focuses on various challenges on QoE influence factors in a fluctuating network condition, which are often ignored in present HAS methodologies. Furthermore, this survey will enable network and multimedia researchers a fair amount of understanding about the latest happenings of adaptive streaming and the necessary improvements that can be incorporated in future developments.Abdullah, MTA.; Lloret, J.; Canovas Solbes, A.; GarcĂ­a-GarcĂ­a, L. (2017). Survey of Transportation of Adaptive Multimedia Streaming service in Internet. Network Protocols and Algorithms. 9(1-2):85-125. doi:10.5296/npa.v9i1-2.12412S8512591-

    Final report on the evaluation of RRM/CRRM algorithms

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    Deliverable public del projecte EVERESTThis deliverable provides a definition and a complete evaluation of the RRM/CRRM algorithms selected in D11 and D15, and evolved and refined on an iterative process. The evaluation will be carried out by means of simulations using the simulators provided at D07, and D14.Preprin
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