667 research outputs found

    Attention to Wi-Fi Diversity: Resource Management in WLANs with Heterogeneous APs

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    Many home networks integrate a small number (typically 2-4) of Wi-Fi Access Points (APs), with heterogeneous characteristics: different 802.11 variants, capabilities and security schemes. This paper proposes the consideration of these specific characteristics in order to improve the management of network resources. Three use cases are presented in order to showcase the potential benefits. By the use of a user-space AP, which works in coordination with a controller, the network is able to assign each connected station to the AP that best fits with its characteristics. The system also manages security, avoiding the need of adding specific elements for authentication, encryption or decryption. Extensions are proposed to an existing protocol that defines the communication between the AP and the controller, in order to communicate and store the specific characteristics of each AP and end device. This includes new association and handoff schemes that do not introduce any additional delay. The system has been implemented in a real environment, and a battery of tests has been run using three hardware platforms of different characteristics. The results show that handoffs between bands are possible, and estimate the processing delays, the Round-Trip Time and the handoff delay, which is small enough in order not to produce any significant disruption to the user (10-50 ms). Finally, the scenarios of interest have been replicated in a simulation environment, showing that significant benefits can be achieved if the specific characteristics of each AP and station are considered

    A Survey on Wireless Network Simulators

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    The Network simulator helps the developer to create and simulate new models on an arbitrary network by specifying both the behavior of the network nodes and the communication channels. It provides a virtual environment for an assortment of desirable features such as modeling a network based on a specific criteria and analyzing its performance under different scenarios. This saves cost and time required for testing the functionality and the execution of network. This paper has surveyed various Wireless Network Simulators and compared them

    A Survey on Wireless Network Simulators

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    The Network simulator helps the developer to create and simulate new models on an arbitrary network by specifying both the behavior of the network nodes and the communication channels. It provides a virtual environment for an assortment of desirable features such as modeling a network based on a specific criteria and analyzing its performance under different scenarios. This saves cost and time required for testing the functionality and the execution of network. This paper has surveyed various Wireless Network Simulators and compared them

    Miracle: the multi-interface cross-layer extension of ns2

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    We present Miracle, a novel framework which extends ns2 to facilitate the simulation and the design of beyond 4G networks. Miracle enhances ns2 by providing an efficient and embedded engine for handling cross-layer messages and, at the same time, enabling the coexistence of multiple modules within each layer of the protocol stack. We also present a novel framework developed as an extension of Miracle called Miracle PHY and MAC. This framework facilitates the development of more realistic Channel, PHY and MAC modules, considering features currently lacking in most state-of-the-art simulators, while at the same time giving a strong emphasis on code modularity, interoperability and reusability. Finally, we provide an overview of the wireless technologies implemented in Miracle, discussing in particular the models for the IEEE 802.11, UMTS and WiMAX standards and for Underwater Acoustic Networks. We observe that, thanks to Miracle and its extensions, it is possible to carefully simulate complex network architectures at all the OSI layers, from the physical reception model to standard applications and system management schemes. This allows to have a comprehensive view of all the interactions among network components, which play an important role in many research areas, such as cognitive networking and cross-layer design

    Augmented reality device for first response scenarios

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    A prototype of a wearable computer system is proposed and implemented using commercial off-shelf components. The system is designed to allow the user to access location-specific information about an environment, and to provide capability for user tracking. Areas of applicability include primarily first response scenarios, with possible applications in maintenance or construction of buildings and other structures. Necessary preparation of the target environment prior to system\u27s deployment is limited to noninvasive labeling using optical fiducial markers. The system relies on computational vision methods for registration of labels and user position. With the system the user has access to on-demand information relevant to a particular real-world location. Team collaboration is assisted by user tracking and real-time visualizations of team member positions within the environment. The user interface and display methods are inspired by Augmented Reality1 (AR) techniques, incorporating a video-see-through Head Mounted Display (HMD) and fingerbending sensor glove.*. 1Augmented reality (AR) is a field of computer research which deals with the combination of real world and computer generated data. At present, most AR research is concerned with the use of live video imagery which is digitally processed and augmented by the addition of computer generated graphics. Advanced research includes the use of motion tracking data, fiducial marker recognition using machine vision, and the construction of controlled environments containing any number of sensors and actuators. (Source: Wikipedia) *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Adobe Acrobat; Microsoft Office; Windows MediaPlayer or RealPlayer

    Medium and mobility behaviour insertion for 802.11 emulated networks

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    Wmediumd és una aplicació basada en el llenguatge de programació C i que va ser desemvolupada per una consultora d’Estats Units anomenada Cozybit. Wmediumd va ser creada per dur a terme emulació del medi sense fils a xarxes emulades Linux. Aquesta aplicació permet als programadors de controladors 802.11 crear un entorn de desenvolupament/prova amb un sol ordinador, estalviant temps i equips. La versió actual d’aquesta aplicació només emula el comportament del medi mitjançant la pèrdua de paquets basant-se en probabilitats, sense patrons de mobilitat entre ràdios emulades i sense tindre en compte les interferències del medi. És interessant per Cozybit i per altres desenvolupadors crear una extensió de Wmediumd introduint el comportament del medi i de mobilitat de les ràdios emulades. D’aquesta manera es millorarien els test-beds de 802.11 per als desenvolupadors de controladors. English: Wmediumd is an application based on the C programming language and was developed by a United States company called Cozybit. Wmediumd was created to perform emulation of the wireless environment on emulated networks created on Linux OS. This application allows programmers of 802.11 drivers to create an environment for development/testing with a single computer, saving time and hardware. Current version of this application only emulates the behaviour of the medium creating frame losses depending on probabilities, but not using mobility patterns between emulated radios and also without taking into account the interferences the environment has. It is interesting for Cozybit and other developers to create an extension of Wmediumd to introduce environmental behaviour and mobility on the emulated radios. Introducing this extension will improve the test-beds for the 802.11 driver developers
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