Controlo de acesso ao meio em redes ad hoc móveis IEEE 802.11

Dissertação apresentada para obtenção do Grau de Doutor em Engenharia Electrotécnica, especialidade de Telecomunicações, pela Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologia

Models for pheromone evaluation in Ant Systems for Mobile Ad-hoc networks

On a mobile ad-hoc network environment, where the resources are scarce, the knowledge about the network's link state is essential to optimize the routing procedures. This paper presents a study about different pheromone evaluation models and how they react to possible changes in traffic rate. Observing how the pheromone value on a link changes, it could be possible to identify certain patterns which can indicate the path status. For this study, the behavior of the Ant System evaluation model was compared with a Temporal Active Pheromone model (a biological approach) and a Progressive Pheromone Reduction model with and without a maximum pheromone limit.

Controlo de acesso ao meio fiável para redes Ad Hoc

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica, Sistemas e Computadores

Desenvolvimento de uma infraestrutura computacional que visa o aumento da eficiência energética em edifícios através da utilização de redes Ad Hoc

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica e de Computadores

MAC regenerative analysis of wireless Ad-Hoc networks

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Engenharia Electrotécnica e de Computadores

Providing QoS for publishing/subscribe communication in dynamic ad-hoc networks

QoS, MANET, Ad-hoc networks, Simulation, wireless communication

Does Ad Hoc Coronary Intervention Reduce Radiation Exposure? – Analysis of 568 Patients

Background:Advantages and disadvantages of ad hoc percutaneous coronary intervention have been described. However little is known about the radiation exposure of that procedure as compared with the staged intervention.Objective:To compare the radiation dose of the ad hoc percutaneous coronary intervention with that of the staged procedureMethods:The dose-area product and total Kerma were measured, and the doses of the diagnostic and therapeutic procedures were added. In addition, total fluoroscopic time and number of acquisitions were evaluated.Results:A total of 568 consecutive patients were treated with ad hoc percutaneous coronary intervention (n = 320) or staged percutaneous coronary intervention (n = 248). On admission, the ad hoc group had less hypertension (74.1% vs 81.9%; p = 0.035), dyslipidemia (57.8% vs. 67.7%; p = 0.02) and three-vessel disease (38.8% vs. 50.4%; p = 0.015). The ad hoc group was exposed to significantly lower radiation doses, even after baseline characteristic adjustment between both groups. The ad hoc group was exposed to a total dose-area product of 119.7 ± 70.7 Gycm2, while the staged group, to 139.2 ± 75.3 Gycm2 (p < 0.001).Conclusion:Ad hoc percutaneous coronary intervention reduced radiation exposure as compared with diagnostic and therapeutic procedures performed at two separate times.

The Office International des Epizooties ad hoc Group on Non Tsetse Animal Trypanosomoses: Its Origin, Scope and Perspectives

A summary of the goals and activities of the ad hoc group on Non Tsetse Transmitted Animal Trypanosomosis belonging to the Office International des Epizooties is presented.

Emerging narratives of conference interpreters’ training: a case study of ad hoc training in Babels and the Social Forum

Desde una perspectiva narrativa, este artículo explora cómo la práctica y la formación en interpretación de conferenciasse han percibido en la disciplina, en la profesión y en diferentescolectivos de traductores e interpretes comprometid@s como ECOSy Babels. Sostiene que estas distintas maneras de percibir la interpretación no son meramente opuestas sino que su potencial confluencia es clave para hacer posible una interpretación de conferencias más comprometida políticamente y más socio-crítica en un mundo de desigualdades cada vez más acentuadas y de mercantilización creciente de todos los aspectos de la vida. El artículo lleva a cabo un estudio de caso sobre la formación ad hoc de intérpretes en el Foro Social, en particular el Foro Social Europeo de Londres, y analiza cómo el trabajo colectivo entre instituciones educativas y sociedad civil tanto local como global ha dado luz a prácticas transformadoras hacia una metodología de formación mássocio-critica y con mayor consciencia ética.

Intraoral open reduction and internal fixation of displaced mandibular angle fractures using a specific ad hoc reduction-compression forceps: a preliminary study

OBJECTIVES: To preliminarily evaluate prospectively the accuracy and reliability of a specific ad hoc reduction-compression forceps in intraoral open reduction of transverse and displaced mandibular angle fractures. STUDY DESIGN: We analyzed the clinical and radiologic data of 7 patients with 7 single transverse and displaced angle fractures. An intraoral approach was performed in all of the patients without using perioperative intermaxillary fixation. A single Arbeitsgemeinschaft Osteosynthese (AO) unilock reconstruction plate was fixed to each stable fragment with 3 locking screws (2.0 mm in 5 patients and 2.4 mm in 2 patients) at the basilar border of the mandible, according to AO/American Society of Internal Fixation (ASIF) principles. Follow-up was at 1, 3, 6, and 12 months, and we noted the status of healing and complications, if any. RESULTS: All of the patients had satisfactory fracture reduction as well as a successful treatment outcome without complications. CONCLUSION: This preliminary study demonstrated that the intraoral reduction of transverse and displaced angle fractures using a specific ad hoc reduction-forceps results in a high rate of success.

Modular support for developing mobile ad hoc applications

Abstract This PhD thesis addresses the issue of alleviating the burden of developing ad hoc applications. Such applications have the particularity of running on mobile devices, communicating in a peer-to-peer manner and implement some proximity-based semantics. A typical example of such application can be a radar application where users see their avatar as well as the avatars of their friends on a map on their mobile phone. Such application become increasingly popular with the advent of the latest generation of mobile smart phones with their impressive computational power, their peer-to-peer communication capabilities and their location detection technology. Unfortunately, the existing programming support for such applications is limited, hence the need to address this issue in order to alleviate their development burden. This thesis specifically tackles this problem by providing several tools for application development support. First, it provides the location-based publish/subscribe service (LPSS), a communication abstraction, which elegantly captures recurrent communication issues and thus allows to dramatically reduce the code complexity. LPSS is implemented in a modular manner in order to be able to target two different network architectures. One pragmatic implementation is aimed at mainstream infrastructure-based mobile networks, where mobile devices can communicate through fixed antennas. The other fully decentralized implementation targets emerging mobile ad hoc networks (MANETs), where no fixed infrastructure is available and communication can only occur in a peer-to-peer fashion. For each of these architectures, various implementation strategies tailored for different application scenarios that can be parametrized at deployment time. Second, this thesis provides two location-based message diffusion protocols, namely 6Shot broadcast and 6Shot multicast, specifically aimed at MANETs and fine tuned to be used as building blocks for LPSS. Finally this thesis proposes Phomo, a phone motion testing tool that allows to test proximity semantics of ad hoc applications without having to move around with mobile devices. These different developing support tools have been packaged in a coherent middleware framework called Pervaho.

System-level Support for Mobile Ad hoc Communications: an Algorithmic & Practical Approach

A mobile ad hoc network (MANET) is a decentralized and infrastructure-less network. This thesis aims to provide support at the system-level for developers of applications or protocols in such networks. To do this, we propose contributions in both the algorithmic realm and in the practical realm. In the algorithmic realm, we contribute to the field by proposing different context-aware broadcast and multicast algorithms in MANETs, namely six-shot broadcast, six-shot multicast, PLAN-B and ageneric algorithmic approach to optimize the power consumption of existing algorithms. For each algorithm we propose, we compare it to existing algorithms that are either probabilistic or context-aware, and then we evaluate their performance based on simulations. We demonstrate that in some cases, context-aware information, such as location or signal-strength, can improve the effciency. In the practical realm, we propose a testbed framework, namely ManetLab, to implement and to deploy MANET-specific protocols, and to evaluate their performance. This testbed framework aims to increase the accuracy of performance evaluation compared to simulations, while keeping the ease of use offered by the simulators to reproduce a performance evaluation. By evaluating the performance of different probabilistic algorithms with ManetLab, we observe that both simulations and testbeds should be used in a complementary way. In addition to the above original contributions, we also provide two surveys about system-level support for ad hoc communications in order to establish a state of the art. The first is about existing broadcast algorithms and the second is about existing middleware solutions and the way they deal with privacy and especially with location privacy. - Un réseau mobile ad hoc (MANET) est un réseau avec une architecture décentralisée et sans infrastructure. Cette thèse vise à fournir un support adéquat, au niveau système, aux développeurs d'applications ou de protocoles dans de tels réseaux. Dans ce but, nous proposons des contributions à la fois dans le domaine de l'algorithmique et dans celui de la pratique. Nous contribuons au domaine algorithmique en proposant différents algorithmes de diffusion dans les MANETs, algorithmes qui sont sensibles au contexte, à savoir six-shot broadcast,six-shot multicast, PLAN-B ainsi qu'une approche générique permettant d'optimiser la consommation d'énergie de ces algorithmes. Pour chaque algorithme que nous proposons, nous le comparons à des algorithmes existants qui sont soit probabilistes, soit sensibles au contexte, puis nous évaluons leurs performances sur la base de simulations. Nous montrons que, dans certains cas, des informations liées au contexte, telles que la localisation ou l'intensité du signal, peuvent améliorer l'efficience de ces algorithmes. Sur le plan pratique, nous proposons une plateforme logicielle pour la création de bancs d'essai, intitulé ManetLab, permettant d'implémenter, et de déployer des protocoles spécifiques aux MANETs, de sorte à évaluer leur performance. Cet outil logiciel vise à accroître la précision desévaluations de performance comparativement à celles fournies par des simulations, tout en conservant la facilité d'utilisation offerte par les simulateurs pour reproduire uneévaluation de performance. En évaluant les performances de différents algorithmes probabilistes avec ManetLab, nous observons que simulateurs et bancs d'essai doivent être utilisés de manière complémentaire. En plus de ces contributions principales, nous fournissons également deux états de l'art au sujet du support nécessaire pour les communications ad hoc. Le premier porte sur les algorithmes de diffusion existants et le second sur les solutions de type middleware existantes et la façon dont elles traitent de la confidentialité, en particulier celle de la localisation.

Recipients' Anonymity in Multihop Ad-hoc Networks

Multihop ad-hoc networks have a dynamic topology. Retrieving a route towards a remote peer requires the execution of a recipient lookup, which can publicly reveal sensitive information about him. Within this context, we propose an efficient, practical and scalable solution to guaranteethe anonymity of recipients' nodes in ad-hoc networks.