<p>The number of automobiles has been increased on the road in the past few years. Due to high density of vehicles, the potential threats and road accident is increasing. Wireless technology is aiming to equip technology in vehicles to reduce these factors by sending messages to each other.</p><p>The vehicular safety application should be thoroughly tested before it is deployed in a real world to use. Simulator tool has been preferred over out door experiment because it simple, easy and cheap. VANET requires that a traffic and network simulator should be used together to perform this test. Many tools exist for this purpose but most of them have the problem with the proper interaction. In this thesis, we aim at simulating vehicular networks with external stimulus to analyze its effect on wireless communication but to do this job a good simulator is also needed. So we will first debate on the shortcoming of current simulators and come up with our own recommendations to perform our simulation.</p>

The number of automobiles has been increased on the road in the past few years. Due to high density of vehicles, the potential threats and road accident is increasing. Wireless technology is aiming to equip technology in vehicles to reduce these factors by sending messages to each other. The vehicular safety application should be thoroughly tested before it is deployed in a real world to use. Simulator tool has been preferred over out door experiment because it simple, easy and cheap. VANET requires that a traffic and network simulator should be used together to perform this test. Many tools exist for this purpose but most of them have the problem with the proper interaction. In this thesis, we aim at simulating vehicular networks with external stimulus to analyze its effect on wireless communication but to do this job a good simulator is also needed. So we will first debate on the shortcoming of current simulators and come up with our own recommendations to perform our simulation.

Master of Science / Department of Computing and Information Sciences / Gurdip Singh / Ad hoc based routing protocol is a reactive protocol to route messages between mobile nodes. It allows nodes to pass messages through their neighbors to nodes which they cannot directly communicate. It uses Route Request (RREQ) and Route Reply (RREP) messages for communication. Wireless sensor networks consist of tiny sensor motes with capabilities of sensing, computation and wireless communication. This project aims to implement data collector application to collect the temperature data from the set of wireless sensor devices located within a building, which will help in gathering the information by finding the route with minimum number of hops to reach destination and generates low message traffic by not encouraging the duplicate message within the network. Using this application, wireless devices can communicate effectively to provide the network information to the user. This system consists of a mobile wireless sensor device called base station which is connected to a PC to communicate and is the root of the network. It also consists of set of client sensor devices which are present in different parts of the building. This project has been evaluated by determining how well the ad hoc protocol performs by measuring the number of messages and time consumed in learning about the complete topology. This application will eventually find the path with minimum number of hops. Simple Network Management Protocol (SNMP) is also used to monitor the sensor nodes remotely. This project was developed using nesC and C programming languages with TinyOS and UNIX based operating systems. It has been tested with a sufficient number of motes and evaluated based on the number of messages generated and number of hops traveled for each route request.

In this thesis, we are concerned with content dissemination in mobile ad hoc networks. The scope of content dissemination is limited by network capacity, and sometimes the price to be paid for securing faster delivery. In the first part of the thesis, we address the issue of finding the maximum throughput that a mobile ad-hoc network can support. We have assumed that there is no price involved, and all nodes work as a team. The problem of determining the capacity region has long been known to be NP-hard even for stationary nodes. Mobility introduces an additional dimension of complexity because nodes now also have to decide when they should initiate route discovery. Since route discovery involves communication and computation overhead, it should not be invoked very often. On the other hand, mobility implies that routes are bound to become stale, resulting in sub-optimal performance if routes are not updated. We attempt to gain some understanding of these effects by considering a simple one-dimensional network model. The simplicity of our model allows us to use stochastic dynamic programming (SDP) to find the maximum possible network throughput with ideal routing and medium access control (MAC) scheduling. Using the optimal value as a benchmark, we also propose and evaluate the performance of a simple threshold-based heuristic. Unlike the optimal policy which requires considerable state information, the proposed heuristic is simple to implement and is not overly sensitive to the threshold value. We find empirical conditions for our heuristic to be near-optimal. Also, network scenarios when our heuristic does not perform very well are analyzed. We provide extensive numerical analysis and simulation results for different parameter settings of our model. Interestingly, we observe that in low density network the average throughput can first decrease with mobility, and then increase. This motivates us to study a mobile ad-hoc network when it is sparse and in a generalized environment, such as when movement of nodes is in a two-dimension plane. Due to sparseness, there are frequent disruptions in the connections and there may not be any end-to-end connection for delivery. The mobility of nodes may be used for carrying the forwarded message to the destination. This network is also known as a delay tolerant network. In the rest part of the thesis, we consider the relay nodes to be members of a group that charges a price for assisting in message transportation. First, we solve the problem of how to select first relay node when only one relay node can be chosen from a given number of groups. Next, we solve two problems, namely price-constrained delay minimization, and delay-constrained price optimization.

ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, California / The integrated Network Enhanced Telemetry effort (iNET) was launched to create a telemetry network that will enhance the traditional point-to-point telemetry link from test articles (TAs) to ground stations (GS). Two of the critical needs identified by the Central Test and Evaluation Investment Program (CTEIP) are, "the need to be able to provide reliable coverage in potentially high capacity environments, even in Over-The-Horizon (OTH) settings", and "the need to make more efficient use of spectrum resources through dynamic sharing of said resources, based on instantaneous demand thereof". Research conducted at Morgan State University (MSU) has focused on providing solutions for both critical problems. The Mixed Network architecture developed by MSU has shown that a hybrid network can be used to provide coverage for TAs that are beyond the coverage area of the GS. The mixed network uses clustering techniques to partition the aggregate network into clusters or sub-networks based on properties of each TA, which currently include signal strengths, and location. The paper starts with a detailed analysis of two parameters that affect the performance of each sub-network: contention between the TAs in the mobile ad-hoc network, and queuing at the Gateway TAs that serve as the link between the mobile ad-hoc and the Cellular networks. Contention and queuing will be used to evaluate two performance (distance) measures for each sub-network: throughput and delay. We define a new distance measure known as "power", which is equal to the ratio of throughput over delay, and is used as a measure of performance of the mixed network for Quality of Service (QOS). This paper describes the analytical foundation used to prove that the "power" performance measure is an excellent tool for optimizing the clustering of a mixed network to provide QOS.

ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / The focus of the integrated Network Enhanced Telemetry (iNET) project is to enhance the current telemetry technology (IRIG106) and still maintain the reliability of the current technology. The Mixed Networking environment is composed of a wired network based on standard 802.11 and a modified wireless based on 802.11. Determining the viability of the networking scheme within the iNET project is critical. The QoS features such as delay and jitter are measures of performance specified by user conditions. These QoS features are measured against current legacy links. This paper will show a comparison of the three QoS levels (best effort, assured, and premium services) that the network provides and investigate QoS performance of the Mixed Network in the iNET environment. This will provide a framework for assessing the strength and weakness of the Mixed Network as well as scoping further research.

Les travaux de cette thèse s'inscrivent tous dans la thématique " traitement du signal pour les réseaux de communications distribués ". Le réseau est dit distribué au sens de la décision. Dans ce cadre, le problème générique et important que nous avons approfondi est le suivant. Comment un terminal, qui a accès à plusieurs canaux de communications, doit-il répartir (de manière autonome) sa puissance d'émission entre ses canaux et l'adapter dans le temps en fonction de la variabilité des conditions de communications ? C'est le problème de l'allocation de ressources adaptative et distribuée. Nous avons développé 4 axes de travail qui ont tous conduits à des réponses originales à ce problème ; la forte corrélation entre ces axes est expliquée dans le manuscrit de thèse. Le premier axe a été l'alignement opportuniste d'interférence. Un des scénarios de référence est le cas où deux couples émetteur-récepteur communiquent en interférant (sur la même bande, en même temps, au même endroit, ...), où les 4 terminaux sont équipés de plusieurs antennes et où un émetteur est contraint de ne pas (ou peu) interférer sur l'autre (canal à interférence dit MIMO). Nous avons conçu une technique d'émission de signal multi-antennaire qui exploite l'observation-clé suivante et jamais exploitée auparavant: même lorsqu'un émetteur est égoïste au sens de ses performances individuelles, celui-ci laisse des ressources spatiales (dans le bon espace de signal et que nous avons identifié) vacantes pour l'autre émetteur. L'apport en performances en termes de débit par rapport aux meilleurs algorithmes existants a été quantifié grâce à la théorie des matrices aléatoires et des simulations Monte Carlo. Ces résultats sont particulièrement importants pour le scénario de la radio cognitive en milieu dense. Dans un second temps, nous avons supposé que tous les émetteurs d'un réseau sont libres d'utiliser leurs ressources de manière égoïste. Les ressources sont données ici par les canaux fréquentiels et la métrique individuelle de performance est le débit. Ce problème peut être modélisé par un jeu dont les joueurs sont les émetteurs. Une de nos contributions a été de montrer que ce jeu est un jeu de potentiel, ce qui est fondamental pour la convergence des algorithmes distribués et l'existence d'équilibre de Nash. De plus, nous avons montré l'existence d'un paradoxe de Braess : si l'espace d'optimisation d'un joueur grandit, les performances individuelles et globales peuvent s'en trouver réduites. Cette conclusion a une conséquence pratique immédiate : il peut y a voir intérêt de restreindre le nombre de canaux fréquentiels utilisables dans un réseau à interférence distribué. Dans le jeu précédent, nous avions constaté que les algorithmes distribués d'allocation de ressources (les algorithmes d'apprentissage par renforcement typiquement) demandent un grand nombre d'itérations pour converger vers un état stable tel qu'un équilibre de Nash. Nous avons ainsi proposé un nouveau concept de solution d'un jeu, à savoir l'équilibre de satisfaction ; les joueurs ne modifient pas leur action, même si celle-ci ne maximise pas leur gain, pourvu qu'un niveau minimal de performance soit atteint. Nous avons alors développé une méthodologie d'étude de cette solution (existence, unicité, convergence, ...). Une de nos contributions a aussi été de donner des algorithmes d'apprentissage qui convergent vers cette solution en un temps fini (et même court génériquement). De nombreux résultats numériques réalisés dans des scénarios imposés par Orange ont confirmé la pertinence de cette nouvelle approche. Le quatrième axe de travail a été la conception de nouveaux algorithmes d'apprentissage qui convergent vers des solutions de type équilibre logit, epsilon-équilibre ou équilibre de Nash. Notre apport a été de montrer comment modifier les algorithmes existants pour que ceux-ci évitent les phénomènes de cycles et convergent vers un équilibre présélectionné au départ de la dynamique. Une idée importante a été d'introduire une dynamique d'apprentissage de la fonction métrique de performances en couplage avec la dynamique principale qui régit l'évolution de la distribution de probabilité sur les actions possibles d'un joueur. Le cadre de ces travaux est parfaitement réaliste d'un point de vue informatif au niveau des terminaux en pratique. Il est montré une voie possible pour améliorer l'efficacité des points de convergence, ce qui constitue un problème encore ouvert dans ce domaine.

Wireless sensor networks offer the advantages of low cost, flexible measurement of phenomenon in a wide variety of applications, and easy deployment. Since sensor nodes are typically battery powered, energy efficiency is an important objective in designing sensor network algorithms. These algorithms are often application-specific, owing to the need to carefully optimize energy usage, and since deployments usually support a single or very few applications.<p> This thesis concerns applications in which the sensors monitor a continuous scalar field, such as temperature, and addresses the problem of determining the location of a contour line in this scalar field, in response to a query, and communicating this information to a designated sink node. An energy-efficient solution to this problem is proposed and evaluated. This solution includes new contour detection and query propagation algorithms, in-network-processing algorithms, and routing algorithms. Only a small fraction of network nodes may be adjacent to the desired contour line, and the contour detection and query propagation algorithms attempt to minimize processing and communication by the other network nodes. The in-network processing algorithms reduce communication volume through suppression, compression and aggregation techniques. Finally, the routing algorithms attempt to route the contour information to the sink as efficiently as possible, while meshing with the other algorithms. Simulation results show that the proposed algorithms yield significant improvements in data and message volumes compared to baseline models, while maintaining the integrity of the contour representation.

Wireless sensor networks offer the advantages of low cost, flexible measurement of phenomenon in a wide variety of applications, and easy deployment. Since sensor nodes are typically battery powered, energy efficiency is an important objective in designing sensor network algorithms. These algorithms are often application-specific, owing to the need to carefully optimize energy usage, and since deployments usually support a single or very few applications.<p> This thesis concerns applications in which the sensors monitor a continuous scalar field, such as temperature, and addresses the problem of determining the location of a contour line in this scalar field, in response to a query, and communicating this information to a designated sink node. An energy-efficient solution to this problem is proposed and evaluated. This solution includes new contour detection and query propagation algorithms, in-network-processing algorithms, and routing algorithms. Only a small fraction of network nodes may be adjacent to the desired contour line, and the contour detection and query propagation algorithms attempt to minimize processing and communication by the other network nodes. The in-network processing algorithms reduce communication volume through suppression, compression and aggregation techniques. Finally, the routing algorithms attempt to route the contour information to the sink as efficiently as possible, while meshing with the other algorithms. Simulation results show that the proposed algorithms yield significant improvements in data and message volumes compared to baseline models, while maintaining the integrity of the contour representation.

Dispersed spectrum cognitive radio systems represent a promising approach to exploit the utilization of spectral resources to full extent. Therefore, the performance analysis of such systems is conducted in this research. The Average symbol error probability of dispersed spectrum cognitive radio systems is derived for two cases: where each channel realization experiences independent and dependent Nakagami-m fading, respectively. In addition, the derivation is extended to include the effects of modulation type and order by considering M-PSK and M-QAM modulation schemes. We then study the impacts of topology on the effective transport capacity performance of ad hoc dispersed spectrum cognitive radio systems where the nodes assume 3- dimensional (3D) configurations. We derive the effective transport capacity considering a cubic grid distribution. In addition, numerical results are presented to demonstrate the effects of topology on the effective transport capacity of ad hoc dispersed cognitive radio systems.