<p> Wireless metropolitan area networking based on IEEE 802.16 is expected to be widely used for creating wide-area wireless backhaul networks, where each subscriber station (SS) is responsible for forwarding traffic for a number of connections. Quality of Service (QoS) provisioning is an important aspect in such networks. The IEEE 802.16 standard specifies that the bandwidth requests sent by the SS are for individual connections and pass only the number of bytes requested from each connection. This is inefficient for backhaul networks where each SS may be responsible for forwarding packets for a relatively large number of connections and the bandwidth request messages consume much bandwidth unnecessarily. Furthermore, the standard does not include latency information, which makes it difficult for the base station (BS) to schedule real-time traffic. </p> <p> In this thesis we study real-time voice traffic support in IEEE 802.16-based backhaul networks. We propose a simple enhancement to the bandwidth request mechanism in 802.16 for supporting packet voice traffic. First, the SS combines the bandwidth requests of multiple voice connections, which are associated to it and have the same traffic parameters, and aggregates the bandwidth requests to the BS. This makes the bandwidth request process more efficient by saving transmission time of both the BS and the SSs. Second, in order to facilitate the BS to make resource allocation decisions, the aggregate bandwidth requests include information about the latency requirements of buffered real-time packets at the SSs. We propose three different bandwidth request and packet scheduling schemes, each of which requires a different amount of information in the bandwidth requests. Our results show that the proposed bandwidth request and scheduling schemes achieve significantly lower packet loss probability than standard 802.16 bandwidth requests and weighted round robin. The results further show that there is an optimum point about how much delay information the SS should report to the BS in order to best utilize the uplink resources while providing satisfactory real-time performance for the voice traffic. </p> / Thesis / Master of Applied Science (MASc)

An adaptive MAC protocol is developed and analyzed that offers a "best case" scenario by allowing the MAC to control medium parameters thereby fully exploiting the channel of an ad hoc wireless LAN. This new, opportunistic medium access control protocol is called CATER (Code Adapts To Enhance Reliability) and is based on the proposed MAC standard for wireless local area networks (WLAN)-IEEE 802.11 [IEE96]. As currently proposed, IEEE 802.11 uses a fixed pseudo-noise (PN) code for spreading the information signal, implying a fixed process gain at the receiver. When the channel degrades, IEEE 802.11 offers only retransmissions at the MAC layer to combat a corrupt medium. However, CATER allows communicating stations to reconfigure their transceivers to use a longer PN code after a prescribed number of failed retransmissions. This longer code increases the process gain of the receiver and reduces the error rate. After the two stations are reconfigured, the source station sends the frame in question. Immediately after that frame is acknowledged, the source station may send additional frames during the reconfigured period. Simulation and emulation are used to demonstrate and validate the adaptive protocol's capabilities. Results show that this new protocol offers substantial improvement in system throughput when the channel degrades to a point that reliable transmission of frames is not feasible in a standard IEEE 802.11 WLAN. Specifically, CATER continues to function, permitting up to 14 percent normalized aggregate throughput at times when IEEE 802.11 permits no frames to pass through the WLAN. In addition, throughput experiences only a small decrease due to protocol overhead during periods when stations experience a good channel with few bit errors. Moreover, CATER does not adversely affect the predominate transport layer protocol (i.e., TCP), and provides equitable service to all stations within the network. / Ph. D.

Wireless network devices, especially in ad hoc networks, are typically battery-powered. The growing need for energy efficiency in wireless networks, in general, and in mobile ad hoc networks (MANETs), in particular, calls for power enhancement features. The goal of this dissertation is to extend network lifetime by improving energy utilization in MANET routing. We utilize the ability of wireless network interface cards to dynamically change their transmission power, as well as the ability of wireless devices to read the remaining battery energy of the device to create a table of what we term "reluctance values," which the device uses to determine how to route packets. Choosing routes with lower reluctance values, on average and with time, leads to better utilization of the energy resources of the devices in the network. Our power-aware scheme can be applied to both reactive and proactive MANET routing protocols. As examples and to evaluate performance, the technique has been applied to the Dynamic Source Routing (DSR) protocol, a reactive routing protocol, and the Optimized Link State Routing (OLSR) protocol, a proactive routing protocol. Simulations have been carried out on large static and mobile networks. Results show improvements in network lifetime in static and certain mobile scenarios. Results also show better distribution of residual node energies at the end of simulations, which means that the scheme is balancing energy load more evenly across network nodes than the unmodified versions of DSR and OLSR. Average change in energy over time in the unmodified protocols show a steady increase with time, while the power-aware protocols show an increase in the beginning, then it levels for sometime before it starts to decrease. The power-aware scheme shows improvements in static and in coordinated mobility scenarios. In random mobility the power-aware protocols show no advantage over the unmodified protocols. / Ph. D.

Internetworking third generation (3G) technologies with wireless LAN (WLAN) technologies such as Universal Mobile Telecommunication Systems (UMTS) and IEEE 802.11, respectively, is an emerging trend in the wireless domain. Its development was aimed at increasing the UMTS network'­s capacity and optimizing performance. The increase in the number of wireless users requires an increase in the number of smaller WLAN cells in order to maintain an acceptable level of QoS. Deploying smaller cells in areas of higher mobility (e.g., campuses, subway stations, city blocks, malls, etc.) results in the user only spending a short period of time in each cell, which significantly increases the rate of handoff. If the user does not spend sufficient time in the discovered WLAN's coverage area, the application cannot benefit from the higher data rates. Therefore, the data interruption and performance degradation associated with the handoff cannot be compensated for. This counters the initial objective for integrating heterogeneous technologies, thus only handoffs that are followed by a sufficient visit to the discovered WLAN should be triggered. The conventional RF-based handoff decision method does not have the necessary means for making an accurate decision in the type of environments described above. Therefore, a location-aided handoff decision algorithm was developed to prevent the triggering of handoffs that result from short visits to discovered WLAN's ­ coverage area. The algorithm includes a location-based evaluation that runs on the network side and utilizes a user's location, speed, and direction as well as handoff-delay values to compute the minimum required visit duration and the user'­s trajectory. A WLAN coverage database is queried to determine whether the trajectory's end point falls within the boundaries of the discovered WLAN's coverage area. If so, the mobile node is notified by the UMTS network to trigger the handoff. Otherwise, the location-based evaluation reiterates until the estimated trajectory falls within the boundaries of the discovered WLAN'­s coverage area, or the user exits the coverage area. By taking into consideration more then merely RF-measurements, the proposed algorithm is able to predict whether the user'­s visit to the WLAN will exceed the minimum requirements and make the decision accordingly. This allows the algorithm to prevent the performance degradation and cost associated with unbeneficial/unnecessary handoffs. / Master of Science

Wireless Local Area Networks (WLAN) have proliferated in the last 5 years. The IEEE 802.11b products have become commonplace both in the residential and business places for untethered Internet access. However the end user experience has often been less satisfactory than what the technology can offer. The degradation in the performance of the system is mainly attributed to the poor network design. The current network design is primarily RF centric. There are two factors that need to be in the incorporated in the design. Firstly a clear understanding of the traffic sources in the network such as the peak load of the system is necessary. Secondly the design should account for the limitations of the indoor propagation such as interference and multipath. The goal of this thesis is to develop a simulator which will predict the performance (throughput) of an end user. The throughput is predicted for a given topology and traffic source. The simulator is built on object oriented design. To validate the simulator a measurement campaign was conducted. The campaign was conducted in two different channel conditions, office space and open hall. The channel measurements were also performed at these locations to understand the multipath. Comparative studies indicate that the choice of the rate adaptation algorithm hugely influences the predicted throughput. The simulator results match very well with the measurement results for the open space scenario. For the office space scenario the simulator varied by roughly 20% from the measurement results. This was due to existence of multipath leading to Inter Symbol Interference. / Master of Science

Software Defined Radio (SDR) is a growing technology that allows radio communication to become interoperable. SDR can lower the cost for a particular hardware radio to communicate with another radio that uses a different standard. In order to show the capability of SDR, this thesis shows how to implement IEEE 802.14.5, a low-rate wireless personal area network (LR-WPAN) standard, on a standalone embedded machine. The implementation is done using a universal software radio peripheral embedded, USRP E100, an open source software development toolkit for SDR, GNU Radio, and UCLA ZigBee PHY GNU Radio application. The implementation can be done on the regular non-embedded USRPs. However, without a fast host computer demodulating the packets, the USRP E100 cannot receive incoming packets. An available FPGA is used to solve this problem by doing a software-hardware hybrid design to allow the USRP E100 to communicate with other IEEE 802.15.4 devices. The final product is an IEEE 802.15.4 monitor software that detects messages from devices communicating using IEEE 802.15.4 in its range. In addition, recommendations are presented for improving SDR education and training, particularly for developers with backgrounds in disciplines other than communications engineering. / Master of Science

Typically a wireless LAN infrastructure is designed and installed by Networking professionals. These individuals are extremely familiar with wired networks, but are often unfamiliar with wireless networks. Thus, Wireless LAN installations are currently handicapped by the lack of an accurate, performance prediction model that is intuitive for use by non-wireless professionals. To provide a solution to this problem, this thesis presents a method of predicting the expected wireless LAN throughput using a site-specific model of an indoor environment. In order to develop this throughput prediction model, two wireless LAN throughput measurement products, LANFielder and SiteSpy, were created. These two products, which are patent pending, allow site-specific network performance measurements to be made. These two software packages were used to conduct an extensive measurement campaign to evaluate the performance of two IEEE 802.11b access points (APs) under ideal, multiuser, and interference scenarios. The data from this measurement campaign was then used to create empirically based throughput prediction models. The resulting models were first developed using RSSI measurements and then confirmed using predicted signal strength parameters. / Master of Science

Les techniques de communication coopératives ont été proposées pour améliorer la qualité des signaux reçus par les terminaux sans fil grâce au principe de diversité spatiale. Cette propriété est obtenue par une duplication du signal, envoyé par l’émetteur au niveau d’un terminal relais situé entre l’émetteur et le récepteur. Les travaux de recherche menés en communications coopératives concernent deux domaines principaux: certains traitent la transmission physique alors que d’autres sont étudient l’interaction de la couche physique avec les couches protocolaires supérieures, en particulier les niveaux MAC (Medium Access Control) et réseau. Si ces domaines de recherche sont généralement séparés, des études conjointes s’avèrent nécessaires pour obtenir des systèmes coopératifs implantables. C’est dans ce contexte que se situent les travaux de la thèse avec, comme cadre applicatif, les réseaux ad hoc. En premier lieu, dans la mesure où il n’existe pas de modèle complet de système coopératif, un cadre de modélisation original est proposé pour représenter le fonctionnement d’un système coopératif, sa mise en place et son fonctionnement. Une caractéristique du modèle est de faire abstraction des couches protocolaires. Cette façon de procéder permet d’analyser de façon similaire différentes solutions proposées dans la littérature. De plus, ce modèle facilite la conception de solutions coopératives, en particulier la conception du processus de mise en place du système de coopération qui initialise les rôles de relais, destinataire et source en fonctionnement coopératif. Le modèle de système coopératif est utilisé pour la conception d’une solution de transmission coopérative adaptative où le relais agit en tant que proxy entre la source et le destinataire. L’intérêt de notre proposition, ProxyCoop, par rapport à d’autres propositions, est d’être compatible avec le protocole IEEE 802.11 que ce soit dans son mode de base ou dans son mode optionnel. Pour chaque trame, le mode de transmission à la source est dynamiquement défini soit en mode proxy coopératif soit en mode non coopératif, et ce en fonction de la réception ou la non réception d’un acquittement du destinataire. Les résultats de simulation montrent, sous certaines conditions, une amélioration des performances en termes de nombre de trames effectivement reçues. Le nombre de retransmissions dues à des trames reçues erronées est diminué, et les transmissions en mode multi saut, coûteuses en temps et en bande passante sont également diminuées. Les conditions favorables à la coopération sont dépendantes de la qualité et de l’accessibilité du canal. Une méthode pour la mise en place du système coopératif est également proposée. Elle repose sur l’utilisation d’un protocole standard de routage pour réseaux ad hoc, AODV. Les évaluations de performances indiquent que la mise en place du système de coopération coûte peu en termes de bande passante, les performances du système (mise en place et fonctionnement) sont supérieures à celles d’un système non-coopératif, pour des conditions données. Finalement, l’application de la solution proposée à un réseau ad hoc spécifique, un réseau maillé (mesh) conforme au standard IEEE 802.11s illustre où et comment déployer la solution proposée. / Cooperative communication techniques have been proposed in order to improve the quality of the received signals at the receivers by using the diversity added by duplication of signals sent by relay terminals situated between each transmission pair. Researches related to cooperative communication can be categorized into two fields; Cooperative transmissions and Cooperative setup. The first research field concerns with cooperative transmission techniques in the physical layer while the second research field concerns with issues on inter-layer interaction between cooperative transmissions in the physical layer to protocols in the upper layers (especially the MAC layer and the network layer). These research topics have been separately concerned but, for implementations, they have to work together. Since there is not any existing common frame work to describe entire functions in cooperative communication, we proposed an original framework of cooperative network at the system level called “Cooperative Network Model”. The model does not reflect the protocol layering; thus, we can generalize the cooperation process and obtain an analysis that is available for many solutions. For validity, the proposed model can clearly illustrate and systematically describe existing cooperative setup protocols. In addition, the proposed cooperative network model facilitates us to find and to solve problems in cooperative designs; especially in cooperative setup, which is in charge on the initiation of the terminal’s role (i.e., a source, a relay, and a destination terminal). Thus, we believe that this model can facilitate the design and updating of existing and future propositions in this domain. The cooperative network protocol is used to design an adaptive cooperative transmission called Proxy Cooperative Transmission. In contrast to other adaptive cooperative transmission techniques, our proposition is compatible to both of the basic access mode and the optional access mode of IEEE 802.11 Medium Access Control (MAC) protocol. The transmission mode for each data frame is adaptively switched between a proxy cooperative mode and a non-cooperative mode based on the absence of acknowledge (ACK) frame. Simulation results show that transmission performance is improved by decreasing the number of re-transmissions due to frame errors; thus, chances of multi-hop mode transitions that are costly in time and bandwidth are alleviated. Then, in order to fulfill ProxyCoop communications in part of cooperative setup, we propose a cooperative setup method called “Proxy Cooperative Setup”. The proposition is based on a routing standard protocol for ad hoc networks, AODV, so that it could be easily deployed. The impacts of ProxyCoopSetup when it works with ProxyCoop transmissions have been studied. From simulation results, it shows that ProxyCoop transmissions with ProxyCoopSetup has similar performance to the ProxyCoop transmissions without ProxyCoopSetup. Finally, when the implementation of the proxy cooperative communication and how it can be integrated on existing networks have been considered, it is shown that the design of proxy cooperative communication is also valuable for the 802.11s WLAN Mesh Network environments.

O projeto de malhas de aterramento requer o cálculo da resistência de aterramento e dos potenciais na superfície do solo. Quando o método das imagens é utilizado para este cálculo o modelo típico do solo é uma estratificação horizontal em 2 camadas. A extensão do método das imagens para solos com múltiplas camadas horizontais apresenta problemas numéricos importantes, de forma que a técnica de imagens complexas foi utilizada para permitir este cálculo, porém restringindo a posição dos eletrodos à primeira camada. Este trabalho objetiva a aplicação do método de imagens complexas a eletrodos situados em qualquer camada de solos com estratificação horizontal, deduzindo as funções kernel para posições arbitrárias da fonte e do objeto e determinando os resíduos e pólos das imagens utilizando a decomposição em autovalores e autovetores. Foi desenvolvido um programa que calcula a resistência de aterramento e os potenciais na superfície do solo para solos com até 4 camadas. Foram realizadas comparações com outros trabalhos publicados e os resultados obtidos permitem validar o uso do programa para esta aplicação. / Grounding grid design requires both ground resistance and surface potential. Traditional method of images restricts this calculation to two layer soils. Complex image method allows calculation of both resistance values and potentials at the soil surface, in multilayer soils with horizontal stratification, without grounding grid position limitation. This work presents a complete methodology for calculation of safety aspects of grounding grid design, validating results by comparison with published previous work.

Le cadre de cette thèse est l'étude des systèmes contrôlés en réseau sans fil (SCRSF) qui utilise la technologie IEEE 802.15.4. Le premier objectif est d'étudier la pertinence de l'utilisation du réseau de type IEEE 802.15.4 pour les SCRSF puis de proposer et d'évaluer des mécanismes pour garantir la Qualité de Service (QdS) offerte par le réseau au système contrôlé. Nous analysons l'utilisation des slots temporels réservés (GTS) dans le cadre des SCRSF et les contraintes qui en découlent. De plus, nous proposons des mécanismes de gestion de la QdS avec priorité aussi bien pour le mode avec balise que pour le mode sans balise du protocole IEEE 802.15.4. Ces propositions ont été validées par des simulations et une partie de manière analytique. Notre deuxième objectif est de concevoir, d'une manière conjointe, les SCRSF pour pouvoir régler en ligne la QdS offerte par le réseau en fonction de la Qualité de Contrôle (QdC) du système contrôlé. Nous proposons des protocoles d'adaptation en ligne de la QdS du réseau qui prennent en compte la QdC du système contrôlé. Ces protocoles ont été validés par simulations et une implémentation réelle de chacun d'eux est proposée / In this thesis, we study wireless networked control systems (WNCS) which use the IEEE 802.15.4 technology. The first objective is to study the pertinence of the use of the IEEE 802.15.4 for the WNCS, then to propose and evaluate QoS management mechanisms which guarantee the Quality of Service (QoS) offered by network to the controlled system. We analyse the use of the guaranteed temporel slots (GTS) for WNCS and in which conditions it is possible. We propose QoS management mechanisms with priority for both the beacon enabled mode and the non-beacon enabled mode of the IEEE 802.15.4 protocol. These proposals are validated through simulations and partially with analytical approach. The second objective is to design the WNCS so that the QoS offered by the network is adated online depending on the Quality of Control (QoC) on the controlled system. We propose QoS online adaptation protocols which take as parameter the QoC of the system. These protocols are validated through simulations and a realistic implementation of them is proposed