<p>The purpose of the project was to develop the hardware to a microwave wireless system working </p><p>at the frequency 2.45 GHz. The functionality of the system should also be easy to understand </p><p>since the system is to be used in an educational purpose. Much time has been spent impedance </p><p>matching components, a task that proved to be harder than we expected. Other work that has been </p><p>is layout of all parts, filter construction and the writing of an easy to understand thesis. After the </p><p>parts had been completed, they were tested in a network analyzer and/or spectrum analyzer. </p><p>Successful full system test has been done up to 400 meters, the length the system is to be used </p><p>for.</p>

The purpose of the project was to develop the hardware to a microwave wireless system working at the frequency 2.45 GHz. The functionality of the system should also be easy to understand since the system is to be used in an educational purpose. Much time has been spent impedance matching components, a task that proved to be harder than we expected. Other work that has been is layout of all parts, filter construction and the writing of an easy to understand thesis. After the parts had been completed, they were tested in a network analyzer and/or spectrum analyzer. Successful full system test has been done up to 400 meters, the length the system is to be used for.

Le problème de la synchronisation en temps et en fréquence dans un système de transmission OFDM (Orthogonal Frequency Division Multiplexing) sans fil de type IEEE 802.11a est étudié. Afin d'améliorer la synchronisation de trame entre les stations mobiles, bien que des solutions aient déjà été proposées pour compenser les décalages en temps et en fréquence, nous avons développé une nouvelle approche conforme à la norme IEEE 802.11a. Cette approche exploite non seulement les informations habituellement spécifiées par la norme à savoir les séquences d’apprentissage mais également d’autres sources d’informations disponibles au niveau de la couche physique et par ailleurs connues par l'émetteur et le récepteur qui les exploitera. Tenant compte des informations fournies par les protocoles réseaux, nous avons montré que les différents sous-champs du champ SIGINAL de la trame physique, identifié comme séquence de référence, sont connus ou prédictibles à partir des deux trames de contrôle RTS (Request to Send) et CtS (Clear to Send) lorsque le mécanisme de réservation de support CSMA/CA (Transporteur Sense Multiple Access avec évitement de collision) est activé conjointement à des algorithmes d'adaptation de débit binaire sur le canal. De plus, la trame RTS reçue permet au récepteur d'estimer le canal avant d’entamer l'étape de synchronisation. Tenant compte de la connaissance sur le champ SIGNAL et de l'information sur le canal de transmission, nous avons développé plusieurs algorithmes conjoints de synchronisation temporelle et fréquentielle et d’estimation de canal compatible avec la norme 802.11a. Les résultats de simulation montrent une amélioration conséquente des performances en termes de probabilité d’échec de synchronisation en comparaison avec les algorithmes existants. / Time and frequency synchronization problem in the IEEE 802.11a OFDM (Orthogonal Frequency Division Multiplexing) wireless communication system is investigated. To enhance the frame synchronization between mobile stations, although solutions to compensate time and frequency offsets have already been proposed, we developed a new approach conform to the IEEE 802.11a standard. This approach exploits not only the reference information usually specified by the standard such as training sequences but also additional sources of information available at the physical layer further known by both the transmitter and receiver to be then exploited. According to the knowledge protocol, we showed that the parts of the identified SIGNAL field considered as a reference sequence of the physical frame are either known or predictable from the RtS (Request to Send) and CtS (Clear to Send) control frames when the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) mechanism is triggered jointly to bit-rate adaptation algorithms to the channel. Moreover the received RtS control frame allows the receiver to estimate the channel before synchronization stage. According to the knowledge of the SIGNAL field and the channel information, we developed multistage joint time/frequency synchronization and channel estimation algorithms conform to the standard. Simulation results showed a strongly improved performance in terms of synchronization failure probability in comparison with the existing algorithms.

This thesis describes user interface and visualization components in the problem solving environment "Site-Specific System Simulator for Wireless System Design" (S4W) developed by CS and ECE faculty and students at Virginia Tech. S4W integrates visualization and computational tools with a high level user interface. The objective of this PSE is to improve the ability of wireless design engineers to design an indoor wireless system through the aid of various simulation and visualization components. S4W provides engineers with the facility of thinking in terms of the overall task of designing the system for optimal performance. They need not to worry about computation, data-management and connectivity issues. The choice of method for interaction between service logic within a PSE and its user is always a challenging issue. The selection of user interaction channel is mostly dictated by the characteristics of the problem domain. For S4W, we chose to build a graphical user interface as human interaction interface, which was connected to other components via a high speed Local Area Network (LAN). The other key form of user interaction in a PSE is the visual representations of the abstract data results of simulations, perceived as user interface for data. The Complex nature of data sets in the domain of wireless simulations calls for a customized set of visualization tools. To address the specific needs of visualizations for S4W, ad hoc visualization tools were developed and integrated into the graphical user interface. A comparison of the integrated PSE and an earlier collection of unintegrated tools and scripts is presented. / Master of Science

- / -

- / -

- / -

No description available.

No description available.

<p>After more than two decades’ development, modern mobile cellular networks now have almost approached to the commercial level of fourth generation communication networks. For each of the mobile solutions, there are special attributes but also similarities compared to the other competitive solutions. We can also find relationships between the old generation solutions and the inheritors or innovations.</p><p>During the communicating session using any kind of existing mobile handset, the handover procedure is a very important one that may effect connection quality and also the phone call continuity. Nowadays, the mobile cellular networks have a trend to interact with LAN networks. They will co-exist and work together to support higher data rate over a wider coverage. Seamless handover proposals like Unlicensed Mobile Access (UMA) can support the heterogeneous handover between Global System for Mobile Communications (GSM) and Wireless (Wi-Fi) Network. Several Media Independent Handover (MIH) proposals can handle the vertical handover in the hybrid mobile data network environment such like between wireless local area network (WLAN) and Universal Mobile Telecommunications System (UMTS) by different solutions.</p>