With the rapid development of information technology, more and more bandwidth is required to transmit multimedia data. Since local communication networks are moving to wireless domain, it brings up great challenges for making integrated wideband wireless front-ends suitable for these applications. RF filtering is a fundamental need in all wireless front-ends and is one of the most difficult parts to be integrated. This has been a major obstacle to the implementation of low power and low cost integrated wireless terminals. <p> Lots of previous work has been done to make integrated RF filters applicable to these applications. However, some of these filters are not designed with standard CMOS technology. Some of them are not designed in desired frequency bands and others do not have sufficient frequency bandwidth. This research demonstrates the design of a tunable wideband RF filter that operates at 3.6 GHz and can be easily changed to a higher frequency range up to 5 GHz. This filter is superior to the previous designs in the following aspects: a) wider bandwidth, b) easier to tune, c) balancing in noise and linearity, and d) using standard CMOS technology. The design employs the state-of-the-art inductor degenerated LNA, acting as a transconductor to minimize the overall noise figure. A Q-enhancement circuit is employed to compensate the loss from lossy on-chip spiral inductors. Center frequency and bandwidth tuning circuits are also embedded to make the filter suitable for multi band operations. <p> At first, a second order bandpass filter prototype was designed in the standard 0.18 ìm CMOS process. Simulation results showed that at 3.6 GHz center frequency and with a 60-MHz bandwidth, the input third-order intermodulation product (IIP3) and input-referred 1 dB compression point (P1dB) was -22.5 dBm and -30.5 dBm respectively. The image rejection at 500 MHz away from the center frequency was 32 dB (250 MHz intermediate frequency). The Q of the filter was tunable over 3000 and the center frequency tuning range was about 150 MHz. <p> By cascading three stages of second order filters, a sixth order filter was designed to enhance the image rejection ability and to extend the filter bandwidth. The sixth order filter had been fabricated in the standard 0.18 ìm CMOS process using 1.8-V supply. The chip occupies only 0.9 mm 0.9 mm silicon area and has a power consumption of 130-mW. The measured center frequency was tunable from 3.54 GHz to 3.88 GHz, bandwidth was tunable from 35 MHz to 80 MHz. With a 65 MHz bandwidth, the filter had a gain of 13 dB, an IIP3 of -29 dBm and a P1dB of -46 dBm.

Future generation wireless networks are envisioned to provide ubiquitous networking to a wide number of mobile users, promising them the ability to access the various data networks anywhere and anytime. Such networks have motivated the research into efficient management and allocation of the wireless network's limited resources. Heterogeneity also exists amongst the subscribers, i.e. there are those who are willing to spend a little extra on their subscriptions in the prospect of obtaining a better level of service. This work proposes a framework for efficient resource management, while satisfying the heterogeneous QoS demands of the different subscribers. Part of the proposed framework was used to generate mathematical models for the purpose of analyzing the behavior of the system under two different resource management schemes. / February 2006

Wireless ad hoc networks have been emerged to support applications, in which it is required/desired to have wireless ommunications among a variety of devices without relying on any infrastructure or central managements. In ad hoc networks, wireless devices, simply called nodes, have limited transmission range. Therefore, each node can directly communicate with only those within its transmission range and requires other nodes to act as routers in order to communicate with out-of-range estinations. One of the fundamental operations in ad hoc networks is broadcasting, where a node sends a message to all other nodes in the network. This can be achieved through flooding, in which every node transmits the first copy of the received message. However, flooding can impose a large number of redundant transmissions, which can result in significant waste of constrained resources such as bandwidth and battery power. One of the contributions of this work is to propose efficient broadcast algorithms which can significantly reduce the number of redundant transmissions. We also consider some of the security issues of ad hoc networks. In particular, we carefully analyze the effect of the wormhole attack, which is one of the most severe threats against ad hoc networks. We also propose a countermeasure, which is an improvement over the existing timing-based solutions against the wormhole attack. Finally, in the last chapter, we propose novel point compression techniques which can be used in Elliptic Curve Cryptography (ECC). ECC can provide the same level of security as other public key cryptosystems (such as RSA) with substantially smaller key sizes. Smaller keys can result in smaller system parameters, bandwidth savings, faster implementations and lower power consumption. These advantages make ECC interesting for ad hoc networks with restricted devices.

Les tecnologies sense fils han provocat una important revolució en el món de les xarxes i serveis de telecomunicació. Han apareguts nous sistemes com els telèfons mòbils d'última generació o les xarxes LAN sense fils que han estat acceptats amb entusiasme per la població. En particular, l'ús de xarxes de sensors (per controlar la temperatura, per a detectar places lliures d'aparcament, etc.) està creixent ràpidament . Aquesta tesi es centra en el disseny d'antenes per a xarxes de sensors distribuïts. En concret s'analitza un sistema on els sensors remots estan connectats a una unitat central utilitzant un radio enllaç operant en la banda ISM de 5,8 GHz, i la unitat central envia la informació recollida a Internet a través d'una connexió WLAN. A la unitat central es necessiten antenes multibanda per cobrir diverses bandes de freqüències amb un únic element radiant. En aquesta tesi es presenten dues solucions per obtenir aquest comportament multibanda: Monopols amb pla de massa fractal i monopols carregats amb ressonadors. S'han fabricat i mesurat diferents prototips que cobreixen les necessitats del sistema. Els sensors han de ser dispositius de reduïdes dimensions i baix cost. Una bona opció per aconseguir aquests requisits és l'ús d'antenes integrades en silici fabricades amb una tecnologia CMOS estàndard. En primer lloc s'analitzen els principals problemes de la integració de l'antena en silici, i a continuació es presenta una possible solució per millorar l'eficiència juntament amb un estudi de la degradació introduïda per altres components quan aquests es fabriquen en el mateix xip que l’antena. Les mesures dels prototips fabricats demostren que la integració de l'antena en la banda de 5,8 GHz és factible, obtenint un abast d'alguns metres. Cada vegada és una realitat més propera el fet de tenir sensors implantats en el cos. Per aquest motiu, l’última part d'aquesta tesi es dedica a estudiar els efectes del cos sobre antenes situades en el seu interior i avaluar les pèrdues de propagació addicionals introduïdes pels teixits humans. / Las tecnologías inalámbricas han provocado una importante revolución en el mundo de las redes y servicios de telecomunicación. Han aparecidos nuevos sistemas, como los teléfonos móviles de última generación o las redes LAN inalámbricas, que han sido aceptados con entusiasmo por la población. En particular, el uso de redes de sensores (para controlar la temperatura, para detectar plazas libres de aparcamiento, etc.) está creciendo rápidamente. Esta tesis se centra en el diseño de antenas para redes de sensores inalámbricos distribuidos. EN concreto se analiza un sistema donde los sensores están conectados a una unidad central utilizando un enlace inalámbrico en la banda ISM de 5.8 GHz, y la unidad central envía la información recogida a Internet a través de una conexión WLAN. En la unidad central se necesitan antenas multibanda para dar servicio a varias bandas de frecuencias con un único elemento radiante. En esta tesis se presentan dos soluciones para obtener este comportamiento multibanda: Monopolos con plano de masa fractal y monopolos cargados con resonadores. Se han fabricado y medido diferentes prototipos que cubren las necesidades del sistema. En los sensores se desean dispositivos de reducidas dimensiones y bajo coste. Una buena opción para lograr estos requisitos es el uso de antenas integradas en silicio fabricadas con una tecnología CMOS estándar. En primer lugar se analizan los principales problemas de la integración de la antena en silicio, y a continuación se presenta una posible solución para mejorar la eficiencia de radiación junto con un estudio de la degradación introducida por otros componentes cuando éstos se fabrican en el mismo chip que la antena. Las medidas de los prototipos fabricados demuestran que la integración de la antena en la banda de 5,8 GHz usando una tecnología CMOS es factible, obteniendo unos alcances de algunos metros incluso cuando la antena se fabrica junto con otros elementos integrados en el mismo chip. Cada vez es una realidad más cercana el hecho de poder tener sensores implantados en el cuerpo. Por este motivo, la última parte de esta tesis se dedica a estudiar los efectos del cuerpo sobre antenas situadas en su interior y evaluar las pérdidas de propagación adicionales introducida por los tejidos humanos. / Wireless technologies have triggered an important revolution in the world of telecommunication networks and services. New systems, such as the latest generation mobile phones or wireless LANs, have appeared being enthusiastically accepted by people. In particular, applications related to remote sensor networks are growing rapidly (for temperature monitoring, the detection of free parking spaces, etc.). This thesis is focused on antenna design for distributed wireless sensor networks. The remote sensors we are considering are connected to a central unit using a wireless link in the 5.8 GHz ISM band and the central unit transmits the collected information to the Internet via a WLAN connection. In the central unit multiband antennas are necessary to cover several frequency bands with a single radiating element. Two solutions to obtain this multiband performance are proposed: fractal-based ground planes and resonator loaded monopoles. Several novel antennas that easily meet the system requirements are manufactured and measured. For remote sensors small dimensions and low costs are desired. The use of silicon integrated antennas fabricated with standard CMOS technology is a good choice to achieve these requirements. First, the main problems of antenna integration are discussed and, then a possible solution to improve the antenna efficiency is presented together with a study of the effects of other elements integrated in the same chip with the antenna. The measurements of the manufactured prototypes demonstrate that antenna integration at 5.8 GHz is feasible, and that system ranges of some meters can be obtained even when the antenna is fabricated together with other elements integrated in the same chip. The possibility of having some of the sensors implanted inside the body will be a reality in the near future, for this reason the particular case of implanted antennas is also analyzed. The last part of this thesis is devoted to study the body effects on antenna performance and evaluate the additional propagation losses introduced by the body tissues.

Cooperative diversity has been proposed as a powerful means to enhance the performance of high-rate communications over wireless fading channels. It realizes spatial diversity advantages in a distributed manner where two or more nodes share their antennas to mimic a virtual antenna array.

Peer-to-Peer networking technology is evolving rapidly. P2P networks overcome the limitations of client/server networks where each computer shares resources of other computer. There are different types of P2P networks depending upon their functionalities. Peer to peer networks provide long list of features like: selection of nearby peers, redundant storage, effi-cient search/location of data items, data performance or guarantees etc. It is important to see that how P2P can work with wireless ad hoc networks and why it is important. What are im-portant issues which come across by using P2P and wireless ad hoc networks together. How TCP/IP stack can be affected. How the whole system looks like in which P2P techniques are used with wireless ad hoc routing protocols to perform different tasks and services.

Cooperative diversity has been proposed as a powerful means to enhance the performance of high-rate communications over wireless fading channels. It realizes spatial diversity advantages in a distributed manner where two or more nodes share their antennas to mimic a virtual antenna array.

Although most work on Wireless Mesh Networks (WMNs) has focused on traffic flowing in and out of the network via gateways, traffic within the WMN may also be significant in many environments. This point-to-point (P2P) traffic between the nodes within WMN can be handled in different ways, particularly in WMNs containing multiple gateways. The approach used affects the performance of both the P2P flows and other traffic in the network. This work studies the impact of handling P2P traffic in the presence of gateways and gateway traffic. Through mathematical analysis of the resulting traffic patterns, along with extensive simulations, the need to route P2P traffic appropriately is demonstrated. While direct routing yields considerable performance improvements in small networks, it can actually decrease capacity in larger networks. Consequently, we extend the Hybrid Wireless Mesh Protocol (HWMP) proposed in IEEE 802.11s by adding two new message types to obtain more information useful for choosing the best route. Through simulations on different networks, HWMP shows better average delivery ratio and end-to-end delay than the original gateway-based and the P2P routing mechanisms in the simulation settings.

As the data rates and performance of current telecommunications technologies reach their limits, MIMO offers promising results allowing for higher spectral efficiencies (or capacities) through the use of multiple element antennas (MEAs). Conventional testing methods, however, cannot be used for multi-antenna systems due to the co-dependence of antenna and RF effects, and baseband hardware and software design. This dissertation specifies a novel MIMO-OFDM, BLAST-based testing design using a hybrid FPGA/DSP development platform from Lyrtech. The design allows for rapid implementation and a consistent indication of the channel impulse response. In addition, a multipath environment is further created to mimic a realistic high scattering scenario. A study of MIMO system capacity is performed along with measurements of an actual over-the-air (OTA) channel. Observations about capacity and the effect of MEA antenna separations are then drawn and conclusions made as to the overall ability to effectively test MIMO systems. The platform used is the result of efforts from several individuals within UW's CST group. My contributions and research are documented in this dissertation.

Pilot Symbol Assisted Modulation (PSAM) is a good method to compensate for the channel fading effect in wireless mobile communications. In PSAM, known pilot symbols are periodically inserted into the transmitted data symbol stream and the receiver uses these symbols to derive amplitude and phase reference. <p> One aspect of this procedure, which has not received much attention yet, is the frame synchronization, i.e. the method used by the receiver to locate the time position of the pilot symbols. In this study, two novel non-coherent frame synchronization methods are introduced in which only the magnitude of received signal is used to obtain the timing of the pilot symbol. The methods are evaluated for both AWGN and frequency non-selective slow Rayleigh fading channels. <p> One synchronization technique is derived by standard maximum likelihood (ML) estimation formulation, and the other is obtained by using maximum a Posteriori probability (MAP) with a threshold test. Signal processing in the receiver uses simplifying approximations that rely on relatively high signal-to-noise ratio (SNR) as consistent with the reception of 16-QAM. Computer simulation has been used to test the acquisition time performance and the probability of false acquisition. Several lengths and patterns of pilot symbol sequences were tested where every 10th symbol was a pilot symbol and all other symbols were randomly selected data symbols. When compared with the other published synchronizers, results from this study show better performance in both AWGN and fading channels. Significantly better performance is observed in the presence of receiver frequency offsets.