Um novo circuito amplificador de 50 MHz - 1 GHz com alta linearidade para o padrão IEEE 802.22 “wireless regional area” (WRAN) é apresentado. Ele foi implementado sem nenhum indutor e oferece uma saída diferencial para ser utilizada como balun. Técnicas de cancelamento de ruído e aumento de linearidade foram usadas para melhorar a performace do amplificador de modo que eles pudessem ser otimizados separadamente. A linearidade foi melhorada utilizando transistores conectados como diodo. O amplificador foi implementado em um processo CMOS 130 nm, em uma área compacta de 136 m x 71 m. As simulações são apresentadas para esquemáticos pós-leiaute para duas classes diferentes de projeto: um visando a melhor linearidade e o outro a melhor Figura de Ruído (FR). Quando otimizado para melhor linearidade, os resultados de simulação atingem um ganho de tensão > 23.7 dB (ganho de potência > 19.1 dB), uma figura de ruído < 3.6 dB na banda inteira (com 2.4 dB min), um ponto de intersecção de terceira ordem (IIP3) > 3.3 dBm (7.6 dBm max) e um coeficiente de reflexão de entrada S11 < -16 dB. Quando otimizado para melhor figura de ruído, ele atinge um ganho de tensão > 24.7 dB (ganho de potência > 19.8 dB), uma FR < 2 dB na banda inteira, um IIP3 > -0.3 dBm e um S11 < -11 dB. Resultados de simulação Monte Carlo confirmam baixa sensibilidade à variabilidade de processo. Além disso, uma baixa sensibilidade com a temperatura na faixa de -55 até 125 C foi observada para Ganho, FR e S11. Consumo de potência é 17.6 mA sob fonte de alimentação de 1.2 V. / A new 50 MHz - 1 GHz low-noise amplifier circuit with high linearity for IEEE 802.22 wireless regional area network (WRAN) is presented. It was implemented without any inductor and offers a differential output for balun use. Noise cancelling and linearity boosting techniques were used to improve the amplifier performance in a way they can be separately optimized. Linearity was improved using diode-connected transistors. The amplifier was implemented in a 130 nm CMOS process in a compact 136 m x 71 m area. Simulations are presented for post-layout schematics for two classes of design: one for best linearity, another for best noise figure (NF). When optimized for best linearity, simulation results achieve a voltage gain > 23.7 dB (power gain > 19.1 dB), a NF < 3.6 dB over the entire band (with 2.4 dB min figure), an input third-order intercept point (IIP3) > 3.3 dBm (7.6 dBm max.) and an input power reflection coefficient S11 < -16 dB. When optimized for best NF, it achieves a voltage gain > 24.7 dB (power gain > 19.8 dB), a NF < 2 dB over the entire band, an IIP3 > -0.3 dBm and an S11 < -11 dB. Monte Carlo simulation results confirm low sensitivity to process variations. Also a low sensitivity to temperature within the range -55 to 125 C was observed for Gain, NF and S11. Power consumption is 17.6 mA under a 1.2 V supply.

The development of the IEEE 802.22 standard is aimed at providing broadband access in rural areas by effectively utilizing the unused TV band, provided no harmful interference is caused to the incumbent operation. This thesis presents the analytical framework to evaluate the number of active customer premise equipments (CPEs) in a wireless regional area network. Initial ranging is the primary process in IEEE 802.22 networks for CPEs to access the network and establish their connections with the base station (BS). A comprehensive analysis of initial ranging mechanism is provided in this work and initial ranging request success probability is derived based on the number of contended CPEs and the initial contention window size. Further, the average ranging success delay is derived for the maximum backoff stages. The collision probability is highly dependent on the size of the initial contention window and the number of contended CPEs. To keep it at a specific level, it is necessary for the BS to schedule the required size of the initial contention window to facilitate the maximum number of CPEs to establish their connections with reasonable delay. Therefore, the optimized initial window size is proposed that meets the collision probability constraint for a particular number of contended CPEs. An analytical model is also developed to estimate the ranging request collision probability depending upon the size of initial contention window and the number of contended CPEs. Moreover, this approximation provides the threshold size for contention window to start the initial ranging process in the IEEE 802.22 network. / Bahauddin Zakariya University Multan, Pakistan.

Given the ever increasing reliance of today’s society on ubiquitous wireless access, the paradigm of dynamic spectrum access (DSA) as been proposed and implemented for utilizing the limited wireless spectrum more efficiently. Orthogonal frequency division multiplexing (OFDM) is growing in popularity for adoption into wireless services employing DSA frame- work, due to its high bandwidth efficiency and resiliency to multipath fading. While these advantages have been proven for many wireless applications, including LTE-Advanced and numerous IEEE wireless standards, one potential drawback of OFDM or its non-contiguous variant, NC-OFDM, is that it exhibits high peak-to-average power ratios (PAPR), which can induce in-band and out-of-band (OOB) distortions when the peaks of the waveform enter the compression region of the transmitter power amplifier (PA). Such OOB emissions can interfere with existing neighboring transmissions, and thereby severely deteriorate the reliability of the DSA network. A performance-enhancing digital pre-distortion (DPD) technique compensating for PA and in-phase/quadrature (I/Q) modulator distortions is proposed in this dissertation. Al- though substantial research efforts into designing DPD schemes have already been presented in the open literature, there still exists numerous opportunities to further improve upon the performance of OOB suppression for NC-OFDM transmission in the presence of RF front-end impairments. A set of orthogonal polynomial basis functions is proposed in this dissertation together with a simplified joint DPD structure. A performance analysis is presented to show that the OOB emissions is reduced to approximately 50 dBc with proposed algorithms employed during NC-OFDM transmission. Furthermore, a novel and intuitive DPD solution that can minimize the power regrowth at any pre-specified frequency in the spurious domain is proposed in this dissertation. Conventional DPD methods have been proven to be able to effectively reduce the OOB emissions that fall on top of adjacent channels. However more spectral emissions in more distant frequency ranges are generated by employing such DPD solutions, which are potentially in violation of the spurious emission limit. At the same time, the emissions in adjacent channel must be kept under the OOB limit. To the best of the author’s knowledge, there has not been extensive research conducted on this topic. Mathematical derivation procedures of the proposed algorithm are provided for both memoryless nonlinear model and memory-based nonlinear model. Simulation results show that the proposed method is able to provide a good balance of OOB emissions and emissions in the far out spurious domain, by reducing the spurious emissions by 4-5 dB while maintaining the adjacent channel leakage ratio (ACLR) improvement by at least 10 dB, comparing to the PA output spectrum without any DPD.

Cognitive radio is frequently touted as a platform for implementing dynamic distributed radio resource management algorithms. In the envisioned scenarios, radios react to measurements of the network state and change their operation according to some goal driven algorithm. Ideally this flexibility and reactivity yields tremendous gains in performance. However, when the adaptations of the radios also change the network state, an interactive decision process is spawned and once desirable algorithms can lead to catastrophic failures when deployed in a network. This document presents techniques for modeling and analyzing the interactions of cognitive radio for the purpose of improving the design of cognitive radio and distributed radio resource management algorithms with particular interest towards characterizing the algorithms' steady-state, convergence, and stability properties. This is accomplished by combining traditional engineering and nonlinear programming analysis techniques with techniques from game to create a powerful model based approach that permits rapid characterization of a cognitive radio algorithm's properties. Insights gleaned from these models are used to establish novel design guidelines for cognitive radio design and powerful low-complexity cognitive radio algorithms. This research led to the creation of a new model of cognitive radio network behavior, an extensive number of new results related to the convergence, stability, and identification of potential and supermodular games, numerous design guidelines, and several novel algorithms related to power control, dynamic frequency selection, interference avoidance, and network formation. It is believed that by applying the analysis techniques and the design guidelines presented in this document, any wireless engineer will be able to quickly develop cognitive radio and distributed radio resource management algorithms that will significantly improve spectral efficiency and network and device performance while removing the need for significant post-deployment site management. / Ph. D.

Computer networks are in the scope of the IEEE organization normalized by the 802 board which currently comprises six working groups for wireless communications. IEEE 802.11 for wireless local area networks, IEEE  802.15 for wireless personal area networks, IEEE 802.16 for wireless metropolitan area networks, IEEE 802.20 for mobile broadband wireless access, IEEE 802.21 for media independent handover and IEEE 802.22 for wireless regional area networks. This master's thesis focuses on a security analysis of particular standards, describes threats, vulnerabilities, current security measures and mutually compares wireless specifications from a security point of view. The conclusion is devoted to overall evaluation of the project, to its contributions, possible enhancements and continuation in the form of consequential studies.