Cognitive Radio (CR) has received tremendous research attention over the past decade, both in the academia and industry, as it is envisioned as a promising solution to the problem of spectrum scarcity. ACR is a device that senses the spectrum for occupancy by licensed users(also called as primary users), and transmits its data only when the spectrum is sensed to be available. For the efficient utilization of the spectrum while also guaranteeing adequate protection to the licensed user from harmful interference, the CR should be able to sense the spectrum for primary occupancy quickly as well as accurately. This makes Spectrum Sensing(SS) one of the where the goal is to test whether the primary user is inactive(the null or noise-only hypothesis), or not (the alternate or signal-present hypothesis). Computational simplicity, robustness to uncertainties in the knowledge of various noise, signal, and fading parameters, and ability to handle interference or other source of non-Gaussian noise are some of the desirable features of a SS unit in a CR. In many practical applications, CR devices can exploit known structure in the primary signal. IntheIEEE802.22CR standard, the primary signal is a wideband signal, but with a strong narrowband pilot component. In other applications, such as military communications, and blue tooth, the primary signal uses a Frequency Hopping (FH)transmission. These applications can significantly benefit from detection schemes that are tailored for detecting the corresponding primary signals. This thesis develops novel detection schemes and rigorous performance analysis of these primary signals in the presence of fading. For example, in the case of wideband primary signals with a strong narrowband pilot, this thesis answers the further question of whether to use the entire wideband for signal detection, or whether to filter out the pilot signal and use narrowband signal detection. The question is interesting because the fading characteristics of wideband and narrowband signals are fundamentally different. Due to this, it is not obvious which detection scheme will perform better in practical fading environments. At another end of the gamut of SS algorithms, when the CR has no knowledge of the structure or statistics of the primary signal, and when the noise variance is known, Energy Detection (ED) is known to be optimal for SS. However, the performance of the ED is not robust to uncertainties in the noise statistics or under different possible primary signal models. In this case, a natural way to pose the SS problem is as a Goodness-of-Fit Test (GoFT), where the idea is to either accept or reject the noise-only hypothesis. This thesis designs and studies the performance of GoFTs when the noise statistics can even be non-Gaussian, and with heavy tails. Also, the techniques are extended to the cooperative SS scenario where multiple CR nodes record observations using multiple antennas and perform decentralized detection. In this thesis, we study all the issues listed above by considering both single and multiple CR nodes, and evaluating their performance in terms of(a)probability of detection error,(b) sensing-throughput trade off, and(c)probability of rejecting the null-hypothesis. We propose various SS strategies, compare their performance against existing techniques, and discuss their relative advantages and performance tradeoffs. The main contributions of this thesis are as follows: The question of whether to use pilot-based narrowband sensing or wideband sensing is answered using a novel, analytically tractable metric proposed in this thesis called the error exponent with a confidence level. Under a Bayesian framework, obtaining closed form expressions for the optimal detection threshold is difficult. Near-optimal detection thresholds are obtained for most of the commonly encountered fading models. Foran FH primary, using the Fast Fourier Transform (FFT) Averaging Ratio(FAR) algorithm, the sensing-through put trade off are derived in closed form. A GoFT technique based on the statistics of the number of zero-crossings in the observations is proposed, which is robust to uncertainties in the noise statistics, and outperforms existing GoFT-based SS techniques. A multi-dimensional GoFT based on stochastic distances is studied, which pro¬vides better performance compared to some of the existing techniques. A special case, i.e., a test based on the Kullback-Leibler distance is shown to be robust to some uncertainties in the noise process. All of the theoretical results are validated using Monte Carlo simulations. In the case of FH-SS, an implementation of SS using the FAR algorithm on a commercially off-the ¬shelf platform is presented, and the performance recorded using the hardware is shown to corroborate well with the theoretical and simulation-based results. The results in this thesis thus provide a bouquet of SS algorithms that could be useful under different CRSS scenarios.

L'objecte d'estudi d'aquesta tesi es centra en la política europea de l'espectre radioelèctric i presta especial atenció a l'harmonització del dividend digital al Regne Unit i Espanya. La metodologia es basa en una revisió bibliogràfica i hemerogràfica completada amb un conjunt d'entrevistes amb representants de diferents organismes de regulació del Regne Unit i Espanya, i de la mateixa Comissió Europea. En la primera part de la tesi es realitza una aproximació conceptual, des d'una vessant tècnica i jurídica, a la xarxa radioelèctrica i al dividend digital, espai alliberat una vegada completada la transició a la TDT. Seguidament, s'aborda la naturalesa, àmbits de regulació de la xarxa radioelèctrica, actors, models i evolució de les formes de gestió. El tercer capítol es centra en la Unió Europea com actor de la política de l'espectre radioelèctric des de mitjans de la dècada dels 80 fins a l'actualitat. En la darrera part de la tesi es descriuen i analitzen les actuacions de la UE destinades a harmonitzar el dividend digital fent especial referència a les conseqüències d'aquesta harmonització sobre les estructures nacionals i la planificació de la TDT en els dos països estudiats, el Regne Unit i Espanya. / El objeto de estudio de esta tesis se centra en la política europea del espectro radioeléctrico y presta una especial atención a la armonización del dividendo digital en el Reino Unido y España. La metodología está basada en una revisión bibliográfica y hemerográfica completada con un conjunto de entrevistas con representantes de diferentes organismos de regulación del Reino Unido y España, y de la misma Comisión Europea. En la primera parte de la tesis se realiza una aproximación conceptual, desde una vertiente técnica y jurídica, a la red radioeléctrica y al dividendo digital, espacio liberado una vez se ha completado la transición a la TDT. Seguidamente, se aborda la naturaleza y ámbitos de la regulación de la red radioeléctrica, sus actores, modelos y evolución de sus formas de gestión. El tercer capítulo se centra en la Unión Europea como actor de la política del espectro radioeléctrico desde mediados de la década de los 80 hasta la actualidad. En la última parte de la tesis se describen y analizan las actuaciones de la UE destinadas a armonizar el dividendo digital y se atiende especialmente a las consecuencias que esta armonización tiene sobre las estructuras nacionales y la planificación de la TDT en los dos países estudiados, el Reino Unido y España. / The object of study of this thesis focuses on the European radio spectrum policy in particular the harmonization of the digital dividend in the United Kingdom and Spain. The methodology is based on a multidisciplinary bibliographic review completed with an in-depth interviews with policy-makers from the national regulatory authorities and the European Commission. The first chapter of the dissertation consists of a conceptual approach of radio spectrum network and the digital dividend, the amount space released once the switch-over is completed. Afterwards, it deals with the nature of spectrum regulation, its actors, models and evolution of spectrum management. Its third chapter focuses on the European Union as a spectrum policy actor from the 80's onwards. Finally, this thesis analyses the EU actions oriented to the harmonisation of the digital dividend, and pays special attention to its consequences on national structures and DTT plans of the United Kingdom and Spain.

Made available in DSpace on 2016-03-15T19:35:52Z (GMT). No. of bitstreams: 1 DENIS PAVEL CABEZAS HUAMAN.pdf: 1718725 bytes, checksum: b98f52c6b4dac9b37a33cc5bc62d871e (MD5) Previous issue date: 2015-03-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The project aims to study the disturbances (responses) of the low solar atmosphere caused by solar flares, using Hα, 30 THz (10 μm), UV/EUV, soft and hard X-rays observations, and a wide range of radio waves emissions (microwaves, millimeter, sub-millimeter). This set of multispectral data enabled us to (i) examine in detail various aspects of the phenomena, (ii) determine the origin of the radio emission during the gradual phase, and therefore (iii) understand the mechanism of the particles acceleration. The data we used for the completion of this study are based on Hα and 30 THz (10 μm) observations, made by the high cadence flare imaging system installed at OSM4 and CASLEO5 observatories, additionally data from HASTA (H-Alpha Solar Telescope for Argentina) telescope installed at OAFA6 observatory. In the sub-millimeter and millimeter domain at 212, 405 GHz and 45, 90 GHz, were from SST (Solar Sub-millimeter Telescope) and from POEMAS (POlarization Emission of Millimeter Activity at the Sun) solar radio telescopes, respectively. Complementary radio observations in the microwave range (0.2-15 GHz) from RSTN (Radio Solar Telescope Network) were considered. In addition, solar observations obtained by RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager), Fermi and GOES (Geostationary Operational Environmental Satellite) satellites in X-ray channels, and from AIA (Atmospheric Imaging Assembly) and HMI (Helioseismic and Magnetic Imager) instruments, onboard the SDO (Solar Dynamics Observatory) satellite, respectively. / O trabalho tem como objetivo estudar as perturbações da baixa atmosfera solar produzidas pelas explosões solares, usando observações em Hα, 30 THz (10 μm), UV/EUV, raios X e uma ampla faixa de emissões em ondas de rádio (microondas, milimétrica, submilimétrica); com o propósito de determinar a natureza dos processos físicos envolvidos. Este conjunto de dados multiespectrais nos permitiu (i) analisar os diferentes aspectos das explosões tanto na fase impulsiva como gradual, (ii) determinar a origem da emissão em rádio durante a fase gradual, e consequentemente (iii) entender melhor os mecanismos de aceleração das partículas. Os dados em Hα e 30 THz foram fornecidos pelo sistema de aquisição de dados com alta resolução temporal, instalado nos observatórios OSM1 e CASLEO2, adicionalmente dados do telescópio HASTA (H-Alpha Solar Telescope for Argentina) instalado no observatório OAFA3. Enquanto as observações em rádio, os dados foram do rádio polarímetro POEMAS (POlarization Emission of Millimeter Activity at the Sun) nas frequências de 45 e 90 GHz, do telescópio SST (Sub-millimeter Solar Telescope) nas frequências 212 e 405 GHz, ambos instalados no CASLEO. Dados na faixa de microondas (0,2-15 GHz) obtidos pela rede RSTN (Radio Solar Telescope Network). Além disso, foram considerados observações do Sol obtidas pelos satélites RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager), Fermi e GOES (Geostationary Operational Environmental Satellite) para raios X, e dos instrumentos AIA (Atmospheric Imaging Assembly), HMI (Helioseismic and Magnetic Imager), a bordo do satélite SDO (Solar Dynamics Observatory), respectivamente.