Cognitive radios require spectral occupancy information in a given location, to avoid any interference with the existing licensed users. This is achieved by spectrum sensing. Existing narrowband, serial spectrum sensors are spectrally inefficient and power hungry. Wideband spectrum sensing increases the number of probable fre-quency candidates for cognitive radio. Wideband RF systems cannot use analog to digital converters (ADCs) for spectrum sensing without increasing the sampling rate and power consumption. The use of ADCs is limited because of the dynamic range of the signals that need to be sampled and the frequency of operation. In this work, we have presented a CMOS based area efficient, dedicated and scalable wideband parallel/serial spectrum sensor for cognitive radio. The key contributions of the thesis are: 1. An injection locked oscillator cascade (ILOC) for parallel LO synthesis. An area-efficient, wideband RF frequency synthesizer, which simultaneously gen-erates multiple local oscillator (LO) signals, is designed. It is suitable for parallel wideband RF spectrum sensing in cognitive radios. The frequency synthesizer consists of an injection locked oscillator cascade where all the LO signals are derived from a single reference oscillator. The ILOC is implemented in a 130-nm technology with an active area of 0.017 mm2. It generates 4 uni-formly spaced LO carrier frequencies from 500 MHz to 2 GHz. 2. A wideband, parallel RF spectrum sensor for cognitive radios has been de-signed. This spectrum sensor is designed to detect RF occupancy from 250 MHz to 5.25 GHz by using an array of CMOS receivers with envelope detec-tors. A parallel LO synthesizer is implemented as an ILOC. The simulated sensitivity is around -25 dBm for 250 MHz wide bandwidth. 3. A mitigation technique for harmonic downconversion in wideband spectrum sensors. The downconversion of radio frequency (RF) components around the harmonics of the local oscillator (LO), and its impact on the accuracy of white space detection using integrated spectrum sensors, is (are) studied. We propose an algorithm to mitigate the impact of harmonic Down conversion by utilizing multiple parallel downconverters in the system architecture. The proposed algorithm is validated on a test-board using commercially avail-able integrated circuits (IC) and a test-chip implemented in a 130-nm CMOS technology. The measured data shows that the impact of the harmonic down-conversion is closely related to the LO characteristics, and that much of it can be mitigated by the proposed technique. 4. A wideband spectrum sensor for narrowband energy detection. A wideband spectrum sensing system for cognitive radio is designed and implemented in a 130-nm RF mixed-mode CMOS technology. The system employs an I-Q downconverter, a pair of complex filters and a pair of envelope detectors for energy detection. The spectrum sensor works from 250 MHz to 3.25 GHz. The design makes use of the band pass nature of the complex filter to achieve two objectives : i) Separation of upper sideband (USB) and lower sideband (LSB) around the local oscillator (LO) signal and ii) Resolution of smaller bands within a large detection bandwidth. The measured sensitivity is close to -45 dBm for a single tone test over a bandwidth of 40 MHz. The measured Image reject ratio (IRR) is close to 30 dB. The overall sensing bandwidth is 3.5 GHz and the overall wideband detection bandwidth is 250 MHz which is partitioned into 40 MHz narrowband chunks with 8 such overlapping chunks.

Le foie est le principal organe impliqué dans la biotransformation des xénobiotiques. Les cytochromes P450 (CYP) en sont des enzymes dés. Parmi elles, leCYP4A est impliqué dans rhydroxylatlon des acides gras et la biotransformation de médicaments, tels que le bézafibrate (BE2A), un hypolipémiant utilisé enthérapeutique humaine. Cette molécule a été montrée hépatocarcinogène chez les rongeurs mais cet effet n'a pas été rapporté chez l'Homme. H est doncimportant de connaître les mécanismes d'action impliqués dans les effets du BEZA chez l'Homme. Dans une première étude, nous avons étudié l'expression duCYP4A au niveau ARNm et apoprotéine ainsi qu'au niveau de son activité dans des cultures primaires d'népatocytes de rat et d'Homme traitées ou non par duBEZA et de la N-acétylcystéine, molécule précurseur du glutathion. Nous avons mis en évidence d'importantes différences Interespèces et l'influence del'environnement redox des cellules en termes de réponse aux Inducteurs. L'implication des récepteurs nucléaires PPARa, PXR et CAR et des CYP4A/3A/2B aensuite été évaluée pour expliquer les différences inter-espèces observées. D'autre part, nous avons montré pour la première fois que le BEZA diminuel'expression de l'ARNm de OATP2 chez le rat et la biodisponibilité des statines en utilisant un système de biochromatographie original. Enfin, nous avonsmontré que le BEZA, en fonction de l'environnement redox de la cellule, régule des protéines impliquées dans le métabolisme des acides gras et lipides, ainsique des biomarqueurs d'hépatocarcinogenèse chez l'Homme, ce qui pose réellement la question du bien-fondé de l'utilisation de cette molécule enthérapeutique / The liver is the main organ involved in biotransformation of xenobkrtics invotving the cytochrome P450 (CYP). Among thèse enzymes, the CYP4A participate in the <o-hydroxylat!on of fatty acids and the met a bolis m of drugs such as be zafibrate (Beza), a lipld-lo wering molécule used In human therapy. It has been shown hepatocarcinogen In rodent; but no effect was reported in humans. It is thus important to understand thé mechanisms of action of Beza in humans. In a first study, we Investigated the expression of CYP4A at the mRNA, apoprotein and activity leveis In primary cultures of rat and human hepatocytes treated or not wlth Beza and/or N- acetylcysteine, a glutathtone precursor. We hâve highlighted Important différences between spedes and the Influence of ce» redox envlronment in terms of response to inducers. The involvement of nudear receptors PPARa, PXR and CAR and of CYP4A/3A/2B was then evaluated to explain the différences observed between species. On the other hand, we showed for the flrst time that Beza decreases the expression of rat OATP2 mRNA and the bioavailability of statins by uslng an original biochromatography System. Flnally, we showed that Beza, dependlng on the cellular redox envlronment modulâtes proteins involved In the metabolism of fatty acids and liplds, and also some biomarkers of hepatocarcinogenesis In humans, which raises the reai question a bout the appropr iateness of using t h is drug in human therapy.

Today, GNSS measurements play an important role in the surveying industry, and their use is ever increasing. Many different GNSS receivers and antenna manufacturers are on the market with new ones appearing. The purpose of this study is to investigate the level of measurement uncertainty of three different GNSS receivers: Leica GS15, Sokkia GCX2 and Satlab SL300. The method in this study is based mainly on the method proposed by HMK - Geodatakvalitet 2015 (Manual in measurement and map issues – Geographic data quality 2015 [author’s translation]) by Swedish Lantmäteriet for "Evaluation of measurement uncertainty in Network RTK [author’s translation]”. Some corrections and additions are made to this method but the basis of the method is retrieved from there. Formulas are used to calculate radial deviation and limit requirements for these. Even standard deviations and radial mean deviations as well as tolerances for these are calculated. The field measurements are made on two RIX 95-points. This is done repeatedly to get up to 20 measurements. The GNSS receivers are mounted on a tripod with a tribrach that is centered over the known points. The main finding from this study is that all investigated receivers, apart from four overriding values ​​for the Leica GS15, perform better than specified by their manufacturers. However, Sokkia GCX2 and Satlab SL300 are approved with uncertainties within the calculated tolerances. The Leica GS15 instrument is very close to meeting the demands but does not reach all the way. A committed error during the performed measurements with the Satlab SL300 makes its evaluation based on 19 instead of 20 measurements. Still, calculations are performed on the collected data that resulted in low measurement uncertainties well below the manufacturer's specified uncertainty. The study was conducted during five weeks in May and June 2017.

The intellectual property concept of 'communication to the public of the broadcast works by radio or television receivers' in Article 23 of the Czech copyright act is a current issue especially in a relation to the exception to this right in favour of health establishments that has been called in a question in front of both Czech courts and CJEU. The most important criteria of communication to the public -- laid down by CJEU -- suggest that the concept should be interpreted broadly, covering all transmissions, regardless of the means used and the nature of the place for the communication. A public refers to an indeterminate but fairly high number of people who constitute so called new public. In order to fall within the scope of a lawful exception the criteria of the so called 'three-step test' must be met as well as the formal criteria stated in the abovementioned Article. The most recent cases discussed in this work dealt with the transmission of the protected works by means of television sets located in the bedrooms of the guests of spa establishments. Although it was held by CJEU that this exception does not comply with EU law, it is still part of the Czech law and Czech courts must cope with it.

For ultra-high speed communication systems at high center frequencies above 100 GHz, we propose a disruptive change in system architecture to address major issues regarding amplifier chains with a large number of amplifier stages. They cause a high noise figure and high power consumption when operating close to the frequency limits of the underlying semiconductor technologies. Instead of scaling a classic homodyne transceiver system, we employ repeated amplification in single-stage amplifiers through positive feedback as well as synthesizer-free self-mixing demodulation at the receiver to simplify the system architecture notably. Since the amplitude and phase information for the emerging oscillation is defined by the input signal and the oscillator is only turned on for a very short time, it can be left unstabilized and thus come without a PLL. As soon as gain is no longer the most prominent issue, relaxed requirements for all the other major components allow reconsidering their implementation concepts to achieve further improvements compared to classic systems. This paper provides the first comprehensive overview of all major design aspects that need to be addressed upon realizing a SPARS-based transceiver. At system level, we show how to achieve high data rates and a noise performance comparable to classic systems, backed by scaled demonstrator experiments. Regarding the transmitter, design considerations for efficient quadrature modulation are discussed. For the frontend components that replace PA and LNA amplifier chains, implementation techniques for regenerative sampling circuits based on super-regenerative oscillators are presented. Finally, an analog-to-digital converter with outstanding performance and complete interfaces both to the analog baseband as well as to the digital side completes the set of building blocks for efficient ultra-high speed communication.

[ES] Las comunicaciones ópticas inalámbricas (OWC) constituyen una tecnología muy prometedora para el desarrollo de futuras comunicaciones inalámbricas. De hecho, ha despertado un interés creciente entre los investigadores y varias empresas de todo el mundo trabajan actualmente en el desarrollo de redes inalámbricas de muy alta velocidad. Las comunidades científica e industrial consideran la OWC como una tecnología complementaria en sus diversas formas: comunicaciones ópticas en el espacio libre (FSO), comunicaciones de luz visible (VLC) o fidelidad de la luz (Li-Fi). El espectro óptico ha sido considerado durante muchos años como una gran oportunidad para las comunicaciones inalámbricas, especialmente debido a la saturación del espectro de radiofrecuencia (RF). Esta disertación trata del uso de fuentes de banda ancha en sistemas de transmisión de luz visible (VLC), así como en sistemas de transmisión en el espectro infrarrojo por fibra óptica. En el trabajo de investigación realizado se pueden distinguir tres partes: En la primera parte, se considera el estudio y la simulación de componentes de Diodos Emisores de Luz (LED) con el software WIEN2k centrándose en las propiedades ópticas y eléctricas de los elementos II-VI. La segunda parte trata del diseño, la implementación y las pruebas de diferentes prototipos de comunicación VLC para la transmisión analógica y digital en modo simplex y semidúplex. Hemos demostrado un sistema OWC empleando una fuente de banda ancha (LED) para la transmisión no sólo de datos, sino también para la transmisión inalámbrica de energía. Además, se aborda el problema de la sincronización y la detección del nivel "1" o "0" de un bit en los sistemas de comunicación inalámbrica óptica implementados que surge como consecuencia de la atenuación de la luz a lo largo de la distancia y al problema de la pérdida de línea de visión (NLOS) entre el emisor y el receptor. Para hacer frente a este problema, se ha proporcionado un protocolo de comunicación que garantiza la transmisión fiable de datos digitales con un algoritmo de detección de nivel de bits adaptativo y se ha demostrado su eficacia mediante la transmisión de textos e imágenes. Además, esta tesis aporta una solución para la implementación de transmisores multiplexados en redes con división de longitud de onda (WDM) para formatos de modulación con multiplexación por división de frecuencia ortogonal (OFDM) basados en el uso de fuentes de banda ancha en el espectro infrarrojo para redes de fibra bidireccionales centralizadas. A pesar de las limitaciones impuestas por la dispersión cromática en el uso de este tipo de fuentes ópticas, la inclusión de ciertas estructuras antes de la detección permite la transmisión de señales OFDM en enlaces ópticos. En este trabajo se ha demostrado experimentalmente la reutilización de portadoras, la asignación dinámica de ancho de banda y la transmisión de señales OFDM multibanda mediante el uso de fuentes ópticas de banda ancha en redes WDM. Los principales resultados obtenidos en cada parte de esta tesis doctoral muestran los procedimientos de estudio, la eficacia de las soluciones propuestas y las limitaciones encontradas. / [CA] Les comunicacions òptiques sense fils (OWC) constitueixen una tecnologia molt prometedora per al desenvolupament de futures comunicacions sense fils. De fet, ha despertat un interés creixent entre els investigadors i diverses empreses de tot el món treballen actualment en el desenvolupament de xarxes sense fils de molt alta velocitat. Les comunitats científica i industrial consideren la OWC com una tecnologia complementària en les seues diverses formes: comunicacions òptiques en l'espai lliure (FSO), comunicacions de llum visible (VLC) o fidelitat de la llum (Li-Fi). L'espectre òptic ha sigut considerat durant molts anys com una gran oportunitat per a les comunicacions sense fils, especialment a causa de la saturació de l'espectre de radiofreqüència (RF). Aquesta dissertació tracta de l'ús de fonts de banda ampla en sistemes de transmissió de llum visible (VLC), així com en sistemes de transmissió en l'espectre infraroig per fibra òptica. En el treball de recerca realitzat es poden distingir tres parts: ¿ En la primera part, es considera l'estudi i la simulació de components de Díodes Emissors de Llum (LED) amb el software WIEN2k centrant-se en les propietats òptiques i elèctriques dels elements II-VI. ¿ La segona part tracta del disseny, la implementació i les proves de diferents prototips de comunicació VLC per a la transmissió analògica i digital de manera simplex i semidúplex. Hem demostrat un sistema OWC emprant una font de banda ampla (LED) per a la transmissió no sols de dades, sinó també per a la transmissió sense fil d'energia. A més, s'aborda el problema de la sincronització i la detecció del nivell "1" o "0" d'un bit en els sistemes de comunicació sense fil òptica implementats, que sorgeix a conseqüència de l'atenuació de la llum al llarg de la distància i al problema de la pèrdua de línia de visió (NLOS) entre l'emissor i el receptor. Per a fer front a aquest problema, s'ha proporcionat un protocol de comunicació que garanteix la transmissió fiable de dades digitals amb un algorisme de detecció de nivell de bits adaptatiu i s'ha demostrat la seua eficàcia mitjançant la transmissió de textos i imatges. ¿ A més, aquesta tesi aporta una solució per a la implementació de transmissors multiplexats en xarxes amb divisió de longitud d'ona (WDM) per a formats de modulació amb multiplexació per divisió de freqüència ortogonal (OFDM) basats en l'ús de fonts de banda ampla en l'espectre infraroig per a xarxes de fibra bidireccionals centralitzades. Malgrat les limitacions imposades per la dispersió cromàtica en l'ús d'aquest tipus de fonts òptiques, la inclusió d'unes certes estructures abans de la detecció permet la transmissió de senyals OFDM en enllaços òptics. En aquest treball s'ha demostrat experimentalment la reutilització de portadores, l'assignació dinàmica d'amplada de banda i la transmissió de senyals OFDM multibanda mitjançant l'ús de fonts òptiques de banda ampla en xarxes WDM. Els principals resultats obtinguts en cada part d'aquesta tesi doctoral mostren els procediments d'estudi, l'eficàcia de les solucions proposades i les limitacions trobades. / [EN] Optical wireless communication (OWC) is a very promising technology for future wireless communications developments. It has attracted increasing interest from researchers and several companies around the world are currently working on the development of very high-speed wireless networks. The scientific and industrial communities believe that OWC will be a complementary technology in its various forms: Free Space Optical communications (FSO), Visible Light Communications (VLC), Light Fidelity (Li-Fi). In fact, the optical spectrum has been considered for many years as a great opportunity for wireless communications especially due to the saturation of the radio frequency (RF) spectrum. This dissertation deals with the use of broadband sources in visible light transmission systems (VLC) as well as fiber optic systems. To carry out the research, three parts can be distinguished: In the first part, we consider the study and simulation of Light Emitting Diode (LED) components with the WIEN2k software by focusing on the optical and electrical properties of elements II-VI. The second part deals with the design, implementation and testing of different VLC communication prototypes for analog and digital transmission in simplex and half-duplex mode. We have demonstrated that an OWC system using a broadband source (i.e. an LED) can be used not only for data transmission, but also for wireless power transmission. Moreover, the synchronization problem and the detection of level "1" or "0" of a bit often arise in the optical wireless communication systems. This is a result of the attenuation nature of the light over the distance and the problem of Non Line-Of-Sight (NLOS) between the emitter and the receiver. To deal with this problem, a communication protocol ensuring reliable digital data transmission with an adaptive bit level detection algorithm has been provided and its effectiveness has been demonstrated by the transmission of texts and images. In addition, this thesis provides a solution for the implementation of wavelength division multiplexed - orthogonal frequency division multiplexed (WDM-OFDM) transmitters based on the use of broadband sources in the infrared spectrum for centralized bidirectional fiber networks. Despite the chromatic dispersion that avoids the use of this type of optical sources, the inclusion of certain structures before detection allows the transmission of OFDM signals in optical links. Carrier reuse, dynamic bandwidth allocation and multiband OFDM signals transmission will be experimentally demonstrated by using optical broadband sources in WDM networks. The main results obtained during this thesis work demonstrate the study procedures, for each part, the effectiveness of the proposed solutions as well as the constraints encountered. / Sekkiou, I. (2021). Design of communication systems based on broadband sources for fiber and free space optical links [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/172542

Long Range (LoRa) has become a key enabler technology for low power wide area networks. However, due to its ALOHA-based medium access scheme, LoRa has to cope with collisions that limit the capacity and network scalability. Collisions between randomly overlapped signals modulated with different spreading factors (SFs) result in inter-SF interference, which increases the packet loss likelihood when signal-to-interference ratio (SIR) is low. This issue cannot be resolved by channel coding since the probability of error distance is not concentrated around the adjacent symbol. In this paper, we analytically model this interference, and propose an interference cancellation method based on the idea of segmentation of the received signal. This scheme has three steps. First, the SF of the interference signal is identified, then the equivalent data symbol and complex amplitude of the interference are estimated. Finally, the estimated interference signal is subtracted from the received signal before demodulation. Unlike conventional serial interference cancellation (SIC), this scheme can directly estimate and reconstruct the non-aligned inter-SF interference without synchronization. Simulation results show that the proposed method can significantly reduce the symbol error rate (SER) under low SIR compared with the conventional demodulation. Moreover, it also shows high robustness to fractional sample timing offset (STO) and carrier frequency offset (CFO) of interference. The presented results clearly show the effectiveness of the proposed method in terms of the SER performance.

In this paper, we analyze the achievable secrecy rates in the two-hop wiretap channel with four nodes, where the transmitter and the receiver have multiple antennas while the relay and the eavesdropper have only a single antenna each. The relay is operating in amplify-and-forward mode and all the channels between the nodes are known perfectly by the transmitter. We discuss different transmission and protection schemes like artificial noise (AN). Furthermore, we introduce interference neutralization (IN) as a new protection scheme. We compare the different schemes regarding the high-SNR slope and the high-SNR power offset and illustrate the performance by simulation results. It is shown analytically as well as by numerical simulations that the high SNR performance of the proposed IN scheme is better than the one of AN.

1-bit analog-to-digital conversion is very attractive for low-complexity communications receivers. A major drawback is, however, the small spectral efficiency when sampling at symbol rate. This can be improved through oversampling by exploiting the signal distortion caused by the transmission channel. This paper analyzes the achievable data rate of band-limited communications channels that are subject to additive noise and inter-symbol-interference with 1-bit quantization and oversampling at the receiver. It is shown that not only the channel noise but also the inter-symbol-interference can be exploited to benefit from oversampling.

With the explosive development of wireless communication systems the specifications of the supporting hardware platforms have become more and more demanding. According to the long term goals of the industry, future communications systems should integrate a wide variety of standards. This leads to the idea of software defined radio, implemented on fully reconfigurable hardware.Among other reconfigurable hardware blocks, suitable for the software radio concept, an outstanding importance belongs to the reconfigurable filters that are responsible for the selectivity of the system. The problematic of filtering is strictly connected to the architecture chosen for a multi-mode receiver realization. According to the chosen architecture, the filters can exhibit low pass or band pass frequency responses.The idea of reconfigurable frequency parameters has been introduced since the beginning of modern filtering applications due to the required precision of the frequency response. However, the reconfiguration of the parameters was usually done in a limited range around ideal values. The purpose of the presented research is to transform the classical filter structures with simple self-correction into fully reconfigurable filters over a wide range of frequencies. The ideal variation of the frequency parameters is continuous and consequently difficult to implement in real circuits. Therefore, it is usually sufficient to use a discrete programming template with reasonably small steps.There are several methods to implement variable frequency parameters. The most often used programming templates employ resistor and capacitor arrays, switched according to a given code. The low pass filter implementation proposed in this work uses a special switching template, optimized for a quasi-linear frequency variation over logarithmic axes. The template also includes the possibility to compensate errors caused by component tolerances and temperature. Another important topic concerns the implementation of programmable band pass filters, suitable for IF sampling receivers. The discussion is centered on the feasibility and the flexibility of different band pass filter architectures. Due to the high frequency requirements, the emphasis lays on filters that employ transconductance amplifiers and capacitors. / Die rasch fortschreitende Entwicklung drahtloser Kommunikationssysteme führt zu immer anspruchsvolleren Spezifikationen der diese Systeme unterstützenden Hardwareplattformen. Zukünftige Kommunikationssysteme sollen übereinstimmend mit den längerfristigen Zielen der Industrie verschiedene Standards integrieren. Dies führt zu der Idee von vollständig rekonfigurierbarer Hardware, welche mittels Software gesteuert wird.Inmitten anderer rekonfigurierbarer Hardwareblöcke, die für das Software Radio Konzept geeignet sind, besitzen die steuerbaren Filter, welche wesentlichen Einfluss auf die Selektivität des Systems haben, eine enorme Bedeutung. Die Filterproblematik ist eng mit der gewählten Architektur der standardübergreifenden Empfängerrealisierung verknüpft. Die Filter können entsprechend der ausgesuchten Architektur Tiefpass- oder Bandpasscharakter annehmen.Die Idee rekonfigurierbarer Frequenzparameter wurde bereits mit Beginn moderner Filteranwendungen auf Grund geforderter Frequenzganggenauigkeit umgesetzt. Jedoch wurde die Parameterrekonfiguration üblicherweise nur in einem begrenzten Bereich um die Idealwerte herum vorgenommen. Das Ziel der vorgestellten Forschungsarbeit ist es, diese klassischen Filterstrukturen mit einfacher Selbstkorrektur in über große Frequenzbereiche voll rekonfigurierbare Filter zu transformieren. Idealerweise werden die Frequenzparameter kontinuierlich variiert weswegen sich die Implementierung in reellen Schaltkreisen als schwierig erweist. Deshalb ist es üblicherweise ausreichend, ein diskretes Steuerschema mit kleinen Schrittweiten zu verwenden.Es gibt verschiedene Methoden, variable Frequenzparameter zu implementieren. Die meisten Schemata verwenden Widerstands- und Kondensatorfelder, die entsprechend eines Kodes geschaltet werden. Die in dieser Arbeit vorgestellte Implementierung eines Tiefpassfilters nutzt ein spezielles Umschaltschema, welches für die quasi-lineare Frequenzvariation bei Darstellung über logarithmischen Axen optimiert wurde. Es beinhaltet weiterhin die Möglichkeit, Fehler zu kompensieren, die durch Bauelementtoleranzen und Temperaturschwankungen hervorgerufen werden.Ein weiteres interessantes Thema betrifft die Implementierung steuerbarer Bandpassfilter, die für Empfänger mit Zwischenfrequenzabtastung geeignet sind. Die Betrachtung beschränkt sich hierbei auf die Durchführbarkeit und Flexibilität verschiedener Bandpassfilterarchitekturen. Auf Grund hoher Frequenzanforderungen liegt der Schwerpunkt auf Filtern, die auf Transkonduktanzverstärkern und Kondensatoren basieren.