73 research outputs found

    Empirical Evaluation of the Impact of Wind Turbines on DVB-T Reception Quality

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    [EN] This paper describes the results of two extensive measurement campaigns for evaluating the potential impact of scattered signals from wind turbines on terrestrial DTV reception quality in the UHF band. A detailed description of the different propagation channels encountered is provided. Furthermore, empirical threshold carrier-to-noise requirements for Quasi Error Free reception in the DVB-T system in the area of influence of a wind farm are presented, and the situations where a significant degradation can be found are identified and characterized.This work has been partially supported by the UPV/EHU GIC 07/110-IT-374-07, by the Basque Government under both the SAIOTEK program and the program for the training of the researcher staff (BFI08.230), by the Spanish Ministry of Science and Innovation under the project NG-RADIATE, TEC2009-14201, and by the Spanish Ministry of Industry, Tourism and Trade under the project ENGINES, TSI-020400-2010-188. ENGINES project is under the Celtic Initiative (Celtic Label CP7-005)

    A Measurement-based Multipath Channel Model for Signal Propagation in Presence of Wind Farms in the UHF Band

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    [EN] Scattering signals on wind turbines may lead to degradation problems on the communication systems provided in the UHF band, such as terrestrial television broadcasting, broadband wireless systems or public safety services. To date, despite the continuous requests from the International Telecommunication Union for studies on this field, no channel model has been developed to characterize signal propagation under these particular conditions. In response to this necessity, this paper presents a complete Tapped Delay Line (TDL) channel model to characterize multipath propagation in presence of a wind farm, including novel scattering modeling and Doppler spectra characterization. As proved later, this channel model, which is based on both theoretical development and empirical data obtained in the surroundings of a real wind farm, is adaptable to the particular features of any case under study: wind turbine dimensions, working frequency, and relative location of the wind farm, transmitter and receivers.This work was supported in part by the European Union FP7 (grant agreement n 296164), by the Spanish Ministry of Economy and Competitiveness (project TEC2012-32370), and by the Basque Government (SAIOTEK program)

    An Empirical Comparative Study of Prediction Methods for Estimating Multipath Due to Signal Scattering from Wind Turbines on Digital TV Services

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    [EN] Several authors have theoretically studied the effect of wind turbines on the propagation of electromagnetic waves in the UHF band. The International Telecommunication Union also proposes a simplified model to evaluate the impact caused to television reception by a wind turbine in the Recommendation ITU-R BT.805. This paper presents an empirical study of the above mentioned prediction methods for estimating signal scattering from wind turbines in the UHF band, comparing predicted values with empirical data obtained from a DTV measurement campaign carried out in Spain. As signal scattering is independent of the transmission standard or modulation, the results are applicable to any broadcasting and wireless communication signals in the UHF band that may be affected by the multipath interference caused by a wind farm.This work was supported in part by the Basque Government under both the SAIOTEK program and the program for the training of the researcher staff (BFI08.230)

    Empirical Doppler Characterization of Signals Scattered by Wind Turbines in the UHF Band under Near Field Condition

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    Time variability of the scattering signals from wind turbines may lead to degradation problems on the communication systems provided in the UHF band, especially under near field condition. In order to analyze the variability due to the rotation of the blades, this paper characterizes empirical Doppler spectra obtained from real samples of signals scattered by wind turbines with rotating blades under near field condition. A new Doppler spectrum model is proposed to fit the spectral characteristics of these signals, providing notable goodness of fit. Finally, the effect of this kind of time variability on the degradation of OFDM signals is studied

    Corrección del modelo de propagación en redes de televisión digital terrestre en entornos urbanos

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    This article presents an ideal propagation model for the design of Digital Terrestrial Television (DTT) networks in Bogotá City. Here was developed, evaluated and compared three propagation models commonly used for the design of this type of networks; these are the methods Stanford University Interim (SUI), Xia-Bertoni and Okumura-Hata. Those were chosen because they allow to calculate the propagation losses over the UHF band and the cartographic information required to estimate the losses by diffraction is not high precision. Here, we found two of the selected models are close to the actual model in a range of 10-15 dB. So, all the models were adjusted and corrected by MATLAB in order to obtain an accurate estimate of signal propagation losses. The models were evaluated with statistical criteria of significance such as correlation coefficient, mean square error, standard deviation and so on [1]. As a result, both Okumura-Hata and Xia-Bertoni models were found to fit easily into the real model, however, the error of the Xia-Bertoni model is smaller compared to the Okumura model.Este artículo presenta un modelo de propagación idóneo para el diseño de redes Televisión Digital Terrestre (TDT) en la ciudad de Bogotá. En el desarrollo se encuentra la evaluación y comparación de tres modelos de propagación comúnmente usados para el diseño de este tipo de redes; estos son los métodos Stanford University Interim (SUI), Xia-Bertoni y Okumura-Hata, escogidos porque permiten calcular las pérdidas de propagación sobre la banda UHF y la información cartográfica que requieren para estimar las pérdidas por difracción no es de alta precisión. Aquí se determina que dos de los modelos escogidos son cercanos al modelo real en un rango de 10 – 15 dB. Dado esto, se ajustaron y se efectuó una corrección, por medio de Matlab, a los todos los modelos con el fin de obtener una acertada estimación de pérdidas en la propagación de la señal. Los modelos fueron evaluados con criterios estadísticos de significancia como lo son el coeficiente de correlación, error medio cuadrado, desviación estándar etc. [1] Como resultado se determinó que tanto el modelo Okumura-Hata como el Xia-Bertoni se ajustaban fácilmente al modelo real, sin embargo, el error del modelo Xia Bertoni es menor en comparación con Okumura

    Modelo de canal para caracterizar la señal dispersada por un parque eólico en la banda UHF e influencia sobre la calidad de servicio de DVB-T

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    288 p. : il.[ES]La presencia de un parque eólico provoca una serie de efectos sobre las señales electromagnéticas que pueden dar lugar a una degradación de la calidad de los servicios de telecomunicaciones proporcionados en sus cercanías. En lo que respecta a la difusión de televisión, el efecto de un parque eólico en la difusión de televisión digital no había sido determinado hasta ahora.Por otra parte, la evaluación de la posible degradación de estos servicios se ha realizado tradicionalmente mediante modelos que caracterizan la señal dispersada por las aspas del aerogenerador. Estos modelos clásicos de dispersión no contemplan ni la contribución del mástil a la señal dispersada, ni la variabilidad temporal de la señal dispersada debida a la rotación de las palas, ni la influencia conjunta de un parque eólico compuesto por varias máquinas.En este contexto, se plantea el primero de los objetivos principales de esta tesis: la evaluación empírica de la degradación causada en la recepción de señales de televisión digital DVB-T debida a la presencia de un parque eólico. Del estudio realizado, basado en medidas de campo, se concluye que las condiciones de recepción más críticas se dan en la zona de backscattering, donde la propagación responde a las características de un canal multitrayecto discreto variante con el tiempo.El segundo objetivo principal de esta tesis se centra en la propuesta un nuevo modelo de canal para caracterizar la propagación multitrayecto típica en los alrededores de un parque eólico en esta banda. Este modelo de canal se adapta a las condiciones particulares de cada caso en estudio: posición relativa transmisor-turbina-receptor, dimensiones del aerogenerador, velocidad máxima de rotación de las aspas, características de los sistemas radiantes del transmisor y receptor, y frecuencia de trabajo.[EN]The presence of a wind farm causes several effects on the electromagnetic signals that may degrade the quality of the telecommunication services provided nearby. In regard to television broadcasting, these effects are notable for the analogue signal. However, a potential impact of a wind farm on digital television broadcasting had not yet been assessed. Apart from that, the evaluation of the potential degradation on these services has been traditionally carried out by means of scattering models that only account for the signal scattered by the blades of a wind turbine. These classic models do not consider neither the mast contribution to the scattered signal nor the time variability due to the blade rotation or the joint influence of a wind farm composed of several turbines. In this context, the first of the two main objectives of this thesis is the empirical evaluation of the degradation caused to the DVB‐T digital television signals reception due to the presence of a nearby wind farm. From this measurement‐based study, it can be concluded that it is in the backscattering region where the most critical reception conditions are encountered. In this zone, the propagation channel can be characterized by a discrete time‐varying multipath channel. Therefore, in order to determine future possible degradations on the services provided in the UHF band, the second main objective of this thesis focuses on proposing a new channel model to characterize the multipath propagation typical of the area surrounding a wind farm. This channel model is adaptable to the particular features of each case under study: relative position transmitter‐wind turbine‐receiver, wind turbine dimensions, maximum rotation rate, characteristics of the transmitter and receiver radiating systems, and working frequency. In this way, the results obtained in this research work give answer to the studies requested by the International Telecommunications Union since the first cases of impact were detected[EUS]Parke eolikoek hainbat efektu eragiten dute seinale elektromagnetikoetan eta, ondorioz, zenbait kasutan, inguruan eskaintzen diren telekomunikazio zerbitzuek kalitatearen degradazioa jasan dezakete. Telebistari dagokionez, efektu hauek nabarmenak dira seinale analogikoaren kasuan. Aitzitik, parke eolikoek telebista digitalean izan dezaketen eragina ez da oraindik zehaztu. Bestalde, oraindaino telebista zerbitzuek izandako inpaktuaren ebaluazioa sakabanatze-ereduen bidez egin da. Sakabanatze-eredu klasiko hauek palek sakabanatzen duten seinalea baino ez dute adierazten; eta horrenbestez, ez dute kontuan hartzen dorreak sakabanatzen duen seinalea, ez besoen errotazio mugimenduak eragindako denbora aldakortasuna, ezta hainbat aerosorgailuz osatutako parkearen eragin bateratua ere. Testuinguru honetan, ikerkuntza lan honen lehen helburu nagusia definitzen da: parke eoliko batek DVB-T sisteman eragin dezakeen harrera-degradazioaren ebaluazio enpirikoa egitea. Neurketetan oinarritutako analisi honetatik, harrerabaldintza zailenak backsckattering delako eremuan gertatzen direla ondorioztatzen da, non hedapenak Ibilbide anitzeko eredua jarraitzen duen. Eredu honen portaera denborarekin aldakorra izango da palen errotazio mugimenduaren ondorioz. Horrez gain, UHF bandan igorritako zerbitzuetan gerta daitezkeen degradazioak aurreikusi ahal izateko, tesiaren bigarren helburua zehazten da: parke eoliko baten inguruan sortutako hedapen tipikoa deskribatzen duen kanal eredu berria proposatzea. Kanal eredu hau aztergai dauden kasu guztien baldintza partikularretara moldatzen da, eta kontuan hartzen du, besteak beste: transmisore-turbina-hargailu arteko kokapen erlatiboa, aerosorgailuaren tamaina, palen errotazio gehienezko abiadura, transmisore eta hargailuaren antenen ezaugarriak, eta frekuentzia. Tesi honetan lortutako emaitzei esker, lehenengo kasuak antzeman zirenetik Telekomunikazioen Nazioarteko Batasunak proposatutako ikerketa eskariei erantzuna ematen zaie.Tesis financiada con beca del Programa de Formación de Personal Investigador del Departamento de Educación, Universidades e Investigación (BFI08.230) del Gobierno Vasco. Colaboración del Communications Research Centre (CRC) de Canadá a través del Dr. Yiyan Wu, Adivic Technology co., Abertis Telecom, Itelazpi y Eólicas de Euskadi (hoy Iberdrola Renovables

    Solutions for New Terrestrial Broadcasting Systems Offering Simultaneously Stationary and Mobile Services

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    221 p.[EN]Since the first broadcasted TV signal was transmitted in the early decades of the past century, the television broadcasting industry has experienced a series of dramatic changes. Most recently, following the evolution from analogue to digital systems, the digital dividend has become one of the main concerns of the broadcasting industry. In fact, there are many international spectrum authorities reclaiming part of the broadcasting spectrum to satisfy the growing demand of other services, such as broadband wireless services, arguing that the TV services are not very spectrum-efficient. Apart from that, it must be taken into account that, even if up to now the mobile broadcasting has not been considered a major requirement, this will probably change in the near future. In fact, it is expected that the global mobile data traffic will increase 11-fold between 2014 and 2018, and what is more, over two thirds of the data traffic will be video stream by the end of that period. Therefore, the capability to receive HD services anywhere with a mobile device is going to be a mandatory requirement for any new generation broadcasting system. The main objective of this work is to present several technical solutions that answer to these challenges. In particular, the main questions to be solved are the spectrum efficiency issue and the increasing user expectations of receiving high quality mobile services. In other words, the main objective is to provide technical solutions for an efficient and flexible usage of the terrestrial broadcasting spectrum for both stationary and mobile services. The first contributions of this scientific work are closely related to the study of the mobile broadcast reception. Firstly, a comprehensive mathematical analysis of the OFDM signal behaviour over time-varying channels is presented. In order to maximize the channel capacity in mobile environments, channel estimation and equalization are studied in depth. First, the most implemented equalization solutions in time-varying scenarios are analyzed, and then, based on these existing techniques, a new equalization algorithm is proposed for enhancing the receivers’ performance. An alternative solution for improving the efficiency under mobile channel conditions is treating the Inter Carrier Interference as another noise source. Specifically, after analyzing the ICI impact and the existing solutions for reducing the ICI penalty, a new approach based on the robustness of FEC codes is presented. This new approach employs one dimensional algorithms at the receiver and entrusts the ICI removing task to the robust forward error correction codes. Finally, another major contribution of this work is the presentation of the Layer Division Multiplexing (LDM) as a spectrum-efficient and flexible solution for offering stationary and mobile services simultaneously. The comprehensive theoretical study developed here verifies the improved spectrum efficiency, whereas the included practical validation confirms the feasibility of the system and presents it as a very promising multiplexing technique, which will surely be a strong candidate for the next generation broadcasting services.[ES]Desde el comienzo de la transmisión de las primeras señales de televisión a principios del siglo pasado, la radiodifusión digital ha evolucionado gracias a una serie de cambios relevantes. Recientemente, como consecuencia directa de la digitalización del servicio, el dividendo digital se ha convertido en uno de los caballos de batalla de la industria de la radiodifusión. De hecho, no son pocos los consorcios internacionales que abogan por asignar parte del espectro de radiodifusión a otros servicios como, por ejemplo, la telefonía móvil, argumentado la poca eficiencia espectral de la tecnología de radiodifusión actual. Asimismo, se debe tener en cuenta que a pesar de que los servicios móviles no se han considerado fundamentales en el pasado, esta tendencia probablemente variará en el futuro cercano. De hecho, se espera que el tráfico derivado de servicios móviles se multiplique por once entre los años 2014 y 2018; y lo que es más importante, se pronostica que dos tercios del tráfico móvil sea video streaming para finales de ese periodo. Por lo tanto, la posibilidad de ofrecer servicios de alta definición en dispositivos móviles es un requisito fundamental para los sistemas de radiodifusión de nueva generación. El principal objetivo de este trabajo es presentar soluciones técnicas que den respuesta a los retos planteados anteriormente. En particular, las principales cuestiones a resolver son la ineficiencia espectral y el incremento de usuarios que demandan mayor calidad en los contenidos para dispositivos móviles. En pocas palabras, el principal objetivo de este trabajo se basa en ofrecer una solución más eficiente y flexible para la transmisión simultánea de servicios fijos y móviles. La primera contribución relevante de este trabajo está relacionada con la recepción de la señal de televisión en movimiento. En primer lugar, se presenta un completo análisis matemático del comportamiento de la señal OFDM en canales variantes con el tiempo. A continuación, con la intención de maximizar la capacidad del canal, se estudian en profundidad los algoritmos de estimación y ecualización. Posteriormente, se analizan los algoritmos de ecualización más implementados, y por último, basándose en estas técnicas, se propone un nuevo algoritmo de ecualización para aumentar el rendimiento de los receptores en tales condiciones. Del mismo modo, se plantea un nuevo enfoque para mejorar la eficiencia de los servicios móviles basado en tratar la interferencia entre portadoras como una fuente de ruido. Concretamente, tras analizar el impacto del ICI en los receptores actuales, se sugiere delegar el trabajo de corrección de dichas distorsiones en códigos FEC muy robustos. Finalmente, la última contribución importante de este trabajo es la presentación de la tecnología LDM como una manera más eficiente y flexible para la transmisión simultánea de servicios fijos y móviles. El análisis teórico presentado confirma el incremento en la eficiencia espectral, mientras que el estudio práctico valida la posible implementación del sistema y presenta la tecnología LDM c

    Final Report DE-EE0005380: Assessment of Offshore Wind Farm Effects on Sea Surface, Subsurface and Airborne Electronic Systems

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    ON THE LOCATION-AWARE COOPERATIVE SPECTRUM SENSING IN URBAN ENVIRONMENT

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    Spectrum sensing is a key enabling technology for cognitive radio networks (CRNs). The main objective of spectrum sensing is to provide more spectrum access opportunities to cognitive radio users without interfering with the operations of the licensed network. Spectrum sensing decisions can lead to erroneous sensing with low performance due to fading, shadowing and other interferences caused by either terrain inconsistency or dense urban structure. In order to improve spectrum sensing decisions, in this paper a cooperative spectrum sensing scheme is proposed. The propagation conditions such as the variance and intensity of terrain and urban structure between two points with respect to signal propagation are taken into consideration. We have also derived the optimum fusion rule which accounts for location reliability of secondary users (SUs). The analytical results show that the proposed scheme slightly outperforms the conventional cooperative spectrum sensing approaches
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