Advanced constellation and demapper schemes for next generation digital terrestrial television broadcasting systems

206 p.Esta tesis presenta un nuevo tipo de constelaciones llamadas no uniformes. Estos esquemas presentan una eficacia de hasta 1,8 dB superior a las utilizadas en los últimos sistemas de comunicaciones de televisión digital terrestre y son extrapolables a cualquier otro sistema de comunicaciones (satélite, móvil, cable¿). Además, este trabajo contribuye al diseño de constelaciones con una nueva metodología que reduce el tiempo de optimización de días/horas (metodologías actuales) a horas/minutos con la misma eficiencia. Todas las constelaciones diseñadas se testean bajo una plataforma creada en esta tesis que simula el estándar de radiodifusión terrestre más avanzado hasta la fecha (ATSC 3.0) bajo condiciones reales de funcionamiento.Por otro lado, para disminuir la latencia de decodificación de estas constelaciones esta tesis propone dos técnicas de detección/demapeo. Una es para constelaciones no uniformes de dos dimensiones la cual disminuye hasta en un 99,7% la complejidad del demapeo sin empeorar el funcionamiento del sistema. La segunda técnica de detección se centra en las constelaciones no uniformes de una dimensión y presenta hasta un 87,5% de reducción de la complejidad del receptor sin pérdidas en el rendimiento.Por último, este trabajo expone un completo estado del arte sobre tipos de constelaciones, modelos de sistema, y diseño/demapeo de constelaciones. Este estudio es el primero realizado en este campo

Architecture and algorithms for the implementation of digital wireless receivers in FPGA and ASIC: ISDB-T and DVB-S2 cases

[EN] The first generation of Terrestrial Digital Television(DTV) has been in service for over a decade. In 2013, several countries have already completed the transition from Analog to Digital TV Broadcasting, most of which in Europe. In South America, after several studies and trials, Brazil adopted the Japanese standard with some innovations. Japan and Brazil started Digital Terrestrial Television Broadcasting (DTTB) services in December 2003 and December 2007 respectively, using Integrated Services Digital Broadcasting - Terrestrial (ISDB-T), also known as ARIB STD-B31. In June 2005 the Committee for the Information Technology Area (CATI) of Brazilian Ministry of Science and Technology and Innovation MCTI approved the incorporation of the IC-Brazil Program, in the National Program for Microelectronics (PNM) . The main goals of IC-Brazil are the formal qualification of IC designers, support to the creation of semiconductors companies focused on projects of ICs within Brazil, and the attraction of semiconductors companies focused on the design and development of ICs in Brazil. The work presented in this thesis originated from the unique momentum created by the combination of the birth of Digital Television in Brazil and the creation of the IC-Brazil Program by the Brazilian government. Without this combination it would not have been possible to make these kind of projects in Brazil. These projects have been a long and costly journey, albeit scientifically and technologically worthy, towards a Brazilian DTV state-of-the-art low complexity Integrated Circuit, with good economy scale perspectives, due to the fact that at the beginning of this project ISDB-T standard was not adopted by several countries like DVB-T. During the development of the ISDB-T receiver proposed in this thesis, it was realized that due to the continental dimensions of Brazil, the DTTB would not be enough to cover the entire country with open DTV signal, specially for the case of remote localizations far from the high urban density regions. Then, Eldorado Research Institute and Idea! Electronic Systems, foresaw that, in a near future, there would be an open distribution system for high definition DTV over satellite, in Brazil. Based on that, it was decided by Eldorado Research Institute, that would be necessary to create a new ASIC for broadcast satellite reception. At that time DVB-S2 standard was the strongest candidate for that, and this assumption still stands nowadays. Therefore, it was decided to apply to a new round of resources funding from the MCTI - that was granted - in order to start the new project. This thesis discusses in details the Architecture and Algorithms proposed for the implementation of a low complexity Intermediate Frequency(IF) ISDB-T Receiver on Application Specific Integrated Circuit (ASIC) CMOS. The Architecture proposed here is highly based on the COordinate Rotation Digital Computer (CORDIC) Algorithm, that is a simple and efficient algorithm suitable for VLSI implementations. The receiver copes with the impairments inherent to wireless channels transmission and the receiver crystals. The thesis also discusses the Methodology adopted and presents the implementation results. The receiver performance is presented and compared to those obtained by means of simulations. Furthermore, the thesis also presents the Architecture and Algorithms for a DVB-S2 receiver targeting its ASIC implementation. However, unlike the ISDB-T receiver, only preliminary ASIC implementation results are introduced. This was mainly done in order to have an early estimation of die area to prove that the project in ASIC is economically viable, as well as to verify possible bugs in early stage. As in the case of ISDB-T receiver, this receiver is highly based on CORDIC algorithm and it was prototyped in FPGA. The Methodology used for the second receiver is derived from that used for the ISDB-T receiver, with minor additions given the project characteristics.[ES] La primera generación de Televisión Digital Terrestre(DTV) ha estado en servicio por más de una década. En 2013, varios países completaron la transición de transmisión analógica a televisión digital, la mayoría de ellas en Europa. En América del Sur, después de varios estudios y ensayos, Brasil adoptó el estándar japonés con algunas innovaciones. Japón y Brasil comenzaron a prestar el servicio de Difusión de Televisión Digital Terrestre (DTTB) en diciembre de 2003 y diciembre de 2007 respectivamente, utilizando Radiodifusión Digital de Servicios Integrados Terrestres (ISDB-T), también conocida como ARIB STD-B31. En junio de 2005, el Comité del Área de Tecnología de la Información (CATI) del Ministerio de Ciencia, Tecnología e Innovación de Brasil - MCTI aprobó la incorporación del Programa CI-Brasil, en el Programa Nacional de Microelectrónica (PNM). Los principales objetivos de la CI-Brasil son la formación de diseñadores de CIs, apoyar la creación de empresas de semiconductores enfocadas en proyectos de circuitos integrados dentro de Brasil, y la atracción de empresas de semiconductores interesadas en el diseño y desarrollo de circuitos integrados. El trabajo presentado en esta tesis se originó en el impulso único creado por la combinación del nacimiento de la televisión digital en Brasil y la creación del Programa de CI-Brasil por el gobierno brasileño. Sin esta combinación no hubiera sido posible realizar este tipo de proyectos en Brasil. Estos proyectos han sido un trayecto largo y costoso, aunque meritorio desde el punto de vista científico y tecnológico, hacia un Circuito Integrado brasileño de punta y de baja complejidad para DTV, con buenas perspectivas de economía de escala debido al hecho que al inicio de este proyecto, el estándar ISDB-T no fue adoptado por varios países como DVB-T. Durante el desarrollo del receptor ISDB-T propuesto en esta tesis, se observó que debido a las dimensiones continentales de Brasil, la DTTB no sería suficiente para cubrir todo el país con la señal de televisión digital abierta, especialmente para el caso de localizaciones remotas, apartadas de las regiones de alta densidad urbana. En ese momento, el Instituto de Investigación Eldorado e Idea! Sistemas Electrónicos, previeron que en un futuro cercano habría un sistema de distribución abierto para DTV de alta definición por satélite en Brasil. Con base en eso, el Instituto de Investigación Eldorado decidió que sería necesario crear un nuevo ASIC para la recepción de radiodifusión por satélite, basada el estándar DVB-S2. En esta tesis se analiza en detalle la Arquitectura y algoritmos propuestos para la implementación de un receptor ISDB-T de baja complejidad y frecuencia intermedia (IF) en un Circuito Integrado de Aplicación Específica (ASIC) CMOS. La arquitectura aquí propuesta se basa fuertemente en el algoritmo Computadora Digital para Rotación de Coordenadas (CORDIC), el cual es un algoritmo simple, eficiente y adecuado para implementaciones VLSI. El receptor hace frente a las deficiencias inherentes a las transmisiones por canales inalámbricos y los cristales del receptor. La tesis también analiza la metodología adoptada y presenta los resultados de la implementación. Por otro lado, la tesis también presenta la arquitectura y los algoritmos para un receptor DVB-S2 dirigido a la implementación en ASIC. Sin embargo, a diferencia del receptor ISDB-T, se introducen sólo los resultados preliminares de implementación en ASIC. Esto se hizo principalmente con el fin de tener una estimación temprana del área del die para demostrar que el proyecto en ASIC es económicamente viable, así como para verificar posibles errores en etapa temprana. Como en el caso de receptor ISDB-T, este receptor se basa fuertemente en el algoritmo CORDIC y fue un prototipado en FPGA. La metodología utilizada para el segundo receptor se deriva de la utilizada para el re[CA] La primera generació de Televisió Digital Terrestre (TDT) ha estat en servici durant més d'una dècada. En 2013, diversos països ja van completar la transició de la radiodifusió de televisió analògica a la digital, i la majoria van ser a Europa. A Amèrica del Sud, després de diversos estudis i assajos, Brasil va adoptar l'estàndard japonés amb algunes innovacions. Japó i Brasil van començar els servicis de Radiodifusió de Televisió Terrestre Digital (DTTB) al desembre de 2003 i al desembre de 2007, respectivament, utilitzant la Radiodifusió Digital amb Servicis Integrats de (ISDB-T), coneguda com a ARIB STD-B31. Al juny de 2005, el Comité de l'Àrea de Tecnologia de la Informació (CATI) del Ministeri de Ciència i Tecnologia i Innovació del Brasil (MCTI) va aprovar la incorporació del programa CI Brasil al Programa Nacional de Microelectrònica (PNM). Els principals objectius de CI Brasil són la qualificació formal dels dissenyadors de circuits integrats, el suport a la creació d'empreses de semiconductors centrades en projectes de circuits integrats dins del Brasil i l'atracció d'empreses de semiconductors centrades en el disseny i desenvolupament de circuits integrats. El treball presentat en esta tesi es va originar en l'impuls únic creat per la combinació del naixement de la televisió digital al Brasil i la creació del programa Brasil CI pel govern brasiler. Sense esta combinació no hauria estat possible realitzar este tipus de projectes a Brasil. Estos projectes han suposat un viatge llarg i costós, tot i que digne científicament i tecnològica, cap a un circuit integrat punter de baixa complexitat per a la TDT brasilera, amb bones perspectives d'economia d'escala perquè a l'inici d'este projecte l'estàndard ISDB-T no va ser adoptat per diversos països, com el DVB-T. Durant el desenvolupament del receptor de ISDB-T proposat en esta tesi, va resultar que, a causa de les dimensions continentals de Brasil, la DTTB no seria suficient per cobrir tot el país amb el senyal de TDT oberta, especialment pel que fa a les localitzacions remotes allunyades de les regions d'alta densitat urbana.. En este moment, l'Institut de Recerca Eldorado i Idea! Sistemes Electrònics van preveure que, en un futur pròxim, no hi hauria a Brasil un sistema de distribució oberta de TDT d'alta definició a través de satèl¿lit. D'acord amb això, l'Institut de Recerca Eldorado va decidir que seria necessari crear un nou ASIC per a la recepció de radiodifusió per satèl¿lit. basat en l'estàndard DVB-S2. En esta tesi s'analitza en detall l'arquitectura i els algorismes proposats per l'execució d'un receptor ISDB-T de Freqüència Intermèdia (FI) de baixa complexitat sobre CMOS de Circuit Integrat d'Aplicacions Específiques (ASIC). L'arquitectura ací proposada es basa molt en l'algorisme de l'Ordinador Digital de Rotació de Coordenades (CORDIC), que és un algorisme simple i eficient adequat per implementacions VLSI. El receptor fa front a les deficiències inherents a la transmissió de canals sense fil i els cristalls del receptor. Esta tesi també analitza la metodologia adoptada i presenta els resultats de l'execució. Es presenta el rendiment del receptor i es compara amb els obtinguts per mitjà de simulacions. D'altra banda, esta tesi també presenta l'arquitectura i els algorismes d'un receptor de DVB-S2 de cara a la seua implementació en ASIC. No obstant això, a diferència del receptor ISDB-T, només s'introdueixen resultats preliminars d'implementació en ASIC. Això es va fer principalment amb la finalitat de tenir una estimació primerenca de la zona de dau per demostrar que el projecte en ASIC és econòmicament viable, així com per verificar possibles errors en l'etapa primerenca. Com en el cas del receptor ISDB-T, este receptor es basa molt en l'algorisme CORDIC i va ser un prototip de FPGA. La metodologia utilitzada per al segon receptor es deriva de la utilitzada per al receptor IRodrigues De Lima, E. (2016). Architecture and algorithms for the implementation of digital wireless receivers in FPGA and ASIC: ISDB-T and DVB-S2 cases [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/61967TESI

A survey of digital television broadcast transmission techniques

This paper is a survey of the transmission techniques used in digital television (TV) standards worldwide. With the increase in the demand for High-Definition (HD) TV, video-on-demand and mobile TV services, there was a real need for more bandwidth-efficient, flawless and crisp video quality, which motivated the migration from analogue to digital broadcasting. In this paper we present a brief history of the development of TV and then we survey the transmission technology used in different digital terrestrial, satellite, cable and mobile TV standards in different parts of the world. First, we present the Digital Video Broadcasting standards developed in Europe for terrestrial (DVB-T/T2), for satellite (DVB-S/S2), for cable (DVB-C) and for hand-held transmission (DVB-H). We then describe the Advanced Television System Committee standards developed in the USA both for terrestrial (ATSC) and for hand-held transmission (ATSC-M/H). We continue by describing the Integrated Services Digital Broadcasting standards developed in Japan for Terrestrial (ISDB-T) and Satellite (ISDB-S) transmission and then present the International System for Digital Television (ISDTV), which was developed in Brazil by adopteding the ISDB-T physical layer architecture. Following the ISDTV, we describe the Digital Terrestrial television Multimedia Broadcast (DTMB) standard developed in China. Finally, as a design example, we highlight the physical layer implementation of the DVB-T2 standar

Wi-Fi의 신뢰성 및 에너지 효율성 향상을 위한 MAC/PHY 기법

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2015. 8. 최성현.Over the last quarter century, wireless local area network (WLAN) technology has become an essential and indispensable part of our daily lives. Recently, a tremendously growing number of portable devices, such as smartphones, tablets and laptops, are being equipped with Wi-Fi, the hallmark of the IEEE 802.11 WLAN, in order to meet ever-increasing traffic demands at extremely low cost. Encouraged by this remarkable success, Wi-Fi is facing two trends. First, the state-of-the-art IEEE 802.11 specifications, e.g., IEEE 802.11n and 802.11ac, have focused on improving physical layer (PHY) rate by enabling multiple antennas, called multiple-input multiple-output (MIMO), and bandwidth widening, known as chan- nel bonding [1, 2]. Second, to achieve high throughput and transmission efficiency at medium access control (MAC) layer, IEEE 802.11n/ac standards have defined two types of frame aggregation techniques: MAC service data unit (MSDU) aggregation and MAC protocol data unit (MPDU) aggregation which amortize PHY/MAC proto- col overhead e.g., binary random backoff, physical layer convergence protocol (PLCP) preamble, and acknowledgement (ACK), over multiple frames by packing several MS- DUs and MPDUs into a single aggregate MSDU (A-MSDU) and aggregate MPDU (A-MPDU), respectively. Apparently, there is no doubt that these state-of-the-art features meet and fulfill i the requirements of Wi-Fi equipped device users by offering several hundred-fold in- creases in PHY rate and ubiquitous access. However, with respect to the demands of the battery-powered portable device users, the belief is easily broken from two per- spectives. First, since using higher PHY rate and longer A-MPDU are more vulnerable to channel errors especially for mobile users, the significant throughput performance degradation can be observed. Second, the emerging Wi-Fi chipsets, based on IEEE 802.11n/ac, consume much more energy than its legacy IEEE 802.11a/b/g counterparts due to the usage of MIMO and channel bonding. Nowadays, as the battery-powered portable device users place increasingly complex demands on the functionality of their devices which have strict power limitation, satisfaction with robust communication and battery life time is becoming increasingly important. In this dissertation, to address these challenges, we propose robust and energy efficient MAC/PHY layer strategies of Wi-Fi. First of all, to confirm those changes, we have conducted extensive experiments using state-of-the-art commercial IEEE 802.11n/ac-equipped devices and Microsofts Software Radio (Sora) platform. Our experiment results have revealed strong evidence that the use of long A-MPDU frames seriously deteriorates the Wi-Fi performance, i.e., throughput, especially for the pedestrian mobile users. Besides, we have found that the use of channel bonding remarkably consumes more energy, thus making Wi- Fi a primary energy consumer in the battery-powered portable devices. Especially, the energy cost is dominated by excessive and unnecessary listening and receiving operations. We begin an intra-frame rate control algorithm (Intra-RCA) design, called SNR- aware Intra-frame Rate Adaption (SIRA), which enhances the system performance of Wi-Fi in fast time-varying environments [3]. Widely used inter-frame rate control algorithms (Inter-RCAs), which select the PHY rate of each frame based on the time- ii averaged frame loss rate and the signal strength statistics, perform poorly for a long A-MPDU due to the channel variation in mobile environments. Unlike the previous ap- proaches, SIRA adapts the PHY rate on intra-frame basis, i.e., the PHY rate is updated in the middle of a frame according to user mobility. The performance of the proposed scheme is also evaluated by a trace-driven link level simulator employing the collected channel traces from real measurements. The simulation results show that SIRA outper- forms a standalone Inter-RCA in all tested traces. Despite its enhanced performance and considerable frame error reduction, the performance degradation caused by the impact of user mobility still remains due to the inherent limitation of IEEE 802.11 PHY design. Therefore, we conclude that this challenge should be solved with the assistance of PHY modification, and propose Channel-Aware Symbol Error Reduction (ChASER), a new practical channel estimation and tracking scheme for Wi-Fi receivers [4]. ChASER utilizes re-encoding and re-modulation of the received data symbol to keep up with the wireless channel dynamics at the granularity of orthogonal frequency division multi- plexing (OFDM) symbols. In addition, its low-complexity and feasibility of standard compliance is demonstrated by Microsofts Sora prototype implementation and experi- mentation. To our knowledge, ChASER is the first IEEE 802.11n-compatible channel tracking algorithm since other approaches addressing the time-varying channel con- ditions over a single (aggregated) frame duration require costly modifications of the IEEE 802.11 standard. Even though the above proposed approaches enhance the Wi- Fis throughput performance and robustness over conventional technique, the rest re- quirement of the portable device user, i.e., energy efficient Wi-Fi system design, should be addressed as ever. Accordingly, we propose a new power save operation as well as the corresponding protocol, called WiFi in Zizz (WiZizz), which judiciously exploits the characteristic iii of the channel bonding defined in IEEE 802.11ac and efficiently handles the channel bandwidth in an on-demand manner to minimize the traumatic energy spent by IEEE 802.11ac devices [5]. Our extensive measurement and simulation show significant per- formance improvement (as high as 73% energy saving) over a wide range of commu- nication scenarios. In addition, the feasibility of easy implementation is demonstrated by a prototype with a commercial 802.11ac device. To the best of our knowledge, WiZizz is the first IEEE 802.11ac-congenial energy efficient bandwidth management while other existing approaches require costly modifications of the IEEE 802.11ac specification. In summary, we propose a number of compelling algorithms and protocols to im- prove the robustness and energy efficiency in accordance with the paradigm shift of Wi-Fi. Moreover, our evaluation results show that the proposed schemes in this disser- tation are effective and yield considerable performance gain based on both the trace- driven link level simulation and the network level simulation which well reflects the wireless channel characteristics of the real world and the operation of IEEE 802.11 WLAN, respectively. We demonstrate the feasibility of our approaches by implement- ing prototypes in off-the-self IEEE 802.11n/ac devices and software-defined radio.Abstract Contents List of Tables List of Figures 1 Introduction 1.1 Paradigm Shift of Wi-Fi 1.2 DevelopmentTrend of IEEE802.11 1.2.1 MAC Features 1.2.2 PHY Features 1.3 Overview of Existing Approaches 1.3.1 Rate Adaptation 1.3.2 MPDU Length Optimization 1.3.3 Channel Estimation 1.3.4 Demystifying Wi-Fi Power Consumption 1.3.5 Minimizing Energy Consumption of Wi-Fi 1.4 Main Contributions 1.4.1 Impact of Mobility Analysis 1.4.2 Intra-frame Rate Adaptation 1.4.3 Enhanced Channel Estimation and Tracking 1.4.4 802.11ac Power Consumption Analysis 1.4.5 Energy Efficient Bandwidth Management 1.5 Organization of the Dissertation 2 Impact of Mobility 2.1 Introduction 2.2 Background 2.2.1 Channel Estimation and Compensation 2.2.2 Role of Pilot Subcarriers 2.2.3 Frame Aggregation 2.3 Measurement Study 2.3.1 Experimental Settings 2.3.2 Temporal Selectivity 2.3.3 Unreliability of A-MPDU in Mobile Environments 2.3.4 Relation between Symbol Dispersion and Mobility 2.4 Summary 3 SIRA: SNR-aware Intra-frame Rate Adaptation 3.1 Introduction 3.1.1 Revisit of Rate Adaptation Algorithms 3.1.2 Channel and Mobility Condition 3.2 ProposedAlgorithm 3.2.1 Pilot-based SNR Estimation 3.2.2 Mobility Detection 3.2.3 Unequal Modulation and Coding Scheme 3.2.4 Zero-overhead Feedback 3.2.5 SIRA Structure 3.3 Simulation 3.3.1 Trace-drivenLinkLevelSimulation 3.3.2 Mobility Detection Accuracy 3.3.3 Performance Comparison 3.4 Summary 4 ChASER: Channel-Aware Symbol Error Reduction 4.1 Introduction 4.2 Revisit of Channel Estimation Algorithms 4.3 ChASER Design 4.3.1 Channel Estimation using Unknown Data Symbols 4.3.2 Adaptive Filter 4.3.3 Adaptive Filter for MIMO 4.3.4 CRC-assisted Channel Correction 4.3.5 Summary of ChASER Operation 4.3.6 Impact of Step Size μ 4.4 Testbed Experiments 4.4.1 Prototype Implementation on SDR Platform 4.4.2 Testbed Settings 4.4.3 Performance Comparison 4.5 Simulation 4.5.1 Simulation Methodology 4.5.2 Estimation Accuracy 4.5.3 Impact of the A-MPDU Duration 4.5.4 Throughput Performance 4.6 Summary 5 Power Consumption of Wi-Fi: Modeling and Testbed Validation 5.1 Introduction 5.2 Revisit of IEEE 802.11ac Features 5.2.1 Wider Bandwidth Channel 5.2.2 MIMO and Higher Order Modulation 5.2.3 Relation between 802.11ac Features and Power 5.3 Modeling 802.11ac Power Consumption 5.3.1 Power Model of IEEE 802.11ac Receiver 5.3.2 Power Model of IEEE 802.11ac Transmitter 5.4 Power Consumption Measurement 5.4.1 Experimental Setting 5.4.2 Idle State Power Consumption 5.4.3 Receive State Power Consumption 5.4.4 Transmit State Power Consumption 5.4.5 PowerModelVerification 5.4.6 Summary 6 WiZizz: Energy Efficient Bandwidth Management 6.1 Introduction 6.2 WiFi Need to Zizz 6.3 WiZizz Design 6.3.1 Dynamic Mode 6.3.2 Pseudo-dynamic Mode 6.3.3 PHY-level Filtering 6.4 Testbed Experiments 6.4.1 Prototype Implementation and Testbed Setting 6.4.2 Bandwidth Switching Delay 6.4.3 Performance Evaluation 6.5 SimulationResults 6.5.1 Simulation Methodology 6.5.2 Constant Traffic Source with FixedMCS 6.5.3 Comprehensive Traffic Patterns 6.5.4 Collaboration with SMPS 6.6 Summary 7 Conclusion and Future Work 7.1 Research Contributions 7.2 Further Research Plans Abstract (In Korean) 감사의 글Docto

Channel Estimation Architectures for Mobile Reception in Emerging DVB Standards

Throughout this work, channel estimation techniques have been analyzed and proposed for moderate and very high mobility DVB (digital video broadcasting) receivers, focusing on the DVB-T2 (Digital Video Broadcasting - Terrestrial 2) framework and the forthcoming DVB-NGH (Digital Video Broadcasting - Next Generation Handheld) standard. Mobility support is one of the key features of these DVB specifications, which try to deal with the challenge of enabling HDTV (high definition television) delivery at high vehicular speed. In high-mobility scenarios, the channel response varies within an OFDM (orthogonal frequency-division multiplexing) block and the subcarriers are no longer orthogonal, which leads to the so-called ICI (inter-carrier interference), making the system performance drop severely. Therefore, in order to successfully decode the transmitted data, ICI-aware detectors are necessary and accurate CSI (channel state information), including the ICI terms, is required at the receiver. With the aim of reducing the number of parameters required for such channel estimation while ensuring accurate CSI, BEM (basis expansion model) techniques have been analyzed and proposed for the high-mobility DVB-T2 scenario. A suitable clustered pilot structure has been proposed and its performance has been compared to the pilot patterns proposed in the standard. Different reception schemes that effectively cancel ICI in combination with BEM channel estimation have been proposed, including a Turbo scheme that includes a BP (belief propagation) based ICI canceler, a soft-input decision-directed BEM channel estimator and the LDPC (low-density parity check) decoder. Numerical results have been presented for the most common channel models, showing that the proposed receiver schemes allow good reception, even in receivers with extremely high mobility (up to 0.5 of normalized Doppler frequency).Doktoretza tesi honetan, hainbat kanal estimazio teknika ezberdin aztertu eta proposatu dira mugikortasun ertain eta handiko DVB (Digital Video Broadcasting) hartzaileentzat, bigarren belaunaldiko Lurreko Telebista Digitalean DVB-T2 (Digital Video Broadcasting - Terrestrial 2 ) eta hurrengo DVB-NGH (Digital Video Broadcasting - Next Generation Handheld) estandarretan oinarrututa. Mugikortasuna bigarren belaunaldiko telebista estandarrean funtsezko ezaugarri bat da, HDTV (high definition television) zerbitzuak abiadura handiko hartzaileetan ahalbidetzeko erronkari aurre egiteko nahian. Baldintza horietan, kanala OFDM (ortogonalak maiztasun-zatiketa multiplexing ) sinbolo baten barruan aldatzen da, eta subportadorak jada ez dira ortogonalak, ICI-a (inter-carrier interference) sortuz, eta sistemaren errendimendua hondatuz. Beraz, transmititutako datuak behar bezala deskodeatzeko, ICI-a ekiditeko gai diren detektagailuak eta CSI-a (channel state information) zehatza, ICI osagaiak barne, ezinbestekoak egiten dira hartzailean. Kanalaren estimazio horretarako beharrezkoak diren parametro kopurua murrizteko eta aldi berean CSI zehatza bermatzeko, BEM (basis expansion model) teknika aztertu eta proposatu da ICI kanala identifikatzeko mugikortasun handiko DVB-T2 eszenatokitan. Horrez gain, pilotu egitura egokia proposatu da, estandarrean proposatutako pilotu ereduekin alderatuz BEM estimazioan oinarritua. ICI-a baliogabetzen duten hartzaile sistema ezberdin proposatu dira, Turbo sistema barne, non BP (belief propagation) detektagailua, soft BEM estimazioa eta LDPC (low-density parity check ) deskodetzailea uztartzen diren. Ohiko kanal ereduak erabilita, simulazio emaitzak aurkeztu dira, proposatutako hartzaile sistemak mugikortasun handiko kasuetan harrera ona dutela erakutsiz, 0.5 Doppler maiztasun normalizaturaino.Esta tesis doctoral analiza y propone diferentes técnicas de estimación de canal para receptores DVB (Digital Video Broadcasting) con movilidad moderada y alta, centrándose en el estándar de segunda generación DVB-T2 (Digital Video Broadcasting - Terrestrial 2 ) y en el próximó estándar DVB-NGH (Digital Video Broadcasting - Next Generation Handheld ). La movilidad es una de las principales claves de estas especificaciones, que tratan de lidiar con el reto de permitir la recepción de señal HDTV (high definition television) en receptores móviles. En escenarios de alta movilidad, la respuesta del canal varía dentro de un símbolo OFDM (orthogonal frequency-division multiplexing ) y las subportadoras ya no son ortogonales, lo que genera la llamada ICI (inter-carrier interference), deteriorando el rendimiento de los receptores severamente. Por lo tanto, con el fin de decodificar correctamente los datos transmitidos, detectores capaces de suprimir la ICI y una precisa CSI (channel state information), incluyendo los términos de ICI, son necesarios en el receptor. Con el objetivo de reducir el número de parámetros necesarios para dicha estimación de canal, y al mismo tiempo garantizar una CSI precisa, la técnica de estimación BEM (basis expansion model) ha sido analizada y propuesta para identificar el canal con ICI en receptores DVB-T2 de alta movilidad. Además se ha propuesto una estructura de pilotos basada en clústers, comparando su rendimiento con los patrones de pilotos establecidos en el estándar. Se han propuesto diferentes sistemas de recepción que cancelan ICI en combinación con la estimación BEM, incluyendo un esquema Turbo que incluye un detector BP (belief propagation), un estimador BEM soft y un decodificador LDPC (low-density parity check). Se han presentado resultados numéricos para los modelos de canal más comunes, demostrando que los sistemas de recepción propuestos permiten la decodificación correcta de la señal incluso en receptores con movilidad muy alta (hasta 0,5 de frecuencia de Doppler normalizada)

Advanced OFDM systems for terrestrial multimedia links

Recently, there has been considerable discussion about new wireless technologies and standards able to achieve high data rates. Due to the recent advances of digital signal processing and Very Large Scale Integration (VLSI) technologies, the initial obstacles encountered for the implementation of Orthogonal Frequency Division Multiplexing (OFDM) modulation schemes, such as massive complex multiplications and high speed memory accesses, do not exist anymore. OFDM offers strong multipath protection due to the insertion of the guard interval; in particular, the OFDM-based DVB-T standard had proved to offer excellent performance for the broadcasting of multimedia streams with bitrates over ten megabits per second in difficult terrestrial propagation channels, for fixed and portable applications. Nevertheless, for mobile scenarios, improving the receiver design is not enough to achieve error-free transmission especially in presence of deep shadow and multipath fading and some modifications of the standard can be envisaged. To address long and medium range applications like live mobile wireless television production, some further modifications are required to adapt the modulated bandwidth and fully exploit channels up to 24MHz wide. For these reasons, an extended OFDM system is proposed that offers variable bandwidth, improved protection to shadow and multipath fading and enhanced robustness thanks to the insertion of deep time-interleaving coupled with a powerful turbo codes concatenated error correction scheme. The system parameters and the receiver architecture have been described in C++ and verified with extensive simulations. In particular, the study of the receiver algorithms was aimed to achieve the optimal tradeoff between performances and complexity. Moreover, the modulation/demodulation chain has been implemented in VHDL and a prototype system has been manufactured. Ongoing field trials are demonstrating the ability of the proposed system to successfully overcome the impairments due to mobile terrestrial channels, like multipath and shadow fading. For short range applications, Time-Division Multiplexing (TDM) is an efficient way to share the radio resource between multiple terminals. The main modulation parameters for a TDM system are discussed and it is shown that the 802.16a TDM OFDM physical layer fulfills the application requirements; some practical examples are given. A pre-distortion method is proposed that exploit the reciprocity of the radio channel to perform a partial channel inversion achieving improved performances with no modifications of existing receivers