Design and Implementation of Belief Propagation Symbol Detectors for Wireless Intersymbol Interference Channels

In modern wireless communication systems, intersymbol interference (ISI) introduced by frequency selective fading is one of the major impairments to reliable data communication. In ISI channels, the receiver observes the superposition of multiple delayed reflections of the transmitted signal, which will result errors in the decision device. As the data rate increases, the effect of ISI becomes severe. To combat ISI, equalization is usually required for symbol detectors. The optimal maximum-likelihood sequence estimation (MLSE) based on the Viterbi algorithm (VA) may be used to estimate the transmitted sequence in the presence of the ISI. However, the computational complexity of the MLSE increases exponentially with the length of the channel impulse response (CIR). Even in channels which do not exhibit significant time dispersion, the length of the CIR will effectively increase as the sampling rate goes higher. Thus the optimal MLSE is impractical to implement in the majority of practical wireless applications. This dissertation is devoted to exploring practically implementable symbol detectors with near-optimal performance in wireless ISI channels. Particularly, we focus on the design and implementation of an iterative detector based on the belief propagation (BP) algorithm. The advantage of the BP detector is that its complexity is solely dependent on the number of nonzero coefficients in the CIR, instead of the length of the CIR. We also extend the work of BP detector design for various wireless applications. Firstly, we present a partial response BP (PRBP) symbol detector with near-optimal performance for channels which have long spanning durations but sparse multipath structure. We implement the architecture by cascading an adaptive linear equalizer (LE) with a BP detector. The channel is first partially equalized by the LE to a target impulse response (TIR) with only a few nonzero coefficients remaining. The residual ISI is then canceled by a more sophisticated BP detector. With the cascaded LE-BP structure, the symbol detector is capable to achieve a near-optimal error rate performance with acceptable implementation complexity. Moreover, we present a pipeline high-throughput implementation of the detector for channel length 30 with quadrature phase-shift keying (QPSK) modulation. The detector can achieve a maximum throughput of 206 Mb/s with an estimated core area of 3.162 mm^{2} using 90-nm technology node. At a target frequency of 515 MHz, the dynamic power is about 1.096 W. Secondly, we investigate the performance of aforementioned PRBP detector under a more generic 3G channel rather than the sparse channel. Another suboptimal partial response maximum-likelihood (PRML) detector is considered for comparison. Similar to the PRBP detector, the PRML detector also employs a hybrid two-stage scheme, in order to allow a tradeoff between performance and complexity. In simulations, we consider a slow fading environment and use the ITU-R 3G channel models. From the numerical results, it is shown that in frequency-selective fading wireless channels, the PRBP detector provides superior performance over both the traditional minimum mean squared error linear equalizer (MMSE-LE) and the PRML detector. Due to the effect of colored noise, the PRML detector in fading wireless channels is not as effective as it is in magnetic recording applications. Thirdly, we extend our work to accommodate the application of Advanced Television Systems Committee (ATSC) digital television (DTV) systems. In order to reduce error propagation caused by the traditional decision feedback equalizer (DFE) in DTV receiver, we present an adaptive decision feedback sparsening filter BP (DFSF-BP) detector, which is another form of PRBP detector. Different from the aforementioned LE-BP structure, in the DFSF-BP scheme, the BP detector is followed by a nonlinear filter called DFSF as the partial response equalizer. In the first stage, the DFSF employs a modified feedback filter which leaves the strongest post-cursor ISI taps uncorrected. As a result, a long ISI channel is equalized to a sparse channel having only a small number of nonzero taps. In the second stage, the BP detector is applied to mitigate the residual ISI. Since the channel is typically time-varying and suffers from Doppler fading, the DFSF is adapted using the least mean square (LMS) algorithm, such that the amplitude and the locations of the nonzero taps of the equalized sparse channel appear to be fixed. As such, the channel appears to be static during the second stage of equalization which consists of the BP detector. Simulation results demonstrate that the proposed scheme outperforms the traditional DFE in symbol error rate, under both static channels and dynamic ATSC channels. Finally, we study the symbol detector design for cooperative communications, which have attracted a lot of attention recently for its ability to exploit increased spatial diversity available at distributed antennas on other nodes. A system framework employing non-orthogonal amplify-and-forward half-duplex relays through ISI channels is developed. Based on the system model, we first design and implement an optimal maximum-likelihood detector based on the Viterbi algorithm. As the relay period increases, the effective CIR between the source and the destination becomes long and sparse, which makes the optimal detector impractical to implement. In order to achieve a balance between the computational complexity and performance, several sub-optimal detectors are proposed. We first present a multitrellis Viterbi algorithm (MVA) based detector which decomposes the original trellis into multiple parallel irregular sub-trellises by investigating the dependencies between the received symbols. Although MVA provides near-optimal performance, it is not straightforward to decompose the trellis for arbitrary ISI channels. Next, the decision feedback sequence estimation (DFSE) based detector and BP-based detector are proposed for cooperative ISI channels. Traditionally these two detectors are used with fixed, static channels. In our model, however, the effective channel is periodically time-varying, even when the component channels themselves are static. Consequently, we modify these two detector to account for cooperative ISI channels. Through simulations in frequency selective fading channels, we demonstrate the uncoded performance of the DFSE detector and the BP detector when compared to the optimal MLSE detector. In addition to quantifying the performance of these detectors, we also include an analysis of the implementation complexity as well as a discussion on complexity/performance tradeoffs

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

Interactive Digital Terrestrial Television: The Interoperability Challenge in Brazil

This paper introduces different standards implemented in existing Digital Terrestrial Television Broadcasting systems to allow the fruition of interactive services and applications through digital Set Top Boxes. It focuses on the interoperability issue between the Brazilian and the European architectures. In fact, despite in Brazil the GEM specification has been designed to foster wide content compatibility across a range of interactive platforms, it has never come to a final implementation and deployment. As a result the interoperability issue has been deeply explored in the BEACON project and an innovative system architecture has been developed to deploy t-learning services across Europe and Brazil, providing integration of those systems that were not able to interoperate until nowadays. This work is an important step in the direction of standards' interoperability. As a result, MHP and Ginga NCL-Lua implementation appeared to be the very best choice to deliver interactive services in an interoperable mode between European and Brazilian digital television

A Cognitive TV White Space Access Framework

Given the current boom in applications and services for mobile devices, data traffic is rapidly expanding, with the consequence that increasing spectrum capacity is being mandated. Following the switchover from analogue to digital platforms, Television White Space (TVWS) affords a fertile opportunity to supplement existing licensed spectrum to ease this scarcity. There are however, a number of obstacles to wide-scale TVWS adoption, including the accurate detection of primary users (PU), the hidden node problem and bandwidth availability for unlicensed secondary users (SU). Regulatory and industry bodies have sought to address some of these issues using a static database for spectrum access decisions, though this involves manual maintenance and accuracy can be compromised due to a lack of real-time information. While the new IEEE802.11af wireless local area network (WLAN) standard attempts to resolve some SU access issues, there remain many challenges, such as the critical asymmetry between mobile and base station power resources. This thesis presents a new cognitive TVWS access framework encompassing a real-time sensing paradigm for TVWS deployment that uses a spectrum-efficient scheme to uphold quality-of-service (QoS) for both PU and SU. A novel dynamic spectrum allocation (DSA) model has been formulated allied with a resilient interference management system which exploits the unique way digital terrestrial TV channels are allocated in different geographical areas. A margin strategy has been framed to support efficient TVWS channel reuse, with an exclusion zone established to overcome the hidden node problem, while an innovative routing algorithm using cross-layer information, both extends coverage capacity and maximises QoS provision by ensuring a more balanced resource allocation. Critical evaluation of the new access framework confirms that significant QoS improvements for SU are achieved compared to existing TVWS techniques. It importantly embodies a generic, practical, resource-efficient solution for TVWS deployment, which is compliant with current PU regulatory requirements

Potentzia domeinuko NOMA 5G sareetarako eta haratago

Tesis inglés 268 p. -- Tesis euskera 274 p.During the last decade, the amount of data carried over wireless networks has grown exponentially. Several reasons have led to this situation, but the most influential ones are the massive deployment of devices connected to the network and the constant evolution in the services offered. In this context, 5G targets the correct implementation of every application integrated into the use cases. Nevertheless, the biggest challenge to make ITU-R defined cases (eMBB, URLLC and mMTC) a reality is the improvement in spectral efficiency. Therefore, in this thesis, a combination of two mechanisms is proposed to improve spectral efficiency: Non-Orthogonal Multiple Access (NOMA) techniques and Radio Resource Management (RRM) schemes. Specifically, NOMA transmits simultaneously several layered data flows so that the whole bandwidth is used throughout the entire time to deliver more than one service simultaneously. Then, RRM schemes provide efficient management and distribution of radio resources among network users. Although NOMA techniques and RRM schemes can be very advantageous in all use cases, this thesis focuses on making contributions in eMBB and URLLC environments and proposing solutions to communications that are expected to be relevant in 6G

Cooperating broadcast and cellular conditional access system for digital television

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The lack of interoperability between Pay‐TV service providers and a horizontally integrated business transaction model have compromised the competition in the Pay‐TV market. In addition, the lack of interactivity with customers has resulted in high churn rate and improper security measures have contributed into considerable business loss. These issues are the main cause of high operational costs and subscription fees in the Pay‐TV systems. This paper presents a novel end‐to‐end system architecture for Pay‐TV systems cooperating mobile and broadcasting technologies. It provides a cost‐effective, scalable, dynamic and secure access control mechanism supporting converged services and new business opportunities in Pay‐TV systems. It enhances interactivity, security and potentially reduces customer attrition and operational cost. In this platform, service providers can effectively interact with their customers, personalise their services and adopt appropriate security measures. It breaks up the rigid relationship between a viewer and set‐top box as imposed by traditional conditional access systems, thus, a viewer can fully enjoy his entitlements via an arbitrary set‐top box. Having thoroughly considered state‐of‐the‐art technologies currently being used across the world, the thesis highlights novel use cases and presents the full design and implementation aspects of the system. The design section is enriched by providing possible security structures supported thereby. A business collaboration structure is proposed, followed by a reference model for implementing the system. Finally, the security architectures are analysed to propose the best architecture on the basis of security, complexity and set‐top box production cost criteria

Cognitive Radio and TV White Space (TVWS) Applications

As more user applications emerge for wireless devices, the corresponding amount of traffic is rapidly expanding, with the corollary that ever-greater spectrum capacity is required. Service providers are experiencing deployment blockages due to insufficient bandwidth being available to accommodate such devices. TV White Space (TVWS) represents an opportunity to supplement existing licensed spectrum by exploiting unlicensed resources. TVWS spectrum has materialised from the unused TV channels in the switchover from analogue to digital platforms. The main obstacles to TVWS adoption are reliable detection of primary users (PU) i.e., TV operators and consumers, allied with specifically, the hidden node problem. This chapter presents a new Generalised Enhanced Detection Algorithm (GEDA) that exploits the unique way Digital Terrestrial TV (DTT) channels are deployed in different geographical areas. GEDA effectively transforms an energy detector into a feature sensor to achieve significant improvements in detection probability of a DTT PU. Furthermore, by framing a novel margin strategy utilising a keep out contour, the hidden node issue is resolved, and a viable secondary user sensing solution formulated. Experimental results for a cognitive radio TVWS model have formalised both the bandwidth and throughput gains secured by TVWS users with this new paradigm

Spectrum Policy and Management

This project provides an examination of the FCC’s policies towards spectrum reallocation. The project examines the National Broadband Plan and how the FCC has approached the goals described within it. The demand for broadband communications has increased dramatically in recent years and has resulted in a predicted spectrum deficit in the near future. In addition to a number of spectrum auctions and their winners the project examines how the redistribution of spectrum impacts the broadband community. The project also provides an examination of spectrum reallocation and policy in other countries, to provide a broader view of spectrum policy. Finally the project examines new spectrum technologies and spectrum usage policies to further examine how the US’s spectrum policies should evolve

Single-Frequency Network Terrestrial Broadcasting with 5GNR Numerology

L'abstract è presente nell'allegato / the abstract is in the attachmen

A Survey of Cognitive Radio Access to TV White Spaces

Cognitive radio is being intensively researched as the enabling technology for license-exempt access to the so-called TV White Spaces (TVWS), large portions of spectrum in the UHF/VHF bands which become available on a geographical basis after digital switchover. Both in the US, and more recently, in the UK the regulators have given conditional endorsement to this new mode of access. This paper reviews the state-of-the-art in technology, regulation, and standardisation of cognitive access to TVWS. It examines the spectrum opportunity and commercial use cases associated with this form of secondary access