134 research outputs found
Receiver design for nonlinearly distorted OFDM : signals applications in radio-over-fiber systems
Tese de doutoramento. Engenharia Electrotécnica e de Computadores. Universidade do Porto. Faculdade de Engenharia. 201
Frequency estimation for single-carrier and OFDM signals in communication and radar systems
Eine der klassischen Problemstellungen in der Signalverarbeitung
ist die Schaetzung der Frequenz eines Signals, das von weissem
Rauschen additiv ueberlagert ist. Diese bedeutende Aufgabe
stellt sich in vielen verschiedenen Anwendungsbereichen wie der
Kommunikationstechnik, beim Doppler-Radar, beim Radar mit
synthetischer Apertur (SAR), beim Array Processing, bei
Radio-Frequency-IDentification (RFID), bei Resonanz-Sensoren usw.
Die Anforderungen bezueglich der Leistungsfaehigkeit des
Frequenzschaetzers haengen von der Anwendung ab. Die
Leistungsfaehigkeit ist dabei oft unter Beruecksichtigung
der folgenden 4 Punkte definiert: i) Genauigkeit,
Richtigkeit der Schaetzung, ii) Arbeitsbereich
(estimation range), iii) Grenzwerte der Schaetzung (im
Vergleich zu einer theoretisch moeglichen Schwelle) und
iv) Komplexitaet der Implementierung. Diese
Anforderungen koennen nicht unabhaengig voneinander
betrachtet werden und stehen sich teilweise gegenueber.
Beispielsweise erfordert die Erzielung von Ergebnissen nahe an der
theoretisch moeglichen Schwelle eine hohe Komplexitaet.
Ebenso kann ein Schaetz-ergebnis von hoher Genauigkeit oftmals
nur fuer einen stark eingeschraenkten Arbeitsbereich erzielt
werden. Die Frequenzschaetzung ist im Falle von durch Fading
hervorgerufenem multiplikativem Rauschen noch herausfordernder. Es
handelt sich dann um den allgemeinen Fall der
Frequenzschaetzung. Bisher hat man bereits viel Arbeit in die
Ableitung eines Schaetzers fĂĽr diesen allgemeinen Fall
investiert. Ein Schaetzer, der optimal bezueglich aller oben
genannten Kriterien ist, duerfte allerdings nur schwer zu
finden sein.
In dieser Dissertation wird mit Blick auf Kommunikationstechnik
und Radaranwendungen ein verallgemeinerter, in geschlossener Form
vorliegender, Frequenzschaetzer eingefuehrt, der alle
genannten Kriterien der Leistungs-faehigkeit
beruecksichtigt. Die Herleitung des Schaetzers beruht auf
dem Prinzip der kleinsten Fehlerquadrate fuer den nichtlinearen
Fall in Verbindung mit der Abelschen partiellen Summation. Zudem
werden verschiedene modifizierte Frequenzschaetzer vorgestellt,
die sich fuer Faelle in denen kein Fading oder nur sehr
geringes Fading auftritt, eignen.Estimating the frequency of a signal embedded in additive white
Gaussian noise is one of the classical problems in signal
processing. It is of fundamental importance in various
applications such as in communications, Doppler radar,
synthetic aperture radar (SAR), array processing, radio
frequency identification (RFID), resonance sensor, etc.
The requirement on the performance of the frequency estimator
varies with the application. The performance is often defined
using four indexes: i). estimation accuracy, ii).
estimation range, iii). estimation threshold, and
iv). implementation complexity. These indexes may be in
contrast with each other. For example, achieving a low threshold
usually implies a high complexity. Likewise, good estimation
accuracy is often obtained at the price of a narrow estimation
range. The estimation becomes even more difficult in the presence
of fading-induced multiplicative noise which is considered to be
the general case of the frequency estimation problem. There have
been a lot of efforts in deriving the estimator for the general
case, however, a generalized estimator that fulfills all indexes
can be hardly obtained.
Focusing on communications and radar applications, this thesis
proposes a new generalized closed-form frequency estimator that
compromises all performance indexes. The derivation of the
proposed estimator relies on the nonlinear least-squares principle
in conjunction with the well known summation-by-parts formula. In
addition to this, several modified frequency estimators suitable
for non-fading or very slow fading scenarios, are also introduced
in this thesis
Physical Layer Techniques for Wireless Communication Systems
The increasing diffusion of mobile devices requiring, everywhere and every time, reliable connections able to support the more common applications, induced in the last years the deployment of telecommunication networks based on technologies capable to respond effectively to the ever-increasing market demand, still a long way off from saturation level.
Multicarrier transmission techniques employed in standards for local networks (Wi-Fi) and metropolitan networks (WiMAX) and for many years hot research topic, have been definitely adopted beginning from the fourth generation of cellular systems (LTE). The adoption of multicarrier signaling techniques if on one hand has brought significant advantages to counteract the detrimental effects in environments with particularly harsh propagation channel, on the other hand, has imposed very strict requirements on sensitivity to recovery errors of the carrier frequency offset (CFO) due to the resulting impact on correct signal detection.
The main focus of the thesis falls in this area, investigating some aspects relating to synchronization procedures for system based on multicarrier signaling. Particular reference will be made to a network entry procedure for LTE networks and to CFO recovery for OFDM, fltered multitone modulation and direct conversion receivers.
Other contributions pertaining to physical layer issues for communication systems,
both radio and over acoustic carrier, conclude the thesis
Spectrally and Energy Efficient Wireless Communications: Signal and System Design, Mathematical Modelling and Optimisation
This thesis explores engineering studies and designs aiming to meeting the requirements of enhancing capacity and energy efficiency for next generation communication networks. Challenges of spectrum scarcity and energy constraints are addressed and new technologies are proposed, analytically investigated and examined.
The thesis commences by reviewing studies on spectrally and energy-efficient techniques, with a special focus on non-orthogonal multicarrier modulation, particularly spectrally efficient frequency division multiplexing (SEFDM). Rigorous theoretical and mathematical modelling studies of SEFDM are presented. Moreover, to address the potential application of SEFDM under the 5th generation new radio (5G NR) heterogeneous numerologies, simulation-based studies of SEFDM coexisting with orthogonal frequency division multiplexing (OFDM) are conducted. New signal formats and corresponding transceiver structure are designed, using a Hilbert transform filter pair for shaping pulses. Detailed modelling and numerical investigations show that the proposed signal doubles spectral efficiency without performance degradation, with studies of two signal formats; uncoded narrow-band internet of things (NB-IoT) signals and unframed turbo coded multi-carrier signals. The thesis also considers using constellation shaping techniques and SEFDM for capacity enhancement in 5G system. Probabilistic shaping for SEFDM is proposed and modelled to show both transmission energy reduction and bandwidth saving with advantageous flexibility for data rate adaptation. Expanding on constellation shaping to improve performance further, a comparative study of multidimensional modulation techniques is carried out. A four-dimensional signal, with better noise immunity is investigated, for which metaheuristic optimisation algorithms are studied, developed, and conducted to optimise bit-to-symbol mapping. Finally, a specially designed machine learning technique for signal and system design in physical layer communications is proposed, utilising the application of autoencoder-based end-to-end learning. Multidimensional signal modulation with multidimensional constellation shaping is proposed and optimised by using machine learning techniques, demonstrating significant improvement in spectral and energy efficiencies
Real-Time Localization Using Software Defined Radio
Service providers make use of cost-effective wireless solutions to identify, localize, and possibly track users using their carried MDs to support added services, such as geo-advertisement, security, and management. Indoor and outdoor hotspot areas play a significant role for such services. However, GPS does not work in many of these areas. To solve this problem, service providers leverage available indoor radio technologies, such as WiFi, GSM, and LTE, to identify and localize users. We focus our research on passive services provided by third parties, which are responsible for (i) data acquisition and (ii) processing, and network-based services, where (i) and (ii) are done inside the serving network. For better understanding of parameters that affect indoor localization, we investigate several factors that affect indoor signal propagation for both Bluetooth and WiFi technologies. For GSM-based passive services, we developed first a data acquisition module: a GSM receiver that can overhear GSM uplink messages transmitted by MDs while being invisible. A set of optimizations were made for the receiver components to support wideband capturing of the GSM spectrum while operating in real-time. Processing the wide-spectrum of the GSM is possible using a proposed distributed processing approach over an IP network. Then, to overcome the lack of information about tracked devices’ radio settings, we developed two novel localization algorithms that rely on proximity-based solutions to estimate in real environments devices’ locations. Given the challenging indoor environment on radio signals, such as NLOS reception and multipath propagation, we developed an original algorithm to detect and remove contaminated radio signals before being fed to the localization algorithm. To improve the localization algorithm, we extended our work with a hybrid based approach that uses both WiFi and GSM interfaces to localize users. For network-based services, we used a software implementation of a LTE base station to develop our algorithms, which characterize the indoor environment before applying the localization algorithm. Experiments were conducted without any special hardware, any prior knowledge of the indoor layout or any offline calibration of the system
Optical Communication
Optical communication is very much useful in telecommunication systems, data processing and networking. It consists of a transmitter that encodes a message into an optical signal, a channel that carries the signal to its desired destination, and a receiver that reproduces the message from the received optical signal. It presents up to date results on communication systems, along with the explanations of their relevance, from leading researchers in this field. The chapters cover general concepts of optical communication, components, systems, networks, signal processing and MIMO systems. In recent years, optical components and other enhanced signal processing functions are also considered in depth for optical communications systems. The researcher has also concentrated on optical devices, networking, signal processing, and MIMO systems and other enhanced functions for optical communication. This book is targeted at research, development and design engineers from the teams in manufacturing industry, academia and telecommunication industries
Implementation of self-tuning control for turbine generators
PhD ThesisThis thesis documents the work that has been done towards the development of
a 'practical' self-tuning controller for turbine generator plant. It has been shown
by simulation studies and practical investigations using a micro-alternator system
that a significant enhancement in the overall performance in terms of control and
stability can be achieved by improving the primary controls of a turbine generator
using self-tuning control.
The self-tuning AVR is based on the Generalised Predictive Control strategy. The
design of the controller has been done using standard off-the-shelf microprocessor
hardware and structured software design techniques. The proposed design is thus
flexible, cost-effective, and readily applicable to 'real' generating plant. Several
practical issues have been tackled during the design of the self-tuning controller and
techniques to improve the robustness of the measurement system, controller, and
parameter estimator have been proposed and evaluated. A simple and robust
measurement system for plant variables based on software techniques has been
developed and its suitability for use in the self-tuning controller has been practically
verified. The convergence, adaptability, and robustness aspects of the parameter
estimator have been evaluated and shown to be suitable for long-term operation in
'real' self-tuning controllers.
The self-tuning AVR has been extensively evaluated under normal and fault
conditions of the turbine generator. It has been shown that this new controller is
superior in performance when compared with a conventional lag-lead type of
fixed-parameter digital AVR. The use of electrical power as a supplementary
feedback signal in the new AVR is shown to further improve the dynamic stability
of the system.
The self-tuning AVR has been extended to a multivariable integrated self-tuning
controller which combines the AVR and EHG functions. The flexibility of the new
AVR to enable its expansion for more complex control applications has thus been
demonstrated. Simple techniques to incorporate constraints on control inputs
without upsetting the loop decoupling property of the multivariable controller have
been proposed and evaluated. It is shown that a further improvement in control
performance and stability can be achieved by the integrated controller.Parsons Turbine Generators Ltd
Sensing and Signal Processing in Smart Healthcare
In the last decade, we have witnessed the rapid development of electronic technologies that are transforming our daily lives. Such technologies are often integrated with various sensors that facilitate the collection of human motion and physiological data and are equipped with wireless communication modules such as Bluetooth, radio frequency identification, and near-field communication. In smart healthcare applications, designing ergonomic and intuitive human–computer interfaces is crucial because a system that is not easy to use will create a huge obstacle to adoption and may significantly reduce the efficacy of the solution. Signal and data processing is another important consideration in smart healthcare applications because it must ensure high accuracy with a high level of confidence in order for the applications to be useful for clinicians in making diagnosis and treatment decisions. This Special Issue is a collection of 10 articles selected from a total of 26 contributions. These contributions span the areas of signal processing and smart healthcare systems mostly contributed by authors from Europe, including Italy, Spain, France, Portugal, Romania, Sweden, and Netherlands. Authors from China, Korea, Taiwan, Indonesia, and Ecuador are also included
High mobility in OFDM based wireless communication systems
Orthogonal Frequency Division Multiplexing (OFDM) has been adopted as the transmission scheme in most of the wireless systems we use on a daily basis. It brings with it several inherent advantages that make it an ideal waveform candidate in the physical layer. However, OFDM based wireless systems are severely affected in High Mobility scenarios. In this thesis, we investigate the effects of mobility on OFDM based wireless systems and develop novel techniques to estimate the channel and compensate its effects at the receiver. Compressed Sensing (CS) based channel estimation techniques like the Rake Matching Pursuit (RMP) and the Gradient Rake Matching Pursuit (GRMP) are developed to estimate the channel in a precise, robust and computationally efficient manner. In addition to this, a Cognitive Framework that can detect the mobility in the channel and configure an optimal estimation scheme is also developed and tested. The Cognitive Framework ensures a computationally optimal channel estimation scheme in all channel conditions. We also demonstrate that the proposed schemes can be adapted to other wireless standards easily. Accordingly, evaluation is done for three current broadcast, broadband and cellular standards. The results show the clear benefit of the proposed schemes in enabling high mobility in OFDM based wireless communication systems.Orthogonal Frequency Division Multiplexing (OFDM) wurde als Übertragungsschema in die meisten drahtlosen Systemen, die wir täglich verwenden, übernommen. Es bringt mehrere inhärente Vorteile mit sich, die es zu einem idealen Waveform-Kandidaten in der Bitübertragungsschicht (Physical Layer) machen. Allerdings sind OFDM-basierte drahtlose Systeme in Szenarien mit hoher Mobilität stark beeinträchtigt. In dieser Arbeit untersuchen wir die Auswirkungen der Mobilität auf OFDM-basierte drahtlose Systeme und entwickeln neuartige Techniken, um das Verhalten des Kanals abzuschätzen und seine Auswirkungen am Empfänger zu kompensieren. Auf Compressed Sensing (CS) basierende Kanalschätzverfahren wie das Rake Matching Pursuit (RMP) und das Gradient Rake Matching Pursuit (GRMP) werden entwickelt, um den Kanal präzise, robust und rechnerisch effizient abzuschätzen. Darüber hinaus wird ein Cognitive Framework entwickelt und getestet, das die Mobilität im Kanal erkennt und ein optimales Schätzungsschema konfiguriert. Das Cognitive Framework gewährleistet ein rechnerisch optimales Kanalschätzungsschema für alle möglichen Kanalbedingungen. Wir zeigen außerdem, dass die vorgeschlagenen Schemata auch leicht an andere Funkstandards angepasst werden können. Dementsprechend wird eine Evaluierung für drei aktuelle Rundfunk-, Breitband- und Mobilfunkstandards durchgeführt. Die Ergebnisse zeigen den klaren Vorteil der vorgeschlagenen Schemata bei der Ermöglichung hoher Mobilität in OFDM-basierten drahtlosen Kommunikationssystemen
Belle II Technical Design Report
The Belle detector at the KEKB electron-positron collider has collected
almost 1 billion Y(4S) events in its decade of operation. Super-KEKB, an
upgrade of KEKB is under construction, to increase the luminosity by two orders
of magnitude during a three-year shutdown, with an ultimate goal of 8E35 /cm^2
/s luminosity. To exploit the increased luminosity, an upgrade of the Belle
detector has been proposed. A new international collaboration Belle-II, is
being formed. The Technical Design Report presents physics motivation, basic
methods of the accelerator upgrade, as well as key improvements of the
detector.Comment: Edited by: Z. Dole\v{z}al and S. Un
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