7 research outputs found
Multi-standard programmable baseband modulator for next generation wireless communication
Considerable research has taken place in recent times in the area of
parameterization of software defined radio (SDR) architecture. Parameterization
decreases the size of the software to be downloaded and also limits the
hardware reconfiguration time. The present paper is based on the design and
development of a programmable baseband modulator that perform the QPSK
modulation schemes and as well as its other three commonly used variants to
satisfy the requirement of several established 2G and 3G wireless communication
standards. The proposed design has been shown to be capable of operating at a
maximum data rate of 77 Mbps on Xilinx Virtex 2-Pro University field
programmable gate array (FPGA) board. The pulse shaping root raised cosine
(RRC) filter has been implemented using distributed arithmetic (DA) technique
in the present work in order to reduce the computational complexity, and to
achieve appropriate power reduction and enhanced throughput. The designed
multiplier-less programmable 32-tap FIR-based RRC filter has been found to
withstand a peak inter-symbol interference (ISI) distortion of -41 dB
Dirty RF Signal Processing for Mitigation of Receiver Front-end Non-linearity
Moderne drahtlose Kommunikationssysteme stellen hohe und teilweise
gegensätzliche Anforderungen an die Hardware der Funkmodule, wie z.B.
niedriger Energieverbrauch, große Bandbreite und hohe Linearität. Die
Gewährleistung einer ausreichenden Linearität ist, neben anderen analogen
Parametern, eine Herausforderung im praktischen Design der Funkmodule. Der
Fokus der Dissertation liegt auf breitbandigen HF-Frontends für
Software-konfigurierbare Funkmodule, die seit einigen Jahren kommerziell
verfügbar sind. Die praktischen Herausforderungen und Grenzen solcher
flexiblen Funkmodule offenbaren sich vor allem im realen Experiment. Eines
der Hauptprobleme ist die Sicherstellung einer ausreichenden analogen
Performanz über einen weiten Frequenzbereich. Aus einer Vielzahl an
analogen Störeffekten behandelt die Arbeit die Analyse und Minderung von
Nichtlinearitäten in Empfängern mit direkt-umsetzender Architektur. Im
Vordergrund stehen dabei Signalverarbeitungsstrategien zur Minderung
nichtlinear verursachter Interferenz - ein Algorithmus, der besser unter
"Dirty RF"-Techniken bekannt ist. Ein digitales Verfahren nach der
Vorwärtskopplung wird durch intensive Simulationen, Messungen und
Implementierung in realer Hardware verifiziert. Um die Lücken zwischen
Theorie und praktischer Anwendbarkeit zu schließen und das Verfahren in
reale Funkmodule zu integrieren, werden verschiedene Untersuchungen
durchgeführt. Hierzu wird ein erweitertes Verhaltensmodell entwickelt, das
die Struktur direkt-umsetzender Empfänger am besten nachbildet und damit
alle Verzerrungen im HF- und Basisband erfasst. Darüber hinaus wird die
Leistungsfähigkeit des Algorithmus unter realen Funkkanal-Bedingungen
untersucht. Zusätzlich folgt die Vorstellung einer ressourceneffizienten
Echtzeit-Implementierung des Verfahrens auf einem FPGA. Abschließend
diskutiert die Arbeit verschiedene Anwendungsfelder, darunter spektrales
Sensing, robuster GSM-Empfang und GSM-basiertes Passivradar. Es wird
gezeigt, dass nichtlineare Verzerrungen erfolgreich in der digitalen
Domäne gemindert werden können, wodurch die Bitfehlerrate gestörter
modulierter Signale sinkt und der Anteil nichtlinear verursachter
Interferenz minimiert wird. Schließlich kann durch das Verfahren die
effektive Linearität des HF-Frontends stark erhöht werden. Damit wird der
zuverlässige Betrieb eines einfachen Funkmoduls unter dem Einfluss der
Empfängernichtlinearität möglich. Aufgrund des flexiblen Designs ist der
Algorithmus für breitbandige Empfänger universal einsetzbar und ist nicht
auf Software-konfigurierbare Funkmodule beschränkt.Today's wireless communication systems place high requirements on the
radio's hardware that are largely mutually exclusive, such as low power
consumption, wide bandwidth, and high linearity. Achieving a sufficient
linearity, among other analogue characteristics, is a challenging issue in
practical transceiver design. The focus of this thesis is on wideband
receiver RF front-ends for software defined radio technology, which became
commercially available in the recent years. Practical challenges and
limitations are being revealed in real-world experiments with these radios.
One of the main problems is to ensure a sufficient RF performance of the
front-end over a wide bandwidth. The thesis covers the analysis and
mitigation of receiver non-linearity of typical direct-conversion receiver
architectures, among other RF impairments. The main focus is on DSP-based
algorithms for mitigating non-linearly induced interference, an approach
also known as "Dirty RF" signal processing techniques. The conceived
digital feedforward mitigation algorithm is verified through extensive
simulations, RF measurements, and implementation in real hardware. Various
studies are carried out that bridge the gap between theory and practical
applicability of this approach, especially with the aim of integrating that
technique into real devices. To this end, an advanced baseband behavioural
model is developed that matches to direct-conversion receiver architectures
as close as possible, and thus considers all generated distortions at RF
and baseband. In addition, the algorithm's performance is verified under
challenging fading conditions. Moreover, the thesis presents a
resource-efficient real-time implementation of the proposed solution on an
FPGA. Finally, different use cases are covered in the thesis that includes
spectrum monitoring or sensing, GSM downlink reception, and GSM-based
passive radar. It is shown that non-linear distortions can be successfully
mitigated at system level in the digital domain, thereby decreasing the bit
error rate of distorted modulated signals and reducing the amount of
non-linearly induced interference. Finally, the effective linearity of the
front-end is increased substantially. Thus, the proper operation of a
low-cost radio under presence of receiver non-linearity is possible. Due to
the flexible design, the algorithm is generally applicable for wideband
receivers and is not restricted to software defined radios
Radio Communications
In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modified our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the field of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world. Various aspects will be deeply discussed: channel modeling, beamforming, multiple antennas, cooperative networks, opportunistic scheduling, advanced admission control, handover management, systems performance assessment, routing issues in mobility conditions, localization, web security. Advanced techniques for the radio resource management will be discussed both in single and multiple radio technologies; either in infrastructure, mesh or ad hoc networks
Performance evaluation of a 40 GHz broadband cellular system
Doutoramento em Engenharia ElectrónicaO trabalho apresentado nesta tese enquadra-se na área das comunicações móveis celulares e tem subjacente a utilização de um protótipo de um sistema de comunicações móveis de banda larga desenvolvido no âmbito do projecto Europeu SAMBA. Este protótipo apresenta como principais características inovadoras as taxas de transmissão, a frequência de operação, a mobilidade e os protocolos de handover rádio. Inicialmente são descritos aspectos relacionados com a evolução das comunicações móveis ao longo do tempo e apresentados conceitos teóricos fundamentais para compreender o comportamento do canal rádio móvel e os mecanismos de propagação. São identificados os tipos de desvanecimento e descritos os vários parâmetros que permitem caracterizar o canal rádio. A descrição do impacto do desvanecimento e as formas de o mitigar são apresentadas para contextualizar o trabalho desenvolvido em termos da especificação do protótipo e as opções escolhidas. As características globais do protótipo são apresentadas o que inclui a descrição do interface rádio, da arquitectura, dos módulos de RF, dos módulos de processamento de banda base, protocolos e algoritmo de transferência rádio. O protótipo foi avaliado em vários cenários com diferentes características. No cenário exterior foi analisada uma rua urbana típica do tipo canyon. Em termos de configuração do sistema foram consideradas e analisadas várias alturas da Estação Base, anglos de inclinação das antenas, várias velocidades da Terminal Móvel, operação com e sem linha de vista e a penetração do sinal rádio em ruas transversais. No cenário interior foram realizados testes similares e medidas relativas às transferências que só foram executadas para este cenário por questões logísticas. Numa primeira abordagem foi analisada a cobertura oferecida por cada célula e posteriormente activada a funcionalidade de transferência. Foram também efectuados estudos com uma única Estação Base cobrindo toda a área. Em termos de caracterização do canal rádio em banda larga são apresentadas medidas da resposta impulsiva para dois cenários interiores e complementados por outros estudos via simulação utilizando uma ferramenta de ray tracing. Nas medidas foi utilizado um método de medição do canal no domínio da frequência. A relação entre o Espalhamento do Atraso e a Banda de Coerência em diferentes cenários foi analisada em detalhe e feita a verificação em termos da violação do limite teórico de Fleury. Como consequência dos tópicos abordados, esta tese apresenta um estudo abrangente de aspectos relacionados com o comportamento do canal rádio na faixa dos 40 GHz e a análise das opções técnicas do protótipo em termos do seu desempenho no âmbito dos sistemas de comunicações móveis 4G.The work presented in this thesis addresses the area of mobile cellular broadband communications and encompasses the utilization of a prototype developed in the framework of the European project SAMBA. This prototype has as main innovative characteristics the transmission rates, the frequency band of operation, the mobility and the radio handover protocols. Initially are described aspects related with the historical evolution of the mobile communications and presented fundamental theoretical concepts to understand the behaviour of the radio channel and the propagation mechanisms. The different types of fading are identified as well as the various parameters that allow the characterisation of the radio channel. The fading impact and its mitigation techniques are presented to contextualise the work developed in terms of the specification of the features implemented in the prototype and the options available. The global characteristic of the prototype are presented namely the radio interface, the architecture, the RF modules, the baseband modules, protocols and the algorithm for the radio handover. The prototype was evaluated in various scenarios with different characteristics. In the outdoor scenario a canyon type street was analysed. Several heights of the Base Station, antenna tilting angles, Mobile Terminal velocities, operation in line-of-sight and non line-of-sight and the penetration of the signal in a transversal street. In the indoor scenario similar measurements were performed. The handover feature was analysed just for this scenario due to logistic reasons. In a first phase the coverage provided by each Base Station was analysed and subsequently activated the handover functionality. Studies using a single Base Station to cover the whole pavilion were also performed. In terms of broadband analysis, channel impulse response measurements were performed using a frequency domain technique in two scenarios and complemented by others analysed only using a ray tracing simulation tool. The relationship between the radio channel Delay Spread and the Coherence Bandwidth was analysed in different scenarios and the possible violation of the Fleury lower bond checked. As a consequence of the several topics covered in this thesis, a deep study of the aspects related with the behaviour of the radio channel in the 40 GHz band and the performance of the technical options implemented in the prototype is presented in the framework of 4G mobile communication systems
Intelligent Circuits and Systems
ICICS-2020 is the third conference initiated by the School of Electronics and Electrical Engineering at Lovely Professional University that explored recent innovations of researchers working for the development of smart and green technologies in the fields of Energy, Electronics, Communications, Computers, and Control. ICICS provides innovators to identify new opportunities for the social and economic benefits of society. This conference bridges the gap between academics and R&D institutions, social visionaries, and experts from all strata of society to present their ongoing research activities and foster research relations between them. It provides opportunities for the exchange of new ideas, applications, and experiences in the field of smart technologies and finding global partners for future collaboration. The ICICS-2020 was conducted in two broad categories, Intelligent Circuits & Intelligent Systems and Emerging Technologies in Electrical Engineering