Tese de doutoramento. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 2009

ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, California / This paper describes the use of orthogonal space-time block codes to overcome the performance and complexity difficulties associated with the use of Shaped Offset QPSK (SOQPSK) modulation, a ternary continuous phase modulation (CPM), in multiple-input multiple-output telemetry systems. The orthogonal space-time block code is applied to SOQPSK waveforms in the same way it would be applied to symbols. The procedure allows the receiver to orthogonalize the link. The main benefits of this orthogonalization are the easy realization of the transmit diversity for the offset-featured SQOSPK, and the removal of the noise correlation at the input to the space-time decoder and the elimination of I/Q interference when space time orthogonalization is applied to the symbol level.

ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / The accuracy of channel estimation plays a crucial role in the demodulation of data symbols sent across an unknown wireless medium. In this work a new analytical expression for the channel estimation error of a multiple input multiple output (MIMO) system is obtained when the wireless medium is continuously changing in the temporal domain. Numerical examples are provided to illustrate our findings. Space-time (ST) coding using Continuous Phase Modulation (CPM) has spectral advantages relative to linear modulations. In spite of the spectral benefits, Space-Time Trellis Codes (STTC) using the CPM implementation of Minimum Shift Keying (MSK) scheme has inherent inphase and quadrature interference, when the received complex baseband signal is the input into the matchfilter to remove the shaped sinusoid pulses. In this paper a novel optimum transmitting and detecting structure for STTC-MSK is proposed. Treating the Alamouti scheme as an outer code, each STTC MSK waveform frame is immediately followed by the orthogonal conjugate waveform frame at the transmit side. At the receiver first orthogonal wave forming is applied, then a new time-variant yet simple trellis structure of the STTC-MSK signals is developed. This STTC-MSK detector is absolutely guaranteed to be I/Q interference-free and still keeps a smaller computation load compared with STTC-QPSK. Simulations are made over quasi-static AWGN fading channel. It is shown that our detector for ST-MSK has solved the I/Q interference problem and has around 2.8 dB gain compared with the Alamouti Scheme and 3.8 dB gain for bit error rate at 5 X 10^(-3) in a 2 by 1 Multiple Input Single Output system.

Spatial Modulation (SM) is a Multiple-Input Multiple-Output (MIMO) transmission technique which realizes low complexity implementations in wireless communication systems. Due the transmission principle of SM, only one Radio Frequency (RF) chain is required in the transmitter. Therefore, the complexity of the transmitter is lower compared to the complexity of traditional MIMO schemes, such as Spatial MultipleXing (SMX). In addition, because of the single RF chain configuration of SM, only one Power Amplifier (PA) is required in the transmitter. Hence, SM has the potential to exhibit significant Energy Efficiency (EE) benefits. At the receiver side, due to the SM transmission mechanism, detection is conducted using a low complexity (single stream) Maximum Likelihood (ML) detector. However, despite the use of a single stream detector, SM achieves a multiplexing gain. A point-to-point closed-loop variant of SM is receive space modulation. In receive space modulation, the concept of SMis extended at the receiver side, using linear precoding with Channel State Information at the Transmitter (CSIT). Even though receive space modulation does not preserve the single RF chain configuration of SM, due to the deployed linear precoding, it can be efficiently incorporated in a Space Division Multiple Access (SDMA) or in a Virtual Multiple-Input Multiple-Output (VMIMO) architecture. Inspired by the potentials of SM, the objectives of this thesis are the evaluation of the EE of SM and its extension in different forms of MIMO communication. In particular, a realistic power model for the power consumption of a Base Station (BS) is deployed in order to assess the EE of SM in terms of Mbps/J. By taking into account the whole power supply of a BS and considering a Time Division Multiple Access (TDMA) multiple access scheme, it is shown that SM is significantly more energy efficient compared to the traditional MIMO techniques. In the considered system setup, it is shown that SM is up to 67% more energy efficient compared to the benchmark systems. In addition, the concept of space modulation is researched at the receiver side. Specifically, based on the union bound technique, a framework for the evaluation of the Average Bit Error Probability (ABEP), diversity order, and coding gain of receive space modulation is developed. Because receive space modulation deploys linear precoding with CSIT, two new precoding methods which utilize imperfect CSIT are proposed. Furthermore, in this thesis, receive space modulation is incorporated in the broadcast channel. The derivation of the theoretical ABEP, diversity order, and coding gain of the new broadcast scheme is provided. It is concluded that receive space modulation is able to outperform the corresponding traditional MIMO scheme. Finally, SM, receive space modulation, and relaying are combined in order to form a novel virtual MIMO architecture. It is shown that the new architecture practically eliminates or reduces the problem of the inefficient relaying of the uncoordinated virtual MIMO space modulation architectures. This is undertaken by using precoding in a novel fashion. The evaluation of the new architecture is conducted using simulation and theoretical results.

Next generation wireless communications require transmission of reliable high data rate services. Second generation wireless communications systems use single-input multiple-output (SIMO) channel in the reverse link, meaning one transmit antenna at the user terminal and multiple receive antennas at the base station. Recently, information theoretic research has shown an enormous potential growth in the capacity of wireless systems by using multiple antenna arrays at both ends of the link. Space-time coding exploits the spatial-temporal diversity provided by the multiple input multiple output (MIMO) channels, significantly increasing both system capacity and the reliability of the wireless link. The Virginia Tech Space-Time Advanced Radio (VT-STAR) system presents a test bed to demonstrate the capabilities of space-time coding techniques in real-time. Core algorithms are implemented on Texas Instruments TMS320C67 Evaluation Modules (EVM). The radio frequency subsystem is composed of multi-channel transmitter and receiver chains implemented in hardware for over the air transmission. The capabilities of the MIMO channel are demonstrated in a non-line of sight (NLOS) indoor environment. Also to characterize the capacity gains in an indoor environment this test bed was modified to take channel measurements. This thesis reports the system design of VT-STAR and the channel capacity gains observed in an indoor environment for MIMO channels. / Master of Science

Made available in DSpace on 2016-03-15T19:37:56Z (GMT). No. of bitstreams: 1 BRUNO FERRAZ IZARIO.pdf: 4620887 bytes, checksum: bd842cabfdadb0bcb55e0ea548c9fba5 (MD5) Previous issue date: 2015-08-28 / The Long Term Evolution (LTE) system belongs to the 4th generation phone system. It is standardized by 3GPP and utilizes several technologies to improve the performance of data transmission. This permits flexibility for mobile devices, which enables a high data rate in the range of 50 Mbps to 100 Mbps, and admit access to various multimedia services. The study presents the results of deploying an LTE network in the city of Campinas, São Paulo, Brazil, using the 700 MHz band by comparing it to the 2.5 GHz band. By calculating the budget for the LTE system link is information as possible to highlight throughput and cell coverage radius, and other information. The Radio Mobile software was used for verification of results. / O sistema Long Term Evolution (LTE) pertence ao sistema da 4ª geração de telefonia (4G). Ele é padronizado pelo 3GPP e utiliza diversas tecnologias para melhorar o desempenho de transmissão de dados. O mesmo permite uma flexibilidade para dispositivos móveis, possibilitando uma alta taxa de dados na faixa de 50 Mbps a 100 Mbps, além de admitir acesso a diversos serviços multimídias. O estudo apresenta resultados de implantação de uma rede LTE na cidade de Campinas, São Paulo, Brasil, utilizando a faixa de 700 MHz comparando-a com a faixa de 2,5 GHz. Através do cálculo de link budget para o sistema LTE, é possível destacar informações como throughput e raio da célula de cobertura, além de outras informações. O software radio mobile foi utilizado para fins de comprovação de resultados.

In this thesis, the studies mainly focus on recent trends in novel MIMO antennas for indoor wireless communication system. Firstly, we propose a novel MIMO antenna for access-point application. This proposed antenna can reduce the lateral length of the conventional access-point antenna for MIMO application. Then, we present MIMO antenna designs for mobile devices such as PDA phones and laptop computers. Although these two devices are of different configurations, the PIFAs are applicable in these two devices, and their design rules are basically the same. Thus, for this study, the design consideration of the MIMO antenna will focus on S-parameter analysis. Detailed antenna designs and experimental results are presented and discussed in this thesis.

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Dans ce travail de thèse, on s'intéresse é l'emploi de techniques de traitement de signal de systèmes de communication MIMO (Multiple Input Multiple Output) pour des applications aux réseaux de capteurs sans fil. Les contraintes énergétiques de cette classe de réseau font appel à des topologies particulières et le réseau peut être perçu comme étant un ensemble de grappes de nœuds capteurs. Ceci ouvre la porte à des techniques avancées de communication de type MIMO. Dans un premier temps, les différents aspects caractérisant les réseaux de capteurs sans fil sont introduits. Puis, les efforts engagés pour optimiser la conservation de l'énergie dans ces réseaux sont résumés. Les concepts de base de systèmes MIMOs sont abordés dans le deuxième chapitre et l'exploration par voie numérique de différentes pistes de la technologie MIMO sont exposées. Nous nous intéressons à des techniques de diversité de polarisation dans le cadre de milieux de communication riches en diffuseurs. Par la suite, des méthodes de type beamforming sont proposées pour la localisation dans les réseaux de capteurs sans fil. Le nouvel algorithme de localisation est présenté et les performances sont évaluées. Nous identifions la configuration pour la communication inter-grappes qui permet pour les meilleurs compromis entre énergie et efficacité spectrale dans les réseaux de capteurs sans fil. Finalement, nous envisageons la technique de sélection de nœuds capteurs afin de réduire la consommation de l'énergie dans le réseau de capteur sans fil. / The aim of this work is to study from a signal processing point of view the use of MIMO (Multiple Input Multiple Output) communication systems for algorithms dedicated to wireless sensor networks. We investigate energy-constrained wireless sensor networks and we focus on cluster topology of the network. This topology permits for the use of MIMO communication system model. First, we review different aspects that characterize the wireless sensor network. Then, we introduce the existing strategies for energy conservation in the network. The basic concepts of MIMO systems are presented in the second chapter and numerical results are provided for evaluating the performances of MIMO techniques. Of particular interest, polarization diversity over rich scattering environment is studied. Thereafter, beamforming approach is proposed for the development of an original localization algorithm in wireless sensor network. The novel algorithm is described and performances are evaluated by simulation. We determine the optimal system configuration between a pair of clusters that permits for the highest capacity to energy ratio in the fourth chapter. The final chapter is devoted to sensor nodes selection in wireless sensor network. The aim of using such technique is to make energy conservation in the network.