Cooperative traffic safety applications such as lane change or overtaking assistance have the potential to reduce the number of road fatalities. Many emerging traffic safety applications are based on IEEE 802.11p and periodic position messages, so-called cooperative awareness messages (CAM) being broadcasted by all vehicles. In Europe, ETSI defines a periodic report rate of 2 Hz for CAMs. Although a high report rate is the key to early hazard detection, the 2 Hz rate has been chosen to avoid congestion in settings where the vehicle density is high, e.g., on major highways and in urban scenarios. However, on rural roads with a limited number of communicating vehicles, a report rate of 2 Hz leads to unnecessary delay in cooperative awareness. By adapting the CAM report rate depending on the specific application and road traffic density, and by making use of the priority levels provided by the 802.11p quality of service mechanism, we show that hazards can be detected earlier and the available bandwidth is used more efficiently, while not overexploiting the network resources. / <p>©2011 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.</p><p></p><p>Category number CFP11VTF-ART; Code 87844</p>

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It is often necessary to operate a number of radio communication channels from a single control room without time-sharing between the various channels. Here it is necessary to operate a number of transmitters and receivers simultaneously from the same base station or mobile unit without interference. The best method to achieve this has been found in the use of filters inserted in the transmission line between the antenna and the transmitter(s) on one hand and the receiver(s) on the other hand. The basic unit employed in the design of microwave filters is usually a cavity resonator of which the most important factors are the Q, insertion loss and resonant frequency. However, a problem which frequently arises with cavity resonators is the accurate determination of these resonant characteristics complicated by the presence of coupling port, materials and various design and geometrical deviations. Such cavities have been investigated in several cases and the results have been generalised, but this investigation has been conducted to examine thoroughly most of the problems being met in present practice. Design and development of some common resonant structures are considered. Emphasis is placed on solutions found to special problems especially regarding complicated boundary conditions. Furthermore, investigation includes methods for optimising resonant parameters such as insertion loss and Q, trading of insertion loss with coupled cavity selectivity, frequency tuning and compensation for frequency variations due to wide ranges of operating temperatures. By comparing Q values obtained in practice with theoretical values, it has been possible to establish an appropriate Q loss budget to as to facilitate accurate prediction of coupled cavity unloaded Q. A satisfactory agreement between theory and practice has been obtained. By application of the results of theoretical analysis and experiment, it is shown that microwave filters can be designed to have a desired insertion loss and off-band attenuation slope. Steps leading to designs of any number of cascaded cavities in a two-port network and, subsequently, multi-port networks are discussed in detail.

Avec la multiplication des terminaux mobiles et le foisonnement des objets dits « connectés », on assiste à la montée d'un besoin de moyens de communication à tout endroit et en toute situation, accompagné d'un encombrement spectral toujours plus important. Dans ce contexte, si la capacité d'adaptation au canal des modulations multiporteuses permet de bien s'accommoder du besoin de communication en tout endroit, les techniques actuelles, en particulier l'OFDM, souffrent d'une mauvaise localisation fréquentielle et d'un mauvais facteur de crête, ce qui limite leur utilisation dans un contexte embarqué et/ou en présence de fortes contraintes spectrales. Dans cette thèse, nous étudions les modulations multiporteuses au-delà de la cadence de Nyquist. En augmentant la densité de signalisation, ces dernières permettent d'augmenter l'efficacité spectrale. Cela est cependant contrebalancé par l'apparition d'auto-interférence, ce qui rend la réception plus délicate.Sur canal à bruit additif blanc gaussien, on montre comment choisir des impulsions de mise en forme maximisant le rapport signal à interférence plus bruit. On montre que ces dernières permettent d'obtenir une turbo-égalisation linéaire de l'auto-interférence minimisant l'erreur quadratique moyenne. Nos travaux mettent en évidence que ces mêmes impulsions permettent également de réduire le facteur de crête à mesure que la densité augmente. Enfin, sur canal sélectif en fréquence, on vérifie que l'approximation du canal par un coefficient par sous-porteuse est toujours possible. Ces résultats montrent que ce nouveau type de modulation permet d'augmenter l'efficacité spectrale tout en conservant la capacité d'adaptation au canal intrinsèque aux modulations multiporteuses. / With an increasing number of mobile terminals coupled with a large spreading of so-called "smart devices", we can see a growing demand for effective communication means in any place and in any situation.This goes with a more and more overcrowded spectrum.In this context, multicarrier modulations are good candidates to allow effective communication in any place.However current techniques, OFDM in particular, suffer from a bad time--frequency localization and peak-to-average power ratio, limiting their relevancy in an embedded context, or in scenarios with severe spectral constraints.In this thesis, we study faster-than-Nyquist multicarrier modulations.This kind of modulation allow for an increase in spectral efficiency by means of an increase in signaling density.This, in compensation, comes at the price of unavoidable self-interference, which makes demodulation harder.On an additive white Gaussian noise channel, we show how to carefully chose pulse-shapes that maximize signal-to-interference-plus-noise ratio.We show that these particular pulse-shapes yields a linear turbo-equalization of self-interference minimizing the mean squared error.Next, our work highlights the capability of these optimal pulse-shapes to reduce peak-to-average power ratio as density rises.Lastly, on frequency selective channels, we confirm that low complexity equalization using one tap by subcarrier is still possible.These results show how this new modulation technique helps increasing spectral efficiency while keeping what made multicarrier modulations popular: good adaptation to transmission channels.

Orientador: Kamal Abdel Radi Ismail / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-04T07:17:14Z (GMT). No. of bitstreams: 1 Goulart_MarceloMagalhaes_M.pdf: 9682705 bytes, checksum: cef6e14e1c5be1d97e9dd8d289828945 (MD5) Previous issue date: 2005 / Resumo: A partir dos meados dos anos 90, com o surgimento da telefonia celular analógica e posteriormente digital, o número de usuários da telefonia celular aumenta vertiginosamente e em 2004 já supera no Brasil o número de telefones fixos, 54 milhões de celulares e 49 milhões de telefones fixos (Dados Teleco de Junho/2004). Este trabalho descreve de uma forma geral a proposta do desenvolvimento de um protótipo elétrico/eletrônico e mecânico de um sistema de monitoração e controle de inclinação (Tilt) e coordenação (Azimute) das antenas das estações rádio base da telefonia celular, facilitando-se desta forma enormemente a otimização da infra-estrutura já existente das operadoras de telefones portáteis. O estudo se baseia na utilização de microcontroladores para a realização de controle e monitoração dos sensores de inclinação e azimute instalados na simulação de uma estrutura de torre de uma estação rádio base (ERB) / Abstract: Starting from the middles of the nineties, with the appearance of the analogical mobile telephone and later digital, the number of users of the cellular mobile telephone increases vastly and in 2004 it already overcomes in Brazil the number of fixed telephones, 54 million of cellular mobile telephone and 49 million telephones fixed (Data from Teleco jun/2004).This work describe the proposal of the development of a prototype electric/electronic and mechanic of a monitoring and control system of inclination (Tilt) and coordination (Azimuth) of the antennas of the stations radio-base of the mobile telephone, being facilitated this way vastly the optimization of the infrastructure already existent of the operators of telephones mobile. The study if it bases on the microcontrollers use for accomplishment of control and monitoring of the sensor of inclination and azimuth installed in the simulation of a structure of tower of a station radio base (ERB) / Mestrado / Instrumentação e Controle Industrial / Mestre Profissional em Engenharia Mecanica

[pt] Nesta dissertação, é apresentado estudo realizado sobre a variabilidade do sinal, da banda de coerência e do espalhamento de retardos em um ambiente de rádio propagação móvel, por meio de medição em campo de um sinal WiMAX propagado ao longo do canal rádio móvel. A análise da estatística do sinal capturado é comparada com valores teóricos. O sinal WiMAX utilizado possui a tecnologia OFDM-256, como base da sua camada física, e frequência central de 3,410 GHz. A partir dos dados coletados durante as medições, são realizadas as análises da variabilidade do sinal, taxa de cruzamento de nível, tempo médio de desvanecimento, verificada a banda de coerência do canal e calculado o espalhamento de retardos (delay spread), por meio de fórmulas teóricas, em ambientes de LOS e NLOS. O nível do sinal medido é apresentado na forma de distribuição de probabilidade cumulativa, comparado com as distribuições cumulativas teóricas Rayleigh e m-Nakagami, sendo possível verificar a satisfatória adaptação dos dados às distribuições teóricas. São apresentados gráficos com a informação de taxa de cruzamento de nível e tempo médio de desvanecimento de determinadas subportadoras do sinal capturado, bem como os valores teóricos dos parâmetros supracitados, de acordo com as distribuições Rayleigh e m-Nakagami. Novamente, é possível verificar a satisfatória adaptação entre as informações teóricas e os dados medidos em campo. Por fim, é realizada a correlação entre as subportadoras, com o intuito de averiguar a banda de coerência definida, neste trabalho, para um valor de correlação igual a 0,5. De posse dessa informação, o cálculo do parâmetro de espalhamento de retardos é realizado, com base em fórmulas presentes na literatura. / [en] This work presents a study of signal variability, coherence bandwidth and delay spread of a WiMAX signal transmitted through a mobile radio propagation environment. The statistical analysis of the received signal is compared with theoretical distributions. The transmitted WiMAX signal has its physical layer based on OFDM-256 and 3.4 GHz as central frequency. Based on the signal received during the measurements campaign some analysis are done: signal variability; level crossing rate; average fade duration; coherence bandwidth; and delay spread calculation, based on theoretical formulas, in LOS and NLOS environment. The received signal amplitude is plotted as a function of the cumulative probability and compared to the theoretical Rayleigh and m-Nakagami cumulative distributions. It’s possible to notice a good characterization of the measured data based on those two distributions. Some graphs show the level crossing rate and average fade duration of a specific subcarrier of the received signal. In the same graphs are also plotted the theoretical values of Nakagami-m and Rayleigh distributions for those two parameters and we are able to see the good agreement. The correlation between subcarriers is also calculated in order to find out the correlation bandwidth for a correlation of 0.5. Once that the correlation bandwidth is known, the delay spread is calculated based on theoretical formulas.

It is often necessary to operate a number of radio communication channels from a single control room without time-sharing between the various channels. Here it is necessary to operate a number of transmitters and receivers simultaneously from the same base station or mobile unit without interference. The best method to achieve this has been found in the use of filters inserted in the transmission line between the antenna and the transmitter(s) on one hand and the receiver(s) on the other hand. The basic unit employed in the design of microwave filters is usually a cavity resonator of which the most important factors are the Q, insertion loss and resonant frequency. However, a problem which frequently arises with cavity resonators is the accurate determination of these resonant characteristics complicated by the presence of coupling port, materials and various design and geometrical deviations. Such cavities have been investigated in several cases and the results have been generalised, but this investigation has been conducted to examine thoroughly most of the problems being met in present practice. Design and development of some common resonant structures are considered. Emphasis is placed on solutions found to special problems especially regarding complicated boundary conditions. Furthermore, investigation includes methods for optimising resonant parameters such as insertion loss and Q, trading of insertion loss with coupled cavity selectivity, frequency tuning and compensation for frequency variations due to wide ranges of operating temperatures. By comparing Q values obtained in practice with theoretical values, it has been possible to establish an appropriate Q loss budget to as to facilitate accurate prediction of coupled cavity unloaded Q. A satisfactory agreement between theory and practice has been obtained. By application of the results of theoretical analysis and experiment, it is shown that microwave filters can be designed to have a desired insertion loss and off-band attenuation slope. Steps leading to designs of any number of cascaded cavities in a two-port network and, subsequently, multi-port networks are discussed in detail.

Parallel interference cancellation for DS-CDMA has been shown to suffer from biased amplitude estimates if a matched-filter estimator is used. The bias magnitude is proportional to the number of interfering users. For heavy system loads, the bias has been shown to adversely effect the accuracy of the interference cancellation process, thereby impairing BER after cancellation. Empirical simulation work has demonstrated that weighting down interference estimates can improve BER performance. This thesis substantiates these BER improvements by modelling and analyzing a soft interference cancellation technique which mitigates the effects of the bias by minimizing BER after cancellation in a bit-synchronous parallel interference cancellation CDMA receiver. We analyze system decision metrics with down-scaled interference estimates and determine both the mean and variance of the biased decision statistics. From these two metric moments, system BER is evaluated, and the optimal interference scaling function which minimizes BER is derived. We demonstrate BER performance enhancements by simulating this soft interference cancellation technique in systems under perfect power control and in the near-far situation. We further discuss the applicability of the results to asynchronous systems. / Master of Science

In Code Division Multiple Access (CDMA) systems forward error correction (FEC) is an important factor in improving system performance. Because of the multiple access interference observed in asynchronous CDMA, FEC is required to improve system capacity. Several alternative coding techniques are available, including "trellis codes" specifically designed for CDMA, very low rate convolutional codes and conventional convolutional codes. An analytic approach is developed to compare the performance of different coding techniques for CDMA on the same basis by extending several improved analysis techniques which were developed for uncoded CDMA. Analytic results are presented for additive white Gaussian noise (AWGN) channels and frequency non-selective Rician Fading (FNRF) channels. The performance of coded CDMA systems in frequency selective Rayleigh fading channels is also analyzed using simulation techniques. Both analytic and simulation results show that by using trellis codes or very low rate convolutional codes significant performance improvement is achieved over conventional convolutional codes. Trellis codes outperform very low rate convolutional codes in AWGN and FNRF channels while both codes show similar performance in frequency selective Rayleigh fading channels. / Master of Science

Yes / The potentially broad application area in engineering design using Genetic Algorithm (GA) has been widely adopted by many researchers due to its high consistency and accuracy. Presented here is the initial design of a wideband non-dispersive wire bow-tie antenna using GA for breast cancer detection applications. The ultimate goal of this design is to achieve minimal late-time ringing but at higher frequencies such as that located from 4 to 8 GHz, in which is desire to penetrate human tissue for near field imaging. Resistively loading method to reduce minimal ringing caused by the antenna internal reflections is implemented and discussed when the antenna is located in free space and surrounded by lossy medium. Results with optimised antenna geometry and different number of resistive loads are presented and compared with and without existence of scatterers.