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This report focuses on the application of adaptive arrays to the Advanced Mobile Phone Service (AMPS) and Code Division Multiple Access (CDMA) cellular systems. Adaptive arrays have been proposed as early as in the 1960s to improve the signal quality, but most of its applications were restricted to defense purposes. Recently, there has been a surge in interest of applying adaptive arrays for cellular systems. This work introduces new blind adaptive array algorithms for AMPS and CDMA signals. The theoretical capacity limit using an adaptive array at the base station for an AMPS cellular system is derived in this work. One of the significant contributions in this research is a macrocell channel model which provides angle-of-arrival (AOA) statistics of the multipath components. Practical issues involved in the implementation of an adaptive array are addressed and the author's implementation of an 8-element adaptive array operating at 2.05 GHz is explained. This research also analyzes the capacity that can be o ered by an adaptive array in a system where CDMA users co-exist with existing AMPS users. A novel cellular CDMA system which exploits adaptive arrays is introduced and the capacity o ered by this system is compared with existing and other systems exploiting spatial dimension. / Ph. D.

There has been great interest in antenna array processing (diversity, beamforming, null steering, and spatial multiplexing) to enhance the received signal quality and the capacity of wireless communications systems. However, in order to properly exploit the characteristics of different array processing techniques, understanding trade-offs among different techniques and parametric investigation, which offers an insight as to what parameters determine system performance under different situations is necessary. In this study, we present analytical framework which can facilitate the performance analysis of systems with antenna array. Five original contributions to the performance analysis of antenna array processing are presented in this study. First, we present theoretical outage probability of a system equipped with an array which suppresses a few dominant interering signals in TDMA cellular networks when the fading statistics of interfering signals are independent but non-identically distributed. Most of the related previous works assumed either independent and identically distributed fading statistics among cochannel interferences (CCI) or Rayleigh fading when CCI signals are subject to i.n.d. fading statistics. Secondly, the performance of multi-branch predetection equal gain combiner for different modulation techniques in equally correlated Nakagami-m fading is presented through analytical analysis. Specifically, the characteristic function (CHF) and the moment generating function (MGF) of EGC output with correlated inputs are derived and used to evaluate the average symbol error probability (ASEP) and the outage probability performance, respectively. Thirdly, we derived analytical expression which can be used to analyze the performance of different types of diversity techniques in equally correlated Nakagami-m or Rice fading channels. Fourthly, asymptotic analysis on different types of diversity combiners in generalized fading channels is presented in a unifying way. Finally, we investigate and present the impact of transmit diversity at handsets on the reverse link DS/CDMA systems in terms of capacity and coverage over generalized fading channels through analytical approaches. Then, we validate the analytical results with simulation results and investigate practical issues which are hard to capture through analytical analysis using system level simulator we developed. Although we have mainly focused on applying the analytical framework we have derived in this work to the performance analysis of physical layer algorithms such as spatial diversity and adaptive null steering, the framework can be extended to assist the analysis and design of wireless communication systems such as, to name a few, distributed multiple input multiple output (MIMO) system in cooperative wireless networks, multipath routing protocol analysis in wireless fading channels, and antenna selection problems in MIMO system. / Ph. D.

The increasing demand for mobile communication services without a corresponding increase in RF spectrum allocation motivates the need for new techniques to improve spectrum utilization. The CDMA and adaptive antenna array are two approaches that shows real promise for increasing spectrum efficiency. In this research, we investigate the performance of different blind adaptive array algorithms in the CDMA systems. Two novel algorithms, least-squares despread respread multitarget array (LS-DRMTA) and least-squares despread respread multitarget constant modulus algorithm (LS-DRMTCMA), are developed, and a MATLAB simulation testbed is created to compare the performance of these two novel algorithms with those of the multitarget least-squares constant modulus algorithm (MT-LSCMA) and multitarget steepest-descent decision-directed (MT-SDDD) algorithm. It is shown from the simulation results that these two novel algorithms can outperform the other algorithms in all the test situations (e.g., AWGN channel, timing offset case, frequency offset case, and multipath environment). It is also shown that these two algorithms have less complexity and can converge faster than the other algorithms. / Master of Science

Orthogonal Frequency Division Multiplexing (OFDM) has recently gained a lot of attention and is a potential candidate for Fourth Generation (4G) wireless systems because it promises data rates up to 10Mbps. A variation of OFDM is Multi-Carrier CDMA (MC-CDMA) which is an OFDM technique where the individual data symbols are spread using a spreading code in the frequency domain. The spreading code associated with MC-CDMA provides multiple access technique as well as interference suppression. Often times in cellular and military environments the desired signal can be buried below interference. In such conditions, the processing gain associated with the spreading cannot provide the needed interference suppression. This research work investigates multi-antenna receivers for OFDM and MC-CDMA systems; specifically this works investigates adaptive antenna algorithms for MC-CDMA for very different channel conditions. Frequency domain beamforming is studied in this research predominantly through simulation. As an alternative a time domain beamforming is also studied. Time variations in the channel can disrupt the orthogonality between subcarriers. Minimum Mean Square Error (MMSE) detection coupled with MMSE beamforming is proposed for time varying channels. Semi-analytic results are derived to study the Bit Error Rate (BER) performance. These results show significant performance improvement in the presence of interference. Joint MMSE weights in space and frequency is also investigated and semi-analytic results are derived to study their BER performance. / Master of Science

Third generation (3G) mobile communication systems will provide services supporting high-speed data network and multimedia applications in addition to voice applications. The Smart antenna technique is one of the leading technologies that helps to meet the requirement by such services to radio network capacity. Resource management schemes such as power control, handoff and channel reservation/assignment are also essential for providing the seamless services with high quality. Smart antenna techniques will help to enhance the capability of resource management through more efficient and flexible use of resources. In this thesis, adaptive array and switched beam antenna techniques are compared in terms of algorithm, performance, complexity and hardware requirements. Based on these comparisons, sub-optimal code gate algorithm are most likely the suitable algorithms for next generation code division multiple access (CDMA) systems due to its good performances, robustness, and low complexity. A multi-cell CDMA simulator is developed for investigating the gain from smart antenna techniques in both bit error rate (BER) performance improvement and enhancement to resource management schemes. Our study shows that smart antenna techniques can significantly improve the performance of the system and help to build more powerful and flexible resource management schemes. With eight array elements, the system capacity can be increased by a factor of four. Power control command rates can be reduced through the tradeoff with the interference reduction by smart antennas. Smart antennas will also reduce handover failure rates and further increase the system capacity by reducing the resources reserved for soft handover. / Master of Science

During the last decade, the wireless communications industry has grown rapidly. Driven by market demand, service providers are continuously looking for better systems. The main focus of continued research has been to increase the quality of services and system capacity. The Code Division Multiple Access (CDMA) cellular system had been proposed for use as a new standard for cellular telephone systems. A great deal of research has been conducted to develop receiver structures useful for CDMA systems. Traditional receivers such as the correlation and RAKE receivers are vulnerable to the near-far problem, i.e., the problem encountered when one received signal power is stronger than another. This problem is common in mobile environments. For single-user receivers, adaptive filtering techniques can be employed to alleviate multiple access interference and the near-far problem. In this thesis, an adaptive filter receiver is implemented on the FPGA-based configurable computing platform called GigaOps G900. By using FPGAs, designers can implement special-purpose signal processing architectures using specialized data paths, optimized sequencing, and pipelining while still providing some flexibility. This results in better overall system performance, resource utilization, and reduced power consumption. / Master of Science

Esse trabalho de investigação visa a realização de uma análise sistemática, integrada e iterativa da utilização de algoritmos heurísticos aplicados aos problemas de estimativa de parâmetros e detecção multiusuário, sob o ponto de vista do compromisso desempenho × complexidade. O sistema considera topologias do tipo CDMA com exploração de diversidade multidimensional, ou seja, que utilizam uma ou mais técnicas de diversidade, considerando a diversidade de código, tempo, frequência e espaço, entre outras, sujeitos a desvanecimentos multipercurso. A solução integrada para os problemas de estimativa de parâmetros e detecção multiusuário consiste no uso recorrente de técnicas heurísticas. Além disso, estabelece-se uma análise comparada e sistêmica de convergência e de complexidade computacional da técnica de detecção proposta com alguns outros métodos, heurísticos ou determinísticos, relatados na literatura, considerando como métrica de desempenho o número de operações computacionais que cada estratégia requer para a detecção simultânea da informação de todos os usuários ativos no sistema. Por fim, e mais importante, considera-se como a principal contribuição deste trabalho a sistematização da utilização dos algoritmos heurísticos no processo de otimização dos problemas já citados, caracterização de limiares de desempenho e análise de complexidade destas técnicas, trazendo à comunidade científica parâmetros suficientes que devem ser respeitados na configuração dos algoritmos para garantia de resultados satisfatórios quando da utilização destes métodos em problemas de detecção multiusuário com diversidade multidimensional e estimativa de parâmetros. / This work will perform a systematic, integrated and iterative research of heuristic algorithms applied to parameter estimation and multiuser detection problems, considering the performance × complexity tradeoff. The CDMA systems with multidimensional diversity exploitation, i.e., with one or more diversity techniques, code diversity, frequency, time and space, among other, in multipath fading channel scenarios are considered. The integrated solution for parameter estimation and multiuser detection problem uses heuristic techniques in recurrent form. In addition, we intend to establish a systemic and comparative analysis of convergence and computational complexity of the proposal detection technique with some other methods, heuristic or deterministic, reported in the literature, considering the number of computational operations that each strategy requires for simultaneous detection from all active users as a performance metrics. Finally, and most importantly, this work systematizes the heuristic algorithms approach in the optimization problems process already mentioned, considering the thresholds for performance and complexity of these techniques, bringing the scientific community enough configuration parameters that must be respected in the setup algorithms step to guarantee satisfactory results when using these methods to multiuser detection with multidimensional diversity and parameter estimation problems.

Esse trabalho de investigação visa a realização de uma análise sistemática, integrada e iterativa da utilização de algoritmos heurísticos aplicados aos problemas de estimativa de parâmetros e detecção multiusuário, sob o ponto de vista do compromisso desempenho × complexidade. O sistema considera topologias do tipo CDMA com exploração de diversidade multidimensional, ou seja, que utilizam uma ou mais técnicas de diversidade, considerando a diversidade de código, tempo, frequência e espaço, entre outras, sujeitos a desvanecimentos multipercurso. A solução integrada para os problemas de estimativa de parâmetros e detecção multiusuário consiste no uso recorrente de técnicas heurísticas. Além disso, estabelece-se uma análise comparada e sistêmica de convergência e de complexidade computacional da técnica de detecção proposta com alguns outros métodos, heurísticos ou determinísticos, relatados na literatura, considerando como métrica de desempenho o número de operações computacionais que cada estratégia requer para a detecção simultânea da informação de todos os usuários ativos no sistema. Por fim, e mais importante, considera-se como a principal contribuição deste trabalho a sistematização da utilização dos algoritmos heurísticos no processo de otimização dos problemas já citados, caracterização de limiares de desempenho e análise de complexidade destas técnicas, trazendo à comunidade científica parâmetros suficientes que devem ser respeitados na configuração dos algoritmos para garantia de resultados satisfatórios quando da utilização destes métodos em problemas de detecção multiusuário com diversidade multidimensional e estimativa de parâmetros. / This work will perform a systematic, integrated and iterative research of heuristic algorithms applied to parameter estimation and multiuser detection problems, considering the performance × complexity tradeoff. The CDMA systems with multidimensional diversity exploitation, i.e., with one or more diversity techniques, code diversity, frequency, time and space, among other, in multipath fading channel scenarios are considered. The integrated solution for parameter estimation and multiuser detection problem uses heuristic techniques in recurrent form. In addition, we intend to establish a systemic and comparative analysis of convergence and computational complexity of the proposal detection technique with some other methods, heuristic or deterministic, reported in the literature, considering the number of computational operations that each strategy requires for simultaneous detection from all active users as a performance metrics. Finally, and most importantly, this work systematizes the heuristic algorithms approach in the optimization problems process already mentioned, considering the thresholds for performance and complexity of these techniques, bringing the scientific community enough configuration parameters that must be respected in the setup algorithms step to guarantee satisfactory results when using these methods to multiuser detection with multidimensional diversity and parameter estimation problems.

A dinâmica de sistemas caóticos é uma área de pesquisa relativamente recente, diretamente relacionada com os campos da engenharia, física e matemática aplicada. A sincronização entre sistemas dinâmicos tem sido um tópico de pesquisa muito freqüente, abrangendo campos desde a mecânica de corpos celestiais até a física dos lasers. Entretanto, a maioria dos trabalhos da área concentra-se em simulações numéricas do comportamento de sistemas caóticos. Com o objetivo de verificar aplicações em engenharia do sincronismo entre circuitos, foi proposto o circuito eletrônico partícula em caixa, que é relativamente simples, se comparado com outros trabalhos na literatura. A originalidade deste trabalho consiste em verificar a robustez de alguns sistemas compostos de circuitos idênticos que simulam o comportamento de uma partícula em caixa em configurações mestre-escravo, em diversas topologias, explorando o sincronismo dos mesmos utilizando uma malha fechada de realimentação de erro. A robustez do acoplamento destes sistemas é estudada por meio de montagens experimentais e simulações numéricas. A observação da sua dinâmica permite sugerir aplicações na área de telecomunicações em multiplexação de sinais, acesso multiusuário e tecnologia CDMA (Code Division Multiple Access) / The dynamics of chaotic systems is a relatively new research area, directly related to the fields of engineering, physics and applied mathematics. Synchronization between dynamic systems has been a very frequent topic of research, covering fields ranging from mechanics of celestial bodies to the physics of lasers. However, most of the work area focuses on numerical simulations of the behavior of chaotic systems. In order to verify engineering applications of synchronism of circuits, it was proposed a particle in a box electronic circuit, which is relatively simple if compared to other studies. The originality of this work is to verify the robustness of some systems composed of identical circuits that simulate the behavior of a particle in a box in master-slave configurations in several topologies, exploring their synchronism using a closed loop feedback error. The strength of the coupling of these systems is studied through numerical simulations and experimental setups. The observation of this dynamics allows us to suggest applications in telecommunications in signal multiplexing, multiuser access and CDMA (Code Division Multiple Access)