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S/MIMO MC-CDMA Heuristic Multiuser Detectors Based on Single-Objective Optimization

ABRAO, Taufik; OLIVEIRA, Leonardo D. de; CIRIACO, Fernando; Angelico, Bruno Augusto; Jeszensky, Paul Jean Etienne; PALACIO, Fernando Jose Casadevall
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
37.36%
This paper analyzes the complexity-performance trade-off of several heuristic near-optimum multiuser detection (MuD) approaches applied to the uplink of synchronous single/multiple-input multiple-output multicarrier code division multiple access (S/MIMO MC-CDMA) systems. Genetic algorithm (GA), short term tabu search (STTS) and reactive tabu search (RTS), simulated annealing (SA), particle swarm optimization (PSO), and 1-opt local search (1-LS) heuristic multiuser detection algorithms (Heur-MuDs) are analyzed in details, using a single-objective antenna-diversity-aided optimization approach. Monte- Carlo simulations show that, after convergence, the performances reached by all near-optimum Heur-MuDs are similar. However, the computational complexities may differ substantially, depending on the system operation conditions. Their complexities are carefully analyzed in order to obtain a general complexity-performance framework comparison and to show that unitary Hamming distance search MuD (uH-ds) approaches (1-LS, SA, RTS and STTS) reach the best convergence rates, and among them, the 1-LS-MuD provides the best trade-off between implementation complexity and bit error rate (BER) performance.; Brazilian CAPES Agency[BEX0556/07-6]

Algoritmo de escolha de sequencias de espalhamento em sistemas CDMA considerando a interferencia de celulas adjacentes; Spreading sequences selection algorithm for CDMA systems considering the interference from adjacent cells

Paulo Marcelo Perez Rodrigues de Britto
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 11/12/2006 Português
Relevância na Pesquisa
37.49%
O desempenho de sistemas de comunicações sem fio que utilizam técnicas de espalhamento espectral e múltiplo acesso por divisão de código (CDMA) é limitado pela interferência. Nesta dissertação, analisamos o desempenho de um algoritmo de seleção de seqüências de espalhamento de comprimento fixo, que busca a minimização dos efeitos de interferência em sistemas CDMA operando em canais com desvanecimento seletivo em freqüência e possuindo células adjacentes interferentes. Analisamos o desempenho deste sistema no qual o espalhamento espectral é feito usando duas seqüências: seqüências do usuário e seqüências identificadoras de células. Dentre as seqüências analisadas, podemos citar as Walsh, a Gold, as de comprimento máximo e também um tipo de seqüência de espalhamento baseado nas seqüências de comprimento máximo; The performance of wireless communication systems using spread spectrum techniques and code division multiple access (CDMA) is interference-limited. In this dissertation, we evaluate the performance of a selection algorithm for fixed-length spreading sequences, aimed on minimizing the interference effects in CDMA systems operating in frequency selective fading channels and having adjacent interfering cells. We check the performance of this system where the spread spectrum operation is performed using two sequences: user sequences and cell identification sequences. Among the sequences considered...

Controle de congestionamento do protocolo TCP em sistemas de comunicação sem fio CDMA usando estrategia de detecção multiusuario, arranjo de antenas e correção de erro FEC; A new TCP congestioned window algorithm for wireless CDMA system using multiuser decorrelating detection, antenna array and FEC

Gonzalo Fernando Olmedo Cifuentes
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 28/11/2008 Português
Relevância na Pesquisa
37.36%
Neste trabalho foi proposto um novo algoritmo para o controle da janela de congestionamento do protocolo TCP, que melhora o desempenho da vazão de dados em redes sem fio. A estimação da banda disponível responsável pela melhoria do sistema, se dá pois os segmentos TCP com erro produzidos pelo canal sem fio são reconhecidos por uma confirmação negativa NACK, ou quando o buffer do sistema enche. Para o mecanismo proposto, uma expressão analítica da vazão de dados em função da probabilidade de erro de segmentos TCP no canal sem fio é obtida. No sistema sem fio é analisado o enlace reverso de sistemas CDMA de sequencia direta, tanto síncrono, como assíncrono, considerando um canal seletivo em frequencia com desvanecimento do tipo Rayleigh e modulação BPSK. São comparados diferentes tipos de receptores, que usam detecção multiusuário descorrelacionadora, arranjo de antenas e codificação de canal do tipo convolucional ou turbo. Foram obtidas expressões simples e precisas, antes não encontradas na literatura da eficincia assintotica média e da probabilidade de erro de bit que foram comparadas com resultados de simulação. Foram comparadas tres estratégias propostas de decodificação iterativa turbo. Expressões de complexidade computacional do receptor também foram elaboradas.; In this work...

Emprego de antenas adaptativas para a estimação de dados em ambiente CDMA; Applying adaptive antennas for data estimation in CDMA medium

Puttini, Saulo Benigno
Fonte: Universidade de Brasília Publicador: Universidade de Brasília
Tipo: Dissertação
Português
Relevância na Pesquisa
37.58%
Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Elétrica, 2006.; Este trabalho fundamenta-se em propor e avaliar o desempenho de um modelo receptor adaptativo, com utilização de arranjo de sensores, a ser empregado em meios de multiplicidade de acesso via divisão por códigos (CDMA) para fins de estimação de dados. Inicialmente é apresentado um estudo sobre arranjos de antenas, desenvolvendo-se o equacionamento de um arranjo linear e uniforme (ULA). Enfatiza-se o emprego deste para fins de separação espacial de usuários, sendo relatadas e ilustradas algumas formas de conformação de feixe. A seguir, o trabalho aborda o emprego de algoritmos adaptativos, especialmente o método de Wiener e filtro de Mínima Média Quadrática (LMS), para arranjos de sensores, originando os tão conhecidos arranjos adaptativos. Prosseguindo, aborda-se o problema de estimação da direção de chegada (DOA), sendo ilustrados alguns métodos amplamente difundidos na literatura especializada. Algumas simulações de espectro espacial de potência são realizadas, visando a avaliar, principalmente, a capacidade de resolução e a imunidade em relação ao ruído. É apresentado, então...

Transmit space-frequency prefiltering technique for downlink TDD MC-CDMA systems

Silva, Adão; Gameiro, Atílio
Fonte: IEEE Publicador: IEEE
Tipo: Conferência ou Objeto de Conferência
Português
Relevância na Pesquisa
37.36%
In this communication we present a space-frequency pre-filtering technique, for downlink time division duplex (TDD) MC-CDMA systems, where the base station is equipped with an antenna array. We show that the pre-filtering approach can considerably reduce the multiple access interference at the mobile terminals allowing to transfer a significant part of the computational complexity to the base station, using a very low complex receiver at mobile. This approach relies on the availability of the channel state information at transmission, i.e., uses the time division duplex channel reciprocity between alternative uplink and downlink to obtain the channel state information. Simulation results are presented to demonstrate the effectiveness of the proposed prefiltering algorithm. Moreover, the performance of the proposed pre-filtering algorithm is assessed in two distinct scenarios: beamforming and diversity.; European IST-2001-32620 MATRICE project (MC-CDMA Transmission Techniques for Integrated Broadband Cellular Systems); FCT

IB-DFE with interference alignment precoding scheme for MC-CDMA systems; Esquemas de pré-codificação IA com IB-DFE para sistemas MC-CDMA

Moreira, José Eduardo Leal
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Dissertação de Mestrado
Português
Relevância na Pesquisa
37.58%
To achieve high bit rates, needed to meet the quality of service requirements of future multimedia applications, multi-carrier code division multiple access (MC-CDMA) has been considered as a candidate air-interface. Interference alignment (IA) is a promising technique that allows high capacity gains in interfering channels. On the other hand, iterative block decision feedback equalization (IB-DFE) based receivers can efficiently exploit the inherent space-frequency diversity of the MIMO MC-CDMA systems. In this thesis we proposed an IA precoding at the transmitter with IB-DFE based processing at the receiver for MC-CDMA systems. The IA precoding is applied at chip level instead of the data symbols level, as in the conventional IA based systems. The receiver is designed in two steps: first the equalizers based on zero forcing (ZF) or minimum mean square error (MMSE) are used to remove the aligned users´ interference. Then and after a whitening noise process, an IB-DFE based equalizer is designed to remove both the residual inter-user aligned and inter-carrier interferences. The results have shown that the obtained performance is very close to the one obtained by the optimal matched filter, with few iterations at the receiver side.; Para atingir maiores ritmos de transmissão...

Equalization and precoding techniques for future MC-CDMA systems; Técnicas de equalização e pré-codificação para sistemas MC-CDMA

João, Alícia Mafalda de Figueiredo Paiva
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Dissertação de Mestrado
Português
Relevância na Pesquisa
37.63%
O número de dispositivos com ligações e aplicações sem fios está a aumentar exponencialmente, causando problemas de interferência e diminuindo a capacidade do sistema. Isto desencadeou uma procura por uma eficiência espectral superior e, consequentemente, tornou-se necessário desenvolver novas arquitecturas celulares que suportem estas novas exigências. Coordenação ou cooperação multicelular é uma arquitectura promissora para sistemas celulares sem fios. Esta ajuda a mitigar a interferência entre células, melhorando a equidade e a capacidade do sistema. É, portanto, uma arquitectura já em estudo ao abrigo da tecnologia LTE-Advanced sob o conceito de coordenação multiponto (CoMP). Nesta dissertação, considerámos um sistema coordenado MC-CDMA com pré-codificação e equalização iterativas. Uma das técnicas mais eficientes de pré-codificação é o alinhamento de interferências (IA). Este é um conceito relativamente novo que permite aumentar a capacidade do sistema em canais de elevada interferência. Sabe-se que, para os sistemas MC-CDMA, os equalizadores lineares convencionais não são os mais eficientes, devido à interferência residual entre portadoras (ICI). No entanto, a equalização iterativa no domínio da frequência (FDE) foi identificada como sendo uma das técnicas mais eficientes para lidar com ICI e explorar a diversidade oferecida pelos sistemas MIMO MC-CDMA. Esta técnica é baseada no conceito Iterative Block Decision Feedback Equalization (IB-DFE). Nesta dissertação...

Análise de desempenho de sistemas CDMA, utilizando multi-portadoras e multi-códigos; Performance analysis of CDMA systems, using multi carriers and multi codes

Araújo, Alessandra Sousa
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Dissertação
Português
Relevância na Pesquisa
37.7%
O avanço tecnológico em telecomunicações mostra que inúmeros e dife- rentes sistemas vêm surgindo a cada dia. Estes sistemas se adequam às necessidades do mercado, pela sua evolução. A grande variedade de serviços oferecidos a cada dia pelos sistemas de comunicação movel é o reflexo da necessidade de acesso e de sua utilização. Este trabalho analisa o desempenho de tres sistemas: Multi-portadora CDMA, Multi-códigos CDMA e Multi-portadora e Multi-códigos CDMA com multi-taxas de serviços utilizando-se a modulação BPSK. O modelo desses sis- temas consiste no transmissor e receptor, com análise da relação sinal/ruí³do mais interferência (SNIR) e a probabilidade média de erro do bit (Pe médio). O desempenho desses sistemas e apresentado pela comparação ao do número de sub-rajadas, do número de portadoras, do número de usuários, dos diferen- tes parâmetros de fading, da ordem da diversidade e das propriedades multi trajetos de propagação. O sistema Multi-portadoras e Multi-codigos CDMA em termos de SNIR e da probabilidade media de erro do bit quando comparado os sistemas Multi- portadoras CDMA e Multi-códigos CDMA apresentou uma melhora de per- formance. ______________________________________________________________________________ ABSTRACT; The technology advance in telecommunication systems shows that un- countable and di®erent systems have been raised every day. These systems suit to the market needs in terms of evolution. The wide variety of services o®ered every day by the mobile communication systems is response of the need for access and their utilization. This work analyzes the performance of three systems: Multi-Carrier CDMA...

Simulador das interferências de campos elétrico e magnético em função da potência para estação rádio base de "Acesso Múltiplo por Divisão de Código - CDMA" na faixa de frequência de 800 MHz

Kiszka Júnior, Pedro
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Dissertação
Português
Relevância na Pesquisa
37.36%
Neste trabalho foram desenvolvidos e criados dois simuladores para cálculos e indicações de valores Máximos Permissíveis para os campos elétricos e magnéticos, bem como as Densidades de Potência em Estações Rádio Base, com a utilização de Tecnologia CDMA, na faixa de 800 MHz. Esses valores permissíveis foram referênciados e fundamentados pela Comissão Internacional de Proteção à Radiação não Ionizante. O simulador 1 permite calcular as interferências de campo irradiado por estação rádio base, com entrada de dados tais como: Potência do Canal de Rádio; Ganho da Antena; Número de Canais de Rádio; Frequência de Operação; Perdas no Cabo; Atenuação da Direção; Distância Mínima; Reflexões. O referido simulador permite, de maneira rápida e sem a necessidade da execução de instrumentos para medições, alcançar os seguintes valores calculados: Potência Radiada Efetiva; Densidade de Potência do Setor; Campo elétrico no Setor; Campo Magnético no Setor; Densidade de fluxo Magnético; ponto de exposição máxima permitida de campo elétrico, bem como a densidade de potência. Os resultados são apresentados em gráficos, para clareza da visualização da densidade de potência no setor, assim como para a definição da área de cobertura. O simulador abrange também pastas com especificações de antenas...

Multiuser Channel Estimation and Tracking for Long Code CDMA Systems

Bhashyam, Srikrishna; Aazhang, Behnaam; Bhashyam, Srikrishna; Aazhang, Behnaam
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
37.43%
Journal Paper; Channel estimation techniques for code-division multiple access (CDMA) systems need to combat multiple access interference (MAI) effectively. Most existing estimation techniques are designed for CDMA systems with short repetitive spreading codes. However, current and next generation wireless systems use long spreading codes whose period is much larger than the symbol duration. In this paper, we derive the maximum likelihood channel estimate for long code CDMA systems over multipath channels using training sequences and approximate it using an iterative alogrithm to reduce the computational complexity in each symbol duration. The iterative channel estimate is also shown to be asymptotically unbiased. The effectiveness of the iterative channel estimator is demonstrated in terms of squared error in estimation as well as the bit error rate performance of a multistage detector based on the channel estimates. The effect of error in decision feedback from the multistage detector (used in the absence of training sequences) is also shown to be neglible for reasonable feedback error rates using simulations. The proposed iterative channel estimation technique is also extended to track slowly varying multipath fading channels using decision feedback. Thus...

Multiuser Channel Estimation for Long Code CDMA Systems

Bhashyam, Srikrishna; Aazhang, Behnaam; Bhashyam, Srikrishna; Aazhang, Behnaam
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Conference paper
Português
Relevância na Pesquisa
37.43%
Conference Paper; Channel estimation techniques for code-division multiple access (CDMA) systems need to combat multiple access interference (MAI) effectively. Most existing estimation techniques are designed for CDMA systems with short repetitive spreading codes. However, current and next generation wireless systems use long spreading codes whose period is much larger than the symbol duration. In this paper, we derive the maximum likelihood channel estimate for long code CDMA systems over multipath channels using training sequences and approximate it using an iterative algorithm to reduce the computational complexity in each processing window. The asymptotic convergence of the mean of the iterative estimate to the actual channel is also shown. The effectiveness of the iterative channel estimator is demonstrated in terms of squared error in estimation as well as the bit error rate performance of a multistage detector based on the channel estimates. Finally, the proposed iterative channel estimation technique is extended to track slowly varying multipath fading channels using decision feedback. Thus, an MAI resistant multiuser channel estimate with reasonable computational complexity is derived for long code CDMA systems over multipath fading channels.

Reducing Dynamic Power Consumption in Next Generation DS-CDMA Mobile Communication Receivers

Chandrasekhar, Vikram; Chandrasekhar, Vikram
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
37.43%
Masters Thesis; Reduction of the power consumption in portable wireless receivers is an important consideration for next-generation cellular systems specified by standards such as the UMTS, IMT2000. This thesis explores the design-space for reducing the dynamic power dissipation in a RAKE receiver for the Direct Sequence Code Division Multiple Access (DS-CDMA) downlink. Starting with a reference implementation of the DS-CDMA RAKE receiver, we demonstrate design methodologies for achieving significant power reduction, while highlighting the corresponding performance trade-offs. At the algorithm level, we investigate the impact of reduced precision and arithmetic complexity on the performance of the DS-CDMA RAKE receiver. We then present architectures for implementing the reference and reduced complexity DS-CDMA RAKE receivers, and analyze these architectures with respect to their dynamic power dissipation. Finally, we analyze clock-gating techniques for reducing the activity rate in both the architectures to achieve further power reduction.

Parallel Algorithms and Architectures for near-far resistant CDMA acquisition

Kota, Kishore; Kota, Kishore
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
37.49%
PhD Thesis; Subspace-based algorithms are a class of algorithms for estimation problems in array signal processing and more recently near-far resistant Code Division Multiple Access (CDMA) acquisition problems. Subspace-based algorithms are based on estimating signal or noise subspaces from the received data vectors and then performing some form of optimization to estimate the desired parameters. This thesis presents two new parallel algorithms applicable in the estimation of signal or noise subspaces from the received data vectors. The first algorithm is a pipelined SVD algorithm which allows pipelining of multiple independent singular value decomposition (SVD) problems on a single processor array. The resultant algorithm uses the exibility provided by the Jacobi algorithm by defining a new parallel ordering to result in a simple uniform array in which all communication including the initial load and the final unload operations are pipelined. The second algorithm described in this thesis is a sliding window SVD updating algorithm where the signal or noise subspace is updated whenever a new observation vector is received by applying a fixed-length window over the data. An important result shown in this thesis is that an important property ofdowndating problems...

A Software Simulation Testbed for CDMA Wireless Communication Systems

Sundaramurthy, Vishwas; Sundaramurthy, Vishwas
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
37.49%
Masters Thesis; This thesis develops a software wireless communication testbed which simulates a Code Division Multiple Access(CDMA) link. CDMA is a popular technology in cellular systems due to its superior capacity and performance. The designer of CDMA systems has a wide array of signal processing algorithms to choose from and a variety of operating environments to deal with. The testbed is a tool to evaluate these design options and trade-offs in different scenarios. The backbone of this system is a wireless CDMA multiuser link built using Simulink and Matlab. An efficient method of system modeling is used to speed up the simulations. This testbed can be used to study the performance of a CDMA wireless link with variation in system parameters and channel conditions. The use of Real-Time Workshop for DSP code generation is studied. This method is useful for rapid prototyping of algorithms and in DSP-based simulation acceleration of the testbed.

A Software Simulation Testbed for Third Generation CDMA Wireless Systems

Sundaramurthy, Vishwas; Cavallaro, Joseph R.; Sundaramurthy, Vishwas; Cavallaro, Joseph R.
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Conference paper
Português
Relevância na Pesquisa
37.36%
Conference Paper; This paper describes a testbed which simulates a third generation Code Division Multiple Access (CDMA) wireless link. The designer of next generation wideband CDMA systems has the choice of a wide array of advanced signal processing algorithms and a variety of operating environments. The Rice testbed is a tool to evaluate these design options and trade-offs in different system scenarios. The backbone of this testbed is a wireless CDMA multiuser link built using Simulink and Matlab. An efficient method of system modeling is used to accelerate the simulations. The testbed also uses a method for rapid prototyping of algorithms and DSP-based simulation acceleration for new algorithm complexity and performance evaluation.

Algorithms and Architectures for Channel Estimation in Wireless CDMA Communication Systems

Sengupta, Chaitali; Sengupta, Chaitali
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Thesis; Text; Text
Português
Relevância na Pesquisa
37.43%
PhD Thesis; Wireless cellular communication is witnessing a rapid growth in markets, technology, and range of services. An attractive approach for economical, spectrally efficient, and high quality digital cellular and personal communication services is the use of code division multiple access (CDMA) technology. The estimation of channel delays along with channel attenuation and phases of different users constitutes the first stage in the detection process at the receiving base station in a CDMA communication system. This stage, called channel parameter estimation, forms the bottleneck for the detection of users' bitstreams; both in terms of accuracy as well as execution time. In this thesis, we develop new algorithms and architectures to solve the CDMA channel estimation problem. We have first developed a framework that facilitates a computationally efficient solution to the combined problem of channel estimation and detection in a scenario involving multiple users, multiple paths, and multiple sensors at the receiver. The channel estimation approaches presented in this thesis, consist of two categories: (1) maximum likelihood based schemes, and (2) signal and noise subspace based schemes. The maximum likelihood approach is used to solve the complex multidimensional problem of channel estimation in the presence of multipath effects and concurrently using an antenna array at the base station receiver. Once the composite channel impulse response of each user is estimated...

Resource Allocation in Wireless CDMA Multimedia Networks

Guo, Yile; Guo, Yile
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Thesis; Text; Text
Português
Relevância na Pesquisa
37.36%
PhD Thesis; In this thesis we developed a resource allocation framework for wireless code division multiple access (CDMA) networks that support multi-class traffic with different data rates and bit error rate requirements. We proposed a new resource allocation scheme using joint adaptive power control and antenna array multiuser receiver in multipath fading system. In this scheme both transmit power and receiver filter adapt to time- varying fading channel state. By dynamically assigning users appropriate transmit power and receiver filter, the scheme can guarantee users' diverse quality of service (QoS) requirements and significantly improve quality and capacity of the system. We derived theory for abstraction of bandwidth resource and characterization of system capacity for multi-class traffic in multipath fading system. Bandwidth resource allocated to a user can be abstracted as "effective bandwidth", determined by the user's source data rate and target bit error rate. Capacity inmultipath fading system can be characterized by a theoretical bound. Simulations show that actual system capacity in multipath fading environment is close to the theoretical bound at large power constraint. The multirate multiuser receiver can achieve significantly larger capacity for users with higher source data rate and lower target bit error rate than conventional matched-filter receiver. The antenna array multiuser receiver can provide large capacity for users with higher signal-to-interference ratio requirement and achieve high bandwidth utility at lower power constraints. We also proposed a new call admission control scheme for CDMA cellular system that incorporates adaptive power control and antenna array multiuser receiver and supports multi-class traffic. The scheme is based on estimation of othercell interferenceand implemented distributively in each cell. The scheme can adapt to various traffic distribution. Capacity determined by the admission control agrees well with the actual system capacity in the simulation. The scheme can achieve high bandwidth utilization and guarantee QoS requirements of all the users.; Texas Advanced Technology Program; Nokia; National Science Foundation

Estudo do efeito de dipolos em arranjos de antenas adaptativas de sistemas de comunicação DS-CDMA

Torquato, Ciro Augusto Paula
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Engenharia Elétrica; Automação e Sistemas; Engenharia de Computação; Telecomunicações Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Engenharia Elétrica; Automação e Sistemas; Engenharia de Computação; Telecomunicações
Tipo: Dissertação Formato: application/pdf
Português
Relevância na Pesquisa
37.54%
This master dissertation introduces a study about some aspects that determine the aplication of adaptative arrays in DS-CDMA cellular systems. Some basics concepts and your evolution in the time about celular systems was detailed here, meanly the CDMA tecnique, specialy about spread-codes and funtionaly principies. Since this, the mobile radio enviroment, with your own caracteristcs, and the basics concepts about adaptive arrays, as powerfull spacial filter was aborded. Some adaptative algorithms was introduced too, these are integrants of the signals processing, and are answerable for weights update that influency directly in the radiation pattern of array. This study is based in a numerical analysis of adaptative array system behaviors related to the used antenna and array geometry types. All the simulations was done by Mathematica 4.0 software. The results for weights convergency, square mean error, gain, array pattern and supression capacity based the analisis made here, using RLS (supervisioned) and LSDRMTA (blind) algorithms.; Esta dissertação de mestrado vem trazer um estudo sobre alguns aspectos que influenciam na aplicação de antenas adaptativas em sistemas celulares DS-CDMA (ou simplesmente CDMA). Foram detalhados alguns conceitos básicos a respeito do sistema celular e em geral...

Some parameters that affect CDMA capacity analysis. Results using GIS based simulation

Navarro Cadavid, Andrés; Cardona Marcet, Narcís
Fonte: 3G Mobile Communication Technologies, 2001. Second International Conference Publicador: 3G Mobile Communication Technologies, 2001. Second International Conference
Tipo: article; Artículo Formato: PDF; Electrónico
Português
Relevância na Pesquisa
37.49%
In previous papers we describe a model for capacity analysis in CDMA systems using DC-Cell, a GIS based planning tool developed at Universidad Politecnica de Valencia, and MATLAB. We show some initial results of that model, and now, we are exploring different parameters like cell size, proximity between cells, number of cells in the system and “clustering” CDMA in order to improve the planning process for third generation systems. In this paper we show the results for variations of some of these parameters, specifically the cell size and number of cells. In CDMA systems is quite common to suppose only one carrier frequency for capacity estimation, and it is intuitive to think that for more base stations, mean more users. However the multiple access interference problem in CDMA systems could establish a limit for that supposition in a similar way that occurs in FDMA and TDMA systems.

Ordered Hunt Schemes for Overlaid CDMA Cellular Systems

Castañeda-Camacho,J.; Lara-Rodríguez,D.
Fonte: Facultad de Ingeniería, UNAM Publicador: Facultad de Ingeniería, UNAM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2010 Português
Relevância na Pesquisa
37.49%
The CDMA overlay concept, has been proposed as one alternative to take advantage of the bandwidth available in narrowband systems. In fact, the basic idea of the CDMA overlay is to allow to wideband CDMA wave forms, to share a common spectrum with narrowband conventional wave forms. In this work, we have focused in the analysis of the performance of the forward link of the CDMA and TDMA systems when they are overlaid. In our model, in order to limit the interference into the CDMA layer caused by the TDMA system, the use of notch filters has been considered. However, one drawback of the filters is that it rejects only one part of the interference generated by the TDMA system. Therefore, we have proposed two new ideas of reduction of the interference which can not be eliminated by filters; ordered hunt and real location of the slots. Finally, we present an analytical evaluation of the forward link capacity of the systems involved in the overlaid process, due to this is the limiting link and as a function of the outage probabilities. Practical considerations such as power requirements, power control, handoff, the offered load for different services and scenarios are also addressed.