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Estudo do efeito de dipolos em arranjos de antenas adaptativas de sistemas de comunica??o DSCDMATorquato, Ciro Augusto Paula 17 October 2003 (has links)
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Previous issue date: 20031017 / This master dissertation introduces a study about some aspects that determine the aplication of adaptative arrays in DSCDMA cellular systems. Some basics concepts and your evolution in the time about celular systems was detailed here, meanly the CDMA tecnique, specialy about spreadcodes 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 disserta??o de mestrado vem trazer um estudo sobre alguns aspectos que influenciam na aplica??o de antenas adaptativas em sistemas celulares DSCDMA (ou simplesmente CDMA). Foram detalhados alguns conceitos b?sicos a respeito do sistema celular e em geral, bem como sua evolu??o ao longo do tempo, dando ?nfase ? t?cnica CDMA, no que diz respeito aos c?digos de espalhamento e princ?pio de funcionamento. A partir disso, o ambiente de r?dio m?vel, com suas caracter?sticas peculiares, foi abordado, bem como os conceitos b?sicos em que se baseiam o sistema de antenas adaptativas com sua poderosa capacidade de filtragem espacial, capaz de reduzir significativamente o efeito de sinais indesejados. Tamb?m alguns algoritmos adaptativos foram discutidos, esses s?o integrantes do processamento dos sinais captados pelos arranjos, e s?o respons?veis pela atualiza??o dos pesos que de certa forma controlar?o o diagrama de radia??o do arranjo. Mais especificamente, esse trabalho fundamentouse na an?lise, mediante simula??es computacionais, do comportamento do sistema de antenas adaptativas face ao tipo de antena e ao tipo (geometria) de arranjo empregados. Todas as simula??es foram feitas utilizando o software Mathematica 4.0. Os resultados para a converg?ncia dos pesos, erro m?dio quadr?tico, ganho, diagrama de radia??o e capacidade de supress?o foram as grandezas que basearam as an?lises aqui feitas, utilizando para isso, os algoritmos RLS (supervisionado) e LSDRMTA (cego).

22 
[en] STRUCTURES AND ADAPTIVE ALGORITHMS FOR BLIND DETECTION OF DSCDMA SIGNALS / [pt] ESTRUTURAS E ALGORITMOS ADAPTATIVOS PARA DETECÇÃO ÀS CEGAS DE SINAIS DSCDMATIAGO TRAVASSOS VIEIRA VINHOZA 24 June 2008 (has links)
[pt] Esta tese apresenta novas estruturas e algoritmos
adaptativos para detecção às cegas de sinais DSCDMA. São
investigados receptores cegos com restrições lineares
baseados nas funções custo de mínima variância (CMV) e
módulo constante (CCM). Algoritmos adaptativos do tipo
AffineProjection para estimação dos parâmetros do receptor
são desenvolvidos e seu desempenho em estado estacionário é
analisado. Também são apresentados algoritmos adaptativos
para estimação às cegas do canal de comunicações. Em
seguida, novas estruturas de canceladores de interferência
são propostas. Primeiramente um cancelador de interferência
paralelo (PIC) linear baseado na função custo CCM é
proposto. Em seguida é desenvolvido um novo esquema
nãosupervisionado de cancelamento sucessivo de
interferência (SIC), baseado no conceito de arbitragem
paralela. Por fim, é apresentado um esquema híbrido (HIC)
que combina a estrutura SIC com uma estrutura multi
estágio, resultando em melhores estimativas para detecção e
desempenho uniforme para os usuários do sistema. / [en] This thesis presents new structures and adaptive algorithms
for blind detection of DSCDMA signals. Linearly
constrained minimum variance (CMV) and constant modulus
(CCM) receivers are investigated. Blind adaptive Affine
Projection like algorithms for receiver parameter estimation
are derived and its steadystate performance is analyzed.
Blind adaptive channel estimation algorithms are also
presented. This work also proposes new interference
cancellation structures. Firstly, a blind linear parallel
interference canceller (PIC) based on the CCM cost function
is proposed. Secondly, a new nonsupervised serial
interference canceller (SIC) based on the parallel
arbitration concept is developed. Finally, an hybrid
interference cancellation scheme (HIC) which combines SIC
and multiple PIC stages is presented.

23 
Uplink Power Control and Soft Handoff Prioritization in Multimedia DSCDMAShi, Wei 20 January 2006 (has links)
In the CDMA cellular networking system, power control is a very important issue because it is an interference limited system. In order to reduce the nearfar problem and improve the battery life of mobile station, the transmit power of mobile stations must be controlled to limit interference. In this paper, we study the effect of power control on system performance. Different power control rates may have influence on the performance. Meanwhile, we take the consideration of different call admission control algorithm. By introducing soft handoff waiting queue and guard channel into the soft handoff algorithm, we compare the power control influence on a base case (which is similar to IS95 algorithm, but with perfect power control) and proposed call admission control algorithm. The simulation shows that increasing power control rate and combination of power control and soft handoff prioritization can greatly reduce the blocking rates and refuse rates of new/soft handoff calls, thus the system performance is improved.

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Signal formats for code division multiple access wireless networks.Wysocki, Beata J. January 1999 (has links)
One of the fundamental problems related to the development of direct sequence code division multiple access (DS CDMA) wireless data networks is design of spreading sequences possessing semioptimal characteristics. In this thesis, we introduce three new methods to design spreading sequences, which can be optimised to achieve the desired characteristics.We show that the level of MAI for the DS CDMA systems utilising the example sets of sequences designed by the use of these techniques can be relatively low, compare to the case when the well known Goldlike sequences [29] are used. In addition, we show that by using one of the methods introduced in the thesis, we can construct sets of orthogonal sequences possessing acceptable correlation properties, even for an asynchronous operation, while another of the introduced methods can be used if design of sequences of an arbitrary length is required.Our new methods to design complex polyphase sequences are orientated towards the short length sequences, as a target application for them are high data rate wireless networks. Those methods are based on using discretised chirp pulses, pulses consisting of discretised multiple chirps, or linear combinations of them. In order to achieve orthogonality among the designed polyphase sequences, we combined the sequences based on superimposed chirps and double chirps with the sequences derived from the orthogonal Walsh functions.Finally, we utilise the three most promising sequence sets designed by the use of die introduced methods to simulate the multiuser DS CDMA systems. We compare performance of those simulated systems with the performance of the simulated system utilising 15chip Gold like sequences. The comparison results indicate that by using our design methods, we can produce useful sequence sets for applications where short spreading sequences are required. The presented ++ / results also demonstrate that the performance of systems utilising those sequences can be significantly better in terms of the number of simultaneously active users or bit error rate (BER) that the performance of the system employing Gold or Goldlike sequences of the similar length.

25 
Adaptive DSCDMA Receivers with Fast Tracking Capability for Wireless CommunicationsSun, Chunhung 25 April 2007 (has links)
The direct sequence (DS) code division multiple access (CDMA) is one of the most promising multiplexing technologies for wireless communications. It is also a core technology used in the wideband CDMA (WCDMA) system for the third generation (3G) wireless communication systems. In practice, in the CDMA systems the incomplete orthogonal of the spreading codes between users may introduce the socalled multiple access interference (MAI). Usually, the nearfar problem exists when the interfering users are assigned powers much higher than the desired user. Such that the system performance might degrade, dramatically, and thus limits the system capacity. To circumvent the abovementioned problems many effective adaptive multiuser detectors, based on the minimum mean square error (MMSE) and the minimum output energy (MOE) criteria subject to certain constraints have been proposed. In addition, to mitigate multipath fading effect, RAKE receiver was adopted due to the advantages of path diversity, thus, enhances the system performance. To implement the blind adaptive multiuser detector the linearly constrained minimum variance (LCMV), which is the constrained version of MOE, has been suggested. Further, the LCMVbased receivers exhibit high sensitivity to the channel mismatch caused by the unreliable estimation. To deal with this problem the constant modulus (CM) criterion was considered. In this dissertation, to deal with diverse phenomena encountered in practical channels, we first propose new blind adaptive multiuser detectors, based on the Min/Max criterion associated with the LCCM approach. For implementation the LC exponential window (EW) recursive leastsquare (RLS) algorithm is derived, and is referred to as the EW LCCMRLS receiver. It can be used to effectively suppress the MAI and ISI, simultaneously, over multipath fading channels and are robust to mismatch problem caused by inaccuracies in the acquisition of timing and spreading code of the desired user. To reduce the complexity of the abovementioned blind adaptive multiuser receiver with the LCCMRLS algorithm, the socalled generalized sidelobecanceller (GSC) structure is adopted, results in obtaining new CMGSCRLS algorithm. Moreover, to further improve the system performance for multipath fading and timevarying channel, the sliding window (SW) LCCMRLS and SW CMGSCRLS algorithms are developed. It can be employed for multipath fading channel with the rapidly changing strong narrowband interference (NBI), which is joined suddenly to the CDMA systems. To look more inside the effect of selecting the initial value of the input signals autocorrelation matrix, some theoretical analyses for the SW LCRLS as well as EW LCRLS are provided. Since, unfortunately, the LCCM criterion is known to highly depend on the exact knowledge of the desired user amplitude that is not known exactly at receiver. In the final of this dissertation, a novel linearly constrained adaptive constant modulus RLS (LCACMRLS) algorithm for blind DSCDMA receiver is proposed. With this new proposed LCACMRLS algorithm, the amplitude variation of the desired user, due to changing characteristics of the channel, can be tracked adaptively. Thus, better performance achievement, in terms of output signaltointerferenceplusnoise ratio (SINR) and bit error rate (BER), over the conventional LCCMLMS and LCCMRLS algorithms can be expected.

26 
Adaptive Rake Multiuser Receiver with Linearly Constrained Sliding Window RLS Algorithm for DSCDMA SystemsLee, HsinPei 04 July 2003 (has links)
The technique of direct sequence code division multiple access (DSCDMA) cellular system has been the focus of increased attention. In this thesis, we will consider the environment of DSCDMA systems, where the asynchronous narrow band interference due to other systems is joined suddenly to the CDMA system. The suddenly joined narrow band interference will make the system crush down. The main concern of this thesis is to deal with suddenly joined narrow band interference cancellation.
An adaptive filtering algorithm based on sliding window criterion and variable forgetting factor is known to be very attractive for violent changing environment. In this thesis, a new sliding window linearly constrained recursive least squares (SW LCRLS) algorithm and variable forgetting factor linearly constrained recursive least squares (VFF LCRLS) algorithm on the modified minimum mean squared error (MMSE) structure [9] is devised for RAKE receiver in direct sequence codedivision multiple access (DSCDMA) system over multipath fading channels. Where the channel estimation scheme is accomplished at the output of adaptive filter. The proposed SW LCRLS algorithm and VFF LCRLS has the advantage of having faster convergence property and tracking ability, and can be applied to the environment, where the narrow band interference is suddenly joined to the system, to achieve desired performance. Via computer simulation, we show that the performance, in terms of mean square errors (MSE) and signal to interference plus noise ratio (SINR), is superior to the conventional LCRLS and orthogonal decompositionbased LMS algorithms based on the MMSE structure [9].

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Detecção multiusuário baseada em tensores para sistemas de comunicação sem fio cooperativos / Tensorbased multiuser detection for cooperative wireless communications systemsPeixoto, Antonio Augusto Teixeira 07 1900 (has links)
Peixoto, A. A. T. Detecção multiusuário baseada em tensores para sistemas de comunicação sem fio cooperativos. 2017. 115 f. Dissertação (Mestrado em Engenharia Elétrica e da Computação)  Campus de Sobral, Universidade Federal do Ceará, Sobral, 2017. / Submitted by Programa de PósGraduação Engenharia Elétrica e de Computação (secretaria_ppgeec@sobral.ufc.br) on 20170814T13:53:24Z
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Previous issue date: 201707 / Signal processing applications in wireless communications may sometimes take advantage of multilinear algebra concepts. This can be done by modeling the signals as high order tensors. From this context, tensor decompositions such as the Parallel Factor analysis (PARAFAC), may be found useful. On the other hand, cooperative communications and MultipleInput MultipleOutput (MIMO) systems are ways for granting better data rates, capacity, fading mitigation and coverage. Joining the signal processing capabilities of tensor algebra, MIMO and cooperative communications can bring great benefits in wireless communications systems. In this dissertation, two receivers are proposed for two system models that are a multiuser DSCDMA (DirectSequence CodeDivision MultipleAccess) uplink based on multirelay cooperative communications. The two system models are almost the same, except that in one of them, multiuser
interference is considered at the relays. The AmplifyandForward (AF) protocol is used on all the relays, thus exploiting cooperative diversity. For the received signal of the first system model, a quadrilinear PARAFAC decomposition will be adopted and by doing so, the proposed tensorbased semiblind receiver can
jointly estimate the transmitted symbols, channel gains and spatial signatures of all users by assuming previous knowledge of the users spreading codes and a few transmitted symbols. For the second system model, multiuser interference is considered at the relays, then, a receiver based on a trilinear PARAFAC decomposition is proposed. The estimation of the second receiver is done in two phases with the first phase being a supervised stage where nonorthogonal training sequences are sent by all users. During the second phase, the users' data symbols are then estimated. Both receivers use the Alternating Least Squares (ALS) algorithm to fit the tensor models, assuming no channel state information (CSI) at the base station neither at the relays. With computational simulations, we will also provide performance evaluation of the proposed receivers for various cases and system variations. / As aplicações de processamento de sinal em sistemas de comunicações sem fio às vezes podem tirar proveito de conceitos de álgebra multilinear. Isso pode ser feito modelando os sinais como tensores de ordem elevada. Neste contexto, as decomposições tensoriais, tais como a análise de fatores paralelos (Parallel Facor  PARAFAC), podem ser úteis. Por outro lado, as comunicações cooperativas e a área de sistemas de múltiplasentradas e múltiplassaídas (MultipleInput MultipleOuput  MIMO) são uma maneira de se alcançar melhores taxas de dados, capacidade, qualidade de transmissão e cobertura. Juntandose as capacidades de processamento de sinal da álgebra tensorial, dos sistemas MIMO e das comunicações cooperativas, podemos obter grandes benefícios nos sistemas de comunicações sem fio. Nesta dissertação, dois receptores são propostos para dois modelos de sistema, que são o enlace reverso de um sistema DSCDMA multiusuário baseado em comunicações cooperativas auxiliadas por múltiplos retransmissores.
Os dois modelos de sistema são quase iguais, exceto que em um deles, a interferência de múltiplos usuários é considerada nos retransmissores. O protocolo AmplifyandForward (AF) é aplicado em cada retransmissor, explorando a diversidade cooperativa. Para o sinal recebido no primeiro modelo
de sistema, uma decomposição tensorial PARAFAC quadrilinear será adotada e, ao fazêlo, o receptor semicego proposto pode estimar conjuntamente os símbolos transmitidos, ganhos de canais e assinaturas espaciais de todos os usuários, assumindo o conhecimento prévio dos códigos de espalhamento dos usuários e alguns símbolos transmitidos. Para o segundo modelo de sistema, interferência multiusuário é considerada nos retransmissores dos usuários, então, um receptor baseado em uma decomposição PARAFAC trilinear é proposto. O segundo receptor realiza as estimações em duas fases, sendo a primeira fase um estágio supervisionado em que todos os usuários enviam sequências de treinamento não
ortogonais. Durante a segunda fase, os símbolos de dados dos usuários são então estimados. Ambos os receptores usam o algoritmo ALS (Alternating Least Squares) para ajustar os modelos tensoriais, assumindo nenhuma informação de estado do canal (CSI  Channel State Information) na estação base nem nos retransmissores. Com simulações computacionais, também forneceremos avaliação de desempenho dos receptores propostos para vários casos e variações do sistema.

28 
Performance Analysis Of Multicarrier DSCDMA SystemsShankar Kumar, K R 04 1900 (has links) (PDF)
No description available.

29 
Improved Statistical Interference Suppression Techniques in Single and Multirate Direct Sequence Spread Spectrum Code Division Multiple Access SystemsWang, Beibei 20 April 2007 (has links)
No description available.

30 
Blind rate detection for multirate DSCDMA signalsSharma, Abhay January 2000 (has links)
No description available.

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