He was born in Nancy-France. He received the B. S., M. S. and Ph. D., all in Electrical Engineering from EPUSP-Escola Politécnica da Universidade de São Paulo, in 1972, 1981, and 1989, respectively. From 1974 to 1978 he was with FDTE-Fundação para o Desenvolvimento Tecnológico da Engenharia as a member of Technical Staff on the development of Communication Systems. From 1978 to 1990 as Instructor he taught part-time at EPUSP and he was with FDTE and FUSP-Fundação de Apoio à Universidade de São Paulo where he was engaged as Technical Leader in various development programs of Communication Systems to industry and government. Since 1990 he has been with EPUSP where he is full-time Assistant Professor, Associate since 1992 and Full Professor since 2005, and Researcher in Communication Systems. Co-ordinator of LCS-Laboratório de Comunicações e Sinais of EPUSP in 1995/97, 1999/01 and 2003/05. President of the Undergraduate Commission of EPUSP in 2008/14. Associate Provost of the Undergraduate Studies of USP from 03/2011 to 01/2014. General Co-Chairmen of ITS'98-International Telecommunications Symposium, sponsored by SBrT - Sociedade Brasileira de Telecomunicações and IEEE/ComSoc, held in São Paulo from August 9 to 13,1998. General Chairman of the ISSSTA-06, 2006 IEEE Ninth International Symposium on Spread Spectrum Techniques and Applications, sponsored by EPUSP and technically co-sponsored by: IEEE, IEEE/ComSoc, IEE, VDE and SBrT, held in Manaus from August 28 to 31, 2006. Senior Member of IEEE since 2007 and SBrT since 2013. General co-ordinator for the cooperation agreements between Escola Politécnica and Ericsson do Brasil, Motorola do Brasil and Telesp-Celular, since 1999. He was visiting professor at UPC-Universitat Politécnica de Catalunya, Barcelona-Spain in 1995 and at TUB-Technical University of Budapest, Hungary in 2001. He is author of more than 140 research papers published in periodicals and symposiums and the book Sistemas Telefônicos (Editora Manole, 2007).
EPUSP-Escola Politécnica da Universidade de São Paulo
PTC-Departamento de Engenharia de Telecomunicações e Controle
LCS-Laboratório de Comunicações e Sinais
Caixa Postal 61548-São Paulo-SP-Brazil
- Communication Systems
- Wireless Communications
- Digital Telephony
- CDMA-Code Division Multiple Access
- Code Sequences for Spread Spectrum
- PTC-2549 Sistemas Telefônicos (Telephony)
- PTC-2433 Teoria das Comunicações II (Communications Theory II)
- PTC-3452 Teoria da Informação e Codificação (Information and Coding Theory)
- PTC-5710 Comunicação por Espalhamento Espectral (Spread Spectrum Communications)
- PTC-5757 Tópicos Especiais em Comunicações Digitais (Special Topics on Digital Communications)
- PTC-5869 Teoria Básica e Aplicações das Sequências de Códigos (Code Sequences: Theory and Applications)
TÓPICOS SOBRE A CARACTERIZAÇÃO DO DESEMPENHO DE SISTEMAS DS-CDMA (size: 1.41M), M. S. Dissertation, John Richard Fitzgerald Júnior, 3/1996. This master thesis addresses and compares several possible ways to determine CDMA (Code Division Multiple Access) systems performance, using specific and random sequences. The main body of the work concerns DS (Direct Sequence) systems with the use of deterministic code sequences. One evaluation method is developed using random code sequence for comparative effects. The performance is characterized by the system’s bit error probability considered as a quality index.
ANÁLISE DE UM SISTEMA DE COMUNICAÇÃO POR PACOTES PARA USO EM TELEFONIA MÓVEL MICROCELULAR (size: 985K), M. S. Dissertation, José Augusto de Lima, 1/1997. This master thesis establishes a mobile micro cellular communications systems characterization based on the PRMA (Packet Reservation Multiple Access) technique. The communication support is a high bit rate metropolitan area network for simultaneous voice and data transmission. The main performance measure is the voice package drop probability.
SEQÜÊNCIAS DE CÓDIGOS PARA USO EM COMUNICAÇÃO POR ESPALHAMENTO ESPECTRAL (size: 767K), M. S. Dissertation, Angel Antonio Gonzalez Martinez, 3/1997. This master thesis makes an exhaustive review of code sequences families used in spread spectrum communication and a possible choice optimization of them, when used in CDMA (Code Division Multiple Access) systems, is studied by simulation. Families of sequences are introduced (generated in linear and non-linear form) and their most important characteristics exposed. The work presents also some performance indicators for each family and an objective criterion for sequence selection.
UMA ESTRATÉGIA DE MIGRAÇÃO DE SISTEMAS DE TELEFONIA MÓVEL COM TECNOLOGIA AMPS PARA TECNOLOGIA CDMA (size: 3.18M), M. S. Dissertation, Ronald Luís Clarkson Eisner, 8/1997. This master thesis studies a strategy for the transition of a mobile phone system with FDMA (Frequency Division Multiple Access) technology to CDMA (Code Division Multiple Access) in terms of interference between both systems and increase of the subscriber capacity.
ANÁLISE DE UM MÉTODO DE AQUISIÇÃO EM DOIS ESTÁGIOS PARA SISTEMAS DS-CDMA (size: 1.18M), M. S. Dissertation, Ivan Roberto Santana Casella, 6/1998. This work tries to characterize the behavior of a new proposed DS-CDMA acquisition system. This new scheme is applied to DS-CDMA systems in which timing uncertainties between the received and local spreading code are inside a relatively small and known interval of the total uncertain region. Without the use of this kind of technique, the acquisition process determines the capacity limitation of DS-CDMA systems. Since it is possible to use a technique like this, the DS-CDMA system capacity is limited by the bit error probability, for a specific desired performance.
ANÁLISE DO USO DA ALOCAÇÃO DINÂMICA DE CANAIS EM SISTEMAS DE TELEFONIA CELULAR (size: 3.34M), M. S. Dissertation, Benedito José Barreto Fonseca Júnior, 8/1999. Fixed Channel Allocation (FCA) causes several problems in present cellular phone systems: need for frequency planning, poor tolerance to traffic load variations and low capacity due to low trunking efficiency and high design margins. Dynamic Channel Allocation (DCA) is an alternative to solve these problems. This research considers several different DCA algorithms under the same scenario, allowing a complete analysis and comparison of their performance. Call quality and stability are considered in detail. The impact of power control, user mobility and limited number of transceivers in base stations are studied separately. The application of DCA in TDMA systems and its main problems are also studied.
ANÁLISE DE SISTEMAS DS/CDMA DE MÚLTIPLA TAXA (size: 1.37M), M. S. Dissertation, Cyro Scarano Hemsi, 3/2000.The objective of this work is to study multi-rate DS/CDMA systems. The work focuses on capacity and resource optimization aspects of this system. From user specifications, as maximum transmission power and minimum rate and quality of service (QoS) requirements in a multi-class environment, a capacity expression is derived, which can be optimized to result the minimum total transmission power solution or the maximum total throughput one, as was investigated, initially for a single cell, next for multi-cell environment. Furthermore, the work studies a modification in the multi-rate CDMA transmission scheme (single-user detection with all users transmitting at same time) that proposes to time schedule the signals of delay-tolerant users and also maximize their rates in this situation, resulting throughput gains, when compared with the conventional transmission mode. These throughput gains were also compared with the ones obtained with SIC (successive interference cancellation) multi-user approach, which was also modeled in this work.
TÓPICOS SOBRE A DETERMINAÇÃO DA CAPACIDADE DE SISTEMAS DS/CDMA (size: 1.64M), M. S. Dissertation, Márcio Wagner Duarte Rolim, 6/2000. This master thesis establishes the capacity of DS/CDMA systems, in particular that defined by IS-95 standard. The determination is based on reverse channel (Mobile Unit to Base Station) considering the following additional factors: frequency reuse efficiency, imperfect power control, sectorization, vocal activity and soft handoff. Each factor was statistically characterized and finally we have obtained a general expression for the system capacity. At the end we have also calculated the direct channel (Base Station to Mobile Unit) limitation and with this determination we have concluded that the main limitation is on reverse channel.
ESTUDO DE TÉCNICAS DE ALOCAÇÃO DINÂMICA DE RECURSOS E SINCRONISMO PARA SERVIÇOS DE MULTIMÍDIA NUM SISTEMA MÓVEL CELULAR CDMA DE BANDA LARGA (size: 540K), M. S. Dissertation, Eduardo Meirelles Massaud, 8/2000. In this master thesis two fundamental topics in a cellular mobile system transmission process are presented: To make them feasible, direct sequence spread spectrum CDMA systems with transmission of multiple parallel channels per user are analyzed to reach higher throughputs. The relation between multimedia quality of service and limits on the number of codes are studied and analyzed through computer simulation in some specific cases. Parameters that make synchronization process between multimedia documents feasible are also analyzed and delay thresholds are established to keep the quality of services. Maximum loss information of each multimedia services is also studied to keep end-user reproduction quality of service. Some computer simulations of dynamic resource allocation are presented too.
CANCELADORES DE INTERFERÊNCIA MULTIUSUÁRIO APLICADOS A SISTEMAS DS/CDMA DE MÚLTIPLA TAXA (full size: 11.1M); or by parts:contents (size: 144K), chapter 1 (size: 152K), chapter 2 (size: 3.82M), chapter 3 (size: 1.76M), chapter 4 (size: 1.45M), chapter 5 (size: 3.17M), chapter 6 (size: 28K), annex (size: 5.13M), references (size: 63K), Ph. D. Thesis, Taufik Abrão, 4/2001. This work investigates new MuD structures for mobile DS-CDMA (Direct Sequence-Code Division Multiple Access) communication systems in AWGN (Additive White Gaussian Noise) and flat fading Rayleigh channels combining non-linear Interference Cancellers (IC) to two types of multirate access schemes: Multiple Processing Gain (MPG) and Multiple Codes (MC). The original contributions of this work related to new MuD structures for high capacity acting in a multirate scenario can be synthesized as: 1- Proposal and performance determination for five new MuD structures based on multistage parallel and hybrid interference cancellation schemes which detect DS-CDMA signals with different information rates; 2- Development of an analytical model for multistage Parallel Interference Cancellers (PIC) performance determination with hard and tanh decision detectors in AWGN and flat fading Rayleigh channels; 3- Comparison of linear and non-linear decision detectors for multistage PIC based receivers in a single rate scenario in AWGN and flat fading Rayleigh channels from extensive Monte Carlo simulation.
ESQUEMAS DE MULTITAXA PARA SISTEMAS CDMA DE BANDA LARGA (size: 996K), M.S. Dissertation, André Fagundes da Rocha, 10/2002. This work investigates DS-CDMA cellular systems, which adopt multi-rate schemes, based on multiple modulation formats, multiple processing gains or multiple spreading codes. The work covers the description and modeling of these systems; a performance analysis with the development of error bit probability expressions for AWGN and frequency-selective Rayleigh fading channels; and the evaluation of interferent power as a function of path loss model, cellular architecture and geometry, and users distribution over the cells. Finally, the three systems are compared, and advantages and disadvantages of each one are shown. This comparison includes a performance analysis where two-application systems are investigated. It is shown that multi-code systems have the same performance of multi processing-gain systems, while multi-modulation systems have poor performance at high bit rates.
ESTRUTURAS ESPAÇO-TEMPORAIS DE MÚLTIPLAS ENTRADAS E MÚLTIPLAS SAÍDAS PARA A TRANSMISSÃO DE DADOS DE ALTA TAXA EM SISTEMAS W-CDMA (size: 2.9M), Ph. D. Thesis, Ivan Roberto Santana Casella, 3/2004. Future wireless communication systems promise to offer a wide variety of multimedia services. However, the perspectives of a great demand by the new services, and the characteristics of demanded QoS, make essential the use of high capacity systems with high-speed wireless access, motivating the development and the use of new technologies. In the last few years, several structures based on recent advances in the signal processing area have been proposed to reduce the fading effects caused by the radio propagation channel and the different types of wireless communication interference, thus enabling an increase of system capacity and of wireless access speed. Traditionally, space diversity is one of the most used techniques to combat fading, while beamforming is one of the more effective techniques for interference suppression. Space diversity, typically implemented by multiple transmit and/or receive antenna arrays, stands out for enabling a reduction of the channel fading effects without necessarily sacrificing precious frequency band resources. Beyond this, as demonstrated recently, multiple transmit and receive antenna arrays allow a significant increase in system capacity. On the other hand, beamforming considers that multipath components of the desired signal and of the interfering signals happen about the receiver with different angles, allowing an antenna array to explore this signature space, through the adjustment of the radiation pattern of the antenna array, to improve the desired signal and to cancel the interfering signals. Attending to the requisites of larger capacity and higher rates, indispensable for future wireless communication systems, we have proposed and analyzed in this thesis different transmit and receive structures based on the use of antenna arrays and coding techniques. We considered both the uplink and the downlink of some different wireless communication systems, enabling both the reduction of interference, and improvement of SNR, by exploiting different forms of diversity.
RECEPTORES RAKE EM CANAIS COM DESVANECIMENTOS RÁPIDOS E SELETIVOS EM FREQÜÊNCIA PARA SISTEMAS DS-CDMA (size: 2.24M), M. S. Dissertation, Elvis Miguel Galeas Stancanelli, 07/2004. One of the main causes that degrade the performance of mobile communication systems is the signal fading due to the channel characteristics variations. In this context, diversity techniques consist in a very usual solution for CDMA systems. The Time RAKE receiver earns eminence in the midst of diversity techniques, whose theory was presented about half century ago, and already implemented in the first DS-CDMA standard (IS-95). Nevertheless, in its original conception a very slow fading channel was assumed, which don't always reflects the reality. As choice to the non-coherent version, it is possible to exploit the signal envelope variations as another form of diversity, which treats the fast channels through a signal processing: it is the Doppler diversity. In this dissertation, the joint multipath Doppler diversity is founded and analyzed, and the Time-frequency RAKE receiver is defined and implemented through the STFT. The signal-to-noise ratio gain with the Doppler diversity can be about 17dB for a bit error rate of 10-4 in a scenario characterized by a normalized Doppler shift around the unity. The STFT window length can be adjusted to improve the Doppler diversity and it can be stated that a large number of Doppler sub-channels with similar energies is the ideal scenario. An expression that provides an approximation for this energy allocation was also deduced. Additionally, the Doppler diversity for some examples considering unicellular systems was evaluated, via Monte Carlo simulations. Finally, two additional schemes were also considered: (i) the multicode in order to improve the Doppler diversity, preserving the information transmission rate; (ii) and an interference canceling algorithm for the parallel channels decoupling (channels created by the adopted multirate scheme). Despite its larger computational complexity, in comparison with the traditional Time RAKE approach, the Time-frequency RAKE receiver can be seen as an attractive alternative that would deserve more research works.
MODELAGEM COMPUTACIONAL DE CANAIS DE COMUNICAÇÃO MÓVEL (size: 4.77M), M. S. Dissertation, Vanderlei Aparecido da Silva, 10/2004. Computational modeling is a powerful and widely used tool for research in mobile communication systems. In such systems, the communication channel modeling is an indispensable factor, because its mobility and propagation characteristics can cause distortion over the transmitted waveform. This work contains the main mathematical and computing communication channel models. A historical cover is provided, which presents the nature of the problem and the initial modeling of the fading phenomenon. On the other hand, recent models are presented, which are mathematically effective and computationally efficient. One contribution of this work is the proposal of a new fading channel computational model, which was suitably tested and validated. The presented models were mathematically analyzed through its statistical properties. From numerical and computational point of view, the models were analyzed through several simulations. The main conclusion, from analytical and simulated results, shows that two models using frequency filtering are the best choice for the generation of multiple uncorrelated Rayleigh fading waveforms, where one of them is the new proposed model. This work can help mobile communications researchers to suitably model the communication channel in a computer simulation.
SISTEMAS CDMA MULTIPORTADORA (size: 2.35M), M. S. Dissertation, Bruno Augusto Angélico, 5/2005. Multicarrier CDMA systems have been considered as good candidates to integrate one of the fourth generation wireless mobile communications standards, mainly because they are relatively robust to the degrading effects of a mobile communication channel with high transmission rates. The present work brings a comparative performance study of three multicarrier CDMA systems: MC-CDMA, MC DS-CDMA orthogonal and MT-CDMA. The results presented here are obtained analytically according to some developments found in the literature and also by Monte Carlo simulation. The MC-CDMA system had the best result in terms of bit error rate. However, it is important to point out that such conclusion limits to the configurations used and the simplifications adopted to obtain the systems performance.
METODOLOGIAS DE SELEÇÃO DE SEQÜÊNCIAS DE ESPALHAMENTO PARA SISTEMAS DS/CDMA QUASE SÍNCRONOS (size: 2.04M), M. S. Dissertation, André Seichi Ribeiro Kuramoto, 5/2005. This work presents a study on some proposed methods of obtaining families of appropriate sequences for the spreading function in QS-CDMA systems. In this study, binary and poliphase sequences and a family of ternary sequences recently proposed in the literature are considered. Special attention is given to the families of binary sequences. For some of these families, performance illustrations are presented in terms of bit error rate for a QS-CDMA mobile communication system with conventional reception in Rayleigh fading channel. Such illustrations aid the evaluation of these families of binary sequences. In the literature they are found few works on appropriate sequences to QS-CDMA systems with variable data rates (multirate). In this work, it was evaluated the use of the binary sequences previously studied in a multirate QS-CDMA system with multiple code scheme. For the multirate QS-CDMA system with multiples processing gains a methodology of sequence selection was proposed. The conclusions of this work involve the classification of the methodologies of obtaining the families of sequences in terms of: complexity of the method, characteristic of the resulting families of sequences, proportionate performance in a QS-CDMA system and the applicability in a multirate QS-CDMA system.
Análise do Controle de Potência Aplicado ao Canal Reverso de Sistemas DS-CDMA (size: 11.7M) , M. S. Dissertation, Tadeu Júnior Gross, 7/2005. This dissertation deals with the Verhulst continuous dynamic model is used, that was elaborated initially to describe the biological species population growth with food and physical space restrictions, in order to synthesize a new DPCA (Distributed Power Control Algorithm) applicable in Direct Sequence Code Division Multiple Access (DSCDMA) systems. The associated differential equation is discretized via the Euler method, originally used for numerical integration. Properties of this recursive algorithm, as the Euclidean distance of optimum power vector distance and convergence velocity, are investigated via simulation. Numerical results are used in order to compare the performance against two other classic DPCA algorithms: the Foschini and Miljanic, and the sigmoidal of Uykan and Koivo. With estimation errors the proposed DPCA has presented smaller discrepancy in comparison with the optimum vector and also a better convergence velocity. Additionally the Gerschgorin Circles (GC) theory was applied for the determination of sufficient conditions for the allocation problem feasibility.
Estimativa de parâmetros de canal para DS-CDMA baseada na decomposição em subespaços (size 1.26M) , M. S. Dissertation, Paulo José Garcia Guimarães, 8/2005. With the development of techniques that increase DS-CDMA capacity as MuD, it is growing the need of accurate channel parameters estimation (signal strength, propagation delays and carrier phase). Some articles suggest subspace-based techniques for these parameters determination; however, papers presented so far are focusing on algorithms development while less attention is given to the analysis of limits and sensitivity. The objective of this dissertation is to work on performance and sensitivity analysis of one proposed algorithm based on subspace decomposition, focusing on practical utilization, in order to point vulnerabilities and suggest changes that increase algorithm performance.
Proposta de transmissão de dados em redes de telefonia celular CDMA2000 (size: 1.1 M); M. S. Dissertation, Ediclei Alves de Oliveira, 9/2006. Mobile telephony systems have been constantly asked for new demands of value added services. Voice traffic only is not enough anymore to support the new needs of mobile users because nowadays they ask for fast, cost-efficient, cheap and mobile services to support electronic mail, videoconference or Internet access. This work presents a method of how to determine minimum rates on traffic channels to support these services. Considering CDMA2000 technology, an impact analysis will be made in the air interface for these specific traffic channels. Same analysis will be made when minimum or maximum rates are reserved for each user, also comparing the time needed for data transmission, efficiency of the cell (useful rate / maximum rate) and others. The conclusions of this work may allow strategies to support data users in mobile telephony networks in such different ways, as better cost-effective solution, specific segment of the market (i.e., to concentrate in services with higher or lower transmission rates) or even to foresee the amount of resources needed in a network to support a forecasted number of users.
Sistemas de banda ultralarga com pré-processamento (Size: 2,4 M), Ph.D. Thesis, Bruno Augusto Angélico, 6/2010. The channel impulse response of a typical ultra wideband system is characterized by a large number of resolvable paths. For a efficient reception, the energy spread over the multipath components has to be somehow combined. Considering the downlink of a wireless personal area network, the access point is assumed to have a good hardware capacity when compared to the portable devices of the network, such as digital cameras, cell phones and mp3 players. This work focuses on preprocessing schemes that are able to combine efficiently the multipath components, and to combat self and multiuser interference without increasing the computational cost at the receiver (portable devices) substantially. Hence, most of the complexity is transferred to the transmitter (access point) in such a way that the receiver needs only a conventional detector or a conventional detector followed by a moderated complexity processing in order to mitigate the residual interference.
Otimização Multidimensional Baseada em Heurísticas Aplicada aos Sistemas de Comunicação Sem Fio (Size: 6,4 M), Ph.D. Thesis, Fernando Ciriaco Dias Neto, 03/2012. This work will perform a systematic, integrated and iterative research of heuristic algorithms applied to parameter estimation and multiuser detection problems, considering the performance x 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.
EFICIÊNCIA ENERGÉTICA E CAPACIDADE: ESTRATÉGIAS DE ALOCAÇÃO DE RECURSOS EM REDES SEM FIO DE MÚLTIPLO ACESSO (Size: 4.76 Mb). Ph.D. Thesis, Lucas Dias Hiera Sampaio, 05/2015. This work investigates the spectrum and power allocation problems in wire-less multiple access networks and seven different solutions to different scenarios and topologies, which are enumerated as follows. Three distinct solutions are presented to the energy efficiency maximization problem in multicarrier direct sequence code division multiple access cooperative: two game theoretic approaches, one using the iterative water-filling algorithm (1) and another one using the distributed power control algorithm based on Verhulst equilibrium concept (2), and a third solution also based on the last algorithm but considering the average channel power gain (3); an heuristic approach using the firefly algorithm (4) and the particle swarm optimization algorithm (5). In orthogonal frequency division multiple access networks, optimization problems considering a statistical quality of service metric were analyzed: the first one is the effective capacity maximization, which was solved through Lagrange dual decomposition method (6). The second one, in which the objective is to maximize the effective energy efficiency was addressed and solution based on the Dinkelbah method and further application of Lagrange dual decomposition was developed (7). Simulations were conducted to verify the proposed approaches performance and, whenever possible, the numerical results were compared to previous solution proposed in the literature.