Orientador: Celso de Almeida / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-09-11T21:24:05Z (GMT). No. of bitstreams: 1 CarvajalMora_HenryRamiro_M.pdf: 10096746 bytes, checksum: 558790b8f1575c8f3b46fe6c7418920d (MD5) Previous issue date: 2014 / Resumo: Neste trabalho, é avaliado o desempenho do enlace reverso de redes celulares que utilizam a técnica de múltiplo acesso por divisão de código com multiportadoras (MC-CDMA) em termos da probabilidade de erro de bit média (BER) e da eficiência espectral média. O sistema de comunicações analisado utiliza a técnica MC-CDMA, um arranjo linear de antenas na estação rádio base, entrelaçamento em frequência, combinação de máxima razão (MRC), modulação adaptativa, controle de potência e um prefixo cíclico grande o suficiente para eliminar os efeitos da interferência intersimbólica (ISI) e da interferência entre portadoras (ICI). O cenário estudado considera a presença de interferência de múltiplo acesso (MAI) e interferência de co-canal (CCI). A caracterização do canal considera a presença de ruído aditivo gaussiano branco (AWGN), perda de propagação exponencial e desvanecimento lento e seletivo em frequência que segue a distribuição de Rayleigh. Neste contexto, expressões analíticas exatas e fechadas para a BER média tanto para a modulação BPSK, quanto para a modulação M-QAM são obtidas. A exatidão das expressões é validada através de simulações de Monte Carlo. Ademais, uma expressão para a eficiência espectral celular média é determinada, a qual é uma função do fator de reuso de canais, do incremento da largura de banda devido ao prefixo cíclico, do carregamento do sistema, do fator de espalhamento, dos raios da célula e da modulação utilizada. Os resultados indicam que utilizar um fator de reuso de canais de 1 é a maneira mais eficiente de usar o espectro. No entanto, esse fator de reuso é crítico em relação às taxas de transmissão. Ademais, evidenciando que a técnica de múltiplo acesso por divisão de frequências ortogonais (OFDMA) é um caso particular da técnica MC-CDMA, os resultados mostram que a máxima eficiência espectral média obtida com a técnica OFDMA é menor do que aquela obtida com a técnica MC-CDMA / Abstract: In this work the performance of cellular networks uplink is evaluated using the multicarrier-code division multiple access (MC-CDMA) technique in terms of the mean bit error rate (BER) and the mean spectral efficiency. The analyzed communications system is supposed to employ the MC-CDMA technique, a linear antenna array in the base station, frequency interleaving, maximal ratio combining (MRC), adaptive modulation, control power and a cyclic prefix large enough to eliminate the effects of intersymbol interference (ISI) and intercarrier interference (ICI). The studied scenario assumes the presence of multiple access interference (MAI) and co-channel interference (CCI). The channel characterizations considers the presence of additive white gaussian noise (AWGN), exponential path-loss and slow and frequency selective Rayleigh fading. In this context, exact and closed analytical expressions for the mean BER for both BPSK modulation, as for M-QAM modulation are obtained. The accuracy of the expressions is validated through Monte Carlo simulations. Also, an expression for the mean cellular spectral efficiency is determined, which is a function of the channel reuse factor, the bandwidth increases due to the cyclic prefix, the system load, the spreading factor, the cell radius and the modulation employed. The results show that using an unitary channel reuse factor of 1 is the most efficient way to use the spectrum. However, this reuse factor is critical in relation to transmission rates. Moreover, considering that the orthogonal frequency division multiple access (OFDMA) technique is a particular case of MC-CDMA, the results show that the maximum mean spectral efficiency achieved with the OFDMA technique is lower than that obtained with the MC-CDMA technique / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

Phase Shifters are one of the most important building cells of the applications in microwave and millimeter-wave range, especially for communications and radar applications / to steer the main beam for electronic scanning. This thesis includes all of the stages starting from the theoretical design stage to the measurements of the phase shifters. In detail, all-pass network phase shifter configuration is used to achieve broadband and ultra wide-band differential phase characteristics. For these reasons, 1 to 2 GHz, 2 to 4 GHz, and 3 to 6 GHz 4-bit, 22.5&deg / phase resolution phase shifter realization with surface micromachined lumped components are designed, simulated, fabricated and measured. Basic building blocks of the phase shifters, i.e., surface micromachined lumped components, square planar spiral inductors and Metal-Insulator-Metal capacitors are designed with EM simulation and lumped equivalent model extractions. The validation of the designed square planar spiral inductors is done with fabrication and measurement steps, very low error, below 1%, between the designs and fabricated samples are observed. Using this knowledge on lumped elements finally phase shifters are designed with surface micromachined lumped components, fabricated using an in house technology provided by METU-MEMS facilities, RF MEMS group. Low phase rms error, good return and insertion loss considerations are aimed, and achieved. In addition to the main work of this thesis, a generalized theoretical calculation method for 2n-1 number of stages all-pass network phase shifters is presented for the first time in literature. A different, new, broadband, and combined phase shifter topology using two-stage all-pass filters is presented. Moreover, the implementation of this idea is proved to be practical to 3 to 6 GHz 5.625&deg / and 11.25&deg / combined phase shifter. A new approach for stage numbers other than power of 2 is indicated, which is different from what is already presented in the literature. An example practical implementation results are provided for the three-stage 4-bit 1 to 6 GHz phase shifter. Also, a small improvement in SRF of the high inductance valued inductors is achieved with the mitering of the corners of square planar spiral inductors. Comparison of the measured data between the normal inductors and mitered versions shows that the first SRF of the inductors are increased about 80 MHz, and second SRF of the inductors are increased about 200 MHz.

University of Macau / Faculty of Business Administration / Department of Management and Marketing

Enhanced Data Rates for Global Evolution (EDGE) is one of the 3G wireless communication standards, which provides higher data rates by adopting 8-PSK modulation in TDMA system infrastructure of GSM. In this thesis, a turbo detection receiver for Enhanced General Packet Radio Services (EGPRS) system, which is the packet switching mode of EDGE, is studied. In turbo detection, equalization and channel decoding are performed iteratively. Due to 8-ary alphabet of EGPRS modulation, full state trellis based equalization, as usually performed in GSM, is too complex not only for turbo detection but even for conventional equalization / so suboptimum schemes have to be considered. The Delayed Decision Feedback Sequence Estimation (DDFSE) is chosen as suboptimal and less complex trellis based scheme and it is examined as a conventional equalization technique firstly. It is shown that the DDFSE has a fine tradeoff between performance and complexity and can be a promising candidate for EGPRS. Then it is employed to reduce the number of the trellis state in turbo detection. Max-log-MAP algorithm is used for soft output calculations of both SISO equalizer and SISO decoder. Simulation results illustrate that proposed turbo detection structure improves bit error rate and block error rate performance of the receiver with respect to the conventional equalization and decoding scheme. The iteration gain varies depending on modulation type and coding rate of Modulation Coding Scheme (MCS) employed in EGPRS.

Marketing, Direct Marketing, Tele-Marketing, Consumer Behavior, Tele-sales, Developing countries, Customer attitude/behavior, Call center, Outbound calls, Proactive telemarketing, Sales promotion ,Survey, Telemarketing center , Telemarketing sales , Telephone marketers , Cold calls.

Family conversation between homes is difficult to initiate at mutually agreeable times as neither participant has exact knowledge of the other's activities or intentions. Whether calling to plan an important family gathering or simply to connect with family members, the question is: Is now a good time to call? People expect friends and family to learn their activity patterns and to minimize interruptions when calling. Can technology provide awareness cues to the caller, even prior to the initiation of the call? This research focuses on sampling the everyday activities of home life to determine environmental factors, which may serve as an indicator for availability. These external factors may be effective for identifying household routines of availability and useful in determining when to initiate conversation across homes. Several workplace studies have shown a person's interruptibility can be reliably assessed and modeled from specific environmental cues; this work looks for similar predictive power in the home. Copresence, location, and activity in the home were investigated as correlates to availability and for their effectiveness within the social protocol of family conversation. These studies indicate there are activities that can be sensed, either in real-time or over some time span, that correlate to self-reported availability. However, the type and amount of information shared is dependent upon individual preferences, social accessibility, and patterns of activities. This research shows friends and family can improve their predictions of when to call if provided additional context, and suggests that abstract representations of either routines or explicit availability status is sufficient and may be preferred by providers. Availability prediction is feasible in the home and useful to those outside the home, but the level of detail to provide in particular situations needs further study. This work has implications for the development of groupware systems, the automatic sensing of activity to deal with interruption, and activity recognition in the home.

In this thesis, an algorithm for visual detecting and tracking of very low SNR targets, i.e. dim targets, is developed. Image processing of single frame in time cannot be used for this aim due to the closeness of intensity spectrums of the background and target. Therefore / change detection of super pixels, a group of pixels that has sufficient statistics for likelihood ratio testing, is proposed. Super pixels that are determined as transition points are signed on a binary difference matrix and grouped by 4-Connected Labeling method. Each label is processed to find its vector movement in the next frame by Label Destruction and Centroids Mapping techniques. Candidate centroids are put into Distribution Density Function Maximization and Maximum Histogram Size Filtering methods to find the target related motion vectors. Noise related mappings are eliminated by Range and Maneuver Filtering. Geometrical centroids obtained on each frame are used as the observed target path which is put into Optimum Decoding Based Smoothing Algorithm to smooth and estimate the real target path. Optimum Decoding Based Smoothing Algorithm is based on quantization of possible states, i.e. observed target path centroids, and Viterbi Algorithm. According to the system and observation models, metric values of all possible target paths are computed using observation and transition probabilities. The path which results in maximum metric value at the last frame is decided as the estimated target path.

Multi-user MIMO (MIMO-MU) communication techniques make use of available channel state information at the transmitter to mitigate the inter-user interference. The goal of these techniques is to provide the least interference at the mobile stations by applying a precoding operation. In this thesis a comparison of available techniques in the literature such as Channel Decomposition, SINR Balancing, Joint-MMSE optimization is presented. Novel techniques for the MIMO multi-user downlink communication systems, where a single stream is transmitted to each user are proposed. The proposed methods, different from the other methods in the literature, use a simple receiver to combat the interference. It has been shown that MRC based receivers are as good as more complicated joint MMSE receivers.

Low Density Parity Check (LDPC) codes are the parity check codes of long block length, whose parity check matrices have relatively few non-zero entries. To improve the performance at relatively short block lengths, LDPC codes are constructed by either pseudo-random or quasi-cyclic methods instead of random construction methods. In this thesis, pseudo-random code construction methods, the effects of closed loops and the graph connectivity on the performance of pseudo-random LDPC codes are investigated. Moreover, quasi-cyclic LDPC codes, which have encoding and storage advantages over pseudo-random LDPC codes, their construction methods and performances are reviewed. Finally, performance comparison between pseudo-random and quasi-cyclic LDPC codes is given for both regular and irregular cases.

In this study, a computer code is developed in MATLAB&reg / to compute the Radar Cross Section (RCS) of arbitrary shaped complex targets by using Physical Optics (PO) and Modified PO. To increase the computational efficiency of the code, a novel fast integration procedure for oscillatory integrals, called Levin&rsquo / s integration, is applied to PO integrals. In order to improve the performance of PO near grazing angles and to model diffraction effects, a method called PO with Modified Surface Normal Vectors is implemented. In this method, new surface normals are defined to model the diffraction mechanism. Secondary scattering mechanisms like multiple scattering and shadowing algorithms are also included into the code to obtain a complete RCS prediction tool. For this purpose, an iterative version of PO is used to account for multiple scattering effects. Indeed, accounting for multiple scattering effects automatically solves the shadowing problem with a minor modification. Therefore, a special code for shadowing problem is not developed. In addition to frequency domain solutions of scattering problems, a waveform analysis of scattered fields in time domain is also comprised into this thesis. Instead of direct time domain methods like Time Domain Physical Optics, a Fourier domain approach is preferred to obtain the time domain expressions of the scattered fields. Frequency and time domain solutions are obtained for some simple shapes and for a complex tank model for differently polarized incident fields. Furthermore, a statistical analysis for the scattered field from the tank model is conducted.