International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / The decorrelating detector can afford good data estimates because it does not need to know many parameters of the received signal. However, it shows great performance deprivation when the background noise is high. On the other hand, partial parallel interference canceller(PPIC) has the potential to combat the near-far problem and have much lower computation complexity. But its performance depends on the initial data estimate. An improved PPIC scheme is proposed in this paper to combat the near-far problem. It utilizes the advantages of the two detectors by combining them. The focus of this paper is on the BER performance and the near-far resistance capability of the proposed scheme. Computer simulations demonstrate that the proposed detector has good BER performance and near-far resistance capability.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The impact of multipath fading parameters on the probability of error for Offset QPSK (OQPSK) is derived. The multipath fading channel is modeled using the aeronautical telemetry channel model [1-2]. Expressions for the probability of bit error are derived that are a function of the multipath model parameters. The expressions are shown to agree with computer simulations and show that a strong multipath reflection with a short delay causes much more degradation than a weak multipath reflection with a long delay.

Nowadays most of the communications systems are designed considering only to work under AWGN (Additive White Gaussian Noise). But the implementation of wireless systems in industrial facilities brings different kind of interference from machines or any other kind of electronic devices. Some of them are sources of randomly and high power noise, which commonly is known as impulsive noise. The objective in this thesis is to study the impact of the impulsive noise on a communication using QAM (Quadrature Amplitude Modulation) and PSK (Phase-Shift Keying) schemes, by observing the BER (Bit Error Rate) and the APD (Amplitude Probability Distribution). For that, it is developed a measurement method that will be used in a real industrial environment in future work.      The content of this thesis is divided in two parts. In the first part is made a program in MATLAB to simulate the communication through a noisy channel. Then is developed a measurement method which is tested in three different ways corresponding to 3 different outputs of an spectrum analyzer, namely, 20,4 MHz IF output, video output and IQ data output.      The relation of impulsive noise is presented in the second part with different statistical properties in the BER and the APD, in the setup with the best performance. At the end of the thesis a concluding section summarizes the results obtained during the work and some lines of future work in a real industrial environment with the developed method.

A high throughput scalable decoder architecture, a tiling approach to reduce the complexity of the scalable architecture, and two low power decoding schemes have been proposed in this research. The proposed scalable design is generated from a serial architecture by scaling the combinational logic; memory partitioning and constructing a novel H matrix to make parallelization possible. The scalable architecture achieves a high throughput for higher values of the parallelization factor M. The switch logic used to route the bit nodes to the appropriate checks is an important constituent of the scalable architecture and its complexity is high with higher M. The proposed tiling approach is applied to the scalable architecture to simplify the switch logic and reduce gate complexity. The tiling approach generates patterns that are used to construct the H matrix by repeating a fixed number of those generated patterns. The advantages of the proposed approach are two-fold. First, the information stored about the H matrix is reduced by onethird. Second, the switch logic of the scalable architecture is simplified. The H matrix information is also embedded in the switch and no external memory is needed to store the H matrix. Scalable architecture and tiling approach are proposed at the architectural level of the LDPC decoder. We propose two low power decoding schemes that take advantage of the distribution of errors in the received packets. Both schemes use a hard iteration after a fixed number of soft iterations. The dynamic scheme performs X soft iterations, then a parity checker cHT that computes the number of parity checks in error. Based on cHT value, the decoder decides on performing either soft iterations or a hard iteration. The advantage of the hard iteration is so significant that the second low power scheme performs a fixed number of iterations followed by a hard iteration. To compensate the bit error rate performance, the number of soft iterations in this case is higher than that of those performed before cHT in the first scheme.

No description available.

Ce travail de recherche est basé sur la technologie Ultra Large Bande (ULB), en particulier pour des applications bas débit (standard IEEE 802.15.4) tels que les réseaux de capteurs, les transmissions WPAN ou encore WBAN. La modélisation et la conception d’un récepteur non cohérent ULB pour les communications radio impulsionnelles ont été réalisées. Un des facteurs les plus importants dans les communications ULB est la sensibilité du récepteur, qui détermine la portée de transmission maximale. Un autre facteur aussi important est la consommation d’énergie qui influence directement la durée de vie de la source d’alimentation (batterie). Dans ce contexte, nous présentons dans le chapitre I une introduction sur la technologie ULB et ses diverses applications. Le chapitre II présente la modélisation au niveau système ainsi que d’une étude comparative des récepteurs non cohérents basés sur la détection d’énergie et la pseudo-Détection d’énergie. Dans le chapitre III sont présentés la méthode de conception et de réalisation d’un récepteur non cohérent ULB dans la bande de 3-5 GHz, ainsi que les résultats de mesure et ses performances en termes de sensibilité et de consommation d’énergie. Finalement, le chapitre IV présente une étude théorique sur les différents modes de fonctionnement du transistor MOS afin de mieux comprendre le fonctionnement de chaque bloc du récepteur. Cela permet de proposer de nouvelles architectures pour la détection d’énergie. Enfin, à partir de ces études nous réalisons l’optimisation du récepteur en termes de sensibilité et de consommation d’énergie. / This research is based on Ultra Wide Band (UWB) technology, in particularly for low-Rate applications such as sensor network, WPAN and WBAN (for the standard IEEE 802.15.4). The model and design of a non coherent receiver for UWB impulse radio communications has been completed. One of the most important factors in the UWB communications is the receiver sensitivity which determines the maximum transmission range. Another important factor is the energy consumption that determines the lifetime of the power source (battery). In this context, we present in Chapter I an introduction to UWB technology and its different applications. Chapter II deals with a modeling at the system level of non-Coherent receivers as well as a comparative study based on the energy detection and pseudo energy detection. In Chapter III is presented the method of design and implementation of a non-Coherent UWB receiver in the band of 3-5 GHz, as well as measurement results and performance in terms of sensitivity and power consumption. Finally, Chapter IV presents a theoretical study on the different modes of operation of the MOS transistor to understand the operation of each block of the receiver. This allows us to show the new architectures for energy detection and perform the optimization of receiver in terms of sensitivity and power consumption.

Yes / An assessment of the performance of OFDM transmissions over the wideband mobile radio channel is reported. The simulation in MATLAB /Simulink is based on the CODIT channel model. The results show that BER deteriorates significantly as the mobile velocities increase from 0 to 30 m/s. Significant variability in the BER for a given channel type is quantified. For a given instance of the channel the standard deviation of the estimated BER is 20%, but when averaged over many separate instances of the same channel type, a standard deviation of 47% is found.

No description available.

High-speed serial links in modern communication systems often require the Bit-Error-Rate (BER) to be at the level of 10 −12 or lower. From the industry perspective, major drawbacks in high volume production test for the serial links with low BER are the excessive test time for comparing each captured bit for error detection and costly instrumentation. In this thesis, we focus on developing a novel BER estimation methodology and its implementation. We propose a novel BER estimation methodology and an effective self-test system, which not only eliminates the usage of expensive measuring instruments, but also significantly reduces the test time. In the proposed BER estimation, we show that the total jitter (TJ) spectral information of a test SerDes is successfully estimated from the known TJ distribution of a golden SerDes. We propose a novel BER estimation formula that incorporates not only the TJ spectral information of the serial data, but also the TJ spectral information of the recovered clock. Our proposed estimation formula enables efficient BER estimation without excessive test time, and its accuracy does not depend on the jitter present in the serial data stream of the SerDes. The experimental results demonstrate that the test time for the proposed BER estimation is in the order of seconds, which translates to the test time savings of more than hundred times compared to the traditional BER measurement for the same accuracy. To implement the proposed BER estimation methodology, we have developed a novel time-to-digital converter (TDC). This design effectively measures the delay between two signals and converts it into the digital format. Performance of the TDC has been evaluated and presented using ModelSim and SPICE simulation. / Electrical and Computer Engineering

Os gliomas compreendem mais de 70% de todos os tumores cerebrais primários. Mesmo com tratamento agressivo, a média de sobrevivência relatada para estes tumores é geralmente menor do que 1 ano após o diagnóstico. A quimioterapia baseada em agentes alquilantes, como a temozolomida (TMZ), tem mostrado, em média, uma modesta resposta e pequeno aumento da sobrevida. As principais lesões causadas pela TMZ são os aductos N7-metil-G e N3-metil-A, que são processados pelo reparo por excisão de base (BER), compreendendo mais de 80% das lesões induzidas no DNA pela TMZ. Há evidência de que a resistência a este quimioterápico pode ser causada em parte por um eficiente processo de reparo via BER, mas poucos estudos têm focalizado essa abordagem. Metoxiamina (MX) é um inibidor do reparo via BER que tem sido atualmente investigado como um possível aliado no combate a vários tipos de tumores, aumentando os efeitos citotóxicos de drogas, tais como a TMZ. No presente trabalho, foram avaliadas as respostas celulares de células de glioblastoma (GBM) ao tratamento com a TMZ, associada ou não à MX. Foram analisados parâmetros como citotoxicidade (24 h, Kit XTT), sobrevivência celular (120 h, Kit XTT) e clonogênica (10 dias após o tratamento), danos no DNA pelo Ensaio Cometa (2, 6, 12 e 24 h), a indução de apoptose (24, 48 e 72 h) e alterações na expressão gênica e transcricional (24, 48 e 72h) de genes envolvidos na via de reparo por BER. Sob tratamento das linhagens de GBM (U87, U343, U251, U138 e T98G) a diferentes concentrações de TMZ (100 a 1000 M), o efeito citotóxico foi observado em células analisadas após 120 h, sendo que a linhagem T98G foi a mais resistente ao tratamento com TMZ e foi a única a apresentar diferenças significativas entre o tratamento sozinho e combinado (p 0,05). Assim, foi selecionada a linhagem T98G para os demais experimentos e estudar as possíveis vias implicadas na resistência a essa droga. A sobrevivência clonogênica das células T98G foi reduzida, sob tratamento com a TMZ (100 a 800 M), com diferença significativas para as concentrações superiores a 400 M. Observou-se que o efeito da TMZ foi acentuado quando associada ao inibidor, com diferenças significativas para todas as concentrações testadas. A droga induziu uma maior porcentagem de danos no DNA (Ensaio Cometa) para ambos os tratamentos (400 e 600 M) e nos tempos de 2 e 6 h, com diferenças significativas entre os tratamentos (TMZ e TMZ+MX), somente na concentração de 600 M/2 h. Entretanto esses danos se equipararam nos tempos seguintes. A indução de apoptose analisada nas células T98G mostrou a freqüência máxima de 24,2% no tempo de 72h, na concentração de 600 M de TMZ, enquanto que uma maior indução de apoptose (47,7%) foi observada para a mesma concentração no tratamento combinado (TMZ + MX), resultando em diferenças significativas. A análise de expressão gênica realizada para os genes APE1, FEN1 e XRCC1, mostraram que houve uma menor indução dos genes APE1 e FEN1 no tratamento combinado. A expressão da proteína APE1 (analisada por Western blot) foi menos intensa em todos os tempos de tratamento combinado (TMZ + MX), possivelmente pelo bloqueio dos sítios AP causado pelo inibidor MX. A proteína FEN1 mostrou-se menos expressa na comparação dos tratamentos, nos tempos de 48 e 72 h, indicando uma inibição de proteínas da via BER downstream à remoção de sítios AP por APE1, possivelmente pela ligação de MX. PCNA teve sua expressão protéica aumentada no tratamento combinado, nos tempos de 24 h, e principalmente em 48 h, sugerindo uma indução devida a um aumento de danos no DNA. Portanto, os resultados dos ensaios realizados com a associação da TMZ à MX demonstraram a influência do tratamento combinado sobre a expressão de proteínas envolvidas no reparo via BER, o que contribuiu para uma redução da capacidade proliferativa das células T98G em decorrência da maior indução de danos por aductos DNA-MX não reparados, resultando também em aumento de morte celular apoptótica. Esses dados mostram que a modulação do reparo via BER pode constituir uma estratégia promissora para aumentar a eficácia do tratamento com a TMZ, o que poderá futuramente embasar a escolha de procedimentos terapêuticos que resultem numa maior eficácia do tratamento de gliomas com agentes alquilantes. / Gliomas represent more than 70% of primary brain tumors. Even following an aggressive therapies, the mean survival rate of patients with these tumors is less than one year after diagnosis. Chemotherapy based on alkyklating agents, such as temozolomide (TMZ) has been reported to increase the survival rate. N7-metyl-G and N3-metyl-A adducts comprise more than 80% of the DNA lesions induced by TMZ and are processed by the base excision repair process (BER). There is evidence in the literature suggesting that the resistance to TMZ could be caused, in part, by an efficient repair by BER pathway, although few studies have focused on this subject. Metoxiamine (MX) is an effective BER inhibitor, which has been investigated as a conceivable treatment for different kinds of tumor, due to its synergistic effect with antitumoral drugs, such as TMZ. In the present study, the cellular responses to TMZ treatment associated or not with MX were evaluated in giloblastoma (GBM) cell lines. Several parameters were analyzed, such as cytotoxicity (24 h), cellular survival (120 h) and clonogenic efficiency (10 days after treatment), DNA damage and repair kinetics (after 2, 6, 12 and 24 h of recovery time), apoptosis induction (24, 48 and 72 h) and alterations in gene expression (24, 48 e 72h) for genes playing role in BER pathway. The treatment with TMZ 100 -1000 M (during 24 h) was cytotoxic for all GBM cell lines tested (U87, U343, U251, U138 and T98G), as analyzed after 120 h, with the T98G cell line being be the most resistant to TMZ; besides, T98G was the only one to present significant differences (p 0,05) in survival rates measured between TMZ treatment and TMZ combined with MX. Thus, T98G cells were selected for the subsequent experiments and for the study of the pathways implicated in TMZ resistance. The clonogenic efficiency of T98G cells was reduced under TMZ treatment (100 - 800 M) with significant differences for treatments above 400 M. In addition, the combined treatment TMZ plus MX significantly increased the cytotoxic effects, even for the lowest concentration. The comet assay showed higher percentage of DNA damage for both treatment modalities (TMZ and TMZ+MX) at 2 and 6 h of recovery, with significant differences between treatments for 2 h. Following 12 and 24 h of recovery, the amount of DNA damage reached the control levels, indicating the repair of DNA breaks. Apoptosis induction in T98G cells showed the highest frequency (24.2%) at 72h for 600 M TMZ, while the highest apoptosis induction (47.7%) was observed for the same concentration combined to MX. Quantitative gene expression analysis performed for three genes, APE1, FEN1 and XRCC1, showed a reduced expression of APE1 and FEN1 for the combined treatment. Western blot analysis demonstrated that APE1 was less expressed for all kind of treatments, probably due to AP-sites blockade caused by the inhibitor MX. In addition, FEN1 showed low levels of expression at 48h and 72h, indicating the inhibition of BER pathway downstream to the AP removal by APE1. On the other hand, PCNA expression was higher for the combined treatment (24h and mainly 48h), suggesting its induction probably due to increased DNA damage. Therefore, the present results demonstrated that the association of TMZ with MX interfered with the expression of proteins involved in BER, thus, reducing the clonogenic efficiency of T98G cells, probably as a consequence of the high production of unrepaired DNA-MX adducts, leading to cell death, including apoptosis. These data show that the modulation of BER is a promising strategy for magnifying the therapeutic impact of TMZ, and in the next future, this strategy may embrace the option to establish novel and efficient therapy protocols for the treatment of gliomas with alkylating agents.