With the rapid evolving IT technologies, today, the power factor correction (PFC) design is facing many challenges, such as power scalability, high entire-load-range efficiency, and high power density. Power scalability is a very desirable and cost-effective approach in the PFC design in order to keep up with servers' growing power requirements. Higher power density can eventually reduce the converter cost and allows for accommodating more equipment in the existing infrastructures. Driven strongly by economic and environmental concerns, high entire-load-range efficiency is more and more required by various organizations and programs, such as the U.S. Energy Star, Climate Savers, and German Blue Angel. Today, the existing boost PFC is reaching its limitations to meet these challenges simultaneously. Using the cutting-edge semiconductor devices, further efficiency improvement at light load is still needed. There are limited approaches available for increasing the power density due to the large EMI filter and inductor size. Interleaved multi-channel boost PFC is a promising candidate to meet those challenges, but the interleaved boost converter is a less explored area. On the other hand, the multi-channel interleaved buck converter for the VR application has been intensively studied and thoroughly explored. One basic approach of this study is trying to extend the existing knowledge and techniques obtained from multiphase buck converters to the multi-channel interleaved boost converters since there are similarities existed between the multi-phase buck and the multi-channel boost converters. The existing studies about the interleaving impact on the EMI filter design are based on the time domain ripple cancellation effect. This approach is good enough for most of the filter designs. However, unlike the conventional filter designs, the EMI filter design is a specification related process. Both the EMI standard and the EMI measurement are based on the frequency domain spectrum. Limited by the existing analysis approaches, it is difficult to provide a clear picture about how exactly the multi-channel interleaving will impact the EMI filter design. The interleaving impact on the Common Mode (CM) noise also has not been studied in any existing literatures for the same reason. In this study, the frequency domain analysis method was adopted. With the double Fourier integral transformation, a closed-form expression of all the harmonics of the noise sources can be obtained. With all the detailed phase relationship of the switching frequency harmonics and all the side band harmonics, the multi-channel interleaving impact on both the differential mode (DM) and CM filter design can be clearly understood and summarized. According to the design curves provided, the EMI filter size can be effectively reduced by properly choosing the interleaving channel number and the switching frequency. The multi-channel interleaving impact on the output capacitor current ripple is also studied and summarized in this dissertation. It should be pointed out that interleaving only reduces the total input and output current ripples; the inductor current in each channel still has large ripple if small inductance is used. Similar to the multi-phase buck converter, coupling inductors result in different equivalent inductances for input current ripple and inductor current ripple for boost converters. Keeping the inductor current ripple magnitude the same, inverse coupling inductors between the interleaved channels can reduce the inductor size. However, the DM filter size is increased due to larger input current. Based on the investigation on the total magnetic component weight, inverse coupling inductor can reduce the total magnetic component weight. The reduction is more pronounced for lower switching frequency design when the inductor size is dominating among the total magnetic components. Based on the harmonic cancellation, and with all the detailed phase relationship of the switching frequency harmonics and all the side band harmonics, a novel phase angle control method is proposed to maximize the reduction of the EMI filter. For example, in a 2-channel interleaved PFC, just by changing the interleaving scheme to 90 degree phase shift, 39% total volume reduction of the EMI filter can be achieved. The proposed phase angle controlled multi-channel PFC is experimentally demonstrated and verified on a digital controlled 4-channel PFC. The phase angle control method proposed in the multi-channel boost converter can be applied back to the multi-phase buck converter as well. The harmonic cancellation principle will be the same as the multi-channel boost converter. The same benefits can be obtained when the requirement is defined in the frequency domain, e.g. the EMI Standard. The interleaved multi-channel configuration makes it possible to implement the phase-shedding to improve the PFC light load efficiency. By decreasing the number of active channels according to the load, the PFC light load efficiency can be optimized. However, shedding phases can reduce the ripple cancellation effect as well, which will result in the EMI noise increase and losing the benefit on the EMI filter. By applying the proposed phase-shedding with phase angle control strategy, the phase shedding impact on the EMI filter design can be minimized. The light load efficiency can be improved without compromising the EMI filter size. Then, adaptive frequency controlled PFC is proposed to further improve the PFC light load efficiency. The proposed light load efficiency improvement strategies are combined and implemented on the platform of the digital controlled 4-channel PFC. The benefit of improving the light load efficiency is experimentally verified. The EMI performance is also evaluated with the EMI measurement results obtained from the PFC prototype. Following the same approach explored, the benefits of interleaved boost converter can be further extended other applications, such as the boost converter in the Hybrid Electric Vehicles (HEV) and photovoltaic (PV) system. / Ph. D.

Advances in transistor-integration technology and multi-core technology of the latest microprocessors have driven transient requirements to become more and more stringent. Rather than relying on the bulky output capacitors as energy-storage devices, increasing the control bandwidth (BW) of the multiphase voltage regulator (VR) is a more cost-effective and space-saving approach. However, it is found that the stability margin of current-mode control in high-BW design is very sensitive to operating conditions and component tolerance, depending on the performance of the current-sensing techniques, modulation schemes, and interleaving approaches. The primary objective of this dissertation is to investigate an advanced multiphase current-mode control, which provides accurate current sensing, enhances the stability margin in high-BW design, and adaptively compensates the parameter variations. Firstly, an equivalent circuit model for generic current-mode controls using DCR current sensing is developed to analyze the impact of component tolerance in high-BW design. Then, the existing state-of-the-art auto-tuning method used to improve current-sensing accuracy is reviewed, and the deficiency of using this method in a multiphase VR is identified. After that, enlightened by the proposed model, a novel auto-tuning method is proposed. This novel method features better tuning performance, noise-insensitivity, and simpler implementation than the state-of-the-art method. Secondly, the current state-of-the-art adaptive current-mode control based on constant-frequency PWM is reviewed, and its inability to maintain adequate stability margin in high-BW design is recognized. Therefore, a new external ramp compensation technique is proposed to keep the stability margin insensitive to the operating conditions and component tolerance, so the proposed high-BW constant-frequency control can meet the transient requirement without the presence of bulky output capacitors. The control scheme is generic and can be used in various kinds of constant-frequency controls, such as peak-current-mode, valley-current-mode, and average-current-mode configurations. Thirdly, an interleaving technique incorporating an adaptive PLL loop is presented, which enables the variable-frequency control to push the BW higher than proposed constant-frequency control, and avoids the beat-frequency input ripple. A generic small-signal model of the PLL loop is derived to investigate the stability issue caused by the parameter variations. Then, based on the proposed model, a simple adaptive control is developed to allow the BW of the PLL loop to be anchored at the highest phase margin. The adaptive PLL structure is applicable to different types of variable-frequency control, including constant on-time control and ramp pulse modulation. Fourthly, a hybrid interleaving structure is explored to simplify the implementation of the adaptive PLL structure in an application with more phases. It combines the adaptive PLL loop with a pulse-distribution technique to take the advantage of the high-BW design and fast transient response without adding a burden to the controller implementation. As a conclusion, based on the proposed analytical models, effective control concepts, systematic optimization strategies, viable implementations are fully investigated for high-BW current-mode control using different modulation techniques. Moreover, all the modeling results and the system performance are verified through simulation with a practical output filter model and an advanced mixed-signal experimental platform based on the latest MHz VR design on the laptop motherboard. In consequence, the multiphase VRs in future computation systems can be scalable easier with proposed multiphase configurations, increase the system reliability with proposed adaptive loop compensation, and minimize the total system footprint of the VR with the superior transient performance. / Ph. D.

El uso combinado de diversidad en el dominio temporal, frecuencial y espacial constituye una valiosa herramienta para mejorar la recepción de servicios de difusión móviles. Gracias a la mejora conseguida por las técnicas de diversidad es posible extender la cobertura de los servicios móviles además de reducir la infraestructura de red. La presente tesis investiga el uso de técnicas de diversidad para la provisión de servicios móviles en la familia europea de sistemas de difusión terrestres estandarizada por el prpoyecto DVB (Digital Video Broadcasting). Esto incluye la primera y segunda generación de sistemas DVB-T (Terrestrial), DVB-NGH (Handheld), y DVB-T2 (Terrestrial 2nd generation), así como el sistema de siguiente generación DVB-NGH. No obstante, el estudio llevado a cabo en la tesis es genérico y puede aplicarse a futuras evoluciones de estándares como el japonés ISDB-T o el americano ATSC. Las investigaciones realizadas dentro del contexto de DVB-T, DVB-H y DVBT2 tienen como objetivo la transmisión simultánea de servicios fijos y móviles en redes terrestres. Esta Convergencia puede facilitar la introducción de servicios móviles de TB debido a la reutilización de espectro, contenido e infraestructura. De acuerdo a los resultados, la incorporación de entrelazado temporal en la capa física para diversidad temporal, y de single-input multiple-output (SIMO) para diversidad espacial, son esenciales para el rendimiento de sistemas móviles de difusión. A pesar de que las técnicas upper later FEC (UL-FEC) pueden propocionar diversidad temporal en sistemas de primera generación como DVB-T y DVB-H, requieren la transmisión de paridad adicional y no son útiles para la recepción estática. El análisis en t�ñerminos de link budjget revela que las técnicas de diversidad noson suficientes para facilitar la provision de servicios móviles en redes DVB-T y DVB-T2 planificadas para recepción fija. Sin embargo, el uso de diversidad en redes planificadas para recepción portable / Gozálvez Serrano, D. (2012). Combined Time, Frecuency and Space Diversity in Multimedia Mobile Broadcasting Systems [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/16273

No / Orthogonal frequency division multiplexing (OFDM) is pronounced in wireless communication systems. Methods for improving the performance of the OFDM-based systems are mostly sought. A method of doing this involves error correction coding and another, a better multicarrier modulation kernel. In this work, convolutional error correction coding with interleaving is introduced in wavelet multicarrier modulation OFDM system (wavelet-OFDM) to improve the performance of multicarrier systems as the signal traverses the multipath and noisy transmission channels. This is compared with FFT-based multicarrier modulation (FFT-OFDM). Results show that coded wavelet-OFDM saves more than a half of the transmit power than the uncoded wavelet. Also it will be shown that, the interleaved and non-interleaved coded wavelet-OFDM well outperform interleaved coded and non-interleaved coded FFT-OFDM systems respectively.

High power multi-level converters are deemed as the mainstay power conversion technology for renewable energy systems including the battery storage system, PV farm and electrical vehicle charge station. This thesis is focused on the study of three-level DC/DC converter with multi-phase interleaved structure, with coupled and integrated magnetics to achieve high power density. The proposed interleaved phased legs offer the benefit of output current ripple reduction, while inversed coupled inductors can suppress the circulating current between phase legs. Compared with conventional non-interleaving three-level DC/DC converter with non-coupling inductors, both inductor current ripple and output current ripple are largely reduced by interleaving with inverse-coupled inductors. Because of the non-linearity of the inductor coupling, the equivalent circuit model is developed for the proposed interleaving structure. The model identifies the existence of multiple equivalent inductances during one switching cycle. A combination of them determines the inductor current ripple and dynamics of the system. By virtue of inverse coupling and means of controlling the coupling coefficients, one can minimize the current ripple and the unwanted circulating current. To further reduce the magnetic volume, the four inductors in two-phase three-level DC/DC converter are integrated into one common structure, incorporating the negative coupling effects. The integrated magnetic structure can effectively suppress the circulating current and reduce the inductor current ripple and it is easy to manufacture. This thesis provides an equivalent circuit model to facilitate the design optimization of the integrated system. A prototype of integrated coupled inductors is assembled with nano-crystalline C-C core and powder block core. It is tested with both impedance analyzer and single pulse tester, to guarantee proper mutual inductance for inductor current ripple and output current ripple target. With a two-phase three-level DC/DC converter hardware, the concept of integrated coupled inductors is verified, showing its good performance in high-voltage, high-power conversion applications. / Master of Science / With the demanding energy consumption globally, there is an increasing trend for the requirement of high efficiency power converters with high power density. The application for renewable energies including the PV farm, battery storage system and electrical vehicle become more and more important for the sustainable development of society. High-power, high-voltage DC/DC converters can fulfill the role for such renewable energy power conversion. In this paper, a multi-phase multi-level DC/DC converter solution suitable for high-power, high-voltage application is analyzed and designed. With the techniques including interleaving operation and inverse coupled inductors, the power density for the power conversion is increased while keeping a high system efficiency. The discussed power converter in this thesis demonstrated a solution for high-power, highvoltage DC/DC power conversion with high efficiency. And the concept is verified with real hardware experimental results, showing its good performance for a 200kW power conversion system.

The main objective of this thesis is to provide a smooth video playout on the mobile device over wireless networks. The parameters that specify the wireless channel include: bandwidth variation, frame losses, and outage time. These parameters may affect the quality of the video negatively, and the mobile users may notice sudden stops during the playout video, i.e., the picture is momentarily frozen, followed by a jump from one scene to a different one. This thesis focuses on eliminating frozen pictures and reducing the amount of video data that need to be transmitted. In order to eliminate frozen scenes on the mobile screen, we propose three different techniques. In the first technique, the video frames are split into sub-frames; these sub-frames are streamed over different channels. In the second technique the sub-frames will be “crossed” and sent together with other sub-frames that are from different positions in the streaming video sequence. If some sub-frames are lost during the transmission a reconstruction mechanism will be applied on the mobile device to recreate the missing sub-frames. In the third technique, we propose a Time Interleaving Robust Streaming (TIRS) technique to stream the video frames in different order. The benefit of that is to avoid losing a sequence of neighbouring frames. A missing frame from the streaming video will be reconstructed based on the surrounding frames on the mobile device. In order to reduce the amount of video data that are streamed over limited bandwidth channels, we propose two different techniques. These two techniques are based on identifying and extracting a high motion region of the video frames. We call this the Region Of Interest (ROI); the other parts of the video frames are called the non-Region Of Interest (non-ROI). The ROI is transmitted with high quality, whereas the non-ROI is interpolated from a number of references frames. In the first technique the ROI is a fixed size region; we considered four different types of ROI and three different scenarios. The scenarios are based on the position of the reference frames in the streaming frame sequence. In the second technique the ROI is identified based on the motion in the video frames, therefore the size, position, and shape of the ROI will be different from one video to another according to the video characteristic. The videos are coded using ffmpeg to study the effect of the proposed techniques on the encoding size. Subjective and objective metrics are used to measure the quality level of the reconstructed videos that are obtained from the proposed techniques. Mean Opinion Score (MOS) measurements are used as a subjective metric based on human opinions, while for objective metric the Structural Similarity (SSIM) index is used to compare the similarity between the original frames and the reconstructed frames.

Recently, there has been a renewed interest in code based cryptosystems. Amongst the reasons for this interest is that they have shown to be resistant to quantum at- tacks, making them candidates for post-quantum cryptosystems. In fact, the National Institute of Standards and Technology is currently considering candidates for secure communication in the post-quantum era. Three of the proposals are code based cryp- tosystems. Other reasons for this renewed interest include e cient encryption and decryption. In this dissertation, new code based cryptosystems (symmetric key and public key) are presented that use high rate codes and have small key sizes. Hence they overcome the drawbacks of code based cryptosystems (low information rate and very large key size). The techniques used in designing these cryptosystems include random bit/block deletions, random bit insertions, random interleaving, and random bit ipping. An advantage of the proposed cryptosystems over other code based cryp- tosystems is that the code can be/is not secret. These cryptosystems are among the rst with this advantage. Having a public code eliminates the need for permutation and scrambling matrices. The absence of permutation and scrambling matrices results in a signi cant reduction in the key size. In fact, it is shown that with simple random bit ipping and interleaving the key size is comparable to well known symmetric key cryptosystems in use today such as Advanced Encryption Standard (AES). The security of the new cryptosystems are analysed. It is shown that they are immune against previously proposed attacks for code based cryptosystems. This is because scrambling or permutation matrices are not used and the random bit ipping is beyond the error correcting capability of the code. It is also shown that having a public code still provides a good level of security. This is proved in two ways, by nding the probability of an adversary being able to break the cryptosystem and showing that this probability is extremely small, and showing that the cryptosystem has indistinguishability against a chosen plaintext attack (i.e. is IND-CPA secure). IND-CPA security is among the primary necessities for a cryptosystem to be practical. This means that a ciphertext reveals no information about the corresponding plaintext other than its length. It is also shown that having a public code results in smaller key sizes. / Graduate

The GSM platform is a extremely successful wireless technology and an unprecedented story of global achievement. The GSM platform is growing and evolving and offers an expanded and feature-rich voice and data enabling services. General Packet Radio Service, (GPRS), will have a tremendous transmission rate, which will make a significant impact on most of the existing services. Additionally, GPRS stands ready for the introduction of new services as operators and users, both business and private, appreciate the capabilities and potential that GPRS provides. Services such as the Internet, videoconferencing and on-line shopping will be as smooth as talking on the phone. Moreover, the capability and ease of access to these services increase at work, at home or during travel. In this research the traffic channel of a GSM system was studied in detail and simulated in order to obtain a performance analysis. Matlab, software from Mathworks, was used for the simulation. Both the forward and the reverse links of a GSM system were simulated. A flat fading model was used to model the channel. Signal to Noise Ratio, (SNR), was the primary metric that was varied during the simulation. All the building blocks for a traffic channel, including a Convolutional encoder, an Interleaver and a Modulator were coded in Matlab. Finally the GPRS system, which is an enhancement of the GSM system for data services was introduced.

Uno de los campos más importantes de la Electrónica de Potencia es el de los convertidores de potencia conmutados, que debido a sus características de alto rendimiento energético, reducido tamaño, posibilidades de regulación del factor de potencia y de elevación de tensión, etc., están presentes en un gran número de las etapas de alimentación de los equipos electrónicos actuales.Las mejoras tecnológicas en ámbitos como el de la integración de circuitos han permitido importantes reducciones en el tamaño de los equipos (por ejemplo en los ordenadores). Sin embargo, este proceso de reducción de tamaño que, además, suele venir unido a unas especificaciones más rígidas en cuanto a costes, rendimiento, seguridad y prestaciones en general, no se ha producido en igual medida en las etapas de alimentación. El estudio de los convertidores conmutados es por lo tanto un campo necesitado de esfuerzos de investigación y desarrollo.Para potencias superiores a 25 W, y especialmente en potencias superiores a 150 W, una de las estrategias utilizadas para mejorar las prestaciones de los convertidores es el uso del denominado "interleaving" o entrelazado , definido como la puesta en paralelo de N convertidores idénticos desfasando sus señales de control de forma uniforme a lo largo del periodo de conmutación.Con el objetivo principal de reducir al máximo los rizados de la tensión de salida y de la corriente de entrada, en esta tesis se estudian casos particulares de "interleaving" en estructuras convertidoras continua-continua que utilizan el convertidor elevador ("boost") como célula básica y cuyas tensiones de salida son, idealmente y operando en modo de conducción continua, múltiplos enteros positivos de la tensión de entrada, de ahí la denominación de multiplicadores de tensión que aparece en el título de tesis propuesto. Posteriormente se analizan las posibilidades de regulación de tensión que presentan algunos de los casos de estudio, a costa de incrementar los rizados.

Orthogonal frequency division multiplexing (OFDM) system is the standard of next generation mobile communication, one of the major drawbacks of OFDM systems is the peak-to-average power ratio (PAPR). In this paper, we proposed a low complexity Selected mapping (SLM) scheme to reduce PAPR. In [27], Wang proposed a low complexity SLM scheme by utilizing conversion vectors having the form of a perfect sequence to solve the problem that phase rotation vectors of the conversion vectors do not usually have an equal magnitude in frequency domain. This paper proposed a low complexity SLM scheme based on perfect sequence and consider the symbol interleaving to reduce the correlation between signals in time domain. It is shown that the (Complementary Cumulative Distribution Function, CCDF) of our proposed scheme are closer to the traditional SLM scheme than Wang¡¦s in [27] but with additional complexity. And the computational complexity is much lower than traditional SLM.