Made available in DSpace on 2014-06-12T15:50:51Z (GMT). No. of bitstreams: 1 license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2008 / A tecnologia UWB (Ultra-WideBand) é uma das mais promissoras para a comunicação em redes sem fio de curto alcance. Esta afirmação é reforçada pelo fato dos sinais UWB ultrapassarem facilmente obstáculos e pelo fato da tecnologia permitir uma banda passante ultra-larga associada a um baixo consumo de energia. As interferências multi-usuário (MUI) em redes UWB são um dos principais fatores que contribuem para uma degradação rápida da qualidade da comunicação na rede. Assim sendo, a adoção de um mecanismo de mitigação de interferências multi-usuário se faz necessário. Esta dissertação propõe um método de mitigação adaptativa de MUI para redes UWB TH-PPM (Time Hopping - Pulse Position Modulation). O método proposto, chamado de MSS-UWB, se baseia nos sistemas de múltiplos códigos com o objetivo de criar vários enlaces entre um mesmo par transmissor-receptor e realizar adaptação da taxa de dados através da seleção adaptativa destes enlaces. Simulações realizadas com o auxílio do Matlab demonstraram que a utilização de múltiplas seqüências TH para a mitigação adaptativa da MUI traz benefícios com relação à utilização do canal de comunicação.

Kyoto University (京都大学) / 0048 / 新制・論文博士 / 博士(工学) / 乙第12736号 / 論工博第4087号 / 新制||工||1574(附属図書館) / 30549 / (主査)教授 山川 宏, 教授 守倉 正博, 准教授 三谷 友彦 / 学位規則第4条第2項該当

Non-contact life detection is a significant component of both civilian and military rescue applications. As a consequence, this interest has resulted in a very active area of research. The primary goal of this research is reliable detection of a human breathing signal. Additional goals of this research are to carry out detection under realistic conditions, to distinguish between two targets, to determine human breathing rate and estimate the posture. Range gating and Singular Value Decomposition (SVD) have been used to remove clutter in order to detect human breathing under realistic conditions. However, the information of the target range or what principal component contains target information may be unknown. DFT and Short Time Fourier Transform (STFT) algorithms have been used to detect the human breathing and discriminate between two targets. However, the algorithms result in many false alarms because they detect breathing when no target exists. The unsatisfactory performance of the DFT-based estimators in human breathing rate estimation is due to the fact that the second harmonic of the breathing signal has higher magnitude than the first harmonic. Human posture estimation has been performed by measuring the distance of the chest displacements from the ground. This requires multiple UWB receivers and a more complex system. In this thesis, monostatic UWB radar is used. Initially, the SVD method was combined with the skewness test to detect targets, discriminate between two targets, and reduce false alarms. Then, a novel human breathing rate estimation algorithm was proposed using zero-crossing method. Subsequently, a novel method was proposed to distinguish between human postures based on the ratios between different human breathing frequency harmonics magnitudes. It was noted that the ratios depend on the abdomen displacements and higher harmonic ratios were observed when the human target was sitting or standing. The theoretical analysis shows that the distribution of the skewness values of the correlator output of the target and the clutter signals in a single range-bin do not overlap. The experimental results on human breathing detection, breathing rate, and human posture estimation show that the proposed methods improve performance in human breathing detection and rate estimation.

A radar works by radiating electromagnetic energy and detecting the reflected signal returned from the target. The nature of the reflected signal provides information about the target’s distance or speed. In this thesis, we will be using a UWB radar and a CW radar to help detect the presence and rough location of trapped survivors by detecting their motions. Range is estimated in the UWB radar using clutter removal with SVD and for the dual frequency CW Radar using STFT and median filtering. The effect of the algorithm parameters on their performance was analyzed. The performance of the implemented algorithms with regards to small motion detection, distance estimation and penetration capability was analyzed. Both systems are certainly capable of human detection and tracking.

This thesis deals with the use of spatial awareness methods within technologies designed for creation of short-range wireless sensor networks. The thesis analyzes several techniques that can be used to estimate position of objects within the sensor network. For a practical solution, a method based on measuring the time differences of the sent messages was chosen. A circuit implementation of a network node based on the DW1000 chip, which works on ultra-wideband transmission technology, was implemented. A sensor network with the appropriate user application for its operation and display of localization results was also implemented.

This master´s thesis deals with Ultra-wideband and reveals present stage of this technology and situation on marketplace. In this work I will mention the milestones of its history and describe main fundamentals of communication and modulation methods in UWB systems. This work provides an overview of methods in pseudo-noise code design. The practical part includes UWB system simulation based on BPSK modulation and Directsequence multi-access scenario. This work presents BPSK modulated signal behavior in UWB channel model, where AWGN noise and multi-path energy is taken into account. Only physical layer was tested. At the end of this thesis, the summary and conclusion simulation results will be discussed. Bit error rate characteristic is a product of this testing.

UWB is a promising technology for short-range high-rate wireless applicationa.It is able to providemaximal 480Mbps data-rate at a distance of 2 meters in realisticindoormulti-path environments. UWB technology is widely applied to the next generation WPAN as well as the wireless accessof consumer electronics at home. Recently, Multi-Band OFDM based UWB technology proposed by WiMedia has been selected as the international standard by ISO. In China, a new transmission architecture based on Dual-Carrier OFDM technology is adopted as UWB standard draft. Comparing to MB-OFDM based UWB system, DC-OFDM based UWB system has multiple advantages, like more spectrum resource,lower requirements on devices, etc. Besides, it is compatiblewith existing MB-OFDM based UWB technology. Therefore, DC-OFDM based UWB is more flexible. Synchronizationis the first step atthe receiver digital baseband, which is of tremendous importance in any wireless communication systems. The performance of synchronization directly determines whether the receiver can pick up radio signals correctly or not, whether the baseband modules can fulfill the digital signal processing effectively or not. The synchronization process in OFDM system can be briefly divided into two parts: symbol timing and frequency synchronization. Symbol timing serves to judge the starting position of OFDM symbolsafter considering the impact of multi-path fading channel.While the frequency synchronization estimates the multiple imperfections in analog front-end signal processing and make proper compensation. This thesis puts the emphasis on synchronization issues in DC-OFDM based UWB systems. We are the first to analyze the synchronization algorithm as well as the hardware implementation method tailored for DC-OFDM based UWB system. We also present the VLSI implementation result for synchronization module. The thesis consists of symbol timing and frequency synchronization. Regarding on the symbol timing, we analyze the impact of several synchronization errors inOFDM system. After that, we divide the synchronization process into four modulesby functionality: packet detection, coarse timing, TFC detection and fine timing. The internal parameters in each moduleare determined by system simulations. In the aspect of algorithm development, we adopt the joint auto-correlation and cross-correlation method to meet the requirements of UWB system in different indoor multi-path environments, and therefore achieve the robustness. In the aspect of hardware implementation, we put the attention on the structure of some key modules in symbol timing and their VLSI implementation result, such as auto-correlator, cross-correlator, real-number divider, etc. Regarding on the frequency synchronization, we first investigate the multiple analog front-end imperfections in OFDM system, like CFO, SFO and I/Q imbalance, and present their mathematics models respectively in DC-OFDM based UWB system.After that, we analyze the performance degradation in OFDM system due to these non-ideal effects by the metric of EVM. RF designer can build the connection between mismatching parameters and performance degradation by referring to the analysis. Hence, theRF designer is able to traceout the outline of system design. In the aspect of algorithm development, we explore the intrinsic character of I/Q imbalancewhich causes the image interference. Then, we design a set of new training sequences based on phase rotation and give the corresponding estimation algorithm.The simulation result shows that the new training sequence is able to obtain the diversity message introduced by I/Q imbalance and therefore achieve the diversity gain during demodulation process. In order to deal with the challenging situation where multiple analog front-end imperfections co-exist, we propose a joint estimation and compensation scheme. In the aspect of hardware implementation, we present the hardware structure of CFO estimation and compensation module catered for DC-OFDM based UWB system, with the emphasis on CORDIC unit that is responsible for triangle calculations. The VLSI implementation result shows that the proposed CFO estimation and compensation module satisfies the timing and resource requirements in DC-OFDM based UWB system. In the last, we present the prospective research area in 60-GHz applications. It includes multiplenon-ideal impairments, like phase noise, non-linear power amplification, DC offset, ADCs mismatch, etc. It is even more challenging to develop joint estimation and compensation scheme for these non-ideal effects.

A microwave imaging system processes scattered electromagnetic fields in the microwave region to create images. It is an alternative or complementary imaging tool that can be used in breast cancer imaging. It employs non-ionising radiation and during measurement, compression of the scanned body part is avoided. These benefits potentially lead to safer and more comfortable examinations. It also has the potential to be both sensitive and specific to detect small tumors, whilst being much lower cost than current methods, such as magnetic resonant imaging, mammography and ultrasound. This thesis reports a multi-layer active antenna array for breast imaging using microwaves from 3 GHz to 8 GHz. The proposed structure resolves the outstanding problem in the design of large active antenna arrays for tissue imaging, namely, the isolation of the antennas from the electronic circuits. A ground plane within the multi-layer design separates the antenna array from the electronics array while providing shielding to the antennas from the back and improved power coupling into the tissue. The possibility of a high-speed vertical connector to provide interconnection between the antenna array and the mixer array is investigated and measurements show that it could be utilized for the frequency range from 3 GHz to 8 GHz. / Thesis / Master of Applied Science (MASc)

Traditionally, spread-spectrum systems have been employed to provide low probability-of-intercept (LPI) and low probability-of-detection (LPD) performances at the physical layer, but the messages transmitted over such a system are still encrypted with a powerful cipher to protect their secrecy. Our challenge is to find a solution to provide an additional level of security at the physical layer so that simple systems such as RFID tags with limited resources can be secure without using standard encryption. It has recently been suggested that the cryptographic security of the system can be enhanced by exploiting physical properties of UWB signals. With an eavesdropper observing the communications over multipath channels between two legitimate partners sharing a secret key of a limited length, we consider both coherent and reference-based UWB schemes to enhance security. The security of the legitimate nodes is achieved by signal attributes based on the secret key, conferring an advantage over the adversary. We propose UWB signaling schemes to improve physical layer security when the transmission is intended for coherent reception and TR reception. Among possible improvements, we consider removing the frame structure of the UWB coherent signaling scheme, resulting in pulses that can be located anywhere in the symbol period. Our proposed signaling schemes could potentially suggest a solution for applications relying on conventional cryptography, especially for low-data rate RFID systems.

Falls are a cause of concern for the elderly because it can make them unable to call for help. A monitoring system can detect automatically their immobility and provide help to the elderly if they fall. Ultra-wide band signals for a monitoring system is an excellent choice since it has low enough power to not interfere with other medical and household electronics as well as being able to transmit data to a central monitoring unit. One part of this monitoring system is a boundary detection system used to verify that the monitoring system is not capturing events outside the monitoring region such as an event outside the house or in a neighboring room. The work presented in the paper, “A Frequency-Modulated Continuous Wave-Based Boundary Detection System for Determination of Monitoring Region for an Indoor Ultra-Wideband Short Range Radar-Based Eldercare Monitoring System” has determined that a frequency modulated continuous wave (FMCW) based system is an acceptable solution for boundary detection. A FMCW system can measure distance with less than 10cm accuracy if the chosen spectrum bandwidth is 1GHz or more. This thesis presents the design of a low cost approach to small PCB footprint distance detection circuitry for the boundary detection system.