The Ultra-Wideband (UWB) communication technology has been extensively attended in recent years. In this thesis, we propose the improved selective-Rake receiver and analyze the performance on UWB channels. The UWB transmission channels are modeled with statistical methods and its fading characteristics are discussed. Different impulse radio properties for the UWB communication system are analyzed. The system performance and design complexity issues of selective-Rake receiver (SRake) are studied. Rake receiver has difficulties achieving desired system performance in the dense multipath environment. The main ideas of SRake receiver are to obtain the SNR level on known multipath channel and to determine the desired number of Rake fingers. Matched filters and maximum likelihood detectors are utilized in the implementation of the SRake to estimate the signal time delay. The CLEAN algorithm is then used in selecting the paths with relatively high energy. Furthermore, we also propose a noise cancellation scheme for performance improvement in the SRake receiver. In the noise cancellation scheme, the multiresolution property of wavelet transform is used for filtering the noise interference caused by the rapid fluctuation factor. In addition, a two-stage search is combined with the original CLEAN algorithm to increase the accuracy of path selection. From our simulation results on the UWB channels, the improved SRake receiver, with noise cancellation and two-stage search, indeed has high SRake output SNR and better path accuracy than the original SRake receiver.

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Ultra-wideband (UWB) is a revolutionary radio communication system that utilizes a large portion of the frequency spectrum while maintaining low power levels and high data rates. UWB systems can be used both indoors and outdoors within the power-level masks regulated by the Federal Communications Commission, thus making the technology very versatile. One of the main advantages of UWB is its robustness to multi-path diversity. The technology has attracted the interests of research and industry alike, owing to the possibility of implementing low-power, low-complexity, and low-cost devices. A widely recognized method of transmitting UWB signals is the use of Impulse Radio technology to transmit information. Impulse Radio Ultra-Wideband (IR-UWB) uses repetitive pulses of very short duration, low duty cycle, and low power levels within FCC regulations. One implementation of IR-UWB pulses in non-coherent transmission is the use of Differential Code-Shifted Reference (DCSR) pulses. In this technique, one of the main challenges at the receiver is pulse-level synchronization that times the received pulses at the right moments for accurate pulse detection. This thesis will introduce two design proposals in attempt to achieve the pulse synchronization. The first proposal is based on a fast-switch-controlled integrator circuit, while the second focuses on the use of an active low pass filter and phase-locked loop circuits to achieve proper clock timing. Both proposals will be presented, together with schematics, computer-aided simulations, and lab tests results.

La technique ultra large bande (UWB) par impulsions consiste à émettre des impulsions de courte durée et de faible énergie offrant ainsi la possibilité de transmettre de l'information à de hauts débits et à faible coût. Dans cette thèse nous nous sommes intéressés aux systèmes ultra large bande à accès multiple par répartition de codes de saut temporel (TH-UWB) dans un contexte asynchrone et dans un environnement de propagation à trajets multiples. Un récepteur rake a été mis en place. Nous avons calculé de manière analytique la variance de l'interférence multi-utilisateur (MUI) en sortie de ce récepteur. Ceci nous a permis d'identifier les paires dites optimales qui minimisent cette variance. Nous avons constaté qu'utiliser ces paires permet d'améliorer significativement le taux d'erreur binaire du système. Une démarche similaire a été appliquée aux systèmes DS-UWB et DS-CDMA, en effet ces systèmes s'expriment analytiquement de manière identique au système TH-UWB. Ainsi nous avons pu caractériser les paires optimales. Nous avons ensuite comparé les performances de ces différents systèmes lorsque la variance de la MUI est minimale. La variance de l'interférence entre symboles et entre trames (ISI / IFI) a été calculée analytiquement. Ceci nous a permis de dimensionner le récepteur rake et le temps de garde intelligemment. Nous avons également observé, en absence d'ISI / IFI et de bruit, un seuil sur la probabilité d'erreur. En modifiant légèrement le récepteur, nous avons éliminé ce seuil. Enfin nous avons établi les bornes de Cramer-Rao relatives à l'estimation des paramètres du canal (amplitudes et retards) en supposant que les trajets pouvaient se chevaucher.

Ubiquitous computing and Internet-of-Things (IoT) implies an untapped opportunity in the realm of information and communication technology, in which a large number of micro-devices with communication and/or computing capabilities, provides connectivity for anything, by anyone at anytime and anywhere. Especially, these devices can be equipped with sensors and actuators that interact with our living environment. Barcode, smart contactless card, Radio Frequency Identification (RFID) systems, wireless sensor network (WSN), and smart mobile phones are some examples which can be utilized in ubiquitous computing. RFIDs and WSN have been recognized as the two promising enablers for realization of ubiquitous computing. They have some great features such as low-cost and small- size implementation, non-line of sight operation, sensing possibilities, data storing ability, and positioning. However, there are several challenges which need to be addressed, such as limited life time for battery powered device, maintenance cost, longer operation range, higher data rate, and operation in dense multipath and multiuser environment. Ultra-Wideband Impulse Radio (UWB-IR) with its huge advantages has been recognized as a great solution for future WSN and RFID. UWB-IR technique has the possibility of achieving Gb/s data rate, hundreds of meter operation range, pJ energy per bit, centimeter accuracy of positioning, and low cost implementation. In this work utilization of UWB-IR in WSN and RFID is investigated. A wireless sensor network based on UWB-IR is proposed focusing on low-cost and low-power implementation. Our contribution is to imply two different architectures in base station and sensor nodes to satisfy power, complexity and cost constraints. For sensor nodes, an autonomous UWB-IR detection is proposed, which detects the UWB signal autonomously and no restrict synchronization is required. It reduces the circuit complexity significantly. The performance in term of bit-error-rate is compared with two other common detection techniques. It is shown that the new detection is more robustness to timing jitter and clock skew, which consequently reduces the clock and synchronization requirements considerably. A novel wireless sensing and identification system, based on remote-powered tag with asymmetric wireless link, is proposed. Our innovative contribution is to deploy two different UWB and UHF communication techniques in uplink and downlink respectively. In the proposed system, tags capture the required power supply from different environmental sources (e.g. electromagnetic wave transmitted by a reader) and transmit data through an ultra-low power impulse UWB link. A new communication protocol is devised based on slotted-aloha anti-collision algorithm. By introducing several improvements including of pipelined communication, adaptive frame size, and skipping idle slots, the system throughput of more than 2000 tags/s is achieved. To prove the system concept a single chip integrated tag is implemented in UMC 0.18μm CMOS process. The measurement results show the minimum sensitivity of -18.5 dB (14.1 μW) and adaptive data rate up to 10 Mb/s. It corresponds to 13.9 meters operation range, considering 4W EIRP, a matched antenna to the tag with 0dB gain, and free space path loss. This is a great improvement in operation range and data rate, compared with conventional passive RFID, which data rate is limited to a few hundreds of Kb/s. System integration in a Liquid-Crystal-polymer (LCP) substrate is investigated. The integration of a tunable UWB-IR transmitter and a power scavenging unit are studied. Our contribution includes embedding and modeling the RF components and antenna in substrate and co-optimizing the chip and package with on-chip versus off-chip passives trade-offs. Simulation results verify the potential of system-on-package solution for UWB integration. The effect of antenna miniaturization in a UWB system is studied. Our focus is to scale down a UWB antenna and optimize the performance through the chip-antenna co-design. A tunable impulse- UWB transmitter is designed in two cases - a conventional 50Ω design and a co-design methodology. The simulation results show that the standard 50Ω design technique can not reach the best condition in all cases, when a real antenna is placed into the system. The performance can be improved significantly when doing codesign. The antennas and UWB transmitter performances are evaluated in a given UWB systems. It is shown that the operation distance at a target performance is reduced with antenna scaling factor and it can be compensated by antenna-transceiver co-design. The result proves the importance of antenna-transceiver codesign, which needs to be addressed in the earliest phases of the design flow. / QC 20100701

In recent years, the requirement of application such as wireless sensor networks and short-range wireless controllers caused the growing of ZigBee technology. ZigBee is a communication technology developed specifically for short-range, low rate, low-cost wireless transmission.There are some characteristic such as short-range, low rate, low cost, and low power. The ZigBee Aliance group developed the specifications of software, and IEEE 802.15.4 group developed the specifications of hardware. IEEE 802.15.4a impulse radio UWB physical layer is one of the ZigBee physical layers. In our study, we designed a baseband signal processing algorithm meeting the specifications of IEEE 802.15.4a. The data processing flow in transmitter followed the specifications. In receiver, we designed baseband algorithms based-on the non-coherent energy detection scheme. Our algorithm including packet detection, synchronization and demodulation, and considering the implementation of algorithm, reducing the complexity of hardware as possible and improving the efficiency. Finally, the system performance is 3.9dB better than the receiver sensitivity.

Ultra-Wideband impulse radio (UWB-IR) technology is an attractive method on multi-user for high data rate transmitting structures. In this thesis, we use the ultra wideband (UWB) signal that is modulated by the time-hopping spread spectrum technique in a wireless multiple access environments, and discuss the influences of multiple access interference. We discuss two parts of the influences of multiple access interference in this thesis. The first, we analyze the multiple access interferences on the conventional correlation receiver, and discuss the influences by using the time hopping code on different multiple access structures. The second, we know that the performances of user detection and system capacity would be degraded by the conventional correlation receiver in the multiple access channels. The Probabilistic Data Association(PDA) multi-user detection technology can eliminate multiple access interferences in this part. We will use this method to verify the system performance through the computer simulations, and compare to other multi-user detectors with convention correlation receivers. Finally, the simulation results show that the performance of the PDA multi-user detections is improved when the system is full loaded.

Ultra-wideband (UWB) is a wireless system which transmits signals across a much wider frequency spectrum than traditional wireless systems. The impulse radio (IR) UWB technique uses ultra-short duration pulses of nanoseconds or less. The objective of this thesis is to provide the design, implementation and testing of the timing recovery between the transmitter and receiver of the recently emerging differential code-shifted reference (DCSR) Impulse radio (IR) ultra-wideband (UWB) system. A new non-coherent energy detection based technique and its algorithm are proposed for timing recovery by means of a phase-locked loop (PLL) circuit. Simulations are presented first to verify the proposed algorithm. Then, it is implemented and tested in the Lattice ECP2 field-programmable gate array (FPGA) evaluation board with VHDL codes (a VHSIC hardware description language). The simulation and implementation results show that the proposed timing recovery scheme can be effectively achieved without much error.

Σε αυτή την εργασία, αφού παρουσιαστεί αναλυτικά η τεχνολογία UWB, μελετούνται από τη βιβλιογραφία τρόποι για την εκτίμηση του ασύρματου καναλιού με χρήση δεδομένων εκπαίδευσης. Στη συνέχεια, υπάρχει μια ανάλυση της προσομοίωσης που έγινε με τη βοήθεια του λογισμικού MATLΑB η οποία υλοποιεί τον πομπό, το κανάλι και το δέκτη με εκτιμητή καναλιού και στο τέλος μελετάται η απόδοση του συστήματος. / This report presents the UWB impulse radio technology and contains a relevant study of channel estimation techniques. In next chapters there is a MATLAB simulation for the full system and the channel estimator subsystem and conclusions are made.

Abstract This Thesis examines low complexity receiver structures for impulse-radio (IR) ultra-wideband (UWB) systems to be used in wireless sensor network applications. Such applications require radio communication solutions characterized by low cost, low complexity hardware and low power consumption to provide very long battery life. Analysis of several auto-correlation receiver (AcR) structures is performed in the presence of additive white Gaussian noise to identify receiver structures that offer a good compromise between implementation complexity and data communication performance. The classes of receiver that demonstrate the best complexity/performance trade-off are shown to be the AcR utilising transmitted-reference with binary pulse amplitude modulation signaling, and the energy detector (ED) utilising binary pulse position modulation. The analysis of these two schemes is extended to consider multipath fading channels. Numerically integrable bit error rate probability (BEP) expressions are derived in order to evaluate the receivers' performance in the presence of fading distributions characterized by closed form characteristic functions. Simulations utilising widely accepted UWB channel models are then used to evaluate the BEP in different indoor environments. Since UWB systems share frequency spectrum with many narrowband (NB) systems, and need to coexist with other UWB systems, the performance of low complexity receivers can be seriously affected by interference. In the presence of NB interference, two cases have been considered: 1) single NB interference, where the interfering node is located at a fixed distance from the receiver, and 2) multiple NB interference, where the interfering nodes are scattered according to a spatial Poisson process. When considering UWB interference, the case of multiple sources of interference has been considered. For both the multiple NB and the multiple UWB interference cases, the model derived considers several interference parameters, which can be integrated into BEP formulations for quick performance evaluations. The framework is sufficiently simple to allow tractable analysis and can serve as a guideline for the design of heterogeneous networks where coexistence between UWB systems and NB systems is of importance. The very large bandwidth of UWB signals offers an unprecedented possibility for accurate ranging operations. Signal leading-edge estimation algorithms based on average maximum likelihood estimators are derived considering different multipath channel fading distributions. Suboptimal solutions are proposed and investigated in order to support ranging capabilities in low complexity receiver structures. The ability to identify line-of-sight and non-line-of-sight conditions with the ED-based receiver is also addressed. An example of an IR-UWB low complexity transceiver based on ED for sensor network applications is proposed in this Thesis. Ad-hoc solutions for pulse transmission, synchronization and data detection are developed.