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Ultra-wideband systems exploiting orthonormal waveforms
textElectrical and Computer Engineerin
A VHDL-AMS Simulation Environment for an UWB Impulse Radio Transceiver
Ultra-Wide-Band (UWB) communication based on the impulse radio paradigm is becoming increasingly popular. According to the IEEE 802.15 WPAN Low Rate Alternative PHY Task Group 4a, UWB will play a major role in localization applications, due to the high time resolution of UWB signals which allow accurate indirect measurements of distance between transceivers. Key for the successful implementation of UWB transceivers is the level of integration that will be reached, for which a simulation environment that helps take appropriate design decisions is crucial. Owing to this motivation, in this paper we propose a multiresolution UWB simulation environment based on the VHDL-AMS hardware description language, along with a proper methodology which helps tackle the complexity of designing a mixed-signal UWB System-on-Chip. We applied the methodology and used the simulation environment for the specification and design of an UWB transceiver based on the energy detection principle. As a by-product, simulation results show the effectiveness of UWB in the so-called ranging application, that is the accurate evaluation of the distance between a couple of transceivers using the two-way-ranging metho
Spektralno-efikasna zelena bežična komunikacija pomoću kognitivnog UWB signalnog modela
This paper focuses on spectral lines suppression for non-coherent impulse-radio ultra-wideband (IR-UWB) signals in the presence of pulse attenuation and timing jitter. Particular attention is devoted to severely unbalanced (i.e. non-uniform distributed) data sources where a unified spectral analysis is considered for both uncorrelated and correlated M-ary biorthogonal data-stream scenarios. Indeed, the specific novelty insights of this paper are as follows: i) Proposal of a new spectral-efficient signal model as a modified version of transmitted-reference (TR) approach, where each transmitted symbol is represented by a preamble Data-based Statistical Reference (DSR) followed by a set of transmitted data pulses and within this context, the preamble signal is designed to eliminate spectral lines via an adaptive monitoring of data-stream statistics as the optimal spectral policy; ii) Performance analysis in order to derive optimal signal parameters; iii) Evaluation of the system capabilities over different predefined operational modes.Ovaj rad se fokusira na prigušenje spektralnih linija kod ne-koherentnih radio-impulsnih ultra-širokopojasnih (IR-UWB) signala prilikom slabljenja pulsa i vremenskog podrhtavanja. Posebna pažnja je pridana značajno neuravnoteženim (npr. ne-unifornmno distribuiranim) izvorima podataka gdje je jedinstvena spektralna analiza razmatrana za nekorelirane i korelirane M-arne biortogonalne scenarije prijenosa podataka. Novine predstavljene u ovom radu su: i) Novi spektralno-efikasni signalni model koji je modificirana verzija pristupa prijenosom-reference (TR), gdje se svaki preneseni simbol prikazuje pomoću preambule definirane statistikom reference podataka (DSR) koju slijedi skup prenesenih podatkovnih pulseva, te je u tom kontekstu preambula signala dizajnirana kako bi se eliminirale spektralne linije pomoću optimalnog spektralnog kriterija definiranog adaptivnim praćenjem statistike poslanih podataka; ii) Analiza performansi kako bi se dobili optimalni parametri signala i iii) Evaluacija sposobnosti sustava prilikom rada u različitim predefiniranim stanjima
Multi Detector Fusion of Dynamic TOA Estimation using Kalman Filter
In this paper, we propose fusion of dynamic TOA (time of arrival) from
multiple non-coherent detectors like energy detectors operating at sub-Nyquist
rate through Kalman filtering. We also show that by using multiple of these
energy detectors, we can achieve the performance of a digital matched filter
implementation in the AWGN (additive white Gaussian noise) setting. We derive
analytical expression for number of energy detectors needed to achieve the
matched filter performance. We demonstrate in simulation the validity of our
analytical approach. Results indicate that number of energy detectors needed
will be high at low SNRs and converge to a constant number as the SNR
increases. We also study the performance of the strategy proposed using IEEE
802.15.4a CM1 channel model and show in simulation that two sub-Nyquist
detectors are sufficient to match the performance of digital matched filter
Analysis Of Time Synchronization Errors In High Data Rate Ultrawideban
Emerging Ultra Wideband (UWB) Orthogonal Frequency Division Multiplexing (OFDM) systems hold the promise of delivering wireless data at high speeds, exceeding hundreds of megabits per second over typical distances of 10 meters or less. The purpose of this Thesis is to estimate the timing accuracies required with such systems in order to achieve Bit Error Rates (BER) of the order of magnitude of 10-12 and thereby avoid overloading the correction of irreducible errors due to misaligned timing errors to a small absolute number of bits in error in real-time relative to a data rate of hundreds of megabits per second. Our research approach involves managing bit error rates through identifying maximum timing synchronization errors. Thus, it became our research goal to determine the timing accuracies required to avoid operation of communication systems within the asymptotic region of BER flaring at low BERs in the resultant BER curves. We propose pushing physical layer bit error rates to below 10-12 before using forward error correction (FEC) codes. This way, the maximum reserve is maintained for the FEC hardware to correct for burst as well as recurring bit errors due to corrupt bits caused by other than timing synchronization errors
On the Effects of Estimation Error and Jitter in Ultra-Wideband Communication
The opening of the 3.6 - 10.1 GHz frequency spectrum below the \u27noise-floor\u27 by the FCC in 2002 has made possible the prospect of reusing this frequency spectrum through ultra-wideband (UWB) communication. In this thesis, we compare the performance of several UWB systems in the presence of estimation error and jitter. We then develop two alternative decision schemes to combat the effect of jitter in the UWB system. Numerical results show that one of the schemes provides significantly better performance in the presence of severe jitter than maximal ratio combining and minimal degradation of performance if jitter is not present. A generalized maximal ratio combining decision scheme to combat the presence of estimation error is also proposed. It is shown that the generalized scheme outperforms traditional maximal ratio combining
M-sequenze based ultra-wideband radar and its application to crack detection in salt mines
Die vorliegende Dissertation beschreibt einen innovativen ultra-breitband
(UWB)elektromagnetischen Sensor basierend auf einem
Pseudo-Rauschverfahren.Der Sensor wurde für zerstörungsfreies Testen in
zivilen Anwendungen entwickelt.Zerstörungsfreies Testen entwickelt sich zu
einem immer wichtiger werdenden Bereich in Forschung und Entwicklung. Neben
unzähligen weiteren Anwendungen und Technologien, besteht ein primäres
Aufgabenfeld in der Überwachung und Untersuchung von Bauwerken und
Baumaterialien durch berührungslose Messung aus der Ferne.Diese Arbeit
konzentriert sich auf das Beispiel der Auflockerungszone im Salzgestein.Der
Hintergrund und die Notwendigkeit, den Zustand der oberflächennahen
Salzschichten in Salzminen kennen zu müssen, werden beleuchtet und die
Messaufgabe anhand einfacher theoretischer Überlegungen beschrieben. Daraus
werden die Anforderungen für geeignete UWB Sensoren abgeleitet. Die
wichtigsten Eigenschaften sind eine sehr hohe Messband breite sowie eine sehr
saubere Systemimpulsantwort frei von systematischen Gerätefehlern. Beide
Eigenschaften sind notwendig, um die schwachen Rückstreuungen
der Auflockerungen trotz der unvermeidlichen starken Oberflächenreflexion
detektieren zu können.Da systematische Fehler bei UWB Geräten technisch
nicht von vorne herein komplett vermeidbar sind, muss der Sensor eine
Gerätekalibrierung erlauben, um solche Fehler möglichst gut zu
unterdrücken.Aufgrund der genannten Anforderungen und den Nebenbedingungen
der Messumgebung unter Tage, wurde aus den verschiedenen UWB-Technologien
ein Prinzip ausgewählt, welches pseudozufällige Maximalfolgen als
Anregungssignal benutzt. Das M-Sequenzkonzept dient als Ausgangpunkt für
zahlreiche Weiterentwicklungen. Ein neues Sendemodul erweitert dabei die
Messbandbreite auf 12~GHz. Die äquivalente Abtastrate wird um den Faktor
vier auf 36~GHz erhöht, ohne den geringen Abtastjitter des ursprünglichen
Konzepts zu vergrössern.Weiterhin wird die Umsetzung eines
Zweitormesskopfes zur Erfassung von S-Parametern sowie einer automatische
Kalibriereinheit beschrieben. Etablierte Kalibrierverfahren aus dem Bereich
der Netzwerkanalyse werden kurz rekapituliert und die Adaption des 8-Term
Verfahrens mit unbekanntem Transmissionsnormal für das
M-Sequenzsystem beschrieben. Dabei werden Kennwerte vorgeschlagen, die dem
Bediener unter Tage einfach erlauben, die Kalibrierqualität einzuschätzen
und Hinweise auf mögliche Gerätefehler oder andere Probleme zu bekommen.
Die Kalibriergenauigkeit des neuen Sensors im Labor wird mit der eines
Netzwerkanalysators verglichen. Beide Geräte erreichen eine störungsfreie
Dynamik von mehr als 60~dB in den Systemimpulsantworten für Reflexion und
Transmission.Der neu entwickelte UWB Sensor wurde in zahlreichen Messungen
in Salzminen in Deutschland getestet. Zwei Messbeispiele werden vorgestellt
- ein sehr alter, kreisrunder Tunnel sowie ein ovaler Tunnelstumpf,
welcher kurz vor den Messungen erst aufgefahren wurde. Messaufbauten und
Datenverarbeitung werden beschrieben. Schließlich werden Schlussfolgerungen
und Vorschläge für zukünftige Arbeiten mit dem neuen M-Sequenzsensor sowie
der Messung von Auflockerungen im Salzgestein diskutiert.This dissertation describes an innovative ultra-wideband
(UWB) electromagnetic sensor device based on a pseudo-noise principle
developed in the context of non-destructive testing in civil
engineering.Non-destructive testing is becoming a more and more important
fieldfor researchers and engineers alike. Besides the vast field of
possibleapplications and testing technologies, a prime and therefore
typical topic is the inspection and monitoringof constructions and
materials by means of contactless remote sensing techniques.This work
focuses on one example the assessment of the disaggregation zone in salt
rock tunnels.The background and relevance of knowing the state of salt rock
layers near a tunnel's surface are explainedand simple theoretical
considerations for requirements of suitable UWB sensor devices are shown.
The most important sensor parameters are a very large measurement bandwidth
and a very clean impulse response. The latterparameter translates into the
mandatory application of calibration techniques to remove systematic errors
of the sensor system itself. This enables detection of weak scattering
responses from near-surface disaggregation despite the presence of a strong
surface reflection.According to the mentioned requirements and other side
conditions in salt mine environments an UWB sensor principlebased on
pseudo-noise stimuli namely M-Sequences is selected as a starting point for
system development. A newtransmitter frontend for extending the stimulus
bandwidth up to 12~GHz is presented. Furthermore, a technique for
increasing the (equivalent) sampling rate while keeping the stable and
low-jitter sampling regime of the M-Sequencesapproach is introduced and its
implementation is shown. Moreover, an automatic calibration unit for full
two-port coaxial calibration of the new UWB sensor has been developed.
Common calibration techniques from the area of vector network analysers are
shortly reviewed and a reasonablealgorithm the 8-term method with an
unknown line standard - is selected for the M-Sequences device. The 8-term
method is defined in the frequency domain and is adapted for use with time
domain devices. Some performance figures and comparisonwith calibration
results from network analysers are discussed to show the effectiveness of
the calibration.A spurious-free dynamic range of the time domain impulse
responses in excess of 60~dB has been achieved for reflection as well as
transmission measurements.The new UWB sensor was used in various real world
measurements in different salt mines throughout Germany. Two
measurementexamples are described and results from the disaggregation zone
of a very old and a freshly cut tunnel will be presented. Measurement setup
and data processing are discussed and finally some conclusions for future
work on this topic are drawn
Transceiver design and system optimization for ultra-wideband communications
This dissertation investigates the potential promises and proposes possible solutions to the challenges of designing transceivers and optimizing system parameters in ultra-wideband (UWB) systems. The goal is to provide guidelines for UWB transceiver implementations under constraints by regulation, existing interference, and channel estimation.
New UWB pulse shapes are invented that satisfy the Federal Communications Commission spectral mask. Parameters are designed to possibly implement the proposed pulses. A link budget is quantified based on an accurate frequency-dependent path loss calculation to account for variations across the ultra-wide bandwidth of the signal.
Achievable information rates are quantified as a function of transmission distance over additive white Gaussian noise and multipath channels under specific UWB constraints: limited power spectral density, specific modulation formats, and a highly dispersive channel. The effect of self-interference (SI) and inter-symbol interference (ISI) on channel capacity is determined, and modulation formats that mitigate against this effect is identified. Spreading gains of familiar UWB signaling formats are evaluated, and UWB signals are proved to be spread spectrum. Conditions are formulated for trading coding gain with spreading gain with only a small impact on performance. Numerical results are examined to demonstrate that over a frequency-selective channel, the spreading gain may be beneficial in reducing the SI and ISI resulting in higher information rates.
A reduced-rank adaptive filtering technique is applied to the problem of interference suppression and optimum combining in UWB communications. The reduced-rank combining method, in particular the eigencanceler, is proposed and compared with a minimum mean square error Rake receiver. Simulation results are evaluated to show that the performance of the proposed method is superior to the minimum mean square error when the correlation matrix is estimated from limited data.
Impact of channel estimation on UWB system performance is investigated when path delays and path amplitudes are jointly estimated. Cramér-Rao bound (CRB) expressions for the variance of path delay and amplitude estimates are formulated using maximum likelihood estimation. Using the errors obtained from the CRB, the effective signal-to-noise ratio for UWB Rake receivers employing maximum ratio combining (MRC) is devised in the presence of channel path delay and amplitude errors. An exact expression of the bit error rate (BER) for UWB Rake receivers with MRC is derived with imperfect estimates of channel path delays and amplitudes.
Further, this analysis is applied to design optimal transceiver parameters. The BER is used as part of a binary symmetric channel and the achievable information rates are evaluated. The optimum power allocation and number of symbols allocated to the pilot are developed with respect to maximizing the information rate. The optimal signal bandwidth to be used for UWB communications is determined in the presence of imperfect channel state information. The number of multipath components to be collected by Rake receivers is designed to optimize performance with non-ideal channel estimation
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