An Assessment of Indoor Geolocation Systems

Currently there is a need to design, develop, and deploy autonomous and portable indoor geolocation systems to fulfil the needs of military, civilian, governmental and commercial customers where GPS and GLONASS signals are not available due to the limitations of both GPS and GLONASS signal structure designs. The goal of this dissertation is (1) to introduce geolocation systems; (2) to classify the state of the art geolocation systems; (3) to identify the issues with the state of the art indoor geolocation systems; and (4) to propose and assess four WPI indoor geolocation systems. It is assessed that the current GPS and GLONASS signal structures are inadequate to overcome two main design concerns; namely, (1) the near-far effect and (2) the multipath effect. We propose four WPI indoor geolocation systems as an alternative solution to near-far and multipath effects. The WPI indoor geolocation systems are (1) a DSSS/CDMA indoor geolocation system, (2) a DSSS/CDMA/FDMA indoor geolocation system, (3) a DSSS/OFDM/CDMA/FDMA indoor geolocation system, and (4) an OFDM/FDMA indoor geolocation system. Each system is researched, discussed, and analyzed based on its principle of operation, its transmitter, the indoor channel, and its receiver design and issues associated with obtaining an observable to achieve indoor navigation. Our assessment of these systems concludes the following. First, a DSSS/CDMA indoor geolocation system is inadequate to neither overcome the near-far effect not mitigate cross-channel interference due to the multipath. Second, a DSSS/CDMA/FDMA indoor geolocation system is a potential candidate for indoor positioning, with data rate up to 3.2 KBPS, pseudorange error, less than to 2 m and phase error less than 5 mm. Third, a DSSS/OFDM/CDMA/FDMA indoor geolocation system is a potential candidate to achieve similar or better navigation accuracy than a DSSS/CDMA indoor geolocation system and data rate up to 5 MBPS. Fourth, an OFDM/FDMA indoor geolocation system is another potential candidate with a totally different signal structure than the pervious three WPI indoor geolocation systems, but with similar pseudorange error performance

Ultra low range sidelobe level pulse compression waveform design for spaceborne meteorological radars.

Meteorological measurements from spaceborne radars present several advantages over current passive techniques, due to the radar capability to discriminate backscattered energy in range. However, the system configuration imposes stringent design requirements in order to guarantee cloud and rain detectability, in particular on the radar waveform. Since power is severely restricted on board a satellite, it is necessary to achieve an efficient range resolution with low transmitted power requirements. Pulse compression theory solves the previous conflicting demand, but the transmitted signal needs to be carefully designed in order to allow the significantly large dynamic range (between 60 and 80 dB depending on the type of meteorological target) needed to carry out the measurements. Several pulse compression range sidelobe reduction techniques of differing natures have been investigated and reported in the literature during the past 50 years. A detailed survey of the most relevant range sidelobe supression procedures has been carried out in order to identify the most suitable frequency modulation candidates which are potentially capable of meeting the stringent specifications of spaceborne radar meteorology. Novel pulse compression waveform design techniques have also been developed, employing linear FM predistortion functions and asymmetric frequency modulation laws, which provide excellent performance in terms of range sidelobe level (below -60 dB) and Doppler tolerance. Different options for the provision of a rain mode for the RA-2 Radar Altimeter (due to fly on European Space Agency ENVISAT satellite) are described, based on altimetry linear FM full-deramp technique concepts. Finally, amplitude modulated pulse compression waveform design alternatives are analysed for the MACSIM radar (Millimetre wave Active Cloud Structure Imaging Mission, European Space Agency Pre Phase A Study), which allow to measure different type of clouds within the Mission required radiometric resolution accuracy

Flow Assessment Using Optical Coherence Microscopy Based Particle Image Velocimetry

Congenital heart diseases (CHDs) are the most common forms of congenital malformation in newborns. Among all types of CHDs, a large portion is contributed by malformation of endocardial cushion malformation during early heart development. Although the etiology of endocardial cushion malformation is unclear, it is a result of interactions between genetic and environmental factors has been confirmed. There is hypothesis indicating that malformation of endocardial cushion is caused by altered shear stress conditions where in cushion forming area the shear stress is supposed to be high compare with other area in congenital heart. However it is difficult to justify due to lack of in vivo imaging modality that is able to monitor structure and hemodynamic conditions simultaneously and over long time period. To address this problem, we present an optical coherence microscopy based particle image velocimetry system. This system is capable of invasively imaging biological sample structures at micrometer resolution and providing velocity information at the same time. With this imaging set up we successfully assessed velocity profile in a microfluidic system with simultaneous structure details demonstration of the microfluidic channel. Both flow measurement and structural information were verified using conventional microscopy. As a result, OCM-based PIV imaging modality not only makes it feasible to study in detail the process of congenital heart remodeling in response to environmental alterations, but also provides new options for measuring fluid flow in live tissue

Adaptive time-frequency analysis for cognitive source separation

This thesis introduces a framework for separating two speech sources in non-ideal, reverberant environments. The source separation architecture tries to mimic the extraordinary abilities of the human auditory system when performing source separation. A movable human dummy head residing in a normal office room is used to model the conditions humans experience when listening to complex auditory scenes. This thesis first investigates how the orthogonality of speech sources in the time-frequency domain drops with different reverberation times of the environment and shows that separation schemes based on ideal binary time-frequency-masks are suitable to perform source separation also under humanoid reverberant conditions. Prior to separating the sources, the movable human dummy head analyzes the auditory scene and estimates the positions of the sources and the fundamental frequency tracks. The source localization is implemented using an iterative approach based on the interaural time differences between the two ears and achieves a localization blur of less than three degrees in the azimuth plane. The source separation architecture implemented in this thesis extracts the orthogonal timefrequency points of the speech mixtures. It combines the positive features of the STFT with the positive features of the cochleagram representation. The overall goal of the source separation is to find the ideal STFT-mask. The core source separation process however is based on the analysis of the corresponding region in an additionally computed cochleagram, which shows more reliable Interaural Time Difference (ITD) estimations that are used for separation. Several algorithms based on the ITD and the fundamental frequency of the target source are evaluated for their source separation capabilities. To enhance the separation capabilities of the single algorithms, the results of the different algorithms are combined to compute a final estimate. In this way SIR gains of approximately 30 dB for two source scenarios are achieved. For three source scenarios SIR gains of up to 16 dB are attained. Compared to the standard binaural signal processing approaches like DUET and Fixed Beamforming the presented approach achieves up to 29 dB SIR gain.Diese Dissertation beschreibt ein Framework zur Separation zweier Quellen in nicht-idealen, echobehafteten Umgebungen. Die Architektur zur Quellenseparation orientiert sich dabei an den außergewöhnlichen Separationsfähigkeiten des menschlichen Gehörs. Um die Bedingungen eines Menschen in einer komplexen auditiven Szene zu imitieren, wird ein beweglicher, menschlicher Kunstkopf genutzt, der sich in einem üblichen Büroraum befindet. In einem ersten Schritt analysiert diese Dissertation, inwiefern die Orthogonalität von Sprachsignalen im Zeit-Frequenz-Bereich mit unterschiedlichen Nachhallzeiten abnimmt. Trotz der Orthogonalitätsabnahme sind Separationsansätze basierend auf idealen binären Masken geeignet um eine Trennung von Sprachsignalen auch unter menschlichen, echobehafteten Bedingungen zu realisieren. Bevor die Quellen getrennt werden, analysiert der bewegliche Kunstkopf die auditive Szene und schätzt die Positionen der einzelnen Quellen und den Verlauf der Grundfrequenz der Sprecher ab. Die Quellenlokalisation wird durch einen iterativen Ansatz basierend auf den Zeitunterschieden zwischen beiden Ohren verwirklicht und erreicht eine Lokalisierungsgenauigkeit von weniger als drei Grad in der Azimuth-Ebene. Die Quellenseparationsarchitektur die in dieser Arbeit implementiert wird, extrahiert die orthogonalen Zeit-Frequenz-Punkte der Sprachmixturen. Dazu werden die positiven Eigenschaften der STFT mit den positiven Eigenschaften des Cochleagrams kombiniert. Ziel ist es, die ideale STFT-Maske zu finden. Die eigentliche Quellentrennung basiert jedoch auf der Analyse der entsprechenden Region eines zusätzlich berechneten Cochleagrams. Auf diese Weise wird eine weitaus verlässlichere Auswertung der Zeitunterschiede zwischen den beiden Ohren verwirklicht. Mehrere Algorithmen basierend auf den interauralen Zeitunterschieden und der Grundfrequenz der Zielquelle werden bezüglich ihrer Separationsfähigkeiten evaluiert. Um die Trennungsmöglichkeiten der einzelnen Algorithmen zu erhöhen, werden die einzelnen Ergebnisse miteinander verknüpft um eine finale Abschätzung zu gewinnen. Auf diese Weise können SIR Gewinne von ungefähr 30 dB für Szenarien mit zwei Quellen erzielt werden. Für Szenarien mit drei Quellen werden Gewinne von bis zu 16 dB erzielt. Verglichen mit binauralen Standardverfahren zur Quellentrennung wie DUET oder Fixed Beamforming, gewinnt der vorgestellte Ansatz bis zu 29 dB SIR

Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

Dynamics of large-scale brain activity in health and disease

Tese de doutoramento em Engenharia Biomédica e Biofísica, apresentada à Universidade de Lisboa através da Faculdade de Ciências, 2008Cognition relies on the integration of information processed in widely distributed brain regions. Neuronal oscillations are thought to play an important role in the supporting local and global coordination of neuronal activity. This study aimed at investigating the dynamics of the ongoing healthy brain activity and early changes observed in patients with Alzheimer's disease (AD). Electro- and magnetoencephalography (EEG/MEG) were used due to high temporal resolution of these techniques. In order to evaluate the functional connectivity in AD, a novel algorithm based on the concept of generalized synchronization was improved by defining the embedding parameters as a function of the frequency content of interest. The time-frequency synchronization likelihood (TF SL) revealed a loss of fronto-temporal/parietal interactions in the lower alpha (8 10 Hz) oscillations measured by MEG that was not found with classical coherence. Further, long-range temporal (auto-) correlations (LRTC) in ongoing oscillations were assessed with detrended fluctuation analysis (DFA) on times scales from 1 25 seconds. Significant auto-correlations indicate a dependence of the underlying dynamical processes at certain time scales of separation, which may be viewed as a form of "physiological memory". We tested whether the DFA index could be related to the decline in cognitive memory in AD. Indeed, a significant decrease in the DFA exponents was observed in the alpha band (6 13 Hz) over temporo-parietal regions in the patients compared with the age-matched healthy control subjects. Finally, the mean level of SL of EEG signals was found to be significantly decreased in the AD patients in the beta (13 30 Hz) and in the upper alpha (10 13 Hz) and the DFA exponents computed as a measure of the temporal structure of SL time series were larger for the patients than for subjects with subjective memory complaint. The results obtained indicate that the study of spatio-temporal dynamics of resting-state EEG/MEG brain activity provides valuable information about the AD pathophysiology, which potentially could be developed into clinically useful indices for assessing progression of AD or response to medication

Proceedings of the Fall 1995 Advanced Digital Communication Systems

Coordinated Science Laboratory was formerly known as Control Systems Laborator