D.Ing. (Electrical and Electronic Engineering) / Please refer to full text to view abstract

This thesis presents novel techniques for the reduction of audio recordings and signal processing techniques as part of cough recognition. Evidence collected shows the reduction technique to be effective and the recognition techniques to give consistent performance across different patients. Cough is one of the commonest symptoms reported by patients to GPs. Despite this, it remains a significantly unmet medical need. At present, there exists no practical and validated technique for assessing the efficacy of therapies to treat cough on a large enough scale. Research that is presently undertaken requires fitting a patient with a recording system which will record their coughing and all other sound for a predefined period, usually 24 hours or less. This audio is then counted manually by trained cough counters to produce counts for each record which can be used as data for cough studies. Research in this field is relatively new, but a number of attempts have been made to automate this process. None so far have shown sufficient reliability or precision to be of sufficient use. The aim of this research is to analyse from the ground up signal processing techniques which can aid cough research. Specifically, the research will look into data minimisation techniques to improve the efficiency of manual counting techniques and recognition algorithmsThe research has produced a published record reduction system which can reduce 24 hour cough records down to around 10% of their original size without compromising the statistics of subsequent manual counts. Additionally, a review of signal processing techniques for cough recognition has produced a robust event detection technique and measurement techniques which have shown remarkable consistency between patients and conditions. Throughout the research a clear understanding of the limitations and possible solutions are pursued and reported on to aid further progress on what is a young and developing research field.

This thesis investigates the possibility of detecting weak vital signs, such as heartbeat and respiration rate, through the implementation of quadrature demodulation and frequency spectrum algorithms on a high performance digital signal processor. This thesis has been part of an ongoing research project at Linkoping University, with the aim to develop a sensor platform for wireless measurements of these vital signs. This sensor platform has been expected to consist of two major physical devices, a RF-radar front-end including a quadrature multi-port and a processing back-end which holds the implementation of the algorithms to detect the vital signs. The back-end consists of a data acquisition- and a processing-part which together forms the digital signal processor. The results show that the implemented algorithms works in terms of being able to find artificial vital signs from quadrature signals. This result also confirms that the hardware solution proposed during this thesis, has been considered as viable for the aim of the project.

This master thesis was completed at Limes Audio in Umeå. Limes Audio are specialized in speech enhancement software which is mostly used in conference phones. Their software is used to reduce noise, echo cancellation as well as reduction of distortion. When a conference phone is malfunctioning it can be troublesome to find the cause of the problem. Common issues that lead to perceived poor audio quality are rattling plastics, loose parts and an environment with demanding acoustics. There is a need for automatic tests to run on conference phone which can diagnose audio quality and the acoustics of the environment where the conference phone is located in. A previous master thesis by Wilhelmsson called "Estimating Loudspeaker Distortion and Room Reverberation Time Using a Speakerphone" focused on evaluating several tests run in MATLAB for analyzing acoustic characteristics of a room. The goal of this thesis was to continue the work of the master thesis by Wilhelmsson. Previous tests served as a basis for this thesis. The tests where modified and rewritten in C and run on a Linux computer connected to a specific conference phone model. In the extended test made in this thesis using sine sweep signals, the reverberation time as well as the distortion for the conference phone setup was determined. The calculated reverberation time was compared to the results using Room EQ Wizard and gave almost identical results. Total harmonic distortion was not easy to relate to the perceived audio quality. There is a need to further develop methods to take into account other types of distortion than the total harmonic distortion. Rub & buzz is one kind of distortion that could be of interest. To investigate pass or fail thresholds for reverberation time as well as distortion is central for further development of this test software.

[ES] Los sistemas de transmisión óptica no-coherente se emplean actualmente en las redes ópticas de corto alcance (< 80 km), como son las redes de ámbito metropolitano. La implementación más común en el estado del arte se basa en sistemas que emplean multiplexación por división en longitud de onda (WDM, wavelength division multiplexing) de cuatro longitudes de onda (¿) proporcionando un régimen binario de 100 Gbps (4¿×25 Gbps). En los últimos años, los sistemas de transmisión ópticos no-coherentes están evolucionando desde 100 Gbps a 400 Gbps (4¿×100 Gbps). Dado que este mercado comprende un gran número de sistemas, el coste es un parámetro importante que debe ser lo más bajo posible. El objetivo de esta tesis es investigar distintos aspectos del procesado de señal en general y, específicamente, investigar nuevas técnicas de procesado digital de señal (DSP, digital signal processing) que puedan ser utilizadas en sistemas de transmisión óptica no-coherentes empleando la modulación por amplitud de pulsos (PAM, pulse-amplitude modulation). Para que una técnica DSP sea interesante en el contexto de una red óptica WDM no-coherente, esta debe mitigar de manera efectiva al menos una de las tres limitaciones principales que afectan a estos sistemas: limitaciones de ancho de banda, limitaciones por dispersión cromática (CD), y el ruido. En esta tesis se proponen y examinan una serie de algoritmos cuyo su rendimiento es analizado mediante simulación y experimentalmente en laboratorio: - Feed-forward equalizer (FFE): este es el esquema de ecualización más común que se emplea principalmente en las transmisiones ópticas no-coherentes de alto régimen binario. Puede compensar grandes limitaciones en el ancho de banda. - Estimación de la secuencia de máxima verosimilitud (MLSE): el MLSE es un detector óptimo y, por lo tanto, proporciona las mejores prestaciones en detección cuando se abordan las limitaciones por CD y de ancho de banda. - Conformación geométrica de la constelación: en los esquemas de modulación de intensidad óptica multinivel, la distancia entre los niveles de amplitud puede ajustarse adecuadamente (de manera que no son equidistantes) a fin de aumentar la tolerancia de la señal frente al ruido. - Conformación probabilística: técnica diseñada específicamente para esquemas de modulación multinivel. Esta técnica ajusta la probabilidad de cada nivel de amplitud de modo que se incrementa la tolerancia al ruido óptico. - Señalización de respuesta parcial (PRS, partial signaling response): este es un enfoque basado en DSP donde una interferencia entre símbolos (ISI, inter-symbol interference) controlada es introducida intencionalmente de tal manera que la señal resultante requiere menos ancho de banda. La técnica PRS puede adaptarse para combatir también el efecto de CD. - Pre-énfasis digital (DPE, digital pre-emphasis): esta técnica consiste en aplicar el inverso de la función de transferencia del sistema a la señal en el transmisor, lo que reduce el impacto de las limitaciones de ancho de banda en el receptor. - Modulación con codificación Trellis (TCM, Trellis-coded modulation): esquema de modulación que combina elementos de corrección de errores (FEC, forward error correction) con técnicas de partición en conjuntos y modulación multidimensional para generar una señal más resistente al ruido. - Modulación multidimensional por partición en conjuntos: muy similar a TCM, pero sin ningún elemento FEC. Tiene menos ganancias que TCM en términos de tolerancia al ruido, pero no es tan sensible al ISI. Utilizando estas técnicas, esta tesis demuestra que es posible lograr una transmisión óptica con régimen binario de 100 Gbps/¿ empleando componentes de bajo coste. En esta tesis también demuestra regímenes binarios de más de 200 Gbps, lo que indica que la transmisión óptica no-coherente con modulación PAM puede ser una solución viable y eficiente en coste / [CAT] Actualment, s'utilitzen sistemes òptics no coherents en xarxes òptiques de curt abast ( < 80 km), com són les xarxes d'àmbit metropolità. La implementació més comuna que podem trobar en l'estat de l'art es correspon amb sistemes emplenant multiplexació per divisió en longitud d'ona (WDM, wavelength division multiplexing) de quatre longituds d'ona (¿) proporcionant un règim binari de 100 Gbps (4¿×25 Gbps). En els últims anys, els sistemes de transmissió òptica no-coherents han evolucionat des de 100 Gbps cap a 400 Gbps (100 Gbps/¿). Atès que el mercat de sistemes de curt abast compren un gran volum de dispositius òptics instal·lats, el cost unitari és molt important i ha de ser el més baix possible. L'objectiu d'aquesta tesi és analitzar aspectes del processament de senyal en general i, específicament, investigar noves tècniques de processament digital de senyal (DSP, digital signal processing) que puguen ser utilitzades en sistemes de transmissió òptica no-coherent que utilitzen la modulació per amplitud d'impulsos (PAM, pulse-amplitude modulation). Per tal que una tècnica DSP es considere interessant per a una xarxa òptica WDM no-coherent, aquesta ha de mitigar efectivament almenys una de les tres principals limitacions que afecten aquests sistemes: limitacions d'ample de banda, limitacions per dispersió cromàtica (CD), i el soroll. En aquesta tesi s'examinen una sèrie d'algoritmes, el seu rendiment s'analitza per simulació i experimentalment en laboratori: - Feed-forward equalizer (FFE): aquest és l'esquema d'equalització més comú i s'utilitza bàsicament en les transmissions òptiques no coherents d'alt règim binari. Pot compensar grans quantitats de limitacions d'ample de banda. - Estimació de la seqüència de probabilitat màxima (MLSE): el MLSE és un detector òptim i, per tant, proporciona el millor rendiment quan es tracta de limitacions d'ample de banda i de CD. - Conformació geomètrica de la constel·lació: en esquemes de modulació òptica d'intensitat multinivell es pot ajustar la distància entre els nivells d'amplitud (de manera que ja no són equidistants) per augmentar la tolerància del senyal al soroll. - Conformació probabilística: una tècnica dissenyada específicament per als esquemes de modulació multinivell; ajusta la probabilitat de cada nivell d'amplitud de manera que augmenta la tolerància al soroll òptic. - Senyalització de resposta parcial (PRS, partial signaling response): és un enfocament basat en DSP on la interferència entre símbols (ISI, inter-symbol interference) controlada s'introdueix intencionalment de manera que el senyal resultant requereix menys ample de banda. La tècnica PRS es pot adaptar per combatre els efectes del CD. - Pre-èmfasi digital (DPE, digital pre-emphasis): aquesta tècnica consisteix a aplicar la inversió de la funció de transferència del sistema a la senyal en el transmissor de manera que es redueix l'impacte de les limitacions d'ample de banda en la senyal en el receptor. - Modulació amb codificació Trellis (TCM, Trellis-coded modulation): esquema de modulació que combina els elements de correcció d'errors avançats (FEC, forward error correction) amb tècniques de partionament de conjunts i modulació multidimensional per generar un senyal més resistent al soroll. - Modulació multidimensional per partició en conjuntes: molt similar a TCM però sense elements FEC. Té guanys menors que TCM en termes de tolerància al soroll, però no és tan sensible a l'ISI. Mitjançant l'ús d'aquestes tècniques, aquesta tesi demostra que és possible aconseguir una transmissió òptica amb un règim binari de 100 Gbps/¿ utilitzant components de baix cost. Esta tesi també demostra règims binaris de més de 200 Gbps, el que indica que la tecnologia no-coherent amb modulació PAM és una solució viable i eficient en cost per a una nova generació de sistemes transceptors òptics WDM funcionant a 800 Gbps (4¿×200 G / [EN] Non-coherent optical transmission systems are currently employed in short-reach optical networks (reach shorter than 80 km), like metro networks. The most common implementation in the state-of-the-art is the four wavelength (¿) 100 Gbps (4¿×25 Gbps) wavelength division multiplexing (WDM) transceiver. In recent years non-coherent optical transmissions are evolving from 100 Gbps to 400 Gbps (4¿×100 Gbps). Since in the short-reach market the volume of optical devices being deployed is very large, the cost-per-unit of the devices is very important, and it should be as low as possible. The goal of this thesis is to investigate some general signal processing aspects and, specifically, digital signal processing (DSP) techniques required in non-coherent pulse-amplitude modulation (PAM) optical transmission, and also to investigate novel algorithms which could be applied to this application scenario. In order for a DSP technique to be considered an interesting solution for non-coherent WDM optical networks it has to effectively mitigate at least one of the three main impairments affecting such systems: bandwidth limitations, chromatic dispersion (CD) and noise (in optical or electrical domain). A series of algorithms are proposed and examined in this thesis, and their performance is analyzed by simulation and also experimentally in the laboratory: - Feed-forward equalization (FFE): this is the most common equalizer and it is basically employed in every high-speed non-coherent optical transmission. It can compensate high bandwidth limitations. - Maximum likelihood sequence estimation (MLSE): the MLSE is the optimum detector and thus provides the best performance when it comes to dealing with CD and bandwidth limitations. - Geometrical constellation shaping: in multilevel optical intensity modulation schemes the distance between amplitude levels can be adjusted (such that they are no longer equidistant) in order to increase the signal's tolerance to noise. - Probabilistic shaping: another technique designed specifically for multilevel modulation schemes; it adjusts the probability of each amplitude level such that the tolerance to optical noise is increased. - Partial response signaling (PRS): this is a DSP-based approach where a controlled inter-symbol interference (ISI) is intentionally introduced in such a way that the resulting signal requires less bandwidth. PRS can be customized to also mitigate CD impairment, effectively increasing transmission distances up to three times. - Digital pre-emphasis (DPE): this technique consists in applying the inverse of the transfer function of the system to the signal at the transmitter side which reduces the impact of bandwidth limitations on the signal at the receiver side. - Trellis-coded modulation (TCM): a modulation scheme that combines forward error correction (FEC) elements with set-partitioning techniques and multidimensional modulation to generate a signal that is more resistant to noise. - Multidimensional set-partitioned modulation: very similar with TCM but without any FEC elements. It has lower gains than TCM in terms of noise tolerance but is not so sensitive to ISI. By using the techniques enumerated above, this thesis demonstrates that is possible to achieve 100 Gbps/¿ optical transmission bitrate employing cost-effective components. Even more, bitrates higher than 200 Gbps are also demonstrated, indicating that non-coherent PAM is a viable cost-effective solution for next-generation 800 Gbps (4¿×200 Gbps) WDM transceivers. / Prodaniuc, C. (2019). Advanced Signal Processing for Pulse-Amplitude Modulation Optical Transmission Systems [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/117315 / TESIS

This master’s thesis is focused on sensory systems and analysis of such signals. In the frst part, a theoretical analysis of each sensory system is conducted. Followingly, appropriate flters were used to process these signals. The last part of this thesis deals with the analysis of measured data.

This master’s thesis is focused on sensory systems and analysis of such signals. In the frst part, a theoretical analysis of each sensory system is conducted. Followingly, appropriate flters were used to process these signals. The last part of this thesis deals with the analysis of measured data.

This master thesis deals with implementation of the radar sensor for adaptive cruise control system. It discusses used technologies and processes and documents implementation of signal processing serving for the purpose of adaptive cruise control. It also describes the testing on the real data gathered in traffic. Texas Instrument's AWR1843 radar module was used as the sensor. This sensor represents currently very popular milimeter wave technology radars. Result of this master thesis are two implemented systems processing digital signal. One of them is a prototype application of the adaptive cruise control system, which also visualises the data. The other is implemented firmware of radar module doing real-time on-chip signal processing according to adaptive cruise control logic.

The utilisation of personal computers for a conditioning of audio devices has shown a significant increase, since the digital signal processing (DSP) was introduced. The expansion of the DSP has allowed implementing analyses to obtain frequency and linear characteristics, distortion parameters (THD, THD+N, WHD, SINAD), a rate of crosstalk or a signal-to-noise ratio. In this work a software analyser is developed, which is able to obtain qualitative parameters of hardware audio devices that are connected with a sound card. For an efficient communication between the sound card and the personal computer the ASIO driver is used. The application is capable to measure audio effects that are implemented in VST plug-ins. The software is developed in C++ language and the implemented analyses are based on the AES17 recommendation.

In digital image correlation, an optical full-field analysis method that can determine displacements of an object under load, high-resolution images are preferable. One way to improve the resolution is to improve the camera hardware. This can be expensive, hence another way to enhance the image is by various image processing techniques increase the resolution of the image. There are several ways of doing this and these techniques are called super-resolution. In this thesisthe theory behind several different approaches to super-resolution is presented and discussed. The goal of this Thesis has been to investigate if super-resolutionis possible in a scene with moving objects as well as movement of the camera. It became clear early on that image registration, a step in many super-resolution methods that will be explained in this thesis, was of utmost importance, and a major part of the work became comparing image registration methods. Data has been recorded and then two different super-resolution algorithms have been evaluated on a data set showing that super-resolution is possible.