System approach to robust acoustic echo cancellation through semi-blind source separation based on independent component analysis

We live in a dynamic world full of noises and interferences. The conventional acoustic echo cancellation (AEC) framework based on the least mean square (LMS) algorithm by itself lacks the ability to handle many secondary signals that interfere with the adaptive filtering process, e.g., local speech and background noise. In this dissertation, we build a foundation for what we refer to as the system approach to signal enhancement as we focus on the AEC problem. We first propose the residual echo enhancement (REE) technique that utilizes the error recovery nonlinearity (ERN) to "enhances" the filter estimation error prior to the filter adaptation. The single-channel AEC problem can be viewed as a special case of semi-blind source separation (SBSS) where one of the source signals is partially known, i.e., the far-end microphone signal that generates the near-end acoustic echo. SBSS optimized via independent component analysis (ICA) leads to the system combination of the LMS algorithm with the ERN that allows for continuous and stable adaptation even during double talk. Second, we extend the system perspective to the decorrelation problem for AEC, where we show that the REE procedure can be applied effectively in a multi-channel AEC (MCAEC) setting to indirectly assist the recovery of lost AEC performance due to inter-channel correlation, known generally as the "non-uniqueness" problem. We develop a novel, computationally efficient technique of frequency-domain resampling (FDR) that effectively alleviates the non-uniqueness problem directly while introducing minimal distortion to signal quality and statistics. We also apply the system approach to the multi-delay filter (MDF) that suffers from the inter-block correlation problem. Finally, we generalize the MCAEC problem in the SBSS framework and discuss many issues related to the implementation of an SBSS system. We propose a constrained batch-online implementation of SBSS that stabilizes the convergence behavior even in the worst case scenario of a single far-end talker along with the non-uniqueness condition on the far-end mixing system. The proposed techniques are developed from a pragmatic standpoint, motivated by real-world problems in acoustic and audio signal processing. Generalization of the orthogonality principle to the system level of an AEC problem allows us to relate AEC to source separation that seeks to maximize the independence, hence implicitly the orthogonality, not only between the error signal and the far-end signal, but rather, among all signals involved. The system approach, for which the REE paradigm is just one realization, enables the encompassing of many traditional signal enhancement techniques in analytically consistent yet practically effective manner for solving the enhancement problem in a very noisy and disruptive acoustic mixing environment.PhDCommittee Chair: Biing-Hwang Juang; Committee Member: Brani Vidakovic; Committee Member: David V. Anderson; Committee Member: Jeff S. Shamma; Committee Member: Xiaoli M

Low cost antenna array based drone tracking device for outdoor environment

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2019.Aplicações para técnicas de Direção de Chegada (DoA) têm crescido drasticamente em várias áreas, desde os tradicionais sistemas de comunicação sem fio e operações de resgate até os sistemas GNSS e rastreamento de drones. Particularmente, as forças policiais e as empresas de segurança têm voltado sua atenção para os dispositivos de rastreamento de drones, devido ao número de acidentes e incidentes envolvendo estes Veículos Aéreos não Tripulados (VANTs). Agora, novos sistemas e dispositivos que fornecem segurança a cidadãos e clientes cresceram e ganharam espaço no mercado. Para detectar a presença de drones e rastreá-los existe uma variedade de soluções altamente caras no mercado. Porém, a estimativa da localização de um alvo pode ser obtida usando hardware barato, comprado facimente no mercado, e com técnicas de Direção de Chegada. Data esta estimativa, algumas ações podem ser tomadas pelo responsável pela segurança no local. Trabalhos anteriores na estimativa de direção de chegada usando arranjo de antenas foram propostos, mas sem uma abordagem prática. Nesta dissertação, propõe-se um dispositivo de rastreamento de drones baseado em arranjo de antenas de baixo custo para ambientes externos. A solução proposta é dividida em partes de hardware e software. A parte de hardware do dispositivo proposto é baseada em componentes fáceis de serem encontrados no mercado, como um arranjo de antena omnidirecional, uma plataforma SDR (Rádio Definido por Software) de 4 canais com frequência de portadora variando de 70 MHz a 6 GHz, uma placa-mãe FPGA e um laptop. A parte do software inclui algoritmos para calibração, seleção de ordem de modelo (MOS) e estimativa de DoA, incluindo etapas específicas de pré-processamento para aumentar a precisão dos cálculos para os métodos de DoA. Avaliamos o desempenho de nossa solução de baixo custo, proposta para ambientes externos, e de acordo com as medições de campo, mostra-se que, quando o transmissor está na posição frontal, ou seja, com um DoA variando de -60° a 60°, o máximo e a média dos erros de DoA são 6° e 1,6°, respectivamente.Applications of Direction of Arrival (DoA) techniques have dramatically increased in various areas ranging from the traditional wireless communication systems and rescue operations to GNSS systems and drone tracking. Particularly, police forces and security companies have drawn their attention to drone tracking devices, due to the number of accidents and incidents involving Unmanned Aerial Vehicles (UAVs). Now, new systems and devices that provide the safeness of citizens and clients, have grown and gained space on the market. In order to detect the presence of drones and to track them, there is a variety of highly expensive solutions in the market. In this way the estimation of a target’s location can be obtained using off-the-shelf hardware with Direction of Arrival techniques. Consequently some actions can be taken by the responsible for the security in that place. Previous works in DoA estimation using antenna arrays have been proposed but with no practical approach. In this dissertation, it is proposed a low cost antenna array based drone tracking device for outdoor environments. The proposed solution is divided into hardware and software parts. The hardware part of the proposed device is based on off-the-shelf components such as an omni-directional antenna array, a 4 channel Software Defined Radio (SDR) platform with carrier frequency ranging from 70 MHz to 6 GHz, a FPGA motherboard and a laptop. The software part includes algorithms for calibration, model order selection (MOS) and DoA estimation, including specific pre-processing steps to increase the DoA accuracy. The performance of our proposed low cost solution is evaluated in outdoor scenarios. According to our measurement campaigns, it is shown that, when the array is in the front fire position, i.e. with a DoA ranging from -60° to 60°, the maximum and the average DoA errors are 6° and 1,6°, respectively

Abstracts on Radio Direction Finding (1899 - 1995)

The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion

High accuracy and low complexity adaptive Generalized Sidelobe Cancelers for colored noise scenarios

The Generalized Sidelobe Canceler (GSC) is a beamforming scheme which is applied in many fields such as audio, RADAR, SONAR and telecommunications. Recently, the adaptive Reduced Rank GSC (RR-GSC) has been proposed for applications with a large number of sensors. Due to its dimensionality reduction step, the adaptive RR-GSC achieves an enhanced performance in comparison with the standard GSC. However, both standard GSC and RR-GSC have their performance drastically degraded in the presence of colored noise. In this paper, we propose to extend further the GSC and the RR-GSC for colored noise scenarios. As shown in this paper, such improvement in colored noise scenarios can be obtained by incorporating a stochastic or a deterministic prewhitening step in the GSC and RR-GSC algorithms. Since the prewhitening increases the computational complexity, a block-wise reduced rank stochastic gradient GSC beamformer is also proposed. The block-wise step allows only one prewhitening step per block while in the previous schemes one per sample was needed. Another proposed advance in colored noise scenarios is the incorporation of the Vandermonde Invariance Transform (VIT). The VIT works as a pre-beamformer which reduces the interferent power of the undesired sources and the colored noise effect. We show by means of simulations the improved results even for highly correlated scenarios

High accuracy and low complexity adaptive Generalized Sidelobe Cancelers for colored noise scenarios

The Generalized Sidelobe Canceler (GSC) is a beamforming scheme which is applied in many fields such as audio, RADAR, SONAR and telecommunications. Recently, the adaptive Reduced Rank GSC (RR-GSC) has been proposed for applications with a large number of sensors. Due to its dimensionality reduction step, the adaptive RR-GSC achieves an enhanced performance in comparison with the standard GSC. However, both standard GSC and RR-GSC have their performance drastically degraded in the presence of colored noise. In this paper, we propose to extend further the GSC and the RR-GSC for colored noise scenarios. As shown in this paper, such improvement in colored noise scenarios can be obtained by incorporating a stochastic or a deterministic prewhitening step in the GSC and RR-GSC algorithms. Since the prewhitening increases the computational complexity, a block-wise reduced rank stochastic gradient GSC beamformer is also proposed. The block-wise step allows only one prewhitening step per block while in the previous schemes one per sample was needed. Another proposed advance in colored noise scenarios is the incorporation of the Vandermonde Invariance Transform (VIT). The VIT works as a pre-beamformer which reduces the interferent power of the undesired sources and the colored noise effect. We show by means of simulations the improved results even for highly correlated scenarios