83 research outputs found
A Socially Aware Bayesian Model for Competitive Foraging
No full textAuthor(s): Ahmad, Sheeraz; Yu, Angel
Using information theoretic vector quantization for gmm based speaker verification
No full textPublication in the conference proceedings of EUSIPCO, Lausanne, Switzerland, 200
Automatic speaker recognition: modelling, feature extraction and effects of clinical environment
No full textSpeaker recognition is the task of establishing identity of an individual based on his/her voice. It has a significant potential as a convenient biometric method for telephony applications and does not require sophisticated or dedicated hardware. The Speaker Recognition task is typically achieved by two-stage signal processing: training and testing. The training process calculates speaker-specific feature parameters from the speech. The features are used to generate statistical models of different speakers. In the testing phase, speech samples from unknown speakers are compared with the models and classified.Current state of the art speaker recognition systems use the Gaussian mixture model (GMM) technique in combination with the Expectation Maximization (EM) algorithm to build the speaker models. The most frequently used features are the Mel Frequency Cepstral Coefficients (MFCC).This thesis investigated areas of possible improvements in the field of speaker recognition. The identified drawbacks of the current speaker recognition systems included: slow convergence rates of the modelling techniques and feature’s sensitivity to changes due aging of speakers, use of alcohol and drugs, changing health conditions and mental state. The thesis proposed a new method of deriving the Gaussian mixture model (GMM) parameters called the EM-ITVQ algorithm. The EM-ITVQ showed a significant improvement of the equal error rates and higher convergence rates when compared to the classical GMM based on the expectation maximization (EM) method.It was demonstrated that features based on the nonlinear model of speech production (TEO based features) provided better performance compare to the conventional MFCCs features.For the first time the effect of clinical depression on the speaker verification rates was tested. It was demonstrated that the speaker verification results deteriorate if the speakers are clinically depressed. The deterioration process was demonstrated using conventional (MFCC) features.The thesis also showed that when replacing the MFCC features with features based on the nonlinear model of speech production (TEO based features), the detrimental effect of the clinical depression on speaker verification rates can be reduced
Image Quality Assessment for Performance Evaluation of Focus Measure Operators
No full textThis paper presents the performance evaluation of eight focus measure operators namely Image CURV (Curvature), GRAE (Gradient Energy), HISE (Histogram Entropy), LAPM (Modified Laplacian), LAPV (Variance of Laplacian), LAPD (Diagonal Laplacian), LAP3 (Laplacian in 3D Window) and WAVS (Sum of Wavelet Coefficients). Statistical matrics such as MSE (Mean Squared Error), PNSR (Peak Signal to Noise Ratio), SC (Structural Content), NCC (Normalized Cross Correlation), MD (Maximum Difference) and NAE (Normalized Absolute Error) are used to evaluate stated focus measures in this research. . FR (Full Reference) method of the image quality assessment is utilized in this paper. Results indicate that LAPD method is comparatively better than other seven focus operators at typical imaging condition
Probabilistic and Hybrid Model Checking Deployments for Wireless Sensor Networks
No full textIn the early stages of system development, model checking is a good practice for
examining the WSNs (Wireless Sensor Networks). Model checking involves verifying
a system\'s properties based on the system\'s finite state model. For varying applications
like computers and wireless communication prior to expensive simulations, model
checking has become a vital requirement in order to investigate the performance and
reliability. In this paper for the first time, we are presenting probabilistic and hybrid
model checking tools which are being implemented to analyse and verify the WSN
applications and their examples. Here we are categorizing the model checking tools
and presenting how they have been used for the investigation of various behaviours of
WSN solutions. Consequently, this paper helps readers/researchers to choose the
appropriate model checking tool and to get benefited in shape of validating their
solutions. The paper has also highlighted the problems of existing model checking
tools within WSN domain
Experimental study on multi-channel waveform agile beamforming and testbed calibration
No full textIn this paper, a novel multi-channel waveform agile radar testbed - ASTAP (Advanced Space-Time Adaptive Processing) with eight transmit channels and a single receive channel to form a co-located Multiple-Input Single-Output (MISO) radar is presented. Based on current configuration, the ASTAP radar system possesses agility for synthesizing and transmitting independent waveforms via each transmit channel simultaneously via multi-channel Arbitrary Waveform Generator (AWG). Hardware imperfections influence on digitally created waveforms including limited-bits DAC (Digital-to-Analog Converter) quantization, inter-channel time- and phase-skew (and/or jitter), non-linearities introduced by high-frequency devices (RF amplifiers and mixers etc) and antenna dispersion effects has been studied experimentally.An end-to-end system-level digital calibration using Over-the-Air (OTA) channel measurements to minimize system hardware imperfections prior to transmission is proposed. Calibration accuracy for waveform transmit ambiguity functions, orthogonality in MISO transmissions, received signals separation and beamforming process for the synthesis of target azimuth distributions is examined and quantified. Front-end performance with different waveforms types for colored transmission and simultaneous MIMO is demonstrated and analysed. Extraction of the signals corresponding to each transmit channel from the composite received signal in a single receive channel exploiting waveforms orthogonality is studied experimentally.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Microwave Sensing, Signals & System
Multi-channel Waveform Agile Radar: Experimental performance evaluation of ASTAP radar system
No full textRecent advancements in Multiple-Input Multiple-Output (MIMO) radar techniques has created a paradigm shift in the overall radar technology to increase degrees of freedom in multi-function radar capabilities. The underlying principle of MIMO transmissions is to transmit independent waveforms from each antenna-element which do not interfere with other transmitted signals and establish wide illuminations which create multiple received signals back-scattered from the same target under observation to provide more information on the target aspects. One other principle is called colored transmission, by simultaneously radiating specific waveforms from each antenna-element/sub-array in different directions to achieve ‘space-time coding’. This can be explained as colored spatial distribution (multiple coded beams to probe the radar environment) instead of the white spatial distribution (single wide beam), such that the transmitted signals are now function of time as well as space. Recently, a novel multi-channel waveform agile demonstrator namely ASTAP (Advanced Space-Time Adaptive Processing) radar system has been designed and developed in Microwave Sensing, Signals and Systems (MS3) group. It consists of eight transmit channels with a single receive channel and hence can also be called as co-located Multiple-Input Single-Output (MISO) radar. The ASTAP radar system is capable of generating and transmitting independent waveforms via multi-channel Arbitrary Waveform Generator(AWG) simultaneously . However, the transmission of different coded waveforms with a radar system such as ASTAP demonstrator has some major challenges to be addressed first. These challenges include the impact of AWG on digital-domain generation of waveforms including limited-bits quantization errors, time- and phase-skew ( and/or jitter), influence of high-frequency up-conversion hardware components such as RF mixers (as non-linear devices) and antenna dispersion effects. First novelty of this thesis work is to investigate the influence of these system imperfections on waveform transmit ambiguity functions, waveform orthogonality in MISO transmissions, received signals separation and beamforming process for the synthesis of target azimuth distributions. It follows that an end-to-end system-level calibration to compensate these system imperfections on transmit side for different waveforms also serves as the second novelty of this thesis work and has been demonstrated with ASTAP radar system. For system performance analysis and beamforming applications, Over-the-Air (OTA) channel measurements have been done to compensate the ASTAP hardware distortions significantly and obtain the near-ideal waveform responses. Furthermore, it is investigated that to what extent it is possible to separate signals corresponding to each transmit channel from the composite received signal in a single receive channel. This study is extended further to generate and transmit two orthogonal beams occupying the same frequency band simultaneously and the corresponding transmit radiation patterns are recovered from the composite received signal matched filtering. Finally, conclusions along with future aspects and recommendations have been discussed.Electrical Engineering | Signals and System
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