Kalman tracking of linear predictor and harmonic noise models for noisy speech enhancement

This paper presents a speech enhancement method based on the tracking and denoising of the formants of a linear prediction (LP) model of the spectral envelope of speech and the parameters of a harmonic noise model (HNM) of its excitation. The main advantages of tracking and denoising the prominent energy contours of speech are the efficient use of the spectral and temporal structures of successive speech frames and a mitigation of processing artefact known as the ‘musical noise’ or ‘musical tones’.The formant-tracking linear prediction (FTLP) model estimation consists of three stages: (a) speech pre-cleaning based on a spectral amplitude estimation, (b) formant-tracking across successive speech frames using the Viterbi method, and (c) Kalman filtering of the formant trajectories across successive speech frames.The HNM parameters for the excitation signal comprise; voiced/unvoiced decision, the fundamental frequency, the harmonics’ amplitudes and the variance of the noise component of excitation. A frequency-domain pitch extraction method is proposed that searches for the peak signal to noise ratios (SNRs) at the harmonics. For each speech frame several pitch candidates are calculated. An estimate of the pitch trajectory across successive frames is obtained using a Viterbi decoder. The trajectories of the noisy excitation harmonics across successive speech frames are modeled and denoised using Kalman filters.The proposed method is used to deconstruct noisy speech, de-noise its model parameters and then reconstitute speech from its cleaned parts. Experimental evaluations show the performance gains of the formant tracking, pitch extraction and noise reduction stages

Digital Linearization of High Capacity and Spectrally Efficient Direct Detection Optical Transceivers

Metropolitan area networks are experiencing unprecedented traffic growth. The provision of information and entertainment supported by cloud services, broadband video and mobile technologies such as long-term evolution (LTE) and 5G are creating a rapidly increasing demand for bandwidth. Although wavelength division multiplexing (WDM) architectures have been introduced into metro transport networks to provide significant savings over single-channel systems, to cope with the ever-increasing traffic growth, it is urgently required to deploy higher data rates (100 Gb/s and beyond) for each WDM channel. In comparison to dual-polarization digital coherent transceivers, single-polarization and single photodiode-based direct-detection (DD) transceivers may be favourable for metropolitan, inter-data centre and access applications due to their use of a simple and low-cost optical hardware structure. Single sideband (SSB) quadrature amplitude modulation (QAM) subcarrier modulation (SCM) is a promising signal format to achieve high information spectral density (ISD). However, due to the nonlinear effect termed signal-signal beat interference (SSBI) caused by the square-law detection, the performance of such SSB SCM DD systems is severely degraded. Therefore, it is essential to develop effective and low-complexity linearization techniques to eliminate the SSBI penalty and improve the performance of such transceivers. Extensive studies on SSB SCM DD transceivers employing a number of novel digital linearization techniques to support high capacity (≥ 100 Gb/s per channel) and spectrally-efficient (net ISD > 2 b/s/Hz) WDM transmission covering metropolitan reach scenarios (up to 240 km) are described in detail in this thesis. Digital modulation formats that can be used in DD links and the corresponding transceiver configurations are firstly reviewed, from which the SSB SCM signalling format is identified as the most promising format to achieve high data rates and ISDs. Following this, technical details of the digital linearization approaches (iterative SSBI cancellation, single-stage linearization filter and simplified non-iterative SSBI cancellation, two-stage linearization filter, Kramers-Kronig scheme) considered in the thesis are presented. Their compensation performance in a dispersion pre-compensated (Tx-EDC) 112 Gb/s per channel 35 GHz-spaced WDM SSB 16-QAM Nyquist-SCM DD system transmitting over up to 240 km standard single-mode fibre (SSMF) is assessed. Net ISDs of up to 3.18 b/s/Hz are achieved. Moreover, we also show that, with the use of effective digital linearization techniques, further simplification of the DD transceivers can be realized by moving electronic dispersion compensation from the transmitter to the receiver without sacrificing performance. The optical ISD limit of SSB SCM DD system finally explored through experiments with higher-order modulation formats combined with effective digital linearization techniques. 168 Gb/s per channel WDM 64-QAM signals were successfully transmitted over 80 km, achieving a record net optical ISD of 4.54 b/s/Hz. Finally, areas for further research are identified

Heterogeneous LTE/ Wi-Fi architecture for intelligent transportation systems

Intelligent Transportation Systems (ITS) make use of advanced technologies to enhance road safety and improve traffic efficiency. It is anticipated that ITS will play a vital future role in improving traffic efficiency, safety, comfort and emissions. In order to assist the passengers to travel safely, efficiently and conveniently, several application requirements have to be met simultaneously. In addition to the delivery of regular traffic and safety information, vehicular networks have been recently required to support infotainment services. Previous vehicular network designs and architectures do not satisfy this increasing traffic demand as they are setup for either voice or data traffic, which is not suitable for the transfer of vehicular traffic. This new requirement is one of the key drivers behind the need for new mobile wireless broadband architectures and technologies. For this purpose, this thesis proposes and investigates a heterogeneous IEEE 802.11 and LTE vehicular system that supports both infotainment and ITS traffic control data. IEEE 802.11g is used for V2V communications and as an on-board access network while, LTE is used for V2I communications. A performance simulation-based study is conducted to validate the feasibility of the proposed system in an urban vehicular environment. The system performance is evaluated in terms of data loss, data rate, delay and jitter. Several simulation scenarios are performed and evaluated. In the V2I-only scenario, the delay, jitter and data drops for both ITS and video traffic are within the acceptable limits, as defined by vehicular application requirements. Although a tendency of increase in video packet drops during handover from one eNodeB to another is observed yet, the attainable data loss rate is still below the defined benchmarks. In the integrated V2V-V2I scenario, data loss in uplink ITS traffic was initially observed so, Burst communication technique is applied to prevent packet losses in the critical uplink ITS traffic. A quantitative analysis is performed to determine the number of packets per burst, the inter-packet and inter-burst intervals. It is found that a substantial improvement is achieved using a two-packet Burst, where no packets are lost in the uplink direction. The delay, jitter and data drops for both uplink and downlink ITS traffic, and video traffic are below the benchmarks of vehicular applications. Thus, the results indicate that the proposed heterogeneous system offers acceptable performance that meets the requirements of the different vehicular applications. All simulations are conducted on OPNET Network Modeler and results are subjected to a 95% confidence analysis

Statistical single channel source separation

PhD ThesisSingle channel source separation (SCSS) principally is one of the challenging fields in signal processing and has various significant applications. Unlike conventional SCSS methods which were based on linear instantaneous model, this research sets out to investigate the separation of single channel in two types of mixture which is nonlinear instantaneous mixture and linear convolutive mixture. For the nonlinear SCSS in instantaneous mixture, this research proposes a novel solution based on a two-stage process that consists of a Gaussianization transform which efficiently compensates for the nonlinear distortion follow by a maximum likelihood estimator to perform source separation. For linear SCSS in convolutive mixture, this research proposes new methods based on nonnegative matrix factorization which decomposes a mixture into two-dimensional convolution factor matrices that represent the spectral basis and temporal code. The proposed factorization considers the convolutive mixing in the decomposition by introducing frequency constrained parameters in the model. The method aims to separate the mixture into its constituent spectral-temporal source components while alleviating the effect of convolutive mixing. In addition, family of Itakura-Saito divergence has been developed as a cost function which brings the beneficial property of scale-invariant. Two new statistical techniques are proposed, namely, Expectation-Maximisation (EM) based algorithm framework which maximizes the log-likelihood of a mixed signals, and the maximum a posteriori approach which maximises the joint probability of a mixed signal using multiplicative update rules. To further improve this research work, a novel method that incorporates adaptive sparseness into the solution has been proposed to resolve the ambiguity and hence, improve the algorithm performance. The theoretical foundation of the proposed solutions has been rigorously developed and discussed in details. Results have concretely shown the effectiveness of all the proposed algorithms presented in this thesis in separating the mixed signals in single channel and have outperformed others available methods.Universiti Teknikal Malaysia Melaka(UTeM), Ministry of Higher Education of Malaysi

Gold/graphene fractals as tunable plasmonic devices

Graphene, an atomically thin sheet of carbon atoms arranged in a honeycomb geometry, is attracting unique attention thanks to its extraordinary mechanical, electrical and optical properties. This thesis work concerns the realization of graphene-based nanoscale devices for novel plasmonic applications. We focus mainly on gold/graphene (Au/G) structures designed to display plasmonic multiresonances in the visible range thanks to the nanostructure geometry based on the Sierpinski carpet (SC) deterministic fractal

Extremely high data-rate, reliable network systems research

Significant progress was made over the year in the four focus areas of this research group: gigabit protocols, extensions of metropolitan protocols, parallel protocols, and distributed simulations. Two activities, a network management tool and the Carrier Sensed Multiple Access Collision Detection (CSMA/CD) protocol, have developed to the point that a patent is being applied for in the next year; a tool set for distributed simulation using the language SIMSCRIPT also has commercial potential and is to be further refined. The year's results for each of these areas are summarized and next year's activities are described