Nithin George

Nithin George
Indian Institute of Technology Gandhinagar · Faculty of Electrical Engineering

Doctor of Philosophy

About

94
Publications
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1,433
Citations

Publications

Publications (94)
Article
Full-text available
Monitoring the corrosion of steel rebars is paramount to ensuring the safety and serviceability of reinforced concrete (RC) structures. Conventional electro-chemical techniques can provide an overall estimate of the extent of corrosion. However, a detailed account of the extent of corrosion would help in understanding the residual strength of corro...
Article
Nonlinear spline adaptive filters are a class of adaptive filters for modelling nonlinear systems. To improve the convergence performance of existing nonlinear spline adaptive filters (SAFs), in this paper, we propose a low rank approximation for different SAF models by incorporating the technique of nearest Kronecker product decomposition. We cons...
Article
In the past years, the generalized maximum correntropy criterion (GMCC) has been widely used in adaptive filters to provide robust behavior under non-Gaussian/impulsive noise environments. However, GMCC-based adaptive filters are affected by high steady-state misalignment. In order to enhance the robustness under non-Gaussian noise environments and...
Article
Phase-mode array processing which utilizes the spherical harmonics decomposition offers a useful framework for spherical microphone arrays. In the modal domain, one of the major applications of spherical arrays is acoustic beamforming. Usually, beamforming is performed by minimizing the power of the beamformer output with a distortionless constrain...
Article
This brief introduces a novel cost function framework for developing robust algorithms for adaptive filtering by embedding the standard cost function into the arctangent framework. This proposed framework is called the arctangent cost function framework. Based on this, we propose an arctangent family of robust algorithms for adaptive filtering. The...
Article
Diffusion affine projection algorithms have the ability to de-correlate the input signal and have faster convergence but with the expense of increased computational complexity. Moreover, traditional diffusion affine projection algorithms consider the noise to be of Gaussian nature. However, practically this noise can be non-Gaussian which can signi...
Article
The recently proposed affine projection Versoria (APV) algorithm has been widely used over other affine based algorithms due to its robustness against impulsive noises. However, the performance of the APV algorithm suffers from high steady state misalignment. In order to overcome this, we propose affine projection Champernowne adaptive filter (APCM...
Article
An exhaustive review of adaptive signal processing schemes which are robust, sparsity-aware and robust as well as sparsity-aware has been carried out in this paper. Conventional robust learning approaches as well as the ones based on information theoretic methods have been included in the review. Further, adaptive filtering schemes which take advan...
Article
Spline nonlinear adaptive filters are well known for their ability to efficiently model nonlinear systems while having low computational complexity. However, the performance of traditional spline adaptive filter degrades in the presence of impulsive disturbances. For improving the performance of spline adaptive filters in impulsive noise scenarios,...
Article
In recent years, correntropy-based algorithms which include maximum correntropy creterion (MCC), generalized MCC (GMCC), kernel MCC (KMCC) and hyperbolic cosine function-based algorithms such as hyperbolic cosine adaptive filter (HCAF), logarithmic HCAF (LHCAF), least lncosh (Llncosh) have been widely utilized in the adaptive filtering due to their...
Article
In distributed wireless sensor networks, geographically distributed sensors cooperate wirelessly with each other. While sensing from the environment, the signals from these sensors are often contaminated by noise. Traditional diffusion algorithms for distributed estimation consider this noise to be Gaussian in nature. However, in practice this nois...
Article
A linear-in-the-parameters nonlinear filter consists of a functional expansion block, which expands the input signal to a higher dimensional space nonlinearly, followed by an adaptive weight network. The number of weights to be updated depends on the type and order of the functional expansion used. When applied to a nonlinear system identification...
Article
In this letter, we propose to exploit the array motion of sparse circular arrays (SCA) on a rotating platform to increase the degrees of freedom (DOF) (i.e. the number of unique spatial lags) associated with the rotating array when compared to the array on a fixed platform. This increases the total number of sources that can be resolved by the rota...
Article
The constrained least mean square algorithm is extensively used for adaptive filtering applications which need to satisfy a set of linear constraints. However, it is not robust when non-Gaussian or impulsive noise is present at the error sensor. To effectively overcome this issue, in this letter, we propose the constrained generalized maximum corre...
Article
Acoustic feedback is a frequently encountered problem in assistive listening devices (ALDs). Feedback paths in ALDs are typically sparse in nature and sparsity aware adaptive feedback cancellers can improve perceived audio quality under such scenarios. In an endeavour to improve the feedback canceller performance, a decorrelated polynomial zero att...
Article
In an adaptive feedback cancellation (AFC) scenario, it is essential for an algorithm to track and cancel the feedback signal as quickly as possible. We analyze typical feedback paths in hearing aids and show that they exhibit a low-rank nature. Further, to exploit this knowledge and improve the convergence and tracking performance for AFC, we prop...
Article
A robust adaptive filter is usually unaffected by spurious disturbances at the error sensor. In an endeavour to improve robustness of the adaptive filter, a novel modified Champernowne function (MCF) is proposed as a robust norm and the corresponding robust Champernowne adaptive filter (CMAF) is derived. To improve modelling accuracy and convergenc...
Article
Non-uniform linear arrays have the ability to provide higher degrees of freedom (DOF) than conventional uniform linear arrays (ULAs) by making use of their virtual coarray. However, some non-uniform arrays such as coprime arrays have holes in their virtual array. In order to utilize the full DOF of such arrays, coarray interpolation is performed. C...
Article
Robust adaptive signal processing algorithms based on a generalized maximum correntropy criterion (GMCC) suffers from high steady state misalignment. In an endeavour to achieve lower steady state misalignment, in this letter we propose a generalized hyperbolic secant function (GHSF) as a robust norm and derive the generalized hyperbolic secant adap...
Article
Full-text available
Ultrasonic scanning can present a detailed map of the invisible internal degradation of objects. However, their utility is limited in case of built facilities as their dimensions are too large for the currently used piezoelectric transducers to penetrate. This paper presents an investigation with high power Laser ultrasonic guided waves combined wi...
Article
This paper proposes a new robust learning strategy, which is based on a Weibull M-transform function. The suitability of the Weibull M-transform function as a robust norm has been investigated for different shape and scale parameters, and a Weibull M-transform least mean square (WMLMS) algorithm has been developed. Further, the bound of learning ra...
Article
Linear-in-the-parameters nonlinear controllers are widely used for active noise cancellation (ANC) in the presence of nonlinearities in the system. However, the performance of such controllers deteriorates significantly in highly nonlinear systems and also in the presence of nonlinear harmonic distortion. To overcome these issues, a kernel filtered...
Article
Recently, the logarithmic hyperbolic cosine adaptive filter (LHCAF) was proposed and was seen to demonstrate excellent robustness against impulsive interference. However, for the modelling of sparse systems, it may not provide optimal performance as it does not take into account the sparse nature of the system. To improve the modelling accuracy and...
Article
Low complexity and ease of implementation provided by zero-attraction-based least mean square (LMS) algorithms have made them popular candidates for sparse system identification. In this brief, a new sparsity aware norm based on a modified Versoria function is proposed, and utilized to develop a novel Versoria zero-attraction LMS (VZA-LMS) algorith...
Article
The adaptive exponential functional link network (AEFLN) is a recently introduced novel linear-in-the-parameters nonlinear filter and is used in numerous nonlinear applications, including system identification, active noise control, and echo cancellation. The improved modeling accuracy offered by AEFLN for different nonlinear applications can be at...
Article
This paper presents a non-linear multi-channel active noise control (ANC) scheme based on a set of adaptive spline filters as the component controllers. An adaptive spline filter comprises an adaptive finite impulse response (FIR) structure, which is followed by an adaptive spline activation function. A suitable learning rule is developed that upda...
Article
Adaptive exponential functional link network (AEFLN) is a recently introduced linear-in-the-parameters nonlinear filter. In an attempt to improve the performance of AEFLN, an improved AEFLN (IAEFLN) which employs independent decay rates for each exponentially varying sinusoidal basis function, has been proposed in this brief. The update rules for t...
Article
Zero-attraction-based adaptive filters are widely used for sparse system identification, where a suitable penalty function is integrated with the least mean square (LMS) framework to improve the convergence behavior of the identification process. In this brief, we have made an attempt to implement some of the most popular zero-attracting algorithms...
Chapter
Evolutionary-computing-algorithm-based nonlinear active noise control (ANC) removes the requirement of secondary path modeling, which is essential for proper functioning of a conventional gradient-descent-approach based ANC system. However, the noise mitigation capability of such algorithms is largely dependent on the proper selection of the agent...
Article
A forward two channel blind source separation scheme can be used as a effective method for speech enhancement. In such a scheme, two mixed sound signals are used as inputs to estimate the original signals which created these mixtures. In an endeavour to enhance the speech quality, an attempt has been made in this paper to design a two channel blind...
Article
An adaptive room equalization scheme is usually employed to compensate for the distortion of sound produced by the room impulse response, thereby offering an improved listening experience. In a conventional adaptive room equalizer, an adaptive filter updated using a filtered-x least mean square (FxLMS)algorithm is used to achieve room equalization....
Article
Adaptive exponential functional link network (AEFLN) is a recently developed linear-in-the-parameters nonlinear adaptive filter. It has been observed that the convergence performance of the AEFLN filter deteriorates in the presence of colored and/or correlated inputs. To overcome this issue, an affine projection algorithm (APA) based AEFLN (AEFLN-A...
Article
Distributed arithmetic (DA)-based approximate structures are used for efficient implementation of inner-products in various error-resilient applications. In the existing literature, most of these approximate architectures are developed by truncating the least significant bits (LSBs) of the inputs and/or the multiplying coefficients. The existing wo...
Conference Paper
Full-text available
An attempt has been made in this paper to simulate active noise control (ANC) in a three dimensional space using computational fluid dynamics and pressure acoustics. We have considered a rectangular box, with primary and secondary sources at the two opposite sides of the box. A model of ANC has been developed, which considers a cardboard surface an...
Article
This paper presents a new technique for discerning corrosion in steel bars using guided ultrasonic waves with an improved signal processing technique. A mild steel bar has been subjected to accelerated corrosion. Information concerning variation in spectral traits associated with the spread of corrosion has been discerned. Dispersion curves for the...
Article
Cell penetrating peptides (CPPs) facilitate the transport of pharmacologically ac- tive molecules, such as plasmid DNA, short interfering RNA (siRNA), nanoparticles, and small peptides. The accurate identification of new and unique CPPs is the ini- tial step to gain insight into CPP activity. Experiments can provide detailed insight into the cell-p...
Article
Single constant multiplication (SCM) and multiple constant multiplications (MCM) are among the most popular schemes used for low-complexity shift-add implementation of finite impulse response (FIR) filters. While SCM is used in the direct form realization of FIR filters, MCM is used in the transposed direct form structures. Very often, the hybrid f...
Article
The feedback cancellation performance of behind the ear hearing aids can be improved by employing two microphones in the feedback cancellation process. A frequency domain implementation of feedback cancellation in a two microphone behind the ear hearing aid has been proposed in this paper. A frequency domain step size control scheme has been furthe...
Article
Adaptive room equalization aims at providing a listener with an audio experience, which is very close to the original audio signal. The equalizer, which is an adaptive filter, compensates for the disturbance in the audio signal contributed by the impulse response of the room. One of the most popular algorithms employed for the design of an adaptive...
Article
Full-text available
Parameter identification of bilinear systems has been considered as an evolutionary computing algorithm based optimization problem in this paper. A new Levy shuffled frog leaping algorithm (LSFLA), which is an improved version of the conventional shuffled frog leaping algorithm (SFLA), has been designed and has been applied for this parameter ident...
Article
Cancelling the effect of acoustic feedback is a challenging task in the design of a behind the ear digital hearing aid. In traditional behind the ear digital hearing aids, feedback cancellation is usually achieved using an adaptive finite impulse response filter, the weights of which are updated using a suitable learning rule. However, the impulse...
Article
Wireless sensor networks, including wireless acoustic sensor networks, have found applications in diverse areas including hearing aids, hands-free telephony and target tracking. The objective of this brief is to introduce a new sparsity regularization parameter in sparse distributed network estimation, to achieve a better estimation accuracy in com...
Article
Active sound profiling, or active noise equalization strategies have been proposed to achieve spectral shaping of a primary disturbance signal. The control algorithms proposed to achieve such spectral shaping have either suffered from poor robustness to plant modelling uncertainties or required high levels of control effort. To improve the robustne...
Article
Acoustic feedback cancellation is one of the challenging tasks in the design of a behind the ear (BTE) digital hearing aid. This feedback cancellation is usually achieved using an adaptive filter. The finite correlation between the desired microphone input signal and the input signal to the loudspeaker results in a biased estimation of the adaptive...
Article
A new nonlinear filter, which employs an adaptive spline function as the basis function is designed in this paper. The input signal to this filter is used to generate suitable parameters to update the control points in a spline function. The update rule for updating the control points have been derived and a mean square analysis has been carried ou...
Article
Nonlinear active noise control (ANC) systems, which employ a nonlinear filter as the adaptive controller is not robust when the primary noise to be mitigated has a non-Gaussian distribution. The algorithm which updates the weights of the controller may even diverge for some higher magnitude primary noise signals. With an objective to improve the ro...
Article
Sparse learning algorithms for system identification differ from their non-sparse counterparts in their improved ability in quickly identifying the zero coefficients in a sparse system. This improvement has been achieved using the principle of zero attraction, whereby the near zero coefficients of the model are forced to zero. In order to further i...
Conference Paper
S transform, which is a powerful time frequency analysis method, has found applications in diverse areas of science and technology. The computational load offered by the S transform increases with increase in the length of the time series which is analysed. In an endeavour to reduce the computational load for time series which is sparse in the freq...
Conference Paper
Traditional active noise control (ANC) systems, which uses a fixed tap length adaptive filter as the controller may lead to non optimal noise mitigation. In addition, the conventional filtered-x least mean square algorithm based ANC schemes fail to effectively perform noise cancellation in the presence of nonlinearities in the ANC environment. In o...
Article
A novel nonlinear filter, which incorporates the concept of exponential sinusoidal models into nonlinear filters based on functional link networks (FLNs) has been developed in this paper. The proposed filter is designed to provide improved convergence characteristics over traditional FLN filters. The conventional trigonometric FLN may be considered...
Article
An exhaustive review on the use of structured stochastic search approaches towards system identification and digital filter design is presented in this paper. In particular, the paper focuses on the identification of various systems using infinite impulse response adaptive filters and Hammerstein models as well as on the estimation of chaotic syste...
Article
Implementation of a feed-forward active noise control (ANC) system in a short duct may cause acoustic feedback between the active loudspeaker and the reference microphone. The conventional filtered-x least mean square (FxLMS) algorithm based ANC systems are not designed to handle this situation. Similarly, an FxLMS algorithm based ANC system fails...
Conference Paper
Full-text available
Adaptive room equalization is a technique which compensates for the modification of a sound signal caused by the impulse response of the room in which the sound is played. Room impulse responses as well as the impulse response of the equalizer are generally sparse in nature. However, traditional adaptive room equalizers are not designed to make use...
Article
A spline adaptive filter (SAF) based nonlinear active noise control (ANC) system is proposed in this paper. The SAF consists of a linear network of adaptive weights in cascade with an adaptive nonlinear network. The nonlinear network, in-turn consists of an adaptive look-up table followed by a spline interpolation network and forms an adaptive acti...
Article
Full-text available
GPR often encounters difficulty in visualizing the buried target when signals are weak and enveloped by noise, despite using the best of existing GPR data analysis tools. In this study, new method has been proposed based on modified S-transform to analyze weak signals of GPR data. The time–frequency analysis has been implemented to capture the chan...
Article
An attempt has been made in this paper to model a nonlinear system using a Hammerstein model. The Hammerstein model considered in this paper is a functional link artificial neural network (FLANN) in cascade with an adaptive infinite impulse response (IIR) filter. In order to avoid local optima issues caused by conventional gradient descent training...
Conference Paper
Full-text available
In this paper, an improved interior search algorithm (ISA) is designed by incorporating Le´vy flight for solving optimisation problems. Le´vy flight pattern seen in some birds, is a special type of movement along a straight line followed by sudden turns in random directions. The convergence rate of ISA is improved using the principles of Le´vy flig...
Conference Paper
This paper presents the design of an adaptive channel equalizer which is based on the recently proposed krill herd (KH) algorithm. The channel equalization problem, which is conventionally solved using gradient descent approaches, has been formulated as an evolutionary computing (EC) algorithm based optimization task. The performance of the propose...
Article
This paper presents a cuckoo search algorithm (CSA) based adaptive infinite impulse response (IIR) system identification scheme. The proposed scheme prevents the local minima problem encountered in conventional IIR modeling mechanisms. The performance of the new method has been compared with that obtained by other evolutionary computing algorithms...
Conference Paper
A novel online secondary path modeling scheme for active noise control (ANC) systems based on the Generalized Levinson Durbin (GLD) algorithm is proposed in this paper. A short duration zero mean white Gaussian noise is injected into the system using an active loudspeaker and the GLD algorithm is employed to recursively estimate the secondary path....
Article
This paper presents a set of single layer low complexity nonlinear adaptive models for efficient identification of dynamic systems in the presence of outliers in the training signal. The weights of the new models have been updated using a new robust learning algorithm. The proposed robust algorithm is based on adaptive minimization of Wilcoxon norm...
Article
This paper proposes a nonlinear active noise control (ANC) system based on convex combination of a functional link artificial neural network (FLANN) and a Volterra filter. Simulation study reveals enhanced noise cancelation performance of the proposed ANC system over the ones based on its component filters.
Conference Paper
This paper proposes an improved face recognition scheme using spectral domain features and a multi-layer classification mechanism. The efficiency of the new scheme, in correctly classifying images has been tested through an OpenCV implementation using a benchmark face database. The improved classification accuracy of the proposed method is evident...
Conference Paper
With an objective to improve the convergence characteristics of nonlinear active noise control (ANC) systems, this paper proposes a discrete cosine transform based adaptive algorithm for ANC. The performance of the new algorithm in terms of speed of convergence has been compared with that of the filtered-s least mean square algorithm. The improved...
Conference Paper
A new approach towards time frequency localization has been proposed in this paper. This scheme is based on a local variance factor. The framework of the approach has been demonstrated mathematically. The consistency of approach and the resulting methodology have been empirically verified.
Conference Paper
High computational load involved in nonlinear adaptive controllers acts as a bottleneck in the deployment of large multichannel active noise control systems. In order to circumvent this limitation, this paper proposes a computationally efficient multichannel nonlinear active noise control scheme based on the principle of partial updates. Simulation...
Article
This paper discusses the evolution of active noise control systems over the past 75 years. The focus of this study is on the use of signal processing and some recent soft computing tools on the development of active noise control systems. Special attention has been paid to the advances in nonlinear active noise control achieved during the past deca...
Article
A novel nonlinear adaptive filter based on a cascade combination of a functional link artificial neural network (FLANN) and a Legendre polynomial has been proposed in this paper for nonlinear active noise control (ANC). The performance of the new controller has been compared with that obtained by a FLANN based ANC system trained using a filtered-s...
Article
This paper proposes a functional-link-artificial-neural-network-based (FLANN) multichannel nonlinear active noise control (ANC) system trained using a particle swarm optimization (PSO) algorithm suitable for nonlinear noise processes. The use of PSO algorithm in a multichannel ANC environment not only reduces the local minima problem but also remov...
Article
Over the years, a number of different models and techniques have been proposed to both quantify and explain the glacial isostatic adjustment (GIA) process. There are serious challenges, however, to obtaining accurate results from measurements, due to noise in the data and the long periods of time necessary to identify the relatively small-magnitude...
Article
The performance of a nonlinear active noise control (ANC) system based on the recently developed filtered-s least mean square (FsLMS) algorithm deteriorates when strong disturbances in the ANC system are acquired by the microphones. To surmount this shortcoming, a novel robust FsLMS (RFsLMS) algorithm is proposed for a functional link artificial ne...
Article
The conventional filtered-x least mean square (FxLMS) algorithm commonly employed for active noise control (ANC) is sensitive to disturbances acquired by the error microphone and yields poor performance in such scenario. To circumvent this problem, in this paper, a Wilcoxon FxLMS (WFxLMS) algorithm is proposed and used in the design of an efficient...
Article
The presence of nonlinearities as well as acoustic feedback deteriorates the cancellation performance of the conventional filtered-x LMS (FxLMS) algorithm based active noise control (ANC) systems. With an objective to improve the performance, a novel filtered-su LMS (FsuLMS) algorithm based ANC system which employs a convex combination of an adapti...
Conference Paper
This paper proposes a novel low complexity nonlinear active noise control (ANC) system. The nonlinear controller is composed of an adaptive Legendre neural network (LeNN), updated using a filtered-l least mean square (FlLMS) algorithm. The computational complexity of the proposed scheme has been further reduced by incorporating the principle of par...
Article
A nonlinear active noise control (ANC) system based on a couple of low complexity nonlinear networks are developed in this paper. These are the evolutionary computing based feed forward nonlinear network (FFNN) and the evolutionary computing based feed forward recursive nonlinear network (FFRNN). The new method does not require the identification o...
Conference Paper
Full-text available
A noisy time series, with both signal and noise varying in frequency and in time, presents special challenges for improving the signal to noise ratio. A modified S-transform time-frequency representation is used to filter a synthetic time series in a two step filtering process. The filter method appears robust within a wide range of background nois...
Conference Paper
Full-text available
The time-frequency representation (TFR) has been used as a powerful technique to identify, measure and process the time varying nature of signals. In the recent past S-transform gained a lot of interest in time-frequency localization due to its superiority over all the existing identical methods. It produces the progressive resolution of the wavele...