New Publications are available for Interpolation and function approximation (numerical analysis)
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New Publications are available now online for this publication.
Please follow the links to view the publication.Modeling study of the amount of wear in sliding electric contact
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0638
The wear produced from the sliding contact in the pantograph slide and contact line system, has a direct relationship with the contact load. In premise of the current carrying performance conditions, there will be erosion resistance wear when the load is smaller, but mechanism wear when the load is bigger. In this article, many experiments through the leaching copper carbon sliding plate and Silver copper wire were conducted to study the wear characteristics of the sliding electrical contact in different load flow, speed and the changes of load. And some variables are fixed, then the others will be changed to find the variety of wear, also the data have been saved. After analyzing the relationship of different conditions, a model including the wear and the contact load will be produced, then draw the function equation include speed and others variables. The coefficient of which will be devised based on the saved data using the least-square method. And some experimentations are taken to validate the model, which could adequately reflect the function relationship between the wear and contact load. Also this model will be given a theory basis on the best load designing.Interpolation of magnetic and electric fields using spherical elementary current systems
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0396
A physics-based technique for interpolating magnetic and electric field disturbances of external origin across large spatial areas can be achieved by employing the Spherical Elementary Current System (SECS) method using data from ground-based magnetic observatories. The SECS method represents complex electrical current systems as a simple set of equivalent currents placed at a specific height in the ionosphere. The magnetic field recorded at observatories can be used to invert for the electrical currents and subsequently employed to interpolate or extrapolate the electric and magnetic field across a large area at midto high geomagnetic latitudes. Here we show that the magnetic field interpolation can be improved, even over very large distances (> 1000 km), by the addition of further observatory data into the SECS inversion. (5 pages)Application of distance bounding protocols with random challenges over RFID noisy communication systems
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0607
Distance bounding protocols are proposed based upon the round trip time measurements of the executed messages to protect RFID systems against the relay attack. The existing distance bounding protocols employed by RFID systems are divided into two categories generally called, with random challenges or with mixed challenges. Since RFID systems and distance bounding protocols are particularly susceptible to noise, in this paper, the security analysis of distance bounding protocols with random challenges is performed over a noisy channel. This analysis is achieved by computing an attacker's success probability due to mafia fraud and distance fraud attacks in a noisy environment. In this case, the analysis as well as simulation results show that increasing the number of iterations (rounds) makes the attacker's success probability to decrease and adversely it can causes the rejection probability of a valid tag due to channel errors to increase. Therefore, the proper values for the number of iterations and the total number of errors that are acceptable are computed to obtain the optimal false-accept and false-reject probabilities in a noisy environment. (5 pages)Multi-frame super resolution using edge directed interpolation and complex wavelet transform
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0447
In this paper, a multi frame super resolution technique is proposed which uses edge directional interpolation (EDI) and dual-tree complex wavelet transform (DT-CWT). In the proposed technique a super resolution process is applied for each frame to generate the low frequency component. On the other hand, high frequency components are generated by DTCWT decomposition followed by EDI. Finally, the composition of the generated subbands using inverse DTCWT (IDT-CWT) reconstructs the super resolved output frame. Experimental results on a number of benchmark video sequences with respect to their PSNR measures confirm the superiority of the suggested method over the state of the art video resolution enhancement methods. (5 pages)Novel fingerprint segmentation with entropy-Li MCET using log-normal distribution
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0455
Fingerprint recognition is an important biometric application. This process consists of several phases including fingerprint segmentation. This paper proposes a new method for fingerprint segmentation using a modified Iterative Minimum Cross Entropy Thresholding (MCET) method. The main idea is to model fingerprint images as a mixture of two Log-normal distributions. The proposed method was applied on bi-modal fingerprint images and promising experimental results were obtained. Evaluation of the resulting segmented fingerprint images shows that the proposed method yields better estimation of the optimal threshold than does the same MCET method with Gamma and Gaussian distributions. (6 pages)A Bayesian look at the optimal track labelling problem
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0406
In multi-target tracking (MTT), the problem of assigning labels to tracks (track labelling) is vastly covered in literature, but its exact mathematical formulation, in terms of Bayesian statistics, has not been yet looked at in detail. Doing so, however, may help us to understand how Bayes-optimal track labelling should be performed or numerically approximated. Moreover, it can help us to better understand and tackle some practical difficulties associated with the MTT problem, in particular the so-called “mixed labelling” phenomenon that has been observed in MTT algorithms. In this paper, we rigorously formulate the optimal track labelling problem using Finite Set Statistics (FISST), and look in detail at the mixed labeling phenomenon. As practical contributions of the paper, we derive a new track extraction formulation with some nice properties and a statistic associated with track labelling with clear physical meaning. Additionally, we show how to calculate this statistic for two well-known MTT algorithms. (6 pages)A combined image approach to compression of volumetric data using delaunay tetrahedralization
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0461
We present a method for lossy compression of three dimensional gray scale images that is based on a 3D linear spline approximation to the image. We have extended an approach that has previously been successfully applied in two dimensions. In our method, we first select significant points in the data, and use them to create a 3D tetrahedralization. The tetrahedrons of the tetrahedralization are used as cells for a linear interpolation spline that gives an approximation of the original image. The compression is done by storing the positions of the vertices of the tetrahedralization and the values there instead of the value of the approximation at each grid point. We introduce a novel concept of using a smoothed version of the original image to improve the quality of the approximating spline. To increase the efficiency of the algorithm, we combine it with a refinement/decimation technique. We compare our compression technique to JPG2000 3D. We show that our algorithm performs similarly to, and in some cases even outperforms it, for high compression ratios. Our approach gives images that have significantly different properties than ones created using wavelets, and have the potential of being more suitable for some applications. In addition, this type of compression is particularly suitable for visualization. (6 pages)Face recognition using kernel collaborative representation and multiscale local binary patterns
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0457
Collaborative Representation with regularized least square (CRC-RLS) is state-of-the-art face recognition method that exploits the role of collaboration between classes in representing the query sample. However, this method views the image as a point in a feature space, and the performance can be degraded when the cropped face image is misaligned and/or the lighting conditions change. Histogram-based features, such as Local Binary Patterns (LBP) have gained reputation as powerful and attractive texture descriptors showing excellent results in terms of accuracy in face recognition. In this paper, LBP features are introduced in CRC-RLS to confront these problems such as illumination. In addition, motivated by the recent success of non-linear approaches, a new kernel-based nonlinear regularized least square classifier with collaborative representation (KCRC-RLS) is proposed in this paper. The proposed system is evaluated on two benchmarks: ORL and Extended Yale B. The results indicate a significant increase in the performance when compared with state-of-the-art face recognition methods. (4 pages)An application of sequential Monte Carlo samplers: an alternative to particle filters for non-linear non-gaussian sequential inference with zero process noise
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0413
Particle filters are not applicable in sequential parameter estimation scenarios, ie scenarios involving zero process noise. Sequential Monte Carlo (SMC) samplers provide an alternative sequential Monte-carlo approximation to particle filters that can address this issue. This paper aims to provide a description of SMC samplers that is accessible to an engineering audience and illustrate the utility of SMC samplers through their application to a specific problem. The problem involves processing a stream of bearings-only measurements to perform localisation of a stationary tar get. The SMC sampler solution is shown to outperform an Extended and Unscented Kalman filter in nonlinear scenarios (as defined by a novel metric for nonlinearity that this paper describes). The SMC sampler offers a computational cost that is near-constant over time on average. Future work aims to investigate the utility of Approximate Bayesian Computation and apply the technique within a Simultaneous Localisation and Mapping context. (8 pages)Particle learning methods for state and parameter estimation
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0412
This paper presents an approach for online parameter estimation within particle filters. Current research has mainly been focused towards the estimation of static parameters. However, in scenarios of target maneuver-ability, it is often necessary to update the parameters of the model to meet the changing conditions of the target. The novel aspect of the proposed approach lies in the estimation of non-static parameters which change at some unknown point in time. Our parameter estimation is updated using change point analysis, where a change point is identified when a significant change occurs in the observations of the system, such as changes in direction or velocity. (6 pages)Bayes optimal knowledge exploitation for target tracking with hard constraints
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0411
Nonlinear target tracking is a well known problem and its Bayes optimal solution, based on particle filtering techniques, is nowadays applied in high performance surveillance systems. Oftentimes, additional information about the environment and the target is available, and can be formalized in terms of constraints on target dynamics. Hence, a Constrained version of the Bayesian Filtering problem has to be solved to achieve optimal tracking performance. In this paper we consider the Constrained Filtering problem for the case of perfectly known hard constraints. We clarify that in such a case the Particle Filter (PF) is still Bayes optimal if we can correctly model the constraints. We then show that from a Bayesian viewpoint, exploitation of the available knowledge in the prediction or in the update step are equivalent. Finally, we consider simple techniques to exploit constraints in the prediction and update steps of a PF, and use the Kullback-Leibler divergence to illustrate their equivalence through simulations. (6 pages)Understanding S-parameter vs. equivalent circuit-based models for surface mount RLC devices (Abstract only)
http://dl-live.theiet.org/content/conferences/10.1049/ic.2012.0060
Summary form only given. For many years, S-parameter data files have been the default industry standard for representing passive surface mount devices in the microwave industry. In many cases, however, S-parameters fall short in terms of equipping designers with the simulation capability that is needed for circuit design success. In contrast, a properly extracted equivalent circuit model can avoid many inherent limitations of data file representations and provide for extrapolation, scaling, and statistical yield analyses not easily accomplished with S-parameters alone. This talk will discuss “best-practice” surface-mount component modeling from a number of points of view. Several examples will be presented to illustrate common problems and solutions that can be accomplished using a combination of modern tools. These tools include on-board RF probing, electromagnetic analysis and complex equivalent circuit modeling. Resulting models enable simulations that can very accurately represent microwave as well as mm-wave passive surface mount devices in ways that enable reliably successful circuit design flows from synthesis, through optimization and yield analysis to measured results that correlate well with simulation predictions.Decoupled steady-state model of the modular multilevel converter with half-bridge cells
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0232
Modular multilevel converters, based on cascading of half-bridge converter cells, can combine low switching frequency with low harmonic interference. They can be designed for high operating voltages without direct series connection of semiconductor elements. This has led to a rapid adoption within high-power applications such as HVDC, STATCOM and railway interties. Analysing the operation of these converters in the frequency domain poses a few challenges due to the presence of significant low-order harmonic voltages in the cell capacitors. This paper presents a frequency-domain model of the MMC converter with half- bridge cells, based on a two-stage approach. First, the circuit equations are decoupled by a simple linear transformation, whereby the circuit schematic can be separated into a dc-side and an ac-side part. Second, the switching operation within the phase arms is modelled in the frequency domain by iterated convolution. The model is verified against a time- domain simulation of a converter with ratings valid for HVDC applications. It is shown that the proposed methodology, where all calculations are made in the frequency domain, can accurately reproduce the results from the simulation. (6 pages)Online optimized stator flux reference approximation for maximum torque per ampere operation of interior permanent magnet machine drive under direct torque control
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0266
This paper presents an online optimized stator flux reference approximation scheme for application of direct torque control (DTC) technique to interior permanent magnet (IPM) brushless AC (BLAC) drives with maximum torque per ampere (MTPA) operation. It is found that by considering dq-axis stator flux components instead of stator flux magnitude, straightforward mathematical functions for computing stator flux reference from the relevant torque reference to achieve MTPA operation can be derived. It is also demonstrated that by properly selecting initial value for approximating the proposed stator flux equation utilizing the Newton-Raphson method, a high degree of accuracy can be obtained utilizing only one computing step. It is shown that MTPA operation can be achieved for a DTC-based IPM BLAC drive using the proposed stator flux reference approximation scheme. Simulation results confirm validity of the proposed method. (6 pages)Implementation of time-varying observers used in direct field orientation of motor drives by trapezoidal integration
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0162
The paper discusses the problem of implementing the state observers associated with direct field orientation (DFO) of motor drives using trapezoidal integration (Tustin method). Typically, the discrete-time equations of observers are obtained by emulating the continuous-time equations using the Euler method (forward rectangular rule). With Euler integration, the resulting equations are simple and the real-time implementation requires low computational effort. However, Euler-based observers become inaccurate if a small sampling time cannot used or if the motor drive operates at high frequency-this is because, as the sampling time increases, the Euler approximation of the integral starts losing more and more area from under the curve. The Tustin method (trapezoidal integration) offers an interesting alternative it is theoretically a more accurate integration method, however, it is more complicated. The paper discusses the emulation procedure required to discretize continuous-time observers based on trapezoidal integration. The permanent magnet synchronous motor (PMSM) is used as an example of a time-varying plant-the paper develops a trapezoidal integration based observer for the PMSM and compares this with an Euler-based observer in terms of computational complexity and performance. The two observers are simulated comparatively in order to establish the conditions when trapezoidal integration outperforms the Euler method. (6 pages)Discrete time integration of observers with continuous feedback based on Tustin's method with variable prewarping
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0161
The paper discusses the problem of integrating the equations of state observers associated with direct field orientation (DFO) of motor drives and presents a method to improve the integration accuracy when the drive operates at high frequency. In a typical implementation, observer equations are integrated based on the Euler method (forward rectangular rule). Euler method is simple; however, integration is accurate only at low/medium speed. As the speed (frequency) increases, the integration process becomes more and more inaccurate because the rectangular approximation starts losing more and more area from under the curve. Theoretically, the problem could be alleviated by increasing the sampling frequency; however, this cannot always be done because it has implications related to the switching frequency of the power converter. Another idea is to use a more accurate integration method, for example, trapezoidal integration (Tustin method). At high frequency, trapezoidal integration performs better than the Euler method and the resulting estimates are closer to the expected values (in both magnitude and phase). In DFO drives, this leads to a more accurate field orientation angle. The paper presents an improvement to trapezoidal integration - the state equations of observers are integrated using a discrete-time filter that is prewarped as a function of the drive's operating frequency. The algorithm estimates the applied frequency, prewarps the continuous-time transfer function used in practical integration and obtains a discrete time filter with frequency dependent coefficients. It is shown that the method produces an improvement over trapezoidal integration in the high-speed region. The implications related to DFO are studied by considering a full-order observer for the PMSM - integration with prewarping is compared with the classic Tustin method. The theoretical development is supported with simulation results. (6 pages)Optimal allocation of distributed generation to minimize relay operating times
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0086
Integrating Distributed Generation (DG) in distribution systems will have an impact on the fault current magnitudes. This could have an impact on the coordination of the protective devices. In this paper, the optimal DG locations are determined in order to minimize the overall relay operating times for a meshed distribution system. The problem is formulated as a Non-Linear Programming (NLP) problem and is solved using the reduced gradient approach. The relay operating times are minimized taking into account the protection coordination constraints where each relay is backed up by another relay on the system with a certain coordination time. In addition, constraints on the relay operating times and relay settings are included. The system under study is the IEEE meshed 30 bus distribution system with a protection system that relies on directional over-current relays. (5 pages)The design of AC permanent magnet motors for electric vehicles: a computationally efficient model of the operational envelope
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0251
Salient brushless AC (BLAC) permanent magnet (PM) motors are a preferred topology in the rapidly growing area of electric vehicle traction due to their inherent high efficiencies and excellent power densities. In the design of these systems it is important to appraise the motor performance across the entire torque-speed envelope. This paper presents computationally efficient techniques that allow rapid and accurate modelling of the entire operational envelope of any BLAC PM motor, enabling the generation of torque/speed characteristics and loss maps that can be used in an iterative design process. The proposed techniques are validated against test data from an in-house 35kW interior PM motor design and a comparison between a measured and computed efficiency map for the 2004 Toyota Prius motor is undertaken. (6 pages)Accurate estimation of electric vehicle speed using Kalman filtering in the presence of parameter variations
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0315
The mechanical drivetrain dynamics of electric vehicles can have a detrimental effect on the performance of the vehicle speed controller. This is mainly caused by the feedback only being available from the motor encoder, with no measurement of the actual vehicle speed. In this paper it is shown how the vehicle driveability can be greatly improved if estimates of vehicle speed and mass are obtained. This has been realised using a Kalman Filter (KF) and a Recursive Least Squares (RLS) estimator, and validated with experimental results. (6 pages)Modelling and simulation of a quad-rotor helicopter
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0318
Small size quad-rotor helicopters are often used due to the simplicity of their construction and maintenance, their ability to hover and also to take-off and land vertically. The first step in control development is an adequate dynamic system modelling, which should involve a faithful mathematical representation of the mechanical system. This paper presents a detailed dynamic analytical model of the quad-rotor helicopter using the linear Taylor series approximation method. The developed analytical model was simulated in the MatLab/Simulink environment and the dynamic behaviour of the quad-rotor assessed due to voltage changes. The model is further calibrated and linearized for use on any quad-rotor helicopter. (6 pages)Examination of new current control methods for modern PMW controlled AC electric locomotives
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0314
A railway electrification system supplies electrical energy to railway locomotives and multiple units. There are several different electrification systems in use throughout the world. The single-phase AC network systems are widespread (25 kV 50 Hz or 15 kV 16 2/3 Hz). The Hungarian system is 25 kV 50 Hz AC. This article is just dealing with the AC network supplied locomotives. Nowadays in our country the series wound DC traction motor driven locomotives are still widely used. These vehicles are equipped with diode or thyristor rectifier circuits that inject harmonics into the AC line and distort the line voltage. In our work we examined and compared current control methods that can be achieved by "network-friendly" locomotives connected to distorted line. We worked out a new current control strategy that possesses several advantages. The modern locomotives endeavour to consume sinusoidal current from the AC network, in phase with the network voltage fundamental. In generator mode these endeavour to supply back to the grid sinusoidal current in antiphase to the voltage fundamental. We compared current control methods with this "common" strategy. One of them can reduce the consumed root mean square (RMS) or fundamental current of a distorted line connected modern locomotive in motor mode. Other one can increase the generated RMS and fundamental current in generator mode. With these strategies the harmonic currents can be used for active power. Moreover it turned out that the harmonic content of the network can be reduced by the "new" strategies. For the study, we built a test system. We can model the line side converter of a modern locomotive DC-link frequency converter with the system. A common solution in locomotives is when several line-side converters feed two DC-links. In the test system we modelled these with one converter, while the motor-side voltage source inverters and the electric traction motors were taken into account as a controllable current source DC-link. (5 pages)Adaptive second-order TDTL with optimized performance
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0152
In this paper the architecture of a second-order time delay digital tanlock loop (TDTL) with real-time adaptive calculation of the loop filter coefficients is proposed. An adaptive digital filter based on the recursive least squares (RLS) algorithm is used to generate the coefficients of the TDTL loop filter. This allows the filter coefficients to be continuously updated in real- time so as to optimise the noise immunity of the TDTL in a highly dynamic environment. The performance of the proposed system was evaluated and compared with the original TDTL system using both additive white Gaussian noise (AWGN) and Doppler shifts. The results indicate that the noise performance of the proposed system outperforms that of the original TDTL. (5 pages)Adaptive decision feedback detection with constellation constraints for multi-antenna systems
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0150
A low-complexity decision feedback (DF) detection algorithm with constellation constraints (DFCC) is proposed for multiple-antenna systems. An enhanced detection and interference cancellation is achieved by introducing the constellation constraints (CC). For time-varying channels, the proposed receiver updates the filter weights using recursive least squares (RLS) algorithm. This highly efficient detector is also incorporated in a multiple branch (MB) structure to achieve a higher detection diversity order. Simulations show that the proposed DFCC technique has a complexity as low as the conventional adaptive DF detector while it achieves a significant performance improvement. (5 pages)Widely linear complex extended Kalman filters
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0156
Complex signals are generally second order noncircular (improper), that is, their probability distributions are rotation dependent, and conventional algorithms that assume second order circular distributions are generally inadequate. Recently the widely linear (augmented) complex extended Kalman filter (ACEKF), which utilises augmented complex statistics, has been proposed for dealing with the generality of complex signals, both second order circular and noncircular. In this paper, we analyse the ACEKF and show that it has an equivalent (dual) real valued extended Kalman filter, and that this duality can be used to reduce its computational complexity. We also provide a mean square analysis of the linear conventional complex Kalman filter (CCKF) and the augmented complex Kalman filter (ACKF), and show that the ACKF has superior performance for second order noncircular signals. Simulations using both synthetic and real world proper and improper signals support the analysis. (5 pages)Multispeaker direction of arrival tracking for multimodal source separation of moving sources
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0143
An improvement is proposed in the audio-visual approach to solve the problem of source separation of physically moving speakers by exploiting multiple video cameras, a circular microphone array and robust spatial beamforming. The challenge of separating moving sources is that the mixing filters are time varying; as such the unmixing filters should also be time varying but these are difficult to determine from only audio measurements. Therefore the visual modality is utilized to track the direction of each speaker to the microphone array by using a Markov chain Monte Carlo particle filter (MCMC-PF). The proposed direction of arrival (DOA) tracker improves the computational complexity with respect to a previously employed 3-D multi-speaker position tracker. The DOA information is used in a robust least squares frequency invariant data independent (RLSFIDI) beamformer to separate the audio sources. Experimental results show that the proposed technique efficiently tracks the DOA with improved computational complexity and enhanced source separation. (5 pages)Audio classification based on sparse coefficients
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0153
Audio signal classification is usually done using conventional signal features such as mel-frequency cepstrum coefficients (MFCC), line spectral frequencies (LSF), and short time energy (STM). Learned dictionaries have been shown to have promising capability for creating sparse representation of a signal and hence have a potential to be used for the extraction of signal features. In this paper, we consider to use sparse features for audio classification from music and speech data. We use the K-SVD algorithm to learn separate dictionaries for the speech and music signals to represent their respective subspaces and use them to extract sparse features for each class of signals using Orthogonal Matching Pursuit (OMP). Based on these sparse features, Support Vector Machines (SVM) are used for speech and music classification. The same signals were also classified using SVM based on the conventional MFCC coefficients and the classification results were compared to those of sparse coefficients. It was found that at lower signal to noise ratio (SNR), sparse coefficients give far better signal classification results as compared to the MFCC based classification. (5 pages)Iterative QR decomposition-based detection algorithms with multiple feedback and dynamic tree search for LDPC-coded MIMO systems
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0170
In this paper, we present two innovative LDPC- coded QR decomposition-based soft-output detection techniques, both of which are able to achieve a near-ML performance with significant reduced complexity compare to other optimal detection solutions, such as MAP or list SD algorithms. The first detector (MF-QRD) employs a multi-feedback technique to select appropriate candidates when the symbols are unreliable. Another detection strategy called variable-M QRD (VM-QRD) detector is developed which dynamically adapts the number of detection candidates according to the channel variations in each detection layer. The irregular PEG LDPC code is employed as the outer channel code which provides efficient redundancy for mitigating remaining co-channel interference and additive noise. And simulation results show that the proposed algorithms have excellent performances. (5 pages)A switched-order FLOM STAP algorithm in heterogeneous clutter environment
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0160
The normalized fractionally-lower order moment (NFLOM) algorithm exhibits fast convergence but low steady- state signal-to-interference-plus noise ratio (SINR) when the order is less than two. In this paper, we propose a switched-order NFLOM algorithm to adaptively select the best order to achieve both fast convergence and good steady-state performance. The basic idea is to constrain the order within a range of appropriate values, to compute the space-time adaptive processing (STAP) the best order that maximizes the output SINR. The proposed algorithm is assessed with simulated data considering a heterogeneous clutter environment. The simulation results illustrate that our proposed algorithm outperforms the normalized least mean squares (NLMS) algorithm and the NFLOM algorithm, and has an easier parameter setting than the existing variable-order algorithms. (5 pages)Wiener system identification using B-spline functions with De Boor recursion
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0138
A simple and effective algorithm is introduced for the system identification of Wiener system based on the observational input/output data. The B-spline neural network is used to approximate the nonlinear static function in the Wiener system. We incorporate the Gauss-Newton algorithm with De Boor algorithm (both curve and the first order derivatives) for the parameter estimation of the Wiener model, together with the use of a parameter initialization scheme. The efficacy of the proposed approach is demonstrated using an illustrative example. (5 pages)Compressive sensing reconstruction techniques with magnitude prior information
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0151
This paper considers compressive sensing (CS) reconstruction with magnitude prior information. The magnitude prior information is described by mean and covariance of the unknown signal. Towards a reconstruction with minimum mean square errors (MMSE), we propose several CS reconstruction algorithms that use the magnitude prior information. Numerical simulations demonstrate that our approach reduces the reconstruction distortion. Potential applications of the proposed techniques include radio spectrum surveillance, sensor networks, etc. (5 pages)Joint receiver design and power allocation strategies for wireless sensor networks
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0140
In this paper, we consider a 2-hop wireless sensor network (WSN) with multiple relay nodes where the amplify- and-forward (AF) scheme is employed. Our strategy is to jointly design the linear receiver and the power allocation parameter via an alternating optimization approach subject to global, individual and neighbour-based power constraints respectively. We derive constrained minimum mean-square error (MMSE) expressions for the linear receiver and the power allocation parameter that contains the optimal complex amplification coefficients for each relay nodes. Computer simulations show good performance of our proposed methods in terms of bit error rate (BER) compared with the method with equal power allocation. Furthermore, the method with neighbour-based constraint brings a feature to balance the performance against the computational complexity and the need for feedback information which is desirable for WSNs to extend their lifetime. (5 pages)Sparsity-aware STAP algorithms for airborne radar based on conjugate gradient techniques
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0142
In this paper, new sparsity-aware space-time adaptive processing (STAP) algorithms based on conjugate gradient (CG) techniques are proposed. The idea of sparsity-aware STAP algorithms is based on the incorporation of a sparse regularization (l<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">1</sub>-norm) constraint to the minimum variance (MV) design criterion. To solve this optimization problem, two different l<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">1</sub>-based algorithms based on the conventional CG and the modified CG are derived. An analysis of the computational complexity shows that the proposed algorithms have nearly the same cost as the conventional algorithms. It is also demonstrated that the proposed STAP algorithms outperform the conventional algorithms using the simulated airborne radar data. (5 pages)Using acoustic images for human identification
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0161
An acoustic electronic scanning array is developed to acquire acoustic images from a person. On the basis of pulse- echo techniques, multifrequency acoustic images are obtained for a set of positions of a person (front, front with arms outstretched, back and side). Two uniform linear arrays with 15 λ/2-equispaced sensors have been employed, using different spatial apertures in order to reduce sidelobe levels. Work frequencies have been designed on the basis of the main lobe width, the grating lobe levels and the frequency responses of people and of sensors. Finally, for a case of study with 6 people, the acoustic profiles, formed by all images acquired, are evaluated and compared in a mean square error sense. According to the obtained results, this system will be able to be used for biometric applications. (5 pages)Validation of load-independent X-parameters<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">®</sup> formulation for use in analytical circuit design
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0212
Recently analytical behavioral model formulation based on the PHD model has been introduced and successfully used to describe the nonlinear behavior of transistors and components [1-3]. The next important advance would be to utilize this formulation, constraint to load-independent X parameters, to enable analytical non-linear microwave circuit design procedures. For this purpose, in this paper a blind iterative process is presented and validated in order to obtain the appropriate load independent X parameters, focused around the chosen optimum impedance condition, necessary to enable accurate analytical non-linear circuit design to be undertaken.CT-based robust statistical shape modeling for forensic craniofacial reconstruction
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0126
Estimating the facial outlook from an unidentified skull is a challenging task in forensic investigations. This paper presents the definition and implementation of a craniofacial model for computerized craniofacial reconstruction (CFR). The craniofacial model consists of a craniofacial template that is warped towards an unidentified target skull. The allowed transformations for this warping are statistically defined using a PCA-based transformation model, resulting in a linear combination of major modes of deformations. This work builds on previous work [1] in which a statistical model was constructed based on facial shape (represented as a dense set of points) variations and sparse soft tissue depths at 52 craniofacial landmarks. The main contribution of this work is the extension of the soft tissue depth measurements to a dense set of points derived from a database of head CT-images of 156 patients. Despite the limited amount of training data compared to the number of degrees of freedom, the reconstruction tests show good results for a larger part of the test data. Root mean squared error (RMSE) values between reconstruction results and ground truth data smaller than 4 mm over the total head and neck region are observed. (6 pages)Eigen values and vectors computations on VIRTEX-5 FPGA platform cyclic Jacobi's algorithm using systolic array architecture
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0044
The parallel iterative algorithms are the major advancements in the field of computing. These algorithms lead to efficient usage of hardware as well as obtaining faster results. In this paper, we describe architecture to compute eigen values and eigen vectors of a matrix having dimensions up to 50 × 50 using cyclic Jacobi's Algorithm. Systolic array architecture is used to apply it to matrices of larger dimensions. We have implemented the architecture on FPGA Vertex-5 that takes about 8059 LUT slices out of 69120 slices for matrices of dimensions 50 × 50.Self-dependent 3D face rotational alignment using the nose region
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0101
One of the challenging issues for 3D face recognition is face alignment. Many alignment algorithms are computationally expensive, making them unsuitable for real-time biometrics, or not robust enough to detect large variations in pose. In this work, a novel algorithm for 3D face rotational alignment is proposed, that uses the nose region. After preprocessing and nose region identification, alignment is performed by applying two energy functions to the nose footprint, identified as the largest filled region in the inverted depth map. These functions are minimised using Simulated Annealing and the Levenberg-Marqurdt algorithm. The energy minimisation and segmentation procedures continue iteratively until a stopping criterion is met. The method has been applied to images from the Face Recognition Grand Challenge (FRGC) v2 dataset and the consistency of its alignment has been verified using the iterative closest point (ICP) algorithm. As a self-dependent algorithm, it does not require a pre-aligned image as a reference and also has a high computational speed, approximately three times faster than the brute force ICP technique. (6 pages)Clustering performance analysis of FCM algorithm on iterative relaxed median filtered medical images
http://dl-live.theiet.org/content/conferences/10.1049/ic.2011.0069
Noise removal is a major concern in image processing particularly in medical imaging. In this paper, a novel noise removal technique called Iterative relaxed median filter (IRMF) has been proposed and the effect of noise removal, by means of median filtering, on Fuzzy C-Means Clustering (FCM) has been analysed. Noise removal is carried out by various median filtering methods such as standard median filter (SMF), adaptive median filter (AMF), hybrid median filter (HMF) & relaxed median filter (RMF) and the performance of these methods is compared with the proposed method.A combined interpolation method for waveform reconstruction in beacon transmitter detector
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0889
When beacon transmitter detector making measurements on high speed beacon signal, interpolation is required to reconstruct waveform from sampled waveform data for optimal waveform viewing. In this paper, the linear interpolation and sine interpolation are introduced and analyzed firstly. Then utilizing the characteristics of beacon transmitter detector, a combined interpolation method which consists of the linear interpolation and sine interpolation is proposed. Simulation results show that the proposed combined method has good waveform reconstruction performance and relatively low computational complexity. It is very suitable for implementation of waveform reconstruction in beacon transmitter detector.Review of eddy current analysis
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0002
Summary form only given. The quasi-static magnetic approximation of Maxwell's equations neglecting the displacement current density leads to eddy current problems. The analysis of eddy current problems a challenging task requiring separate treatment of the two types of regions.Analysis and comparison of GNSS code tracking with different discriminators
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0838
Code tracking is an indispensible operation of a Global Navigation Satellite System (GNSS) receiver. This paper provides analytical expressions for tracking loop performances using quasi-coherent dot product discriminator under small error conditions. Expressions are derived for root mean squared tracking error for arbitrary Signal-in-Space (SIS) spectra, Gaussian noise and non-white interference. Theoretical expressions are compared with previous work and numerical results are provided to examine the effect of different discriminators, SIS modulation designs and types of interference.Linear interference alignment based on signal and interference space ranks
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0982
In this paper, we discuss the implementation problem of interference alignment with low complexity. Firstly, interference system model based on signal and interference space is analyzed. Then, the design of chordal distance based linear precoder and receiver filter based on the optimization problem of rank of interference space are presented. Simulation results confirm that the sum rate of linear interference alignment is close to the iterative alignment scheme, but the computation complexity can be reduced greatly.Eigen-based dictionary for ultra-wideband compressed sensing
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0851
In practice, sub-Nyquist rate sampling schemes are desirable in ultra-wideband (UWB) applications. Due to the fact that UWB signals are sparse in nature, compressed sensing (CS) is regarded as a promising technology which enables low rate sampling of UWB signals. In CS, a crucial issue is to find the best dictionary which statistically achieves the sparsest representation of the target signals. This is because that the number of measurements (sampling rate) required by CS to reconstruct the original signals is proportional to the sparseness. In this paper, we propose an eigen-based dictionary for CS-based UWB channel estimation and signal detection, where the eigenvectors of the covariance matrix of the UWB channel are used as the elements of the dictionary. For ease of implementation, the generalized rotation matrix, instead of the Gaussian random matrix, is employed as measurement matrix and orthogonal matching pursuit (OMP) algorithm is employed to reconstruct original UWB signals. Simulation results over realistic channels show that the proposed dictionary outperforms conventional dictionaries.SER analysis of physical layer network coding at high SNR over AWGN channels
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.1019
Physical layer network coding (PNC), where relay node is allowed to process the superimposed signal directly, can improve the network throughput and spectral efficiency greatly. In this paper, we extent nearest neighbor approximation to investigate the symbol error rate (SER) of PNC over AWGN channels. SER for BPSK and QPSK modulation is derived, and an algorithm is designed to calculate the SER for high order modulations. Simulation results validate the derived SER expressions can characterize the SER performance of PNC over AWGN channels.Effective channel estimation for sparse multipath OFDM systems
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0628
Coherent detection and demodulation need channel state information at receivers for orthogonal frequency division multiplexing systems. Conventional channel estimations, such as least squares (LS), are widely adopted under the assumption of rich multipath. Recently, numerous physical measurements have verified that many wireless multipath channels encountered in practice tend to exhibit sparse structures. Exploiting the inherent sparsity, a novel channel estimation method based on compressive sensing is proposed, which reduces the number of pilots so as to improve the bandwidth efficiency. Simulation results confirm that the proposed method has a 5-dB lower mean square error in channel estimation when compared to the conventional approach. In addition, the complexity of the proposed method is acceptable.Analysis of time invariant state equation using blend function
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0447
"The Blend Function" is a combination of Sample-and-Hold (SHF) function set and Right Hand Side Triangular Function (RHTF) set. It is a new set of Piece-wise Constant Basis Function (PCBF). Any square integrable function can be approximated in this domain. Here, the blend function set is used to find response of a linear time invariant system described by a linear state equation and the result is compared with block pulse function domain analysis (the most fundamental component of PCBF family).Lattice-reduction-aided tomlinson Harashima precoding based on MMSE criteria in multiuser MIMO downlink system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0638
In this paper, two kinds of lattice-reduction-aided (LRA) Tomlinson-Harashima precoding (THP) will be proposed. THP is a nonlinear precoding technique which uses modulo operation and successive interference cancellation (SIC). Lattice reduction methods have been proved to be powerful tools in solving the closest lattice point search problem. The lattice reduction methods which implement to the THP can improve the performance obviously. The LLL algorithm is a common used method for the lattice reduction, and the lattice reduction that based on LLL algorithm can transform the channel matrix into a more orthogonal one. Simulation results show the proposed schemes significantly outperform the traditional MMSE based THP.An iterative multiuser detection with frequency-domain equalization for relay-assisted SFBC single-carrier systems
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0630
In this paper, an iterative multiuser detection scheme for relay-assisted space-frequency block code (SFBC) single-carrier systems with frequency-domain equalization is proposed. In practical mobile applications, relay-assisted SFBC in SC-FDE suffers performance degradation from double-selective (time and frequency selective) channels, resulting in a deviation from the basic assumption of Alamouti codeword. In the proposed algorithm, diagonalized SFBC decoding, soft multi-user interference (MUI) cancellation and soft inter-symbol interference (ISI) cancellation with minimum mean-square error (MMSE) filtering were performed iteratively to suppress interferences. An approximate implementation for complexity reduction with little performance loss was also proposed. The bit error rate (BER) performances and extrinsic information transfer (EXIT) charts were presented for Rayleigh fading channels. Simulation results show that our proposed algorithm outperforms other existing ones in severely double-selective channels without increasing computational complexity.Performance evaluation of channel detection for the cooperative network coding in the wireless relay network
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0714
Network coding is regarded as a promising technique to improve system throughput of the Long-Term Evolution (LTE) system. The channel detection technique plays a significant role in the cooperative relay network with network coding. In this paper, an minimum-mean-square-error (MMSE) joint detection strategy for the cooperative network coding is proposed. The receiver utilizes the direct link signals and the forwarding network coded signal for joint detection, and recovers the source data of multiple users. It is shown that with the MMSE joint detection, the relay network with network coding shows better system performance with lower backhaul cost and higher system throughput than the traditional relay network at high signal-to-noise ratio (SNR). In addition, as the number of users increases, the network coding scheme based on the proposed channel detection brings a more significant improvement in throughput at high SNR.A novel 8×8 transform method applied in video coding
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0846
Transform Coding has been playing an important role in video coding and increasingly becomes a research focus especially in the current popular standards such as H.264/AVC, AVS and HEVC. It is important to select an excellent transform method as transform module has a direct impact on the efficiency of video codec. This paper proposes a new 8×8 transform method as well as its integer approximation applied in video coding. Experiments show that it achieves a higher performance.