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The article reports on the 2008 Institute of Electrical and Electronics Engineers (IEEE) Radar Conference held in Rome, Italy in 2008. The technical program covered issues in radar theory and applications and aspects of radar systems for civilian, defense applications, and technology. Also highlighted were the space-time-adaptive-processing (STAP), waveform design, and sensors. It describes 10 conference papers that delve in topics such as multiple input multiple output radar systems and the European effort on radar imaging.

In a recent paper, Cao proposed and analysed a new switching constant false-alarm rate (CFAR) detection algorithm (S-CFAR), which exploits the magnitude of the test cell for the selection of the reference samples. Here we use the order statistic theory to obtain alternative expressions for the detection probability and the false-alarm rate of the S-CFAR in homogeneous background. They are not bulky and thus are easy to calculate for the thresholding parameters. [ABSTRACT FROM AUTHOR]

The article discusses various papers published within the issue including "Bistatic SAR Experiment With the Ingara Imaging Radar," "Compact Polarimetric SAR Interferometry" and "Interferometric Focusing for the Imaging of Humans."

An introduction is presented in which the editor discusses various reports published within the issue on topics which include the adaptive detection of signals, the Gaussian background with unknown covariance matrix, and constant false alarm rate (CFAR) detection.

The problem of state estimation with quantised measurements is considered for general vector state-vector observation model in wireless sensor networks (WSNs), which broadens the scope of sign of innovations Kalman filtering (SOI-KF) and multiple-level quantised innovations Kalman filter (MLQIKF). Adhering to the limited power and bandwidth resources WSNs must operate with, this paper introduces a novel decentralised unscented Kalman filtering (UKF) estimators based on quantised measurement innovations. In the quantisation approach, the region of a measurement innovation is partitioned into L contiguous, non-overlapping intervals. After quantised, the measurement information is broadcasted by using a variable number of bytes coding method. A filtering algorithm for general vector state-vector observation case is developed based on the quantised measurement information. Performance analysis and Monte Carlo simulations reveal that under the same bandwidth constraint condition, the performance of novel quantised UKF tracker, indeed better than those of SOI-KF and MLQIKF in error covariance matrix (ECM) and root mean-square error (RMSE) and almost identical to these of an UKF based on analogue-amplitude observations. [ABSTRACT FROM AUTHOR]

This paper presents a capacity-aware linear minimum mean square error (MMSE) detector for orthogonal frequency-division multiplexing/space-division multiple access (OFDM-SDMA) applications. We derive closed-form expressions for the signal-to-interference plus noise ratio (SINR) performance of OFDM-SDMA systems with linear MMSE detection method, where capacity enhancements have been introduced in the transmit/receive weight computations. Using the derived expressions, we compare the performance of the proposed scheme with the regular multiple-input multiple-output (MIMO)-MMSE system in OFDM-SDMA applications. It is shown that in enhancing the system capacity, the capacity-aware MIMO-MMSE scheme also enhances the SINR, resulting in lower symbol error rate (SER) compared to the conventional MIMO-MMSE beamforming schemes. [ABSTRACT FROM AUTHOR]

The study paper deals with sensor fault detection problem for a class of linear uncertain systems with bounded disturbances and non-zero constant reference inputs. The sensor faults are modelled as multi-mode, named as fault-free mode and faulty modes. A steady-state-based approach is proposed to detect the sensor faults. The steady-state-based approach can be used to detect lock-in-place sensor faults with arbitrary small magnitudes, which has not been well investigated in the literature. A convergent iterative algorithm based on linear matrix inequalities is given to obtain the solutions. A numerical example is given to illustrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

New control paradigms are needed for large networks of wireless sensors and actuators in order to efficiently utilise system resources. In this study, the authors consider the problem of discrete-time state estimation over a wireless sensor network. Given a tree that represents the sensor communications with the fusion centre, the authors derive the optimal estimation algorithm at the fusion centre, and provide a closed-form expression for the steady-state error covariance matrix. They then present a tree reconfiguration algorithm that produces a sensor tree that has low overall energy consumption and guarantees a desired level of estimation quality at the fusion centre. The authors further propose a sensor tree construction and scheduling algorithm that leads to a longer network lifetime than the tree reconfiguration algorithm. Examples are provided throughout the paper to demonstrate the algorithms and theory developed. [ABSTRACT FROM AUTHOR]

Engineers have utilised spectral information and have steadily improved its applications in imaging systems for more than a century. The course of technological developments in colour imaging has been dictated by system improvements measured by their efficacy for direct human consumption. It seems reasonable to us to try to emulate nature and boost capabilities of machine vision systems by optimising the way in which they exploit spectral information. This is a two-step process: first step involves using a few spectrally broad detectors to compress the information content of the scene and the second step constructs spectral discriminants for image segmentation based on a small number of spectrally generated features assigned to each pixel. In animals the discriminant value is attributed to the object as what is called colour. Previous papers have concentrated on the final segmentation step. Here we show a straightforward way to design application-specific spectral sensitivity functions to improve image segmentation. The resulting functions can be used for reliable recognition of objects in a hyperspectral image in real time. These functions can also be used to design task-specific specialised cameras that can outperform current hyperspectral systems in terms of sensitivity, size, power consumption, robustness, price and complexity. [ABSTRACT FROM AUTHOR]

In various adaptive array applications, the desired-user signal arrives from only a relatively small number of directions. The paper proposes an NLMS-based adaptive algorithm that incorporates a direction of arrival (DOA) detection criterion. The criterion stems from Akaike's information criterion and Donoho's thresholding principle. Within ‘low-dimensional’ DOA applications, the inclusion of the DOA detection criterion leads to a reduction in the number of NLMS adapted parameters. The result is significantly improved convergence and tracking speeds, as well as improved nulling of multi-user interference signals. Simulations demonstrate the favourable performance of the proposed NLMS adaptive-array system. [ABSTRACT FROM AUTHOR]

This paper describes a new non-sequential linear phase detector using a standard 0.18 μm CMOS process for high-speed clock and data recovery applications. The new phase detector avoids using DFFs or D-latches in order to achieve high operating speeds up to 10 Gbit/s. Its circuit structure is much simpler than the existing half-rate 10 Gbit/s phase detectors reported so far. Consisting of 1 delay cell, 2 XOR gates and 1 AND gate, the proposed PD consumes 34.58 mW. It exhibits a linear characteristic for low jitter operation and avoids half-cycle skew problem inherent in the conventional linear phase detectors. The simple structure of the proposed PD also has the advantage of lower power consumption compared with other PDs reported in the literature. [ABSTRACT FROM AUTHOR]

If a bee expects food in response to the scent of cocaine or Semtex, for example, then it will stick out its proboscis when it smells that compound too and this uncovers an explosive new area of illicit materials detection. The bees are currently loaded into the holders manually, but stings are pretty rare as the insects are refrigerated first to calm them down. They are trained to a particular compound in a stream of air with a small amount of it on some filter paper. A cotton bud soaked in sugar solution -artificial nectar -is given to the bee straight after it smells the compound. Once this has been done a few times, the bee will automatically stick out its proboscis in expectation of food whenever it smells. [ABSTRACT FROM AUTHOR]

An implementation for the post-Doppler adaptive target detectors enabling an efficient change of the subspace dimension is described. The proposed implementation uses the order recursive structure of the conjugate directions method and does not present any additional computational burden on the processor. The implementation can be particularly useful for the adaptive detectors with an indeterminate number of auxiliary vectors for the clutter covariance matrix estimation. Through the proposed method, the subspace dimension can be easily increased or decreased according to the multiplicity of the auxiliary vectors at no loss of computational efficiency. [ABSTRACT FROM AUTHOR]

The paper gives an overview of the 'smart dust' - small, unobtrusive electronic sensors spread across the landscape. The sensors use the ZigBee low-power wireless standard to send a message to relays mounted on street lamps, which then pass the data to a central computer. This surface-to-surface sensors can link up for the ultimate surveillance and control network of a smart city. [ABSTRACT FROM AUTHOR]

In this paper, we address the radar adaptive detection problem in the case of multiple fluctuating targets with unknown parameters. The unknown parameters are: the number and location of targets, the amplitude and phase of received signals, the Doppler frequency of targets in slowly fluctuating case the target signal vectors in rapid-fluctuating case and the statistical characteristics of noise and clutter. We extract the generalised likelihood ratio test (GLRT) in Gaussian interference with unknown covariance matrix. Owing to high computational complexity of these detectors when the number of probable targets is large, we design a simple detector relying on the GLRT procedure, namely simplified GLR detector for implementation. This detector achieves satisfactory performance under several situations of practical interest and is simpler to implement than the designed GLR detector. Also in slowly fluctuation case, based on adaptive-matched filter (AMF), Kelly's detector (KD) and adaptive coherence estimator (ACE) that are used for single-target detection, some detectors are presented for multiple-target detection called generalised AMF, generalised KD and generalised ACE. Furthermore, in rapid fluctuation case in Gaussian interference with unknown covariance matrix, we propose an intuitive inexpensive detector with low computational complexity, which we will refer to as the generalised energy detector. Simulation results illustrate and compare the performance and the efficiency of the proposed detectors. [ABSTRACT FROM AUTHOR]

This paper deals with the modelling and control of a variable speed doubly fed induction generator-based marine current turbine with and without tidal current speed sensor. The proposed maximum power point tracking control strategy relies on the resource and the marine turbine models that were validated by experimental data. The sensitivity of the proposed control strategy is analysed regarding the swell effect because it is considered as the most disturbing one for the resource model. Tidal current data from the Raz de Sein (Brittany, France) are used to run simulations of a 7.5-kW prototype over various flow regimes. Simulation results are presented and fully analysed. [ABSTRACT FROM AUTHOR]

This paper deals with the problem of non-cooperative target recognition. Specifically, the aim is the automatic recognition of ship targets from inverse synthetic aperture radar (ISAR) images. For this purpose a new two-step multi-feature based technique is proposed; this technique uses a number of features extracted from the ship radar image and matches these features with those extracted from the images obtained by properly projecting the target models of the classification library. Both cases of a priori known or unknown ship aspect angles are considered: the knowledge of the ship aspect (as available from tracking data) allows the selection of the candidate models on the basis of the matching between the ship and the model length, thus resulting in a performance improvement. Moreover, both single- and multi-frame-based processing techniques are proposed in order to assess the performance improvement achievable when an increasing number of ISAR images are involved in the decision; the fusion strategy adopted for the exploitation of the information from the multiple images is also described. The performance of the overall proposed technique is deeply investigated against simulated data. Results of its application to a set of live ISAR images of a ship target are also provided showing the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Multiple-input, multiple-output (MIMO) radars enhance performance by transmitting and receiving coded waveforms from multiple locations. This paper describes MIMO techniques that can be used to improve radar performance, especially in airborne Ground Moving Target Indicator (GMTI) applications. The authors begin by showing how MIMO techniques can lower airborne radar clutter to noise ratios (CNRs). This results in smaller losses when observing stationary or low-velocity targets. Next, the authors consider the implementation of MIMO radar modes using electronically scanned arrays (ESAs). Specifically, the authors show how MIMO techniques, applied to subarray-based ESAs, can cause high grating lobes and/or reduced search rates. To address this problem, the authors describe new space–time waveform coding techniques that can be used to improve performance. Two space–time waveform encoding approaches are proposed: (i) an overlapped virtual transmit subarray approach, and (ii) a beamspace MIMO approach. A third approach, involving conventional MIMO waveforms and irregular subarrays, is also briefly considered. [ABSTRACT FROM AUTHOR]

This study addresses the control of linear systems subject to both sensor and actuator saturations and additive L2-bounded disturbances. Supposing that only the output of the linear plant is measurable, the synthesis of stabilising output feedback dynamic controllers, allowing to ensure the internal closed-loop stability and the finite L2-gain stabilisation, is considered. In this case, it is shown that the closed-loop system presents a nested saturation term. Therefore, based on the use of some modified sector conditions and appropriate variable changes, synthesis conditions in a ‘quasi’- linear matrix inequality (LMI) form are stated in both regional (local) as well as global stability contexts. Different LMI-based optimisation problems for computing a controller in order to maximise the disturbance tolerance, the disturbance rejection or the region of stability of the closed-loop system are proposed. [ABSTRACT FROM AUTHOR]

Video shot boundary detection is the initial and fundamental step towards video indexing, browsing and retrieval. Great efforts have been paid on developing accurate shot boundary detection algorithms. However, the high computational cost in shot detection becomes a bottleneck for real-time applications. The problem of making a balance between detection accuracy and speed is addressed in this paper, and a novel fast detection framework is presented. The general framework that employs pre-processing techniques can improve both detection speed and precision. In the pre-processing stage, adaptive local thresholding is adopted to classify non-boundary segments and candidate segments that may contain shot boundaries. The candidate segments are refined using bisection-based comparisons to eliminate non-boundary frames. Only refined candidate segments are preserved for further detections; hence, the speed of shot detection is improved by reducing detection scope. Moreover, prior knowledge about each possible shot boundary such as its type and duration can be obtained in the pre-processing stage, which can accelerate the consequent hard cut and gradual transition detections. Experimental results indicate that the proposed framework is effective in accelerating the shot detection process, and it can also achieve excellent detection accuracies. [ABSTRACT FROM AUTHOR]

In this paper, a key pre-distribution model with the concept of key pool generation in distributed sensor networks (DSNs) is proposed. In this scheme, additional information is inserted into each group during key pool generation. The nodes in the DSNs can use this extra information to increase system performance. A concrete example is given to clarify this concept and prove that the added information in the scheme can greatly improve connectivity between nodes even if node deployment is sparse or non-uniform. In addition, high connectivity decreases the energy consumption of wireless communication between sensor nodes and extends the life of these nodes. [ABSTRACT FROM AUTHOR]

A multiple-input multiple-output (MIMO) configuration has been studied for communication applications, offering a lot of advantages to mitigate propagation effects because of multipath and fading environments. More recently, MIMO techniques in radar have been proposed. MIMO is discussed in the context of high-frequency surface waves radar (HFSWR). After a short introduction to the MIMO radar technique (a technique which is not new; the RIAS developed by ONERA was probably the first MIMO radar), explores two different applications are explored. The first application aims at improving the resolution and accuracy of a coastal radar, proposed here in a bistatic configuration. Such a radar operates with a wide sparse frequency band and with an equivalent wide aperture, taking advantage of the MIMO configuration. Simulation over a congested area of targets demonstrates the benefit of MIMO over the conventional HFSWR radar, especially in terms of separation of targets. The second application consists in a more practical ship-borne HFWSR configuration compatible with space time adaptive processing (STAP) to improve the detection of slow targets. In this case, a limited number of receiving channels is considered whereas STAP uses the degrees of freedom offered by the transmitting array. The MIMO-STAP is compared with a conventional STAP, showing that theoretical performances should not be affected by the MIMO configuration even if the signals are no longer perfectly orthogonal, because of Doppler shift, once scattered by moving targets. [ABSTRACT FROM AUTHOR]

A common technique for source localisation is to utilise the time-of-arrival (TOA) measurements between the source and several spatially separated sensors. The TOA information defines a set of circular equations from which the source position can be calculated with the knowledge of the sensor positions. Apart from nonlinear optimisation, least squares calibration (LSC) and linear least squares (LLS) are two computationally simple positioning alternatives which reorganise the circular equations into a unique and non-unique set of linear equations, respectively. As the LSC and LLS algorithms employ standard least squares (LS), an obvious improvement is to utilise weighted LS estimation. In the paper, it is proved that the best linear unbiased estimator (BLUE) version of the LLS algorithm will give identical estimation performance as long as the linear equations correspond to the independent set. The equivalence of the BLUE-LLS approach and the BLUE variant of the LSC method is analysed. Simulation results are also included to show the comparative performance of the BLUE-LSC, BLUE-LLS, LSC, LLS and constrained weighted LSC methods with Cramér–Rao lower bound. [ABSTRACT FROM AUTHOR]

This paper deals with timing jitter reduction in the timing recovery loop of a digital QAM receiver. The main contribution, which is derived analytically, is an economical prefilter to reduce the timing jitter in timing recovery loops containing either the early–late or the Gardner timing-error detector (TED). The proposed prefilter has the advantage of being an infinite impulse response filter that is placed inside the TED and runs at the symbol rate. For small roll off factors, it is shown with a computer simulation that a single-pole filter placed inside either the early–late or the Gardner detector is quite effective in reducing the timing jitter. [ABSTRACT FROM AUTHOR]

The paper describes a simple control structure for a vector-controlled stand-alone induction generator (IG) used to operate under variable speeds. Deadbeat current control is developed for a voltage source PWM converter and the three-phase variable speed squirrel-cage IG to regulate DC-link and generator voltages with newly designed phase-locked-loop circuit. The required reactive power for the variable-speed IG is supplied by means of the PWM converter and a capacitor bank to build up the voltage of the IG without the need for a battery and to reduce the rating of the PWM converter with the need for only three sensors. This proposed scheme can be used efficiently for variable speed wind or hydro energy conversion systems. The measurements of the IG system at various speeds and loads are given and show that this proposed system is capable of good AC and DC voltages regulation. [ABSTRACT FROM AUTHOR]

Until now, the sensitivity attack was considered as a serious threat to the robustness and security of spread-spectrum-based schemes, since it provides a practical method of removing watermarks with minimum attacking distortion. Nevertheless, it had not been used to remove the watermark from other watermarking algorithms, such as those which use side-information. Furthermore, the sensitivity attack has never been used to obtain falsely watermarked contents, also known as forgeries. In this paper a new version of the sensitivity attack based on a general formulation is proposed; this method does not require any knowledge about the detection function nor any other system parameter, but just the binary output of the detector, being suitable for attacking most known watermarking methods. The new approach is validated with experiments. [ABSTRACT FROM AUTHOR]

Most of the watermark detection schemes proposed until now imply the general assumption that the image coefficients, which may carry watermarks, can be perfectly characterised by certain model distributions. However, there are always (small) deviations of the actual coefficient distributions from the idealised theoretical models owing to inherent modelling errors and possible attacks to the watermarking systems. These uncertain deviations, although usually small, may degrade or even upset the performance of the existing optimum detectors that are optimised under idealised assumptions. In this paper, we present a new detection structure for additive watermarking in transform domains based on Huber's robust hypothesis testing theory. In order to capture the uncertainties, the statistical behaviours of the image subband coefficients are modelled by a contaminated generalised Gaussian distribution (GGD) instead of the perfect GGD. The robust detection structure is derived as a min–max solution of the contamination model and turns out to be a censored version of the optimum probability ratio test. Experimental results on real images confirm the superiority of the proposed detector over the classical optimum detector. [ABSTRACT FROM AUTHOR]

Passive radars using illuminators of opportunity have attracted much attention in the international radar community. One existing radio transmission system that may be utilised for this purpose is the Global System for Mobile communication (GSM). The paper presents a study showing the feasibility of using a GSM signal for passive radar. The analysis of the GSM waveform, and any significance or influence it has with respect to the passive radar design considerations are investigated in detail. The paper describes fully the design and implementation of a low-cost GSM-based passive radar prototype in addition to the associated signal processing scheme. Numerous measurements for various ground-moving targets were investigated extensively. The preliminary processing results demonstrate the feasibility of using GSM signals as a radar waveform and have the potential capability to detect and track different types of ground-moving targets. [ABSTRACT FROM AUTHOR]

The article discusses various reports published within the issue including "Dynamic Range Improvement and Measurement in Radar Sonar and Keith Ward in "Modeling and Enhancement of Interrupted SAR Imagery."

Dr Elena Plis from SK Infrared, LLC in the US, talks about the research and motivations behind the paper 'Voltage controllable dual-band response from InAs/GaSb strained layer superlattice detectors with nBn design' on page 133. [ABSTRACT FROM AUTHOR]

An analytical method based on the knowledge of the moment generating function of the decision variable, which permits to assess the in-band crosstalk tolerance of direct detection differential phase-shift keying (DPSK) optical systems with receiver imperfections relatively to conventional on-off keying systems, is presented. It is shown that the crosstalk tolerance of DPSK systems can be greatly reduced or even disappear when the receiver imperfections are taken into account. [ABSTRACT FROM AUTHOR]

Lifetime extension is a fundamental concern in wireless sensor networks (WSNs) owing to the limited energy of each sensor. Random and dense deployment of sensors in many applications impose some coverage redundancy in WSNs, which motivates methods to avoid such redundancy for extending the overall lifetime of the networks. An effective method for this purpose is to divide the sensors into a maximum number of disjoint groups called covers, each of which can cover all targets, so that only one cover is active at any time. The problem of obtaining the maximum number of covers has been proved to be NP-hard. In this study, an optimal method is proposed for the problem. The proposed method is based on the transformation of the problem into the well-known Boolean satisfiability (SAT) problem. Simulation results indicate that the proposed method is superior to existing genetic (GAMDSC) and heuristic (MCMCC) methods. Moreover, as an optimal algorithm, it guarantees obtaining an optimum solution, whereas the existing (meta)heuristic algorithms do not. In addition, we extend the proposed method to the K-coverage problem, where each target is supposed to be covered by at least K number of nodes. [ABSTRACT FROM AUTHOR]

In radar target detection, the adaptive normalised matched filter (ANMF) detector is often used to detect moving targets in sea and land clutter environment. Its performance depends on estimation of clutter covariance matrix. The sample covariance matrix (SCM) estimator has been thoroughly analysed for independent and identically distributed Gaussian clutter vectors. Many radar systems on service use range-oversampling receivers. Referred to the range-oversampling model in the weather and oceanic radars, the spatial correlation model of range-oversampled clutter vectors is established, the error of the SCM estimator is analysed, and the range-oversampling gain, relevant to the oversampling factor and the receiver's bandwidth, is derived. The experiments using raw radar clutter data are made to verify the range-oversampling gain, showing that the range oversampling improves the performance of the ANMF detector. [ABSTRACT FROM AUTHOR]

A popular family of sensing systems work using binary sensors. In this study, the behaviour of binary sensing methods is investigated where the individual sensors only return information regarding the target's presence or absence within their own sensing range. In order to enhance their performance the authors propose a new compact distributed algorithm based on a triplet circle intersection principle where they take the central point of their common intersection arc among the sensor detection circles is considered as the target's position. It was shown that the new model can reduce the cost of resourcing as well as decreasing overhead communication traffics; it therefore fits very well with low-power sensor network applications. The experimental test-bench results verify the superior performance of our algorithm. Moreover, the results reveal improved performance criteria for conventional tracking evaluation of the average error and the root-mean-square error because of inherent measurement effectiveness of the target-tracking problem. [ABSTRACT FROM AUTHOR]

The emerging technologies such as the Internet-of-Things, sensors, communication networks, have been or will be introduced to conventional domotics to provide a wide variety of smart home services to facilitate the household appliances or home cares and improve the lifestyles of people. Currently, smart home system are integrated with different features from product line and equipped with various sensors and actuators to meet the requirements of house occupants by specifying their customised user policies. However, the introduction of features and policies may result in undesired behaviours, and this effect is known as feature interactions. In this study, the authors proposed a Semantic Web-based policy interaction detection method with rules to model smart home services and policies with the aids of ontological analysis in the smart home domain, so as to construct a semantic context for inferring the interaction of policies. The authors focus their work on user policies interaction, which are detected by using the Semantic Web rule language in semantic context. The approach is successfully applied to the smart home system and is able to detect 90 interactions among 32 user policies by automated reasoning with tools support as Protégé and Jess. [ABSTRACT FROM AUTHOR]

A number of significant airplane accidents have resulted from windshear encounters during takeoff or landing. In these situations the radar signal received may be affected by a strong ground clutter that may make the conventional windshear detection algorithms implemented on ground-based systems unusable. Typically, the solution to this problem is to employ a clutter rejection filter and then process the filter output to derive weather information. In this study, a parametric bimodal spectral model of the raw radar signal from an airborne Doppler weather radar is proposed. The bimodal shape of the model has been defined as a superposition of clutter and windshear. The model can be used to define a windshear detection algorithm that can also directly estimate the physical weather parameters by using the estimated model parameters without using a clutter rejection pre-filter. Owing to the impossibility of testing a windshear detection system in a realistic environment, a simulated windshear data base has been developed by National Aeronautics and Space Administration (NASA) and Federal Aviation Administration (FAA) during their windshear research programme. The purpose of this study is to define a parametric bimodal spectral model and demonstrate its validity on the NASA-FAA windshear certification data set. [ABSTRACT FROM AUTHOR]

In this study an invariant-set approach to sensor FDI is employed together with control system reconfiguration based on the use of a virtual sensor. In the proposed FDI approach, invariant sets are specified for each considered healthy/faulty situation in the system's sensor structure. The detection mechanism is based on the separation between the computed invariant sets and 'transition' sets where appropriate residual variables 'jump' when faults occur. The closed-loop system is then reconfigured by means of a virtual sensor which is adapted to the detected fault. Furthermore, conditions are derived in terms of bounds on reference signals, noise and disturbances which guarantee the stability of the closed-loop system under the resulting fault tolerant control scheme for all considered fault situations. Simulation results of the proposed scheme on a longitudinal car following scenario and experimental results on a laboratory scale magnetic levitation system confirm the validity of the approach under realistic conditions. [ABSTRACT FROM AUTHOR]

This study introduces a block-based motion estimation algorithm based on projection with adaptive window-size selection. Using one-dimensional (1D) projection, the original 2D block-matching problem is translated to a simpler 1D matching problem which eliminates the majority of potential pixel participation. The authors propose an efficient fast-motion estimation method using an intensity gradient algorithm to reduce the encoding time. The proposed algorithm estimates the texture direction of the block, and then a horizontal or vertical projection is employed for the sum of absolute difference calculation. Experimental results show that the proposed algorithm achieves a greater than 60% time reduction with negligible peak signal to noise ratio (PSNR) loss and BR increments. [ABSTRACT FROM AUTHOR]

In this study, several new detection algorithms are proposed for multi-input/multi-output (MIMO) communication systems transmitting non-circular signals. Unlike the conventional receivers, the proposed detectors estimate the transmitted signal from both the received signal and its complex conjugate version. Analytical results quantifying the performance improvement are provided. As a typical example, extended zero-forcing (EZF) detector and extended minimum mean square error (EMMSE) detector are derived for the real signals. Computational complexity of the proposed algorithms remains the same order as that of the conventional zero-forcing (ZF). Simulation results show that both EZF and EMMSE detectors significantly outperform the conventional minimum mean square error (MMSE) detector, and that the ordered-successive-interference-cancelling (OSIC) version of the EZF (or EMMSE) detector has a quasi-optimal performance in terms of bit error rate (BER). [ABSTRACT FROM AUTHOR]

The authors propose some robust adaptive multiuser detection schemes for direct-sequence code-division multiple-access multipath frequency-selective fading channels. Multiple access interference (MAI) and intersymbol interference (ISI) are presented in an identical format using expanded signal subspace, which facilitates multiuser detection in a symbol-by-symbol fashion. This study contributes to the theoretical aspect of adaptive multiuser detection by proving that the optimum linear multiuser detectors that achieve maximum signal-to-interference-plus-noise ratio (SINR) must exist in the signal subspace, and the theoretic SINR upper bound is also derived. Another contribution of this study is to propose the design of multiuser detectors in an expanded signal subspace, and introduce subspace estimation and Kalman filtering algorithms for their adaptive implementation. To robustify the adaptive detectors against subspace estimation and channel estimation errors, a modified projection approximation subspace tracking (PAST) algorithm is proposed for subspace tracking. It is demonstrated by simulations that these adaptive detectors effectively suppress both MAI and ISI and converge to the optimum SINR. They are robust against subspace estimation errors and channel estimation errors compared to the conventional Wiener minimum mean square error (MMSE) detector. [ABSTRACT FROM AUTHOR]

The authors investigate the performance of the probabilistic data association (PDA) detector in a cooperative system that consists of a source, a relay and a destination, which are all multiantenna nodes. Taking advantage of the soft information provided by the PDA detector at the relay, the authors present a relaying scheme in light of which the relay can just transmit signals to the destination under the condition of having high detection reliability. Characterised by the means on how to exploit the information provided by both the source and the relay at the destination, two detectors named as combing PDA (C-PDA) and iterative PDA (I-PDA) are developed, respectively. C-PDA adopts one PDA detector to retrieve the transmit signals by combining the received signals from the source and the relay. I-PDA employs two concatenated PDA detectors to perform detection with respect to the received signals from the source and the relay, respectively. Just as in turbo decoding, soft information is iteratively exchanged between these two concatenated PDA detectors to enhance the performance of I-PDA. Simulation results have shown that significant performance gains can be achieved by both C-PDA and I-PDA over the conventional zero-forcing detector. [ABSTRACT FROM AUTHOR]

With the advances in traffic sensor technology, more useful traffic information can be generated directly or indirectly. This study introduces an innovative single-loop speed estimation model using recent traffic sensor technology. Proposed speed estimation model can be easily integrated with existing loop systems without requiring any roadside construction work. With accurately estimated speed, accurate travel time can also be derived. This will help disseminate accurate real-time traffic information, and therefore improve overall network performance, and traffic control/operation. The spatial and temporal transferability of the developed model was tested and encouraging results were obtained. Automated vehicle grouping is also one of the main contributions of the proposed model. [ABSTRACT FROM AUTHOR]

This study is concerned with the state estimation problem for a kind of asynchronous multirate multisensor dynamic system, where observations from different sensors are randomly missing. The system is described at the highest sampling rate with different sensors observing a single target independently with multiple sampling rates. The optimal state estimate is obtained by use of the multiscale system theory and the modified Kalman filter. This study extends the federated Kalman filter to the case of asynchronous multirate multisensor dynamic systems with measurements randomly missing. The presented algorithm is proven to be effective in the sense of linear minimum mean squared error. The feasibility and efficiency of the algorithm are illustrated by a numerical simulation example. [ABSTRACT FROM AUTHOR]

A city-wide wireless sewer sensor system becomes 'intelligent' by having adaptive manhole cover antennas. Hundred and fifty wireless sensor nodes have been developed and deployed to monitor the sewer flow and to reduce the frequency of the combined sewer overflow (CSO) during heavy storm runoff in a mid-sized city: South Bend, Indiana in the US. The challenge for the wireless designer is to design a radiator that operates below ground as well as to improve the communication performance of the wireless sensor system. In this study, the authors replace a conventional cast-iron manhole cover with a composite manhole cover to create a radiator which is not only mechanically strong but electrically functional. The electrical characteristics of the composite are analysed by finding the relative permittivity and loss tangent. In addition, the effect of adaptive antennas is demonstrated to be extremely useful in terms of the packet reception rate and received signal strength. Measured results indicate that angular diversity significantly enhances received signal strength and the packet reception rate in the presence of interferers. The slot diversity antenna designed herein increased packet reception rate by 52.8% in the fielded system, compared to a uniformly radiating dipole antenna in the azimuthal plane. [ABSTRACT FROM AUTHOR]

Second-order intermodulation is a great drawback in zero-intermediate frequency (IF) receivers. Many complex techniques for distortion cancelling have been proposed in the literature. In this study, the authors propose a simple architectural solution for second-order intermodulation intercept point (IIP2) improvement and also theoretically and experimentally demonstrate the high rejection level abilities. To determine its performance, a classical in-phase and quadrature (IQ) demodulator was also designed and used as a reference. In order to compare their non-linear behaviour in the presence of interfering signals, two types of zero-IF demodulators were tested in this work in terms of error vector magnitude and bit error rate. This study shows that by using the three-phase architecture it is possible to gain 20 dB in blocking effect rejection in comparison to the classical IQ architecture. [ABSTRACT FROM AUTHOR]

The ratio of the increments of flux linkages (RIFLs) of the primary–secondary, primary–tertiary and secondary–tertiary windings is the same as the corresponding turns ratio during normal operating conditions, magnetic inrush and over-excitation. The RIFL differs from the turns ratio during an internal fault. In this study, the authors propose an algorithm for protection, a faulted phase and winding identification for the three-winding transformer using the increments of flux linkages (IFLs). The IFLs of each pair of windings are estimated for a single-phase and a three-phase transformer with wye-connected windings. For a three-phase transformer with delta-connected windings, the differences of the IFLs are estimated to use the line currents because the delta winding currents are practically unavailable. In this study, six detectors are suggested for fault detection; three additional detectors and a rule for the faulted phase and winding identification are presented as well. The proposed algorithm can not only detect an internal fault, but also identify the faulted phase and winding of a three-winding transformer. The various test results with electromagnetic transients program (EMTP) generated data show that the proposed algorithm successfully discriminates the internal faults from normal operating conditions including magnetic inrush and over-excitation. This study concludes by implementing the proposed algorithm into a prototype relay based on a digital signal processor. [ABSTRACT FROM AUTHOR]

It has been shown that the motor cables in variable-speed electric drives are a feasible medium for power line communication (PLC). Communication between an electric motor and an inverter is required because of sensors installed at the motor. These sensors are used in the motor control and in the diagnostics. A PLC signal is coupled through a coupling interface to the motor power cable. Being the only component in the channel that can be affected in the communication system design, the coupling interface thus constitutes an essential part of the system. Different coupling interfaces are already introduced for normal low-voltage networks, but not for inverter-fed networks. This study considers the applied channel characteristics and noise scenario from the viewpoint of communication. Two different coupling interfaces, capacitive and inductive, are developed and analysed by laboratory tests. The developed inductive coupling method makes it possible to create a broadband data transmission link between a motor and an inverter without a du/dt filter at the inverter output. [ABSTRACT FROM AUTHOR]

Distributed aperture radars represent an interesting solution for target detection in strong interference environments. Distributed apertures provide improved angular resolution or are able to view a target from multiple look-angles, thereby exploiting scintillation. However, because of the large distances between array elements, both target and interfering sources are in the near field of the antenna array. Furthermore, because of the relative motion between antenna elements and interference sources, the clutter Doppler frequency is not stationary. Recent works have demonstrated the benefits of combining frequency diversity and space–time adaptive processing (STAP) for distributed aperture radars. In this study a new waveform diversity system model is developed. Using orthogonal signalling, the receivers can treat the incoming signals independently, solving several bistatic problems instead of the initial multistatic problem. The authors also apply adaptive techniques to counteract the range dependency of the clutter Doppler frequency. In particular, the authors apply the joint domain localised algorithm, specifically chosen because of its need for only limited secondary data. [ABSTRACT FROM AUTHOR]

A new approach for active-sonar target detection and bearing estimation from a mobile two-dimensional array of sensors operating in a predominantly noisy environment is presented. Sensor-level adaptive noise cancellation featuring an unconventional method for reference-noise estimation is the key preprocessing step in the proposed approach. A signal-subspace algorithm resulting from two-stage optimisation based on a generalised eigendecomposition of the signal plus (residual) noise covariance matrix is employed to estimate the bearing of the detected target. Simulation results conclusively demonstrate that the proposed scheme is capable of performing target detection and the subsequent two-dimensional bearing estimation with a high degree of reliability at signal-to-noise power ratios as low as -70 and -40 dB, respectively. [ABSTRACT FROM AUTHOR]