Search

In this paper, we address the design of a navigation control algorithm for the autonomous landing of a quadrotor on a moving mobile platform. The quadrotor's velocity is unknown, and we assume that it is equipped with an on-board downward-looking single camera for determining its position relative to the target. The proposed autonomous landing operation proceeds in three phases: the search phase, the homing phase, and the landing phase. To prepare for these phases, a safety sphere with a desired radius having the target position as its center is constructed along with a virtual target point that can move on its surface. During the docking procedure, the quadrotor is first commanded to reach the virtual target point; as it approaches this target point, a second stage is initiated to provide the quadrotor with more precise guidance to land safely on the mobile platform. The core design of the landing algorithm is proposed based on a concise adaptive tracking control scheme using backstepping and dynamic surface control. Simulations are carried out to validate the effectiveness of the proposed guidance landing control approach. [ABSTRACT FROM PUBLISHER]

This paper addresses the coherent integration problem for detecting a high-speed target, involving range walk (RW) within the coherent processing time. A fast method based on sequence reversing transform is proposed to eliminate the RW and achieve the coherent accumulation. The proposed method is simple and fast since it can be easily implemented by using complex multiplications, the fast Fourier transform (FFT) and the inverse FFT. Compared with the Radon–Fourier transform and moving target detection methods, the presented algorithm can avoid the blind speed sidelobe and make a good balance between the computational cost and the detection ability. Finally, several simulations are provided to demonstrate its effectiveness. [ABSTRACT FROM PUBLISHER]

DC fault current is contributed by various distributed energy resources in dc distribution systems. The tightly coupled dc distribution systems have relatively low line impedance values. The fault current increases fast because of the low impedance. Some converters in dc distribution systems include fault current limiting function. The controlled fault currents at different locations are very close. Thus, it is important to design a reliable and fast fault detection and location method for dc distribution systems. This paper proposes a novel local measurement-based fault location algorithm for tightly coupled dc distribution systems. The proposed fault location algorithm can estimate the equivalent inductance between a protective device and a fault in less than 1 ms. The performance of the developed protection algorithm was validated by numerical simulation and hardware tests. [ABSTRACT FROM AUTHOR]

The recently-developed nested neutral-point clamped (NNPC) converter is a four-level converter for medium-voltage high-power applications. It has some merits such as operating over wide voltage ranges (2.4–7.2 kV) without switching devices in series and less diodes or capacitors when compared with classical four-level topologies. But it has severe voltage balancing problems under low output frequency conditions when conventional space vector modulation (SVM) or sinusoidal pulse width modulation (SPWM) is applied, which limits its wide applications. In order to solve this issue, a space virtual-vector modulation (SVVM) along with a voltage balance control (VBC) algorithm is proposed in this paper. It helps reduce the voltage ripples greatly and maintain them within an acceptable region under low output frequency conditions. Therefore, it guarantees even voltage stresses among switching devices and extends the NNPC converter's applications. Principles of the proposed SVVM and VBC algorithms are elaborated in detail, and the voltage balancing performance is investigated and compared with the cases where conventional SVM and SPWM with the same VBC are applied. The relationship curves between voltage ripples and flying capacitance, output power, and output frequency have been explored and compared for both conventional SVM and proposed SVVM. Simulation and experimental results are presented to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, we propose a resource management scheme for on-demand video streaming in orthogonal frequency-division multiple access (OFDMA) networks with both time-varying channels and a user's personalized quality requirement. We design a user quality satisfaction model to evaluate the degree of the user quality satisfaction with respect to his/her personalized quality requirement. To perform the dynamic resource management, we propose a joint rate control (RC) associated with the quality adjustment at the application layer and resource allocation (RA) associated with the power allocation and subcarrier assignment at the physical layer. By using the Lyapunov optimization technique, we develop a joint RC and RA (JRCRA) algorithm to maximize the time-averaged quality satisfaction of all users (QSAU). We show that the QSAU achieved by the JRCRA algorithm without any prior knowledge of the channel statistics can arbitrarily attain the optimal QSAU achieved by the algorithm with a complete knowledge of the channel statistics. Simulation results verify the advantages of the proposed JRCRA algorithm. [ABSTRACT FROM PUBLISHER]

Typical algorithms of multidimensional space-vector pulsewidth modulation (SVPWM) divide (n –1) dimensional space into (n–1)/2 subplanes with decoupling matrix or symmetrical component approach. However, the determination of effective sectors and appropriate space voltage vectors takes a heavy computing burden. Taking the five-phase inverter as example, the relationship between the operation time of branch switches and the dwell times of active space vectors in the SVPWM method is analyzed in this paper. Then, the branch space voltage vector (BSVV) corresponding to the individual active branch voltage is defined and the synthesis of other active space voltage vectors using BSVVs is given. Furthermore, only the BSVVs are chosen as the base vectors to synthesize the reference voltage vector, and a novel SVPWM algorithm is present. The operation time of branch switch is deduced, and the equivalence of the normalized load-phase voltages and operation times of branch switches is emphasized and used to analyze the simulation results. The zero-sequence voltage vector is also included in the algorithm as a parameter and its effects on the dwell time of the BSVVs, the modulation index and the common-mode voltage are explicated. Finally, the extension to an n-phase system is discussed. The algorithm eliminates the selection of sectors and proper active space vectors, and can effectively control the dwell time of switches of multiphase inverter. Experimental results proved the feasibility and effectiveness of the algorithm. [ABSTRACT FROM AUTHOR]

One of the chief challenges of the finite-difference time-domain (FDTD) subgridding algorithm is developing a field-coupling scheme to avoid late-time instability resulting from spatial interface between regions with different meshes. This paper introduces the concept of the nonuniform grid method to appropriately handle the tangential electric component on the spatial interface of the two meshes. This study analyzed shielding effectiveness of metallic enclosures with apertures. A novel subgridding algorithm was employed to locally refine the region containing a thin perfect electric conducting (PEC) film with apertures through FDTD simulation. Image theory was implemented to obtain an interpolation scheme of the magnetic fields as the sub-boundary surface when a thin PEC film traverses the subgridding interface. The numerical accuracy and stability of the proposed method were verified by comparing with results from other established methods. [ABSTRACT FROM PUBLISHER]

In this paper, the downlink of a clustered coordinated multicell multiuser multiple-input multiple-output (MIMO) system is considered, and various low-complexity user scheduling algorithms to maximize the sum rate are proposed. The users' data signals are transmitted cooperatively via the base stations (BSs) of a cluster within the sectorized multicell heterogeneous cellular network. Exhaustive search as the optimal scheduling method is extremely complex, particularly for large numbers of users requesting service. We therefore propose suboptimal scheduling algorithms based on the lower complexity metaheuristic stochastic optimization techniques of simulated annealing (SA) and particle swarm (PS). Moreover, a hybrid algorithm combining the traits of PS and a greedy scheduler is also proposed. The performance and complexity of these algorithms are evaluated for a heterogeneous system model employing different precoding methods. Assessing the algorithms' performance via computer simulations, the effectiveness of the proposed schemes in terms of sum rate is demonstrated, yielding performance very close to that of the exhaustive search at much lower complexity. For each precoding method used in the employed system model, the best corresponding approach to scheduling from our proposed algorithms is determined. [ABSTRACT FROM AUTHOR]

Network lifetime predictability is an essential system requirement for the type of wireless sensor network (WSN) used in safety-critical and highly-reliable applications. All sensor nodes in these time-critical WSNs should meet the lifetime constraint at any time instance, else it may cause severe consequences that involve economic losses, or even fatalities. In the literature, clustering sensors into groups is a popular strategy to maximize the network lifetime, but none of the clustering algorithms address the predictability issue for time-critical WSNs. In this paper, the High Energy First (HEF) clustering algorithm is chosen as a design reference model, which is proved in this paper to be an optimal clustering policy under certain ideal conditions. To address network lifetime predictability in practice, the network lifetime bounds and feasibility test for the HEF are developed via the worst case energy consumption analysis. The network simulator 2 (NS2) is used to verify the proposed network lifetime predictability model, and the results show that the derived bounds of the predictability provide accurate estimations of the system lifetime. [ABSTRACT FROM AUTHOR]

Equal allocation of bandwidth and/or power may not be efficient for wireless multi-user networks with limited bandwidth and power resources. Optimal joint bandwidth and power allocation strategies for wireless multi-user networks with and without relaying are proposed in this paper for 1) the maximization of the sum capacity of all users; 2) the maximization of the worst user capacity; and 3) the minimization of the total power consumption of all users. It is shown that the proposed allocation problems are convex and, therefore, can be solved efficiently. Moreover, joint bandwidth and power allocation for admission control is considered. A suboptimal greedy search algorithm is developed to solve the admission control problem efficiently. Instructive analysis of the greedy search shows that it can achieve good performance, and the condition under which the greedy search is optimal is derived. The formal and in-depth analysis of the greedy search algorithm presented in this paper can serve as a benchmark for analyzing similar algorithms in other applications. The performance improvements offered by the proposed optimal joint bandwidth and power allocation are demonstrated by simulations. The advantages of the suboptimal greedy search algorithm for admission control are also shown in numerical results. [ABSTRACT FROM PUBLISHER]

In this paper, a sensorless controller for an interior permanent-magnet synchronous motor is presented based on well-known high-frequency signal injection techniques. The issue of the demodulation process is the key point of this paper. A novel approach based on discrete Fourier transform and nonconventional reference frame transformation is presented, allowing a simple and robust noncoherent demodulation, i.e., in which no information about the carrier phase is needed. In the classically adopted coherent approaches, in fact, uncertainty about carrier phase reflects in uncertainty in the demodulated signal amplitude, affecting observer gains and signal-to-noise ratio and definitively providing a degradation of the performance of the estimator. Analytical development of the sensorless algorithm, including the demodulation technique, is provided. A complete investigation by simulation is carried out aiming at showing the performance of the proposed method. Finally, experimental results are presented based on a prototype motor drive for city scooters. [ABSTRACT FROM AUTHOR]

This paper compares the performance of source-tuner noise-parameter extraction methods used to measure noise parameters of low-noise amplifiers that have very low (<1 dB) noise figures. The methods discussed are known as the Cold method and the modified Y-factor method (or Hot-Cold method). The paper describes equations used in the extraction algorithms. In a Monte Carlo analysis by randomly adding various sources of uncertainties to "measurements," created with a computer simulation, performances of the noise parameter extraction methods are compared. It is shown that the iterative Cold method and the direct Cold method are the best at extracting Rn and Γopt noise parameters in terms of lowest standard deviation and close proximity of the extracted mean values to the true values. The simplified Cold method, used in a number of commercial systems, has largest systematic offsets in extracted noise parameters while being the quickest to perform. The modified Y-factor method is the slowest to perform due to additional time required for hot measurements. This method is marginally the most accurate to extract Fmin. These conclusions are also supported with measurement results. This study assembles in one place necessary theoretical background information to serve as a reference for those who are working in the field of noise parameter extraction using tuner-based methods. [ABSTRACT FROM AUTHOR]

This paper considers a noncooperative game in which competing users sharing a frequency-selective interference channel selfishly optimize their power allocation in order to improve their achievable rates. Previously, it was shown that a user having the knowledge of its opponents' channel state information can make foresighted decisions and substantially improve its performance compared with the case in which it deploys the conventional iterative water-filling algorithm, which does not exploit such knowledge. This paper discusses how a foresighted user can acquire this knowledge by modeling its experienced interference as a function of its own power allocation. To characterize the outcome of the multiuser interaction, the conjectural equilibrium is introduced, and the existence of this equilibrium for the investigated water-filling game is proven. Importantly, we show that both the Nash equilibrium and the Stackelberg equilibrium are special cases of the conjectural equilibrium. We also develop practical algorithms to form accurate beliefs and select desirable power allocation strategies. Numerical simulations indicate that a foresighted user without any a priori knowledge of its competitors' private information can effectively learn how the other users will respond to its actions, and induce the entire system to an operating point that improves both its own achievable rate as well as the rates of the other participants in the water-filling game. [ABSTRACT FROM AUTHOR]

Providing VCR-like operations in Peer-to-Peer (P2P) environments is a significant challenge. This paper proposes a distributed Storage-assisted Data-driven overlay Network (SDNet) to support P2P Video-on-Demand (VoD) services. It integrates two networks: a Data-driven Overlay Network (DONet) and a multi-way tree. DONet is enhanced and used for the routine video distribution based on the buffer overlapping mechanism and gossip protocol. A novel algorithm which uses a multi-way tree structure and extra pre-fetching buffers at the nodes is proposed to support efficient VoD operations. Videos are divided into uniform segments, pre-fetched and stored in a distributed manner along the tree topology. The cooperation between DONet-based video delivery and the tree-located multimedia components enable multimedia streaming interactive commands to be performed efficiently. This paper presents and discusses the structure of SDNet and the distributed storage scheme and details the cooperation procedure. Simulation-based testing results show how the proposed SDNet is an efficient interactive streaming solution in a P2P environment. [ABSTRACT FROM AUTHOR]

Abstract-This paper studies the blind block synchronization problem in block transmission systems using linear redundant precoders (LRP). Two commonly used LRP systems, namely, zero padding (ZP) and cyclic prelix (CP) systems, are considered in this paper. In particular, the block synchronization problem in CP systems is a broader version of timing synchronization problem in the popular orthogonal frequency division multiplexing (OFDM) systems. The proposed algorithms exploit the rank deficiency property of the matrix composed of received blocks when the block synchronization is perfect and use a parameter called repetition index which can be chosen as any positive integer. Theoretical results suggest advantages in blind block synchronization performances when using a large repetition index. Furthermore, unlike previously reported algorithms, which require a large amount of received data, the proposed methods', with properly chosen repetition indices, guarantee correct block synchronization in absence of noise using only two received blocks in ZP systems and three in CP systems. Computer simulations are conducted to evaluate the performances of the proposed algorithms and compare them with previously reported algorithms. Simulation results not only verify the capability of the proposed algorithms to work with limited received data but also shown significant improvements in the block synchronization error rate performance of the proposed algorithms over previously reported algorithms. [ABSTRACT FROM AUTHOR]

This paper presents a way to access both the multiple-order and parameters of a multidimensional complex number autoregressive (AR) model through matrix factorization. The principle of this technique consists of the transformation of the multidimensional model to a pseudo simple-input simple-output AR model, then performing factorization of the covariance matrix of the data. This factorization then leads- to a recursive form of the parameter and order estimation. This paper makes two principal contributions. The first is a generalization of one dimensional factored form algorithm, and the second is that it makes it possible to access all the possible different orders and parameters of a multidimensional complex number AR model of any dimension, whereas classical approaches are limited to at most four-dimensional models. Computer simulation results are provided to illustrate the behavior of this method. [ABSTRACT FROM AUTHOR]

Service discovery is indispensable to ad hoc networking where establishing a stand-alone and self-configurable communication environment is the main objective. This paper concentrates on designing a distributed service discovery model for service sharing among diverse mobile devices in mobile ad hoc networks (manets). This model is built on top of the network layer of the TCP/IP stack and benefits from the up-to-date routing information enabled by proactive routing protocols that attempt to keep the information in the routing tables of the mobile nodes current. The designed system is based on storing service descriptions in selected nodes that are searched in accordance to the proposed Minimum Distance Packet Forwarding (MDPF) algorithm. In addition to identifying and analyzing the design parameters of the system, this paper studies the delay and traffic performance using analytical derivations and experimental evaluations based on the ns-2 network simulation software. The system is intended to be used in a collaborative manet environment whereby a mobile node can consume services, share them, or facilitate such sharing by helping other nodes find them. [ABSTRACT FROM AUTHOR]

We describe in detail the theoretical and practical implementation aspects of a simulation for marine radars which can, in particular, be used in multistatic configurations. Since the simulator is intended to deliver pseudoraw signals, it can be used later as a tool to benchmark and improve postprocessing algorithms such as bistatic synthetic aperture radar focusing algorithms and ship wake detection algorithms. The work is divided into two parts. This paper reviews and recalls theoretical prerequisites necessary in implementing such a simulator. Included are the full derivation of the bistatic radar equation from the transmitter to the receiver, accounting also for the transmit-receive time, a description of the sea state phenomenology, a review of the theory of electromagnetic scattering from the sea surface, and the presentation and validation of the method used in the simulation. A companion paper discusses the practical implementation aspects of the simulator as well as an analysis of our results. [ABSTRACT FROM AUTHOR]

This paper presents a novel compact passive modeling technique for high-performance RF passive and interconnect circuits modeled as high-order resistor-inductor-capacitor-mutual inductance circuits. The new method is based on a recently proposed general s-domain hierarchical modeling and analysis method and vector potential equivalent circuit model for self and mutual inductances. Theoretically, this paper shows that s-domain hierarchical reduction is equivalent to implicit moment matching at around s = 0 and that the existing hierarchical reduction method by one-point expansion is numerically stable for general tree-structured circuits. It is also shown that hierarchical reduction preserves the reciprocity of passive circuit matrices. Practically, a hierarchical multipoint reduction scheme to obtain accurate-order reduced admittance matrices of general passive circuits is proposed. A novel explicit waveform-matching algorithm is proposed for searching dominant poles and residues from different expansion points based on the unique hierarchical reduction framework. To enforce passivity, state-space-based optimization is applied to the model order reduced admittance matrix. Then, a general multiport network realization method to realize the passivity-enforced reduced admittance based on the relaxed one-port network synthesis technique using Foster's canonical form is proposed. The resulting modeling algorithm can generate the multiport passive SPICE-compatible model for any linear passive network with easily controlled model accuracy and complexity. Experimental results on an RF spiral inductor and a number of high-speed transmission line circuits are presented. In comparison with other approaches, the proposed reduction is as accurate as passive reduced-order interconnect macromodeling algorithm in the high-frequency domain due to the enhanced multipoint expansion, but leads to smaller realized circuit models. In addition, under the same reduction ratio, realized models by the new method have less error compared with reduced circuits by time-constant-based reduction techniques in time domain. [ABSTRACT FROM AUTHOR]

This paper describes the dynamic overmodulation strategies for fast torque control of the high-saliency-ratio ac motor. For the high-saliency-ratio ac motor, the dynamic control of both d- and q-axes currents is required for fast torque control with optimal efficiency. However, in transient operation, the d- and q-axes current regulators are easily saturated even at low speed because the stator inductance is designed large enough to generate the desired reluctance torque. With the conventional overmodulation strategies, the current regulation performance degrades severely compared to a nonsalient motor. In this paper, the drawbacks of the conventional overmodulation strategies are investigated and a dynamic overmodulation strategy is proposed to improve the current response to fast transients. For the effective implementation of the strategy, a practical algorithm is also presented. The performance of the proposed strategy is con- firmed by computer simulation and experiment with a 3.75-kW axially laminated synchronous reluctance motor and an interior Permanent-magnet synchronous motor for 42-V integrated starter-generator applications. [ABSTRACT FROM AUTHOR]

For coherent detection, block-coded modulation is a bandwidth efficient scheme. In this paper, we propose theorems about the error performance of block-coded modulation using Mary phase-shift keying (MPSK) for noncoherent detection. Based on these theorems, we propose a novel block-coded modulation scheme for noncoherent detection called noncoherent block-coded MPSK. The proposed scheme provides flexible designs of noncoherent block codes with different code rate, block length and error performance. Good noncoherent block codes can be easily obtained by properly choosing binary linear block codes as the component codes. Moreover, noncoherent block codes of this new scheme can be decoded by multistage decoding, which has the advantage of low complexity and satisfactory error performance. In this paper, two algorithms of multistage decoding for noncoherent detection are proposed as welt. The error performance of some designed codes and decoding algorithms is verified by computer simulation. [ABSTRACT FROM AUTHOR]

In this paper, we propose two adaptive notch filters (ANFs) for sinusoids embedded in a noisy environment. Both of the ANFs, as usual, are structurally composed of a time-variant infinite-impulse-response (IIR) filter that serves as a line-enhancer and an adaptive mechanism that serves as a frequency estimator. The novelty of ANFs is that the derivations of the coefficient-up- dating algorithms for the adaptive mechanisms are both inspired by a discrete oscillator model and, moreover, are both independent of the structures of the line-enhancement filters chosen. In this paper, a second-order IIR bandpass filter is selected to serve the line-enhancement portions for both of the two ANFs. Analyses and computer simulations show that the performances of the proposed ANFs are very promising. [ABSTRACT FROM AUTHOR]

Multiple-access interference is one of the major impediments in the reverse link of code-division multiple-access (COMA) systems, due to the synergy of the users' spreading codes, transmission delays, and the channel characteristics. A space-time dynamic signature-assignment (DSA) algorithm was briefly described by the authors in a previous paper. In this paper, we further elaborate on the space-time DSA approach and its receiver structure for the reverse link of direct-sequence (DS)-CDMA systems using multiple antennas at the receiver. The space-time DSA dynamically assigns the users' spreading codes and transmission delays, i.e., to assign the user signatures, in order to minimize mutual crosscorrelations. In assigning the signatures, the USA adopts a low-complexity iterative algorithm which utilizes channel information and aims to maximize the signal-to-interference-plus-noise ratio of the poorest performing user at the base station. Analytic results as well as, further simulation results are provided to support our arguments. [ABSTRACT FROM AUTHOR]

In order to achieve higher efficiency for the unregulated LLC series resonant converter, the switching frequency must be equal to the resonant frequency. However, since the converter works in open-loop condition, the switching frequency usually deviates from the resonant frequency in real converter. This paper proposed a new control method to track the resonant frequency of the unregulated LLC series resonant converter. Theoretically, the time of zero diode current in secondary is zero when the working frequency is equal or greater than the resonance frequency, and it is changed as the frequency varies when the working frequency is less than the resonance frequency. The proposed control algorithm is based on the time measurement of zero diode current to realize the resonance frequency tracking. A closed-loop digital controller is designed to realize the proposed tracking approach. The simulation and experiments are conducted to verify the proposed tracking approach. The simulation and experimental results show that (1) the switching frequency can be well controlled to track the resonant frequency, and (2) the tracking accuracy can be at least 96%. [ABSTRACT FROM AUTHOR]

This paper describes an integrated chassis control (ICC) algorithm of differential braking, front/rear traction torque, and active roll moment control. The integrated control algorithm is designed to maximize driving velocity and enhance vehicle lateral stability in cornering. The target longitudinal acceleration is determined based on the driver's intention and vehicle current status to ensure vehicle lateral stability in high-speed maneuvering. An optimization-based control allocation strategy is used to distribute the actuator control inputs optimally under consideration of tire and vehicle limitations. Closed-loop simulations of a driver–vehicle–controller system were conducted to investigate the performance of the proposed control algorithm. The performance of the ICC has been compared with those of individual chassis control systems, such as electronic stability control, four-wheel drive (4WD), and active roll control system. The simulation results show that the proposed ICC algorithm improves the performance in high-speed cornering with respect to driving speed without losing stability, compared with individual chassis control systems. [ABSTRACT FROM PUBLISHER]

This paper proposes an algorithm to control the suspension dynamics with an energy regeneration capability and high conversion efficiency. Central to the concept is the development of a switched-mode rectifier (SMR) that is capable of providing either an equivalent positive or negative damping and alternating between regenerative and motoring modes. Simulation results are presented to demonstrate power flow in regeneration and motoring modes and verify the equivalent damping characteristic and vibration energy harvesting. The studies are conducted on a small-scale proof-of-concept electromagnetic suspension system excited by emulated International Standard Organization (ISO) 8608 road profiles. An autonomous start/stop algorithm is proposed such that autonomously turns on or off the converter. This mechanism mitigates quiescent power consumption of auxiliary integrated circuits (ICs) such as gate drivers and current transducers, therefore increasing the conversion efficiency of the power electronics throughout an ISO standardized variable-speed driving cycle. The autonomous start/stop algorithm is implemented experimentally to demonstrate its feasibility under typical standardized driving cycles. [ABSTRACT FROM PUBLISHER]

This paper describes an integrated speed and steering control driver model for vehicle–driver closed-loop simulation at high-speed maneuvering. In numerous research studies, the performance of vehicle control systems is validated via closed-loop computer simulations due to safety, cost, and repeatability issues. A driver model for the analysis of interactions between vehicle systems and drivers is a significant part of the validation. In particular, in developing a chassis control system, limit-driving characteristics of the actual driver, which mainly affects the performance of the system, has to be taken into consideration. Thus, the proposed driver model is developed to realize the actual driver's driving pattern. A speed control part of the proposed driver model consists of two modules, i.e., the real-time velocity planner and the motion stabilizer. The former plans the desired velocity profile from curvature information on a preview desired path in real time. The latter, i.e., the motion stabilizer, is developed to cope with losing maneuverability through deceleration because there is an obvious limitation to securing stability with velocity profile planning only. On the other hand, a steering control part of the proposed driver model utilizes the yaw-rate gain-based self-adaptation algorithm. An actual driver drives a vehicle without an exact understanding of system dynamics, and the self-adaptation algorithm is adequate for this characteristic accordingly. The proposed driver model has been validated by comparison with an expert driver's driving data, collected on the Korea International Circuit in Yeongam, Korea. [ABSTRACT FROM PUBLISHER]

A new formulation of the auxiliary difference equation (ADE) finite-difference time-domain (FDTD) algorithm for the simulation of dispersive materials has been presented in the literature. Although flexible and efficient, this algorithm suffers from instability when modeling lossy high contrast dielectrics. In this paper, we adapt this ADE-FDTD formulation and present alternative algorithms for modeling static conductivity and Debye dispersion. The stability of these algorithms is assessed by numerical simulation in a wide variety of dielectric media, and their performance is compared to the existing algorithm by means of a simulation of the reflection of a plane wave from a dielectric boundary. Results and comparison with theory demonstrate the stability and accuracy of the new methods. The flexibility, computational efficiency, and ability to model a wide range of materials make these new methods highly attractive compared to other dispersive FDTD algorithms, particularly for modeling materials with multiple dispersion models. [ABSTRACT FROM PUBLISHER]

This paper presents a new strategy to correct the Earth data corrupted by spurious samples that are randomly included in the multiplexed data stream provided by the MADRAS instrument. The proposed strategy relies on the construction of a trellis associated with each scan of the multichannel image, modeling the possible occurrences of these erroneous data. A specific weight that promotes the smooth behavior of the signals recorded in each channel is assigned to each transition between trellis states. The joint detection and correction of the erroneous data are conducted using a dynamic programming algorithm for minimizing the overall cost function throughout the trellis. Simulation results obtained on synthetic and real MADRAS data demonstrate the effectiveness of the proposed solution. [ABSTRACT FROM AUTHOR]

In this paper, we consider performance analysis of the decentralized power method for the eigendecomposition of the sample covariance matrix based on the averaging consensus protocol. An analytical expression of the second order statistics of the eigenvectors obtained from the decentralized power method, which is required for computing the mean square error (MSE) of subspace-based estimators, is presented. We show that the decentralized power method is not an asymptotically consistent estimator of the eigenvectors of the true measurement covariance matrix unless the averaging consensus protocol is carried out over an infinitely large number of iterations. Moreover, we introduce the decentralized ESPRIT algorithm which yields fully decentralized direction-of-arrival (DOA) estimates. Based on the performance analysis of the decentralized power method, we derive an analytical expression of the MSE of DOA estimators using the decentralized ESPRIT algorithm. The validity of our asymptotic results is demonstrated by simulations. [ABSTRACT FROM PUBLISHER]

The construction of highly incoherent frames, sequences of vectors placed on the unit hyper sphere of a finite dimensional Hilbert space with low correlation between them, has proven very difficult. Algorithms proposed in the past have focused on minimizing the absolute value off-diagonal entries of the Gram matrix of these structures. Recently, a method based on convex optimization that operates directly on the vectors of the frame has been shown to produce promising results. This paper gives a detailed analysis of the optimization problem at the heart of this approach and, based on these insights, proposes a new method that substantially outperforms the initial approach and all current methods in the literature for all types of frames, with low and high redundancy. We give extensive experimental results that show the effectiveness of the proposed method and its application to optimized compressed sensing. [ABSTRACT FROM PUBLISHER]

In this paper, an optimal unbiased finite impulse response (OUFIR) filter is proposed as a linking solution between the unbiased FIR (UFIR) filter and the Kalman filter (KF). We first derive the batch OUFIR estimator to minimize the mean square error (MSE) subject to the unbiasedness constraint and then find its fast iterative form. It is shown that the OUFIR filter is full horizon (FH) and that its estimate converges to the KF estimate by increasing the horizon length N. As a special feature, we note that the FH OUFIR filter operates almost as fast as the KF. Several other critical properties of the OUFIR filter are illustrated based on simulations and practical applications. Similar to the UFIR filter, and contrary to the KF, the OUFIR filter is highly insensitive to the initial conditions. It has much better robustness than KF against temporary model uncertainties. Finally, the OUFIR filter allows for ignoring system noise, which is typically not well known to the engineer. [ABSTRACT FROM PUBLISHER]

This paper aims to address a new class of multiscale coordination control problems for multivehicle systems that are subject to external disturbances. Each vehicle is measured by an independent scale due to the constraints of physical environments. Based on the nearest neighbor-interaction rules, three algorithms of different convergence rates are presented such that the vehicles are guaranteed to achieve consensus on a common quantity for all but of their own scales. Simulation tests are performed to validate the effectiveness and robustness of these consensus algorithms. By introducing a Lyapunov potential function, the consensus analysis is further achieved for the three multiscale algorithms, regardless of them with an exponential, finite-time, or fixed-time convergence rate and in the presence of bounded disturbances. [ABSTRACT FROM PUBLISHER]

This paper presents a compendious summary of power hardware-in-the-loop (PHIL) simulations that are used for designing, analyzing, and testing of electrical power system components. PHIL simulations are an advanced application of real-time simulations that represent novel methods, which conjoin software and hardware testing. This contribution outlines necessary requirements for the implementation of PHIL simulations, which are defined by the nature of the digital real-time simulator, the power amplifier, and the power interface (PI). Fundamental characteristics, such as the input/output systems, PI, interface algorithm, and system stability considerations, are discussed for PHIL setups, in order to illustrate both flexibility and complexity of this compound simulation method. The objective of this work is to elaborate an understandable overview of PHIL simulation for electrical power systems and to constitute a contemporary state-of-the-art status of this research area. [ABSTRACT FROM AUTHOR]

The crosstalk effect is one of the main problems in deep sub-micron designs of high-speed buses. To mitigate the crosstalk effect, there are several types of crosstalk avoidance codes proposed in the literature. In this paper, we are particularly interested in generating forbidden transition codes that do not have opposite transitions on any two adjacent wires. For this, we propose a sequential bit-stuffing algorithm and a parallel bit-stuffing algorithm. For the sequential bit-stuffing algorithm, we perform a worst-case analysis and a probabilistic analysis. We show by both theoretic analysis and simulations that the coding rate of the sequential bit-stuffing encoding scheme is quite close to the Shannon capacity. In particular, for a bus with $n=10$ parallel wires, the difference is only 2.2 percent. Using a Markov chain analysis, we show that the coding rate of the parallel bit-stuffing algorithm is only slightly lower than that of the sequential bit-stuffing algorithm. The implementation complexity of the parallel bit-stuffing algorithm is linear with $n$ . In comparison with the existing forbidden transition codes that use the Fibonacci representation in the literature, our bit-stuffing algorithms not only achieve higher coding rates but also have much lower implementation complexity. [ABSTRACT FROM PUBLISHER]

In blind hyperspectral unmixing (HU), the pure-pixel assumption is well known to be powerful in enabling simple and effective blind HU solutions. However, the pure-pixel assumption is not always satisfied in an exact sense, especially for scenarios where pixels are heavily mixed. In the no-pure-pixel case, a good blind HU approach to consider is the minimum volume enclosing simplex (MVES). Empirical experience has suggested that MVES algorithms can perform well without pure pixels, although it was not totally clear why this is true from a theoretical viewpoint. This paper aims to address the latter issue. We develop an analysis framework wherein the perfect endmember identifiability of MVES is studied under the noiseless case. We prove that MVES is indeed robust against lack of pure pixels, as long as the pixels do not get too heavily mixed and too asymmetrically spread. The theoretical results are supported by numerical simulation results. [ABSTRACT FROM PUBLISHER]

This paper deals with the problem of tracking a moving target by means of a network of geographically dispersed nodes with Doppler sensing, communication, and processing capabilities. The problem is addressed both in a hierarchical setting, i.e., in the presence of a fusion center that can fuse data from all the local nodes, and in a peer-to-peer setting wherein each node (peer) has to locally estimate the target kinematic state only on the grounds of local measurements and of data received from its neighbors. A suitable nonlinear observability decomposition is introduced in order to single out state coordinates that can be fully observed from a single Doppler sensor. Based on such a decomposition, a novel dual-stage filtering approach to distributed Doppler-only tracking is developed. In particular, it is shown how the proposed approach can be adopted both in the presence of a fusion center by means of covariance intersection and in the peer-to-peer case by exploiting consensus algorithms. The effectiveness of the proposed algorithms is evaluated via computer simulations. [ABSTRACT FROM AUTHOR]

Many applications have benefited remarkably from low-dimensional models in the recent decade. The fact that many signals, though high dimensional, are intrinsically low dimensional has given the possibility to recover them stably from a relatively small number of their measurements. For example, in compressed sensing with the standard (synthesis) sparsity prior and in matrix completion, the number of measurements needed is proportional (up to a logarithmic factor) to the signal’s manifold dimension. Recently, a new natural low-dimensional signal model has been proposed: the cosparse analysis prior. In the noiseless case, it is possible to recover signals from this model, using a combinatorial search, from a number of measurements proportional to the signal’s manifold dimension. However, if we ask for stability to noise or an efficient (polynomial complexity) solver, all the existing results demand a number of measurements, which is far removed from the manifold dimension, sometimes far greater. Thus, it is natural to ask whether this gap is a deficiency of the theory and the solvers, or if there exists a real barrier in recovering the cosparse signals by relying only on their manifold dimension. Is there an algorithm which, in the presence of noise, can accurately recover a cosparse signal from a number of measurements proportional to the manifold dimension? In this paper, we prove that there is no such algorithm. Furthermore, we show through the numerical simulations that even in the noiseless case convex relaxations fail when the number of measurements is comparable with the manifold dimension. This gives a practical counterexample to the growing literature on the compressed acquisition of signals based on manifold dimension. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a self-directed adaptive phased array control method using the low-frequency part of the signal for a millimeter-wave wireless personal area network, which can reduce the hardware requirement and power consumption compared with those of the conventional digital beamforming method. The signal from each element antenna of the antenna array is phase shifted and down converted to the baseband and then divided into two paths. The first paths are low-pass filtered to extract the low-frequency part of the signals for beamforming control. The second paths from all antennas are combined in-phase in an analog domain and then sampled by two high-speed A/D converters for demodulation. A beamforming algorithm using the sampled low-frequency part of the signal is also proposed. The beamforming calculation time is established as a function of the signal-to-noise ratio, the bandwidth of the low-frequency part, and the required phase control accuracy. The calculated values match the measured results. Using the IEEE 802.15.3c specifications with an eight-element array antenna, the calculation time is less than \5~\mu\s for initial beam establishment and less than \30~\mu\s for beam tracking. Therefore, high-speed beamforming is possible while reducing the power consumption. [ABSTRACT FROM AUTHOR]

Previous studies on disk scheduling for video services were usually based on computer simulation. We present analysis on disk scheduling for video services. This paper first gives a short review on the various disk scheduling algorithms. It then concentrates on the analysis of two major disk scheduling algorithms, namely, CLOOK and LOOK. The purpose of the analysis is to obtain the maximum number of simultaneous users supported by systems using these two algorithms. The results of the analysis show that the CLOOK algorithm performs slightly better than LOOK algorithm in video applications. Then, this paper discusses disk scheduling for supporting special user functions such as “forward search” and “reverse search”. It is shown that the maximum number of user streams supported drops dramatically when such user functions are used. A technique called redundancy for special user functions (RESUF) is then studied. Analysis of the technique shows that it can keep the I/O demands to almost constant under all user request conditions [ABSTRACT FROM PUBLISHER]

Distributed database systems (DUBS) have received considerable attention in recent years. Being a relatively young research field, there are still many problems associated with DDB systems that need solution. Concurrency control is one of these problems and, probably, the most extensively studied. However, most of the work has concentrated on the development of alternative solutions and the field seems to be ready for some comparative analysis work. This paper reports the results of a performance evaluation study on distributed database concurrency control algorithms. The research has resulted in the development of a formalism, based on Petri nets, for modeling and analysis purposes. The formalism, called the Extended Place/Transition Nets (EPTN), is both descriptively powerful in that it can be used to model various algorithms precisely and succinctly and to communicate them in a clear manner, while at the same time lending itself to be used as a performance evaluation tool. An EPTN simulator is implemented and various algorithms are studied using this tool. This paper describes both the formalism and the performance results that have been obtained. [ABSTRACT FROM AUTHOR]

We describe a successive-cancellation list decoder for polar codes, which is a generalization of the classic successive-cancellation decoder of Arıkan. In the proposed list decoder, $L$ decoding paths are considered concurrently at each decoding stage, where L$ is an integer parameter. At the end of the decoding process, the most likely among the L$ paths is selected as the single codeword at the decoder output. Simulations show that the resulting performance is very close to that of maximum-likelihood decoding, even for moderate values of L$ . Alternatively, if a genie is allowed to pick the transmitted codeword from the list, the results are comparable with the performance of current state-of-the-art LDPC codes. We show that such a genie can be easily implemented using simple CRC precoding. The specific list-decoding algorithm that achieves this performance doubles the number of decoding paths for each information bit, and then uses a pruning procedure to discard all but the L time, which is in stark contrast with the $O(n \log n)$ complexity of the original successive-cancellation decoder. In this paper, we utilize the structure of polar codes along with certain algorithmic transformations in order to overcome this problem: we devise an efficient, numerically stable, implementation of the proposed list decoder that takes only $O(L n \log n)$ time and $O(L n)$ space. [ABSTRACT FROM AUTHOR]

Quadrature compressive sampling (QuadCS) is a recently introduced sub-Nyquist sampling scheme for effective acquisition of inphase and quadrature (I/Q) components of sparse radio frequency signals. In applications to pulse-Doppler radars, the QuadCS outputs can be arranged into a two-dimensional data format, in terms of slow time and virtual fast time, similar to that by Nyquist sampling. This paper develops a compressive sampling pulse-Doppler (CoSaPD) processing scheme which performs Doppler estimation/detection and range estimation from the sub-Nyquist data without recovering the Nyquist samples. The Doppler estimation is realized through a spectrum analyzer as in classical processing, whereas the detection is performed using the Doppler bin data. The range estimation is performed using sparse recovery algorithms only for the detected targets to reduce the computational load. A low detection threshold is used to improve the detection probability and the introduced false targets are then removed in the range estimation stage by exploiting the inherent target detection capability of the recovery algorithms. Simulation results verify the effectiveness of the proposed CoSaPD scheme, which requires only one-eighth of the Nyquist rate to achieve similar performance to the classical processing with Nyquist samples, provided that the input signal-to-noise ratio (SNR) is above ?25 dB. [ABSTRACT FROM AUTHOR]

This paper deals with the estimation of the clutter covariance matrix in airborne radar space-time adaptive processing (STAP). Based on the persymmetry property, a novel STAP method, referred to as persymmetric extended factored processing (Per-EFA), is derived, which can make a more intensive use of the secondary data and improve the STAP performance in training-limited scenarios. Simulation results demonstrate the effectiveness of this method. [ABSTRACT FROM AUTHOR]

In this paper, we study the distributed spectrum sensing in cognitive radio networks. Existing distributed consensus-based fusion algorithms only ensure equal gain combining of local measurements, whose performance may be incomparable to various centralized soft combining schemes. Motivated by this fact, we consider practical channel conditions and link failures, and develop new weighted soft measurement combining without a centralized fusion center. Following the measurement by its energy detector, each secondary user exchanges its own measurement statistics with its local one-hop neighbors, and chooses the information exchanging rate according to the measurement channel condition, e.g., the signal-to-noise ratio (SNR). We rigorously prove the convergence of the new consensus algorithm, and show all secondary users hold the same global decision statistics from the weighted soft measurement combining throughout the network. We also provide distributed optimal weight design under uncorrelated measurement channels. The convergence rate of the consensus iteration is given under the assumption that each communication link has an independent probability to fail, and the upper bound of the iteration number of the $ \epsilon$ -convergence is explicitly given as a function of system parameters. Simulation results show significant improvement of the sensing performance compared to existing consensus-based approaches, and the performance of the distributed weighted design is comparable to the centralized weighted combining scheme. [ABSTRACT FROM PUBLISHER]

This paper deals with the problem of joint complex matrix diagonalization by considering both the Hermitian and transpose congruences. We address the general case where the searched diagonalizing matrix is a priori nonunitary. Based on the minimization of a quadratic criterion, we propose a flexible algorithm in the sense that it allows to directly consider a rectangular diagonalizing matrix and to take into consideration both the Hermitian and transpose congruences within the same framework. The proposed algorithm is a coordinate descent algorithm that is based on an approximate criterion leading to the analytical derivation of the minima arguments. Computer simulations are drawn to illustrate the usefulness and performances of the algorithm and a comparison to state-of-the-art algorithms is presented. Finally, an application to independent component analysis based on fourth-order statistics is also presented. [ABSTRACT FROM PUBLISHER]

This paper focuses on an important query in scientific simulation data analysis: the Spatial Distance Histogram (SDH). The computation time of an SDH query using brute force method is quadratic. Often, such queries are executed continuously over certain time periods, increasing the computation time. We propose highly efficient approximate algorithm to compute SDH over consecutive time periods with provable error bounds. The key idea of our algorithm is to derive statistical distribution of distances from the spatial and temporal characteristics of particles. Upon organizing the data into a Quad-tree based structure, the spatiotemporal characteristics of particles in each node of the tree are acquired to determine the particles’ spatial distribution as well as their temporal locality in consecutive time periods. We report our efforts in implementing and optimizing the above algorithm in graphics processing units (GPUs) as means to further improve the efficiency. The accuracy and efficiency of the proposed algorithm is backed by mathematical analysis and results of extensive experiments using data generated from real simulation studies. [ABSTRACT FROM AUTHOR]