Gyula Simon

• PhD
• Professor (Full) at Obuda University

The accuracy of passive hyperbolic localization applications using Time Difference of Arrival (TDOA) measurements can be severely compromised in non-line-of-sight (NLOS) situations. Consensus functions have been successfully used to provide robust and accurate location estimates in such challenging situations. In this paper, a fast branch-and-bound...

A fast Hough transform (HT)-based hyperbolic emitter localization system is proposed to process time difference of arrival (TDOA) measurements. The position-fixing problem is provided for cases where the source is known to be on a given plane (i.e., the elevation of the source is known), while the sensors can be deployed anywhere in the three-dimen...

Simple flooding algorithms are widely used in ad hoc sensor networks either for information dissemination or as building blocks of more sophisticated routing protocols. In this paper a percolation driven probabilistic flooding algorithm is proposed, which provides large message delivery ratio with small number of sent messages, compared to traditio...

Exposure time is a fundamental parameter for the photographer when the photo is composed, and the exact length of the exposure may be an essential determinant of performance in certain camera-based applications, e.g., optical camera communication (OCC) systems. There can be several reasons to measure the shutter speed of a camera: shutter speed may...

This article presents a novel method to measure the exposure time of digital cameras. The measurement relies on a sequence of images taken by the camera in video mode, using the effect of equivalent sampling. The hardware requirements of the proposed method are low: a signal generator drives an LED source and the blinking LED is recorded by the cam...

This book is a printed edition of the Special Issue Recent Advances in Indoor Localization Systems and Technologies that was published in Applied Sciences

Despite the enormous technical progress seen in the past few years, the maturity of indoor localization technologies has not yet reached the level of GNSS solutions. The 23 selected papers in this special issue present recent advances and new developments in indoor localization systems and technologies, proposing novel or improved methods with incr...

Recently, an observer-based algorithm was reviewed that is able to perform recursive sliding discrete Fourier transform (SDFT) [1]. DFT is the basic algorithm used for Fourier analysis [2], but it provides unbiased estimates only if the sampling is coherent, i.e., the ratio of the sampling frequency f <sub xmlns:mml="http://www.w3.org/1998/Math/Mat...

An inexpensive bearing estimation sensor and a corresponding method has been recently proposed for indoor localization applications. The system utilizes modulated infrared LED sources as light beacons, and a planar circular photodiode array (PCPA) as sensor. The PCPA measures the light intensity of the beacons in multiple channels, from which the b...

Several industrial indoor positioning systems utilize LEDs as beacons and cameras as sensors: The LED beacons transmit their identity, using various means of visible light communication (VLC) techniques. To avoid flickering effects, the transmission frequency is usually much higher than the sampling frequency of ordinary cameras, thus undersampling...

Performance analysis of the Undersampled Frequency Shift ON-OFF Keying (UFSOOK) protocol, frequently used in visible light communication, is provided. Data transmission is modelled as a measurement process, and the analysis of the underlying measurement channel and the possible error sources reveals important performance properties of the protocol...

This paper proposes a novel object tracking method using radio interferometry. The proposed low cost solution is able to track objects, equipped with a radio receiver, in real time, using only simple infrastructure nodes with radio transceivers at fixed and known locations. The localization method has low computational requirements and does not req...

As a step towards sustainable energy management systems, energy providers use various demand side management techniques to reduce fluctuations in consumer energy demand. Dynamic pricing schemes encourage consumers to shift their energy usage patterns from peak hours towards off-peak periods, but here usually the active participation of consumers is...

Emergent smart energy distribution systems offer new approaches in the sustainable management of energy consumption, even at household level. The smart grid and smart house paradigms provide the necessary infrastructure to improve the efficiency of the distribution system and at the same time offer benefits for the consumers, too. In this paper the...

A novel indoor localization system is presented, where LED beacons are utilized to determine the position of the target sensor, including a camera, an inclinometer, and a magnetometer. The beacons, which can be a part of the existing lighting infrastructure, transmit their identifiers for long distances using visible light communication techniques....

A novel radio-interferometric measurement method for tracking applications is proposed. Fixed radio transceiver nodes are used to generate interferometric signals, allowing the tracking of a moving object equipped with a radio receiver. Low-frequency phase measurements of the interferometric signals are processed by the proposed simultaneous phase...

A new sensor fusion is proposed for radio-interferometric tracking applications. The proposed solution utilizes fixed infrastructure nodes equipped with simple radio transceivers, generating interferometric signals, which allows the tracking of moving objects equipped with similar radios. The proposed solution utilizes redundant low-frequency phase...

An intrusion detection system was developed to detect illegal entries to guarded forest areas and thus help the prevention of timber theft and other damages, caused by illegal activities. The system contains accelerometers, magnetometers and geophones to provide high detection reliability and fast reaction time. The performance of the proposed syst...

Phase difference measurement of interfering radio signals is an essential part of radio-interferometric positioning applications. In this paper a novel phase measurement system is proposed, which is able to accurately measure the phase difference of the received radio signals, even in the presence of significant measurement noise. The suggested mea...

Home refrigerators produce a substantial part of the annual power consumption in an average household. To further improve the efficiency of these devices, new intelligent control solutions are required. These solutions necessitate the behaviour modeling of the refrigerators. We seek models with as simple structure as possible, since future intellig...

A sensor fusion algorithm is proposed, which can be used to fuse measurements from a distributed sensor network, containing inexpensive, easily deployable and energy efficient magnetic sensor devices. The sensor measurements are collected and transferred to a central base station, where the sensor fusion is performed, using the sensor location. The...

A scheduling algorithm will be proposed for wireless ring topology networks, utilizing time division multiple access (TDMA) with possible simultaneous operation of nodes. The proposed algorithm finds the optimal schedule to minimize the turnaround time for messages in the network. The properties of the algorithm are mathematically analyzed and prov...

In this paper a novel robust radio-interferometric object tracking method is proposed. The system contains fixed infrastructure transmitter nodes generating interference signals, the phases of which are measured by the tracked receivers and other fixed infrastructure nodes. From the measured phase values a confidence map is computed, which is used...

In this paper a novel sensor is proposed, which can be applied both to intrusion detection or tamper detection purposes. The device senses vibrations caused by the attacker, using MEMS accelerometers, to provide alarm signals. The sensor uses low duty cycling operation to conserve its energy, thus it is suitable for wireless applications. The perfo...

In this paper, an adaptive, autocovariance-based event detection algorithm is proposed, which can be used with micro-electro-mechanical systems (MEMS) accelerometer sensors to build inexpensive and power efficient event detectors. The algorithm works well with low signal-to-noise ratio input signals, and its computational complexity is very low, al...

In this paper a low-power communication protocol is proposed for sensor networks, where sensors mostly send measurements and rarely receive commands. The proposed protocol optimizes energy utilization on sensor nodes by using a modified MAC-layer, with acknowledgment frames piggy-backing meta-information towards sensor nodes. The proposed method is...

In this paper a special ring topology is investigated for sensor networks, where the whole network is decomposed into subnetworks forming rings, and these subnetworks are connected to each other through a main ring. Each of these subnetworks may have different requirements concerning message delivery times. In this paper algorithms are proposed, wh...

Wireless Sensor Networks (WSNs) are widely used to perform measurement and monitoring tasks in large sensing fields. Several applications require every point in the monitored area to be covered by at least k sensors (k-coverage problem) for measurement accuracy or robustness. In heterogeneous multi-functional sensor networks, p parallel observation...

In this paper an autocovariance-based event de-tector algorithm is proposed. The algorithm is able to detect events even if the measurements have poor signal-to-noise ratio, and its performance is independent of the characteristic of the input signal. An efficient implementation of the algorithm is also proposed, which allows the utilization of the...

In this paper a TDMA based routing scheme is proposed for such wireless sensor networks, where nodes form multiple connected cycles. The proposed method provides fault tolerance, guaranteed delivery times, and low power consumption. The paper discusses the routing scheme and its implementation details, and provides several performance tests.

An inexpensive, non-intrusive, energy-efficient magnetic sensor-based solution is proposed, which is able to detect vehicles and estimate their speed. In this paper the measurement algorithm is described in detail, which contains an adaptive auto-offset algorithm, a power-based detector and a correlation-based speed estimator. The performance of th...

In this paper a fault-tolerant energy-efficient Time Division Multiple Access (TDMA) based routing scheme is proposed for wireless sensor networks. The proposed system provides guaranteed delivery times and tolerates node and link failures. The software architecture and the performance properties of the system are described.

TDMA-based medium access protocols provide energy efficient and real-time solutions for various sensor networking applications. In this paper an extension is suggested for static TDMA networks, providing connection of mobile nodes to the autonomous TDMA network, with very low overhead. The solution is suitable for applications where mobility is occ...

In this paper a fault-tolerant ring topology is suggested to provide energy efficient and real time operation using Time Division Multiple Access (TDMA) in sensor networks. The fault tolerant behaviour requires search for an extended type of Hamiltonian cycle in the connectivity graph. Since the problem in general is NP-complete, heuristics based u...

Time synchronization is one of the fundamental middleware services in sensor networks, enabling the creation of low duty cycle, power efficient applications. One of the major goals of time synchronization is to enable efficient communication between mostly sleeping devices. The actual requirements and solutions of time synchronization depend on the...

Time synchronization services are often required to support coordinated operation of the nodes in sensor networking applications, potentially containing hundreds or thousands of elements. The synchronization service must provide application-specific performance (in terms of accuracy and overhead), and must be scalable and robust. For the design of...

In this paper a wireless distributed building safety and security framework will be introduced. The main design goals of the system are completely distributed operation, flexibil-ity, robustness, fast response time, and energy efficiency. The framework uses low duty cycle TDMA-based communication scheme, where the scheduling is the result of optimi...

A reconfigurable sensor-networking architecture is proposed, which is constructed from lightweight functional elements running on small virtual machines. The proposed architecture provides a flexible measurement framework that is easily adaptable to changing system requirements in run-time. The system is based on Communicating Sequential Processes...

Sensor networks, constructed from a large number of inexpensive devices can be used to provide accurate and robust acoustic localization services. A consistency-based fusion method, which can be utilized for Time Difference of Arrival (TDOA) measurements has recently been proposed. The fusion algorithm is able to find the global optimum with good a...

Sensor networks have proven their usefulness in various acoustic localization applications. Recently, a consistency-function-based algorithm has been proposed, which can provide accurate solutions even if a large number of independent outliers are present in a measurement set. In certain practical cases, e.g., in non-line-of-sight reverberant areas...

Sensor networks are built from tiny, resource limited nodes, which are able to communicate with each other, and thus, provide distributed services. The quality of communication, and especially of routing, is one of the major enablers of good performance, energy efficiency, and longevity in resource-deprived sensor networks. Since the advent of wire...

Time synchronization services are often required to support coordinated operation of the nodes in sensor networking applications, potentially containing hundreds or thousands of elements. The synchronization service must provide application-specific performance (in terms of accuracy and overhead), and must be scalable and robust. For the design of...

A reconfigurable sensor-networking architecture constructed from lightweight functional elements, running on small virtual machines in parallel is proposed. The proposed architecture provides a flexible measurement system that is easily adaptable to changing system requirements in run-time. It is based on Communicating Sequential Processes and thus...

Sensor networks have proved their usefulness in various acoustic localization applications. Recently a consistency function-based algorithm was proposed, which can provide accurate solution even if a large number of independent outliers are present in the measurement set. In certain practical cases, however, sensors may have cooperative and consist...

Simple flooding algorithms are widely used in ad hoc sensor networks either for information dissemination or as building blocks of more sophisticated routing protocols. In this paper a percolation driven probabilistic flooding algo-rithm is proposed, which provides large message delivery ratio with small number of sent messages, compared to traditi...

As advanced security systems become more and more complex as they handle various sources ofinformation in an integrated manner, traditional approaches for tailoring these systems to the actual applicationdomain become impractical and unfeasible. To help the construction of powerful integrated security systems arule-base support is proposed, which i...

Flooding algorithms are widely used in ad-hoc sensor networks, especially as building blocks of more sophisticated routing protocols. A distributed percolation-driven energy efficient probabilistic flood routing algorithm is proposed, which provides large message delivery ratio with small number of sent messages, using neighborhood information only...

Robustness, fault tolerance, and long lifetime are key requirements of sensor networks used in real-world applications. Dense sensor networks with high sensor redundancy offer the possibility of redundant sensing and low duty-cycle operation at the same time, thus the required robust sensing services can be provided along with elongated lifetime. I...

The paper describes a target tracking system running on a heterogeneous sensor network (HSN) and presents results gathered from a realistic deployment. The system fuses audio direction of arrival data from mote class devices and object detection measurements from embedded PCs equipped with cameras. The acoustic sensor nodes perform beamforming and...

A completely automatic identification system is described which uses the latest results of the frequency domain identification approach to provide an easy-to-use and reliable tool to the inexperienced users. The proposed system accepts periodic measurement data and performs the whole identification procedure automatically from the data-preprocessin...

This paper presents the robustness and performance analysis of the Controlled Greedy Sleep algorithm, which was designed to provide k-coverage in wireless sensor networks. The aim of this algorithm is to prolong network lifetime while ensuring QoS requirements in a dynamic manner. We investigated how the network can be strenghtened to improve perfo...

A diverse set of sensors and actuators are key components of integrated security systems, which provide protection against various types of attacks and threats. Based on the type of the protected objects and environment the sensor/actuator components can be completely different, and the control logic, which makes decision based on the sensor readin...

Redundant sensing capabilities are often required in sensor network applications due to various reasons, e.g. robustness, fault tolerance, or increased accuracy. At the same time high sensor redundancy offers the possibility of increasing network lifetime by scheduling sleep intervals for some sensors and still providing continuous service with hel...

Redundant sensing capabilities are often required in sensor network applications due to various reasons, e.g. robustness, fault tolerance, or increased accuracy. At the same time high sensor redundancy offers the possibility of increasing network lifetime by scheduling sleep intervals for some sensors and still providing continuous service with hel...

A new acoustic localization scheme is proposed, which can be applied in sensor networks with low communication bandwidth. The first step of the two-stage algorithm is distributed and is evaluated at the sensors having possibly low communication capabilities. The sensors detect various events in the acoustic signal and transmit only the event descri...

An ad-hoc wireless sensor network-based system is presented that detects and accurately locates shooters even in urban environments. The localization accuracy of the system in open terrain is competitive with that of existing centralized countersniper systems. However, the presented sensor network-based solution surpasses the traditional approach b...

Experiences developing a sensor network-based acoustic shooter localization system are presented. The system is able to localize the position of a shooter and the trajectory of the projectile using observed acoustic events, such as the muzzle blast and the ballistic shockwave. The network consists of a large number of cheap sensors communicating th...

A nonparametric identification method for linear systems is proposed. The identification is done via synchronized multisine measurements where the synchronization is ensured by a resonator-based generator-observer pair. The advantage of the proposed structure is that it works as a filter bank and, hence, provides the measurement results online. Exp...

IntroductionFACT ArchitectureModeling Hybrid Systems and ControllersThe Hybrid ObserverApproaches to Fault Detection and IsolationController SelectionConclusion and Future WorkReferences

Experiences developing a sensor network-based acoustic shooter localization system are presented. The system is able to localize the position of a shooter and the trajectory of the projectile using observed acoustic events, such as the muzzle blast and the ballistic shockwave. The network consists of a large number of cheap sensors communicating th...

Embedded systems are often modeled using Matlab's Simulink and Stateflow (MSS), to simulate plant and controller behavior but these models lack support for formal verification. On the other hand verification techniques and tools do exist for models based on the notion of Hybrid Automata (HA) but there are no tools that can convert Simulink/Stateflo...

An ad-hoc wireless sensor network-based system is presented that detects and accurately locates shooters even in urban environments. The system consists of a large number of cheap sensors communicating through an ad-hoc wireless network, thus it is capable of tolerating multiple sensor failures, provides good coverage and high accuracy, and is capa...

Wireless sensor network applications, similarly to other distributed systems, often require a scalable time synchronization service enabling data consistency and coordination. This paper describes the Flooding Time Synchronization Protocol (FTSP), especially tailored for applications requiring stringent precision on resource limited wireless platfo...

Complex control applications require capabilities for accommodating faults in the controlled plant. Fault accommodation involves the detection and isolation of faults, and then taking appropriate control actions to mitigate the fault effects and maintain control. This requires the integration of fault diagnostics with control in a feedback loop. Th...

Detecting and accurately locating snipers has been an elusive goal of the armed forces and law enforcement agencies for a long time. Most successful sniper-detecting systems are based on acoustic measurements. We develop an acoustic system that works well even in complex urban environments. Funded through the Network Embedded Systems Technology pro...

The possibility of establishing the chronology of events in a widely distributed network, or even stronger, the clock synchronization of all nodes in the network is often needed for applications of wireless sensor networks (WSN). In this paper we describe the Flooding Time Synchronization Protocol (FTSP) that provides clock synchronization service...

An approach for automatically testing GUIs in the MATLAB environment has been proposed. We developed a software tool that tests GUIs by simulating the user through an action recorder. We proposed a heuristic test procedure: providing random input to GUI, but guiding the randomness with predefined weights assigned to the user controls. The weights c...

The authors explain how to implement a graphical user interface and automatic procedures for easier identification and modeling.

The Frequency Domain System Identification Toolbox for MATLAB is an ef-fective tool for the identification of linear dynamic system models from measured data. Since the use of advanced system identification methods often requires a lot of program-ming work, the attention can be deflected from the modelling issues. Therefore, a Graphi-cal User Inter...

In this paper, we propose a method that allows to make a fully automated spectral analysis of a periodic signal, including a noise analysis, without any user interaction. The only action required from the user is to provide a data record that contains more than two periods of the signal (no integer number of periods is required). No synchronization...

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The AI model-based diagnosis community has developed qualitative reasoning mechanisms for fault isolation in dynamic systems. Their emphasis has been on the fault isolation algorithms, and little attention has been paid to robust online detection and symbol generation that are essential components of a complete di- agnostic solution. This paper dis...

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The design of reliable, dynamic, fault-tolerant services in wireless sensor networks is a big challenge and a hot research topic. In this paper an optimization method is proposed that can be used to tune parameters of the middleware services and applications to provide optimal performance. The optimization method is based on simulation, and is capa...

Self-adaptive software is a technology that allows building fault-adaptive control systems: control software that can survive faults in the system under control, and in the control software itself. This form of self-adaptive software requires capabilities for the detection and isolation of faults when the system is in operation, and then taking app...

Self-adaptive software systems use observations of their own behavior, and that of their environment, to select and enact adaptations in accordance with some objective(s). This adaptation is a higher-level system function that performs optimizations, manages faults, or otherwise supports achieving an objective via changes in the running system. In...

This paper presents a new nonlinear least-squares algorithm for fitting band-limited periodic signals with unknown frequency and harmonic content. The new solution features a model-based recursive calculation method that requires less memory space and has smaller computational demand than the known matrix-based algorithms.

This report investigates the transient phenomena due to run-time reconfigurations in controlled systems. It is shown that in the case of dynamic systems these reconfiguration transients might be reduced to a considerable extent using dedicated design-time and/or run-time methods. The methodology behind applies the so-called model-integrated approac...

Fault adaptive systems must adapt and reconfigure themselves to the changes in the environment or the system itself, and have to maintain operation even in case of system failures. In order to avoid performance degradation due to system reconfigurations, adequate reconfiguration management is necessary. This paper describes a fault-adaptive control...

This paper presents a new nonlinear least-squares algorithm for fitting band-limited periodic signals with unknown frequency and harmonic content. The new solution features a model-based recursive calculation method that requires less memory space and has smaller computational demand than the known matrix-based algorithms

In this paper we propose a method that allows to make a fully automized spectral analysis of a periodic signal, including a noise analysis, without any user interaction. The only action required from the user is to provide a data record that contains more than 2 periods of the signal (no integer number of periods is required). No synchronization be...

Complex control applications require a capability for accommodating faults in the controlled plant. Fault accommodation involves the detection and isolation of faults, and taking an appropriate control action that mitigates the effect of the faults and maintains control. This requires the integration of fault diagnostics with control, in a feedback...

Self-adaptive software systems use observations of their own behavior, and that of their environment, to select and enact adaptations in accordance with some objective(s). This adaptation is a higher-level system function that performs optimizations, manages faults, or otherwise supports achieving an objective via changes in the running system. In...

System reconfiguration at run time may cause unacceptable transients. In this paper, a new design methodology is proposed for reducing transients due to reconfiguration in recursive digital signal processing (DSP) systems. The technique utilizes the fact that, 1) transfer functions can be realized by different processing structures, and 2) these al...