Present-day RF indoor localization systems generally underperform due to multipath propagation. T... more Present-day RF indoor localization systems generally underperform due to multipath propagation. This paper presents a new localization method based on Angle of Arrival estimation and ray tracing. This system exploits the reflections that are generally considered as a burden in conventional systems. In order to design the proposed system, a virtual test bench is created that enables adjusting all parameters. This test bench is then used to evaluate various antenna array elements. Also the Beamscan, MVDR, MUSIC and ESPRIT angle of arrival estimation algorithms are being tested and the effect of spatial smoothing is studied for each of these algorithms. The tests demonstrate that directional microstrip patch antennas result in the best array response for the proposed system and that spatial smoothing is indispensable in multipath environments.
2014 Ubiquitous Positioning Indoor Navigation and Location Based Service (UPINLBS), 2014
ABSTRACT In this paper we intend to find out what resolution can be achieved with two-dimensional... more ABSTRACT In this paper we intend to find out what resolution can be achieved with two-dimensional Angle of Arrival localization when using linear antenna arrays at 2.4 GHz. A theoretical resolution calculation method is presented. Room dimensions, number of cooperating anchor nodes (provided with a linear antenna array) which track the position of a mobile node and number of antenna elements can be chosen. These theoretical calculations lead to the definition of a reference value which can be used to calculate the expected resolution for all rectangular shaped rooms with the desired variable settings. It is also shown that square rooms result in the best resolution and adding extra antenna elements improves the resolution. The design and calibration of a practical linear antenna array, with four linearly positioned 2.4 GHz antenna elements and inter distance of λ/2, is presented. Measurements of practical beam patterns, and the corresponding −3dB beam widths, for different incident angles show that influences such as mutual coupling and reflections can not be neglected. The practical resolutions are compared with expected theoretical values and it is shown that besides I/Q and phase offset calibration, manifold calibration is necessary.
2014 International Conference on Development and Application Systems (DAS), 2014
ABSTRACT In this paper, we describe an experimental evaluation platform, which enables us to obta... more ABSTRACT In this paper, we describe an experimental evaluation platform, which enables us to obtain the performance of baseband modulation techniques for usage in Visible Light Communication (VLC) applications. For the demonstration of the evaluation platform, we have chosen for Manchester encoding. This choice is exemplary, the described system is able to deal with a large set of analog and digital modulation techniques like Non-Return to Zero (NRZ), Return to Zero (RZ), Pulse Position Modulation (PPM), Binary Frequency Shift Keying, Dual Tone Multi-Frequency (DTMF), Phase Shift Keying (PSK), ... For the Manchester encoding, it is experimentally demonstrated that the statistical distribution of the received signal after matched filter operation, is Gaussian in nature. This allows us to make an estimation of the Bit Error Rate (BER) using Q-functions for Gaussian distributions. Our results demonstrate that the estimated BER strongly depends on the sampling rate at the receiver end. The sampling rate will therefor determine whether or not the receiver can receive NonLine Of Side (NLOS) signals at normal light intensities.
IEEE Journal of Biomedical and Health Informatics, 2014
In current healthcare environments, a trend toward mobile and personalized interactions between p... more In current healthcare environments, a trend toward mobile and personalized interactions between people and nurse call systems is strongly noticeable. Therefore, it should be possible to locate patients at all times and in all places throughout the care facility. This paper aims at describing a method by which a mobile node can locate itself indoors, based on signal strength measurements and a minimal amount of yes/no decisions. The algorithm has been developed specifically for use in a healthcare environment. With extensive testing and statistical support, we prove that our algorithm can be used in a healthcare setting with an envisioned level of localization accuracy up to room revel (or region level in a corridor), while avoiding heavy investments since the hardware of an existing nurse call network can be reused. The approach opted for leads to very high scalability, since thousands of mobile nodes can locate themselves. Network timing issues and localization update delays are avoided, which ensures that a patient can receive the needed care in a time and resources efficient way.
2014 IEEE International Conference on RFID (IEEE RFID), 2014
ABSTRACT In this paper, we take an innovative approach to the design of RFID loop antennas. As we... more ABSTRACT In this paper, we take an innovative approach to the design of RFID loop antennas. As we want to increase the reliability of HF RFID systems, we need to step away from the traditional circular antenna shape. Adapting the shape of the antenna to its environment will improve the reliability of the HF RFID systems with a single loop antenna. We compare various shapes to serve as a reader antenna in a metallic tunnel. The optimized loop antennas are created by an antenna design tool which combines MATLAB® and CST EM Studio®. One of the optimized loop antennas is selected to serve in a practical case. Measurements were performed on this practical case with some promising results.
2011 IEEE International Conference on RFID-Technologies and Applications, RFID-TA 2011, 2011
ABSTRACT In spite of the popularity of passive Radio Frequency Identification (RFID) systems, rel... more ABSTRACT In spite of the popularity of passive Radio Frequency Identification (RFID) systems, reliability is an important topic to achieve the adoption of this technology in certain areas of applications. Maintaining this reliability is especially challenging in applications where metals are ubiquitous. This article describes how a passive HF RFID system is optimized for implementation within a closed metal case. The ideal orientation of a transponder within a metal environment is determined. Various simulations were executed in order to predict the areas where the magnetic field exceeded the activation field of the tags. The findings, resulting from these simulations, are verified by hardware measurements which show high prediction accuracy for the practical test setup. In this paper we optimized the reliability of RFID systems by adjusting the radius of a circular loop antenna to the metal construction. In future work, the simulation and measurement tools presented here will be used to evaluate and, eventually automatically generate, optimal antennas with other (non-circular) shapes for different environments.
Advances in Electrical and Computer Engineering, 2009
ABSTRACT This paper presents our research on the influence of metal plates on a radio frequency i... more ABSTRACT This paper presents our research on the influence of metal plates on a radio frequency identification (RFID) loop antenna operating at 13.56MHz. More specific we have tested different types of metal plates near a loop antenna in terms of resonance frequency. The performance of an RFID system strongly depends on the configuration of the antenna. The study shows that the resonance frequency will shift up in a metallic environment, resulting in a failing performance. A solution is presented to avoid the influence of a changing environment around a loop antenna. As an example a loop antenna is designed to prove the increase of stability.
International Conference on Next Generation Mobile Applications, Services, and Technologies, 2011
ABSTRACT Increasing importance of localizing objects in indoor environments is the motivation for... more ABSTRACT Increasing importance of localizing objects in indoor environments is the motivation for many research on localization algorithms. This paper focuses on the maximum achievable resolution for Angle of Arrival as a means to position objects inside rooms using equipment within the field of wireless sensor networks, thus dealing with restricted resources. A clear view on beam forming using antenna arrays is represented and is proven to be useful in Angle of Arrival measurements. The choice of the linear antenna array as most appropriate solution is motivated. A detailed overview of the algorithm, used to calculate the maximum realistic resolution, leads us to draw conclusions concerning the resolution. Depending on the number of anchor nodes and the composition of the antenna arrays, a reference value can be defined to calculate the realistic resolution for all room dimensions.
2013 2nd International Workshop on Optical Wireless Communications (IWOW), 2013
ABSTRACT In this paper, we describe the development of a dedicated transmitter to be used in Visi... more ABSTRACT In this paper, we describe the development of a dedicated transmitter to be used in Visible Light Communication applications. The transmitter has a high power efficiency, so the communication functionality does not lead to significant power consumption. For this reason, a Trans-Conductance Amplifier (TCA) was designed making use of a class AB amplifier. The final design has an electrical bandwidth from 20 kHz until 25 MHz and is able to power LEDs with a driving current up to 700 mA. Results show that the bandwidth of the driver electronics is much larger than the bandwidth of the commonly used power LEDs that are designed for illumination purposes. Because the transmitter has the ability to implement different modulation techniques, as well digital as analogues in nature, it can be used in a wide range of applications depending on the needs of data rate and bandwidth.
Present-day RF indoor localization systems generally underperform due to multipath propagation. T... more Present-day RF indoor localization systems generally underperform due to multipath propagation. This paper presents a new localization method based on Angle of Arrival estimation and ray tracing. This system exploits the reflections that are generally considered as a burden in conventional systems. In order to design the proposed system, a virtual test bench is created that enables adjusting all parameters. This test bench is then used to evaluate various antenna array elements. Also the Beamscan, MVDR, MUSIC and ESPRIT angle of arrival estimation algorithms are being tested and the effect of spatial smoothing is studied for each of these algorithms. The tests demonstrate that directional microstrip patch antennas result in the best array response for the proposed system and that spatial smoothing is indispensable in multipath environments.
2014 Ubiquitous Positioning Indoor Navigation and Location Based Service (UPINLBS), 2014
ABSTRACT In this paper we intend to find out what resolution can be achieved with two-dimensional... more ABSTRACT In this paper we intend to find out what resolution can be achieved with two-dimensional Angle of Arrival localization when using linear antenna arrays at 2.4 GHz. A theoretical resolution calculation method is presented. Room dimensions, number of cooperating anchor nodes (provided with a linear antenna array) which track the position of a mobile node and number of antenna elements can be chosen. These theoretical calculations lead to the definition of a reference value which can be used to calculate the expected resolution for all rectangular shaped rooms with the desired variable settings. It is also shown that square rooms result in the best resolution and adding extra antenna elements improves the resolution. The design and calibration of a practical linear antenna array, with four linearly positioned 2.4 GHz antenna elements and inter distance of λ/2, is presented. Measurements of practical beam patterns, and the corresponding −3dB beam widths, for different incident angles show that influences such as mutual coupling and reflections can not be neglected. The practical resolutions are compared with expected theoretical values and it is shown that besides I/Q and phase offset calibration, manifold calibration is necessary.
2014 International Conference on Development and Application Systems (DAS), 2014
ABSTRACT In this paper, we describe an experimental evaluation platform, which enables us to obta... more ABSTRACT In this paper, we describe an experimental evaluation platform, which enables us to obtain the performance of baseband modulation techniques for usage in Visible Light Communication (VLC) applications. For the demonstration of the evaluation platform, we have chosen for Manchester encoding. This choice is exemplary, the described system is able to deal with a large set of analog and digital modulation techniques like Non-Return to Zero (NRZ), Return to Zero (RZ), Pulse Position Modulation (PPM), Binary Frequency Shift Keying, Dual Tone Multi-Frequency (DTMF), Phase Shift Keying (PSK), ... For the Manchester encoding, it is experimentally demonstrated that the statistical distribution of the received signal after matched filter operation, is Gaussian in nature. This allows us to make an estimation of the Bit Error Rate (BER) using Q-functions for Gaussian distributions. Our results demonstrate that the estimated BER strongly depends on the sampling rate at the receiver end. The sampling rate will therefor determine whether or not the receiver can receive NonLine Of Side (NLOS) signals at normal light intensities.
IEEE Journal of Biomedical and Health Informatics, 2014
In current healthcare environments, a trend toward mobile and personalized interactions between p... more In current healthcare environments, a trend toward mobile and personalized interactions between people and nurse call systems is strongly noticeable. Therefore, it should be possible to locate patients at all times and in all places throughout the care facility. This paper aims at describing a method by which a mobile node can locate itself indoors, based on signal strength measurements and a minimal amount of yes/no decisions. The algorithm has been developed specifically for use in a healthcare environment. With extensive testing and statistical support, we prove that our algorithm can be used in a healthcare setting with an envisioned level of localization accuracy up to room revel (or region level in a corridor), while avoiding heavy investments since the hardware of an existing nurse call network can be reused. The approach opted for leads to very high scalability, since thousands of mobile nodes can locate themselves. Network timing issues and localization update delays are avoided, which ensures that a patient can receive the needed care in a time and resources efficient way.
2014 IEEE International Conference on RFID (IEEE RFID), 2014
ABSTRACT In this paper, we take an innovative approach to the design of RFID loop antennas. As we... more ABSTRACT In this paper, we take an innovative approach to the design of RFID loop antennas. As we want to increase the reliability of HF RFID systems, we need to step away from the traditional circular antenna shape. Adapting the shape of the antenna to its environment will improve the reliability of the HF RFID systems with a single loop antenna. We compare various shapes to serve as a reader antenna in a metallic tunnel. The optimized loop antennas are created by an antenna design tool which combines MATLAB® and CST EM Studio®. One of the optimized loop antennas is selected to serve in a practical case. Measurements were performed on this practical case with some promising results.
2011 IEEE International Conference on RFID-Technologies and Applications, RFID-TA 2011, 2011
ABSTRACT In spite of the popularity of passive Radio Frequency Identification (RFID) systems, rel... more ABSTRACT In spite of the popularity of passive Radio Frequency Identification (RFID) systems, reliability is an important topic to achieve the adoption of this technology in certain areas of applications. Maintaining this reliability is especially challenging in applications where metals are ubiquitous. This article describes how a passive HF RFID system is optimized for implementation within a closed metal case. The ideal orientation of a transponder within a metal environment is determined. Various simulations were executed in order to predict the areas where the magnetic field exceeded the activation field of the tags. The findings, resulting from these simulations, are verified by hardware measurements which show high prediction accuracy for the practical test setup. In this paper we optimized the reliability of RFID systems by adjusting the radius of a circular loop antenna to the metal construction. In future work, the simulation and measurement tools presented here will be used to evaluate and, eventually automatically generate, optimal antennas with other (non-circular) shapes for different environments.
Advances in Electrical and Computer Engineering, 2009
ABSTRACT This paper presents our research on the influence of metal plates on a radio frequency i... more ABSTRACT This paper presents our research on the influence of metal plates on a radio frequency identification (RFID) loop antenna operating at 13.56MHz. More specific we have tested different types of metal plates near a loop antenna in terms of resonance frequency. The performance of an RFID system strongly depends on the configuration of the antenna. The study shows that the resonance frequency will shift up in a metallic environment, resulting in a failing performance. A solution is presented to avoid the influence of a changing environment around a loop antenna. As an example a loop antenna is designed to prove the increase of stability.
International Conference on Next Generation Mobile Applications, Services, and Technologies, 2011
ABSTRACT Increasing importance of localizing objects in indoor environments is the motivation for... more ABSTRACT Increasing importance of localizing objects in indoor environments is the motivation for many research on localization algorithms. This paper focuses on the maximum achievable resolution for Angle of Arrival as a means to position objects inside rooms using equipment within the field of wireless sensor networks, thus dealing with restricted resources. A clear view on beam forming using antenna arrays is represented and is proven to be useful in Angle of Arrival measurements. The choice of the linear antenna array as most appropriate solution is motivated. A detailed overview of the algorithm, used to calculate the maximum realistic resolution, leads us to draw conclusions concerning the resolution. Depending on the number of anchor nodes and the composition of the antenna arrays, a reference value can be defined to calculate the realistic resolution for all room dimensions.
2013 2nd International Workshop on Optical Wireless Communications (IWOW), 2013
ABSTRACT In this paper, we describe the development of a dedicated transmitter to be used in Visi... more ABSTRACT In this paper, we describe the development of a dedicated transmitter to be used in Visible Light Communication applications. The transmitter has a high power efficiency, so the communication functionality does not lead to significant power consumption. For this reason, a Trans-Conductance Amplifier (TCA) was designed making use of a class AB amplifier. The final design has an electrical bandwidth from 20 kHz until 25 MHz and is able to power LEDs with a driving current up to 700 mA. Results show that the bandwidth of the driver electronics is much larger than the bandwidth of the commonly used power LEDs that are designed for illumination purposes. Because the transmitter has the ability to implement different modulation techniques, as well digital as analogues in nature, it can be used in a wide range of applications depending on the needs of data rate and bandwidth.
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Papers by Bart Nauwelaers