The Experts below are selected from a list of 11052 Experts worldwide ranked by ideXlab platform
Anthony Rowe - One of the best experts on this subject based on the ideXlab platform.
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IPSN - Demonstration abstract: how many lights do you see?
IPSN-14 Proceedings of the 13th International Symposium on Information Processing in Sensor Networks, 2014Co-Authors: Niranjini Rajagopal, Patrick Lazik, Anthony RoweAbstract:We demonstrate a Visual Light Communication (VLC) system that enables LED lighting luminaires to communicate with cameras on mobile devices. Each LED pulses at a frequency above the humanly perceivable flicker threshold where cameras and photodiodes can still detect changes in light intensity. Our modulation scheme supports multiple light sources in a single Collision Domain, and works for both, line-of-sight (LOS) operation as well as from reflected surfaces like those found in architectural lighting. The spatial confinement of light makes this system ideal for use as localization landmarks. Our demonstration includes four LED ambient lights acting as location landmarks transmitting modulated data. A mobile device receiving and processing the signal displays the ID and RSSI of the closest landmark. Interacting with the system will allow users to see the practical effects of multiple-access, frequency of operation, distance from the lights, camera parameters and camera motion.
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IPSN - Visual light landmarks for mobile devices
IPSN-14 Proceedings of the 13th International Symposium on Information Processing in Sensor Networks, 2014Co-Authors: Niranjini Rajagopal, Patrick Lazik, Anthony RoweAbstract:The omnipresence of indoor lighting makes it an ideal vehicle for pervasive communication with mobile devices. In this paper, we present a communication scheme that enables interior ambient LED lighting systems to send data to mobile devices using either cameras or light sensors. By exploiting rolling shutter camera sensors that are common on tablets, laptops and smartphones, it is possible to detect high-frequency changes in light intensity reflected off of surfaces and in direct line-of-sight of the camera. We present a demodulation approach that allows smartphones to accurately detect frequencies as high as 8kHz with 0.2kHz channel separation. In order to avoid humanly perceivable flicker in the lighting, our system operates at frequencies above 2kHz and compensates for the non-ideal frequency response of standard LED drivers by adjusting the light's duty-cycle. By modulating the PWM signal commonly used to drive LED lighting systems, we are able to encode data that can be used as localization landmarks. We show through experiments how a binary frequency shift keying modulation scheme can be used to transmit data at 1.25 bytes per second (fast enough to send an ID code) from up to 29 unique light sources simultaneously in a single Collision Domain. We also show how tags can demodulate the same signals using a light sensor instead of a camera for low-power applications.
Zdenek Hanzalek - One of the best experts on this subject based on the ideXlab platform.
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zigbee cluster tree formation for time bounded data flows in one Collision Domain
2015 IEEE World Conference on Factory Communication Systems (WFCS), 2015Co-Authors: Aasem Ahmad, Zdenek HanzalekAbstract:We study one-Collision Domain ZigBee cluster-tree design problems to satisfy periodic time-bounded data flows. The formation of the cluster-tree topology can be seen as a bounded-degree-and-depth tree which is an NP-complete problem. The objective is to minimize the number of clusters such that all flows can take place and there exists a cluster schedule that meets the deadlines of the flows. For the resulting tree, the cluster schedule is required to be energy efficient, which can be achieved by maximizing the length of the schedule period, and consequently, increasing the lifetime of the network. We present a Cluster-Tree Formation and Energy-Efficient clusters scheduling algorithm, CFEFS, based on the Hungarian algorithm, the Maximum Matching algorithm and the Branch and Bound algorithm to tackle this design problem that integrates the cluster formation and the cluster scheduling in one problem.
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WFCS - ZigBee cluster tree formation for time-bounded data flows in one Collision Domain
2015 IEEE World Conference on Factory Communication Systems (WFCS), 2015Co-Authors: Aasem Ahmad, Zdenek HanzalekAbstract:We study one-Collision Domain ZigBee cluster-tree design problems to satisfy periodic time-bounded data flows. The formation of the cluster-tree topology can be seen as a bounded-degree-and-depth tree which is an NP-complete problem. The objective is to minimize the number of clusters such that all flows can take place and there exists a cluster schedule that meets the deadlines of the flows. For the resulting tree, the cluster schedule is required to be energy efficient, which can be achieved by maximizing the length of the schedule period, and consequently, increasing the lifetime of the network. We present a Cluster-Tree Formation and Energy-Efficient clusters scheduling algorithm, CFEFS, based on the Hungarian algorithm, the Maximum Matching algorithm and the Branch and Bound algorithm to tackle this design problem that integrates the cluster formation and the cluster scheduling in one problem.
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A polynomial scheduling algorithm for IEEE 802.15. 4/ZigBee cluster tree WSN with one Collision Domain and period crossing constraint
2014Co-Authors: Aasem Ahmad, Zdenek Hanzalek, Claire HanenAbstract:Cluster scheduling is a crucial issue in cluster-tree Wireless Sensor Networks (WSNs). The paper presents a methodology that provides a Time Division Cluster Scheduling (TDCS) mechanism based on the shortest path problem. The objective is to meet all the flows' deadlines defined by the maximum number of crossed periods for each flow to reach its destination assuming one Collision Domain. Formulating the problem as the shortest path problem gives us a light exact algorithm suitable to the scarce properties of WSNs especially related to memory, power consumption and processors. Our polynomial algorithm leads to the minimization of the energy consumption and, consequently, the lifetime of the network is maximized by setting the TDCS period as long as possible. Since each cluster is active only once during the period, the given flow may span over several periods when there are flows with an opposite direction. The scheduling tool enables the system designers to efficiently configure all the required parameters of the IEEE 802.15.4/ZigBee beacon-enabled cluster-tree WSNs in the network configuration time.
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ETFA - A polynomial scheduling algorithm for IEEE 802.15.4/ ZigBee cluster tree WSN with one Collision Domain and period crossing constraint
Proceedings of the 2014 IEEE Emerging Technology and Factory Automation (ETFA), 2014Co-Authors: Aasem Ahmad, Zdenek Hanzalek, Claire HanenAbstract:Cluster scheduling is a crucial issue in cluster-tree Wireless Sensor Networks (WSNs). The paper presents a methodology that provides a Time Division Cluster Scheduling (TDCS) mechanism based on the shortest path problem. The objective is to meet all the flows' deadlines defined by the maximum number of crossed periods for each flow to reach its destination assuming one Collision Domain. Formulating the problem as the shortest path problem gives us a light exact algorithm suitable to the scarce properties of WSNs especially related to memory, power consumption and processors. Our polynomial algorithm leads to the minimization of the energy consumption and, consequently, the lifetime of the network is maximized by setting the TDCS period as long as possible. Since each cluster is active only once during the period, the given flow may span over several periods when there are flows with an opposite direction. The scheduling tool enables the system designers to efficiently configure all the required parameters of the IEEE 802.15.4/ZigBee beacon-enabled cluster-tree WSNs in the network configuration time.
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WFCS - Mixed-criticality scheduling of messages in time-triggered protocols
2014 10th IEEE Workshop on Factory Communication Systems (WFCS 2014), 2014Co-Authors: Zdenek Hanzalek, Tomas TunysAbstract:In different communication protocols, a message retransmission is often used to increase reliability. Messages with higher criticality are allowed for more retransmissions and therefore different execution time values should be specified for each criticality level of the given message. The paper deals with a problem of the static scheduling of mixed-criticality messages on a communication resource (Collision Domain) without preemption. On the basis of the current state of the art in the mixed-criticality scheduling, our problem, denoted as 1|r i , d i , mc =L|βC max + α∑T, is formulated. We use two metaheuristic methods used to solve the mixed-criticality scheduling problem.
Niranjini Rajagopal - One of the best experts on this subject based on the ideXlab platform.
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Visual Light Landmarks for Mobile Devices
2018Co-Authors: Niranjini Rajagopal, Patrick Lazik, Anthony G. RoweAbstract:The omnipresence of indoor lighting makes it an ideal vehicle for pervasive communication with mobiledevices. In this paper, we present a communication scheme that enables interior ambient LED lightingsystems to send data to mobile devices using either cameras or light sensors. By exploiting rolling shutter camera sensors that are common on tablets, laptops and smartphones, it is possible to detect high-frequency changes in light intensity reflected off of surfaces and in direct line-of-sight of the camera. We present a demodulation approach that allows smartphones to accurately detect frequencies as high as 8kHz with 0.2kHz channel separation. In order to avoid humanly perceivable flicker in the lighting, our system operates at frequencies above 2kHz and compensates for the non-ideal frequency response of standard LED drivers by adjusting the light's duty-cycle. By modulating the PWM signal commonly used to drive LED lighting systems, we are able to encode data that can be used as localization landmarks. We show through experiments how a binary frequency shift keying modulation scheme can be used to transmit data at 1.25 bytes per second (fast enough to send an ID code) from up to 29 unique light sources simultaneously in a single Collision Domain. We also show how tags can demodulate the same signals using a light sensor instead of a camera for low-power applications.
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IPSN - Demonstration abstract: how many lights do you see?
IPSN-14 Proceedings of the 13th International Symposium on Information Processing in Sensor Networks, 2014Co-Authors: Niranjini Rajagopal, Patrick Lazik, Anthony RoweAbstract:We demonstrate a Visual Light Communication (VLC) system that enables LED lighting luminaires to communicate with cameras on mobile devices. Each LED pulses at a frequency above the humanly perceivable flicker threshold where cameras and photodiodes can still detect changes in light intensity. Our modulation scheme supports multiple light sources in a single Collision Domain, and works for both, line-of-sight (LOS) operation as well as from reflected surfaces like those found in architectural lighting. The spatial confinement of light makes this system ideal for use as localization landmarks. Our demonstration includes four LED ambient lights acting as location landmarks transmitting modulated data. A mobile device receiving and processing the signal displays the ID and RSSI of the closest landmark. Interacting with the system will allow users to see the practical effects of multiple-access, frequency of operation, distance from the lights, camera parameters and camera motion.
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IPSN - Visual light landmarks for mobile devices
IPSN-14 Proceedings of the 13th International Symposium on Information Processing in Sensor Networks, 2014Co-Authors: Niranjini Rajagopal, Patrick Lazik, Anthony RoweAbstract:The omnipresence of indoor lighting makes it an ideal vehicle for pervasive communication with mobile devices. In this paper, we present a communication scheme that enables interior ambient LED lighting systems to send data to mobile devices using either cameras or light sensors. By exploiting rolling shutter camera sensors that are common on tablets, laptops and smartphones, it is possible to detect high-frequency changes in light intensity reflected off of surfaces and in direct line-of-sight of the camera. We present a demodulation approach that allows smartphones to accurately detect frequencies as high as 8kHz with 0.2kHz channel separation. In order to avoid humanly perceivable flicker in the lighting, our system operates at frequencies above 2kHz and compensates for the non-ideal frequency response of standard LED drivers by adjusting the light's duty-cycle. By modulating the PWM signal commonly used to drive LED lighting systems, we are able to encode data that can be used as localization landmarks. We show through experiments how a binary frequency shift keying modulation scheme can be used to transmit data at 1.25 bytes per second (fast enough to send an ID code) from up to 29 unique light sources simultaneously in a single Collision Domain. We also show how tags can demodulate the same signals using a light sensor instead of a camera for low-power applications.
Aasem Ahmad - One of the best experts on this subject based on the ideXlab platform.
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Distributed Real Time TDMA Scheduling Algorithm for Tree Topology WSNs
IFAC-PapersOnLine, 2017Co-Authors: Aasem Ahmad, Zdeněk HanzálekAbstract:Abstract In this paper, we address the problem of developing TDMA scheduling algorithm for tree topology WSNs. The data transmissions are organized into periodic data flows that may have opposite directions since they are carrying sensor and actuator values for feedback control. It is required to determine a periodic and Collision-free allocation of the time-slots to the sensor nodes such that the end-to-end deadline of each data flow, as given in time units, is satisfied. The objective is to maximize the lifetime of the network by maximizing the time when the nodes are in the sleep mode. However, the longer the time at which the nodes stay in the sleep mode, the harder is to meet the timeliness requirements of the data flows. To solve the TDMA scheduling problem, we have found an elegant approach to express the end-to-end deadline as an integer number of the length of the schedule period. Moreover, since the distributed algorithms, in compassion with the centralized algorithms, well-suit the scarce resources of the WSNs, we focus on the distributed methods that allow each node in the network to come up with its allocated time-slots in the schedule. The proposed algorithm is based on the graph theory algorithms, namely the distributed shortest path and the distributed topological ordering. Furthermore, it falls into the category of the exact algorithms for tree topology with single-Collision Domain and in the category of the heuristic algorithms for multiple-Collision Domains tree topology.
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zigbee cluster tree formation for time bounded data flows in one Collision Domain
2015 IEEE World Conference on Factory Communication Systems (WFCS), 2015Co-Authors: Aasem Ahmad, Zdenek HanzalekAbstract:We study one-Collision Domain ZigBee cluster-tree design problems to satisfy periodic time-bounded data flows. The formation of the cluster-tree topology can be seen as a bounded-degree-and-depth tree which is an NP-complete problem. The objective is to minimize the number of clusters such that all flows can take place and there exists a cluster schedule that meets the deadlines of the flows. For the resulting tree, the cluster schedule is required to be energy efficient, which can be achieved by maximizing the length of the schedule period, and consequently, increasing the lifetime of the network. We present a Cluster-Tree Formation and Energy-Efficient clusters scheduling algorithm, CFEFS, based on the Hungarian algorithm, the Maximum Matching algorithm and the Branch and Bound algorithm to tackle this design problem that integrates the cluster formation and the cluster scheduling in one problem.
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WFCS - ZigBee cluster tree formation for time-bounded data flows in one Collision Domain
2015 IEEE World Conference on Factory Communication Systems (WFCS), 2015Co-Authors: Aasem Ahmad, Zdenek HanzalekAbstract:We study one-Collision Domain ZigBee cluster-tree design problems to satisfy periodic time-bounded data flows. The formation of the cluster-tree topology can be seen as a bounded-degree-and-depth tree which is an NP-complete problem. The objective is to minimize the number of clusters such that all flows can take place and there exists a cluster schedule that meets the deadlines of the flows. For the resulting tree, the cluster schedule is required to be energy efficient, which can be achieved by maximizing the length of the schedule period, and consequently, increasing the lifetime of the network. We present a Cluster-Tree Formation and Energy-Efficient clusters scheduling algorithm, CFEFS, based on the Hungarian algorithm, the Maximum Matching algorithm and the Branch and Bound algorithm to tackle this design problem that integrates the cluster formation and the cluster scheduling in one problem.
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A polynomial scheduling algorithm for IEEE 802.15. 4/ZigBee cluster tree WSN with one Collision Domain and period crossing constraint
2014Co-Authors: Aasem Ahmad, Zdenek Hanzalek, Claire HanenAbstract:Cluster scheduling is a crucial issue in cluster-tree Wireless Sensor Networks (WSNs). The paper presents a methodology that provides a Time Division Cluster Scheduling (TDCS) mechanism based on the shortest path problem. The objective is to meet all the flows' deadlines defined by the maximum number of crossed periods for each flow to reach its destination assuming one Collision Domain. Formulating the problem as the shortest path problem gives us a light exact algorithm suitable to the scarce properties of WSNs especially related to memory, power consumption and processors. Our polynomial algorithm leads to the minimization of the energy consumption and, consequently, the lifetime of the network is maximized by setting the TDCS period as long as possible. Since each cluster is active only once during the period, the given flow may span over several periods when there are flows with an opposite direction. The scheduling tool enables the system designers to efficiently configure all the required parameters of the IEEE 802.15.4/ZigBee beacon-enabled cluster-tree WSNs in the network configuration time.
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ETFA - A polynomial scheduling algorithm for IEEE 802.15.4/ ZigBee cluster tree WSN with one Collision Domain and period crossing constraint
Proceedings of the 2014 IEEE Emerging Technology and Factory Automation (ETFA), 2014Co-Authors: Aasem Ahmad, Zdenek Hanzalek, Claire HanenAbstract:Cluster scheduling is a crucial issue in cluster-tree Wireless Sensor Networks (WSNs). The paper presents a methodology that provides a Time Division Cluster Scheduling (TDCS) mechanism based on the shortest path problem. The objective is to meet all the flows' deadlines defined by the maximum number of crossed periods for each flow to reach its destination assuming one Collision Domain. Formulating the problem as the shortest path problem gives us a light exact algorithm suitable to the scarce properties of WSNs especially related to memory, power consumption and processors. Our polynomial algorithm leads to the minimization of the energy consumption and, consequently, the lifetime of the network is maximized by setting the TDCS period as long as possible. Since each cluster is active only once during the period, the given flow may span over several periods when there are flows with an opposite direction. The scheduling tool enables the system designers to efficiently configure all the required parameters of the IEEE 802.15.4/ZigBee beacon-enabled cluster-tree WSNs in the network configuration time.
Falko Dressler - One of the best experts on this subject based on the ideXlab platform.
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Vehicular Visible Light Communications: A Survey
IEEE Communications Surveys & Tutorials, 2021Co-Authors: Agon Memedi, Falko DresslerAbstract:Visible Light Communications (VLC) is becoming a mature communication technology, particularly for indoor usage. The application in outdoor environments is especially interesting in the scope of Vehicular VLC (V-VLC), however, there are some critical challenges remaining. In general, VLC is a good complement to Radio Frequency (RF)-based communication. For automotive use cases, V-VLC can benefit from the huge available spectrum and the readily available Light Emitting Diode (LED)-based lighting systems of modern cars. Its Line Of Sight (LOS) characteristics, the directionality of the light, and the smaller Collision Domain substantially reduces interference. In this survey article, we study the state of the art of V-VLC and identify open issues and challenges. We study the V-VLC communication system as a whole and also dig into the characteristics of the VLC channel. For the beginner in the field, this review acts as a guide to the most relevant literature to quickly catch up with current trends and achievements. For the expert, we identify open research questions and also introduce the V-VLC research community as a whole.
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WONS - On the need for coordinated access control for vehicular visible light communication
2018 14th Annual Conference on Wireless On-demand Network Systems and Services (WONS), 2018Co-Authors: Agon Memedi, Christoph Sommer, Falko DresslerAbstract:We argue on the need for a dedicated medium access control (MAC) for Vehicular VLC (V-VLC). The huge unlicensed spectrum that can support high throughput applications and the intrinsic security due to the LOS requirement make visible light a viable candidate for use in vehicular communications. In some first research work, the directionality of V-VLC has been considered and an initial conclusion was that the small Collision Domain leads to negligible interference and, thus, dedicated mechanisms for medium access are unnecessary. However, in a more realistic simulation setup using the Luxembourg mobility model, we are able to show that, in certain geographical areas, the number of transmitters seen at a single receiver can easily grow up to 30. Considering packet transmissions, the interference-induced packet loss can be substantial, reaching up to 13 % during rush hours. We thus make the case that this packet loss should be mitigated with a dedicated MAC for coordinated access control in V-VLC.