International Conference on Broadband Communications for Next Generation Networks and Multimedia Applications, 12 – 14 July 2022
Andreas Weiss, Ziad Salem and Saman Zahiri Rad (research group Smart Connected Lighting, JOANNEUM RESEARCH MATERIALS) presented three oral talks at the CoBCom-2022 conference at Graz University of Technology in the period between 12-14 July 2022.
Andreas Weiss 
Ziad Salem 
Saman Zahiri Rad
Integrated Sensing and Communication in the Visible Spectral Range: A Novel Closed Loop Controller
Authors: Christian Fragner, Andreas P. Weiss, Franz P. Wenzl and Erich Leitgeb
Abstract: In the course of the ongoing process of defining the future communication standard of 6G, one of the main conceptions is that in future the tasks of communication and sensing will be performed in parallel, utilizing the same waveforms and the same hardware, thus forming a so-called Integrated Sensing and Communication (ISAC) system. In this work, we propose the concept of an ISAC system based solely on visible light that performs the task of sensing the rotational position of a cylinder mounted on a servomotor with an average absolute deviation of ~1.2° and the task of forwarding the commands to reach a defined rotational position. The feasibility of the implemented ISAC system is verified by experimental results that demonstrate the applicability of such a visible light based ISAC systems in the era of 6G. Furthermore, we show a simple and effective method to compensate the impacts of additional ambient light on the operation performance.
Visible Light Sensing for Recognising Human Postural Transitions
Authors: Ziad Salem and Andreas Peter Weiss
Abstract: Human activity recognition and monitoring classify signals that are generated from various sensors based on the physical activities a person is performing during his/her daily life. This is useful if a human performs some postural transition activities such as sit-to-stand and stand-to-sit, which are hardly detected accurately by a single sensor. The aim of this study is to explore the possibilities of detecting daily postural transition activities through a novel wearable approach comprising of inertial measurement sensors (IMU) and visible light sensing (VLS) utilizing a single RGB photodiode in an unmodified lighting infrastructure. By employing a low-complex decision tree algorithm, the activity recognition can be achieved in a resourceful way. For enabling our approach to work precisely in changing environments, a K-means clustering algorithm is employed to adapt the parameters of both sit-to-stand and stand-to-sit transition detection. Our approach is validated with different scenarios; representing basic and daily life postural transition activities. The results showed that the approach was able to achieve the tasks accurately, which could not be the case if either IMU sensors or VLS is used alone.
An Optimal Solution for a Human Wrist Rotation Recognition System by Utilizing Visible Light Communication
Authors: Saman Zahiri-Rad, Ziad Salem, Andreas P. Weiss, Erich Leitgeb
Abstract: Wrist-worn devices enable access to essential information and they are suitable for a wide range of applications, such as gesture and activity recognition. Wrist-worn devices require appropriate technologies when used in sensitive areas, overcoming vulnerabilities in regard to security and privacy. In this work, we propose an approach to recognize wrist rotation by utilizing Visible Light Communication (VLC) that is enabled by low-cost LEDs in an indoor environment. In this regard, we address the channel model of a VLC communicating wristband (VLCcw) in terms of the following factors. The directionality and the spectral composition of the light and the corresponding spectral sensitivity and the directional characteristics of the utilized photodiode (PD). We verify our VLCcw from the simulation environment by a small-scale experimental setup. Then, we analyze the system when white and RGBW LEDs are used. In addition, we optimized the VLCcw system by adding more receivers for the purpose of reducing the number of LEDs on VLCcw. Our results show that the proposed approach generates a feasible real-world simulation environment.
EEDAL-LS-2022 Conference, 1 – 3 June 2022
Ziad Salem and Saman Zahiri Rad (research group Smart Connected Lighting, JOANNEUM RESEARCH MATERIALS) attended the International Conference on Energy Efficiency in Domestic & Light Sources and held lectures on the topics “Sit-to-stand and stand-to-sit activities recognition by Visible Light Sensing” as well as “Combining Optical and Electronic simulation models for the assessment of Visible Light Positioning Systems”.
Ziad Salem 
Saman Zahiri Rad
Sit-to-stand and stand-to-sit activities recognition by Visible Light Sensing
Authors: Ziad Salem, Andreas Peter Weiss, Franz Peter Wenzl
Abstract: Monitoring and analyzing the basic human daily life activities will help enhancing the life qualities of both healthy and physically handicapped persons. The recognition of sit-to-stand and stand-to-sit transitions is a complex task due to the intricate movements in such a transition. This work proposes a novel method, for the detection of sit-to-stand and stand-to-sit transitions in addition to walk and no-walk activities. In contrast to previous methods for sit-to-stand and stand-to-sit transition determination, our solution does not require complex time- or frequency-domain based algorithms, but relies on fusing sensor data from an inertial measurement unit and an RGB photodiode that detects the lighting characteristics at different positions of a room. By utilizing a low complex decision tree algorithm the activity recognition can be performed in a resource-efficient way. The applicability of our approach was tested in two different scenarios.
Combining Optical and Electronic simulation models for the assessment of Visible Light Positioning Systems
Authors: Saman Zahiri-Rad, Andreas P. Weiss, Franz P. Weiss, Felix Lichtenegger, Claude Leiner, Christian Sommer, Erich Leitgeb
Abstract: Research activities to establish precise and reliable Indoor Positioning Systems (IPS) have significantly gained momentum in the recent years. Visible Light Positioning (VLP), an approach to establish a positioning system by utilizing the spectrum of the visible light that is emitted from one or multiple light sources and received at a photosensitive device, has shown to be a promising candidate for the fulfillment of this task. Still, despite the huge progress in improving the basic technology, some discrepancies between the achievable accuracies reported in simulation based studies and real world implementations become aware. This is because in the simulations the effects of the electronic components necessary for a real world implementation are often simplified or even not considered at all. In this study, we propose an approach of an electronic receiver design methodology that is combining ray-tracing for the simulation of the optical channel with simulations of electronic circuits in Simulink/Simscape. By interfacing these two domains, a system level assessment of applications in the field of Visible Light Positioning can be realized. In addition, we demonstrate in an exemplary implementation how the electronic design can be optimized utilizing the method of fingerprinting scenarios.
SPIE Photonics Europe, 3 – 7 April 2022
Ziad Salem and Saman Zahiri Rad (research group Smart Connected Lighting, JOANNEUM RESEARCH MATERIALS) as well as Felix Lichtenegger (research group Light and Optical Technologies, JOANNEUM RESEARCH MATERIALS) attended the SPIE Photonics Europe conference (April 3-7, 2022) and held lectures on the topics listed below.
Ziad Salem 
Saman Zahiri Rad
Human activity recognition based on fusing inertial sensors with an optical receiver
Authors: Ziad Salem, Felix Lichtenegger, Andreas P. Weiss, Claude Leiner, Christian Sommer, Franz P. Wenzl
Abstract: The research on Human Activity Recognition (HAR) systems has received high attention due to its importance in high demanding and challenging fields of study such as health care, social science, robotics and artificial intelligence. One of the most prominent approaches is to use Inertial Measurement Unit (IMU) sensors in order to determine what activity a human is making. If complex activities such as sit-down, stand-up, walk-up and walk-down are needed to be recognized, the user needs to wear multiple sensors on his/her body to perform a correct recognition. Such activity recognition will be of high interest if the object’s position is also recognized. For recognizing the activity and location properly, a decent fusion technique between the multiple sources of information is required. In this study, we propose a novel positioning and HAR system based on fusing data from a single IMU device with data from a simulated segmented optical receiver to perform visible light positioning (VLP). We combine real world data collected from the IMU device with optical simulation data generated from a simulated segmented optical receiver in order to distinguish between various complex activities, particularly walk, walk-up and walk-down in addition to determining the position of where the activity is performed. The fusion mechanism does not only improve the accuracy of the activity recognition in comparison to utilizing either IMU or optical data alone, but also enables the system to furthermore retrieve the user’s position in the room. By applying different Machine-learning (ML) algorithms for the assessment of the achievable results, we conduct a comprehensive analysis on which ML method is suitable for our envisioned low-complex HAR and positioning system, which avoids the placement of multiple sensors on the user’s body. Our results show the influence of different segmentation strategies for the novel concept of a segmented optical receiver in combination with an IMU sensor on the accuracy of the activity and position recognition.
Citation: Ziad Salem, Felix Lichtenegger, Andreas P. Weiss, Claude Leiner, Christian Sommer, Franz P. Wenzl, “Human activity recognition based on fusing inertial sensors with an optical receiver”, Proc. SPIE 12139-5, Optical Sensing and Detection VII, SPIE Photonics Europe, Strasbourg, France (03 April 2022).
Compact angle diversity receiver concept for visible light positioning
Authors: Felix Lichtenegger, Claude Leiner, Christian Sommer, Andreas P. Weiss, Andreas Kröpfl, Saman Zahiri-Rad
Abstract: In this work, we investigate a novel angle diversity receiver concept for visible light positioning. The receiver concept, consisting an ultrathin Fresnel lens, embedded in an aperture, mounted on top of a CMOS sensor has been tested and optimized by ray-tracing simulations. This angle-dependent receiver system has the advantage of compact dimensions, a high field-of-view, an off-the-shelf-sensor and relatively high amount of collected light. The origination of the previously calculated Fresnel lens structure is performed by means of grayscale laser lithography. In the presented receiver system, the incoming radiant intensity distribution is converted into an irradiance distribution on the CMOS sensor, where different angles of incidence of incoming light are refracted towards different areas on the CMOS sensor. To verify the optical system experimentally, a prototype of the receiver is placed in a goniometer setup to record images under controlled angles of incidence. Irradiance distributions recorded in the experiment are compared to irradiance distributions obtained by a realistic ray-tracing model. By direct comparison between experiment and simulation, we can verify the optical functionality of the developed optical system of the receiver and investigate the effect of manufacturing imperfections.
Citation: Felix Lichtenegger Claude Leiner , Christian Sommer , Andreas P. Weiss , Andreas Kröpfl , Saman Zahiri-Rad, “Compact angle diversity receiver concept for visible light positioning”, Proc. SPIE 12138-18, Optics, Photonics and Digital Technologies for Imaging Applications VII, SPIE Photonics Europe, Strasbourg, France (06 April 2022).
A combined optical-electronic simulation approach for a comprehensive discussion of the performance of visible light positioning under tunable lighting conditions
Authors: Saman Zahiri-Rad, Felix Lichtenegger, Andreas P. Weiss, Claude Leiner, Christian Sommer, Erich Leitgeb
Abstract: This paper proposes a novel combined optical-electronic simulation in an indoor environment consisting of four luminaires with tunable LEDs of different Correlated Color Temperatures (CCT). This paper investigates the ability to perform Visible Light Positioning (VLP) to identify the receiver positions in such a scenario with tunable LEDs. In this regard, the ray-tracing simulation, generating a list of rays consisting of optical power, CCT, and the corresponding wavelength of each ray, impinging on the receiver’s surface, is combined with the simulation of an electronic receiver with wavelength depending sensitivity in Simulink/Simscape. This configuration allows us to evaluate the impact of tunable CCT on the electronic design, especially regarding optimizing certain parameters. In this work, we show how the number of unique values in an offline-fingerprinting map can be optimized, which is a crucial requirement for indoor positioning utilizing the fingerprinting method. With our outlined solution approach, a system-level tool is formed based on a precise and comprehensive optical-electronic simulation that allows for assessing VLP scenarios.
Citation: Saman Zahiri-Rad, Felix Lichtenegger, Andreas P. Weiss, Claude Leiner, Christian Sommer, Erich Leitgeb, “A combined optical-electronic simulation approach for a comprehensive discussion of the performance of visible light positioning under tunable lighting conditions”, Proc. SPIE 12139-1, Optical Sensing and Detection VII, SPIE Photonics Europe, Strasbourg, France (03 April 2022).
2nd International Symposium on Implementations of Digital Industry and Management of Digital Transformation 2021, November 11th
Assoc. Prof. Dr. Ziad Salem, Senior Scientist at JOANNEUM RESEARCH MATERIALS/SMART CONNECTED LIGHTING, has been invited as a keynote speaker to the 2nd International Symposium on Implementations of Digital Industry and Management of Digital Transformation 2021.
Assoc. Prof. Dr. Salem held a lecture on “I4RC: The Potential of Visible Light Communication, Positioning and Sensing in the Robotics Domain”.
Abstract: The increasing use of white LEDs for indoor environment provides a significant opportunity for generating functionalities beyond illumination, like Visible Light Communication (VLC), Positioning (VLP) and Sensing (VLS). VLC is a paradigm that could revolutionise the future of wireless communication by transmitting the information using high-speed modulation of the visible light spectrum (380–780 nm) emitted from the LED. The same infrastructure needed for VLC, LEDs as transmitters and photodiodes as receivers, can be also used to perform the task of VLP, which favours an accurate indoor positioning using the luminaires as reference points. By an investigation of the light reflected by objects in the room with the help of the photodiodes, common backscatter approaches can be also applied within the visible light spectrum, which is referred to as (backscattered) VLS. VLS has potentials for privacy-keeping approaches towards human activity recognition and the interaction of humans with appliances and objects in a room (e.g., a wall mounted display, computers, doors, windows, etc.). As a further potential application scenario, of VLC, VLP and VLS, an I4RC (Illumination for Robotic Control) approach will be discussed in detail, in which the motion of a robotic arm(rotation direction, speed) can be accurately monitored by VLS simply by equipping the robotic arm with sequences of colored retroreflective foils. This paths the way that simultaneously sensing and communication tasks can be performed with one and the same low-complexity infrastructure, that apart from communication and sensing also could take over the task of the obligatory room lighting. There with, VLS accentuates as an alternative option for industrial and home robot monitoring in combination with VLP and optical wireless communication.
Recent publication
Title: A low-complexity approach for visible light positioning and space-resolved human activity recognition
Authors: Ziad Salem, Andreas Peter Weiss, Franz Peter Wenzl
Conference: Multimodal Sensing and Artificial Intelligence: Technologies and Applications II; 21-25 June 2021
Abstract: Achieving precise information on the position of a subject without changing the luminaire infrastructure is a big challenge in positioning approaches that rely on visible light positioning. Achieving high positioning accuracy on a centimetre scale is done by implementing complex receiver unit designs or adapting the existing luminaries. In this context, we suggest a visible light positioning based approach that can determine the position of a person in certain areas of a room without the need of lighting infrastructure modifications. With this approach, one can identify the position with the help of the existing luminaires for the obligatory room lighting. The receiver, represented by a RGB sensitive photodiode, is positioned in an optimized way in order to support both the positioning task as well as the comfort of the user. Based on received signal strength measurements in the red, green and blue channels, we achieve the positioning task by a segmentation of the room into different areas corresponding to the respective impinging light and by utilizing machine learning clustering. Our results show the influence of different segmentation strategies and parameters on the number and size of the distinguishable areas inside the room. Then, we demonstrate the achievable accuracy of our solution approach in real world experiments. Our results show that such light-based positioning data can be fused with IMU sensor data for recognizing human activity.
Citation: Ziad Salem, Andreas Peter Weiss, and Franz Peter Wenzl “A low-complexity approach for visible light positioning and space-resolved human activity recognition”, Proc. SPIE 11785, Multimodal Sensing and Artificial Intelligence: Technologies and Applications II, 117850H (20 June 2021); https://doi.org/10.1117/12.2593291.
Conference proceedings of SPIE
Title: Spatiotemporal framework for human indoor activity monitoring
Authors: Ziad Salem, Andreas Peter Weiss, Franz Peter Wenzl
Abstract: Recently, indoor activity monitoring of human beings has gained more and more relevance. In particular, the determination of the spatial and temporal context of a user is of utter importance in many applications like monitoring or safety. In this paper, we present a framework that can identify what, where and how long a user is performing a certain activity by the utilization of a low cost and low complex system. Our system only comprises of a single inertial measurement unit and a single RGB sensitive photodiode, with no prerequisite for infrastructural modifications. By using independent decision trees, also the training effort can be kept minimal. Additionally, we verify experimentally the optimal set of features to be used for the framework. Overall, the achieved results are above 90 % in correct determinations of the room the user is in, the activity the user is performing and in which direction the activity is undertaken.
Citation: Ziad Salem, Andreas Peter Weiss, Franz Peter Wenzl, “A spatiotemporal framework for human indoor activity monitoring,” Proc. SPIE 11525, SPIE Future Sensing Technologies, 115251L (8 November 2020); doi: 10.1117/12.2579884
CoBCom – International Conference on Broadband Communications for Next Generation Networks and Multimedia Applications
July 07th – 09th, 2020, Graz, Austria
In the, due to the Corona crisis, only virtually held 3rd CoBCom – International Conference on Broadband Communications for Next Generation Networks and Multimedia Applications 2020 Conference from 07.07.2020 to 09.07.2020, Dr. Andreas Peter Weiss gave a talk with the title “3D Visible Light Positioning of an Angle Diverse Receiver based on Track Analysis”. In this work it is shown, how the position of an angle diverse receiver can be determined by utilizing the visible light spectrum. This technology is also known as Visible Light Positioning (VLP). Especially in rooms with a symmetrical arrangement of the light sources the method of Fingerprinting suffers performance degradation from ambiguous values in the used offline map with this method. In this work it is shown how this problem can be overcome by extending the position estimation algorithm in a way that it does not only take the current received signals into consideration, but to find the position estimation on the analysis of a series of consecutive signals caused by the receivers movements. In his talk, Andreas gave a detailed description of the utilized receiver design, the implemented algorithm and the achieved results.
2nd CISET 2019, 10 – 12 October 2019, Mersin / TURKEY
Dr. Ziad Salem, Senior Scientist at JOANNEUM RESEARCH MATERIALS/SMART CONNECTED LIGHTING, has been invited as a keynote speaker to the symposium “2nd Cilicia International Symposium on Engineering and Technology”.
Dr. Ziad held a lecture on “Visible Light Communication (VLC) and the Innovation ahead for Internet of Things (IoT)”. Transmission of data is one of the most important day-to-day activities in the fast growing world. With the increase in the number of devices, which access the Internet (IoT), the availability of fixed bandwidth makes it much more difficult to enjoy high data transfer rates and to connect a secure network. Visible light communication (VLC), or Light Fidelity (Li-Fi), is a subset of Optical Wireless Communications (OWC) technologies that uses light as medium to deliver high-speed communication in a manner similar to Wi-Fi and complies with the IEEE standard (IEEE 802.15.7). VLC uses visible light between 400 and 800 THz (electromagnetic spectrum 780–375 nm). VLC provides better bandwidth, efficiency, connectivity, security and high speeds. VLC had already implemented in many installations related to Smart Buildings, Smart Cities, Smart Farming, Smart Street lighting, and Automotive. This technology is expected to grow rapidly. “Indoor navigation through visible light communication” provides an easy approach for example “visitors to shopping malls”, “airport terminals” etc. to find their location and navigate their way forward.
BalkanLight Junior 2019, 19 – 21 September 2019, Plovdiv / BULGARIA
From 19. – 21. September the Balkan Lights Junior 2019 conference was held in the Technical University – Sofia, Branch Plovdiv. Participants included researchers, lighting experts and young scientists who were encouraged to share their knowledge on the conference topics. Over 40 papers were presented on this year’s topics, which include light sources, lighting design and photometric studies, lighting control systems, health effects and environmental issues as well as future directions in lighting engineering.
The work presented by Felix Lichtenegger, master student at JOANNEUM RESEARCH MATERIALS, focuses on optical simulation techniques in Visible Light Communication (VLC). Visible Light Communication is a form of Optical Wireless Communication (OWC), which uses light in the visible spectrum of electromagnetic waves for data communication. With ray-tracing based computer simulations it is possible to simulate the illumination of indoor environments as well as the characteristics of data communication with one common simulation tool. The presented paper proposes new simulation strategies for less time-consuming calculations that were developed during his master thesis as part of the SmartLight2Live project. For further information please visit: https://blj2019.nko.bg/
Proceedings of the “BalkanLight Junior 2019”
The proceedings of the “BalkanLight Junior 2019” conference have now been published. Among others, they also contain Felix Lichtenegger´s contribution on “Ray-tracing based channel modeling for the simulation of the performance of visible light communication in an indoor environment“, which can be found here: https://ieeexplore.ieee.org/document/8883669
The full citation is: F. Lichtenegger, C. Leiner, C. Sommer, A. P. Weiss, F. P. Wenzl, Ray-tracing based channel modelling for the simulation of the performance of visible light communication in an indoor environment, Proc. of the Second Balkan Junior Conference on Lighting, Balkan Light Junior, (2019) DOI: 10.1109/BLJ.2019.8883669