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- Indoor positioning and intuitive advertising using visible light communicationPublication . Vieira, Manuela; Vieira, Manuel; Louro, Paula; Fantoni, Alessandro; Vieira, PedroThis paper researches the applicability of an intuitive advertising system for large indoor environments using Visible Light Communication (VLC). This VLC based positioning system includes the use of the visible light signal to light the space and to transmit the information for travelers’ positioning and of advertising campaigns in the surroundings. White RGB-LEDs, whose original function is providing illumination, are used as transmitters due to the ability of each individual chip to switch quickly enough to transfer data. This functionality is used for communication where the multiplexed data can be encoded in the emitting light. The light signals emitted by the LEDs positioned in the area of the advertising campaign are interpreted directly by the customers’ receivers. A SiC optical sensor with light filtering and demultiplexing properties receives the modulated signals containing the ID and the geographical position of the LED and other information, demultiplexes and decodes the data and locates the mobile device in the environment. Different layouts are analysed: square and hexagonal meshes are tested, and a 2D localization design, demonstrated by a prototype implementation, is presented. The key differences between both topologies are discussed. For both, the transmitted information, indoor position and motion direction of the customer are determined. The results showed that the LED-aided VLC navigation system enables to determine the position of a mobile target inside the network, to infer the travel direction as a function of time and to interact with information received.
- Redesign of the trajectory within a complex intersection for visible light communication ready connected carsPublication . Vieira, Manuel Augusto; Vieira, Manuela; Louro, Paula; Vieira, PedroTo serve the changing needs of road traffic control, the road space and road structure surrounding an intersection have evolved into complex forms. The redesign of the trajectories, though complex, can be accomplished by the application of methods for navigation, guidance, and combination of expert knowledge of road traffic control of vehicles, using a concept of request/response in a two-way-to-way traffic light-controlled crossroad. The communication between the infrastructures and the vehicles (I2V), between vehicles (V2V), and from the vehicles to the infrastructures (V2I) is performed through visible light communication (VLC) using the street lamps and the traffic signaling to broadcast the information. Vehicle headlamps and taillights are used to transmit data to other vehicles or infrastructures allowing digital safety and data privacy. Data are encoded, modulated, and converted into light signals emitted by the transmitters. Tetra-chromatic white sources are used providing a different data channel for each chip. As receivers and decoders, silicon/carbon wavelength division multiplexer devices, with light filtering properties, are used. The primary objective is to control the arrival of vehicles to an intersection and schedule them to cross at times that minimize delays. A further objective is to allocate delays between left-turns and forward movements, moderating the speed and slot between vehicles traveling in these directions, maintaining a safe distance from one to another. Pedestrians and bicycles are incorporated. A I2V2V2I traffic scenario is established. A phasing traffic flow is developed as a proof of concept. The experimental results confirm the cooperative VLC architecture showing that communication between connected cars is optimized.
- Wayfinding services in crowded buildings through visible lightPublication . Vieira, Manuela; Vieira, Manuel; Louro, Paula; Fantoni, Alessandro; Vieira, PedroThis paper investigates the applicability of an intuitive risk of transmission wayfinding system in public spaces, virtual races, indoor large environments and complex buildings using Visible Light Communication (VLC). Typical scenarios include: finding places, like a particular shop or office, guiding users across different floors, and through elevators and stairs. The system is able to inform the users, in real time, not only of the best route to the desired destination, through a route without clusters of users, but also of crowded places. Data from the sender is encoded, modulated and converted into light signals emitted by the transmitters. Tetra-chromatic white sources are used providing a different data channel for each chip. At the receiver side, the modulated light signal, containing the ID and the 3D geographical position of the transmitter and wayfinding information, is received by a SiC optical sensor with light filtering and demultiplexing properties. Since lighting and wireless data communication is combined, each luminaire for downlink transmission becomes a single cell, in which the optical Access Point (AP) is located in the ceiling and the mobile users are scattered across the overlap discs of each cell, underneath. The light signals emitted by the LEDs are interpreted directly by the receivers of the positioned users. Bidirectional communication is tested. The effect of the location of the Aps is evaluated and a 3D model for the cellular network is analyzed. In order to convert the floorplan to a 3D geometry, a tandem of layers in a orthogonal topology is used, and a 3D localization design, demonstrated by a prototype implementation, is presented. Uplink transmission is implemented, and the 3D best route to navigate through venue is calculated. Buddy wayfinding services are also considered. The results showed that the dynamic VLC navigation system enables to determine the position of a mobile target inside the network, to infer the travel direction along the time, to interact with received information and to optimize the route towards a static or dynamic destination.
- Footprint model in a navigation system based on visible light communicationPublication . Louro, Paula; Vieira, Manuela; Vieira, Manuel; Lima, Mirtes de; Rodrigues, João; Vieira, PedroIndoor navigation is hardly managed by the usual Global Positioning System (GPS) due to the strong attenuation of signals inside the buildings. Alternative based on RF optical, magnetic or acoustic signals can be used. Among the optical technologies, Visible Light Communication (VLC) provides good position accuracy. The proposed system uses commercial RGB white LEDs for the generation of the light, which is simultaneously coded and modulated to transmit information. The receiver includes a multilayered photodetector based on a-SiC:H operating in the visible spectrum. The positioning system includes multiple, identical navigation cells. Inside each cell, the optical pattern defined by the VLC transmitters establishes specific spatial regions assigned each to different optical excitations, which configures the footprint of the navigation cell. Demodulation and decoding procedures of the photocurrent signal measured by the photodetector are used to identify the input optical excitations and enable position recognition inside the cell. The footprint model is characterized using geometrical and optical assumptions, namely the Lambertian model for the LEDs and the evaluation of the channel gain of the VLC link. An algorithm to decode the information is established and the positioning accuracy is discussed. The experimental results confirmed that the proposed VLC architecture is suitable for the intended application.
- Cooperative vehicular communication systems based on visible light communicationPublication . Vieira, Manuel; Vieira, Manuela; Louro, Paula; Vieira, PedroThe use of visible light communication (VLC) in vehicular communication systems for vehicle safety applications is proposed. The system aims to ensure the communication between a LED-based VLC emitter and an on-vehicle VLC receiver. A traffic scenario is established. Vehicle-to-vehicle (V2V) and infrastructure-to-vehicle (12V) communications are analyzed. For the V2V communication study, the emitter was developed based on the vehicle headlights, whereas for the study of 12V communication system, the emitter was built based on streetlights. The VLC receiver is based on amorphous SiC technology and enhances the conditioning of the signal enabling to decode the transmitted information. Receivers are located at the rooftop of the vehicle, for 12V communications, and at the tails for V2V reception. Clusters of emitters, in a square topology, are used in the 12V transmission. The information and the ID code of each emitter in the network are sent simultaneously by modulating the individual chips of the trichromatic white LED. Free space is the transmission medium. An on-off code is used to transmit data. An algorithm to decode the information at the receivers is set. The proposed system was tested. The experimental results confirmed that the proposed cooperative VLC architecture is suitable for the intended applications.
- Trajectory redesign within a complex intersection for VLC ready connected carsPublication . Vieira, Manuel Augusto; Vieira, Manuela; Louro, Paula; Vieira, PedroIn order to serve the changing needs of road traffic control, the road space and road structure surrounding an intersection have evolved into complex forms. Using a new concept of request/response in a two-way-to-way traffic light controlled crossroad, the redesign of the trajectories can be accomplished by the application of methods for navigation, guidance and combination of expert knowledge of vehicle road traffic control. In this work, the communication between the Infrastructures and the Vehicles (I2V), between vehicles (V2V) and from the Vehicles to the Infrastructures (V2I) is performed through Visible Light Communication (VLC), using the street lamps and the traffic signaling to broadcast the information. Vehicle headlamps are used to transmit data to other vehicles or infrastructures, allowing digital safety and data privacy. Data is encoded, modulated and converted into light signals emitted by the transmitters. Tetra-chromatic white sources are used, providing a different data channel for each chip. As receivers and decoders, SiC Wavelength Division Multiplexer (WDM) devices, with light filtering properties, are considered. The primary objective is to control the arrival of vehicles to an intersection and schedule them to cross at times that minimize traffic delay. A further objective is to allocate delays between left-turns and forward movements, moderating the speed and slot between vehicles travelling in these directions, maintaining a safe distance from one to another. Pedestrians and bicycles are also incorporated. An I2V2V2I traffic scenario is proposed, and bidirectional communication between the infrastructure and the vehicles is tested, using the VLC request/response concept. A phasing traffic flow is developed as a proof of concept. The experimental results confirm the cooperative VLC architecture, showing that communication between connected cars and infrastructures can be optimized using the mentioned request/response concept. A significant increase in traffic throughput with the least dependency on infrastructure is achieved.
- Geolocation and communication in unfamiliar indoor environments through visible lightPublication . Vieira, Manuela; Vieira, Manuel; Louro, Paula; Fantoni, Alessandro; Vieira, PedroTo support people’s wayfinding activities in unfamiliar indoor environments, a method able to generate ceiling landmark route instructions using Visible Light Communication (VLC) is proposed. The system is composed of several transmitters (ceiling luminaries) which send the map information and path messages required to wayfinding. Mobile optical receivers, using joint transmission, extracts theirs location to perform positioning and, concomitantly, the transmitted data from each transmitter. Bidirectional communication between the emitters and the receivers is available in strategic optical access point. Typical scenarios are simulated and include finding places and guiding users across different floors. Data from the sender is encoded, modulated and converted into light signals emitted by the transmitters. Tetra-chromatic white sources are used, providing a different data channel for each chip. At the receiver, the modulated light signal, containing the ID and the 3D geographical position of the transmitter and wayfinding information, is received by SiC photodetectors with light filtering and demultiplexing properties. Since lighting and wireless data communication is combined, each luminaire for downlink transmission become a single cell, in which the optical access point (AP) is located. The coded light signals are interpreted directly by the receivers of the users positioned underneath. The effect of the location of the APs is evaluated and a model for the different cellular networks is analyzed. Orthogonal and hexagonal topologies are tested, and a 3D localization design, demonstrated by a prototype is presented. Uplink transmission is implemented and the 3D best route to navigate through venue calculated. The results show that the system make possible to determine the position of a mobile target inside the network, to infer the travel direction along the time and to interact with information received and optimize the route towards a static or dynamic destination.
- Bidirectional data transfer in VLC linksPublication . Louro, Paula; Vieira, Manuela; Vieira, Manuel AugustoVisible Light communication is a data transmission technology that uses the LED lighting infrastructure to simultaneously illuminate and communicate. The ubiquitous existence of LED lamps opened a new opportunity for addressing VLC communication in many indoor communication scenarios. The motivation for the application presented in this paper is the modern, efficient management of warehouses supported by autonomous navigation robots that grab goods and deliver the items at the packaging station. This functionality demands bi-directional communication among infrastructures and vehicles. In this paper we propose links for Infrastructure-To-Vehicle (I2V), Vehicle-ToInfrastructure (V2I) and Vehicle-To-Vehicle (V2V) to perform indoors, bi-directional communication for robot navigation in automated warehouses. In this work it is proposed a bidirectional communication system between a static infrastructure and a mobile robot (I2V). The LED lamps of the warehouse illumination system are used to lighten the space, and to transmit information about position and about racks content. The mobile robots communicate with the infrastructure (V2I) to transmit information on the items that are being removed and carried to the packaging station. The communication among the autonomous robots (V2V) provides information on the number of items intended to be collected when the vehicles are in the same lane, possibly with the purpose of collecting the same items. Different codification schemes are proposed to establish the V2I, I2V and V2V links. Tri-chromatic white LEDs with the red and blue chips modulated at different frequencies and a photodetector based on a-SiC:H/a-Si:H with selective spectral sensitivity are used at the emitter and receiver. Position information is provided by each LED lamp to the autonomous vehicle by adequate modulation of the RGB emitters. The decoding strategy is based on accurate calibration of the output signal. Different scenarios were designed and tested. Requirements related to synchronous transmission and flickering were addressed to enhance the system performance.
- VLC-based geo-localization for automated logistics control using AVGsPublication . Louro, Paula; Rodrigues, João; Vieira, Manuela; Vieira, Manuel Augusto; Vieira, PedroIncreasing interest in indoor navigation has recently been generated by devices with wireless communication capabilities that enabled a wide range of applications and services. The rise of the Internet of Things (IoT) and the inherent end-to end connectivity of billions of devices is very attractive for indoor localization and proximity detection. Other fields, such as, marketing and customer assistance, health services, asset management and tracking, can also benefit from indoor localization. Different techniques and wireless technologies have been proposed for indoor location, as the traditional Global Positioning System (GPS) has a very poor, unreliable performance in a closed space. The work presented in this research proposes the use of an indoor localization system based on Visible Light Communication (VLC) to support the navigation and operational tasks of Autonomous Guided Vehicles (AVG) in an automated warehouse. The research is mainly focused on the development of the navigation VLC system, transmission of control data information and decoding techniques. As part of the communication system, trichromatic white LEDs are used as emitters and a-SiC:H/a-Si:H based photodiodes with selective spectral sensitivity, are used as receivers. Through the modulation of the RGB LEDs, the downlink channel establishes an infrastructure-to-vehicle link (I2V) and provides position information to the vehicle. The decoding strategy is based on accurate calibration of the output signal. Characterization of the transmitters and receivers, description of the coding schemes and decoding algorithms will be the focus of discussion in this paper.
- Optical communication applications based on white LEDsPublication . Louro, Paula; Vieira, Manuel; Vieira, Manuela