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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.
- 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.
- Fine-grained indoor localization: optical sensing and detectionPublication . Vieira, Manuela; Vieira, Manuel; Louro, Paula; Vieira, Pedro; Fantoni, AlessandroA LED-assisted navigation system for large indoor environments is proposed. White LEDs are used both for illumination purposes and as transmitters. On-off keying modulation scheme is used to broadcast the information together with the identifiers, IDs, related to the physical location of the transmitters. The mobile receiver is implemented using a double p-i-n/pin SiC photodetector with light controlled filtering properties. Coded multiplexing techniques for supporting communications and navigation concomitantly on the same channel are analysed. Fine-grained indoor localization is demonstrated. Different indoor layouts, using as position technique a four-code assignment for the LEDs, are proposed. Square and hexagon mesh are tested, and a 2D localization design, demonstrated by a prototype implementation, is presented. The key differences between both topologies are discussed. The location and motion information is calculated by position mapping and estimating the location areas along the time. In both topologies, the transmitted data information, indoor position and motion direction of the mobile device are determined. The results showed that the LED-aided VLC navigation system make possible not only to determine the position of a mobile target inside the unit cell but also in the network and concomitantly to infer the travel direction along the time.
- Geo-localization using indoor visible light communicationPublication . Louro, Paula; Vieira, Manuela; Vieira, Pedro; Rodrigues, J.; Lima, M. deNowadays, Global Positioning Systems (GPS) are used everywhere for positioning and navigation. However, its use is not suitable in indoor environment, due to power budget constraints and the strong attenuation inside buildings. Therefore, indoors navigation takes advantage of other technologies to infer position. Recently, several Visible Light Positioning (VLP) systems have been reported. Among these technologies, Visible Light Communication (VLC) is one of the most promising, as its operation is based on the use of LED lights, currently widely used in the illumination solutions of most buildings. In this paper, we propose an indoor navigation system based on VLC in an industrial application for automated warehouses, where the navigation of autonomous vehicles (AVG) is supported by VLC. The proposed VLC system establishes bidirectional communication between the infrastructure and the guided vehicles. LED transmitters at the warehouse ceiling support downlink data transmission from the Infrastructure to Vehicle (I2V). This channel provides positioning and navigation of the vehicles, as well as transmission of dedicated messages related to the requested tasks of the management warehouse system to the autonomous vehicles. The uplink channel from the Vehicle to the Infrastructure (V2I) is used to acknowledge the requested tasks and transmit updates on the concluded tasks. Optical transmitters are tri-chromatic white LEDs with a wide angle beam. The characterization of the optical transmitter system is done through MatLab simulations for path loss and VLC channel gain prediction, using the Lambertian model for the LED light distribution. Dedicated receivers based on a-SiC:H/a-Si:H photodiodes with selective spectral sensitivity are used to record the transmitted signal. The decoding strategy is based on accurate calibration of the output signal.
- Light-emitting diodes aided indoor localization using visible light communication technologyPublication . Vieira, Manuela; Vieira, Manuel; Louro, Paula; Vieira, PedroThis paper focuses on designing and analyzing a visible light-based communication and positioning system for indoor wireless communication under light-emitting diodes (LEDs) lighting environments. The indoor positioning system uses trichromatic white LEDs, both for illumination purposes and as transmitters, and an optical processor, based on a-SiC:H technology, as a mobile receiver. An on–off keying modulation scheme is used, proving a good trade-off between system performance and implementation complexity. The relationship between the transmitted data and the received output levels is decoded. LED bulbs work as transmitters, sending information together with different identifiers, IDs, related to their physical locations. Square and diamond topologies for the unit cell are analyzed, and a two-dimensional localization design, demonstrated by a prototype implementation, is presented. Fine-grained indoor localization is tested. The received signal is used in coded multiplexing techniques for supporting communications and navigation concomitantly on the same channel. The location and motion information are found by mapping the position and estimating the location areas.
- Bi-directional VLC LED-assisted navigation system for large indoor environmentsPublication . Vieira, Manuela; Vieira, Manuel; Louro, Paula; Fantoni, Alessandro; Vieira, PedroIn this paper, a LED-assisted positioning and navigation VLC system is proposed. A VLC scenario for large environments is stablished, the emitters and receivers are characterized and the communication protocol presented. Different layouts are analyzed. 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, motion direction as well as bi-directional communication are determined. The results showed that the LED-aided VLC navigation 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.
- Fine-grained Indoor Localization: Visible Light CommunicationPublication . Vieira, Manuela; Vieira, Manuel Augusto; Louro, Paula; Fantoni, Alessandro; Vieira, PedroAn indoor positioning system where trichromatic white Light Emitting Diodes (LEDs) are used both for illumination proposes and as transmitters and an optical processor, based on a-SiC:H technology, as mobile receiver is presented. On-Off Keying (OOK) modulation scheme is used, and it provides a good trade-off between system performance and implementation complexity. The relationship between the transmitted data and the received digital output levels is decoded. LED bulbs work as transmitters, sending information together with different identifiers, IDs, related to their physical locations. A triangular topology for the unit cell is analysed, and a 2D localization design, demonstrated by a prototype implementation, is presented. Fine-grained indoor localization is tested. The received signal is used in coded multiplexing techniques for supporting communications and navigation concomitantly on the same channel. The location and motion information is found by mapping the position and estimating the location areas.
- On-off keying transmitter design for navigation by visible light communicationPublication . Louro, Paula; Vieira, Manuela; Costa, João; Vieira, ManuelWhite LEDS revolutionized the field of illumination technology mainly due to the energy saving effects. Besides lighting purposes LEDs can also be used in wireless communication systems when integrated in Visible Light Communication (VLC) systems. Indoor positioning for navigation in large buildings is currently under research to overcome the difficulties associated with the use of GPS in such environments. The motivation for this application is also supported by the possibility of taking advantage of an existing lighting and WiFi infrastructure. In this work it is proposed an indoor navigation system based on the use of VLC technology. The proposed system includes trichromatic white LEDs with the red and blue chips modulated at different frequencies and a pinpin photodetector with selective spectral sensitivity. Optoelectronic features of both optical sources and photodetector device are analyzed. The photodetector device consists two pin structures based on a-SiC:H and a-Si:H with geometrical configuration optimized for the detection of short and large wavelengths in the visible range. Its sensitivity is externally tuned by steady state optical bias. The localization algorithm makes use of the Fourier transform to identify the frequencies present in the photocurrent signal and the wavelength filtering properties of the sensor under front and back optical bias to detect the existing red and blue signals. The viability of the system was demonstrated through the implementation of an automatic algorithm to infer the photodetector cardinal direction. A capacitive optoelectronic model supports the experimental results and explains the device operation.
- Visible light communication technology for fine-grained indoor localizationPublication . Vieira, Manuela; Vieira, Manuel; Louro, Paula; Fantoni, Alessandro; Vieira, PedroThis paper focuses on designing and analysing a visible light based communication and positioning system. The indoor positioning system uses trichromatic white Light Emitting Diodes (LEDs), both for illumination purposes and as transmitters, and an optical processor, based on a-SiC: H technology, as mobile receiver. On-Off Keying (OOK) modulation scheme is used, proving a good trade-off between system performance and implementation complexity. In the following, the relationship between the transmitted data and the received output levels is decoded. LED bulbs work as transmitters, sending information together with different identifiers, IDs, related to their physical locations. Square and diamond topologies for the unit cell are analyzed, and a 2D localization design, demonstrated by a prototype implementation, is presented. Fine-grained indoor localization is tested. The received signal is used in coded multiplexing techniques for supporting communications and navigation concomitantly on the same channel. The location and motion information is found by mapping the position and estimating the location areas.
- Positioning and advertising in large indoor environments using visible light communicationPublication . Vieira, Manuela; Vieira, Manuel; Louro, Paula; Vieira, PedroWe investigate 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 signals to light the space and to transmit information for traveler positioning and for advertising campaigns in the surroundings. As transmitters, white RGB-LEDs were used. Although their original function is to provide illumination, due to the ability of each individual chip to switch quickly enough to transfer data, they were used to broadcast information. This functionality is used for communication where multiplexed data can be encoded in the emitting light. The light signals emitted by the LEDs, positioned in the area of an advertising campaign are interpreted directly by the customers’ receivers. A silicon carbide optical sensor with light filtering and demultiplexing properties receives the modulated signals containing the ID, the geographical position of the LED, and other information, and then it demultiplexes and decodes the data and locates the mobile device within the environment. Different layouts are analyzed; square and hexagonal meshes are tested, and a two-dimensional 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 show 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 the received information.