Browsing by Author "Lima, Mirtes de"
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- 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.
- Vehicular visible light communicationin a two-way-two-way traffic light controlled crossroadPublication . Vieira, Manuel; Vieira, Manuela; Louro, Paula; Lima, Mirtes de; Vieira, PedroThe concept of request/response and relative pose estimation for the management of the trajectory is used, in a two-way-two-way traffic lights controlled crossroad, using Vehicular Visible Light Communication (V-VLC). The connected vehicles receive information from the network and interact with each other and with the infrastructure. In parallel, an Intersection Manager (IM) coordinates the crossroad and interacts with the vehicles using the temporal/space relative pose concepts. V-VLC is performed using the street lamps, the traffic signaling and the headlamps to broadcast the information. Data is encoded, modulated and converted into light signals emitted by the transmitters. As receivers and decoders, optical sensors with light filtering properties are used. Cooperative localization is realized in a distributed way with the incorporation of the indirect vehicle-to-vehicle relative pose estimation method. A phasing traffic flow is developed, as Proof of Concept (PoC) and a generic model of cooperative transmission is analysed. Results expresses that the vehicle’s behavior (successive poses) is mainly influenced by the manoeuvre permission and presence of other vehicles.