Visible light communication (VLC) allows the dual use of lighting and wireless communication systems by modulation of illumination devices. However, to increase the performance, typically, beam-forming measures are taken creating pencil beams, thus contradicting the illumination purpose. In order to optimize the performance trade off between efficient illumination and communication, the switching capabilities of illumination LEDs are examined. Illumination LEDs with standard drivers and without beam-forming show limited applicability for communication purposes as they are not optimized for the necessary switching capability (f ≈11 MHz) and coherence. Methods to enhance the electrical current by pre-equalisation, biasing, carrier sweeping and current shaping are examined in respect to the illumination LED's communication performance. A novel driver scheme is derived which achieves considerably higher switching frequencies (f ≥100 MHz) without employing beamforming at the illumination LED. This driver is able to obtain a data rate of up to 200 Mbit/s at a distance of 3.2 m, using on-off keying (OOK) modulation technique. Therefore, it is feasible to apply the LED driver by implementing standardised illumination devices in VLC systems.
Today radio based wireless communication technologies offer limited performance, whereas optical wireless com- munication systems (OWC) propose potentially a high performant, scalable communication system conforming to real time conditions. However, current studies imply, that OWCs still lack the necessary performance and robustness level for most wireless applications in industrial production environments. In this approach several types of noises for free-space optical communication systems are empirically analysed in an accredited, exemplary industrial production environment. While the channel noise is usually modelled by the signal to noise ratio it is found that real environments cannot be approximated by the usual static additive white gaussian noise. In this approach the accumulated measurement data represents the spectrum variation of different locations and times relating to different types of noise sources. The implementation in a total channel model allows the optimization of OWC designs like the channel access scheme or the modulation type concerning performance and robustness. Furthermore an additional measurement setup is proposed, capable of measuring and classifying existing noise sources in order to serve the design of OWC systems in industrial production environments.
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