Demonstration of an Adaptive Fractionally-Spaced Pre-Equaliser to Increase VLC System Data Rates

This paper demonstrates a VLC system using an adaptive fractionally-spaced pre-equaliser to extend the modulation bandwidth of the light-emitting diodes (LEDs). The proposed system has the flexibility of compensating for different LEDs by reloading the digital adaptive equaliser’s coefficients without introducing any modification to the hardware. The key enabling power to obtain the optimal equaliser coefficients is from the well-known least mean square (LMS) algorithm. As a by-product, the proposed method offers a novel angle and a method to determine the pre-equaliser coefficients for those systems which do not have the updating algorithm implemented in a real-time manner but have to rely on a stored pre-set coefficient list. Finally, the experimental validation clearly shows the effectiveness of the proposed scheme by means of the improvement in the received eye diagrams.