An Adaptive Fractionally-spaced Post-equaliser for Photovoltaic-based VLC

Visible light communications systems employing photovoltaic (PV) cells as receivers (Rxs) offer a promising solution in the next generation smart devices. However, PV cells operating in the energy-harvesting mode exhibit low bandwidth, which significantly limits the maximum achievable data rate. In this work, an adaptive fractionally spaced post-equaliser to extend the bandwidth of PV-based Rxs. The system enables real-time adaptation for different PV cell conditions, such as changes in the irradiance, which influence the Rx’s bandwidth, without requiring any hardware modification. The optimal filter coefficients are obtained using the least mean squares and the recursive least squares filters. Algorithms are experimentally validated, and the results are verified using the resulting eye diagram, showing a meaningful improvement in data rate using on-off keying.