Adaptive SPAD-based Receiver for Dimmable Visible Light Communication

Visible light communication (VLC) is an emerging mode of wireless communication that supports both illumination and communication. Dimming control is one essential function for such systems that requires a sensitive receiver for low-light conditions. The use of an array of single-photon avalanche diodes (SPADs) is one promising approach to enhancing receivers' sensitivity in a VLC system. However, an increase in the light brightness can impair the performance of SPAD-based receivers due to non-linear effects caused by the SPAD dead time. In this paper, an adaptive SPAD receiver is proposed to ensure reliable operation at a wide dynamic range of channel conditions and different dimming levels. In the proposed receiver, a variable optical attenuator (VOA) is used to optimize the SPAD's incident photon rate at each channel condition. Two dimming control methods of IEEE 802.15.7 standard based on analog and digital dimming for on-off keying (OOK) modulation are studied and compared for the proposed SPAD-based VLC system. Our detailed performance investigation shows that the proposed adaptive receiver outperforms traditional PIN PD and non-adaptive SPAD array receivers in terms of the bit error rate (BER) performance. Moreover, the considered analog dimming can provide a significantly higher achievable data rate compared to that of digital dimming at the expense of lower power efficiency.