Overlapping Signals Separation for Two Light Sources Based on Mode-Mixed PD Arrays

Multipath causes interferences to the optical receivers, and reduces the accuracy of visible light positioning (VLP). The existing works mainly focused on the simulation analysis of the signal responses incurred by the scattering of the indoor surfaces, or the positioning error caused by the multipath in the VLP systems. However, such works can only provide insights for how the multipath propagation affects the VLP systems, but cannot separate and exploit the multipath components. In this paper, we design a mode-mixed photodiode (PD) array to receive the overlapping signals of two light sources. The light sources can be light-emitting diodes (LEDs) or reflectors. Based on the diversity of the PDs, we propose an algorithm to separate the signals from the two light sources, which can estimate the directions and the powers of the light sources. Based on the analytical and simulation results, we show that the two light sources can be separated at the receiver without consuming extra time or frequency resources. Moreover, we can distinguish the line-of-sight component even though the received signal has been distorted by interferences from another light source or a reflecting wall, and improve the localization accuracy of the PD array.