Performance analysis of the imaging receivers using a hemispherical lens for Visible Light Communications

A hemispherical lens is often used in Visible Light Communication (VLC) systems to provide a wide field of view (FOV) and spatial multiplexing gain. Depending on the way of placing the lens, in practice there are generally two kinds of receivers, namely the flat-surface and curved-surface receivers, where the former one uses the flat surface of lens to collect light from the LED while the latter one uses the curved surface. We first derive the channel gain of the single-input single-output (SISO) VLC system with a finite receiving area, and then compare the channel gains of the two receivers in various scenarios. It is shown that the flat-surface receiver could provide a wider FOV than the curved-surface receiver. We further study the performance of two receivers in multiple-input multiple-output (MIMO) VLC systems. Through the BER performance analysis, we find that high spatial multiplexing gain could be achieved by both receivers if the receiving plane is properly located.