MIMO Techniques in a Visible Light Communication (VLC) Link with Imager

An investigation of MIMO (multiple-input multiple-output) modulation techniques is presented in the context of a short-range Visible Light Communication (VLC) link compatible with the lighting function of common LED-based luminaires. A 2x2 VLC test bench was constructed based on typical low-cost components (white LEDs and photodiodes) and the use of an imaging lens to separate the transmitted streams at the receiver. Two transmission schemes are compared, both based on pulse amplitude modulation (PAM): spatial modulation (SM) and spatial multiplexing (SMP). BER performance is assessed through simulation based on channel characteristics measured on the test bench for both perfect alignment and laterally offset (misaligned) geometries. SMP is found to yield superior BER performance at the same spectral efficiency.