Experimental proof-of-concept of optical spatial modulation OFDM using micro LEDs

This paper investigates experimentally the performance of optical spatial modulation (OSM) with orthogonal frequency division multiplexing (OFDM) in a multiple-input and multiple-output (MIMO) based visible light communication (VLC) system. Gallium nitride based micro light emitting diodes (µLEDs) are considered as a transmitter unit. A two transmitter and two optical receiver based MIMO setup is used. The performance of OSM-OFDM system is experimentally analysed by varying the semi-angle at half power, θ½ of the µLEDs. The optical cross-talk in the MIMO channel is quantified and its effect on the achievable data rate and bit error rate (BER) performance is analysed. The experimental results show that OSM-OFDM achieves higher data rates than single-input and single-output (SISO)-OFDM for all the ranges of θ½ of the µLEDs under study. However, the BER performance of OSM-OFDM is worse than in the case of SISO-OFDM. The maximum achievable data rate in OSM-OFDM is 1.34 Gb/s and 1.17 Gb/s in SISO-OFDM for θ½ of 2.27° at a link distance of 1 m using adaptive data loading. The experimental results also show that due to the strongly correlated channels, the system performance is highly dependent on the θ½ of the µLEDs.