Non-DC-biased OFDM with Optical Spatial Modulation

In this paper, a novel optical Orthogonal Frequency Division Multiplexing (OFDM) modulation approach is presented. This method uses the Optical Spatial Modulation (OSM) technique to obtain positive and real-valued signals which are required by an Optical Wireless Communication (OWC) system. In comparison to existing OFDM methods applied to the OSM system, the new scheme, Non-DC-biased OFDM (NDC-OFDM), has significant advantages. Compared to DC-biased Optical OFDM (DCO-OFDM), NDC-OFDM avoids DC-biasing and, thus, improves the power efficiency. Moreover, the spectral and power efficiency of the new approach are better than the well-known unipolar optical modulation scheme, Asymmetrically Clipped Optical OFDM (ACO-OFDM). The bit-error ratio (BER) performances of these three methods are compared. Compared to ACO-OFDM and DCO-OFDM, NDC-OFDM has an energy saving gain of at least 5 dB for the same spectral efficiency. The improvement comes at the expense of additional hardware at the transmitter and receiver. However, visible light communication (VLC) systems typically are equipped with multiple low-cost Light Emitting Diodes (LEDs) to fulfill minimum indoor lighting conditions.