Optical spatial modulation with transmitter-receiver alignments

Optical spatial modulation (OSM) is a pulsed modulation technique for indoor optical wireless (OW) communication systems, proposed recently in. In this paper, the performance of OSM is significantly enhanced by proper geometrical alignment of transmit and receive units. In OSM, multiple transmit units are considered where only a single transmit unit is activated at a particular time instance and all others are turned off. The incoming bits are grouped in blocks with length equivalent to the base-two logarithm of the number of transmit units. A block of bits forms a spatial symbol, and the actual transmit units are considered as spatial constellation points. A 4×4 multiple-input multiple-output (MIMO) model inside a room is considered to evaluate the performance of the proposed OSM system. It is shown that the proposed scheme is very efficient in terms of power and bandwidth as compared to on-off keying (OOK), pulse position modulation (PPM), and pulse amplitude modulation (PAM).