Modulation precoding for MISO visible light communications

Indoor Visible Light Communication is recognized as a viable and smart solution to provide both illumination and wireless connectivity by conveniently modulating optical signals generated by Light Emitting Diodes. When dealing with multiple independent sources, the communication reliability is tied to the capability of separating signals. Such task is typically accomplished by realizing Multiple-Input Multiple-Output architectures, with efficient spatial equalization affordable thanks to the presence of several photodetectors equipping the receiver. On the other hand, dealing with reliability issue, it becomes very challenging in Multiple-Input Single-Output scenarios where channels spatial correlation may severely impact on the communication performance. In this context, we propose a modulation precoding scheme aiming to maximize the minimum distance between received signal power levels at the receiver thus lowering the symbol error probability. To do so, channel state information is required at the transmit side. At the same time, the solution offered by the presented scheme guarantees the lighting constraints, explicitly requested in terms of received optical power, to be met as well.