Space-Collaborative Constellation Designs for MIMO Indoor Visible Light Communications

In conventional multi-input multioutput (MIMO) visible light communication (VLC) techniques such as repetition coding (RC), spatial multiplexing (SMP), and spatial modulation (SM), the transmitted symbols through different light-emitting diodes located different space are usually generated from unipolar pulse amplitude modulation constellations independently. In this letter, we propose a novel constellation design for MIMO indoor VLC systems, in which the two symbols from two spaces collaborate so closely that the average optical power is minimized under the constraint that the minimum Euclidean distance is fixed. Therefore, this new constellation is called space-collaborative constellation (CC). Computer simulations show that the CC always has better error performance than SM and SMP, and also has better error performance than RC for most of good channels as well as for some really bad channels.