Exit-Chart-Based Design of Irregular Precoded Power-Imbalanced Optical Spatial Modulation

In this paper, we propose a near-capacity irregular precoded power-imbalanced (PI) optical spatial modulation (OSM) scheme. The PI-OSM scheme was developed for negating the effects of high channel correlation, which is often observed in optical wireless communications. In our proposed scheme, multiple PI-OSM subcodes are used to create a novel irregular precoded PI-OSM architecture. This allows us to match the extrinsic information transfer curves of the inner and outer codes in a flexible manner, hence reducing the signal-to-noise ratio required for achieving an infinitesimally low bit error rate (BER). Our numerical simulation results demonstrate that the irregular precoded PI-OSM scheme achieves a high performance, particularly in noise-dominant channels, and it outperforms the repetition-coded benchmark scheme with pulse-amplitude modulation.