Partially Informed Transmitter Based Optical Space Shift Keying under Atmospheric Turbulence

In this work, a partially informed transmitter-based optical space shift keying (PIT-OSSK) scheme is proposed, wherein the transmitter only possesses the knowledge of channel gain ordering. This partial information is used to adapt the OSSK constellation and power allocation (PA). The adaptation of OSSK constellation reduces the number of bits in error between two consecutive constellation points, which in turn lowers the overall bit error rate (BER) of the proposed scheme. On the other hand, it is demonstrated by a mathematical analysis that PA achieves improved diversity order as compared to the conventional OSSK scheme. These modifications make the PIT-OSSK scheme significantly better than the conventional OSSK scheme in terms of BER under both indoor and outdoor conditions. For a single receiver aperture, accurate closed-form expressions of average BER (ABER) for two and four transmitter aperturebased PIT-OSSK schemes are derived under negative-exponential channel model. Moreover, a very tight approximate closed-form expression of ABER for an arbitrary number of transmitter apertures is also developed. All the derived expressions are verified via Monte-Carlo simulations. Furthermore, the proposed strategy is extended and examined for an arbitrary number of receiver apertures by simulation-based results under different channel models.