Error rate performance for STBC in free-space optical communications through strong atmospheric turbulence

In this letter, error rate performance for space-time block coding (STBC) in free-space optical (FSO) communication systems with direct detection operating over strong atmospheric turbulence channels is analyzed. Based on the modification of the Alamouti code presented by Simon and Vilnrotter, a generalized approach is adopted to consider space-time coded on-off keying (OOK) formats with any pulse shape and reduced duty cycle, allowing the increase of the peak-to-average optical power ratio (PAOPR) and, hence, a relevant improvement in error rate performance. Simulation results are further demonstrated to confirm the analytical results