Alamouti-Type STBC for Atmospheric Optical Communication Using Coherent Detection

Alamouti-type space-time block coding is studied for optical wireless communication systems using coherent detection over atmospheric turbulence channels. Atmospheric turbulence-induced fading and phase noise are known to impair the performance of coherent optical wireless systems. Two new Alamouti-type space-time coded architectures are proposed to overcome turbulence-induced fading and phase noise from transmitter lasers, receiver local oscillators, and turbulence channels. Their error rate performance is analyzed for a wide range of turbulence conditions. With developed analytical error rate expressions, the usefulness of the proposed Alamouti-type space-time block coding is demonstrated for coherent optical wireless communication systems. Numerical results confirm the performance improvements of the proposed systems over that of single-input-single-output systems.