Extended Alamouti Space Time Coding Scheme with Turbo Coding for Free Space Optical Communication

An appropriate coding method that can reduce the error rate of communication system is very important to the free space optical communication. Space-Time Block Code (STBC) is an orthogonal encoding method integrating space domain and time domain. This can combat fading effectively and improve error rate performance. In this paper, we have first used an extended Alamouti STBC codes for Pulse Position Modulations (PPM) for an intensity modulation and direct detection (IM/DD) optical communication system. Also, the BER performance of the system is further improved by using Turbo channel coding with the space time codes. The atmosphere channel is described by Gamma-Gamma PDF model. Maximum likelihood (ML) optimal detection technique is used at the receiver side for detection.