Optical spatial modulation over Gamma-Gamma turbulence and pointing error induced fading channels

The installations of free space optical (FSO) systems on many structures may account to link availability degradation and poor system performance due to vibration in the transmitted optical beam between the transmitter and the receiver coupled with atmospheric turbulence fading within the channel. In this paper, we study the performance of free space optical spatial modulation system (FSO-SM) under the influence of Gamma-Gamma turbulence channel and misalignment effect. We derived the average bit error rate (ABER) for the system using a power series approach by eliminating the difficulty incur with Meijer-G function adopted in many related researches. The effect of pointing error on the system performance is therefore analyzed under the normalized transmitter beam waist and jitter variance conditions and the numerical results reveal how receive diversity significantly improved the system error rate. It was found that the proposed system outperformed the conventional FSO systems. Furthermore, convolutional coding is employed to enhance the system performance and the study discovered that a very low optical power is required by the system to achieve a minimum error rate.