Performance evaluation of different Pulse Position Modulation schemes in atmospheric turbulence channel for ground-to-satellite optical communication

The atmosphere affects the ground-to-satellite optical link characteristics. In Free Space Optical (FSO) communication it is important to minimize these atmospheric effects, so that efficient communication can take place. In this research paper different modulation schemes as such Pulse Position Modulation (PPM), Differential Pulse Position Modulation (DPPM) and Differential Amplitude Pulse Position Modulation (DAPPM) have been evaluated for atmospheric turbulence channel. It has been observed that DPPM and DAPPM are better bandwidth and power efficient in comparison to conventional modulation schemes OOK and PPM. So they can perform better in atmospheric turbulence channel. In our research paper these modulation schemes have been discussed and then the comparison of bit error rate performance of these modulation schemes has been made for ideal channel without any turbulence and for a practical channel with varying levels of turbulence. Two models log-normal and negative exponential channel model have been used to create weak and strong turbulence conditions. The BER performance with respect to SNR has been compared for PPM, DPPM and DAPPM for ground-to-satellite link.