BER Performance Analysis for M-ary PPM over Gamma-Gamma Atmospheric Turbulence Channels

Atmospheric turbulence induced fading is one of the main impairments affecting the operation of free-space optical (FSO) communication systems. In this paper, the average bit error rate (BER) of M-ary pulse position modulation (PPM) is analyzed under Gamma-Gamma fading channel. Using the characteristics of Meijer G function, Closed-form expression for average BER is derived. The investigation of how the BER performance is affected by the atmospheric conditions and other parameters such as the operational wavelength and the modulation level is made. It is shown that the influence of the turbulence on the short-wavelength is more serious than the long-wavelength. Another important result in this work is that, increasing of modulation level cannot significantly reduce the transmitted power required to achieve a desired BER in moderate-to-strong turbulence channels for M-ary PPM, which is different from the situation in the non-turbulent channel.