LDPC coded FSO communication system under strong turbulent condition

Atmospheric turbulence-induced fading is one of the main impairments affecting free-space optics (FSO) communications. To design a high-performance communication link for the atmospheric FSO channel, it is of great importance to characterize the channel from the perspective of information and coding theory. In this paper, we consider FSO multiple-input multiple-output (MIMO) channel with Q-ary pulse position modulation (QPPM) and transmit repetition under the assumption of non-ideal photodetection is analyzed in terms of its ergodic channel capacity. Instead of using a simple binary channel code, we suggest using low density parity-check (LDPC) code to perform iterative soft demodulation (demapping) and channel decoding at the receiver. The simulation results confirm the analytical findings of this paper.