A novel low density parity check coded differential amplitude and pulse position modulation free-space optical system for turbulent channel

Based on the proposed partly equidifferent mapping and its specific Differential Amplitude and Pulse Position Modulation (DAPPM) demodulation, a modified FSO scheme for turbulent channel is designed and analyzed. The novel Low Density Parity Check (LDPC) coded 4×4 and 4×8 DAPPM Free-Space Optical communication (FSO) system is constructed. The Monte Carlo simulation results show approximately 2dB transmit power reduction against classical LD-PC-DAPPM at the identical Bit-Error-Rate in strong turbulent channel. The proposed partly equidifferent mapping is compatible with other modulations, so it enables widespread adoption in other coded FSO systems.