A novel trellis coded overlapping amplitude and pulse position modulation scheme for gamma-gamma channel free-space optical communication

A novel trellis coded-4x8 overlapping amplitude and pulse position modulation (TC-4x8AOPPM) scheme is proposed to enhance bit error rate (BER) performance of free-space optical communication (FSO) system. In addition, an uncoded AOPPM referential scheme is also designed. The schemes manage to decrease BER by designing gamma-gamma (GG) channel applicable decoding and demodulation methods. Simulation results of 8, 16 and 64-state TC-4x8AOPPM show 2.5-3.3 dB SNR gain against traditional TC-4x8AOPPM scheme respectively. Thus significant BER performance improvement is achieved and the reliability of the FSO system is also enhanced.