Study on Performance of Bit-Interleaved Coded M-PPM in Wireless Optical Communications

A novel transmission scheme of bit-interleaved coded M-ary pulse-position modulation (M-PPM) in free-space wireless optical communications is proposed. The detection method and performance of bit-interleaved coded M-PPM system in atmosphere turbulence channels are studied. The maximum a posterior detection is used to calculate the bit metric information at the receiver in bit-interleaved coded M-PPM system. The bit metric information is used to soft-decision decode in Viterbi decoder. Comparing with the conventional detection and hard-decision decoding, the maximum a posterior detection and soft-decision decoding can improve the performance of coded M-PPM systems in the atmosphere turbulence channels. The numerical simulation results of bit-interleaved coded M-PPM systems in the atmosphere turbulence channels with Rayleigh fading and log-normal fading show that the bit-interleaved coded M-PPM is efficient.