Turbo-DC-FPSK: A Joint Turbo Coding and FPSK Based Modulation Scheme Adapted to Optical Wireless Communications

This letter proposes and analyzes a flexible and energy efficient technique for Optical Wireless Communication (OWC) systems. It involves the Direct Current - Frequency and Phase Shift Keying (DC-FPSK) modulation combined with a very low complexity convolutional code in a parallel scheme at the transmitter side, and a turbo-decoder at the receiver side, i.e. Bahl, Cocke, Jelinek and Raviv (BCJR) algorithm. It is an adaptation of the coplanar turbo-FSK technique developed for the long range low power Radio-Frequency (RF) context to the OWC requirements, to be compatible with Intensity-Modulation Direct Detection (IM-DD) techniques (real positive base-band waveforms including a Direct Current (DC) component instead of complex waveforms). Simulation results show that turbo-Dc-fpsk can achieve around 5 dB energy gain over regular OWC state-of-the-art DC-FPSK modulation at a BER
$=10^{-A}$
. Using the number of linear modulation states as degrees of freedom, a flexibility in the desired balance between energy efficiency and spectral efficiency is achieved.