Differential Dual Amplitude-Width PPM Coding for FSO communication systems

In this paper, a hybrid modulation scheme called DDAWPPM (Differential Dual Amplitude-Width Pulse Position Modulation) suitable with wireless optical systems has been proposed, on the basic of DPPM (Differential Pulse Position Modulation), PAM (Pulse Amplitude Modulation) and PWM (Pulse Width Modulation). The combinations (DPPM-PAM) and (DPPM-PWM) have been proposed in previous works, but the proposed DDAWPPM and beside the symbol synchronization ability, it shows more improvement in term of data rate and spectral efficiency, on the other side it shows a degradation in term of power efficiency. We present theoretical expressions of spectral efficiency, power requirements, and the normalized data rate improvement, and we present comparison results to DPPM and the hybrids PAM-DPPM and PWM-DPPM.