3-D-Hierarchical Signalling for Resilient Optical Wireless Communication Systems

Abstract

This paper presents a 3 dimensional (3D)-hierarchical modulation technique for optical wireless communication (OWC) systems in which high, medium and low priority data are encoded on the frequency, phase and amplitude of a subcarrier signal, respectively. The error performance of the 3Dhierarchical modulation is derived and evaluated under different channel conditions. A proof-of-concept experiment is then presented to demonstrate the feasibility of this approach. The results presented in this study show that encoding high and medium priority data on the frequency and phase of a subcarrier signal offers resilience against the deleterious effects of the OWC channel. The amplitude dimension of the subcarrier signal can then be utilised to further increase the system spectral efficiency if the channel conditions allow for it. INDEX TERMS Optical wireless communications (OWC), Underwater optical wireless communications (UOWC), Visible light communication (VLC), free-space optical communication, Modulation schemes, Signalling techniques for OWC