Multi-User Connectivity: Advanced User Grouping in RF/VLC Systems with SLIPT for Cooperative NOMA Networks

Simultaneous light information and power transfer (SLIPT) enabled non-orthogonal multiple access (NOMA) based radio frequency (RF)/visible light communication (VLC) systems are considered a viable option for indoor wireless systems as they provide a higher data rate with higher energy efficiency. In this work, a grouping algorithm for a dual-hop cooperative NOMA-based multi-user RF/VLC system is introduced. The system consists of a light-emitting diode (LED) source, multiple VLC users randomly distributed inside the coverage area of the LED, and RF users located outside the coverage area of the LED. In grouping, all the VLC users are assigned as near users (NUs) and all the RF users are assigned as far users (FUs). In the first phase of the communication, the NU of a group decodes both its own information and the information of the group's FUs from the alternating current (AC) component of the received NOMA-coded optical signal. Also, it harvests the energy from the direct current (DC) component of the received NOMA-coded optical signal. In the second phase, the NU forward signal of FUs of the same group as NOMA coded RF signal by solely using harvested energy in the first phase. We propose a grouping algorithm by considering either the users' channel gain or signal-to-interference-plus-noise ratio (SINR) as a grouping parameter. Then, we obtained the achievable rate of the NUs and FUs. The presented numerical results demonstrate the effectiveness of the proposed grouping algorithm for the cooperative NOMA-based RF/VLC system with SLIPT capabilities.