On the Performance of OOK/L-PPM Modulated NOMA Cooperative VLC System With Diversity Combining Techniques Under Imperfect CSI Scenario

Wireless communication systems can become more capable by leveraging new chances for developing challenges by utilizing the Internet of Things (IoT) in sixth-generation (6G) networks. Visible light communication (VLC) exhibits considerable potential as a wireless access protocol for IoT devices (IDs). Nonorthogonal multiple access (NOMA) can be used in IoT applications to handle its massive connectivity requirements when various devices with different communication requirements need to share the same communication resources efficiently. In a more realistic context, when noisy or imperfect channel state information (CSI) is present, this study suggests an ON–OFF keying (OOK)/L-ary pulse position modulation (L-PPM) modulated NOMA cooperative VLC (C-VLC) system capable of connecting IDs to achieve long-range indoor communication. Within the research, three diversity combining strategies, i.e., equal gain combining (EGC), maximum ratio combining (MRC), and selection-based combining, are used and compared for the scheme under discussion. An OOK/L-PPM modulated NOMA cooperative VLC system is examined for bit error probability (BEP) under both perfect and imperfect successive interference cancellation (SIC), taking into consideration imperfect CSI. This assessment compares the outcomes with a conventional orthogonal multiple access technique and focuses on a scenario involving two IDs. To validate the analytical bit error probability (BEP) conclusions, extensive simulations are carried out and compared with the direct transmission.