Performance Analysis of Cooperative VLC With L-PPM Modulation and Diversity Combining Strategies Under Perfect and Imperfect CSI for IoT Devices

The rise of digital transformation is driven by the convenience of Internet of Things (IoT) wireless connectivity, facilitating the development of smarter, more interconnected, and efficient solutions across diverse sectors such as smart homes, cities, industrial automation, healthcare, transportation, agriculture, and environmental monitoring. Visible light communication (VLC) emerges as a promising wireless data transmission technique utilizing the visible light spectrum. Integrating VLC with IoT devices (IDs) offers myriad benefits and potential applications. In a practical scenario, this study presents a novel approach for cooperative VLC (C-VLC) systems that use L-ary pulse position modulation (L-PPM) to establish long-range indoor communication across IDs, even in the presence of noisy channel state information (CSI). Three diversity combining procedures, including equal gain combining (EGC), maximum ratio combining (MRC), and selection-based combining (SBC), are employed and compared in the study. The study examines the bit error probability (BEP) of a C-VLC system using L-PPM modulation for IDs under perfect and imperfect CSI conditions for an M-IDs scenario. The BEP of all three diversity combining strategies is computed using extensive simulations and compared to the performance of direct transmission and on-off keying (OOK) C-VLC systems. These comparisons provide empirical support for the analytical BEP findings.