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The convergence of wireless optical communication (WOC) and radio-frequency (RF) systems is a promising technology that overcomes the shortcomings of standalone communication systems. By incorporating reconfigurable intelligent surfaces (RISs) on top of these WOC and RF communication systems, it is possible to circumvent the connection challenges associated with standard line of sight (LOS) communication links. Wireless communication systems with RIS assistance are a promising and evolving technology that enables more efficient and reliable link performance over long distances. The performance of the triple-hop RIS-assisted RF-FSO convergent with the underwater wireless optical communication (UWOC) system is investigated in this article. We considered the fading channel Nakagami-m over the RIS-RF connection and the fading channel Gamma-Gamma (GG) over the RIS-FSO and UWOC links. Then, the average bit error rate (ABER) and outage probability are determined using closed-form expressions. The ABER and outage probability performances of the triple-hop communication system is analysed by varying parameters such as turbulence, misalignment fading, and the number of RIS elements. The obtained results demonstrate an improvement in performance for low turbulence, low pointing error, and an increasing number of RIS elements. Additionally, the data demonstrate the accuracy of the analytical results.

Visible light communication (VLC) is considered a new technology for interconnecting devices in 5G and beyond. VLC can provide additional bandwidth for communicating devices which can help to reduce the radio frequency bandwidth congestion. In this work, we aim to maximize the bandwidth usages for VLC. The proposed modulation technique can impose more bits due to the combined utilization of both pulse height and width changes. Moreover, we subdivide the single bit duration to impose more bits for data transmission. The proposed modulation is capable of transmitting more bits by utilizing fewer optical pulses than other traditional modulation techniques such as multilevel modulation, on-off keying, pulse width modulation, pulse position modulation, pulse amplitude modulation, and multiple pulse position modulation. We have evaluated the theoretical bit error rate (BER) expression in terms of average signal to noise ratio and compared the experimental BER performance for the proposed system. The experimental results demonstrate that the proposed modulation technique can achieve a communication distance of 3 m in an indoor environment.

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