On the dynamic vehicular VLC systems employing AF relay node and multiple access techniques

This paper presents a novel approach to Vehicular Visible Light Communication (VVLC) systems by combining Amplify-and-Forward (AF) relay nodes with Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA) techniques within a Direct Current biased Optical Orthogonal Frequency Division Multiplexing framework. The key contribution lies in the innovative integration of AF relays with FDMA and TDMA, offering significant advantages over traditional VVLC systems. Specifically, this combination extends communication range, optimizes resource allocation, and enhances data throughput in dynamic vehicular environments, addressing challenges such as line-of-sight dependency and performance degradation under high mobility. The proposed framework incorporates adaptive bit-loading to efficiently utilize available bandwidth and maximize spectral efficiency. Additionally, this work introduces a dynamic VVLC channel model based on the Weibull distribution, accurately capturing the impact of variable vehicle speeds and real-world mobility patterns on system performance. Our model provides a more realistic representation of vehicular environments compared to static channel models used in previous studies. The proposed system achieves a target Bit Error Rate of 10–3 at a bit energy-to-noise ratio (Eb/N0) of 16 dB with AF relay assistance in high-traffic scenarios using 16-QAM modulation, compared to 19 dB without it. Furthermore, the integration of AF relays with TDMA and adaptive bit-loading achieves a remarkable spectral efficiency of 30.99 b/s/Hz for 64-QAM, significantly outperforming traditional methods. These findings highlight the superior performance of the proposed system in terms of reliability, scalability, and efficiency, making it a promising solution for future 5G/6G vehicular networks and intelligent transportation systems.