Link Characteristics Comparison of Lambertian & Non-Lambertian MIMO-Based 6G Vehicular Visible Light Communications

As one key candidate technology for the 6G internet of vehicles, vehicular visible light communications (VLCs) have received widespread attention and discussion due to their inherent advantages, including broadband, green, security, and ubiquity. In order to improve the quality of vehicular VLC links and extend their coverage, various multiple input multiple output (MIMO) techniques have been actively introduced into the field of vehicular VLC, demonstrating the corresponding performance gain potential. Objectively, the existing research works mentioned above are generally limited to the discussion of MIMO vehicular VLC based on conventional Lambertian light-emitting diode (LED) light sources. Consequently, there is one absence of a targeted study and evaluation of the link configuration-based vehicular non-Lambertian LEDs and the potential non-Lambertian MIMO vehicular VLC. To address the limitations of the aforementioned research and explore the novel spatial dimension for vehicular VLC design, this work attempts to introduce the representative non-Lambertian LED light beams into the typical MIMO vehicular VLC application for constructing novel MIMO vehicular VLC transmission links. The numerical results demonstrate that in 2 × 2 MIMO mode, compared to the benchmark Lambertian vehicular VLC scheme, the proposed typical non-Lambertian NSPW vehicular VLC schemes could provide capacity gains of up to 5.18 bps/Hz and 4.71 bps/Hz for the stop mode, and the traffic mode, respectively. Moreover, this article quantitatively evaluates the impact of the spatial spacing of receiver light beams on the performance of MIMO vehicular VLC and the relevant fundamental characteristics.