This paper reports a detailed experimental characterization of optical performances of Visible Light Communication (VLC) system using a real traffic light for ultra-low latency, infrastructure-to-vehicle (I2V) communications for intelligent transportation systems (ITS) protocols. Despite the implementation of long sought ITS protocols poses the crucial need to detail how the features of optical stages influence the overall performances of a VLC system in realistic configurations, such characterization has rarely been addressed at present. We carried out an experimental investigation in a realistic configuration where a regular traffic light (TX), enabled for VLC transmission, sends digital information towards a receiving stage (RX), composed by an optical condenser and a dedicated amplified photodiode stage. We performed a detailed measurements campaign of VLC performances encompassing a broad set of optical condensers, and for TX-RX distances in the range 3 - 50 m, in terms of both effective field of view (EFOV) and packet error rate (PER). The results show several nontrivial behaviors for different lens sets as a function of position on the measurement grid, highlighting critical aspects as well as identifying most suitable optical configurations depending on the specific application and on the required EFOV. In this paper we also provide a theoretical model for both the signal intensity and the EFOV as a function of several parameters, such as distance, RX orientation and focal length of the specific condenser. Our results could be very relevant in the near future to assess a most suited solution in terms of acceptance angle when designing a VLC system for real applications, where angle-dependent misalignment effects play a non-negligible role, and we argue that it could have more general implications with respect to the pristine I2V case mentioned here.

中文翻译：

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用于智能交通系统的超低延迟可见光通信系统的光学特性

本文报告了对可见光通信 (VLC) 系统光学性能的详细实验表征，该系统使用真正的交通灯，用于智能交通系统 (ITS) 协议的超低延迟、基础设施到车辆 (I2V) 通信。尽管长期寻求的 ITS 协议的实施提出了详细说明光学阶段的特征如何在现实配置中影响 VLC 系统的整体性能的关键需求，但目前很少解决此类表征。我们在实际配置中进行了实验研究，其中启用了 VLC 传输的常规交通灯 (TX) 向接收级 (RX) 发送数字信息，接收级 (RX) 由光学聚光器和专用放大光电二极管级组成。我们针对有效视场 (EFOV) 和数据包错误率 (PER) 对 VLC 性能进行了详细的测量活动，包括一系列广泛的光学聚光器，以及 3 - 50 m 范围内的 TX-RX 距离。结果显示了不同镜头组的几种重要行为，作为测量网格上位置的函数，突出了关键方面，并根据特定应用和所需的 EFOV 确定了最合适的光学配置。在本文中，我们还提供了信号强度和 EFOV 作为几个参数的函数的理论模型，例如距离、RX 方向和特定聚光镜的焦距。