The Uplink Visible Light Communication Beacon System for Universal Traffic Management
This paper presents a feasibility study of the uplink visible light communication (VLC) beacon system for the universal traffic management system (UTMS). The UTMS is a traffic management system beneath the National Police Agency of Japan. Currently, 55 000 UTMS infrared beacon systems have been installed, and they provide expressway and ordinary road information to cars. However, the data rate is 1 Mbps, and a faster data rate is necessary to support automotive and smart mobility devices. In this paper, we propose an uplink V2I system for the UTMS. The system is designed to match the current beacon system as closely as possible, so that the system can easily be replaced and still provide sufficient bandwidth for future automotive and smart mobility devices. We adopt a photo diode (PD) as the VLC receiver and a commercially available off-the-shelf LED headlight as a transmitter. Unfortunately, the bandwidth of such an LED is usually small, so we consider applying a bit-loading algorithm to direct-current-biased optical orthogonal frequency division multiplexing. To reduce strong background noise, such as from the sun, we narrow down the field-of-view by applying a lens to the PD, which forms a tiny communication area, smaller than the current infrared beacon system. We then consider multiple PDs with the lens to create a similar communication area as the infrared beacon system. As a result, we achieve 3.1-Mbps throughput.