Renovating road signs for infrastructure-to-vehicle networking: a visible light backscatter communication and networking approach

Conventional road signs convey very concise and static visual information to human drivers, and bear retroreflective coating for better visibility at night. This paper introduces RetroI2V - a novel infrastructure-to-vehicle (I2V) communication and networking system that renovates conventional road signs to convey additional and dynamic information to vehicles while keeping intact their original functionality. In particular, RetroI2V exploits the retroreflective coating of road signs and establishes visible light backscattering communication (VLBC), and further coordinates multiple concurrent VLBC sessions among road signs and approaching vehicles. RetroI2V features a suite of novel VLBC designs including late-polarization, complementary optical signaling and polarization-based differential reception which are crucial to avoid flickering and achieve long VLBC range, as well as a decentralized MAC protocol that make practical multiple access in highly mobile and transient I2V settings. Experimental results from our prototyped system show that RetroI2V supports up to 101 m communication range and efficient multiple access at scale.