Challenges and Opportunities of VLC Application in Intelligent Transportation Systems

Introduction

Visible Light Communication (VLC) is a developing wireless communication technology, which uses visible light (380 - 780 nm) for data transmission. It offers significantly greater bandwidth compared to the radio frequency (RF) communications. VLC exploits the low-cost and highly efficient Light-emitting Diodes (LEDs) used for both illumination purposes and wireless communications. LEDs are characterized by numerous advantages, including long lifespan, compact form factor, reduced usage of harmful materials in design and low heat generation even after long period of usage. Another important benefit of LEDs is the capability of switching to different light intensity levels (undetectable to human eyes). Furthermore, VLC is safe for human health and it does not affect the functionality of the sensitive electronic systems. It is also characterized by a high directivity and a predictable channel, which reduces the sources of interference and a high-security level is guaranteed due to the inherently reserved channels. These benefits make VLC a very promising technology for numerous applications. However, the high directivity requires the existence of the Line-of-Sight (LOS), which limits the use of VLC. Relative mobility in establishing communication links between vehicles or between vehicles and infrastructure can disrupt LOS. In addition, natural and artificial light also degrades performances of the VLC systems, especially the sunlight which adds noise and interference in the channel.

VLC enables wireless communications with high data rates wherever there is artificial lighting, indoor and outdoor. Thus, VLC has great potentials in vehicular communication applications. It can easily be incorporated into Intelligent Transportation Systems (ITS). The aim of ITS is to increase safety, the efficiency of the transportation system and to reduce the gasses emissions. Numerous studies show that VLC can satisfy the requirements imposed on vehicular networks. Various modes of vehicular communication can be established: Vehicle-to-Infrastructure (V2I), Vehicle-to-Vehicle (V2V) and Infrastructure-to-Vehicle (I2V). Considering the communications between infrastructure and vehicles, and vice versa, most of the existing systems are oriented towards the communication between LED-based traffic lights or street lighting system and vehicles. The high power of traffic lights allows relatively long communication distances. On the other hand, the short distance between the street light and vehicle, along with the high power implied, assures high data rates and increases the communication stability. Based on the LED lighting systems integrated into vehicles in headlamps, brake lights or signal lights, the VLC communication between vehicles is enabled. Besides communication, VLC enables positioning superior to the Global Positioning System (GPS) with lower costs than existing systems. In this chapter, the comprehensive analysis of VLC technology and applications in ITS are provided. Main characteristics of VLC in ITS in terms of architecture, modulation and standardization are analyzed. Benefits and possible challenges of VLC application in ITS scenarios are also addressed.