OCTMAC: A VLC based MAC protocol combining optical CDMA with TDMA for VANETs

Visible Light Communication (VLC) has drawn much interest from telematics and adaptive cruise control system due to its high communication safety and license-free. At present, most researches about VLC Medium Access Control (MAC) protocol are carried out in indoor environments, studies in inter-vehicles communication are less relatively. In this paper, we first present a Vehicle-to-Vehicle (V2V) communication model and then propose a novel MAC protocol in VLC named OCTMAC which combines Time Division Multiple Access (TDMA) with optical Code Division Multiple Access (CDMA) mechanism. Then we analyze the system performance in terms of access delay and network throughput. Finally, the proposed protocol is evaluated with network simulation (NS3) to verify the theoretical analysis on a horizontal and straight road. Simulation results show that the average access delay is 2.75ms when network experiences the worst situation. Also, network throughput is improved by encoding the information with Optical Orthogonal Codes (OOCs).