Design and Implementation of Distributed Broadcast Algorithm Based on Vehicle Density for VANET Safety-Related Messages

Vehicle ad hoc network (VANET) is a research hotspot in industrial and academic fields now and after. Dedicated short-range communication (DSRC) is a key technology of vehicular safety services and most research adhere to IEEE 802.11p standard. The safety-related services face channel congestion, message collision, and hidden tinal problem in different traffic conditions. This paper focuses on the broadcast of safety-related message under different vehicle densities. In this paper, we firstly divide the safety-related messages into three categories and assign them different broadcast priorities. Secondly, we design different distributed broadcast algorithms for the three type messages. Then,we propose a method used to evaluate the vehicle density and present the relationship between the vehicle density and the transmit power. Then the safety module selects proper transmit power according to the relationship before the message is sent. Finally, we conduct the simulation experiment using NS3 software in the Linux environment. Simulation results show that the broadcast scheme can effectively ensure that the emergency message is correctly received in the 200m range for high vehicle density. Compared with the algorithm without considering the vehicle density, the performance has been greatly improved.