Power Adjustment Based Congestion Control in Vehicular Ad-hoc Networks

Vehicles exchange periodic beacons to keep track of neighbor´s moving trends in order to achieve cooperative safety awareness. In this paper, beacon rate is fixed as 10Hz to ensure sufficient tracking accuracy. High rate means heavy channel load. If beacons are transmitted with high power, channel will become extremely congested. To alleviate channel congestion, we propose a power adjustment based congestion control method depending on channel condition evaluation and message priority. In our scheme, channel situations are evaluated by current channel load and historical transmission delay. The mechanism is evaluated in our simulation platform which comprises of traffic simulator VISSIM for realistic urban scenario and network simulator NS3 for IEEE 802.11p-based communication. Simulation results demonstrate that our scheme has improved both the system reliability and efficiency.