Congestion control by dynamic sharing of bandwidth among vehicles in VANET

The wireless access in vehicular environment system is developed for enhancing the driving safety and comfort of automotive users. However, such system suffers from quality of service degradation for safety applications caused by the channel congestion in scenarios with high vehicle density. The present work is a congestion control mechanism in vehicular ad-hoc network. It supports the communication of safe and unsafe messages among vehicles and infrastructure. Each node maintains a control queue to store the safe messages and a service queue to store the unsafe messages. The control channel is used for the transmission of safe messages and service channel is used for the transmission of unsafe messages. Each node computes its own priority depending upon the number of waiting messages in control queue and service queue. Each node reserves a fraction of control channel and service channel dynamically depending upon the number of waiting messages in its queue. The unsafe messages at a node may also be transmitted using control channel provided the control channel is free and service channel is overloaded which helps to reduce the loss of unsafe message at a node which in turn reduces the congestion level of a node and also improves its quality of service. The available bandwidth is also distributed among the nodes dynamically depending upon their priority. The performance of the proposed scheme is evaluated on the basis of average loss of unsafe message, average delay in safe and unsafe message, storage overhead per node.