Research On Backoff Algorithm In MAC Protocol For Vehicle Ad Hoc Network

At present, the rapid development of auto industry, road traffic accidents and other traffic safety problems emerge in endlessly, Vehicle Ad Hoc Network is in this situation arises at the historic moment. In order to improve the road traffic safety and traffic efficiency, VANET applied wireless self-organizing network technology to vehicle communication, this is good for the Intelligent transportation System development, which reduce traffic accidents, has much important significance.Based on the Binary an Exponential Backoff algorithm,we studied Reverse back- off mechanism algorithm and based on the Expiration of probability and the Collision probability algorithm, found in terms of control channel information, traditional BEB algorithm is no longer applicable, lenovo to broadcast messages without confirmation, most of the improved algorithm were focused on overdue news probability.RBEB and CEB algorithm respectively from message expired probability and comprehensive consideration of the overdue probability of collision and message on retreat algorithm was improved and the improved algorithm on the network performance is greatly improved.According to radio beacon on the control channel without confirmation, in this paper, on the basis of predecessors proposed a New retreat Algorithm based on message Collision and expired probability, first of all, this Algorithm integrated the message expired probability and Collision probability, through the analysis of system model, based on message expired and Collision probability competition equilibrium when the window is based on the theory of the optimal value, the threshold expired messages is deduced, and to determine the current channel state, thus real-time changes in the size of the window value competition, can make it more appropriate response to current conditions in the channel, The simulation result indicates that the algorithm of time delay control within the 3 ms, radio reception rate above 70%.Compared with other algorithms are improved significantlyCombined NS2 and Vanet Mobisim simulation platform, the algorithm is verified by the simulation on the radio reception rate and the time delay has great improvement.