Research On Backoff Algorithm Based On Sender-based Packet Loss Discrimination In Vehicle Networking

In the protocol of vehicular ad-hoc network,correctly determining the type of data frame loss and adopting a reasonable processing method is of great significance for improving the performance of the protocol.Based on the in-depth study of IEEE 802.11 p protocol,this paper proposes a sender-based packet loss discrimination algorithm based on the problem that the traditional packet loss discrimination algorithm performs poorly in dense and high-speed motion scenarios.The MAC layer unicast mode and the broadcast mode backoff algorithm are improved.Firstly,this paper proposes a packet loss discrimination algorithm,which is completed independently by the sender.By detecting the signal-to-noise ratio and the number of surrounding nodes,a mathematical model is constructed to predict the collision loss probability and the weak signal loss probability,and then determine the packet loss type.The algorithm solves the problem that the traditional algorithm needs to repeatedly exchange data when distinguishing the packet loss type,and adds additional network overhead.At the same time,it can also be directly applied to the broadcast mode to solve the problem that the broadcast mode cannot determine the channel environment.The simulation results show that the algorithm can achieve the accuracy of 95.59% without modifying the data frame format and adding other control frames.Aiming at the problem that the IEEE 802.11 p MAC layer performs poorly when the mobile vehicle nodes are dense,this paper proposes a protocol improvement scheme based on the packet loss discrimination algorithm.In unicast mode,the transmission probability and collision probability in the improved algorithm are calculated.The algorithm adjusts the backoff window and MCS value according to different packet loss types.It can be obtained from the simulation analysis that the unicast backoff algorithm with packet loss discrimination mechanism can adapt to the environment well,especially in the environment where the vehicle nodes are dense,which significantly improves the system performance.Aiming at the defect that the IEEE 802.11 p broadcast mode cannot make reasonable adjustment according to the surrounding environment,this paper proposes an adaptive backoff algorithm based on the number of vehicle nodes,and based on the packet loss discrimination algorithm,the MAC layer adopts "two frames" when appropriate.In the way of continuous transmission,the algorithm improves the accuracy of data transmission under the condition of reasonable delay.