The Research On Several Key Technologies For Vehicle Ad Hoc Networks Data Communications

With the rapid development of automotive,vehicle has become a system which composes with machinery,electron,communication and network.Vehicle needs a mass of electronic control units to support to realize luxuriant automotive functions.More and more signals between ECUs need to transmit through vehicle area networks.Automotive electron already becomes an important portion of modern vehicle.At present,the most extensive vehicle ad hoc network is Control Area Network.FlexRay protocol is emerged as the defacto standard for automotive communication systems.For the balance of cost and performance,the coexistence of various vehicle ad hoc networks will exist for a long time.We focus on the data packing of heterogeneous networks and message scheduling in FlexRay in this paper base on the vehicle ad hoc networks current situation and development tendency.Many different automotive buses are used for connecting different functional ECUs in vehicle.It is unavoidable that ECUs need to exchange data between heterogeneous networks.Data transmission affects the message effective and system reliability.From the perspective of automotive heterogeneous networks gateway,we design a new CAN/FlexRay data packing method.With the real time guaranteed,this method improves the transmitting ability for gateway by rising the utilization of message data segment and reducing the competing frequency of bus.We also design an experimental model to analyze and test it.The result shows that the new method can improve the heterogeneous networks messages chedulability and the bandwidth utilization.FlexRay network gets highly appreciated in automotive industry by its excellent performance.This paper focuses on message scheduling in FlexRay,and analyze the principle of message scheduling in communication cycle.Then,we design a hybrid method of scheduling dynamic messages in static segment to improve the static segment bandwidth utilization,reduce the waiting time of dynamic messages in the queue and increase the messages schedulability.Finally,we design an experiment and test the hybrid scheduling method.It compares with traditional principle scheduling method.The result shows that the new method is more efficient than traditional scheduling method on improving bandwidth utilization and message schedulablility.