The Research And Implementation Of Adaptive Transmission Strategy For The Communication Between High-speed Train And Ground

With the large-scale popularization of high-speed rail, it has formed a large and complex system, and will continue to increase. It is the basis to run train safely that carries out the maintenance with high efficiency and quality。the ground monitoring system can get the real-time status of the train in time through communication of operational data based on wireless public network, and can easily make arrangement of the daily incoming inspection and maintenance for the train, which improves the efficiency of the high speed train operations. The main reason of low communication performance relates with signal instability caused by the uneven distribution base station along high-speed railway.AT the same time, it leads to signal quality deterioration and BER increasing with the train speed increasing. It needs to be addressed how to meet the requirements of the real time and reliability of data communication under the complicated geographical environment and high speed motion state.To solve the problems above, this paper proposes an adaptive transmission strategy to improve the transmission quality of the data communication between the trainand ground. The method includes two parts:network quality prediction and adaptive transmission strategy. In the first part, the network quality is reflected with the signal quality; In order to predict the network quality accurately, the exponential smoothing prediction algorithm is improved according to the characteristics of the signal quality in high speed environment. As for the second part, the relationship between the packet loss rate and packet size is mainly discussed, and it makes the appropriate changes to transmit strategiesbased on the predicted network quality to improve throughput. The simulation results show that the prediction algorithm used can predict network quality effectively; adaptive transmission strategy can improve the throughput of the sending process.Finally, the policy is implemented in the program, and run in the real environment. It was found that the adaptive transmission strategy above does work by comparing and analysing the data from both the process used the strategy and the process not used the strategy.