Research On Optimization Of CBTC Train-ground Communication System Resilience Based On LTE-M

With the continuous development of wireless communication technology and the gradual expansion of urban rail transit business,the long-term evolution communication system facing the urban rail transit business needs arises at the historic moment,and gradually becomes the research focus of the next generation of Train-Ground communication system.Furthermore,the safety critical CBTC system puts forward more and more strict requirements for the service carrying capacity and service quality of the Train-Ground communication system,which realizes the two-way and large capacity information transmission between train and wayside equipment.Therefore,optimizing the communication performance of CBTC Train-Ground communication system based on LTE-M and improving the Qo S of CBTC Train-Ground communication system have great significance to ensure the reliable transmission of CBTC system security data and realize the smooth and efficient operation of trains.In this paper,the CBTC Train-Ground communication system based on LTE-M is taken as the research object,and a number of performance indexes of Train-Ground communication system are combined to quantitatively analyze the system resilience.In order to realize the joint optimization of Train-Ground communication system resilience and train operation control performance,the optimization of CBTC Train-Ground communication system resilience based on LTE-M is deeply studied.Firstly,the technical background and system architecture of LTE-M system are expounded.Based on the technical principle of CBTC Train-Ground communication system based on LTE-M,the Qo S requirements of CBTC Train-Ground communication system are studied.The transmission characteristics of Train-Ground wireless communication are analyzed in this paper.Moreover,channel models are established from the physical layer and link layer respectively to describe the wireless channel of Train-Ground communication.Secondly,according to the characteristics of LTE-M technology,combined with transmission delay,packet loss rate,handover delay and other performance indicators,the resilience model of Train-Ground communication system based on LTE-M is established,and the stability and recoverability of Train-Ground communication system facing of wireless transmission disturbance are quantitatively analyzed.By introducing the principle of network control system,the NCS model of CBTC multi train control based on resilience index is established,and the relationship between the resilience of Train-Ground communication system and train operation control is analyzed quantitatively.And then,the effectiveness of the proposed resilience model is verified by MATLAB simulation platform.The simulation results show that improving the resilience of Train-Ground communication system can effectively reduce the occurrence of unplanned traction and braking,and reduce the negative impact of disturbance of Train-Ground communication system on train operation control.Finally,based on the proposed Train-Ground communication system resilience model,a semi Markov decision process based Train-Ground communication system resilience optimization strategy is proposed.The handover decision and the adaptive decision of maximum retransmission times of wireless link in the process of Train-Ground communication are described as a SMDP model.The resilience of Train-Ground communication system and the estimation of train traction energy consumption are taken as the optimization objective function,and the optimal strategy of the model is solved by using Q-learning algorithm.At the end,the MATLAB simulation platform shows that the proposed optimization strategy can significantly improve the resilience performance of Train-Ground communication system,and effectively improve the Qo S of Train-Ground communication system,so as to realize the joint optimization of multiple performance indexes of Train-Ground communication system and train operation control performance.