Research On Seamless Handoff Mechanism Of High-Speed Railway Multimode Communication System

After the development in recent years,High-Speed Rail has become an important means of transportation for people in medium-distance travel with high-speed,large-capacity,intensive and three-dimensional characteristics.The wireless vehicle-to-ground communication technology is the guarantee for the implementation of TEDS and WTDS train monitoring systems.The safety of train production operations has far-reaching significance.The vehicle-to-ground communication of a single wireless network is difficult to meet the needs of real-time data transmission and reception of trains.Based on the theoretical analysis,this thesis uses information entropy and analytic hierarchy process to design a multi-network,multi-mode heterogeneous network seamless handoff mechanism to solve high-speed trains.The problem of wireless network access in different operating environments improves the coverage and security of wireless vehicle communication,and reduces the delay and blocking rate in transmission.In order to improve the service quality of communication,this thesis clarifies the current application status of traditional wireless networks such as GSM-R and Wi-Fi in wireless vehicle-to-ground communication,and deeply understands the development status of vertical handoff mechanism at home&abroad and applies vertical handoff mechanism to high-speed rail.The meaning of multi-mode communication system,according to the current high-speed rail vehicle communication requirements,select LTE,Wimax,Beidou short message three standard networks,combined with several commonly used vertical handover decision algorithms,for the vertical handoff mechanism applicable to high-speed rail Analyze.In view of the high speed of High-Speed railway and the drastic changes of network environment,firstly,this thesis combs and compresses the sensor data information that needs to be transmitted,and designs the corresponding service frame and data frame structure.Secondly,it divides the wireless channel into two parts:slow fading and fast fading.Channel selection is selected separately.Then,based on the two algorithms of information entropy and AHP,the attribute value and the corresponding weight in the QoS requirement are calculated.The utility function value is calculated according to the utility function formula designed in this thesis.Thirdly,a dynamic adjustment mechanism of information entropy and analytic hierarchy process(AHP)weights is designed,and a new function of network maintenance and triggering is realized by simulation.Finally,the dynamic adjustment mechanism and network continue to be maintained.The triggered function performs simulation and performance analysis in different operating environments.The final simulation results show that the proposed vertical handoff mechanism and the function of maintaining and retriggering the network are superior to the commonly used vertical handoff decision algorithm in the average times of vertical handoff,the blocking rate of new calls and the call drop rate of handoff calls,and meet the communication needs of high-speed trains in different operating environments.The application of vertical handoff mechanism to high-speed rail vehicle-ground communication has certain advantages over the current communication status,which not only improves the service quality of the network,but also plays a role in guaranteeing the safe operation of trains.