Research On The Fast Handover Technology Of Wireless Network Based On Location In High-Speed Railway

At present,the reference signal receiving power is still used for handover decision in the wireless network of high-speed railway.However,when the terminal mobile speed is greater than 200 km/h,problems such as the increase of handover delay,handover failure probability and communication interruption probability of the traditional handover scheme lead to the extreme deterioration of the network perception of the passenger.In order to improve the communication quality of high-speed railway wireless network,it is urgent to study a new scheme of handover.This thesis mainly focuses on the handover problem of wireless networks in high-speed railway.Two positioning algorithms suitable for the interior terminals of high-speed trains have been proposed through the measurement of parameter.On this basis,the fast handover scheme of wireless network based on location has been studied in high-speed railway.The main works include the following four aspects.(1)Based on the wireless network parameter measurement principle of high-speed railway,the wireless network parameter measurement of Lanzhou-Xin high-speed railway is carried out in Gansu province.The constructed wireless network quality data set provides important support for the research of high-speed railway wireless network characteristics,high-speed train terminal location algorithm and location-based fast handover scheme under the chain structure.Due to the tunnel shelter,mountain block,U-shaped trough and other complex terrain factors around the orbit,the satellite signal becomes extremely weak and the GPS receiving device is frequently interrupted,resulting in the serious loss of terminal position information in the wireless network quality data set.The sampling data such as physical cell identification,reference signal receiving power and reference signal receiving quality cannot be visualized on the map,which brings great difficulties to the quality improvement of wireless networks.The loss rate of GPS signal of high-speed train terminal is more than 70% by analyzing the data of parameter measurement.(2)In the mobility control of communication system,the receiving power and quality of reference signal are the key parameters of physical layer measurement.Based on the constructed data set of high-speed railway wireless network quality,the characteristics of wireless network under the chain structure are studied.It is found that the coverage distance of base station in high-speed railway wireless network is significantly different from that in cellular network,and the coverage distance increases linearly with the increase of station gauge along 7.8 slope.The characteristics of high-speed railway wireless network,such as path loss,vehicle penetration loss,leakage cable power loss and antenna receiving power,are studied.Based on the analysis of the characteristics of high-speed railway wireless network,such as path loss,vehicle body penetration loss,leakage cable power loss and antenna receiving power change,the wireless network coverage scheme suitable for non-tunnel,tunnel and tunnel mouth of high-speed railway is presented respectively.Under the same train operating environment and parameter setting conditions,the coverage distance of the lens array high-gain antenna deployed in the high-speed railway wireless network is 4.38% and 4.19% higher than that of the traditional antenna,respectively.(3)Two terminal location algorithms of high-speed railway wireless network are proposed.According to the handover point of the adjacent base stations,the coverage of each base station along the high-speed railway is calculated,and the equivalent and missing track latitude and longitude information is interpolated to realize the positioning of the measurement terminal,and the high-precision positioning is achieved by using the azimuth of the residential area and the map of the high-speed railway.With 300,000 wireless network signals and the corresponding position information of sample build-position based on fingerprint,lack of GPS signal terminal counters,threshold and weighted by setting the fingerprint integral measure eigenvalue tectonic facies thin matrix to complete the calculation of warp/weft and latitude,innovative fingerprint localization algorithm was applied to high-speed rail.Both algorithms achieve high-precision and high-efficiency terminal positioning,with the average positioning accuracy less than 10 m.At the beginning of the application of Fifth Generation Mobile Communication Technology(5G),the location information of the unpositioned terminal is calculated according to the location algorithm based on the cell azimuth angle;in the non-tunnel scenario,and the location information of the unpositioned terminal is calculated according to the location algorithm based on the quadratic fuzzy clustering fingerprint database in the tunnel terrain.In the middle and later stages of 5G network construction,with the increase of highspeed railway wireless network measurement data and the expansion of high-precision positioning results in fingerprint database,both tunnel terrain and non-tunnel terrain can use the positioning algorithm based on twice-fuzzy clustering fingerprint database to calculate the location information of GPS signal missing sampling points.(4)A fast handover scheme based on location in high-speed railway wireless network is studied.Based on the basic theory of mobility management and its application,the receiving power of synchronous reference signal measured by parameters,the receiving quality of synchronous reference signal and the real-time train track are analyzed.By calculating the speed and direction of high-speed train,the reasonable cell handover mode is selected and the positive and negative neighborhood handover chain is identified.After the location information is calculated,it can judge whether the terminal enters the pre-switch identification zone.When the weight of the measured data of the target cell is greater than that of the measured data of the source cell,the handover command is triggered to achieve the purpose of fast handover of the wireless network of high-speed railway based on location.Compared with the current handover scheme,the handover delay of the location-based fast handover scheme is reduced by 8.69%when the train speed is 300 km/h.Compared with power regulation technology,remote antenna technology and distributed antenna technology,the failure probability of the location-based fast handover scheme of high-speed railway wireless network is reduced by 11.24%,23.44% and41.26%,respectively.Compared with power regulation technology,remote antenna technology and distributed antenna technology,the probability of communication interruption is improved by 11.71%,19.80% and 56.25%,respectively.With the rapid development of China’s rail transit,the above research results provide useful ideas for solving the problems of passengers’ Internet access perception deterioration in high-speed railway wireless network,such as handover delay,handover failure probability and communication interruption probability,when terminals move fast.It also has certain theoretical and practical guiding significance for the sustainable development of long term evolution(LTE)for high-speed railway wireless network.It will also provide prospective research directions for the exploration and deployment of 5G-railway(5G-R)system in the future.