Test And Evaluation Of LTE-R System Service Quality On High-Speed Railway

With the rapid development of high-speed railway and the continuous improvement of train speed,in order to ensure the safe and efficient operation of trains,the operation of high-speed railway puts forward more stringent requirements on the effectiveness and reliability of railway mobile communication systems.The current GSM-R narrow-band communication system can no longer meet the needs of future railway services,including video monitoring,infrastructure monitoring and passenger mobile information services.The evolution of GSM-R to LTE-R has become an inevitable trend.Due to the particularity of wireless signal propagation environment,base station coverage mode and user equipment movement speed in the railway scenario,LTE-R system is not completely equivalent to LTE public network system.Before the actual deployment,test work in the actual environment needs to be carried out.According to the analysis of test results,wireless network planning and optimization are carried out reasonably so as to achieve the goals of efficient and reliable transmission of railway business information between trains and ground as well as the safe and stable operation of trains.This paper mainly studies the deployment strategy of LTE-R system base station in actual engineering construction,and proposes a reasonable cell radius recommendation to meet the railway service quality requirements.Based on the above research objectives,the actual test work of LTE-R system under the high-speed railway scenario was carried out in the Beijing-Shenyang Passenger Line test section.The test mainly tested the LTE-R network coverage performance and system service quality including throughput,transmission delay and packet loss rate throughout the test section from Shenyangxi Railway Station to Wulanmutu Railway Station.Based on the two types of test-collected data,which respectively reflect the network coverage quality and system service quality,and the off-line interference problem of extrasystem pantograph and catenary during the test,the main work of this paper is as follows:(1)Based on the LTE-R system performance test and the test data,the relationship between LTE-R network coverage quality and system service quality is studied,and the coverage scheme to meet the railway service quality requirements is given.Firstly,the key indicator reflecting the quality of network coverage is extracted by the method of statistics and analysis in data mining.The relationship model between network coverage quality and service quality as well as the path loss model is established.Combined with the analysis of the railway traffic flow model,reasonable cell radius is given.Secondly,the link budget is applied to the uplink and downlink of the LTE-R system,and the cell radius is given from another perspective in combination with the path loss model.Based on the above two methods,the coverage plan of the LTE-R in the 450MHz frequency band that meets the railway business needs is given.(2)Theoretical analysis and laboratory test research are carried out to solve the problem of external pantograph and catenary interference in the testing process.Firstly,the mechanism of off-line noise generation in the electrified railway system is analyzed.Then the interference source is analyzed and modeled,and its time domain and frequency domain characteristics are simulated.It is proved that the noise spectrum covers the 450?470MHz frequency band so that the noise can generate interference to LTE-R system.It is theoretically analyzed that the interference will not influence the availability of the LTE-R system,but it will cause loss to the system performance.Finally,a laboratory interference test system is set up to study the influence of interference of different intensity on the system service quality under different coverage quality.According to the interference test results,the LTE-R coverage field strength requirements,which can reduce the influence of system interference on the system bearer service,and the base station deployment strategy of LTE-R system are studied through theoretical analysis,combining with the test data of Beijing-Shenyang Passenger Line test section.