Research On The Performance Of Super Cell Networking In Railway Broadband Mobile Communication System

With the development of high-speed railways,Global System for Mobile Communications-Railway(GSM-R)is gradually evolving to the 5th Generation Mobile Communications-Railway(5G-R)since GSM-R cannot meet increasing business needs of the railway system.5G-R system adopts the co-frequency networking mode,which will inevitably cause the problem of co-frequency interference.In high-speed railway scenarios,communication base stations are deployed along both sides of the railway line.The high-speed movement of trains will cause frequent cell handovers.In order to reduce the number of cell handovers and reduce co-frequency interference,super cell networking is applied in the railway.From the comparison results of field measurement data between super cells and common cells,the throughput performance of super cells is worse than that of common cells.Super cells may cause multipath interference problems,and Doppler frequency shift caused by high-speed movement may destroy the orthogonality between sub-carriers in Orthogonal Frequency Division Multiplexing(OFDM).Therefore,it is crucial to research the impact of multipath interference and Doppler frequency shift on the performance of super cell networking.The research results are helpful to the network deployment of 5G-R system.In this thesis,the theoretical simulation about wireless channel characteristics of super cells and common cells is carried out.Comparing analyzing field measurement data,it is concluded that the throughput performance of super cells is worse than that of common cells.Based on field measurement data and 5G-R test network,a hardware-inthe-loop simulation system is built to simulate super cells and common cells and analyze the performance difference between them.By changing channel parameters,the reasons for the performance of super cells degradation are analyzed.The main work of this thesis are as follows:(1)Channel characteristics of super cells and common cells are analyzed through theoretical simulation.The reasons that may cause the degradation of the throughput performance of super cells are analyzed by comparing and analyzing field measurement data of super cells and common cells such as Reference Signal Receiving Power(RSRP),download throughput,frequency offset,and channel multipath.(2)The hardware-in-the-loop simulation system is built in the laboratory.Two downlink channels of the channel simulator respectively simulate downlink channels of two base stations in the actual scenario.Large-scale fading,noise power,small-scale fading,and Multiple-Input Multiple-Output(MIMO)channel correlation are imported into the hardware-in-the-loop simulation system to simulate super cell networking and common cell networking.And the accuracy of the hardware-in-the-loop simulation system for simulating super cell networking and common cell networking is verified through practical measurement.(3)Based on the hardware-in-the-loop simulation system,the simulation scenario with continuous coverage of four cells is built.The throughput difference between super cells and common cells and the impact of multipath interference and Doppler frequency shift on the performance of super cells are analyzed.When each downlink channel is set to single-path channel model and three-path channel model respectively,the degree to which the performance of super cell is affected by multipath interference and Doppler frequency shift is analyzed,and the throughput performance difference between super cells and common cells at different locations is compared.