Research On Handover Method Of High-speed Railway Wireless Communication Based On Multi-antenna Technology

With the rapid development of high-speed railway and mass wireless communication systems,although LTE-R has improved to a certain extent in terms of system capacity,transmission rate and delay,it still cannot meet the needs of future railway communication systems.Therefore,the deep integration of 5G key technologies in the railway field has become a research hotspot for railway wireless communication systems.Cross-zone handover technology ensures uninterrupted communication of mobile terminals,and the base station deployment along the railway line is the basis for cross-zone switching,and reasonable base station deployment not only improves the channel capacity of the communication system,but also simplifies the cross-zone handover method and improves the handover performance index.In this thesis,Distributed antenna systems(DAS)and C/U(control/user)planar separation heterogeneous networks suitable for high-speed railway scenarios are constructed as ground network architecture by using multi-antenna technology,and the vehicle network architecture is constructed by mobile relay technology,and the cross-zone handover method is studied.In DAS,for handover between RAUs under the control of the same CU,this paper proposes an MFC/FSW algorithm combining the moving frequency concept(MFC)and the frequency switching algorithm(FSW).FSW is used to trigger MFC,which changes the frequency of the RAU while keeping the operating frequency of the mobile trunk unchanged,thereby eliminating the occurrence of handover.The effect of the correction factor reduction rate on the success rate is defined.For the handover between RAUs under different CU control,a fast trigger handover scheme is proposed.By triggering the handover preparation phase in advance,the handover time is reduced,and when the handover request and the command to access the target RAU fail,the failure probability during the handover process is reduced by multiple retransmissions in the overlapping area,thereby improving the service quality of DAS.In the C/U plane separation heterogeneous network,the C-plane information and U information are separated into different frequency bands and transmitted in different cells.An auxiliary micro base station is introduced in the overlapping area between macro-cells,and a separate interleaved handover scheme is proposed on this basis.Firstly,the handover under the traditional heterogeneous architecture is separated into two relatively independent handover between macro-cells and micro-intervals,and the connections of the other plane are interleaved when one handover is performed.Secondly,in the small cell handover scheme,similar to the handover algorithm between RAUs under different CU control in DAS,the handover time and the handover success rate are shortened by early triggering and multiple retransmissions.The handover method between macro cells is the same as that of LTE-R,but the handover process is greatly simplified due to the connection to the user plane.Finally,through the Matlab simulation platform,the simulation results of the handover scheme under the two architectures and the traditional handover scheme are compared and analyzed.In DAS,the MFC/FSW algorithm can eliminate the handover between RAUs under the control of the same CU,and the correction factor effectively alleviates the influence of speed change on the success rate of the algorithm.The proposed fast trigger handover method significantly improves the handover trigger probability in the overlapping area,ensures that the handover is completed with a lower failure probability in the handover range,and provides reliable communication services.The new C/U plane separation heterogeneous network effectively simplifies the complexity of cross-zone switching,and the proposed separation and interleaved handover scheme improves the handover trigger probability and success rate between small regions and the channel capacity of each plane,reduces the cumulative time consumption of handover,and improves the performance of the entire communication system.