Research On Multi-beamforming Scheme For MmWave High-speed Railway Communication

With the continuous upgrading of mobile communication technology and the vigorous development of Internet +,the data traffic generated by smart devices such as mobile phones and tablet computers carried by passengers on high-speed trains has dramatically increased,and that puts forward higher requirements for the capacity of high-speed railway mobile communication system.Therefore,how to design an effective system throughput optimization scheme to meet the requirements on higher throughput and high reliability has become one of the research hotspots.As one of research focuses of the fifth generation of mobile communication,millimeterwave(mm Wave)communication has the advantage of abundant frequency band resources.Massive multiple inputs multiple outputs(MIMO),as a key multi-antenna technology,can effectively alleviate the loss of mm Wave in the transmission process.As an important MIMO technology,beamforming can enlarge the coverage range of signal,enhance the energy of signal and suppress interferences.Therefore,the combination of mm Wave communication and massive MIMO beamforming can give full play to the advantages of both technologies and significantly improve the system performance,and therefore can provide strong technical support for the development of mm Wave communication in high-speed railway.In this thesis,the mm Wave massive MIMO technology is used in the high-speed railway scenarios,and the focus of the research is the beam selection issue for massive MIMO beamforming.The main contribution of this thesis includes:(1)Adaptive antenna-beam joint selection scheme with variable number of array antennas:Based on the existing adaptive beam selection scheme and the relationship between the number of array antennas and the system capacity,an adaptive antenna-beam joint selection scheme with variable number of array antennas is proposed to improve the throughput of the high-speed rail mobile communication system.By using the position information of the train,the proposed scheme can adaptively select the beam set and the number of array antennas,and therefore can significantly improve the system throughput.Simulation results show that,compared with the existing adaptive multi-beamforming scheme,the proposed adaptive antenna-beam joint selection scheme with variable number of array antennas can significantly increase the system capacity.When the train is in the(240m,360m)area of the base station cell,the system capacity can be increased by about 20 Gbps.(2)Improved adaptive antenna-beam joint selection scheme with low-complexity: A lowcomplexity version of the adaptive antenna-beam joint selection scheme with variable number of array antennas is proposed to reduce the computational complexity.In the proposed lowcomplexity version,different beam selection algorithms can be used according to the position information of the train,and therefore the number of iterations of searching the beam set and the number of array antennas can be effectively reduced.Simulation results show that compared to the adaptive antenna-beam joint selection scheme with variable number of array antennas,its improved version has lower computational complexity complexity while guaranteeing system throughput performance.In the middle region of the base station cell,the number of iterations is reduced by about 3000 times,and in the edge region,the number of iterations is reduced by 18,424 times.