Research Of LTE Space-time Coding Combined With Smart Antenna Beamforming Technology In Highspeed Railway Scenario

The rapid development of high-speed railway(HSR)has brought great convenience and comfort to people,but at the same time,it has also put forward higher requirements for HSR information processing technology.At present,GSM-R,a dedicated digital railway communication system based on the second-generation public mobile communication system,mainly supports narrow-band voice communication service,and the transmission rate is only about 100 kbps.GSM-R is evolving to Long Term Evolution for Rail(LTE-R).However,LTER has higher reliability and security requirements than ordinary public networks,so it needs more effective solutions.In view of this,the thesis will focus on the anti-jamming technology of next-generation railway wireless communication system.Firstly,this thesis introduces the principles of space-time coding technology for LTE-R system,including space-time block codes,space-time trellis codes,layered space-time codes and their corresponding detection/decoding algorithms.The simulation is performed based on Matlab.According to simulation performance and implementation complexity,we evaluate the applicability of these solutions in HSR time-varying scenario.Secondly,based on the opportunities and challenges under HSR scenario,we study the location based beam-forming(LBBF)algorithm,and the performance under ideal and nonideal positioning conditions is well investigated.In order to obtain additional diversity gain,a distributed beam-forming algorithm is proposed in which multiple receiving antennas are placed at the beginning and end of the train,respectively.Simulation results show that the proposed scheme significantly reduces the complexity of solving beam-forming weighting factor,and can achieve better performance in HSR environment.In addition,this thesis studies the mechanism that combines LTE space-time coding with transmit/receive beamforming,and introduces the combined schemes to HSR scenario.We deduce the system expression of combined structure theoretically,and utilize BER as the main index to analyze its performance under the conditions of perfect channel estimation and outdated CSI(OCSI).Simulation results show that combined schemes can obtain better performance than the simple STBC and BF algorithm under perfect channel estimation.For the situation of OCSI,a channel prediction method based on AR model is introduced,and it is verified that the proposed scheme can significantly improve the system performance.