Research On Improvement Of Channel Capacity Algorithm In High-speed Railway LTE Environment

The rapid development of high-speed railways in China and the inter-vehicle communication in high-speed mobile environments have become one of the key research directions in the field of wireless communications.As the train speed increases continuously,the resulting Doppler shift and fast Doppler changes cause the channel to be fast time-varying and non-constant,and the resulting inter-carrier interference ICI will greatly affect the bit error rate performance of the signal transmission.It not only affects the wireless communication environment of high-speed railway,but also affects the data transmission efficiency,which ultimately leads to a serious reduction in channel capacity.This paper conducts in-depth research on the inter-carrier interference cancellation technology and the improvement of channel capacity.The following is the main work of this paper:Firstly,the evolution process of the network structure of LTE communication system and its key technologies are introduced.The current status of high-speed railway channel measurement technology and research is compared.The multipath quantity of the Beijing-Shenyang Passenger Dedicated Line is analyzed.The characteristics of the high-speed railway channel and the characteristics of radio wave propagation are expounded.The basic theoretical knowledge of the LTE system applied to the high-speed rail channel is introduced.Secondly,the high-speed railway environment download inter-wave interference cancellation algorithm is studied in depth.Based on the existing traditional inter-carrier interference cancellation algorithm,the non-constant time-varying channel caused by Doppler shift is modeled and OFDM is proposed.Joint optimization algorithm for inter-carrier interference cancellation.In the high-speed railway moving scenario,the algorithm first uses the cyclic prefix sequence as the guard interval,and then performs a function linear weighting on each sub-sequence.Because the received symbol interference is reduced,the sensitivity of the system to the sub-carrier frequency offset is reduced..The simulation results show that the improved algorithm can effectively improve the performance of the system and ensure the good communication quality of the train during high-speed operation.Finally,on the assumption that the above-mentioned inter-carrier interference cancellation technology does not reach the ideal state,it is analyzed how to maximize the channel capacity when there is still ICI interference.The algorithm establishes the MIMO-OFDM communication channel model in the scenario of high-speed rail inter-carrier interference,and proposes an iterative optimization design of the transmit beamformer technology.In order to optimize the total subcarrier capacity,firstly,the convex function of the covariance matrix is optimized,and then the optimal propagation direction is provided foreach subcarrier,and the optimal transmission direction is kept unchanged.The power of the carrier is optimally allocated by the method of minimizing the cycle,so that the channel capacity is maximized under the condition of power constraint.The simulation results show that the proposed iterative algorithm can improve the performance of the link to some extent by using the multi-antenna technology to deal with the impact of the ICI.