Research On The Performance Of Urban Rail Transit System Based On Train-to-Train Communication

In recent years,urban rail transit has become a preferred mode of transportation for people due to its advantages in punctuality,comfort,safety,and stability.However,the existing urban rail transit adopts the communication-based train control(CBTC)system,whose key functions,such as train operation and safety protection,are highly dependent on complex ground equipments,and restricted the needs of rail transit in terms of operational efficiency improvement,interconnection and large-scale equipment replacement.As the future research and development directions of urban rail transit,trainto-train(T2T)communication supports train safety,high density,and automatic operation,which has great development space and potential.Therefore,exploring T2 T communication is of great significance to ensure the development needs and performance improvement of urban rail transit systems.This thesis analyzes the research status and future development of T2 T communication and urban rail transit data communication system by consulting the literature,and studies the performance of millimeter wave based T2 T communication.The main research contents are as follows:(1)A hybrid precoding-based T2 T communication transmission scheme is proposed.In the straight-through scenario,the communication mechanism of the transmitting train and the receiving train adopts a hybrid precoding structure,which can ensure the reliability of the system communication and further reduce the hardware design cost of the system.At the same time,this thesis also proposes an alternating minimization algorithm based on phase extraction,in which phase extraction is a solution method for the process value of the analog radio frequency(RF)precoder.The method transforms the multiplication problem into an addition problem through a series of matrix operations,and then into a problem of phase solution.Alternating minimization is to fix one vector and solve another vector alternately.The algorithm simplifies the design process of digital baseband precoding and analog RF precoding,and reduces the computational complexity.Compared with analog precoding and fully digital precoding schemes,the proposed scheme has obvious advantages.In addition,by analyzing the effects of the number of data streams,the number of RF chains,and the T2 T communication distance on the system performance,the proposed scheme can provide theoretical guidance for practical design of T2 T communication.(2)Two position-assisted beam alignment methods are proposed.In turning scenarios,rapid changes in train position and angle can cause frequent beam misalignment.Therefore,the problem of narrow beam alignment between two trains needs to be studied.This thesis first calculates the beam coherence time related to the number of antennas and the average train speed,which provides a reference for the implementation of the T2 T communication scheduling algorithm.Then,in order to simplify the beam search process,this thesis proposes two algorithms,namely LocationAssisted Neighbor Search(LANS)algorithm and Location-Assisted Angle Comparison(LAAC)algorithm.Since the latter has lower complexity under the same performance,this thesis mainly focuses on the LAAC algorithm.This algorithm uses the train position information exchanged by T2 T communication to estimate the beam deflection angle,and obtain analog beamforming and combining vectors by comparing the estimated beam deflection angle with the reference phase angle.Finally,the influence of the position estimation error on the proposed algorithm is considered,and the robustness of the algorithm is proved.There are 38 figures,5 tables and 79 references in this thesis.