Research On Train-to-Train Communication Resource Allocation Of Urban Rail CBTC System Based On D2D

Communication Based Train Control(CBTC)system is the most widely used signaling system in urban rail transit system.With the increasing demand of transportation service and the requirement of equipment streamlining,the new CBTC system based on train-train communication has emerged and become the focus of research for the next generation signaling system.However,the existing CBTC system wireless communication mostly uses WLAN(Wireless Local Area Network)technology,with the continuous progress and development of wireless communication technology,it gradually reveals its poor mobility,interference and not easy to control and other defects.In addition,the system only has the mechanism of train-toground communication can not guarantee that when the ground equipment fails,the rear-end accident caused by the lack of direct link between the front and rear trains will not occur.Therefore,the introduction of Device-to-Device(D2D)communication technology into the existing CBTC system to realize Train-to-Train(T2T)communication has a broad research prospect and practical significance to ensure train safety and improve train operation rate.In this thesis,based on the current status and achievements of domestic and foreign research,we use the spectrum multiplexing characteristics of D2 D technology and apply it to CBTC system to realize train-to-train communication.By modeling and analyzing the generated co-channel interference,we propose two kinds of train-to-train communication resource allocation algorithms to reduce the interference and ensure the stable communication performance of the system.The research in this paper has certain practicality and can provide some reference value for future T2 T communication development.The main contents of the thesis are as follows:(1)Firstly,the LTE(Long Term Evolution)system architecture and its key technologies are studied.The D2 D communication technology based on LTE-A(LTE-Advanced)is elaborated,including D2 D communication types and resource allocation/interference coordination scheme,and the process of establishing train-train communication link based on D2 D technology is explained to provide the technical basis for train-train communication resource allocation.(2)Secondly,the structure and communication principle of the new CBTC system based on train-train communication are discussed and analyzed,and its transmission delay and packet loss rate are verified;on the basis of this system,in order to make full use of the limited spectrum resources,the T2 T link chooses to multiplex the train-ground communication resources to achieve direct communication between trains.To address the interference problem caused by spectrum multiplexing,a joint resource allocation algorithm based on graph theory and improved SSA(Sparrow Search Algorithm)is proposed,which first converts the channel allocation model into a weighted bipartite graph for solving the optimal allocation problem,followed by adjusting the transmit power of all users using the improved SSA algorithm.Through simulation and comparison analysis,it is verified that the algorithm not only improves the system throughput significantly,but also has the best access rate to the vehicle communication link in the same communication environment,which in turn improves the transmission rate of the system.(3)Finally,in order to reduce a large amount of energy consumption overhead at the user terminal side while balancing energy consumption and system throughput,and considering the high requirements of transmission information,an energy-efficiency based train-train communication resource allocation algorithm is proposed for the multiplexing interference model.By transforming the parameters,the Dinkelbach iterative algorithm is used to coordinate the power of users to arrive at the optimal combination;then the ISAP(Improved Shortest Augument Path)algorithm is used to select the best channel resource for the train-train communication link again,and the simulation results show that the proposed algorithm has the best effect of optimizing the energy efficiency of train-train communication users on the basis of securing the train-ground communication.