Research On Application Of D2D Communication Based On LTE In Urban Rail Transit

The main function of train control system in urban rail transit is to control train and guarantee traffic safety.The most widely used train control system is the communication based train control system(CBTC).With the rapid development of science and technology,the existing CBTC system is being upgraded to the new generation CBTC system.The new generation CBTC system has better structure and stronger function.Train to train communication is one of the important characteristics of the new generation CBTC system and also an important point to develop the new generation CBTC system.D2 D communication in LTE supports the direct transmission of data,which is suitable for realizing train to train communication.The application of D2 D communication in CBTC system is studied in this dissertation.On one hand,the architecture and communication mechanism of CBTC system with train to train communication are analyzed.On the other hand,the implementation of train to train communication based on D2 D technology is researched and a resource allocation joint power control algorithm is proposed as the implementation scheme.Firstly,the LTE system is described and the LTE based D2 D communication is mainly introduced including its working mode and technical characteristics.And the process of establishing train to train communication based on D2 D is illustrated.Secondly,the CBTC system architecture and communication mechanism are investigated.The research focuses on train control subjected CBTC system and train to train communication assisted CBTC system.The structure and working mode of CBTC system after adding train to train communication link and the communication mechanism between modules of CBTC system are expounded and the functions of train to train communication link in the new CBTC system are clarified.The new CBTC system is compared with the existing CBTC system to research the improvement of the existing CBTC system by train to train communication link.Finally,the implementation scheme of train to train communication based on D2 D technology is researched.The system model is constructed,the optimization function is defined and the interference in the system is analyzed.A resource allocation joint power control algorithm is proposed as the implementation scheme for train to train communication.The algorithm determines the set of train ground communication links that can share wireless resources for the permitted train to train communication links.And then scheduling the resource in two steps,according to the channel state information,the weighted bipartite graph optimal matching algorithm based on hierarchical network is used to optimize the allocation of wireless communication resources.Then the improved beetle antennae search algorithm is used to optimize the transmitting power on the premise of ensuring the quality of service of the link to maximize the throughput of the system and improve the performance of the system.Simulation results show that compared with the random allocation algorithm and single resource scheduling algorithm,the joint algorithm can improve the throughput of the system while ensuring the quality of service and the utilization of spectrum is more efficient.