Study On The Application Of Device-to-Device Communication In Train Operation Control System

Communication Based Train Control(CBTC)systems usually use Wireless Local Area Networks(WLANs)to ensure the bi-directional data communication between trains and wayside equipment.On the one hand,WLANs which use open frequency band have the own limitations and shortcomings,such as Co-Channel interference and poor user mobility support.On the other hand,conventional CBTC systems only use single train-ground communication,which is not able to avoid the train collision accidents due to train operation equipment breakdown or control center failure.Therefore,the train-to-train communication technology is needed to improve the availability and reliability of data transmission in CBTC systems.In this paper,we analyze the application of Device-to-Device(D2D)communication in train operation control system of urban rail transit systems.The direct data communication between trains using D2D communication technology is able to improve the availability and reliability of data transmission in train operation control systems.The research in this paper is innovative and practical,and is able to support relative works of the engineering application of TD-LTE and D2D communication technologies in urban rail transit systems.The details of this paper are as follows.(1)The details of Long Term Evolution(LTE)and D2D communication technology in LTE-Advanced are analyzed,which contain the system architecture and key technologies of LTE.The general categories,implementation method,resource and power allocation and communication establishment processes of D2D communications are also introduced in this section.(2)The different communication schemes in train operation control systems with and without train-to-train communications are presented.In this paper,we introduce a joint data transmission scheme which combines train-ground communication and train-to-train communication to provide better train control data transmission performance.The detailed train-to-train communication link establishment process are given based on the joint scheme.The joint scheme mechanism containing communication content,transmission method and data fusion are designed in this section.(3)The impact of transmission delay and packet drop on train operation control system performance is presented.Firstly,the transmission delay and packet drop of train-to-train communications are analyzed and compared with that of the train-ground communication links based on LTE.Then the transmission delay and packet drop using the joint scheme,as well as the train operation control system performance improvement with the introduction of train-to-train communication links are analyzed.(4)In order to decrease the resource overhead while improving the data transmission performance,the multiplexing of current resources to achieve train-to-train communications is designed.The resources management strategy based on location and throughput of trains is presented to reduce the interference brought by multiplexing of the same wireless resources and improve the frequency efficiency and overall performance of train operation control systems.The results show that train-to-train communication delay is much smaller than train-ground communication delay,and the application of train-to-train communication is able to reduce the packet drop rate of train operation control system data communication.Moreover,the location and throughput based resources management strategy proposed in this paper can both satisfy the throughput requirement of CBTC business and improve the success rate of train-to-train communication establishment and system frequency efficiency.