I. Introduction
With the growth of traffic demand, rail transit technologies such as subways and high-speed trains have been rapidly developed [1]. The increase in the speed and density of trains has made safety become a primary consideration in the train operation [2], [3]. As an important respect to ensure the safety of train operation, TCN has gradually developed from the application of processing critical signals to the application of processing all kinds of large-capacity data [4]. However, with the increasing application of the Internet of Things (IoT) and intelligent devices in trains, the amount of communication data is becoming complex. The transmission of large amount of data, including safety data, control data, and information data, requires large bandwidth of TCN [5]. The transmission rate of the bus-based TCN can no longer meet the requirement of real-time transmission of large amount of data [6]. The application of fieldbus in TCN is also hindered by the shortage of hardware and software costs of multi-supplier systems as well as the uncertainty of interoperation [7]. With the wide use of user datagram protocol (UDP) and transmission control protocol (TCP), industrial Ethernet has become the main solution of TCN because of large bandwidth and high compatibility [8]–[12].