# Feasibility Test and Analysis for Heavy Haul Freight Using WDPS Based on MIMO-OFDM
## 1 Introduction  
In recent years, as the importance of rail freight transport has emerged as a solution to problems such as energy shortage and climate change, various technical attempts have been made to efficiently operate freight trains [1]. Australia, Canada, the United States, and China, which have a high distribution ratio of freight, are already operating heavy haul freight using wired/wireless distributed control technology as a way to further improve their freight capacity. The heavy haul freight has a shorter braking time, and thus a shorter braking distance, than the conventional centralized control [2]. When the position of the locomotive is not appropriate, the impact between freights due to the asynchronous control time may cause damage to the coupler or a derailment. The ECP braking system which is wired distributed control installed in all freights is connected to the train line to synchronize control signals, and is applied to the transportation of dangerous substances such as gas and oil that require precise control to secure operational stability. But the wired distributed control method has the disadvantage of installing and maintaining a trainline [3, 4]. Another method, the existing wireless distributed control method, applies the FSK method in the 400 and 800 MHz band. The FSK method has a wide communication range and is resistant to diffraction, relatively simple device implementation, but has low frequency efficiency, so it is possible to transmit only the minimum information necessary for operation [5].  
Many researchers have studied on heavy haul freight. [PERSON] et al. presented the minimum time delay of the distributed control signal between the control locomotive (master) and the controlledvehicle (slave) to minimize the longitudinal impact through dynamic simulation [6]. [PERSON] et al. discussed brake performance when driving on steep slopes in locotrol-based distributed control [7]. [PERSON] et al. proposed a method for synchronizing the four distributed wireless distributed modules to transport 50,000 tons in China, and verified this at the laboratory level [8]. Research on the operation of the heavy haul freight has been conducted since the 1970s and communication technology is still being applied, though technology has developed dramatically. WDPS technology in the 400 or 800 MHz band, which is currently used in many countries, has little radio wave loss and a wide communication range, but the transmission rate is limited to 19.2 kb/s [9]. Due to the development of mobile communication technology, large-capacity and high-speed wireless communication is being used for train control, operation, and maintenance [10; 11; 12]. In the case of freight, various sensors are requested to collect status information data using GHz band wireless communication and utilize it for maintenance [13; 14]. For passenger trains, WiFi communication technology in the 2.4/5 GHz band is applied to communicate between onboard and wayside for communication-based train control [15; 16; 17].  
This test is meant to confirm the possibility of using the GHz wireless technology while technically verifying the possibility of operating the heavy haul freight for the first time in Korea. In this paper, we describe the configuration for WDPS based on MIMO-OFDM and test results for control functions, the braking performance and the WDPS performance.  
Section 2 describes the system the configuration of heavy haul freight with WDP and the main technologies applied to WDP, and Section 3 describes the measurement and test for heavy haul freight.