# SDR-Based 28 GHz mmWave Channel Modeling of Railway Marshaling Yard  
[PERSON]  
1 Postgraduate Department, China Academy of Railway Sciences, Beijing 100081, China; [EMAIL_ADDRESS]  
[PERSON]  
2 Signal and Communication Research Institute, China Academy of Railway Sciences Corporation Limited, Beijing 100081, China; [EMAIL_ADDRESS] (Y.T. ); Iiyi.sw  
Telecommunication Union (ITU), UIC, and other countries have paid close attention to the coordination of railway-dedicated frequencies and frequency protection. In 2015, the World Radio-communication Conference (WRC-15) decided to set up agenda item 1.11 to study spectrum harmonization for railway radio-communication systems between train and trackside within the existing mobile service allocations, and countries conducted in-depth research on railway radio-communication systems at the ITU level. In UIC, under the umbrella of the future railway mobile communication system (FRMCS) project, the Frequency Working Group (UGFA) was established and is now responsible for studying the related topics of frequency with respect to railway radio-communication systems. The dedicated frequency for railway radio communication has played a significant role in railway transportation production, ensuring safety and improving efficiency, as well as achieving huge economic and social benefits. The European Union has allocated 876-880 MHz (train to ground) and 921-925 MHz (ground to train) as dedicated operating frequency bands for GSM-R in Europe, with over 100,000 km of lines currently deployed. In China, GSM-R uses 885-889 MHz (train to ground) and 930-934 MHz (train to ground), and covers over 85,000 km of railway lines. With the trend of digitalization and intelligence, the contradiction between the increasing service demand and the shortage of frequency resources as well as the limited carrying capacity of railway radio-communication systems has become increasingly prominent. Facing the rapid evolution of radio-communication technology, the broadband of railway radio-communication systems has become a future development direction. Considering the limited frequency resources in the low-frequency band and fragmented allocation, it is an inevitable trend to migrate to the middle- and high-frequency band. In Europe, the existing 2 x 4 MHz R-GSM frequency resources of GSM-R are expanded to the 2 x 5.6 MHz (874.4-880/919.4-925 MHz) ER-GSM frequency band; in addition, 1900-1910 MHz is used as a supplementary frequency band for FRMCS(5G-R). In the meantime, China Railway has submitted an application to the Ministry of Industry and Information Technology(MIIT) for using the 2100 MHz 2 x 10 MHz frequency band as a 5G-R system field test frequency. However, in addition to meeting the requirements of services on the main lines, such as dispatching communication, train control, monitoring, etc., service models in hotspots such as stations and yards are more complicated in terms of service types as well as bandwidth requirements. The 5G-R system facilitated with dedicated frequency support cannot meet the entire communication requirements of hotspots, so other radio-communication technologies and methods need to be adopted as a supplement to the 5G-R communication system. Among these, the mmWave communication system is a promising technology, especially for large bandwidth communication between train and trackside. There are fundamental differences between mmWave communications and existing communication systems, in terms of high propagation loss, directivity, and sensitivity to blockage. These characteristics of mmWave communications pose several challenges to fully exploiting the potential of mmWave communications, including integrated circuits and system design, interference management, spatial reuse, anti-blockage, and dynamics control [1]. Though mmWave has the disadvantages mentioned above, rich continuous and underutilized frequency resources are available in mmWave bands. As a result, mmWave has become a key enabler for future radio-communication technologies.