# SDR-Based 28 GHz mmWave Channel Modeling of Railway Marshaling Yard
### Related Works  
Scholars have carried out a series of related work with respect to mmWave. Corresponding research will be reviewed from four categories involving communication scenarios, frequency bands, and research methodology, as well as the object of the research. From the communication scenario point of view, railway, metro, residential house, indoor commercial, tropical area, and many other scenarios are covered by the open literature. With respect to railway scenarios, in [3], channel characteristics are studied in the 5G mmWave band centered at 25.25 GHz for typical urban HSR scenarios, including straight and curved route shapes. In [4], the 28 GHz mmWave channel characteristics of rural railway scenarios are studied via a calibrated ray-tracing simulator. Ref. [5] also focuses on the 28 GHz mmWave channel characteristics of rural railway scenarios, in which the dominant propagation mechanisms (direct, penetration, reflection, scattering, etc.) are determined and the three-dimensional environment model and the electromagnetic parameters of different objects are calibrated. The automatic coupling application scenario is studied in [6], in which a dynamic train-to-train (T2T) mmWave propagation measurement campaign was conducted, and the received signal power in the open field area was analyzed and modeled using a two-ray path loss model. The results indicated that the received power next to a platform was higher compared to the open field counterpart due to strong contributions from the signals reflected by the platform. The work in [7] studied the wireless coverage for intra-wagon scenarios at the 60 GHz band; by considering the balance of the wireless coverage and the cost of the transmitters, the deployment of two transmitters in one wagon is suggested. Typical objects in the railway propagation environment are also important research areas. In [8], a significant analysis methodology, which analyzes and distinguishes the contributions of different railway objects to the mmWave propagation channel, is proposed. In [9], the influence of typical objects to the mmWave propagation channel is analyzed for \"train-to-infrastructure\" and \"intra-wagon\" railway scenarios with various configurations. In [10], a statistical mmWave channel modeling for railway communications backhaul in 5G networks was proposed, involving 28 GHz and 60 GHz, by simulating in a novel software, NYUSIM. Viaducts and tunnels are common scenarios of railway terrain, especially in high-speed railways. The work in [11] considered measurement-based ray-tracer calibration and channel analysis for high-speed railway viaduct scenarios at 93.2 GHz, and the conclusion that the typical structure of viaducts and the application of horn antenna lead to a small value of Rician K-Factor and RMS delay spread is drawn. In [12], the authors investigate the mmWave propagation characteristics of a high-speed moving train based on field measurements in tunnel and viaduct scenarios. The measurements were carried out at 28 GHza and path loss (PL) and other channel parameters, including delay spread and Doppler shift, were investigated. In [13], smart-rail mobility was discussed, and the authors identified the main technical challenges and the corresponding chances concerning the reference scenario modules, accurate and efficient simulation platforms, beamforming strategies, and handover design. A mmWave beamforming scheme for disaster detection in high-speed railways was proposed in [14]; the key point of the study was that the antenna array generates multiple beams with different beam widths in different frequency bands simultaneously and the multiple beams are responsible for different detection areas. Another way to improve the reliability of railway communication is interlaced redundant coverage; in [15], a location-fair-based mmWave stable beamforming scheme under interlaced redundant coverage architecture is proposed to improve the stability and reliability of high-speed railway communications.