Binghao Chen

Radio Wave Propagation Scene Partitioning for High-Speed Rails

Radio wave propagation scene partitioning is necessary for wireless channel modeling. As far as we know, there are no standards of scene partitioning for high-speed rail (HSR) scenarios, and therefore we propose the radio wave propagation scene partitioning scheme for HSR scenarios in this paper. Based on our measurements along the Wuhan-Guangzhou HSR, Zhengzhou-Xian passenger-dedicated line, Shijiazhuang-Taiyuan passenger-dedicated line, and Beijing-Tianjin intercity line in China, whose operation speeds are above 300 km/h, and based on the investigations on Beijing South Railway Station, Zhengzhou Railway Station, Wuhan Railway Station, Changsha Railway Station, Xian North Railway Station, Shijiazhuang North Railway Station, Taiyuan Railway Station, and Tianjin Railway Station, we obtain an overview of HSR propagation channels and record many valuable measurement data for HSR scenarios. On the basis of these measurements and investigations, we partitioned the HSR scene into twelve scenarios. Further work on theoretical analysis based on radio wave propagation mechanisms, such as reflection and diffraction, may lead us to develop the standard of radio wave propagation scene partitioning for HSR. Our work can also be used as a basis for the wireless channel modeling and the selection of some key techniques for HSR systems.

Complete Propagation Model in Tunnels

The wave propagation in tunnels does not only depend on the carrier frequency and properties of the tunnel, but also differs along with the distance between transmitter (Tx) and receiver (Rx). This letter presents a complete structure and model for propagation in tunnels. Compared to existing models, the complete model unifies different academic viewpoints, reveals all possible propagation mechanisms, and localizes all the dividing points between every two adjacent propagation mechanism zones. When the user is close to the Tx, the propagation is dominated by the free-space mechanism, then the multimode mechanism is established. Afterwards, when the high-order modes have been largely attenuated, the fundamental-mode guided propagation is dominant. Finally, when the user is extremely far away, the waveguide effect vanishes because of attenuation of reflected rays. Measurements and simulations validate the model. This complete structure and model can be essential to establish a comprehensive understanding of the propagation in tunnels and can be applied for network planning and interference analysis of advanced communication systems.

Channel Characteristics in High-Speed Railway: A Survey of Channel Propagation Properties

In this article, we give an overview of recent research on propagation properties in high-speed railways (HSRs). The channel fading in HSRs is a big challenge for wireless access. It is essential to understand the channel-fading behavior before the system design. The novel results of propagation and channel models are presented. The details of channel characteristics, such as path loss, shadow fading, and Ricean K- factor, are discussed in each scenario. A comprehensive picture of propagation and channel-modeling research in railways is shown.

A Geometry-Based Stochastic Channel Model for High-Speed Railway Cutting Scenarios

The scattering issue in the channel model for a railway cutting - a man-made trough or valley that carries a railway at its base - that is applicable to high-speed railway is discussed. The scattering components are rich in cutting and can be modeled by a cluster to enhance the accuracy and efficiency of the channel model, which is based upon geometry-based stochastic channel modeling. The channel parameters are extracted from measurement data collected along the Zhengxi high-speed railway. The size of the cluster is determined by the structure of cutting and channel parameters, such as pathloss exponent and Ricean K factor. A constraint condition of the cluster size is derived based upon theoretical analysis and verified by measurement data.

Complete Propagation Model Structure Inside Tunnels

In this paper, a complete model structure for propagation inside tunnels is presented by following the segmentation-based modeling thought. According to the concrete propagation mechanism, totally flve zones and four dividing points are modeled to constitute three channel structures corresponding to large-size users and small- size users. Firstly, the propagation characteristics and mechanisms in all the zones are modeled. Then, from the view point of the propagation mechanism, the criterion of judging the type of a user is analytically derived. Afterwards, all the dividing points are analytically localized as well. Finally, a panorama covering all the propagation mechanisms, characteristics, models, and dividing pints for all types of users is presented for the flrst time. This panorama is very useful to gain a comprehensive understanding of the propagation inside tunnels. Validations show that by using the analytical equations in this paper, designers can easily realize a fast network planning for all types of users in various tunnels at difierent frequencies.

Comparison of Antenna Arrays for MIMO System in High Speed Mobile Scenarios

The impact of antenna array geometry on MIMO (Multiple-input Multiple-output) system in high speed railway scenario is investigated in this paper. The capacity of different antenna arrays and the effect of ULA (uniform linear array) azimuthal orientation on capacity are studied with a double-directional channel model including antenna effects and Doppler shift.

Moving Virtual Array Measurement Scheme in High-Speed Railway

The moving virtual array measurement scheme, which means several adjacent samples from one single receiving antenna on a moving train or vehicle can be considered as the reception of multiple antennas, is proposed to overcome the difficulties of multiple-input-multiple-output (MIMO) channel measurement in high-speed railway scenario. This idea is similar to the virtual array measurement in static environment. Furthermore, the number of the equivalent elements in moving virtual array is derived by combining with the principle of switch multiplexed array scheme used in time-variant channel measurement. To verify this scheme, a 1X3 single-input-multiple-output (SIMO) channel sounder is built, and the measurements are carried out in a moving environment. The results show that moving virtual array scheme can reflect the spatial channel characteristics, especially in high signal-to-noise ratio (SNR) range. Finally, the applications of this scheme are discussed.

Antenna array configurations for 3D MIMO system in high speed railway scenario

In the future work of long-term evolution for railway (LTE-R), a better understanding of the antenna array configurations is required. This paper primarily proposes the extension of 2D clustered channel model to 3D circumstance by getting elevation angle involved. Based on the presented 3D channel model, the attainable capacity/diversity gain is simulated by laying out different antenna arrays in 3D space. The impact of different antenna array configurations in 3D high speed railway scenario is studied. Our results show that antenna arrays which take advantage of elevation direction provide better MIMO system performance in high speed railway scenario.

Recent Challenges and New Methods in MIMO Channel Modeling

This paper summaries the new topics about MIMO (Multiple-input-multiple-output) channel modeling. The scenarios are focused on transportation, such as VTV (Vehicle-to-Vehicle) and high speed railway. The sparse channel and time-variant channel are discussed. Afterwards, some novel methods for MIMO channel modeling are described and challenges for each method are summarized.

Impact of Mutual Coupling on LTE-R MIMO Capacity for Antenna Array Configurations in High Speed Railway Scenario

In this paper, the impact of mutual coupling on LTE-R MIMO capacity for antenna array configurations in high speed railway scenario is investigated. In order to evaluate the impact of mutual coupling for different antenna array configurations, the extended 3D clustered channel model is presented primarily in this paper. The impact of mutual coupling can be added to channel models using coupling matrix which is modeled based on S-parameters obtained from CST Microwave Studio. We study the impact of coupling on LTE-R MIMO capacity from the perspective of antenna array configurations: antenna array deployment, interelement spacing and fixed total physical space. The simulations illustrate that the impact on the capacity caused by mutual coupling is significant and differs among various antenna array configurations, which yields meaningful insight into the LTE-R antenna array configurations in high speed railway scenario.