Bing Hui

On Millimeter Wave and THz Mobile Radio Channel for Smart Rail Mobility

As a widely acknowledged efficient and green transportation model, rail traffic is expected to evolve into a new era of “smart rail mobility” whereby infrastructure, trains, and travelers will be interconnected to achieve optimized mobility, higher safety, and lower costs. Thus, a seamless high-data rate wireless connectivity with up to dozens of gigahertz bandwidth is required. Such a huge bandwidth requirement motivates the exploration of the underutilized millimeter (mm) wave and terahertz (THz) bands. In this paper, the motivations for developing millimeter wave and THz communications for railway are clarified by first defining the applications and scenarios required for smart rail mobility. Ray-tracing simulations at 100 GHz imply that to form high-gain directional antenna beams, dynamic beamforming strategies and advanced handover design are critical for the feasibility of THz communications to enable smart rail mobility.

Channel Characterization for Mobile Hotspot Network in Subway Tunnels at 30 GHz Band

Mobile Hotspot Network (MHN) is designed as a new communication system for high speed mobile group vehicles and aiming at providing multi-Giga bps data rate by using millimeter wave (mmWave). According to the MHN setup, the channel at 30 GHz band is simulated by a ray-tracing tool in a typical straight subway tunnel. In order to assess the system physical layer performance, system simulations based on entire channel characteristics provide an profound significance. the channel parameters such as path loss, power delay profile, decorrelation distance, Rician K-factor, Doppler characteristics, etc., are extracted and analyzed for verifying system feasibility and can serve as a guide for physical layer design.

On the high-speed railway communication at 30 GHz band: Feasibility and channel characteristics

Simulations for studying novel high-speed railway millimeter-wave radio propagation channels in urban city are presented in this paper by using verified ray-tracing tool. Based on setups of three antenna beam steering strategies at transceiver, the comparisons among these strategies are given by system feasibility and radio channel characteristics. Numerical results of the simulations are shown to illustrate that adaptive antenna beam steering could greatly improve system performances. However, jointly using fixed and adaptive beam steering is recommended as a trade off between technology implementation and channel performance. Moreover, the system effects from different distances between base station and railroad track are investigated. By selecting a reasonable distance, the detailed radio channel characteristics are extracted including delay spread and Doppler spread, which could serve as a guide for future physical layer design.

On the Feasibility of High Speed Railway mmWave Channels in Tunnel Scenario

Rail traffic is widely acknowledged as an efficient and green transportation pattern and its evolution attracts a lot of attention. However, the key point of the evolution is how to develop the railway services from traditional handling of the critical signaling applications only to high data rate applications, such as real-time videos for surveillance and entertainments. The promising method is trying to use millimeter wave which includes dozens of GHz bandwidths to bridge the high rate demand and frequency shortage. In this paper, the channel characteristics in an arched railway tunnel are investigated owing to their significance of designing reliable communication systems. Meantime, as millimeter wave suffers from higher propagation loss, directional antenna is widely accepted for designing the communication system. The specific changes that directional antenna brings to the radio channel are studied and compared to the performances of omnidirectional antenna. Note that the study is based on enhanced wide-band ray tracing tool where the electromagnetic and scattering parameters of the main materials of the tunnel are measured and fitted with predicting models.

Efficient Doppler mitigation for high-speed rail communications

Since the high-speed rail (HSR) communications are suffering from the huge Doppler shift, an efficient Doppler mitigation method is proposed in this paper. The proposed method mainly concerns about the mitigation of Doppler shift in OFDM based systems, especially for the case of employing mmWave with very high mobility. The proposed method can be used for both downlink and uplink of the system and it is quite robust to the time-varying mobility. Furthermore, the pilot-aided channel estimation for Doppler compensation is not necessary in most of the cases, which indicates the pilot density in time-domain can be reduced. Simulation results show that by using the proposed method, the residual Doppler shift can be compressed to 0 Hz with the probability of 90%.

3GPP standardization activities in relay based 5G high speed train scenarios for the SHF band

Activities related to the 3GPP high speed train (HST) scenario in the super high frequency (SHF) band are described in this paper. Communication between an onboard relay station and remote radio head placed along the railway is considered in the scenario. The content of the paper focuses on motivations for considering the scenario in 3GPP, descriptions of the HST channel model, proposed new radio (NR) technologies and evaluation results. The design elements considered in the evaluation include frame format, numerology, synchronization mechanism, reference signal design and waveform.

From architecture to field trial: A millimeter wave based MHN system for HST Communications toward 5G

This report presents a mobile hotspot network system to provide mobile Internet services for the passengers in the high speed trains. 3GPP has been working on enhanced mobile broadband under many deployment scenarios such as indoor hotspots, dense urban, rural, high speed, etc. The high speed deployment scenario deals with continuous coverage along track in the high speed trains considering mobility of up to 500 km/h. The design concept of the mobile hotspot network system is in line with the 3GPP deployment scenario. The system will eventually provide the fifth generation mobile network services based on the very wide bandwidth of millimeter waves. The designs and architecture of the system will be disclosed. Also, the performance and mobility management issue will be addressed. A proof-of-concept demonstration with the system prototype will be presented.

Creation and control of handover zone using antenna radiation pattern for high-speed train communications in unidirectional networks

In order to successfully perform the break-before-make handover for high-speed train (HST) communications in unidirectional networks, it is well agreed that the handover zone should be created. In this paper, handover zone creation and control methods are proposed. Instead of intentionally create an engineered handover zone by overlapping the coverages of adjacent cells, the nature of antenna radiation pattern is adopted for creating the proposed handover zone. The analysis and simulation results employing the system parameters of mobile hotspot network (MHN) show that the proposed handover zone can be easily controlled by setting the parameters corresponding to the antenna radiation pattern, which enables its flexible use for handover in HST communication networks.