Guangkai Li

On Indoor Millimeter Wave Massive MIMO Channels: Measurement and Simulation

The millimeter wave (mmWave) communications and massive multiple-input multiple-output (MIMO) are both widely considered to be the candidate technologies for the fifth generation mobile communication system. It is thus a good idea to combine these two technologies to achieve a better performance for large capacity and high data-rate transmission. However, one of the fundamental challenges is the characterization of mmWave massive MIMO channel. Most of the previous investigations in mmWave channel only focus on single-input single-output links or MIMO links, whereas the research of massive MIMO channels mainly focus on a frequency band below 6 GHz. This paper investigates the channel behaviors of massive MIMO at a mmWave frequency band around 26 GHz. An indoor mmWave massive MIMO channel measurement campaign with 64 and 128 array elements is conducted, based on which, path loss, shadow fading, root-mean-square (RMS) delay spread, and coherence bandwidth are extracted. Then, by using our developed ray-tracing simulator calibrated by the measurement data, we make the extensive ray-tracing simulations with 1024 antenna elements in the same indoor scenario, and get insights into the variation tendency of mean delay and the RMS delay with different array elements. It is observed that the measurement and the ray-tracing-based simulation results have reached a good agreement.

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.

Channel characteristics analysis in smart warehouse scenario

Industry 4.0 aims to connect internet to industry, makes the factories more conomic, efficient and smart. In this paper we focus the study on the wireless channel characteristics in smart warehouse at 5.8 GHz, which is a typical scenario of industrial 4.0 at ISM band. we build a smart warehouse scenario in 3D mode, simulate the channel by using ray-tracing method. The main energy in the channel comes from the direct path, and most multi-paths are continuously varying in the mobile channel.

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.

Determination of Cell Coverage Area and its Applications in High-Speed Railway Environments

In this paper, a determination method of the cell coverage area for the narrow-strip-shaped cells in high-speed railways (HSRs) is proposed, which is of great importance to HSR dedicated communication network planning. A closed-form expression for the cell coverage area is first derived on the basis of the edge outage probability and the propagation channel parameters, and it is found that the linear coverage in HSRs has a higher percentage of coverage area than the traditional circular coverage of cellular systems. For the convenience of link budget computation, we also present a family of curves related with the percentage of linear coverage. Then, the implementation of the proposed determination of cell coverage area is presented, and it is found that the linear cell of HSRs has a larger maximum communication distance than circular coverage. Furthermore, the impact of frequency on the HSR link budget is investigated, and the results show that a lower frequency band reduces the number of the required base stations. The results can be used in designing and optimizing the wireless coverage and the communication network planning of HSR communications.

An accelerated algorithm for ray tracing simulation based on high-performance computation

Ray tracing tool has played an important role in communication channel modeling. However, accurate simulation with complex scenario will greatly challenge the computational capabilities of personal computer. In this paper, a novel accelerated algorithm for traditional ray tracing tool was proposed based on high-Performance distribute computers. The comparison between traditional ray tracing tool and extended ray tracing tool shown that the accelerating performance for later is highly significant. Numerical results of the simulations show that, jointly using ray tracing tool and high performance distribute computers have been illustrated to be high efficient way for high accurate simulation of channel.

mmWave massive MIMO channel modeling

An in-depth understanding of propagation and channel is of great importance for the simulation and design of mmWave massive multiple-input multiple-output (MIMO) systems. However, so far there has not been any official or widely acknowledged mmWave massive MIMO channel model, either in academia or in the industry. Thus, in this chapter, we first survey and highlight the main distinguished features of mmWave massive MIMO channels in terms of three layers: propagation mechanisms, static channel, and dynamic channel. Furthermore, this chapter introduces and discusses the state-of-the-art of mmWave massive MIMO channel modeling and sounding, respectively. Even though the current available measurements or models for mmWave massive MIMO channels are still very limited, many researchers have been making efforts toward a general and standard channel model that can effectively guide system design for beyond 5G.

Scattering studies on sorted materials of high-speed rail scenario for propagation channel simulations

The accurate deterministic modeling for wireless channel is required tools especially at high frequency, such as ray tracing which can be regarded as a superposition of the line-of-sight (LOS), reflected, diffracted, scattered rays. In this study, we fully investigate the constructive materials in high speed railway scenario in the first place, and extract the dominant materials for scattering character measuring. The measurement campaign is well design for future deducing material permittivity and development of scattering model of these materials.