Jiahui Qiu

Position-Based Modeling for Wireless Channel on High-Speed Railway under a Viaduct at 2.35 GHz

This paper presents a novel and practical study on the position-based radio propagation channel for High-Speed Railway by performing extensive measurements at 2.35 GHz in China. The specification on the path loss model is developed. In particular, small scale fading properties such as K-factor, Doppler frequency feature and time delay spread are parameterized, which show dynamic variances depending on the train location and the transceiver separation. Finally, the statistical position-based channel models are firstly established to characterize the High-Speed Railway channel, which significantly promotes the evaluation and verification of wireless communications in relative scenarios.

High-speed railway channel measurements and characterizations: a review

Wireless communication for high-speed railways (HSRs) that provides reliable and high data rate communication between the train and trackside networks is a challenging task. It is estimated that the wireless communication traffic could be as high as 65 Mbps per high-speed train. The development of such HSR communications systems and standards requires, in turn, accurate models for the HSR propagation channel. This article provides an overview of existing HSR channel measurement campaigns in recent years. Particularly, some important measurement and modeling results in various HSR scenarios, such as viaduct and U-shaped groove (USG), are briefly described and analyzed. In addition, we review a novel channel sounding method, which can highly improve the measurement efficiency in HSR environment.

The dynamic evolution of multipath components in High-Speed Railway in viaduct scenarios: From the birth-death process point of view

Based on the realistic channel measurement on High-Speed Railway (HSR) in viaduct scenarios at 2.35 GHz, the dynamic evolution of multipath components is investigated from the birth-death process point of view. Due to the distinction in the amount of resolvable multipath signals, the channel is divided into five segments and can be completely parameterized by several sets of statistical parameters associated with the type of environment and scenario. Then the four-state Markov chain, describing the birth-death number variation of the detected propagation waves, is employed to specialize the temporal stochastic properties. Furthermore, the steady probabilities and transition probabilities are provided which will facilitate the development and evaluation of wireless communication systems under HSR.

Resource allocation for OFDMA system under high-speed railway condition

A dynamic resource allocation algorithm is investigated for the orthogonal frequency division multiplexing access (OFMDA) system under the network architecture of High-Speed Railway (HSR). The mobile base station (MBS) on the top of the train forwards the signal received from the base station (BS) on the ground to the user equipments (UE) in the train. Due to the high mobility in the BS-MBS link, the inter-carrier interference (ICI) caused by the Doppler shift may degrade the system performance. In this paper, we aim to combat the influence of the ICI to improve the system capacity by means of the resource allocation, which includes subcarrier allocation, subcarrier pairing and power allocation. Simulation results demonstrate that the proposed resource allocation algorithm can improve the system performance dramatically.

Optimal Diversity Position over Time-Varying Rayleigh Channel with Spatial Interpolation

Doppler spread is particularly detrimental to wireless communication performance especially for transmitting a long packet. In this case, the packet experiences rapidly varying fading compared with transmitting over the static channel. To deal with this problem, the uniform linear antenna (ULA) was proposed to compensate Doppler spread. The ULA consists of a linear antenna array which can be used as space samplers to estimate a virtual point that does not move during packet transmission but without the diversity gain. In this paper, we propose the optimal time diversity position with the ULA compensator over the time-varying Rayleigh fading channel. During transmission, this scheme not only can keep the channel quasi-static but also achieve the optimal time diversity by setting the virtual diversity receiving points at zeros of the time autocorrelation function. When combined with the orthogonal space time block code (STBC), it is proved that this scheme performs even better than that over the static channel with Monte Carlo simulation.