High-speed Railway Scenario Research Articles

TDD-based mobile communication solutions for high-speed railway scenarios

Mobile communication solutions for highspeed railway scenarios aim at providing seamless coverage, high system capacity and a high data rate for end users, which in turn face the challenges of Doppler frequency shift, penetration loss, mobility management and system capacity planning. Because the scarcity of frequency resources and increasing wireless broadband requirements have become very serious problems worldwide, increasing attention has been focused on time-division duplexing based technology, on which we focus in this article. Time-division synchronous code-division multiple access based and time-division Long Term Evolution based solutions are introduced with appropriate technology analysis. The experimental results of TD-SCDMA-based solutions in the Shanghai maglev high-speed network environment and the simulation results of TD-LTE-based solutions are presented. Finally, to improve performance, we discuss an enhanced solution based on mobile relays with performance evaluation, which is considered as a more comprehensive solution for high-speed railway scenarios.

Impact Analysis of Layer 3 Filtering on LTE Handover Performance in High-speed Railway Scenario

Handover (HO) which can make user equipment (UE) communicate with the eNodeB (evolves NodeB) with the highest signal quality will have bad performance in high-speed railway scenario. In this paper, detailed introduction is made on Layer3 (L3) filtering theory to help solve this problem. HO measurement and HO decision procedure based on L3 filtering are designed and implemented in a dynamic system level simulation platform modeling two kinds of radio channel environmentmountainous and rural scenario. The Reference Signal Received Power (RSRP) of source and target eNodeB has been simulated to research and achieve proper L3 filtering strategy. Ping-pong HO rate and radio link failure (RLF) rate have been investigated to verify the influence of L3 filtering to HO performance. Simulation results show that the best L3 filtering factor is 1/6 and its impact on Pingpong HO rate and mountainous scenario is greater than on RLF rate and rural scenario.

Outage Analysis of Train-to-Train Communication Model over Nakagami-mChannel in High-Speed Railway

This paper analyzes the end-to-end outage performance of high-speed-railway train-to-train communication model in high-speed railway over independent identical and nonidentical Nakagami-mchannels. The train-to-train communication is inter-train communication without an aid of infrastructure (for base station). Source train uses trains on other rail tracks as relays to transmit signals to destination train on the same track. The mechanism of such communication among trains can be divided into three cases based on occurrence of possible-occurrence relay trains. We first present a new closed form for the sum of squared independent Nakagami-mvariates and then derive an expression for the outage probability of the identical and non-identical Nakagami-mchannels in three cases. In particular, the problem is improved by the proposed formulation that statistic for sum of squared Nakagami-mvariates with identicalmtends to be infinite. Numerical analysis indicates that the derived analytic results are reasonable and the outage performance is better over Nakagami-mchannel in high-speed railway scenarios.

A Handover Algorithm for LTE System based on the Target Cell Pre-Bearer in High-speed Railway Environment

Abstract This paper evaluates the handover performance of an optimized A3 event handover algorithm of LTE system, which is based on the target cell pre-bearer procedure in the high-speed railway (HSR) scenario. The paper introduces this handover algorithm and the handover signaling procedure based on the target cell pre-bearer procedure. These have been designed and implemented in a dynamic system level simulator and have been studied to select different handover parameter sets for HOM (Handover hysteresis margin) and TTT (Timeto-Trigger) in the different velocity interval of the UE (User Equipment) for the high-speed railway simulation scenario. The different HOM and TTT parameters have been simulated in a dynamic system level simulation platform and have been investigated the influence to radio link failure (RLF) via the simulation. The results suggest that this kind of handover algorithm has better handover performance in the velocity internal 250km/h and 350km/h.

A highly efficient channel sounding method based on cellular communications for high-speed railway scenarios

An efficient channel sounding method using cellular communication systems is proposed for high-speed railway (HSR) propagation environments. This channel measurement technique can be used conveniently to characterize different HSR scenarios, which can significantly improve the measurement efficiency. Based on downlink signals of wideband code division multiple access (WCDMA) and the long term evolution (LTE), principles and methodologies of HSR channel sounding are presented. Using the WCDMA signal, a measurement campaign is conducted in real-world HSR scenarios and statistical characterizations are provided using a radio network analyzer. Due to the limits of the radio network analyzer, afterwards, a software defined radio (SDR)-based channel data recorder is developed allowing users to collect the signals from different wireless cellular systems. Especially, the estimation accuracies are validated in lab by the faded signals emitted from a vector signal generator. The results show that the channel data recorder provides a particularly good match to the configured fading channels. Therefore, this measurement method can be employed to investigate the HSR channel, and to establish the channel models under the various HSR scenarios.

Construction and Capacity Analysis of High-Rank LoS MIMO Channels in High Speed Railway Scenarios

The validity of the maximum capacity criterion applied to realize high-rank line-of-sight (LoS) multiple-input multiple-output (MIMO) channels is investigated for high speed railway scenarios. Performance is evaluated by ergodic capacity. Numerical results demonstrate that by simply adjusting antenna spacing according to the maximum capacity criterion, significant capacity gains are achievable. We find relatively low sensitivity of the system to displacements from the optimal point and angle in relatively short range. Thus, we present two proposals to reconfigure antenna arrays so as to maximize LoS MIMO capacity in the high speed railway scenarios

A Novel Train-to-Train Communication Model Design Based on Multihop in High-Speed Railway

Railway telematics applications are currently attracting attention and are under intense research. Reliable railway telematics applications increasingly tend to require a subsidiary means to help existent control system make train operation safer and more efficient. Since 2006, train-to-train communication has been studied to respond to such requirements. A key characteristic of train-to-train communication is that operation control to avoid possible accidents is conducted among trains without help of a base station. This paper proposes a novel train-to-train communication model in a physical layer based on multihop and cooperation, taking a high-speed railway propagation channel into account. The mechanism of this model lies in the idea that a source train uses trains on other tracks as relays to transmit signals to destination train on the same track. Based on occurrence of these potential relays, such mechanism can be divided into three cases. In each case, BER is applied to evaluate properties of the proposed communication model. Simulation results show that BER of the train-to-train communication model decreases to10−6when SNR is 10 dB and that the minimum receiving voltage of this model is −84 dBm, which is 8 dBm lower than the standards established by the International Union of Railways (UIC) in a high-speed railway scenario.