High-speed Railway Communication Research Articles

Joint Access Control Based on Access Ratio and Resource Utilization for High-Speed Railway Communications

AbstractThe fast development of high-speed rails makes people’s life more and more convenient. However, provisioning of quality of service of multimedia applications for users on the high-speed train is a critical task for wireless communications. Therefore, new solutions are desirable to be found to address this kind of problem. Current researches mainly focus on providing seamless broadband wireless access for high-speed mobile terminals. In this paper, an algorithm to calculate the optimal resource reservation fraction of handovers is proposed. A joint access control scheme for high-speed railway communication handover scenario is proposed. Metrics of access ratio and resource utilization ratio are considered jointly in the analysis and the performance evaluation. Simulation results show that the proposed algorithm and the scheme improve quality of service compared with other conventional schemes.

Quality of service improvement for high-speed railway communications

With the fast development of highspeed railways, a call for fulfilling the notion of communication at “anytime, anywhere” for high-speed train passengers in the Train Operating Control System is on the way. In order to make a realization of that, new railway wireless communication networks are needed. The most promising one is the Long Term Evolution for Railway which will provide broadband access, fast handover, and reliable communication for high mobility users. However, with the increase of speed, the system is subjected to high bit error rate, Doppler frequency shift and handover failure just like other system does. This paper is trying to solve these problems by employing MIMO technique. Specifically, the goal is to provide higher data rate, higher reliability, less delay, and other relative quality of services for passengers. MIMO performance analysis, resource allocation, and access control for handover and various services in a two-hop model are proposed in this paper. Analytical results and simulation results show that the proposed model and schemes perform well in improving the system performances.

Delay-Aware Online Service Scheduling in High-Speed Railway Communication Systems

We investigate the downlink service scheduling problem in relay-assisted high-speed railway (HSR) communication systems, taking into account stochastic packet arrivals and quality-of-service (QoS) requirements. The scheduling problem is formulated as an infinite-horizon average cost constrained Markov decision process (MDP), where the scheduling actions depend on the channel state information (CSI) and the queue state information (QSI). Our objective is to find a policy that minimizes the average end-to-end delay through scheduling actions under the service delivery ratio constraints. To address the challenge of centralized control and high complexity of traditional MDP approaches, we propose a distributed online scheduling algorithm based on approximate MDP and stochastic learning, where the scheduling policy is a function of the local CSI and QSI only. Numerical experiments are carried out to show the performance of the proposed algorithm.

Wireless cellular network for high speed (up to 500 km/h) vehicles

In the last 25-30 years, wireless communications have become an essential part of people’s lives all over the globe. Currently, commercial high data rate mobile services are pro-vided with a peak data rate of 28Mbps using a bandwidth of 5MHz. However, this peak data rate is insufficient and even higher transmission rates are already desired, especially when multiple users and multimedia traffic are considered. The development of high-speed railway makes people’s lives more and more convenient; meanwhile, it puts forward much higher requirements on high-speed railway communication services. In this paper, the wireless cellular network for high speed train is designed that can be deployed in the environment where the passengers have speed up to 500 km/h. For this purpose, two different network architectures are designed for inside and outside the train respectively. Inside the train, the MSs are connected to the wireless access point to communicate. The APs are connected to one transceiver antenna on the top of the train by wired connections. In the outside of the train the BSs for railway is designed in a different manner. The Omni-directional antennas are used for the railway BSs for less energy consumption. The coverage area of one BS is overlapped with the nearest BS as a function of the average expected speed of the train. The railways Base Stations are connected to the BSC, MSC and PSTN as like the conventional cellular system as well as there is a point to point connection line between two adjacent BSs to transfer the control information firstly. When the train passes through the overlapping area of the cells, the handoff is occur and all the controls are transferred from the previous BS to the next BS to the moving direction of the train. For a train with maximum speed of 500 km/h we use the BS antenna that can cover an area of radius 10 km. The maximum distance between the overlapped boundary, (5*138) m= 690m (500000/3600= 138). So it will take 5 sec for a train to pass through the overlapping area. During this period of time, the handoff can occur smoothly.

Efficient Service Delivery for High-speed Railway Communications Using MIMO and Access Control Technique

In order to realize the notion of “anytime, anywhere” communication for high-speed train passengers, the Long Term Evolution for Railway is designed to provide broadband accesses and reliable communications for high-speed train passengers. However, with the increase of train speed, the system is subject to high bit error rate, Doppler frequency shift, and call drops. This paper is trying to solve these problems by employing the Multiple-Input Multiple-Output technique and access control schemes. The goal is to provide higher quality of services such as data rate, reliability, and delay for train passengers. Physical layer performance analysis and access control schemes are proposed in a two-hop model. Handovers and service types are also considered. Simulation results show that proposed models and schemes perform better in improving the quality of services.

Review of coverage and handoff technologies of 3G communication for high-speed railway

This paper focused on the environmental characteristics of High-Speed Railway(HSR) and its influence on 3rd Generation(3G) mobile communication networks.Firstly,the technical characteristics of three major 3G communication standards in China were analyzed,especially the two key issues in the construction of HSR communication system: wireless coverage and fast handoff.Then the body loss of serials of HSR,the minimum switching area and the optimization deployment strategies of 3G communication technologies in China were summarized.Lastly,the tendency of HSR's wireless communication technologies was prospected and it was found that the Long Term Evolution(LTE) technologies could provide the technical feasibility for the broadband application services of HSR.Hence,it is suggested that we should strengthen the research for wireless transmission performance optimization of TD-LTE in HSR environment.

An Improved Doppler Frequency Offset Estimation Algorithm of OFDM System under High-speed Movement Environment

Orthogonal frequency division multiplexing (OFDM) is a multi-carrier digital modulation technique. It’s likely to be used in next generation high-speed railway communication system. When OFDM is used in the communication of high-speed railway user s, Doppler frequency shift will become an important technical barrier, because OFDM is sensitive to frequency offset. Especially in high-speed movement environment, Doppler frequency shift can destroy the orthogonal characteristic between sub-carriers in OFDM system. In this paper, we analyze the performance of OFDM system in high-speed movement environment and propose a new Doppler spread estimation algorithm to improve the bit error rate (BER) performance. Theoretical analysis and computer simulations present the advantages of the proposed approach, especially under high-speed railway environment.

Fading Characteristics of Wireless Channel on High-Speed Railway in Hilly Terrain Scenario

This paper focuses on the fading characteristics of wireless channel on High-Speed Railway (HSR) in hilly terrain scenario. Due to the rapid speed, the fading characteristics of HSR channel are highly correlated with time or Transmit-Receive distance and have their own special property. To investigate the fading characteristics, the measurement is conducted on the Guangzhou-Shenzhen passenger-dedicated line in China with the speed of 295 km/h in the data-collection area at 2.4 GHz. From the measured data, the amplitude of each path is estimated by using the Subspace-Alternating Generalized Expectation-Maximization (SAGE) algorithm along with other parameters of channel impulse responses. Then the fading parameters, including path loss, shadow fading, andK-factor, are analysed. With the numerical results in the measurement and analysis, the fading characteristics have been revealed and modelled. It is supposed that this work has a promotion for HSR communication system design and improvement.

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.

Design of Data Transfer System Based on PCI Express Interface Applied in High-Speed Railway

To improve data transmission performance of the data acquisition card, a design of high-speed data transmission system is proposed in the thesis. Using FPGA of programmable logic devices, adopting Verilog HDL of hardware description language, the design of modularization and DMA transmission method is implemented in FPGA. Eventually the design implements the data transmission with high-speed through PCI Express interface. Through simulation and verification based on hardware system, this design is proved to be feasible and can satisfy the performance requirements of data transmission in the high-speed data acquisition card applied in high-speed railway communication. The design also has some value of application and reference for a universal data acquisition card.

Cooperative Access Architecture for High Speed Railway

With the great demand for broadband communication in high speed railway, new access technologies should be adapted to high mobility which brings Doppler frequency shift and fast handoff. The definition of cooperative range is presented and its influence on network connectivity is studied. The result shows that cooperation can greatly extend a wireless user’s communication range. A novel scheme of cooperative access architecture is proposed to support high-speed users with broadband communication.