Railway Communication Systems Research Articles

Integrating 5G and Terrestrial Trunked Radio into Railway Communication System for Railway Safety and Information Security

Integrating 5G and Terrestrial Trunked Radio into Railway Communication System for Railway Safety and Information Security

EMI and IEMI Impacts on the Radio Communication Network of Electrified Railway Systems: A Critical Review

The electrified railway system has been rapidly rolled out in many countries and regions in the past decades, along with the transportation decarbonization agenda. The latest development in power electronics and electrical railway systems has increased the risks of electromagnetic interference (EMI) and intentional EMI (IEMI) emissions, introducing new challenges to the railway radio communications network. It is vital to have a robust and reliable railway communication network that can be resistant and immune to these interferences for the safe and efficient operation of modern railway systems. Yet, the source and new features of EMI and IEMI emerging along with the latest technological development have not been thoroughly investigated and understood. This review paper aims to fill the research gap. First, railway communications systems are introduced. The EMI and IEMI are discussed at the whole system level, and the corresponding impacts on the signaling and communication systems are reviewed comprehensively. Current electromagnetic compatibility (EMC) methods are surveyed, and challenges of tackling the impacts of EMI and IEMI on the signaling and communication systems are discussed. Finally, future research directions are outlined.

RIS-Aided Hybrid Precoder Design With Anti-Blocking Scheme in High-Speed Railway

Reconfigurable intelligent surface (RIS)-aided high-speed railway (HSR) communication system is an efficient and promising way to slove the signal blocking by tuning passive signal reflection or refraction. However, the complexity HSR environment lead unstable communication links and low quality of service. Therefore, this paper studies a RIS-aided hybrid precoding for anti-blocking HSR network to enhance the sum rate of mobile relays when signal blocking. To describe the blocking scenes clearly, the blocking model is established and the closed form of the blocking probability is derived. Based on the blocking model, the non-convex blocking optimal problem is decoupled by the block coordinate descent method with the jointly optimization problem about hybrid precoder and reflect angle matrix of RIS. Then, the successive convex approximation and prox-linear method are utilized to solve the constant modulus constraint of RIS and hybrid precoding constraints. Simulation results show that the proposed RIS-aided anti-blocking hybrid precoding scheme can achieve higher sum rate than the traditional methods in blockage scenarios. Moreover, the proposed algorithm brings better performance of blocking probability and outage probability in high-speed scenarios.

5G for Railways: Next Generation Railway Dedicated Communications

To overcome increasing traffic, provide various new services, further ensure safety and security, and significantly improve travel comfort, a new communication system for railways is required. Since 2019, public networks have been evolving to fifth generation (5G) communication worldwide, whereas the main railway communication system is still based on second generation (2G) communication. It is thus necessary for railways to replace the current 2G-based technology with the next generation railway dedicated communication system with improved capacity and capability, and the 5G for railways (5G-R) technology is a promising solution for further intelligent railways. This article gives a review of the current developments of next generation railway communications, followed by a discussion of the typical services that 5G-R can provide to intelligent railways. Then the main application scenarios of 5G-R are summarized, and system configurations are compared. Some key technologies of 5G-R such as network architecture, massive MIMO, millimeter-wave, multiple access scheme, and ultra-reliable low-latency communication are presented and analyzed. Finally, some challenges of 5G-R are highlighted.

Coverage Analysis for Cell-Free Massive MIMO High-Speed Railway Communication Systems

In traditional cellular framework, the frequent handoff is one of the main factors that affect the performance of high-speed railway (HSR) communication systems. The cell-free massive multiple input multiple output (MIMO) is proposed as a promising technique for the antenna point (AP) deployment of HSR communication systems. This paper investigates the coverage performance of the cell-free massive MIMO HSR communication systems with multiple APs and multiple users. Initially, the system and channel models are proposed. Based on the established models, the uplink training, uplink data transmission and downlink data transmission are analyzed, respectively. By using the deterministic equivalent analysis, we derive a deterministic signal-to-interference-plus-noise ratio expression for downlink transmission. Then, a tight upper bound on the coverage probability is derived. In the high power regime, the asymptotic coverage performance is also analyzed. Numerical results verify the correctness of the derived theoretical expressions. Moreover, the effects of the downlink transmit power, AP’s antenna number, AP’s density, user number, and channel fading parameter on coverage performance are also discussed.

Neural Network-Based Multi-DOA Tracking for High Speed Railway Communication Systems

Along with the rapid development of high-speed railway (HSR), it is of vital importance to explore new technologies to meet the stringent requirements on wireless transmission latency and reliability in such high mobility scenarios. To address this, fast beamforming schemes with precise direction-of-arrival (DOA) can achieve effective channel gain and improve interference mitigation. In this paper, we propose a novel radial-basis function neural network (RBFNN)-based method for the multi-DOA tracking, in which the RBFNN is trained by the location-based prior information. Consequently, the DOA tracking problem is transformed into an RBFNN with trained input/output pairs. The effectiveness of the proposed scheme in terms of complexity and accuracy is verified by simulation results. Finally, the impact of the shapes of the array on estimation accuracy is also discussed.

Coverage Analysis and Chance-Constrained Optimization for HSR Communications With Carrier Aggregation

This paper investigates coverage analysis and performance optimization for a high-speed railway (HSR) communication system with carrier aggregation (CA). Initially, the system model is established. By using CA technology, the statistical characteristic of the received signal-to-noise ratio (SNR) is obtained. Then, for the systems with or without CA, unified theoretical expressions for the edge coverage probability (ECP) and the percentage of cell coverage area (CCA) are obtained, respectively. After that, a chance-constrained coverage optimization is proposed to improve the coverage performance, which is effectively solved by using a heuristic algorithm. Numerical results show that the derived expressions of the ECP and the percentage of CCA are accurate and can be directly used to evaluate the coverage performance without time-intensive simulations. Moreover, the impacts of CA, transmit power, cell radius, received SNR threshold, HSR scenario on coverage performance have been discussed. Furthermore, the effectiveness of the proposed coverage optimization scheme is also verified.

Scheduling of UAV-Assisted Millimeter Wave Communications for High-Speed Railway

To exploit richer spectrum resources for even better service quality, millimeter wave (mmWave) communication has been considered for high-speed railway (HSR) communication systems. In this paper, we focus on scheduling as many flows as possible while satisfying their QoS requirements. Due to interference, eavesdropping, or other problems, some flows may not be directly transmitted from the track-side BS. In this paper, we propose an UAV-assisted scheduling scheme which utilizes a UAV to serve as relay for such flows. The proposed scheme also utilize two mmWave bands, one for the BS links and the other for the UAV links. The proposed algorithm aims to maximize the number of flows with their QoS requirements satisfied. Simulations demonstrate that the proposed scheme achieves a superior performance on the number of completed flows and the system throughput over two baseline schemes.

High mobility transmission system under intelligent reflecting surface

AbstractIn wireless communication system with a high mobility scenario, there is a challenge to obtain fast data transmission service with proper stability. Also, it is difficult to obtain perfect channel state information in the high mobility case without large online computation. Intelligent surface has great potential to cost‐effectively enhance the system performance in next generation technology and beyond. In this paper, a railway communication system with the help of intelligent surface technology is proposed for high mobility scenario. We propose an applicable beamforming scheme with the help of mobile station location information for intelligent surface‐aided communication system under high mobility. In our proposed system, the beams from the intelligent surface are chosen based on the mobile stations locations, where the weights of the beams are optimized for maximum total service of base station. Also, we formulate the optimization problem and propose an alternating iterative technique as a solution. The weights and phase matrix of the beams are optimized to maximize the mobile service. An intelligent surface with beam selection scheme is also proposed. Results demonstrate the significant mobile service enhancement introduced by the intelligent surface in railway communication system and show the effectiveness of our proposed scheme. It can reduce the handover region and can save time for data transmission.

Physical Layer Enhancement for Next-Generation Railway Communication Systems

This paper presents an overview of the challenges and state-of-the-art physical layer enhancement designs for next-generation railway communication, also known as high-speed train (HST) communication. The physical layer design for the HST should adapt from its counterpart in the general-purpose network because of the harsh propagation environment and extreme conditions, stringent latency and reliability requirements of dedicated railway applications, and frequency band scarcity caused by regulation. In this survey, we examine how conventional multiple-input-multiple-output (MIMO) family techniques such as beamforming, multi-cell MIMO, and relays can enhance the physical layer performance for HST. Physical layer enhancement assisted by novel reconfigurable intelligent surface (RIS) technology was also analyzed from different perspectives. Dedicated control channels, reference signals, waveforms, and numerology designs for train-to-infrastructure (T2I) and train-to-train (T2T) communication in sidelinks are also reviewed. Finally, a brief introduction to artificial intelligence (AI)/machine learning (ML)-aided HST physical layer design is provided. Several promising research avenues have also been suggested.

Latency-aware secure transmission in MEC-assisted HSR communication systems

Mobile edge computing can provide short-range cloud computing capability for the mobile users, which is considered to be a promising technology in 5G communication. The mobile users offload some computing tasks to the edge server through the wireless backhaul link, which can reduce the energy consumption and the time latency. Meanwhile, due to the open characteristics of the wireless channel, the offloading tasks through the backhaul link may face the risk of eavesdropping. Therefore, the secure transmission based on physical layer security for the offloading tasks to the edge server is considered. The optimization problem of minimizing the energy consumption for the vehicular stations (VSs) in mobile edge computing-assisted high-speed railway communication system is studied in this paper. The energy consumption of the mobile users is generated by executing the local computing task and by transmitting the partial offloading task to the edge server. In this paper, a novel joint iterative optimization algorithm is proposed. By jointly optimizing the task scheduling, the task offloading and the transmission power, the energy consumption of all VSs is minimized under the constraint of the time latency. Numerical simulation results verify the effectiveness of the proposed algorithm.

Joint optimization of BS-VS association and power control in secure HSR communication systems

In this paper, the secure transmission for high-speed railway (HSR) communication system is studied. The considered HSR wireless communication system consists of a macro base station, B roadside base stations, and K vehicle stations (VSs) on the top of the train, and the eavesdropping user is a mobile unmanned aerial vehicle (UAV). We consider maximizing the sum of the minimum security rate of each time slot as the objective function, and the constraint conditions contain the quality of service (QoS), switch requirements and the total power constraint. The original optimization problem is mixed-integer and non-convex, it is intractable to solve directly. The block coordinate descent (BCD) method is applied, and the original problem can be decoupled into two sub-problems. The one is the joint BS-VS association problem, and the other is the power control problem. The first sub-problem of optimizing BS-VS association can be solved by the successive convex approximation (SCA) algorithm, and the second one of optimizing transmit power can be solved by the lagrangian dual method. Simulation results show that the proposed algorithms have good convergence.

Multi-feature fusion for high-speed railway propagation scene recognition based on LSTM networks

In order to fulfill the requirement of service quality of the 5G system, we consider multi-feature fusion methods in this paper to recognize the propagation scene of high-speed railway precisely. After that, the performance of system is improved by using some adaptive technologies. Firstly, we make an explanation on propagation scenes and channel feature parameters, and the dataset is split into two sets: training set and testing set. Then we propose a multilayer long short term memory(LSTM) architecture with a novel weighted score fusion scheme to learn classification from different propagation scenes and compare the results with usage of three regular fusion schemes. The result shows that the recognition accuracy of proposed model on testing dataset reaches 92.2%, the area under curve(AUC) of this model is better than the other three fusion schemes. Therefore, the proposed method provides an accurate recognition application for high-speed railway communication systems.

COMPARATIVE ANALYSIS OF COMPACT METHODS REPRESENTATIONS OF GRAPHIC INFORMATION

The main characteristics of graphic information compression methods with losses and without losses (RLE, LZW, Huffman's method, DEFLATE, JBIG, JPEG, JPEG 2000, Lossless JPEG, fractal and Wawelet) are analyzed in the article. Effective transmission and storage of images in railway communication systems is an important task now. Because large images require large storage resources. This task has become very important in recent years, as the problems of information transmission by telecommunication channels of the transport infrastructure have become urgent. There is also a great need for video conferencing, where the task is to effectively compress video data - because the greater the amount of data, the greater the cost of transmitting information, respectively. Therefore, the use of image compression methods that reduce the file size is the solution to this task. The study highlights the advantages and disadvantages of compression methods. The comparative analysis the basic possibilities of compression methods of graphic information is carried out. The relevance lies in the efficient transfer and storage of graphical information, as big data requires large resources for storage. The practical significance lies in solving the problem of effectively reducing the data size by applying known compression methods.

RELIABILITY CHARACTERISTICS OF RAILWAY COMMUNICATION SYSTEM SUBJECT TO SWITCH FAILURE

In the present study, a railway communication system (RCS) reliability model is developed based on system failure. The proposed RCS has control centre and stations which are arranged in such a manner that failure of control centre or a single station stops the working of overall system i.e., all switches must be working for communication to be available. To improve the reliability of the proposed communication system, a ring architecture is employed. In this architecture one additional communication path is connected in parallel configuration. Provision of two path of communication ensures that failure of one path will not cause a communication failure and communication will be available through additional path. All failures of RCS are exponentially distributed. Mathematical modelling of the system is carried out using Markov process by which the differential equations are generated. These differential equations are further used to evaluate the reliability measures like availability, reliability, mean time to failure of the proposed RCS. Likewise, sensitivity analysis is done to determine the impact of failures on RCS’s performance measures. The proposed Markov process-based model gives the information about the failure and working of the multi- state railway communication system. Finally, numerical results are provided with graphs to demonstrates the usefulness of the findings.

Railway communication system; Reliability; Mean time to failure; Markov process; Sensitivity

Policy-making is an undeniable decision-making process in every company where different kinds of decisions are taken based on different goals and preferences in each vision. “Prospective Multiple Attribute Decision Making (PMADM)” is one of the well-known decision-making frameworks that have been used as a flexible decision-making tool for developing policies and making future decisions over different periods. This study presents a multi attribute problem with three different visions where a decision-making process is required for each vision in order to prioritize the potential set of alternatives. Evaluation Based on the Distance from the Average Solution (EDAS) is used as a MADM model to show the applicability and feasibility of the PMADM framework. A vision-based weighting system (ViWeS) prepares a new opportunity to take proper decisions in different visions and time requirements. This research is analyzed three-time vision (Current, 2025, and 2030) and showed by changing the time, the rank of the alternatives also is changed. In numerical example is indicated in the current vision, Alternative 5 gets rank one and alternative six get rank 2, for 2025 vision, the rank one and two don’t change, and in vision 2030, the rank of one does not change, but the rank of second change from Alternative 6 to 3.

Cyber Resilience Meta-Modelling: The Railway Communication Case Study

Recent times have demonstrated how much the modern critical infrastructures (e.g., energy, essential services, people and goods transportation) depend from the global communication networks. However, in the current Cyber-Physical World convergence, sophisticated attacks to the cyber layer can provoke severe damages to both physical structures and the operations of infrastructure affecting not only its functionality and safety, but also triggering cascade effects in other systems because of the tight interdependence of the systems that characterises the modern society. Hence, critical infrastructure must integrate the current cyber-security approach based on risk avoidance with a broader perspective provided by the emerging cyber-resilience paradigm. Cyber resilience is aimed as a way absorb the consequences of these attacks and to recover the functionality quickly and safely through adaptation. Several high-level frameworks and conceptualisations have been proposed but a formal definition capable of translating cyber resilience into an operational tool for decision makers considering all aspects of such a multifaceted concept is still missing. To this end, the present paper aims at providing an operational formalisation for cyber resilience starting from the Cyber Resilience Ontology presented in a previous work using model-driven principles. A domain model is defined to cope with the different aspects and “resilience-assurance” processes that it can be valid in various application domains. In this respect, an application case based on critical transportation communications systems, namely the railway communication system, is provided to prove the feasibility of the proposed approach and to identify future improvements.

Communication systems of high‐speed railway: A survey

AbstractModern railway services are required to deliver good quality services to the passenger throughout the whole journey. These include improved performances, safety, and reduce delays. There is also the requirement for in‐train customer experience such as infotainment and access to reliable communication systems. The railway industry has employed different types and generations of communication systems in recent times. Signaling systems were used at the early stage of the railway services. Today, communication systems such as the second‐generation communication system, also known as the global system for mobile communications (GSM), the Third‐generation (3G) and the Fourth‐generation (4G) are utilized in the railway industry. In this paper, we present a brief history of railway communication systems, their features and applications. In addition, we discuss the technical challenges and potential solutions of in‐train communication systems and how data can be distributed on‐board and between the train coaches using state of the art and hybrid communication technologies.

Channel Models for Performance Evaluation of Wireless Systems in Railway Environments

In the automotive and rail domains, vehicles are entering the era of full automation thanks to wireless sensors and communication systems, shifting control functions from a human driver to computers. High data rate, robustness, high reliability and ultra-low latency wireless communications are required in the context of autonomous train and safety critical applications. Today, the Future Railway Mobile Communication System (FRMCS) is under development at European level within the International Union of Railways (UIC). This system will answer all the current and future needs of rail. It will be IP based, multi-bearer and resilient to technology evolution. In the context of the development of different FRMCS prototypes by industry, it is crucial to be able to test them in representative Railway radio environments thanks to laboratory tools. Characterization of radio channels in railway environments, by measurements or simulations, is a very active field. In this article, based on broad literature survey, we show that not all the published models are suitable for performance evaluation. Then, we propose a selection of typical Tapped-Delay-Line channel models to be implemented in an original hardware and software testing platform capable to reproduce the effect of representative Railway environments in laboratory, with real time emulation at RF (Radio Frequency) level. Preliminary results in Hilly 3 taps and Cutting 5 taps channel models are presented as a proof of concept of a “zero on site testing” approach, allowing for time and cost savings in the validation of railway communication systems.

A Dynamic 3-D Wideband GBSM for Cooperative Massive MIMO Channels in Intelligent High-Speed Railway Communication Systems

Coordinated multipoint (CoMP) and massive multiple-input multiple-output (mMIMO) are two of promising technologies in future intelligent high-speed railway (HSR) communication systems, whose performance is fundamentally determined by the characteristics of cooperative mMIMO channels. This article proposes a dynamic three-dimensional (3-D) wideband geometry-based stochastic model (GBSM) for HSR cooperative mMIMO channels. The proposed GBSM employs a sphere model and two elliptic-cylinder models to describe common and uncommon clusters for different links, and integrates the dynamic cluster evolution in both time and array domains. Statistical properties of the cooperative mMIMO model are investigated, such as multi-link spatial cross-correlation function and sum rate capacity. A corresponding dynamic 3-D wideband simulation model for the HSR cooperative mMIMO channel is also proposed. Finally, numerical results of the statistical properties are analyzed, and the proposed model is validated by realistic HSR channel measurement data, in terms of dual-link spatial cross-correlation and channel capacity. This model is more practical and will be helpful for facilitating the design and performance evaluation of future intelligent HSR communication systems.