Igor Lopez

End-to-End Multipath Technology: Enhancing Availability and Reliability in Next-Generation Packet-Switched Train Signaling Systems

The migration of railway signaling systems based on circuit switching toward Internet protocol (IP) is on the way. Consequently, new strategies to promote reliability in packet-?switching networks must be studied. In this article, we propose the use of multipath technology to enhance the availability and reliability of these communications. To our knowledge, this is the first time that multipath strategies are customized for the railway train-control domain. We present the basic requirements that a multipath protocol must fulfill to increase the reliability and evaluate different related multipath proposals and provide our own customized protocol, the reliable multipath transmission control protocol (RMPTCP). Finally, we demonstrate the availability improvement that our proposed multipath strategy introduces.

SCADA Systems in the Railway Domain: Enhancing Reliability through Redundant MultipathTCP

Reliability is a key research issue to promote the role of rail in the transportation system. An important set of critical and vital railway services, such as Traction Power Supply and Supervision Systems, relay currently on modern Supervisory Control and Data Acquisition (SCADA) systems. At the same time, these large scale and networked SCADA systems are deployed over heterogeneous wide area networks. Current strategies to warrant reliability on these systems focus on costly equipment redundancy or retransmission techniques with associated delay penalization. In this paper, we propose a MultiPath strategy with redundant policy to increase reliability in railway SCADA over TCP/IP systems. We built a hybrid simulation tool with real Modbus over TCP/IP equipment and validate our approach comparing the obtained results with three alternative strategies (default TCP/IP, backup and default delivery policy).

Eurobalise-Train communication modelling to assess interferences in railway control signalling systems

The evolution of the railway sector depends, to a great extent, on the deployment of advanced railway signalling systems. These signalling systems are based on communication architectures that must cope with complex electromagnetical environments. This paper is outlined in the context of developing the necessary tools to allow the quick deployment of these signalling systems by contributing to an easier analysis of their behaviour under the effect of electromagnetical interferences. Specifically, this paper presents the modelling of the Eurobalise-train communication flow in a general purpose simulation tool. It is critical to guarantee this communication link since any lack of communication may lead to a stop of the train and availability problems. In order to model precisely this communication link we used real measurements done in a laboratory equipped with elements defined in the suitable subsets. Through the simulation study carried out, we obtained performance indicators of the physical layer such as the received power, SNR and BER. The modelling presented in this paper is a required step to be able to provide quality of service indicators related to perturbed scenarios.

Modelling and Simulation of ERTMS for Current and Future Mobile Technologies

Nowadays, train control in-lab simulation tools play a crucial role in reducing extensive and expensive on-site railway testing activities. In this paper, we present our contribution in this arena by detailing the internals of our European Railway Train Management System in-lab demonstrator. This demonstrator is built over a general-purpose simulation framework, Riverbed Modeler, previously Opnet Modeler. Our framework models both ERTMS subsystems, the Automatic Train Protection application layer based on movement authority message exchange and the telecommunication subsystem based on GSM-R communication technology. We provide detailed information on our modelling strategy. We also validate our simulation framework with real trace data. To conclude, under current industry migration scenario from GSM-R legacy obsolescence to IP-based heterogeneous technologies, our simulation framework represents a singular tool to railway operators. As an example, we present the assessment of related performance indicators for a specific railway network using a candidate replacement technology, LTE, versus current legacy technology. To the best of our knowledge, there is no similar initiative able to measure the impact of the telecommunication subsystem in the railway network availability.

A Step Up in European Rail Traffic Management Systems: A Seamless Fail Recovery Scheme

The European Rail Traffic Management System (ERTMS) is becoming a worldwide de facto standard for high-speed railway signaling. A major shortcoming of this system is that it is attached to a single radio-bearer technology, the Global System for Mobile Communications-Railway (GSM-R). The migration of ERTMS toward Internet Protocol (IP) provides the opportunity to make ERTMS unaware of the underlying communication technology by establishing train-to-ground connectivity via multiple bearers. In this article, we evaluate Multipath Transmission Control Protocol (MPTCP) integration in the ERTMS protocol stack in a test bed as a way to use heterogeneous radio bearers seamlessly and simultaneously. We validate this strategy by comparing our obtained results to the European Integrated Radio Enhanced Network (EIRENE) requirements and demonstrate its functionality as a seamless fail recovery strategy.

Towards zero on-site testing: Advanced traffic management & control systems simulation framework including communication KPIs and response to failure events

For the last five years, our research group I2T has worked with OPNET Modeler, a general purpose simulation tool, to build an integrated simulation framework for advanced railroad traffic management and control systems that includes functional and communication layers. We load in our tool the railroad network and its geographic coordinates through a terrain module. We introduce the real train graph schedule. Our simulation framework meets the subset 026 v3.3.0 UNISIG: System Requirement Specification, current ERTMS (European Rail Traffic Management System) specification for high speed lines. We deploy this train control service over different technologies (the standard technology a full stack with X.224, T.70, LAPB and GSM-R) and over TCP/IP next generation telecommunication technologies (LTE, WiMAX, WLAN). By modeling the train control service, we are able to measure how failures or degradation in the communication link affects railroad network availability and operational performance indicators. In our demonstrator, we stress the railroad communication network in different ways and check the behavior of different standardized telecom approaches. The main goal is to reduce the need for extensive field test by using this demonstrator in a laboratory.

A Framework for Vulnerability Detection in European Train Control Railway Communications

Railway systems have evolved considerably in the last years with the adoption of new communication technologies. Aiming to achieve a single European railway network, the European Rail Traffic Management System (ERTMS) emerged in Europe to substitute multiple and noninteroperable national railway communication systems. This system and its security strategies were designed in late 1990s. Recent works have identified vulnerabilities related to integrity, authenticity, availability, and confidentiality. In the context of defining effective countermeasures to mitigate potential vulnerabilities, these vulnerabilities have to be analysed. In this article we introduce a framework that attempts to challenge ERTMS security by evaluating the exploitability of these vulnerabilities.

A Multi Bearer Adaptable Communication Demonstrator for Train-to-Ground IP Communication to Increase Resilience

This paper presents the setup of a demonstrator based on Multipath TCP protocol to provide a multi bearer--WiFi and WiMAX--and resilient agnostic layer to support train-to-ground IP communication. The adaptable communication and resilient architecture consists of three main blocks: an Acquisition System, a Detection System and a Multipath Communication System. Several tests carried out with jamming devices disturbing the data transfer established between the end devices demonstrate the resilient capability and performance of the proposed architecture to overcome electromagnetic attacks.

Exploiting redundancy and path diversity for railway signalling resiliency

Railway signalling systems play a key role in the intelligent rail transportation. These systems rely on underlying communication networks that carry state information and commands between the control centre and the train fleet. These networks are currently involved in a migration process towards IP technology. Within this migration, the Multiprotocol Label Switching (MPLS) technology in communication core networks is becoming ubiquitous. Besides, in the end-side equipments, the adoption of TCP/IP protocol stack allows the introduction of new protocols, such as MPTCP, that provide end-to-end redundancy in equipments with multiple network interfaces. However, there are still two open questions before being able to introduce this technology in railway signalling networks. On the one hand, the standard Multipath TCP (MPTCP) protocol does not define how an effective redundancy can be applied in equipments with a unique network interface. On the other, redundancy without path diversity does not provide the needed resiliency for facing correlated communication errors. In this paper, we present two contributions to address these two open points. Firstly, we define and test a MPTCP extension that combines spatial and temporal redundancy. Secondly, we describe a procedure for combining MPTCP and MPLS technology in order to guarantee the required end-to-end path diversity.