Virtual lab based on co-simulation to include impairments of wireless tElecommunication such as GSM-R in the evAluation of ERTMS components – VEGAS

The key idea of the methodology elaborated in the VEGAS project consists in the development of a co-simulation approach based on two existing tools: an ERTMS traffic simulator designed by ERSA France and that simulates the functional subsystem, and a discreet event simulator, the OPNET simulator in which the models of the telecommunication subsystem have been implemented. A model of a GSM-R infrastructure is derived from the OPNET model of the Time Division Multiple Access (TDMA). Since the ERTMS simulator does not support pause/resume mechanisms, the co-simulation manager developed in the VEGAS project relies on the scenario running in this simulator in order to control the events simulated by OPNET. A generic co-simulation module has been developed in order to transform any node model of telecommunication component in OPNET to a node controlled by its corresponding model in the ERTMS simulator through the co-simulation manager. The proposed co-simulation protocol determines the conditions in enabling an online co-simulation, and the co-simulation manager software is able to check them at runtime. When online co-simulation is not possible, the protocol fixes how the events can be backed up and offline co-simulation is performed. In addition, offline co-simulation is able to use real-world traces of train instead of a simulated functional scenario. The VEGAS project was a basic research project coordinated by M. Berbineau from IFSTTAR. The partners are ERSA and ULCO. The project started on 01/10/2012 and ended on 31/05/2016. The project was supported by ANR with a subvention equals to 423 421 € for a total cost equals to 1 397 732.32 €.

The scientific production is one international journal, one book chapter and two international conferences. The co-simulation platform developped will be re-used within the X2RAIL-1 project in the framework of Shift2rail JU, in the WP dealing with Virtual Testing. We plan also to re-use part of the co-simulation platform in the H2020 Safe4rail Project also in the context of Shift2rail for the Innovative Programme 1. Ifsttar will cooperate in this project with a laboratory in Denmark. The aim will be also to connect real hardware devices to the simulator.

The co-simulation platform developped in the VEGAS project open the way for the development of various co-simulation approaches that will push the development of Virtual laboratories. The researches on the co-simulation platform should continue, particularly on the two simulators: (i) there is a need to increase the possible number of trains in the ERTMS scenarios (this point depends on ERSA simulator enhancement). (ii) to enhance the model for the wireless system particularly the radio propagation part and the modelling of the interferences intentional or not.

As a research project, we have disseminated the results in the scientific community. We plan to present the results and a demonstration to SNCF réseaux.

In order to harmonize the different train control systems deployed in Europe and to optimize traffic efficiency by dynamic train control, the International Union of Railway introduced the European Rail Traffic Management System (ERTMS). It relies on two major components: the GSM-R (GSM-Railway) sub-system which ensures wireless communications between the train and the control center and the functional sub-system identified as the European Train Control System (ETCS), which ensures train control by defining the signaling exchanged with control centers via the GSM-R technology. The deployment of ERTMS is mandatory along European Railway corridors through a long and expensive process. Meanwhile, both subsystems may be subject to evolutions. The impact of these evolutions should be evaluated prior to their implementation. Thus, there is a need for faster roll-out and reduction in cost for the certification and authorization necessary to put equipment into service. One of the solutions to accelerate the process relies on making intensive use of lab-testing before real deployment. In the existing ERTMS simulators, all major ETCS functionalities are implemented, but the telecommunication subsystem is not actually modeled. As a consequence, no impairments on the communication technology can be taken into account for the system evaluation.
In this context, the VEGAS project aims at designing, developing and evaluating a virtual laboratory based on co-simulation involving two kinds of simulators. The first one is an ERTMS simulator that models the functional behavior of the system. The second one is a telecommunication simulator that enables the modeling of data exchanges over the global telecommunication system architecture including any kind of telecommunication technology. The co-simulation will permit to evaluate the functional subsystem performance while taking into account the impairments related to the telecommunication subsystem, namely the GSM-R (radio propagation impairments such as bad radio links, cuts, electromagnetic interferences or attacks and also network overload).
The VEGAS lab will allow a deep study of the behavior of ERTMS components in case of specific dysfunctions or in case of an increase of traffic load in the telecommunications subsystem. With the obtained results, the railway stakeholders and the researchers will be able to elaborate specific procedures in order to reduce the impact of the dysfunctions on the lines equipped with ERTMS. Railway Industry will benefit from a tool that enables the evaluation of the impact of the dynamic telecommunication network behavior on the ERTMS performance. The virtual lab will allow defining a larger range of realistic scenarios with highly reduced costs and with an accelerated process. When several prospective technologies will be considered for an ERTMS component, the virtual lab will allow users to decide which ones are the more relevant and have to be considered for further evaluations based on trials on real sites.
The development of the VEGAS virtual lab requires a first phase to define the concepts and mechanisms for co-simulation and the development of a relevant co-simulation protocol. It will determine how specific data must be generated by each simulator, and how these data will be exchanged between the simulators. This phase will permit the development of the necessary tools to open the ERTMS simulator to other simulators. After the implementation of the telecommunication network such as GSM-R including Euroradio, it is necessary to define and to automatically generates the scenarios for tests but also to define the relevant metrics. The different modules of the VEGAS virtual lab will be evaluated with real ERTMS traces. Furthermore, the evolution towards emerging telecommunication technologies such as LTE-Advanced will be possible. At the end of the project, the recommendations for an evolution of the VEGAS virtual lab to evaluate ERTMS level 3 will be set up.