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Das Kapitel befasst sich mit den Feldversuchen des 5GRAIL-Projekts und konzentriert sich auf die Validierung von 5G-Technologien für das zukünftige mobile Eisenbahnkommunikationssystem (FRMCS). Er hebt die Prüfung grundlegender funktionaler Anforderungen für Eisenbahnen hervor, einschließlich Sprach-, Daten- und Videoanwendungen. Der Text umfasst die Integration von Anwendungen wie ETCS, ATO und TCMS sowie die Nachahmung von FRMCS-Trägerflexibilität und grenzüberschreitenden Szenarien. Die Feldversuche wurden in Frankreich und Deutschland durchgeführt, wobei Prototypen sowohl in simulierten als auch in realen Umgebungen getestet wurden. Die Ergebnisse zeigen die Nutzbarkeit von 5G für den Eisenbahnbedarf und zeigen erfolgreiche Sprach- und Fernsehtests sowie Datenanwendungen mit geringen Latenzzeiten. Das Kapitel schließt mit den Gesamtleistungen des 5GRAIL-Projekts ab, wobei dessen Rolle bei der Modernisierung der Eisenbahnkommunikation hervorgehoben und der Weg für zukünftige FRMCS-Einsätze geebnet wird.
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Abstract
Railways currently use the Global System Mobile for Railways (GSM-R) for train operation across the world. The GSM-R is used for voice communication between train driver and control centres, including but not limited to, the Railway Emergency Call (REC) as well as for signalling and control messages of the European Train Control System (ETCS). Based on the fifth generation (5G) of mobile networks and in particular, 3rd Generation Partnership Project (3GPP) releases 17 and 18, the Future Railway Mobile Communication System (FRMCS) is envisioned to replace GSM-R. This modernization step does not only address administrative constraints, e.g., the upcoming 2G equipment obsolescence, but also provides an opportunity for transforming the current train operation through introduction of digitalization and automation technologies in an aim of increasing capacity and efficiency for a sustainable transport. In this paper, we present some highlights of first FRMCS Fields trials that have been realized within the 5GRAIL project which is funded by the EU Horizon 2020 program. These trials were co-led by DB Netz AG in Germany and SNCF RESEAU in France. The aim was to accomplish functional and performance testing in addition to multi-access and cross-border like scenarios. We discuss some results on the testing of the different applications before concluding with lessons-learned and outcomes.
1 Introduction
The Future Railway Mobile Communication System (FRMCS) will be the 5G worldwide standard for railway operational communications, conforming to European regulation as well as responding to the needs and obligations of rail organisations outside of Europe. A major challenge is the update by the European Railway Agency of the Technical Specifications for Interoperability of Control Command and Signalling (TSI CCS) with a full description of FRMCS with respect to interoperability functions. Therefore, the 5GRAIL project [1] aims to verify the first set of FRMCS specifications and standards (FRMCS V1) by developing and testing prototypes of the FRMCS ecosystem. The validation of the latest available railway-relevant 5G specifications will be achieved through cross-border emulation trials covering significant portions of railway operational communication requirements and including the core technological innovations for rail expected from 5G release 16 and pre-release 17 [2]. The project will first define functional tests and then work towards the development and evaluation of prototypes, for both onboard (Telecom On-board Architecture (TOBA)) and the infrastructure. The TOBA Gateway (GW) is a core element of the 5GRAIL prototyping activities as it enables multi-application support in the onboard railway communication system [3]. The railway applications include voice-specific services, such as group calls or the Railway Emergency Call (REC), the vital European Train Control System (ETCS), Automatic Train Operation (ATO) and essential additional services like Train Control and Monitoring System (TCMS) or video apps.
Prototypes will be then tested in simulated and real environments, with pilots in laboratories and in the field rolled out in various European locations (France, Hungary, and Germany), to ensure compliance and validation for FRMCS specifications, standards, and performance, and consequently guarantee the time to market for FRMCS deployments. 5GRAIL will finally deliver test report conclusions to potentially update FRMCS version 1 (v1) specifications [4, 5] and to identify implementation constraints.
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The objectives of the field trials are to provide a 5G railway field test environment to evaluate technical solutions and prototypes developed as part of this innovative 5GRAIL project. The prototypes developed and lab-tested will be integrated into real railways environment, i.e., rolling stock running on rail tracks with dedicated 5G radio coverage [6, 7], which will allow evaluation of their functionalities and performances. Field tests will demonstrate the usability of 5G to answer railways needs using railways applications and application simulators. Figure 1 illustrates the workflow in the 5GRAIL project, which is decomposed into 8 Work Packages (WPs). Testing is performed in two fields (France and Germany), each having different characteristics.
Fig. 1.
Project Decomposition and Inputs/Outputs of Field Evaluation (Image produced in Paint.net, Freeware)
Real-world 5G testing of essential functional requirements for the railways,
Evaluation of End-to-End functionality and connectivity for selected railways,
Integration of applications such as Voice via 3GPP’s mission-critical push-to-talk (MCPTT) functionalities, or ETCS, ATO, real-time Video, TCMS, etc. via 3GPP’s mission-critical data (MCDATA) functions,
Emulation of FRMCS bearer flexibility and border-crossing like scenarios.
2 Testbeds for Field Trials
In SNCF’s testbed in France, the test sites consist of a portion of commercial line in sub-urban environments in the Paris region. 5G RAN is deployed as a test network at TDD band n39 encompassing 1900 MHz-1910 MHz band [8] in three sites called: Bourbonnais, Marin and Rive, with reuse of existing GSM-R/GPRS basic infrastructure setup. The CU/DUs and 5G Core are deployed at a local command centre close to the test sites. Train speed is limited to a maximum of 70 km/h.
In DB’s testbed in Germany, 5G RAN is deployed as a test network at TDD band n78 (3.7 GHz, using 20 MHz bandwidth) in 8 sites. The 5G Core is operated remotely from a control centre located of a project partner in Hungary via a leased line. Trains run with a speed of 50–80 km/h.
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The testing is conducted in parallel in the two fields with different scopes. Some similar initial end-to-end connectivity tests are executed in both test fields to compare the results in different deployment conditions.
3 Generic End-to-End Architecture for Field Trials
The generic network architecture of the FRMCS used in the two fields is depicted in Fig. 2. The transport stratum implementing the 5G/FRMCS infrastructure is shown in light blue rectangles. It includes the network elements of the Radio Access Networks (RANs) and 5G Core Networks (5GCs) [2]. The Application and Services strata are shown within the yellow and grey rectangles, respectively. The applications use the On-board Application (OBapp) and TrackSide Application (TSapp) interfaces [5]. In case of voice applications, the mission-critical application (MCx) client is realized in the cab radio device and, hence, tight coupled. For data/video applications the MCx client is implemented in the TOBA Onboard GW following the loose-coupling principle. With 5GRAIL’s TOBA GW prototype, a parallel operation of mission-critical application with a unified FRMCS onboard system becomes possible.
Fig. 2.
Generic Network Architecture of the Field Testing of FRMCS (Image produced in Paint.net, Freeware)
Table 1 reports a list of FRMCS role in modernizing Railway Communication beyond the state of the art, with the conclusion of the field evaluation.
Table 1.
5GRAIL role in modernizing railway communication.
State of the art
After 5GRAIL
GSM-R (2G)
FRMCS (5G)
Limited capacity for railway services
Extended capacity for railway services
No bearer flexibility for railway applications
Bearer flexibility for railway applications
ETCS and ATO circuit-switched interfaces
ETCS and ATO IP interfaces
Limitations on ATO
No limitations for ATO
No possibility for video critical applications
Video for critical applications
Limitations on TCMS applications
TCMS applications
Distributed management of telecoms in train
Unified management of train communications
4 Highlights of Some Use-Cases of the Field Trials
Voice, data, and video calls as well as combined use of heterogeneous applications are successfully completed in the two fields. Below, some highlights are listed.
Voice Communication – Testing P2P Calls, Group Calls and REC (Germany)
As voice communication plays a significant role in today’s railway communications, its migration to 5G-based FRMCS is crucial. In 5GRAIL several voice services have been tested over FRMCS such as point-to-point (P2P) calls initiated by a train driver (using a cab radio) towards a train controller and vice versa, multi-train group calls with FRMCS user groups and mixed FRMCS and GSM-R user groups as well as railway emergency calls (REC) both with only FRMCS users and interworking with GSM-R. For the first time, a system transition from 2G-based GSM-R to 5G-based FRMCS with service continuation has been showcased.
Video Communication – Testing Remote Vision Combined with ETCS (France)
In the remote vision application, a real-time video is transmitted from the train front to the trackside control centres. One objective of testing the remote vision application in 5GRAIL is to add high load on the network and analyse its behaviour, including flows priority management, when multiple heterogeneous applications in term of criticality are used at the same time. In this test, the Remote Vision (RV) is used in parallel with the ETCS application simulator. Note that RV uses High Efficiency Video Coding (H.265/HEVC) adaptive codec to encode the driver’s view in the tests, as illustrated in Fig. 3. In practice, it is possible to stream 1280 × 720p (HD ready video) with full driving capacity from 800 kbps. However, the codec is usually set at 1Mbps. As adaptive, it will automatically adjust according to network conditions, as seen in Fig. 4.
Fig. 3.
Remote Driving End-to-end simulation (Image produced in Paint.net, Freeware)
5GRAIL has performed comprehensive test campaigns in the field with 6 weeks drive tests with rolling stock in France and Germany, each. Besides successfully accomplished voice and remote vision tests (as discussed above), also the data tests with ETCS, ATO and TCMS simulators have been realized. For these data applications with rather small bitrates, achieved latencies in the 5G-based FRMCS test networks have been generally low without impact on QoS of the application. This was also true for combined data application scenarios. Another test aspect of 5GRAIL’s video testing was the real-time streaming of in-cabin video from train to ground (uplink) as well as the offload of CCTV files to trackside servers. For the latter one, a transition between two different 5G bearers has been realized as inter-frequency handover between 5G sub-bands with different TDD patterns and, hence, different achievable uplink bitrates.
5 Conclusion
In this paper, we have presented some highlights of the functional and performance testing accomplished as part of the field tests in the 5GRAIL project. This project allowed the railway ecosystem to validate 5G technologies and 5G standalone architecture for a connected and automated mobility (CAM) context. Moreover, it allowed to validate 5G systems to support advanced FRMCS use-cases such as real-time video. 5GRAIL is the first large-scale FRMCS prototyping project. This project is the first step towards FRMCS. Further projects are currently following.
Acknowledgement
The project “5G for future RAILway mobile communication system” (5GRAIL) has received funding from EU’s Horizon 2020 research and innovation program under grant agreement No. 951725.
Open Access This chapter is licensed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made.
The images or other third party material in this chapter are included in the chapter's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the chapter's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.
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