GSM-R in France

Many railway operators have decided to implement ground-to-train radios on their networks in the fourth quarter of the 20th century, which was, for most of them, variants of a UIC specific analogue technology. In order to anticipate the upcoming obsolescence of this existing radio and having in mind the objective to improve interoperability of railway operations all over Europe, the UIC took action in the early 1990s in order to determine which new technology could be specified and promoted.

Hence, the MORANE initiative has then been defined for that purpose, and the result of its technical evaluation has been to select GSM, actually an evolution of GSM available at that time, named GSM-R, with the ‘R’ standing for ‘Railway’. The reasons for such a choice were the following:

• GSM-R is based on the widely known GSM. It is a standard and by no means a new additional specific choice
• The ‘R’ of GSM-R covers the fact that:
  • The radio frequencies used are close to the GSM ones but dedicated to railway operators. Therefore, GSM-R radio products are globally inherited from GSM products with a slight adaptation to support the specific 4 Mhz wide frequency band
  • Some PMR-like features are added to GSM specifications in order to deal with the railway functional requirements. In terms of products, this means that some software variants are required
• GSM-R is a digital technology which can support any data applications in addition to voice applications

By the end of the 1990s, a first set of GSM-R specifications had been completed to form a standard named ‘EIRENE’, which is one of the numerous chapters of the Technical Specifications for Interoperability (TSIs).

As for GSM, the European Union requires GSM-R to be implemented all over Europe, which means that:

• Railway infrastructures have to be upgraded to GSM-R within a certain timeframe. This brings some constraints, including:
  • The speed of deployment is undoubtedly different from one country to another
  • Within one country, until deployment is complete, transitions between technologies must be managed
• One of the two following migration schemes must be implemented:
  • Mobile-oriented: all engines are to be equipped with mobiles – CAB radios – which can support both GSM-R and the legacy system (analogue technology)
  • Network-oriented: engines are equipped with CAB radios operating in a single mode only, GSM-R or the legacy analogue radio. GSM-R and analogue networks are then operated in parallel on a given line until the whole cab radio migration is complete

GSM-R services

GSM-R services have been designed to fulfil the functional requirements of:

• The dispatchers, whose role is to manage the railway traffic
• The drivers, whose role is to perform their trip in a secured way

The services include quite conventional mobile telecom features and some features targeting the railway needs are added, including:

• Group calls including mobiles and dispatchers; a specific and essential group call is the REC (Railway Emergency Call)
• Priorities and Pre-emption: EIRENE specifications assign a priority based on call types. This allows calls to be arbitrated based on priorities in case of congestion or and pre-empt a call of lower priority when a call with higher priority can not be served. Such a mechanism guarantees that calls of the highest priorities, usually those related to the safety of operations, are always completed
• Functional Numbering: a specific addressing plan is defined which allows users to designate targets by their functional number. For example, a train shall be called by the train journey number (rather than the 10-digit mobile number) which is the number known to operate the train
• Location Dependant Addressing: for a train, the functional need is to reach in the quickest way the ‘local dispatcher’ or ‘the regional dispatcher’ responsible for the given area where the train is located using a single key stroke

In addition, GSM-R has been chosen by standardisation groups to be the transmission layer for ETCS (European Train Control System) the new railway signalling technology promoted by the EU. The application layer, split between the trackside equipment (the RBCs) and the on-board equipment (the EVCs), uses the GSM-R radio to exchange information through data calls. Currently, switched circuit data calls are used. Studies are underway to check whether GPRS (packet-switched data exchanges over the air) could be a possible bearer in the future which would allow the media capacity to be increased.

GSM-R in France

Context and assumptions

It is worth noting that the French Authorities created Réseau Ferré de France (RFF) in 1997 to own and develop the railway network.

SNCF, in addition to being a Train Operating Company, also has the RFF delegation for the network operation and maintenance.

Regarding the GSM-R infrastructure project, RFF is the operator and the project owner. It defines objectives, secures the funding from Public Authorities and drives the organisation in charge of the network implementation.

In the early 2000s, the status of ground-to-train radio deployment was the following:

• Around 14,000km of lines were equipped with ground-to-train analogue radio, among which were 1,800km of high-speed lines (HSL) and 12,200km of conventional lines
• Around 8,300 SNCF engines were equipped with analogue CAB radios and must be upgraded to GSM-R in parallel with the network upgrade

Following a preliminary study, the ‘single infrastructure-double mobile’ strategy was chosen for the following safety reasons:

• ‘Single infrastructure’ means that at a given time, for a given line, only one radio technology will be used for dispatchers
• ‘Double mobile’ means that as trains travel over regions that may or may not be GSM-R equipped, their mobiles must support both technologies – GSM-R and legacy analogue radio

RFF launched the GSM-R project mid-2003 and decided to divide the country into zones that would be equipped one-by-one (mainly for budget reasons). It was then foreseen that the deployment would be concluded by 2015.

RFF mandated the SNCF Telecom Engineering department to conduct the GSM-R deployment of the north eastern zone of France. This mandate covered the design and deployment activities for:

• Transmission
• NSS and BSS network including the two main redundant NSS sites
• Radio sites on the lines
• Dispatcher systems
• End-to-end validation (lab and on-field)

Figure 1 displays the original plan.

Figure 1: Target dates for operational GSM-R for specific zones

Challenges and constraints of GSM-R in France
Opening the ground-to-train service on a given line implies the implementation of the following:

• The GSM-R radio layer, which requires:
  • At least partially the common GSM-R Core Network, including the usual GSM-like NSS, MSC and HLR, but also additional servers that deliver the railway features
  • BSS infrastructure, including the BSC and TCU equipment, linked to the NSS, dedicated to the radio sites.
  • Radio sites delivering the radio coverage suited to the functional requirements of the railway traffic management
  • Data network supporting Operation and Maintenance servers with tools, allowing configuration and operation of the NSS and BSS
• Transmission network between radio sites and BSCs
• Railway telephony, linked to the GSM-R NSS, in order to provide the dispatchers with the fixed terminals they need
• Dual-mode GSM-R/analogue CAB radio in all engines that will have to run through the area

One consequence of the deployment strategy and programme is that transitions between lines equipped with GSM-R, and lines still equipped with analogue radio, will have to be managed until deployment is complete. The safety constraints that must be followed in France have led us to design some mobile based ad hoc equipment which allows the transfer of a REC from GSM-R to analogue (and vice versa).

Even though GSM-R is a standard, implementation and operating rules differ from one country to another. On the French Railway Network, ground-to-train radio availability is mandatory to run a normal mode of operation.

The unavailability of the radio service would lead to the application of very restrictive operation rules, including drastic speed reduction. One can understand that the global GSM-R architecture has to be highly reliable in order to ensure the necessary level of availability for train operations.

Particular attention has to be paid to Core Network, BSC, and transmission backbone availability, whose failure could impact the railway traffic over a very large region, if not the entire country.

Therefore, the GSM-R network architecture in France has been designed in order to minimise the impact of any single failure on the behaviour of the GSM-R services. As an example, any BTS is connected to a BSC via two independent paths (loop configuration). Site design includes replication of key elements such as air cooling, power supply and transmission adduction. For key equipment which could not offer automatic redundancy features (MSC and HLR, BSC), efficient disaster recovery plans have been set-up in order to restore the service on dedicated backup equipment.

The GSM-R network also differs significantly from a classical GSM network by the fact that the radio traffic is extremely low and sporadic. Therefore, classical tools commonly used by a GSM operator to monitor the Quality of Service, which are based on a statistical approach, do not apply and specific GSM-R tools have to be studied.

Figure 2

Current status

By December 2009, the status of the project is the following:

• The Core network has been built and is operational. Selected technical architecture consists in two ‘very secure’ Core sites which include the NSS equipment (MSC, HLR, core platforms and servers such as SCP/IN, SMSC, OTA). These two sites are twin sites running in active/stand-by mode. Should a disaster happen on the active Core site, a ‘hand-over’ to the backup site could be performed technically in less than one hour owing to the transmission backhaul implementation
• Currently two high capacity bi-BSC-TCU sites have been built. Once again, should a BSC–TCU be damaged, transmission backhaul would allow the BTS transmission links to be rerouted towards an operational backup BSC fairly quickly
• An Operation and Maintenance Centre gathers all servers and terminals which allow operations of NSS elements, BSS elements, and transmission gears: configuration, administration, maintenance
• The new 300km East European High-Speed Line has been built from 2003 up to 200 and is equipped with GSM-R. A specific chapter later in this article is dedicated to this line as its GSM-R design is very innovative
• A 300km test line named ‘the Pilot Line’ has been implemented in order to address most of the technical challenges. The conventional line from Paris towards Bar Le Duc has been selected for this purpose and has been put into service in two steps – one in March 2006 and the complete line in January 2007. Its characteristics are:
  • A dense urban area in the suburbs of Paris, including long tunnels
  • Many specific zones requiring some advanced radio engineering studies
  • A maximum speed of 160km/h
  • Three tunnels outside the suburbs
  • Around 1,250 traffic runs a day
  • Closeness to the East European High-Speed Line, also equipped with GSM-R
• 2,000km of lines in the Eastern part of France, that is a small quarter of the whole country, including the regions named Champagne, Ardennes, Lorraine, Alsace and part of Picardie have been deployed from 2006 to 2008 (under the name ‘Tranche 1’). This has led to:
  • Construction of 320 radio sites
  • 25 tunnels have been equipped
  • Eight sets of lines from around 100km to 450km each have been put into service one-by-one, from March 2008 up to September 2009.
• More than 4,500 engines have been equipped with a new dual-mode CAB radio

A lot of work has been undertaken since 2007 to interconnect the French GSM-R core network to core networks of neighbouring railway operators. Currently, the following interconnections are technically available:

• DB in Germany
• Infrabel in Belgium
• Prorail in Netherlands
• CFF in Switzerland
• RFI in Italy

Additionally, based on global European agreements driven at UIC, the network architecture of the interconnections has been coordinated to implement optimised routing and redundancy.

It is foreseen to interconnect the French network to other GSM-R Infrastructure Managers: roaming agreements with ADIF (Spain), Eurotunnel, CFL (Luxembourg) and Network Rail (UK) should be concluded in the next two years.

Lessons learned from operations

Being a standard, one might think that GSM-R and overall ground-to-train radios built upon it should work 100% at switch-on. Obviously that was not the case and reality offered more contrast.

First, RFF and SNCF have decided to build a captive GSM-R test bed, close to Paris, which is a small replication in a lab of a complete network. It includes:

• A set of all type of NSS equipment and core platforms
• 2 BSC-TCUs and 3 BTSs
• A test line of 9 BTSs, linked to the lab system
• One dispatcher system and all type of fixed dispatcher terminals
• GSM-R handhelds of different types and CAB radio

This test system is configured, operated and maintained in order to:

• Validate hardware and software of all network elements, before deployment in live network
• Perform end-to-end system tests which ensure compliancy of services
• Investigate technical issues seen in the field to find the root causes, get the fixes and validate solutions
• Design and validate OA&M procedures before implementation on the live network
• Train people from engineering and operations organisations

Despite intense activity performed in our system lab from mid-2004 which has been fruitful in terms of the number of defects discovered and fixed by suppliers, we have been facing some issues that have remained since opening the first operational GSM-R service, including:

• Mobile products: surprising problems appeared mainly in the domain of radio network reselection, which seem to be specific to the usage of mobiles in the context of GSM-R application
• Radio difficulties were encountered in dense urban areas, including:
  • Number of radio frequencies granted to the GSM-R band is small (4 Mhz of band) which leads to complexity in frequency planning
  • Proximity of some high capacity GSM-operator sites transmitting at fairly high power can generate blocking at the mobile level
• National operational rules can be highly demanding in quality of service provided by the radio to the end users: should this quality be insufficient, drastic decisions must be made, such as speed reduction, thus severely impacting railway operations
• Ground-to-train radios built on GSM-R brings new procedures and changes in the habits of both drivers and dispatchers. A significant effort must be made to train and support the users when switching to the new technology

Tools and procedures have been implemented in order to monitor network quality of service. This monitoring actually covers different aspects, including:

• Technical quality of service of the GSM-R network itself, which encompasses the behaviour of the telecommunication equipment, both GSM-R and transmission
• Functional quality of service of end-to-end ground-to-train radios, which includes the railway telephony, mobiles, and mainly deals with availability of overall service for railway operations
• Perceived end users quality of service which takes into account the capability of the technology to deliver:
  • First class audio quality
  • Ease of use of terminals, fixed or mobiles

Lastly, it is a well-known issue that building a telecommunication network while operating part of it at the same time induces difficulties and can penalise the quality of service, especially in the context of the French GSM-R network whose core network is highly centralised. In order to cope with this issue, both engineering and operations organisations have put in place processes through which any set of technical operations on the network is traced and checked before execution in order to evaluate potential impacts.

Next steps

As explained earlier, the GSM-R deployment strategy and planning has been organised by zones and SNCF was mandated to deploy and operate the north eastern zone.

RFF launched a bid in 2006 targeting the handover of the GSM-R deployment to a private party through a Public Private Partnership procedure. This project is now known as the ‘PPP GSM-R’.

The activities handed over to the private partner include the following:

• Deployment of the radio network – i.e. mainly deploy BTS to provide radio coverage along the 12,000km of remaining lines and deploy new BSC sites; the deployment should be completed within a three year timescale
• Operation and maintenance of the whole radio network – including the existing part – for 15 years

Deployment of the main transmission network, both backbone and local loops to BTS sites, as well as the dispatcher system, will still be deployed by SNCF as of today.

In this new project structure, RFF provides the necessary coordination between the private partner and SNCF.

A candidate was selected in early 2009, and it is now foreseen that the PPP contract should be signed in the near future – hopefully before the end of the first quarter of 2010.

The deployment project is based on the map and planning hereafter – which could be subject to revisions when the contract comes in force.

The key ideas of the project organisation include:

• The whole network is divided in three geographical zones: North Western, South Western, South Eastern
• The planning is composed of 20 phases, each phase being associated with two elementary geographical areas in each zone named ‘brins’ (this rule has a few exceptions for the first and last phases)

The East European High-Speed Line (EE-HSL)

On 10 June 2007, commercial operations of the EE-HSL were launched. This was the result of many years of efforts targeting the development of a high-speed railway from Paris towards Germany and Eastern Europe.

With a length of 300km and commercial operations at 320km/h, the EE-HSL, at its current stage, brings significant reductions of trip durations between Paris and many cities such as Reims, Metz and Nancy in France, Luxemburg, Francfort, Ulm and Münich in Germany.

This project has included many innovations in different areas such as the platform, civil works, and GSM-R coverage. Test plans have been designed in order to validate operations at a speed of 360km/h. Even more, a specific sub-project named V150 has been designed by RFF, SNCF and Alstom, whose objective was to set up a new railway speed world record. The objective was fulfilled on 3 April 2007 with a train that achieved the incredible speed of 574.8km/h.

In the context of this event, and beyond the world record itself, the V150 team has accomplished the following impressive achievements in quite a short period of time:

• More than 700km performed at a speed higher than 500 km/h
• More than 2,200km performed at a speed higher than 400km/h

GSM-R on the EE-HSL

This V150 project has obviously been a tremendous opportunity for many technical teams to perform some unique experiments. This has been the case for the engineering team responsible for GSM-R radio design and implementation.

Before delivering some of the results that were gathered through high-speed testing, let us describe quickly the GSM-R radio network architecture, which is quite innovative. The GSM-R technology has been implemented on the EE-HSL line in order to provide:

• Ground-to-train radio services for drivers and dispatchers
• Radio transmission for the ETCS signalling application

To meet radio service availability requirements specified by ETCS, the project team has decided to implement two layers of GSM-R radio coverage, each layer of cells, belonging for safety reason, to a different BSC.

Such architecture happens to be quite efficient, although not easy to validate and tune: the lack of GSM-R frequencies and proximity of conventional lines also equipped with GSM-R induced some difficulties which had to be overcome.

GSM-R for ETCS on EE-HSL

EE-HSL has been equipped with two signalling systems: the legacy system used on French high-speed lines, namely TVM430, as well as ETCS level 2.

Running trains (SNCF TGV and DB ICE trains) on this line are equipped with a dual-mode on-board signalling system compatible with both TVM430 and ETCS level 2.

As of today, the EE-HSL is being operated with TVM430 until the migration towards ETCS level 2 is performed.

ETCS system validation has taken place on the EE-HSL line for the past two years. In parallel, the quality of radio transmission being a key success factor for ETCS level 2, the GSM-R project was also deeply involved in providing support to the ETCS group since 2007.

GSM-R quality of service is mainly addressed through the following aspects:

• GSM-R transmission interferences should not degrade the communication between the on-board system (EVC) and the trackside equipment (RBC)
• Dropped calls should be minimised to an acceptable rate

Although some objectives and methods had been provided by the specification bodies to measure those QoS aspects, the criteria themselves were defined globally on a line basis and appeared to be insufficient to provide a clear picture of the QoS of the GSM-R media for ETCS. Based on that early statement, it was decided to build an integrated ERTMS/GSM-R project team to analyse that particular aspect of the project.

That project resulted in a new approach where a new set of requirements together with systematic methods and tools were defined to analyse the GSM-R QoS for ETCS. The most significant results of this work are the following:

• ETCS level 2 cannot cope with QoS objectives defined globally for a line, they need to be geographically localised. Indeed, in some specific areas like line entries or other significant points on the line where essential or safety related function can be invoked
• Reliability of the metrics can only be guaranteed if sufficient data is captured, which requires capturing hundreds of hours of GSM-R data traffic
• In order to capture and process this data, an industrial approach is necessary: planning the runs and extracting the captured information from the tools, and compiling it (which results in handling huge amounts of transmission samples). This led the GSM-R project team to develop a full set of tools

Despite the fact that additional work is obviously required in order to provide quality optimisation in a couple of geographical areas, the results already available are very positive.

Conclusion and next steps

This article highlights that the GSM-R project in France is well advanced:

• Overall architecture is specified and key decisions have been made, especially those related to security of operations
• The core network is built and ‘up and running’
• After successful experiments on a pilot line in 2006 and 2007, on time completion of deployment of the north eastern zone ‘Tranche 1’ in 2008 and 2009 has proved that the objectives of this ambitious plan could be met. Around 3,000km in France are now in service and operated in GSM-R.
• In parallel, some significant effort has been put, together with other railways, to improve the European standards with the necessary evolutions for handling of the GSM-R emergency calls in dense areas. This evolution, named eREC (enhanced Railway Emergency Call), will be part of the TSI in the next edition
• GSM-R is ready on one high-speed line, not only for ground-to-train radios at a speed of 320km/h, but also for ETCS validation

Current success of GSM-R in France will go on with the following challenges:

• Additional validation, by performing ERTMS end-to-end testing, that the GSM-R architecture and performance on the EE-HSL fulfil application requirements, last step before starting ERTMS operation
• Introduction of new functionalities such as eREC, Shared Railway Emergency Call Areas at borders, in order to improve ground-to-train operations and safety
• Launch of the PPP GSM-R, which means bringing up to speed new actors, and running a quite complex project

Rémi Bévot

About the authors

Rémi Bévot

Within the SNCF Engineering organisation, Mr. Bévot is currently responsible for the ground-to-train GSM-R project, encompassing infrastructure and mobile sides. This includes the following topics: functional requirements, overall network design for both Core and Radio, deployment, testing activities and transfer towards operations and maintenance. Before joining the SNCF in 2003, he worked for many years in the area of telecommunications, mainly for manufacturers delivering wireless products and services.

Olivier Labourdette

Olivier Labourdette

Mr. Labourdette joined the SNCF Engineering Telecommunication Department in 2005 as Project Manager for GSM-R functional requirements and system design. He has been particularly involved in specifying and delivering GSM-R end-to-end solutions fit for railway radio operations. He is also, since 2005, a member of the standardisation bodies at UIC in charge of driving the evolutions of GSM-R. His past experience before joining SNCF was within Nortel Networks where he spent five years working on GSM/UMTS wireless core network solutions as a support account manager for O2 and Vodafone accounts in Europe.