Until few years ago railway operators basically considered the rail telco network as an ancillary system; that is, helpful, but not really fundamental for the operations.
However, with the introduction of ERTMS (the European Rail Traffic Management System), all this is changing. One of the ERTMS key components is the GSM-R telecoms network, which provides voice communication for train drivers and signallers and provides data communication for ETCS signalling. Furthermore, as GSM-R is based on a 2G mobile telco network, that too is destined to be replaced and work is currently underway to do so. The UIC’s FRMCS (Future Railway Mobile Communication System) is the planned successor of GSM-R and will also act as a key enabler for rail transport digitalisation.
This modernisation of railway infrastructure to improve rail safety and improve the passenger experience with longer, faster and more frequent trains, is therefore, much more of a revolution than an evolution. While the sector has historically been slow to change, the pace of technology development and need to replace assets that are failing or getting close to end of life, means that several rail operators have already launched their own projects for “Digital Rail”.
Every project has different requirements, but they all share similar potential benefits:
- Savings on maintenance costs
- Improved capacity, thanks to the adoption of new ETCS signalling systems, which rely on a modern telco system
- Improved operational safety of operation
- A wider set of new services for rail crew and passengers, thanks to the integration with the public 5G mobile telco networks
That’s why the telco system will become fundamental for operations, for every modern railway within the next 10-15 years.
The importance of testing the telco network
If the telco system fails, the train won’t receive a signal to proceed, which means it has to stop, there and then! Therefore, in order to prevent passenger delays, the telco network needs to be fully reliable – and regular testing needs to be carried out to ensure this is the case.
For many railway infrastructure operators, telco network testing used to take place every few months or a couple of times a year – this is no longer the case. Once systems depend on ETCS Level 2 signalling, the train-ground communication is vital as all signalling is digital with no traffic light style signals, and messages are all transmitted via the telco network. As a result, it’s critical the network is test much more frequently; ideally as often as possible and at least several times a month.
This testing is carried out by conducting Drive Tests. Drive Tests are used to measure and assess mobile radio network coverage, capacity and Quality of Service (QoS), using specialised electronic equipment.
Drive Test systems can therefore, collect and record information relating to a network’s service within the test geographical area. The results can be used to measure the QoS against pre-determined KPIs, as well as for diagnostics and troubleshooting.
Drive Tests for rail telecoms network acceptance
The initial test & measurement of a rail telecoms network normally takes place at the installation and acceptance stages, using a Drive Test system. Even before installing the network, Drive Tests are used to check if the frequencies to be used are affected by interference from third parties (known as band clearance).
During the installation phase, first coverage and network accessibility tests are performed, which is followed by reliability testing, travelling across the network.
The key rail test specifications (Eirene SRS and FRS together with O-2875 and Morane) are normally carried out by telecom vendors but it is also key for railway operators to know exactly which specification/standard and service levels the network is compliant to as KPIs for voice may differ from data.
As Drive Tests are the most common way to gain network acceptance, it is easy to pigeon-hole their use. However, many leading rail operators around the world regularly use Drive Tests for the whole of the railway operations lifecycle.
Ongoing Drive Tests for operational lines
After a network has been fully accepted an ongoing network monitoring & troubleshooting routine should be established as an integral part of daily operations and maintenance. Critical situations can occur if there are issues with interference or equipment failure on operational railway lines. Based on operational experiences, an ongoing proactive maintenance or service assurance campaign is highly recommended to ensure critical levels of quality and service are maintained, especially for rail networks operating ETCS level 2 signalling and above.
When systems fail, the ground-train communication can potentially cause train stoppage and delays. This can be critical when operating at high utilisation levels with many trains running every hour. The ability to source and pinpoint issues quickly, efficiently and effectively can be vital to maintain continued train operations.
This ensures QoS standards and operational KPIs are met; not only giving service assurance but also making it easier to identify trends and areas of service degradation caused by interference, for example.
One size Drive Test does not fit all
Rarely is there one perfect solution for all circumstances and the same applies to Drive Test systems. There are several options to suit, depending on the budget and Drive Test requirements.
Dedicated test trains or test wagons can provide the facility to permanently install Drive Test equipment, often as racks including options for unattended and remote management.
Alternatively, transportable solutions such as customised on-board units or equipment housed in a trolley or backpack can often be more suitable. For example:
• if tests need to be carried out less frequently (making a permanent installation not cost-effective)
• when using commercial trains (so equipment cannot be permanently installed)
• when tests must be conducted in multiple locations within a short space of time (so a test train is less practical).
In each case, it is important that the Drive Test system is designed to match the correct type of radio, scanner, power source, antenna connections, physical and other system requirements necessary to meet the specific type of test(s) required.
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