A CAB RADIO

The railway of today faces many challenges and these include the need to reduce costs, improve operational efficiency, and improve passenger / freight customer benefits. The industry needs to make the best use of the assets already invested, and providing reliable data connectivity for trains can deliver huge benefits for operators and customers. This article discusses how the GSM-R cab mobile asset, already fitted to main line train fleets in Britain, could be used to meet these objectives.

Railways consist of a huge number of assets which must all work seamlessly together to deliver a good, consistent service to passenger and freight customers. Every asset will show signs of wear and tear over time. These signs will appear differently depending on the type of asset, how it’s used, and what components fail first. Maintainers and asset managers won’t always notice changes in conditions or be able to associate these with particular hazards or failures. However, connected remote condition monitoring can provide information on how asset condition measurements on both trains and ground systems are changing over time, and allow interventions to take place before failure occurs. To achieve this requires a good train data connection.

Challenges

Fitting new communication and control technology equipment to existing rolling stock is a challenge. First-in-class train fitments can be costly and not run to programme. Any new device will need space on the train, connection to an existing reliable power supply, an interface to on-board systems, an external antenna causing no interference or compromising the vehicle integrity, and a means of sharing information with train staff. No two types of rolling stock design are the same and each will have its own peculiarities and limitations. Any fitment programme will take valuable trains out of service and require a competent resource to plan and undertake the work. All of this takes time and money the rail industry cannot afford.

Siemens Mobility SVR-411 V4 cab radios, however, have already been fitted to all of the British main line fleets by the GSM-R project, providing reliable, secure track-to-train voice comms’ across the network. This required many years of engineering to provide a spaceefficient, robust, and flexible cab radio rack in the space available, together with a compact control panel unit for the use of train drivers. A little-known fact to many in the industry is that the Siemens cab radio hardware / software is designed and made in Britain, so all the knowledge and capability to support and enhance the product is readily available. To date, over 12,000 cab units have been fitted to trains in Britain and the technology has also been successfully deployed in other countries including Denmark, Australia, Ireland, and Norway.

The design of a unit to allow the scale of deployment achieved by the GSM-R project required a special ‘gland box’ system to allow easy installation and replacement, and the development of an optional uninterrupted power supply unit to provide up to four hours backup power in the event of failure of train power. Two versions of the unit were originally created, one to provide voice communications only, the other to enable ETCS L2 data connectivity with the ground system. The very high availability requirements were met by a design which provided good thermal efficiency and shock resistance. The mean time between failures currently runs at around 250,000 hours, and the mean time to replace a unit is around 30 minutes. In Britain, a textual display is used to provide the human machine interface, but a full graphical unit is also available if required.

So, we have a successful product sitting on practically every train in the country, but what else could it do?

Digital Connectivity

Rail Engineer first reported on using the GSM-R cab mobile to support Driver Advisory Systems (DAS) and other applications in 2016, along with how the cab mobile would need to be enhanced to provide additional connectivity and functionality. GSM-R was originally based on 2G ‘voice only’ connectivity, and the limited bespoke data connection was only for the setting up of calls and very limited text information for the driver. GSM-R radio coverage has been provided along all Network Rail routes with the provision of over 2,400 base-station sites with heights between 15-29 metres (50-100ft), and 350 repeater sites, covering tunnels, cuttings, and other areas such as stations. Public 4G Long-Term Evolution (LTE) radio will not cover the rail network in the same way, however it is surprisingly good on some rail routes and in some parts of the country, but only if a good, efficient train roof top antenna is used.

Obvious signal blockers for public 4G are deep cuttings and tunnels. Trains also run through rural areas with few villages, towns, or roads and therefore little public mobile coverage. With busy trains carrying the equivalent of a small village-worth of people, all attempting to connect to their nearest mobile operator’s base station from inside a ‘Faraday cage’, public mobile coverage on trains can be poor. A Faraday cage, to which modern trains can be likened to, shields its contents from electromagnetic fields, such as radio signals. So, when a radio signal hits the cage, the electromatic charge remains on the outside rather than travelling inside.

In 2020, Transport Focus found that train passengers only receive a good 4G connection some 58% of the time. However, using a good, efficient train roof top antenna can dramatically improve coverage, compared to inside a train, and Siemens has developed a new multiband antenna called SMBA (Siemens Multi-Beam Antenna) to provide reliable GSM-R/ 4G / GNSS / Wi-Fi connectivity, all within the footprint of the original GSM-R train antenna.

The cab mobile has also been enhanced to provide GSM-R, 4G LTE, GNSS/GNNS, Wi-Fi, and with SD & SSD memory cards for other applications. A Secure Digital (SD) card is a compact and removable storage device with extensive capacity, and a Solid State Drive (SSD) is a faster alternative to the old storage hard drive. Accelerometer functionality has also been integrated into the processor module along with optional 4G modules. All this functionality seamlessly connects to the external antenna, and the processor card supports all the main features for an extensive application platform with reliable connectivity. The cab mobile is no longer 2G ‘voice only’.

The British roll-out of the GSM-R cab mobile system started in 2009 and all the units have since been upgraded with the additional functionality. The creation and installation of the mobile cab radios led the Siemens team to realise that having overcome the major challenges of on-board installation –space, power, interfaces – there was an opportunity to provide a range of new functionality inexpensively, and with minimal impact on train fleet availability.

In a similar manner to other items of modern electronic equipment such as smartphones, by developing ‘apps’ to run on the additional SVR-411 processor, affordable new functionality and improved operational efficiency can be provided in a number of ways.

Train Borne Condition Monitoring

The first ‘app’ to be developed by Siemens used the in-built GNSS capability and three-axis accelerometers within the radio to continuously monitor the train’s ride. This is known as Train Borne Condition Monitoring (TBCM).

Trials in the South West of England have demonstrated the system can reliably pinpoint areas where there are voids under switches/crossings and on plain track, which can be used by the maintainer and asset steward to prioritise further investigation and plan the appropriate intervention. TBCM can also identify areas of ‘rough riding’, especially if reported by several trains passing through the same part of the network. ‘Dip track’ locations, which can ultimately result in derailment if not detected and mitigated, can also be identified.

By adding this functionality, every train can continuously monitor the state of the track, and communicate the status back to the maintainer / asset steward to instigate an intervention in real time, without the need for anything other than a new plugin card and a software update.