When it comes to train operations, the GSM-R standard is in widespread deployment. It was developed by ETSI and the International Union of Railways, and was based on the GSM Voice Group Call service to provide a broadcast voice service to support rail operations. But it is unlikely to go through developmental iterations that will see it become relevant to the connectivity supplied to train passengers.
‘Rail operators can split between GSM-R for their own operational needs and in-train repeaters to enable their passengers to use cellular capacity,’ says Markus Kalt, VP of business operations at Andrew Solutions. ‘The two are completely different and require very different approaches.’
GSM-R has several applications for rail operators, as Håkan Samuelsson, CTO of Axell Wireless, explains: ‘Rail operators primarily use GSM-R. It has a number of different use cases such as supporting communications between the dispatcher and the train driver,’ he says. ‘It is also used to allow communication on board the train and supports handheld terminals used by ticket inspectors and catering staff as they serve passengers. There is also potential to use GSM-R for many other types of applications and, in the future, signalling information will be transmitted over GSM-R.’
However, by its nature and design, wider applications for GSM-R are limited. ‘The GSM-R standard offers very high reliability along with a higher installed cost,’ says Stephen Rayment, CTO of Wi-Fi specialist BelAir Networks. ‘However, it offers relatively low throughput so may be a good bet for train control systems that require high availability but lower bandwidth.’
A key point is that while its capabilities may seem limited in the face of wireless technologies with ever broader bands, the GSM-R network supports public safety. Therefore, reliability is paramount and represents a far more important attribute than the potential ability to serve passengers with mobile video, for example.
Kalt acknowledges that the GSM-R market is a highly specific one. ‘GSM-R for me is very specific,’ he says. ‘It does two important things. The first is that it simply provides reliable voice communications between despatch and the train driver and staff. The second is that it enables signalling to be transferred as data through the GSM-R channel. Having signalling means that you have different requirements and redundancy is a key concept. If a repeater, for example, fails and you don’t have redundancy, it’s a big deal, as this is a safety issue.’
There appears to be little room for innovation when it comes to GSM-R. Two key vendors dominate the market – Kapsch and Nokia Siemens Networks, with Huawei also present – and although some countries’ GSM-R capacity is insufficient, others are only just turning to the standard. ‘GSM-R is the recognised industry standard,’ says Samuelsson.
‘But in spite of this, it is still being deployed in several countries and there are a number of countries that are behind schedule. GSM-R is the only rail communication standard that has been approved by all the countries in Europe and, because of this policy it will be difficult to introduce a new standard.’
Samuelsson says that TETRA has been suggested as an alternative to GSM-R, but in his view it will only be adopted in countries outside Europe. In the meantime, countries with heavy rail traffic require more capacity to support their operations. ‘In countries with heavy rail traffic the capacity available in the allocated GSM-R spectrum is not sufficient,’ he adds. ‘That need has led to plans to increase the spectrum for GSM-R from 4MHz to 7MHz.’
GSM-R spectrum is also threatened with its adoption by commercial operators of new wireless technologies in the 900MHz band. ‘Several countries now allow the use of UMTS in the 900MHz band, which is immediately next to the GSM-R spectrum,’ says Samuelsson. ‘The risk of interference between the different wireless services in areas close to the tracks is being debated at the moment.’
With the rail operations environment, served via GSM-R under capacity pressure, there’s little scope for the technology to be used to support the growing bandwidth requirements of passengers. As a consequence, cellular technologies are widely used to provide connectivity to users.
However, trains are highly challenging environments. A steel can hurtling along a track passing from base station to base station, network to network and even country to country presents huge quality of service issues, and train companies, which may be perceived as those providing the services, may prefer to avoid the issue entirely.
‘The key challenge for rail operators is ensuring a great user experience,’ says Rayment. ‘It’s important to remember that users don’t care that there are technical challenges. If they don’t get good wireless service, they will be disappointed. And, since one of the key drivers behind offering wireless connectivity on trains is to maintain rider satisfaction, there’s little point in offering the service if there’s a potential to disappoint users.’
Samuelsson agrees that customer expectations have become greater. ‘The consumer demand for mobile broadband and data services has extended to passengers travelling on trains, who now expect to be able to access wireless services on their smartphones or a USB modem,’ he says. ‘As a result of this demand, many train operators are now providing Wi-Fi coverage inside the coaches. Enhancement of the GSM and UMTS signal levels inside coaches is also a feature offered by many rail operators.’
That enhancement is necessary because of the hostility to wireless of the rail environment. ‘Speed of travel, number of consumers and types of applications are the main issues,’ says Rayment. ‘Speed makes it difficult to maintain contiguous connectivity, while the number of users impacts available bandwidth per user. The railway environment prone to shocks and bumps is also physically challenging for network equipment.’
Kalt agrees: ‘In a sense, a railway coach is a Faraday cage.
There is a high level of shielding so signal penetration is poor.’