GSM-R Consultant Martijn Kuijpers: 'GSM-R is a completely different ball game, compared to ordinary cellular network planning'

Features of GSM-R

 

Voice Group Call Service (VGCS)
These are group calls, similar to the walky-talky communication used previously in railway communications. A number of users can take part in a conversation. Listeners become talkers by pushing the PTT (Push-to-Talk) button. The advantage of VGCS over regular GSM conference calls, is its spectrum efficiency. When multiple users are located in the same cell they use no more than one frequency for all listeners and two for the talker.

Point-to-point (PtP) calls
These are basically regular GSM-calls between two devices on the GSM-R network.

Broadcast calls
One person speaks while the others are listening. A specific type of a broadcast call is the Railways Emergency Call, or REC. This is a broadcast call with the highest priority (REC priority level 0) which is used in case of an emergency.

Priority control
Multi-Level Precedence and Pre-emption Service (eMLPP) allows the priority of different calls to be set. The default level is 4, used for regular point-to-point calls. The highest level is 0, mainly used for emergency calls. There are higher priority levels (known as A and B); these are reserved for network messages.

Shunting mode
For users working on the tracks, the application will regulate and control user access to shunting communications. A Link Assurance Signal (LAS) gives reassurance to the driver that the radio link is working.

Functional addressing
Functional addressing is an alias system used to call someone in a temporary function rather than a specific individual. This allows callers to reach the driver of a specific train, or a specific control center, or anyone else in a specific role, without knowing who fulfills that role at the particular moment.

Location dependent addressing
Is an extension of functional addressing, which allows to reach a person in a specific function closest to a specific location. For example: call the nearest driver, call the controller closest by, etcetera.

Also see our GSM-R expert glossary

High speed GSM-R network measurement train

GSM-R expert Martijn Kuijpers (l) and a colleague onboard a GSM-R measurement train.
Photo courtesy of Clear CinCom.

Challenges in GSM-R Radio Network Planning

Clear CinCom director Martijn Kuijpers on why GSM-R is different

Martijn Kuijpers (1975) is the owner-director of Clear CinCom Radio Telecommunication Consultancy, a company specializing in GSM-R. Kuijpers has been working with GSM-R since 2001, when Siemens and KPN contracted him to plan the GSM-R network for the Dutch railway infrastructure provider ProRail - one of the very first GSM-R networks in the world.

‘What I remember from those early days is that the specifications set in EIRENE where highly theoretical. We were the first to put theory to practice. In the end, we gave a lot of recommendations, most of which eventually made it into the final GSM-R specifications.

‘Even experienced radio planners tend to underestimate the complexities involved in GSM-R. Quite often, railway companies call on us to pick up when their own planners are not able to finish the job. The root of the problem usually comes down to traditional radio planners underestimating the implications of the initial network requirements. We help our clients find the most cost-effective way possible, but requirements need to be met. There is no other option. GSM-R is a safety network, so compromises are not acceptable.

Specific Requirements

GSM-R Expert Martijn Kuijpers

GSM-R expert Kuijpers: 'The focus of a GSM-R radio planner is very different from that of a traditional radio planner'

‘What makes network planning different for GSM-R, are basically three things. First off, the requirements are much more specific. That makes sense if you think about it: if the quality of service of your phone conversation drops in a certain area, generally your safety is not affected. But if your GSM-R signal is unreliable, even for a few meters, results can be catastrophic. Secondly, the initial network design of GSM-R includes a division of group call areas. When a train encounters a problem, GSM-R is used to send information to the control center. But it can also send direct commands to other trains in the vicinity. One such command could be: “Stop!” So, it is crucial that group call areas are properly defined, which is also done in the initial network design.

A Different Ball Game

‘Traditional radio planners never have to worry about these sort of things. But the main reason why GSM-R radio planning is a different ball game altogether, is a technical one. Traditionally, in theory at least, antennas are placed in hexagons: that is the most efficient way to cover an area. But GSM-R is not meant to cover a large, two dimensional space, but rather a line from point A to point B. This is why the focus of a GSM-R radio network planner is completely different.

'Everyone who gets onboard with Clear CinCom – even some very experienced but traditional radio planners - is surprised by how much time it takes to fully grasp the complexities specific to GSM-R. Experience matters, but it needs to be the right experience.

Constant Innovation

‘Knock on wood, but so far we never had to let a client down. In almost any project, there is at least one thing that needs some serious lateral thinking. Paradoxically, the stricter the requirements, the more innovative you need to be to make things work. So when we hire radio planners, creativity is a key element we look for. Because we have enough experience to know that no matter how much we’ve seen and done, there will always be a new challenge that will startle us at first. That is also the best part of the job: solving things that seem insolvable.

 

Read more

Homepage of Clear CinCom, radio telecommunication consultancy
GSM-R case study by Clear CinCom