Application Note

Railcar Couplings With

Wireless Network Technology

Anyone who frequently travels by rail will

know the situation: the train arrives on time,

but even before it reaches the platform the

station tannoy announces that the cars are

not in the order shown on the display board.

Sometimes there are even cars missing.

The reason for this confusion is that the

onboard technology lacks flexibility. Once a

train has been put together the car and seat

numbers are fixed and cannot be changed.

If shunting considerations cause the train to

leave the shed in the wrong direction, then

it will remain the wrong way around until it

reaches its destination. There is no way of

then renumbering the cars and seats. Customers

who are familiar with modern Ethernet

this and numerous other applications that

airline passengers, for instance, have learned

to take for granted: onboard entertainment

offering a selection of films that can be

shown on request, e-mail access via an on-train

internet service, up-to-date information about

connections to other trains, delays, etc.

A broadband network would enable the onboard

staff to improve their proffered service by

providing a central overview of the occupancy

Wireless LAN in trains

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But even now, trains are equipped only with

cable-based networking. There are two reasons

for this – its robustness and its durability.

primarily from the fact that each of the

couplings between cars is a bottleneck that

impedes the flow of data. They are the most

couplings. This is why trains still offer – at

best – digital bus technology or modulated

Ethernet via the UIC line. For many years,

Ethernet has been gradually ousting con-

ventional bus technology from the field of

Bus technology is relatively simple and

extremely reliable, but it does not lend itself

are mutually incompatible. Ethernet, on the

data speeds, it also facilitates fast recognition

of the train configuration and is readily

extensible. To date, however, connections

through train couplings have – at best –

achieved rates of 10 Mbps. This is why a

wireless solution is so attractive.

Wireless LAN (WLAN), as described in the

IEEE802.11 standard, is a wireless Ethernet

network. To date the WLAN standard has

diversified into four variants, from the venerable

These rates are perfectly adequate for imple-

menting the desired facilities and services in

the train, and for future requirements such as

electronic rear-view mirrors or front cameras

to improve passenger comfort. A wireless net-

work can be installed in an existing network –

to be modified.

Naturally, small easy-to-install units will

be advantageous here.

A further advantage can be achieved by

reducing the number of devices, e.g. by inte-

grating several WLAN interfaces into a single

access point. Naturally, the units also have to

meet all the standards required for equipment

that is installed in trains. These are stringent

requirements, and cannot be fulfilled by just

any device.

short distance. It is particularly important

to prevent nearby trains from setting up

unwanted connections. And, naturally, there

have to be safeguards to prevent unauthorized

persons from gaining access to a train’s internal

network.

Modern WLAN equipment is perfectly able to

meet these requirements. Authentication and

encryption are mechanisms that are described

in the WLAN IEEE802.11i safety standard, which