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Citizens increasingly expect access to Internet and wireless communications services whether they are at home, at the work desk, or on the move. Wireless connectivity is increasingly being offered to rail passengers where it is also often cited as an incentive to attract travelers to choose rail over other transport modalities.

When rail passengers use a wireless local area network (LAN) within the vehicle compartment, the connection of this LAN to the Internet backbone can present a significant technical challenge. Numerous competing requirements include the need for good geographical coverage and availability; quality of service; sufficient bandwidth; and a cost that is acceptable to the consumer. Solutions have included uni- or bi-directional satellite; bundled cell phone lines; wireless hotspots in stations; and combinations of these measures.¹ Proposed solutions include WiMAX, for which a good deal of terrestrial infrastructure would be needed, high altitude platforms, for which the aeronautical technology is not sufficiently mature, and 3G mobile networks, which tend to lack sufficient geographical coverage. Satellite has emerged as offering the winning combination of coverage and bandwidth, either in isolation or as part of a multi-bearer solution.

A broadband access service launched fully in Europe in 2008, following a trial phase supported by the European Space Agency² and led by Thales and 21Net Ltd., uses a two-way satellite link in Ku-band. This relies entirely on a tracking reflector antenna on the train’s roof (see Figure 1). The radome height is 72 cm; this limits the number of railway routes where services can be offered due to the need for this headroom. Clearly, a lower profile scanning antenna would open up the scope for wider geographical availability of this service.

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