A nomad will often go where no-one has gone before, and ATDI is helping this one blaze a trail.

Nomad Digital provides wireless broadband services to rail passengers by connecting trains to trackside base stations. However, no suitable spectrum has been available for the company to introduce its systems in the UK – until ATDI helped find a way of using previously unusable spectrum.

ATDI established that Nomad’s services could coexist in the 5GHz region with current operators in that range including radio astronomers and commercial air traffic. UK regulator Ofcom is set to formalise ATDI’s findings by granting a licence which will allow Nomad to begin operations.

“This is a classic case of making one bit of spectrum do two jobs,” says ATDI managing director Cyprien de Cosson. “The scarcity of spectrum resources is the bane of every radiocommunications project. What we have done here is establish the principle of co-existence whereby different services can occupy effectively the same space.”

The modelling for this involved taking each service – Nomad’s broadband signal and the frequencies used by radio astronomy and air traffic control – in turn, creating a physical model in terms of test points representing applications of the services, developing an interference susceptibility model, then computing the worst case coupling between each potential train location before finally marking each train location as interfering or not.

ATDI found there were four potential solutions to the issue of interference – two involving filtering and two not – which would provide broadband services for train passengers without significant problems for other users. Without filtering, around 8% to 9% of the railway’s length would not have the broadband signal; with filtering, that figure fell to between 1% and 2% – and there would still be a broadband signal for train passengers even when the train was passing a large airport.

“We know there will be a great deal of interest in these ideas,” Cyprien notes. “The problems Nomad faced are the same as those for the gamut of radiocommunications companies and I am delighted we are able to offer them an interesting new potential solution to these challenges.”

Nomad’s Executive Chairman, Nigel Wallbridge said “We are pleased and proud that we have made a start acquiring licensed radio spectrum, and are keen to promote this to the rail industry where there is significant benefit.”

UK spectrum regulator Ofcom is permitting access to spectrum that is owned and used by four official bodies: the Ministry of Defence, the Meteorological Office, the Civil Aviation Authority and National Air Traffic Services.

Nomad Digital provides wireless technology and data networks for the transport sector. In 2005, the company created the world’s first broadband internet service in conjunction with T-Mobile and Southern Railways for the London to Brighton service.

Posted in Archive