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Air Traffic Control Systems Could Ditch Radar And Release 5G Spectrum

plane in the sunset sky © magann - Fotolia
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TV signals could be used to locate aircraft as 5G plans take shape

Spectrum for 5G mobile networks could be freed up if a radical new system for air traffic control is approved.

Radar provider Thales has been given government funding by the Technology Strategy Board to investigate how existing TV signals could be used to locate and track aircraft – using a system called “multi-static primary surveillance radar”, or “passive radar“.  The study also involves the UK’s air traffic control provider NATS and research organisation Roke Manor.

The government likes passive radar as it would allow it to sell off the spectrum currently used by air traffic control, while Thales argues that it would be much more reliable than the existing method, which has been in place since the Second World War.

5G plans underway

Radar Screen scan danger © MSA - Fotolia.com“This two year project will be a feasibility study which will set up prototype systems that will use TV signals already being broadcast from transmitters around the UK,” said a Thales spokesman. “Absolutely no radar systems will be switched off during the study, which will report to regulators and the air transport industry.”

The proposed system would use a new set of receivers to monitor TV signals, as well as their reflections from objects such as aircraft.  In essence the system uses the phenomenon whereby passing aircraft can produce “ghost” interference on older TVs, but turns it to good use by detecting and measuring it more accurately.

By measuring the  timing of TV signals reflected from aircraft, the system will be able to locate them precisely, and measuring the Doppler shift of the signal would also allow their speed and direction to be measured. Such systems are called “bistatic” or “multistatic” because they use different stations to send and receive the signals.

The principle is not new – passive radar was the basis of the very first experiments that led up to the invention of radar during the World War II. Robert Watson-Watt’s first demonstration of the principle of radar in 1935 used the BBC shortwave transmitter at Daventry to detect a  Handley Page Heyford bomber at a distance of 12 km.  Radar systems moved to conventional radar enabled by antennas which could alternate between transmit and receive.

The multistatic technique has had a renaissance recently, with the arrival of powerful signal processing technology, and cheap directional antennas, which has allowed systems that are as good as conventional radar.

Thales argues that passive radar is actually more efficient than the current system which relies on one radar transmitter per airport putting enough signals in the sky, and which can be susceptible to confusing echoes and interference from the increasing number of wind farms in the UK. However the company acknowledges that it may encounter resistance to change and that it must convince people of the advantages and safety of the new system.

“This system should be more cost effective, as it  uses signals which are already being transmistted,” said the Thales spokesman. “Digital TV is part of the critical national infrastructure, so it is already safeguarded and will be reliable.” The system will also reduce power consumption, making a small contribution to reducing the carbon footprint of air travel.

No cost for the project has been revealed, but the  TSB is funding half of it, with the rest coming from the commercial partners  Thales, NATS and Roke Manor Research.

“The funding that we have secured today from the Technology Strategy Board is a significant endorsement of the potential long-term benefits of this research,” said Marion Broughton, head of Thales UK’s aerospace business. “Although in its infancy, this innovative application of new technology could reshape the way that air traffic is managed in the future. This is a good example of how Government and industry can work together, share expertise, and sustain innovation and high-technology research within the UK”.

EE is currently the UK’s only 4G operator but Ofcom has already started to plan for the next next-generation of mobile networks. It has identified spectrum in the 700MHz bandwidth used for digital terrestrial television that could be freed up in time for 2018 and used for 5G services.

Last year, TechWeekEurope revealed a trial of 5G services is set to go ahead in the UK in 2013, which should offer users speeds of up to 200Mbps. That will be delivered by the £35 million 5G Innovation Centre, based at the University of Surrey.

Peter Judge contributed to this story.

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  1. As I understand it, in the US almost all of the primary (skin-paint) radars are already turned off — everything relies on transponders on the airplanes.

  2. Wouldn’t it also be possible to read localized variations in the earth’s magnetic field to extract position, direction and velocity?