A long range radio data transmission demonstrator between two skyscrapers in Karlsruhe (CREDIT: Ulrich Lewark)

Wireless data transmission world record set

A world record in wireless data transmission has been achieved by researchers in Germany.

A team of scientist from the Fraunhofer Institute for Applied Solid State Physics and the Karlsruhe Institute for Technology (KIT) have achieved wireless transmission of 40 Gbit/s at 240 GHz over a distance of one kilometre via radio transmitters and receivers, setting a new world record.

The achievement equals the transmission of a complete DVD in under a second and distances of over one kilometre have already been covered by using a long range demonstrator, which the Karlsruhe Institute of Technology set up between two skyscrapers as part of the project “Millilink”.

The researchers hope such high transmission radio links could help to close gaps in providing broadband internet, especially in rural areas, where deploying new fibre-optic cables is expensive and difficult due to natural or urban obstacles such as rivers or traffic junctions.

“We have managed to develop a radio link based on active electronic circuits, which enables similarly high data rates as in fibre-optic systems, therefore allowing seamless integration of the radio link,” says professor Ingmar Kallfass, who coordinated the project at Fraunhofer within the scope of a Shared Professorship between IAF and KIT. Since 2013, Kallfass is with the University of Stuttgart, where he continues to lead the project.

Using the high frequency range between 200 and 280 GHz not only enables the fast transmission of large volumes of data, but also results in very compact technical assembly.

Since the size of electronic circuits and antennae scales with frequency / wavelength, the transmitter and receiver chip only measures 4 x 1.5 mm².

The semiconductor technology developed at Fraunhofer, based on transistors with high carrier mobility (HEMT), makes it possible to use the frequency between 200 and 280 GHz with active transmitters and receivers in the form of compact, integrated circuits.

The atmosphere shows low attenuation in this frequency range, which enables broadband directional radio links.

“This makes our radio link easier to install compared to free-space optical systems for data transmission. It also shows better robustness in poor weather conditions such as fog or rain,” explains Jochen Antes of KIT.

Up to now, radio links were not able to directly transmit ate the data rates of glass fibre, but this might change in the future as the test setup of the project shows.

Such a high performance system would also have the advantage of so-called “bit transparency”, meaning the signal of a glass fibre could be fed directly and without energy-consuming transcoding into a radio link, transmitted and redirected into glass fibre at the other end.

“Improving the spectral efficiency by using more complex modulation formats or a combination of several channels, i.e. multiplexing, will help to achieve even higher data rates,” says Antes.

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