40 gigabit per second wireless link and the possibility of even faster communication

Researchers of the Fraunhofer Institute for Applied Solid State Physics and the Karlsruhe Institute for Technology have achieved the wireless transmission of 40 Gbit/s at 240 GHz over a distance of one kilometer. Their most recent demonstration sets a new world record and ties in seamlessly with the capacity of optical fiber transmission. In the future, such radio links will be able to close gaps in providing broadband internet by supplementing the network in rural areas and places which are difficult to access.

A distance of over one kilometer has already been covered by using a long range demonstrator between two skyscrapers in Karlsruhe. (Photo: Ulrich Lewark / KIT)

High Frequencies enable Fast Data Transmission

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 elec-tronic circuits and antennae scales with frequency / wavelength, the transmitter and receiver chip only measures 4 x 1.5 mm². The semi-conductor technology developed at Fraunhofer IAF, based on tran-sistors 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 at-mosphere 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.

The high frequency chip only measures 4 x 1.5 mm², as the size of electronic devices scales with frequency / wavelength. Photo: Sandra Iselin / Fraunhofer IAF

Up to now, radio links were not able to directly transmit the data rates of glass fiber. 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 the so-called bit transparency, i.e. the signal of a glass fiber could be fed directly and without energy-consuming transcoding into a radio link. It could then be transmitted and redirected into a glass fiber. The record data from the test setup is only the beginning. “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. This could give new impetus to the expansion of the broadband network. Maybe Germany will then no longer occupy the lower ranks compared to the rest of Europe.

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