Wireless data transmission tops 40Gb/s at 240GHz

Researchers at the Fraunhofer Institute for Applied Solid State Physics and the Karlsruhe Institute for Technology have demonstrated a wireless transmission of 40Gb/s at 240GHz over a distance of 1km. According to them, this sets a world record and ties in seamlessly with the capacity of optical fibre 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 that are difficult to access, they added.

The researchers indicated that the wireless data transmission equals the transmission of a complete DVD in under a second or 2400 DSL16000 internet connections. Distances of more than 1km have 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. "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," said Ingmar Kallfass, who coordinated the project at Fraunhofer IAF within the scope of a Shared Professorship between IAF and KIT.

Using the high frequency range from 200-280GHz 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 1.5mm². The semiconductor technology developed at Fraunhofer IAF, based on transistors with high carrier mobility (HEMT), makes it possible to use the frequency from 200-280GHz with active transmitters and receivers in the form of compact ICs. The atmosphere shows low attenuation in this frequency range that 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," noted Jochen Antes of KIT.

Up to now, radio links were not able to directly transmit the data rates of glass fibre. 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 fibre could be fed directly and without energy-consuming transcoding into a radio link. It could then be transmitted and redirected into a glass fibre.

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," stated 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.