Researchers of the German research institutions Fraunhofer Institute for Applied Solid State Physics (IAF) and the Karlsruhe Institute for Technology (KIT) say they have achieved the wireless transmission of 40 Gbps at 240 GHz over a distance of one kilometre.
They say this sets a new 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 which are difficult to access.”
So, even at that speed, the researchers see wireless as a supplement to, rather than a replacement for, fibre.
“The changing media usage habits of modern society require the faster transmission of increasing volumes of data,” said Professor Ingmar Kallfass, who coordinated the project. ”Deploying new fibre-optic cables is expensive and difficult when there are natural or urban obstacles such as rivers or traffic junctions.
“Broadband radio links can help to overcome such critical areas, thereby facilitating the expansion of the network infrastructures. In rural areas they can be a cost-effective and flexible alternative to FTTH.”
The test involved transmitters and receivers operating in the 240 GHz band, which allows the transmission of data rates of up to 40 Gbps, which is the equivalent of 2,400 ADSL connections. I would enable the transmission of a complete DVD in under one second.
The test involved transmission over one kilometre between two tall building is central Karlsruhe which the KIT set up as part of the ‘Millilink’ next generation broadband project, funded by €2 million from the German Federal Government.
“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 Professor Kallfass.
“Using the high frequency range between 200 and 280 GHz not only enables the fast transmission of large volumes of data,” said Kallfass, “but it also results in very compact technical assembly. Since the size of electronic circuits and antennae scales with frequency, the transmitter and receiver chip measures only 4 x 1.5 mm².”
The semiconductor technology developed at Fraunhofer IAF, 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,” said KIT’s Jochen Antes.
“Up to now, radio links were not able to directly transmit the data rates of glass fibre. This might change in the future. Such a high performance system would also have the advantage of the so-called bit transparency – 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.”
Antes said 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 – multiplexing, will help to achieve even higher data rates. Other possible applications are Indoor WLANs and intra-machine and board-to-board communication.”