German team sets record in terrestrial radio transmission
Researchers from the University of Stuttgart and the Fraunhofer Institute for Applied Solid State Physics IAF have exceeded the state of the art in terrestrial wireless transmission by a factor of ten.
They transmitted data at 6 Gigabit per second over a distance of 37km at a radio frequency of 71-76 GHz in the E band. Only in this frequency range are the required high effective bandwidths available.
This was part of collaborative project ACCESS (Advanced E Band Satellite Link Studies) carried out by a research group headed by Ingmar Kallfass from the Institute of Robust Power Semiconductor Systems (ILH) from the University of Stuttgart, the Institut fuer Hochfrequenztechnik und Elektronik (IHE) from KIT, Radiometer Physics GmbH, and the Fraunhofer Institute for Applied Solid State Physics IAF.
The team used transmitters and receivers based on two innovative transistor technologies developed and manufactured by Fraunhofer IAF. In the transmitter the broadband signals are amplified to a comparatively high transmission power of up to 1W with the help of GaN power amplifiers. A highly directive parabolic antenna emits the signals. Built into the receiver are low-noise amplifiers (LNAs) based on high-speed transistors using InGaAs semiconductor layers with very high electron mobility. They ensure the detection of the weak signals at high distance.
The team realised the record data transmission on a stretch between Cologne and the 36.7 km distant town of Wachtberg. The stations were located on the 45-story Uni-Center in Cologne and the site of the Space Observation Radar TIRA at the Fraunhofer Institute for High Frequency Physics and Radar Techniques FHR in Wachtberg.
The transmission of high quantities of data by radio over large distances serves many application areas. For example, next generation satellite communications will require an ever-increasing data offload from earth observation satellites down to earth. Supplying the rural area and remote regions with fast Internet is possible as shown in the trial. 250 Internet connections can be supplied with 24Mbps ADSL. Terrestrial radio transmissions in E-band are suitable as a cost-effective replacement for deployment of optical fibre or as ad-hoc networks in the case of crises and catastrophe, and for connecting basestations in the backhaul of mobile communication systems.
Developments such as the Internet of Things and Industry 4.0 will also demand unprecedented aggregated data quantities. Their processing and transmission in cloud-based services is already today taking the communication infrastructure to its limits. In satellite communication as well, the progress in earth observation and space research as well as plans for a planet-scale satellite network are leading to yet unsolved challenges for the communication infrastructure.
ACCESS was finished on April 30 and is being continued in the follow-up project ELIPSE (E Band Link Platform and Test for Satellite Communication). The aim is the next generation of communication systems for the fast connection of satellites. A further application, however, also lies in terrestrial fixed wireless links.
Along with the University of Stuttgart, the Fraunhofer Institute for Applied Solid State Physics IAF, and the Karlsruhe Institute of Technology (KIT), the industrial partner Radiometer Physics GmbH (A Rohde & Schwarz Company) is involved.
The project was funded by the Federal Ministry for Economy and Energy (BMWi) on the basis of a resolution by the German Bundestag. Support was provided by Fraunhofer FHR, the Uni-Center Cologne and the Suedwest-Rundfunk (SWR), who granted access to their buildings.
