In disasters, rescuers usually communicate via satellite if phone and mobile telecommunication is out. But that has drawbacks: Once the data lines are overloaded, the connection disconnects. In addition, there barely are systems available yet for moving vehicles. Fraunhofer researchers have developed a new antenna system which reliably transmits data via satellite with a high-bandwidth and which is suitable for mobile use.
Natural disasters regularly strike the world. As in the case of the tsunami in Japan or the earthquake in Nepal, electricity and telephone lines are destroyed in this process as well. Usually, mobile communications fail over a large area because the poles are damaged. That is why during disasters, rescue services turn to their own communications technology – mostly over satellite systems. Data or phone calls are sent directly to a satellite in space and, from there, to receiving stations on Earth. As a result, the rescue workers are not dependent on the communications infrastructure on the ground.
Until recently, satellite communication has had its disadvantages. The setting up of a small satellite station in the field takes some time for example. Once built, it cannot be easily moved. Moreover, the connection breaks off when a lot of data has to be transmitted or when a thunderstorm interferes. The satellite antenna has to be aligned very precisely to the satellite – just like in the case of television. It is now virtually impossible to communicate with broadband in a moving car via satellite, since the antenna constantly moves out of focus due to the movement of the vehicle.
In the joint project KASYMOSA (Ka-band systems for mobile satellite communications), several research institutions have developed a number of technologies to make satellite communications fit for mobile use. The Fraunhofer Institute for Integrated Circuits IIS in Erlangen is involved with three working groups. For mobile communications, researchers have to overcome several hurdles. The first issue is to shift and position the satellite antenna on a moving car quickly enough so that it always keeps the satellites in view. This involves high precision: it can only move by a maximum of 0.2 degrees from the focus of the satellite. Even just getting into a car moves it more, though. The partners have therefore developed algorithms for a mechanism which can move the antenna precisely and quickly. They control the movement of the antenna precisely so that it compensates for a change in direction within fractions of a second.