In disasters, rescuers usually communicate via satellite if the phone and mobile telecommunication are 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, although there are some antennas available that is supposed to improve but not eliminate the problem completely.
Internet users have become accustomed to a connection which is stable and which does not just break off when a lot of data is flowing over the line. If a person watches an HD movie or uses video calling, then, at most, the picture changes. It becomes grainier, more pix elated when the data line is heavily loaded — but rarely does the connection break off completely. The reason is that Internet technology is now designed so that it can control an application like the browser or Skype in such a way that the quality of the image is reduced but the functionality is preserved.
Connection without interruptions or dropouts:
With satellite communications that are not the case today. If the line is overloaded, it breaks off easily.TV viewers know that during storms, instead of their satellite image getting worse little by little, it just disappears suddenly. In other words, satellite communication has so far been lacking a continuous technology that controls the connection quality (like with the Internet) and adapts to the current utilization of the data line. Researchers have changed the data processing so that the data rate changes depending on the situation. For this purpose, a special modem has been developed for the transmission of the data.
“In this way, we achieve a very high bandwidth of several megabits per second,” says Raschke. “Of course, we don’t approach the Gigabit streams of a solid data line, but for satellite communication, it’s a big step.” Thanks to this technology, rescuers in the future will be able to send videos of the local situation and maps quickly, and without the connection breaking off. Just like you are used to from the Internet. And even clear satellite telephone calls without dropouts will be possible.
No central station required:
So far, individual senders can only connect with each other via a central hub. However, the newly developed modem now establishes direct connections. This contributes to data security not least because the transmitter and receiver now make direct contact with each other, and the data stream is no longer running through the hub.