Satellite Pre-coding Clears Congested Airwaves
13 November 2019
“Buy land, they’re not making any more of it.” Mark Twain’s famous advice was probably sound for the generation that came after him. But then, things changed.
While land remains a finite resource, the way we use it would hardly be recognisable to Twain. We work and live, for example, in buildings hundreds of meters taller than anything he could have imagined. Yes, physical space remains finite. It is the way we relate to that space and use it that has changed dramatically.
Like land, the radio frequency spectrum, including the frequencies used for satellite communications, is also a finite resource. And each year, the demands we put on it have been increasing; telecommunications companies have been preparing for a coming frequency crunch. But thanks to SnT’s SERENADE project, they might not need to look quite as far to find the satellite bandwidth they need — because the way they utilise frequencies they already have is about to change.
Up to now, telecoms have had to minimise interference by leaving dedicated buffer frequencies empty and then sending only one signal on a frequency at a time. Last year, however, the FNR-funded project SERENADE, led by Prof. Dr Symeon Chatzinotas with Dr Juan Carlos Merlano Duncan, developed a method of altering wavelengths to cancel out the anticipated inference, leaving simultaneous messages crystal clear.
These precise alterations, called “pre-coding”, are calculated based on interference information received along with test signals already being sent for synchronisation purposes. Moreover, this pre-coding does not require any alterations to existing satellites — it can be accomplished with simple processing power upgrades at the earthbound transmitter.
Pre-coding transmissions in this way allow multiple transmissions to be sent simultaneously on the same frequency. The end effect for frequencies is like that of the skyscraper for land: you can layer multiple transmissions on top of each other. Just as skyscrapers have elevators with buttons to reach the floor you need, these layered transmissions arrive with the keys needed to clean up the signal to focus on any given one. This means telecoms can make significantly better use of their allocated frequencies.
Together with SES and Airbus, and with funding from the European Space Agency, SnT’s LiveSatPreDem project is implementing the theoretical framework produced by SERENADE. So perhaps very soon we can expect a significant improvement in the quality of Internet on airplanes, boats, and in remote regions — or more prosaically, as Dr Nicola Maturo, researcher on the LiveSat project said with a smile, “with these data-capacity improvements, before long we will be able to receive a lot more channels on Ultra-HD satellite TV.”
Read the original article on the SnT website.