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Novel Greedy Solution to Interference Wins Best Paper Award

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Published on Wednesday, 10 October 2018

Some 130 years after the invention of wireless communication, we now take services such as satellite navigation and international phone calls for granted. But beaming data thousands of miles into space and back continues to pose numerous challenges. How, for example, to deal with the inevitable loss of data caused by interference from other signals and environmental disturbances? Dr. Farbod Kayhan at the Interdisciplinary Centre for Security, Reliability and Trust received a prestigious Best Paper Award for his novel “greedy” solution to a key aspect of this problem.

“When you send a message via satellite, you need to add some extra data, or bits, at the end of the message. The receiver compares these with the message to check its validity,” says Kayhan, lead author of the paper, Code Design for Non-Coherent Detection of Frame Headers in Precoded Satellite Systems. “Our work looks at just how many bits we need to add to ensure that the receiver can decode a message even if some of the data has gone missing or been changed.”

Kayhan’s work focusses on a situation, called non-coherent detection, where something alters the phase of the waves being used to transmit the data. The receiver isn’t aware of the change, so a message that looks like 00, 01, 10, 11 at the transmitter could flip and become 10, 00, 11, 01 at the receiver – a bit like it has all been rotated 90 degrees.

Dr. Sandro Scalise (German Aerospace Center, Institute of Communications and Navigation) and Dr. Farbod Kayhan

Whereas existing solutions try to treat the message as a whole, Kayhan’s “greedy” solution looks at every “bit” individually, calculating the probability of error for that bit and choosing the optimal number of extra bits needed to account for this. The result is that for a message of eight bits the transmitter might need to add some 200. The extra effort, though, is worth it, says Kayhan. “A message can be thousands of bits long, but at the beginning you send a short “physical layer header”, which tells the receiver exactly how the message has been coded. If part of the header header goes missing or gets changed, then all the subsequent data is worthless. So our greedy solution – which ensures accuracy – is ideal for this sensitive information.”

In recognition of their novel solution, Kayhan, along with co-author prof. Guido Montorsi, Politecnico di Torino, received the prestigious Best Paper Award at the joint 2018 Advanced Satellite Multimedia Systems Conference and Signal Processing for Space Communications Workshop in Berlin in September.

The research was part of the European Space Agency’s OPTIMUS project to develop a new interface for precoded satellite communications. Kayhan and Montorsi’s code has helped the project realise its aim of making improvements on key performance indicators such as capacity and latency.