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Date:  Wed, December 04, 2019
Time:  11:30am - 12:30pm
Location:  Holmes Hall 389
Speaker:  Dr. Ulrich Speidel, Professor, University of Auckland

Abstract:
Geostationary and medium earth orbit satellite links with nominal capacities between 1 Mbps and several hundred Mbps are still the only connectivity option for many islands in the Pacific and beyond, where such links are often shared by dozens to thousands of simultaneous users. User unhappiness about link performance abounds, and is usually seen as an engineering problem at the physical or at best at the data link layer. The talk examines the causes of the performance issues and argues that the problem is caused by TCP at the transport layer. We discuss why FEC between VSAT terminals isn't likely to help much in many cases, but point out ways in which coding at the network layer can support the transport layer. We also argue that existing VSAT terminal buffer dimensioning guidelines need a rethink, and question whether the common practice of blocking UDP over satellite links is truly justified.

Bio:
Ulrich Speidel began academic life as a physicist, never completed his diploma at the University of Erlangen-Nuremberg in Germany and instead graduated with an MSc from the University of Auckland in underwater acoustic signal processing for long distance global warming measurements in 1994 as his first degree. He has since haunted the corridors of Computer Science at Auckland as a bit of an alien: as a PhD student until 1998, and then since 2000 as a member of academic staff. He has taught courses ranging from theory to object oriented programming for the web and databases - with his natural research home in data communications, information theory, and related fields. He has umpteen publications, the odd citation he is proud of, is a member of the IEEE, served as a project associate professor at the University of Tokyo in 2010, and has had visiting appointments at MIT, the University of Victoria, Canada, the University of Johannesburg, and the University of Ulm in Germany. He has been involved in the supervision of 7 successful PhD and 8 MSc graduates, as well as of five successful guide dog puppies.