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talk by Dr. Michael Walter – Mobile-to-Mobile Scatter Channels

Telecommunications / News / talk by Dr. Michael Walter – Mobile-to-Mobile Scatter Channels
04. July 2025
talk by Dr. Michael Walter from the Institute of Communications and Navigation at the German Aerospace Center (DLR)

Date: Friday July 4, 2025
Time: 11:00am
Place: seminar room 389 (CG0118)

szenario_2024

Abstract: In this talk we present differential geometric concepts for future mobile-to- mobile channel models. Those concepts enable the audience to generalize the propagation channel description and apply it to different mobile-to- mobile scenarios. The geometric description allows for a non-stationary probabilistic model, which incorporates high mobility scenarios. These are very important in future communication systems. Hereby, the mathematical concepts are similar to the theory of general relativity. Differential forms and coordinate system transforms are part of a tensorial description of the channel. Our channel model for mobile-to-mobile channels is based on two important mathematical concepts: prolate spheroidal coordinates and differential forms. Furthermore, both the coordinate transform and the differential forms can be uniformly described by the tensor theory. We use co- and contravariant tensors to express both the gradient of the Doppler frequency in prolate spheroidal coordinates. Differential forms are used to calculate the scattering area in a uniform way. Another important mathematical concept presented in this talk is algebraic curves; the mathematician Adrew Wiles Fermat’s used such curves to prove Fermat’s last theorem and certain algebraic curves, i.e., elliptic curves are nowadays used in cryptography. We apply the theory of algebraic curves to obtain a polynomial description of the Doppler frequency.In the second part of the talk, we introduce a complete analytic probability-based description of mobile-to-mobile uncorrelated scatter channels. We show that the description is equivalent to the correlation-based description introduced by Bello and Matz. This equivalence is evaluated through a comparison of the hybrid characteristic probability density with the correlation-based description of a measured generic mobile-to-mobile channel, both of which can be obtained directly either from theory or from measurement data. The comparison confirms the similarity between the probability based and correlation-based description qualitatively and quantitatively. Thus, the proposed probabilistic description complements the common correlation-based description providing a comprehensive theoretical description of arbitrary uncorrelated scatter channels.

Biography: Michael Walter received his Dipl.-Ing. and Dr.-Ing. degree in electrical engineering from Ulm University, Germany, in 2008 and 2015. Since 2009 he has been a member of the scientific staff at the Institute of Communications and Navigation at the German Aerospace Center (DLR) in Oberpfaffenhofen, Germany, where he gained extensive experience in organizing and conducting numerous measurement campaigns for vehicular and aeronautical research. He was a visiting scholar at the School of Electrical and Computer Engineering at the Georgia Institute of Technology in 2014. His research interests include wireless communications, mobile-to-mobile channel models, prolate spheroidal coordinates, differential forms, and algebraic curves. Dr. Walter was the recipient of the IEEE/AIAA David Lubkowski Memorial for Advancement in Digital Avionics Best Paper Award of the 29th DASC in 2011. He is the co-chair of the IEEE P1944 UAV and V2V channel modeling subgroup and a member of the IEEE VTS propagation committee.

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