Knowledge of the propagation characteristics of wireless channels is of paramount importance for the design, analysis, and testing of dependable 6G communication schemes in highly mobile scenarios.
Multi band radio channel measurements and characterization
Although radio signals above 20 GHz can rely on the availability of a wider frequency spectrum, they require beamforming to compensate for stronger attenuation due to the shorter wavelength. According to current technology, direction finding for beamforming is time-consuming and can only be reliably implemented for stationary devices. In an international research collaboration with the University of Southern California, Brno University of Technology, and TU Wien, the first worldwide vehicular multiband measurements were conducted simultaneously at 3.2 GHz, 32 GHz, and 60 GHz to obtain an empirical foundation for advanced algorithm validation. The AIT channel sounder has been extended to the mmWave domain (30 GHz – 300 GHz) to obtain multi-band vehicular measurements [Hof22, Hof21, Mol24].
[Mol24] A. F. Molisch, C. F. Mecklenbräuker, T. Zemen, A. Prokeš, M. Hofer, F. Pasic, and H. Hammoud, “Millimeter-wave V2X channel measurements in urban environments,” in IEEE Open Journal on Vehicular Technology, vol. 6, pp. 520-541, December 2024, invited paper.
[Hof22] M. Hofer, D. Löschenbrand, S. Zelenbaba, A. Dakić, B. Rainer, and T. Zemen, “Wireless 3 GHz and 30 GHz vehicle-to-vehicle measurements in an urban street scenario,” in IEEE 96th Vehicular Technology Conference (VTC-Fall), London:Beijing, September 2022.
[Hof21] M. Hofer, D. Löschenbrand, J. Blumenstein, H. Groll, S. Zelenbaba, B. Rainer, L. Bernadó, J. Vychodil, T. Mikulasek, E. Zöchmann, S. Sangodoyin, H. Hammoud, R. Langwieser, S. Pratschner, A. Prokeš, A. Molisch, C. F. Mecklenbräuker, and T. Zemen, “Wireless vehicular multiband measurements in centimeterwave and millimeterwave bands,” in IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), virtual conference, September 2021.
Site-specific models of radio channels
6G technologies such as distributed MIMO systems, RIS, and multi-band communication require site-specific radio channel models that go beyond the current standardized models (3GPP). AIT leads the standardization activity IEEE P1944 on site-specific radio channel representation. An initial position paper with global participation has been published on this topic [Zem25].
For reliable train communication on branch lines using public 5G and 6G networks we have developed a site-specific radio channel models as digital twin. The digital twin has been calibrated with measurement data from a dedicated railway scenario [Hof23].
[Zem25] T. Zemen, J. Gomez-Ponce, A. Chandra, M. Walter, E. Aksoy, R. He, D. Matolak, M. Kim, J. Takada, S. Salous, R. Valenzuela, and A. F. Molisch, "Site-specific radio channel representation for 5G and 6G," in IEEE Communication Magazine, June 2025.
[Hof23] M. Hofer, D. Löschenbrand, S. Zelenbaba, G. Humer, B. Rainer and T. Zemen, “Massive MIMO channel measurements for a railway station scenario,” in IEEE Wireless Communications and Networking Conference (WCNC), Glasgow, Scotland, March 2023.
