D.A. Karavaev1

1 The Bonch-Bruevich Saint Petersburg State University of Telecommunications (St. Petersburg, Russia)

1 d.a.karavaev@yandex.ru

The current stage of development of fifth-generation 5G mobile communication systems is the migration of radio access network elements to spacecraft in order to provide high-speed services in regions remote from major terrestrial infrastructure. In the case of a mobile downlink communication session scenario from a spacecraft (SC) to a user terminal (UT), multipath propagation effects may arise due to the reception of signal copies (rays) reflected from objects in the terrestrial environment surrounding the UT. The aim of this work is to analyze the interference impact of such a multipath radio channel on 5G signals. The presented results are based on a previously introduced statistical model that accounts for the directional nature of the arriving reflected rays, owing to the use of a highly directional receiving antenna at the UT, employed to meet the link budget requirements for broadband communication. To characterize the rate of fading occurring in the radio channel, an expression for its coherence time was derived. The question of determining the bounds of applicability of the stationarity assumption for the modeled radio channel was discussed, since the shape of the underlying Doppler power profile vary considerably depending on the antenna pointing angles of the UT toward the SC relative to its direction of motion. An analytical expression for the inter-carrier interference (ICI) power was obtained for OFDM signals – a class to which 5G signals belong – propagating through the radio channel. The derived radio channel characteristics for a typical communication session scenario indicate slow fading conditions and negligible inter-carrier interference, which is attributed to the filtering property of the aggregate Doppler spectrum of the reflected rays imposed by the highly directional antenna. A real-time simulation model of the radio channel is presented, implemented on a field-programmable gate array (FPGA) integrated within a low-cost software-defined radio (SDR) transceiver platform. The resulting simulation model is applicable to the evaluation of communication sys-tem equipment with respect to its interference robustness.

Karavaev D.A. Modeling of multipath downlink channel with directional reception in 5G NTN satellite communication systems // Electromagnetic waves and electronic systems. 2026. V. 31. № 4. P. 81−93. DOI: https://doi.org/10.18127/j15604128-202604-07

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