ITU-R P.618/P.838 Rain-Attenuation Extension of 3GPP TR 38.811 Aligned GEO NTN-TDL Channel Model in OpenAirInterface5G

5G-NTN extends cellular connectivity through satellite systems, but realistic evaluation of such networks requires channel models that capture the distinct propagation characteristics of Earth-space links. Existing open-source end-to-end 5G NTN experimentation platforms provide limited support for standardized NTN channel models that jointly represent small-scale fading, elevation-dependent large-scale effects, LOS/NLOS conditions, and weather-dependent attenuation. This paper addresses this gap by developing a 3GPP TR 38.811-aligned GEO NTN tapped-delay-line channel model within the OpenAirInterface5G (OAI), supporting NTN-TDL-A/B/C/D profiles, LOS/NLOS-aware profile remapping, and elevation-dependent large-scale propagation effects. The model is further extended with ITU-R P.618/P.838 rain attenuation to capture frequency-, elevation-, and rain-rate-dependent rain loss. The implementation is validated through consistency checks, downlink and uplink BLER sweeps over S-, Ku-, and Ka-band frequencies and multiple elevation angles, and end-to-end OAI gNB/UE 5G SA attach experiments. Results show negligible rain impact at S-band, substantial degradation at Ku-band, and severe Ka-band impairment under heavy rain, with higher elevation angles consistently reducing the rain-induced loss. End-to-end RFsim experiments further confirm successful 5G SA attachment while preserving the expected LOS/NLOS channel-profile behavior under the tested rain conditions. The resulting implementation provides a reproducible, standards-aligned channel- and PHY-level environment for studying realistic GEO 5G-NTN propagation effects within OAI. The channel-model extensions are being prepared for integration into the OAI develop branch, with the aim of making them available to the broader OAI NTN community.

IEEE International Conference on Advanced Networks and Telecommunications Systems (ANTS 2026)