Framework for Rain Attenuation in mmWave Links Validated by Ray Tracing and Real Measurements

Millimeter-wave (mmWave) communication systems are highly sensitive to atmospheric conditions, particularly rain attenuation, which can significantly degrade link performance over multi-kilometer distances. Although analytical attenuation models and ray-tracing tools are widely used for propagation analysis, validating rain-induced degradation using real operational links remains challenging due to incomplete link-budget information, environmental uncertainties, and the lack of path-level validation methodologies. This paper presents a path-based framework for evaluating and validating rain-induced attenuation in mmWave links using real measurements, ray tracing, and ITU-R propagation models. The proposed methodology combines received signal level (RSL) measurements from operational OpenMesh links, Wireless InSite ray-tracing simulations, and path-level rain attenuation modeling based on ITU-R recommendations. Unlike conventional scalar approaches, rain attenuation is individually applied to each propagation path before coherent recombination, enabling a more physically consistent representation of weather-induced degradation. The framework is evaluated using real operational links operating at approximately 68GHz and compared against a lower-frequency 5GHz control scenario. Experimental results demonstrate strong attenuation during precipitation events at mmWave frequencies, while the 5GHz link exhibits significantly lower sensitivity to rainfall. The results also indicate that relative attenuation trends remain stable under moderate geometric perturbations, suggesting robustness to small deployment uncertainties. The proposed framework contributes toward scalable and physically grounded propagation modeling under weather variations, with potential applications in future weather-aware beam management, adaptive communication strategies, and AI-assisted wireless systems for mmWave and 6G networks.