Fade depth prediction on wireless microwave links using two-ray multipath model

Fade depth prediction for airborne communication links is considered in this paper. There is no fading model for this specific scenario at the moment. The two closest models are the Olsen-Segal model for terrestrial links and the ITU-R model for satellite links. However, they cannot be directly applied to the airborne scenario. We propose a two-ray multipath fading model adapted to a realistic scenario of hilly or mountainous terrain, which applies to elevations angles higher than 2° and frequencies lower than 10 GHz, when the contribution of ground multipath component is dominant. It is interesting to note that the two-ray model predicts roughly the same fade depth dependence on the path clearance angle as the Olsen-Segal model, which may be considered as a theoretical justification, as to the best of our knowledge- for the first time, of the path elevation angle factor in that model. We further propose a hybrid approach to account for the atmospheric contribution to the total fade depth