A two-component rain model for the prediction of attenuation statistics

A new model is presented for the calculation of the probability of exceeding specified attenuation values due to rain on single earth-satellite or terrestrial propagation paths. The model was formulated to explore a prediction procedure that differs significantly from most of the accepted models for attenuation prediction but holds considerable promise for extension to modeling the joint statistics required for space diversity system design, the statistics of interference due to rain scatter at attenuating frequencies, and the duration statistics for attenuation events. The new procedure calculates the probability of occurrence of a convective (volume) cell or widespread debris which could cause the specified value of attenuation. The performance of the new model was evaluated by comparison with observed attenuation statistics and by comparison with the performance of the recently adopted International Radio Consultative Committee (CCIR) model and the earlier global model. The results of the comparison show that the new, two-component model performs as well as the other models for prediction on earth-satellite paths. It is the promise of the application of the new model to the unsolved problems of diversity improvement and interference prediction, however, that justifies the consideration of yet another model.