Recent Increase in Rain Attenuation Statistics of Ku-Band Satellite Communications Links

The rain attenuation statistics obtained from Ku- band satellite signal for the recent 13 years after 2007 at Osaka, Japan, indicate the cumulative time percentages considerably exceeding the ITU-R predictions. These are caused by the increase in the horizontal reduction factor and the vertical adjustment factor of the ITU-R predictions. The increase in the vertical adjustment factor up to the ratio of 1.36 is found to be related to the average equivalent path length in each rainfall event, while the increase in horizontal reduction factor up to the ratio of 1.10 is related to the duration time of 5 dB attenuation. With these revisions of the factors, the ITU-R predictions show good agreement with the cumulative time percentages observed from 2007 to 2019.