The ITU Radiocommunication Assembly considering a)that a better knowledge of the characteristics of propagation contributes greatly to the design of economic line-of-sight systems and to the improvement of system performance and in particular:–that the design of digital systems is largely controlled by the performance and the availability required (as related to propagation) and that periods of adverse propagation are significant to the design of digital systems;–that amplitude and group-delay distortions across a microwave radio channel have a profound effect on the bit error ratio of digital systems.
ITU-R QUESTION 204-4/3-2009 history
2009ITU-R QUESTION 204-4/3-2009 Propagation data and prediction methods required for terrestrial line-of-sight systems