Summary For data downloading from satellites, the traditional approach of considering the complementary probability distribution, P(Atrop) of the total tropospheric attenuation Atrop (dB), at a frequency, polarization, and elevation angle, may be too pessimistic, and it may lead to large overdesign. If the data volume downloaded in a given observation time Tobs (a day, a week, a month, etc.), with a constant probability of symbol error, is more valuable than the instantaneous symbol, or bit rate (as it may be the case in Earth resources observation or in other services that allow long delays in communicating data), another approach can avoid overdesign, namely the various adaptive coding and modulation techniques. We study a particular time integral of Atrop(t): (i) to define the average efficiency of a radio channel faded by the troposphere and (ii) to design a method that can theoretically achieve the same volume of data downloaded in clear-sky conditions (no troposphere), even if the radio link is faded by the troposphere. The average efficiency and its bounds can be calculated from the complementary probability distribution of Atrop(t). We explicitly apply the theory to radio links faded by rain, by using the experimental rain-attenuation time series measured with satellite ITALSAT in a 37.8° slant path, at 18.7, 39.6, and 49.5 GHz at Spino d'Adda (Italy), and to those simulated with the synthetic storm technique. Based on the average efficiency, we define the method that can achieve in Tobs, theoretically, the same data volume as in clear sky, directly applicable to quadrature phase-shift keying, multiple phase-shift keying, and Shannon capacity theorem. The method requires a fixed increase in power margin, and bandwidth, compared with clear-sky conditions, and delivers an average symbol rate equal to the maximum symbol rate obtainable when Atrop(t) = 0. The method can also be used in terrestrial links at any frequency. We compare its theoretical performance with the traditional adaptive coding and modulation techniques and show that, even theoretically, these techniques cannot achieve unitary efficiency as, on the contrary, the novel method can do. Copyright © 2015 John Wiley & Sons, Ltd.