Abstract:In the Ka-band satellite communications, the Adaptive Forward Error Correction ( AFEC ) is an ideal fade countermeasure for downlinks. In this paper, the system scheme of AFEC as a fade countermeasure is presented; Taking the complexity of application into account, an adaptive concatenated codes scheme structured by RS code as an outer code and variable rate punctured codes as inner codes combined with interleaver is recommended. The adaptive concatenated codes as an adaptive fade countermeasure ( AFCM ) can meet 99.8 percents of satellite downlinks availabilities in most area of China. Finally, the application scheme to choose codes is discussed.