VCM techniques for Ka-Band LEO satellites

The growing market of Earth Observation satellites, pushed by the scientific, institutional and commercial requests, is expected to congest in the future the allocated X-Band: considering the innovative and more demanding services and the sophisticated sensing techniques, very high downlink data rate will be needed, exceeding the capabilities of X-Band. Ka-Band represents the alternative to improve the performances of future EES missions in terms of data rate increase, interference minimization, and congestion risks. Given the very high dynamic between clear and rain sky condition and/or when elevation angle increase and the usage of steerable high gain antenna, Variable Coding Modulation (VCM) can highly improve the end-to-end performance ensured by a Constant coding Modulation (CCM system). In the frame of the ESA study [1] aimed to the definition of a Ka-Band downlink architecture, TAS-I has identified a VCM technique to optimize the transmission parameters (i.e. the spectral efficiency) according to the local statistics of atmospheric attenuation and Tsky provided by POLI-MI.