Mitigating interferences on LEO satellite downlinks of Earth exploration services by cognitive radio, adaptive modulation and coding techniques

Upcoming Earth Exploration Satellite Services (EESS) missions, especially to monitor Brazilian diversified biomes, will require progressively higher data rates for downlink transmissions, besides the ability to share its frequency spectrum with cellular base stations. Both impact issues on spectral efficiency (in bps/Hz) and coexistence in frequency, time, location, etc. This paper proposes a technique suitable for LEO Earth Observation Satellites (EOS) by combining two strategies. We initially present the Cognitive Radio (CR) spectrum awareness and exploitation approaches to propose techniques for improving their uses. Next, we detail the Adaptive MODulation and CODing (MODCOD) techniques (ACM) based on DVB-S2X systems to increase RF power and spectral efficiencies. Finally, we evaluate our solution by monitoring the Signal to Interference plus Noise Ratio (SINR) and combining CR/MODCOD techniques. Two case studies are presented that demonstrate the proposed approach on Brazilian satellites developed by the National Institute for Space Research (INPE). A real in-situ characterization of the interfering scenarios was performed during the passes of the two EESS satellites that proves the effectiveness of spectral efficiency and coexistence.