Doppler Shift in Precoded Cooperative Multi-Gateway Satellite Systems: Effects and Mitigation

Very High Throughput Satellite (VHTS) systems are typically deployed in Geostationary (GEO) orbit to benefit from the ubiquitous coverage of such orbits. Although the satellites deployed in GEO orbits appear as a static point in the sky from the on-ground user perspective, in practice, the GEO satellite experiences a north-south drift due to the influence of the sun and moon. Such movement may cause a small Doppler effect in the signals sent from geographically distributed cooperative gateways, which may cause significant performance loss when exploiting DVB-S2X SF-Pilot fields and for precoding purposes. This paper presents the first work investigating the effect of GEO Doppler shift in precoded cooperative multi-gateway satellite systems. In addition, to compensate for the frequency variations produced by the GEO movement, we present and test a user-gateway closed-loop compensation procedure. Results using software-defined radio (SDR) in the Lab are provided to validate the proposed method.