Channel state information acquisition for line-of-sight MIMO feeder links in multibeam satellite systems

A ground receiver system, comprising:

• one or more processors;
• and
• one or more non-transitory computer-readable storage mediums storing instructions that, when executed by the one or more processors, cause the ground receiver system to perform operations comprising:
• receiving, by multiple receivers of multiple gateways of the ground receiver system, from multiple transmitters of a satellite over a downlink of a line-of-sight (LoS) multiple-input multiple-output (MIMO) feeder link, multiple radio frequency (RF) signals;
• obtaining, from the RF signals, preamble signals and pilot signals, the pilot signals including first sequences of pilot symbols associated with second sequences of pilot symbols transmitted by the transmitters;
• estimating, based on the first sequences of pilot symbols and the second sequences of pilot symbols, first channel state information (CSI) of the pilot signals;
• estimating, using the first CSI of the pilot signals, frequency offsets and phase offsets of links between the receivers and the transmitters;
• adjusting, based at least on the frequency offsets and the phase offsets, the preamble signals to obtain adjusted preamble signals;
• and
• estimating, using the adjusted preamble signals, second CSI of the downlink;
• and
• wherein the first sequences of pilot symbols correspond to a transformation of the second sequences of pilot symbols induced by transmission interference over the downlink of the LoS MIMO feeder link.