Beam Tracking for Full-Duplex User Terminals in Low Earth Orbit Satellite Communication Systems

This paper introduces a novel beam tracking scheme for full-duplex ground user terminals aiming to transmit uplink and receive downlink from two low Earth orbit (LEO) satellites at the same time and same frequency. Our proposed technique leverages phenomena observed in recent measurements to strategically select transmit and receive beams which couple low selfinterference across the satellites' trajectories, thereby enabling in-band full-duplex operation. By taking a measurement-driven approach, our scheme circumvents the need for explicit selfinterference channel estimation and can inherently account for hardware nonidealities. We show that our proposed scheme reliably selects beams which spatially cancels self-interference to below the noise floor, avoiding the need for digital/analog cancellation. Simulation results using satellite and orbital parameters published in 3GPP and FCC filings show that this substantial reduction in self-interference does not prohibitively compromise beamforming gain, allowing user terminals to attain near-maximal SINRs, thus unlocking full-duplex operation.