Unveiling Starlink LEO Satellite OFDM-Like Signal Structure Enabling Precise Positioning

This letter unveils the unknown structure of Starlink low Earth orbit (LEO) satellites' orthogonal frequency division multiplexing (OFDM)-like reference signals (RSs). The spectrum of Starlink's downlink signals is presented, and the frame length is estimated. A blind receiver is proposed, which acquires via a sequential generalized likelihood ratio test multiple satellites, estimates their RSs and respective Doppler, and tracks their carrier and code phases. Experimental results are presented showing six tracked Starlink LEO satellites, three of which transmitted pure tones, whereas the other transmitted OFDM-like signals. The achieved horizontal positioning error with the six satellites was 6.5 m.