Signal Mode Transition Detection in Starlink LEO Satellite Downlink Signals

A receiver architecture for detection and tracking of Starlink orthogonal frequency division multiplexing (OFDM)-based signals is proposed. The proposed receiver enables exploiting all the transmitted periodic beacons of Starlink low Earth orbit (LEO) signals to draw carrier phase, code phase, and Doppler observables. The reference signals (RSs) of modern OFDM-based systems contain both always-on and on-demand components. These components can be unknown and subject to dynamic transmission modes. Thanks to a matched subspace-based detection algorithm, the proposed receiver is shown to be capable of cognitive detection of both always-on and on-demand components in the Starlink OFDM-based RSs. It is shown that despite the dynamic nature of Starlink RSs, the proposed matched subspace detector senses the transition between the transmission modes of Starlink RSs, and detects all the accessible RSs with a predetermined probability of false alarm. Experimental results are provided to validate the performance of the proposed receiver in transmission mode detection in Starlink downlink signals.