Round Trip Time (RTT) and Doppler Measurements for IoRT Localization by a Single-Satellite

Accurate node localization holds prime significance across a range of future network applications. In this letter, we present a novel scheme for instantaneous localization of static Internet-of-Remote-Things (IoRT) terminals from the satellite/network side, employing a single-channel probing by a single-antenna-equipped single-orbiter. Our method measures both Round Trip Time (RTT) and Doppler shift, which aid the proposed localization scheme. A geometric framework to establish a probabilistic relationship between satellite Transmit (Tx) and Receive (Rx) positions with the target IoRT terminal location is proposed. The key steps of the proposed framework are summarized in an algorithmic form. Precise IoRT node positioning relies on the accurate estimation of RTT, Doppler shift, and satellite position. For instance, at a 200km satellite altitude and precise satellite positioning, an error of 1.25Hz in Doppler and
$0.0125~\mu $
sec in RTT estimation translates into a positioning error of 7.081m. Notably, this error increases with an increase in satellite altitude, making the proposed scheme better suited for lower-altitude satellites.