# Practical Use of Starlink Downlink Tones for Positioning
###### Abstract  
The large availability of Low Earth Orbit (LEO) satellite systems makes them useful beyond their original purposes, such as in positioning, where their signals can be passively used. In order to determine their potential for this purpose, newly deployed systems need to be investigated. This is the case with the Starlink system, which has a large constellation and is advantageous for positioning. It transmits signals in the 10.7-12.7 GHz band, the same as that of geostationary satellite television. Signals in this band are typically received using a low-noise block down-converter (LNB) and a parabolic antenna reflector. Regarding opportunistic use of these signals in small vehicle navigation, the dimensions of the parabolic reflector and its directional gain are not practical for tracking many satellites simultaneously. In this paper, we investigate the feasibility of tracking Starlink downlink tones for opportunistic positioning in a practical situation, when signals are received without a parabolic reflector. For this purpose, an inexpensive universal LNB is selected, and then signal tracking is performed to determine the signal and frequency measurement quality, as well as the number of satellites that can be tracked simultaneously. Next, the tone measurements are aggregated to handle tracking interruptions and to recover the traditional Doppler shift model. After that, the use of measurements in multi-epoch positioning is defined, and its performance discussed as a function of the relevant measurement rate and the required multi-epoch interval duration. The results showed promising positioning which can be improved by selecting a better-quality LNB. os 2023233  
to GNSS. LEO-SOP is the most prevalent in the literature thanks to the availability of operational systems such as Iridium-Next, Orbcomm [10], and Globalstar [11]. Early research projects using LEO systems for navigation have shown promising positioning results. In [12], experiments based on data from two Orbcomm satellites and assuming a known altitude exhibited a 2D positioning error of 358 m for a static user. In [13], an experiment using 4 min of data for 2 Orbcomm satellites have led to a positioning accuracy of a few hundred meters for a land vehicle. In [14], experiments showed a positioning accuracy of 25 m with Iridium in differential positioning mode in a static location. Specifically, a review of the existing literature on LEO-SOP shows advanced work covering various positioning types. A first class of LEO satellite-based navigation techniques uses only LEO satellite signals in which the positioning can be either autonomous [15; 16] or in differential mode [14; 17]. It can be based on the carrier phase [18] or on Doppler-shift measurements [15; 16]. A second class performs a coupling between LEO satellite measurements and an IMU (gyroscopes and accelerometers) [19; 20] with magnetometers [21]. In general, tight coupling is considered due to the weak satellite visibility from operational LEO systems that makes it difficult to determine a standalone positioning. In both categories, navigation is either single- or multi-constellation, where measurements from two or more LEO systems are coupled to cope with the limited availability of LEO satellites from existing systems [12; 22]. In general, operational constellations such as Iridium, Orbcomm, and Globalstar are used, however the advent of \"super-constellations\" such as Starlink is likely to improve positioning quality and availability. Recently, the use of Starlink as an SOP has gained interest thanks to rapid constellation deployment [23; 24; 25]. The Starlink downlink signal has several channels with large bandwidths (240 MHz) in the 10.7-12.7 GHz frequency band [26]. Within this band, there are multiple tones in a few bandwidths of \(\sim\)1 MHz, which have been observed in many satellite signals. One of the barriers to using a new system as an SOP for navigation is the unknown structure of the signal, as it is usually not made public.