Navigation services from large constellations in low earth orbit

Very large satellite constellations in Low Earth Orbits (LEO) devoted to data broadcast could also help in providing navigation services. Lacking a specific payload onboard, the downlink can be exploited as a signal of opportunity, as an example looking at the carrier’s Doppler shift. The number of sources and the short distance to users, enabling indoor positioning, are significant advantages of this option. However, recent studies confirmed that commercially-oriented designs partly miss the advantage on the number of sources by directing just one or two beams at a given time to any area on the Earth: it is enough for communication services, it is not for navigation when several signals need to be received by the user at the same time. Looking at a possible service combining downlinks from more than one system to achieve the requested minimum of four signals, this work focusses on the dilution of precision proper to the novel concept. Therefore, the paper updates previous studies - concerning the effects of the orbital configuration of a single LEO system - extending the results to the new scenario.