Transmission power control of terrestrial pseudo satellite signal for global navigation satellite systems

In global navigation satellite systems (GNSS) such as Global Positioning System (GPS), we need signals from more than four satellites to find out the current three-dimensional location. However, the satellite visibility is occasionally blocked in city areas and the availability is decreased. In these areas, the ground placement of the pseudo satellite, or in short, pseudolite, has been proposed to augments the availability. It broadcasts the signal in the same format as the satellites broadcast, but it is known the signals from the satellites sometimes block by the pseudolite signal then, and the phenomenon is referred to as the near-far problem. Therefore, burst pulse-like transmission has been used for mitigating the average interference in the close proximity to the pseudolite, but the satellite signals remain unavailable to the users. In this paper, the coverage probability and the outage probability are analytically obtained where the receiver faces shadowing. Then a pseudolite with step-by-step transmission power reduction is proposed to enlarge the service area. Result showed the pseudolite with step-by-step power reduction outperformed the conventional burst pulse-like transmission pseudolite in terms of the coverage probability and the outage probability.