CONTRIBUTIONS TO THE CHARACTERIZATION OF THE INDOOR GPS PROPAGATION CHANNEL

Satellite-based positioning is nowadays experiencing an exponential growth of the consumer segment demand and the Global Positioning System (GPS) is the main provider of this service. While GPS performs very well in outdoor conditions, many people still cannot be located when they are in indoor environment. The characteristics of the indoor propagation are still not well understood and the question whether the GPS signals are good enough for indoor positioning is still open. Nevertheless, precise positioning is of great importance in numerous indoor activities, like underground mining or underground transport. The main limitations of the GPS use indoors are the low signal power and the presence of multipaths, which may affect significantly the signal acquisition and tracking accuracy. Indoors, there is also a high likelihood of non-line of sight signal propagation (i.e. when no line of sight signal is available, due to various obstructions in the propagation wave). The indoor signals are also likely to be much weaker than the outdoor signals, due to the propagation through building materials. In numerous situations, it is presumed that with the installation of pseudolites, indoor navigation can prove better performance. In this paper we analyze the indoor channel propagation using GPS pseudolites, based on the measurement data collected in measurement scenarios.