Theoretical analysis of S-curve for GNSS system

The GPS system improvement and the Galileo system development will increase the signal availability and therefore the GNSS system-based applications. The great evolution of GNSS based application will imply the growth of precise and fast navigation systems. The performances of GNSS systems are mostly influenced by the accuracy of the synchronization modules. In fact, loss of fine tracking means a less precise position estimation. In urban environment the receiver measurement is usually affected by errors, especially caused by multipath fading. For this cause could be useful to analyze the performances of different methodologies to solve this problem proposed in literature. In this paper, a theoretical model valid for the analysis of synchronization performances in GNSS receivers in a urban environment is proposed. The proposed model is studied under the presence of two important cause of disturbances, named gaussian noise and multipath, in the received signal. In general the S-curve is shown in the ideal case, without any source of noise. A model can permit to recognise the presence of different type of noise that act on the received signal. The validation of the method will be made comparing results derived from signals from a simulated environment with the theoretical model. Performed tests have pointed out the validity of the theoretical model in a real case.