The Satellite Navigation System Simulation

Global Positioning System (GPS) plays an important role in military and civil use by providing services of high precision positioning, velocity and timing in all weathers and all-day. Up to now, the number of applications of the GPS system is larger than we can count. Such diverse applications give rise to some widely varied requirements on receivers and the effectiveness of algorithms. It is therefore useful to be able to confirm the performance of a GPS Receiver for a particular application before investing on the actual hardware and test the impact of various system parameters and the effectiveness of algorithms. In order to meet the requirements above, building simulation system is a good solution. This dissertation is devoted to the GPS simulation. The main work and research are listed as follows.A series of reference system: time, coordinates system and force mode system are expounded in detail, which compose of the base of GPS simulation. In order to calculate the satellite position, satellite velocity, satellite acceleration and partial derivatives of the acceleration conveniently anytime, a so-called Collocation integration method is used in the simulation of GPS constellation. Since GPS errors have a major impact on the performance of the simulation system, detailed methods for simulating GPS errors are discussed. These errors are due to tropospheric and ionospheric delays. There are many methods for troposphere and ionosphere delay modeling. In this research, the objective is to find a troposphere and ionospheric model which is valid for GPS simulation through comparison. This involves not only simulating the absolute troposphere and ionosphere delay along the line of sight of observations, but also modeling the irregular properties of the ionosphere. Herein, the EGNOS model and the spherical harmonics model have been proven to be effective in simulation. Then, the paper describes the simulating method of the GPS signal, including the prediction of the visible satellite, the level of the received satellite signal, the phase of the received satellite signal, Doppler frequency drift and the signal delay due to multi-path effects. Finally the static GPS data and the ground-based lower kinetic GPS data are simulated in this paper using the above method.