A Software Defined Receiver for GNSS/INS Ultra-Tight Coupling Simulation

The performance of navigation can be significantly enhanced by coupling the Global Navigation Satellite System (GNSS) and the Inertial Navigation System (INS) because the characteristics of these two systems complement each other. Among those structures of coupling, Ultra-Tight Coupling (UTC) fully uses the information of both systems, therefore has attracted much attention of researchers. To do researches of UTC, it is reasonable that the simulation platform should be built first. Although there have been several open source simulation platforms for the researches of Tight Coupling (TC), which have become important tools for the analysis of TC, the researches about designing simulation platform of UTC is rare, and the standard of simulation has not been settled either, becoming a barrier of the development of UTC. In this paper, a Software Defined Receiver (SDR) for UTC simulation is proposed. The SDR is derived from the open source code of TC SDR with many modules added, including the GNSS signal generation, transmitting, acquisition, and tracking. The tracking results of receiver are transformed to the errors of pseudo-range, and then used in the Extended Kalman Filter (EKF) for coupling. The output of EKF on the other hand adjusts the INS and the loop of GNSS as feedback. The design of SDR for UTC does not need to simulate the navigation data, hence is easy to be realized. The simulation results are also presented to show the validity of the designed SDR.