Position and Measurement Accuracy Analysis of GNSS Receiver using LQG based Vector Tracking Algorithm

Abstract

With the expansion of the navigation by GNSS, various studies have been conducted to improve the performance of navigation. From GNSS receivers point of view, it can be possible to improve the performance of navigation by estimating more accurate position and measurements and developing more robust signal tracking loop in case of temporal signal block or decrement. To improve the accuracy of position and measurements, various studies based on estimation theory and control theory have been tried instead of using conventional loop filter. In this situation, through LQG theory, which combines optimal estimation theory, and optimal control theory, NCO inputs guarantee optimality under particular performance index. In addition, to improve the robustness of the signal tracking loop, vector tracking loop has been proposed. Eventually, by integrating LQG controller and vector tracking loop, LQG based vector tracking loop has been proposed as signal tracking loop. In this paper, simulation tool is developed to verify LQG based vector tracking loop in various conditions. First LQG based scalar tracking loop is designed to verify the performance of LQG controller. Measurements estimation errors in LQG based scalar tracking loop is smaller than those in LF based scalar tracking loop under various users dynamic. Second LQG based vector tracking loop is designed. From the simple case, only pseudorange measurement and position state, simulation expands the complex case like pseudorange, carrier phase, and Doppler measurements and position, velocity, and clock bias state. As the number of satellites increase, the position and measurements estimation errors decrease. Also measurements estimation errors decrease compared to LQG based scalar tracking loop. Finally, in case of temporal signal power reduction, LQG based vector tracking loop is more robust than conventional signal tracking loop. From this study, the performance of LQG based vector tracking loop is verified. Before applying LQG based vector tracking loop to GNSS receiver, performance analysis can be achieved rapidly using this simulation tool.