Positioning Accuracy Improvement With Differential Correlation

The success of satellite navigation in the mass consumer market will depend greatly on its performance in deep urban and moderate indoor environments. The signal obstructions in these environments lead to low signal-to-noise ratios, which substantially degrade the positioning accuracy of GPS and Galileo receivers. New ranging techniques are required to increase the positioning accuracy to an acceptable level for pedestrian navigation in urban and indoor environments. Differential correlation is such a new ranging technique. It can replace the state-of-the-art noncoherent integration with very little implementation overheads. It improves performance as it utilizes the statistical properties of GPS and Galileo signals. This paper analyzes the resulting positioning accuracy for GPS and Galileo receivers when differential correlation is utilized. The probability density functions for early-late code discrimination with differential correlation are algebraically derived in closed form. The resulting positioning accuracies are presented for signals with binary phase shift keying (BPSK) and binary offset carrier (BOC) modulation in a large variety of reception conditions. The results indicate that differential correlation can replace noncoherent integration for all relevant configurations of GPS and Galileo receivers. It increases the accuracy of the measured receiver-to-satellite distances by 40% to 77% when compared to noncoherent integration.