GPS Augmentation Using Japanese Quasi-Zenith Satellite System

The current GPS satellite constellation provides limited availability and capability for a country like Japan where mountainous terrain and urban canyons do not allow a clear skyline to the horizon. At present, the Japanese Quasi-Zenith Satellite System (QZSS) is under investigation through a government-private sector cooperation. QZSS is considered a multi-mission satellite system, as it is able to provide communication, broadcasting and positioning services for mobile users in a specified region with high elevation angle. The additional GPS compatible signals from QZSS can remarkably improve the availability, accuracy and capability of GPS positioning. This paper focuses on the performance of GPS augmentation using the proposed QZSS. The QZSS satellite constellation and signal structure are briefly reviewed. Positioning with pseudorange and carrier phase is analyzed. The performance of GPS augmentation using QZSS in the Asia-Pacific and Australian area is studied by software simulation. The results of simulation are presented using the number of visible satellites as a measure of availability, GDOP as a measure of accuracy, and ambiguity success rate as a measure of capability of carrier phase based positioning, with spatial and temporal variations. The results show that QZSS not only improves the availability and accuracy of GPS positioning, but also enhances the capability of carrier phase of positioning in Japan and its neighboring area.