BDS/QZSS integrated PPPAR time–frequency transfer

Based on BeiDou navigation satellite system (BDS), the Quasi-Zenith satellite system (QZSS) was added to assist in studying the precise point positioning (PPP) time and frequency transfer effect. Ambiguity resolution (AR) is the key to the rapid conversion of the PPP method. Therefore, this paper also used the ionospheric-free combination and the observable-specific signal bias (OSB) product of Wuhan University to test the time–frequency transfer effect of BDS ambiguity-fixed. In this way, BDS PPP, BDS + QZSS PPP, BDS PPP-AR, and global positioning system (GPS) PPP methods were formed. Six stations located in Japan and Australia were selected for experiments. Conclusion: BDS can reach the same level as GPS; when the cut-off angle is greater than 15°, adding QZSS could improve the success rate, accuracy, and frequency stability of the solution of time links effectively; the ambiguity fixed strategy can improve the time transfer accuracy but not the short-term frequency stability.