Considering Receiver Clock Modeling in PPP Time Transfer with BDS-3 Triple-Frequency Un-combined Observations

In this work, two models of precise time transfer are presented, firstly, based on the four-frequency un-combined observations of BDS-3, namely TF-UC1 (B1I/B3I/B2a) and TF-UC2 (B1I/B3I/B1C). Then, TF-UC1 and TF-UC2 time transfer with a receiver clock model are introduced and developed. In TF-UC1 and TF-UC2 models, except for the traditional coordinates, troposphere delay and receiver clock parameters, ionosphere delays are estimated as unknown parameters. In addition, receiver differential inter-frequency bias (IFB) are also estimated as parameters. The standard dual-frequency ionosphere-free model is also presented, named as DF-IF. To assess the performance of the two prosed models, datasets from iGMAS were employed. The experimental results show that the TF-UC1 and TF-UC2 models can be utilized for precise time transfer, with accuracy and stability identical to those of the DF-IF model. Furthermore, the performance of TF-UC1 and TF-UC2 models can be improved significantly by using a receiver clock model. The accuracy of TF-UC1 and TF-UC2 is improved approximately 16.6 and 17.7%, respectively, with the receiver clock model. Furthermore, the maximum of frequency stability is up to 79.4 and 80.3% for of TF-UC1 and TF-UC2.