Enhancing BDS RT-PPP Time Transfer and Synchronization Method With Inconsistent Pseudorange Biases Modeling

Precise time and frequency synchronization measurements are critical for many advanced applications, including mobile communications, the Internet of Things (IoT), and low Earth orbit (LEO) satellite internet. Real-time precise point positioning (RT-PPP) technology has become one of the dominant methods for real-time high-precision time–frequency transfer and synchronization. This study proposes an enhanced BDS RT-PPP time transfer and synchronization method utilizing bias modeling and develops a high-precision RT-PPP time synchronization terminal. After correcting inconsistent pseudorange biases, the RT-PPP time transfer precision reaches 0.19 ns for GPS and 0.16 ns for BDS, while the frequency stability over an averaging time of 1.5 x 10⁴ s reaches 4.01 x 10^-15. Compared with the conventional RT-PPP solution, the proposed bias-corrected method improves the time and frequency transfer performance of both GPS and BDS by approximately 30%. Furthermore, after clock information processing based on BDS RT-PPP, real-time pulse-per-second (PPS) physical signal synchronization with an average precision of 0.20 ns is achieved, and average frequency stability reaches 2.56 x 10^-15 at 1 day averaging time in two time links. When combined with a low-cost oven-controlled crystal oscillator (OCXO), the proposed system demonstrates frequency stability comparable to that of commercial hydrogen masers at 1 day averaging time, providing a portable solution for modern time and frequency stability measurements.