The analysis on GNSS IPPP time frequency transfer using multiple baselines

Abstract The recovery of integer ambiguities in carrier phase observations enables frequency transfer at the mid-to-low 1 × 10 −17 level when averaging over periods of a few tens of days. In this contribution, we propose a universal method for GNSS Integer Precise Point Positioning (IPPP) frequency transfer that is independent of specific products and software. The algorithmic differences between classical PPP and IPPP are discussed. A continuous IPPP clock offset series is generated via a post-compensation solution, and frequency transfer links based on arbitrary signal combinations and satellite systems are established for multiple baselines. We analyze the performance of IPPP time transfer over ultra-short, medium, and long baselines using 30 days of data. The ultra-short, medium, and long baselines were achieved using Common Clock Difference (CCD), fiber, and IGS modes, respectively. The results show that the optimal IPPP frequency stability, expressed in terms of the Allan deviation, reaches 1.28 × 10 −17 at 76,800 s and 3.84 × 10 −17 at 307,200 s. This represents an improvement of 77.71% at 307,200 s compared to the standard PPP method. The IPPP strategy demonstrates a significant advantage in long-term stability; the stability for long baselines reaches 8.2 × 10 −16 at 76,800 s and 5.9 × 10 −16 at 307,200 s. This method provides a powerful solution for remote frequency comparison.