Centimeter-Level Carrier Phase Positioning for Ground-Based Positioning System Without Synchronization

Recent studies have shown that synchronized ground-based positioning systems, such as pseudolites, can achieve decimeter-level to centimeter-level positioning. However, highly precise time synchronization between transmitters is mandatory for existing high-precision positioning algorithms, which greatly limits their applications. Many recent studies focus on relaxing the requirement for time synchronization. In this paper, we propose a Carrier-phase Positioning Algorithm for Systems without Synchronization (CPASS). This algorithm introduces a static reference station as a Clock Bias Monitoring (CBM) station and uses double-difference to eliminate clock biases. Unlike Real Time Kinematic (RTK) in Global Navigation Satellite System (GNSS), CPASS allows the position of the CBM station to be unknown, which simplifies the system requirement. This paper specifically proposes a Batch CPASS (B-CPASS) algorithm for post-processing scenarios and a Sequence CPASS (S-CPASS) algorithm for real-time scenarios. Numerical simulations verify that the two algorithms are able to approach the CRLB, and field experiments show that CPASS can realize centimeter-level carrier phase positioning.