Impact Assessment of the Asynchronous Clocks Between Reference and User Receivers in Differential Pseudolite Navigation System

Compared with the Global Navigation Satellite System (GNSS), the asynchronous pseudolite (PL) navigation system does not provide corrections for the frequency deviation between PL signals. To realize precise positioning, a reference receiver is utilized to reduce the effect of frequency deviation between PLs via the differential method using carrier phase measurements. However, there exists time deviation between the user and reference receivers due to their asynchronous clocks. With this time deviation, the effect of frequency deviation between PLs cannot be removed thoroughly. Theoretical derivation and experimental verification indicate that the residual error in double difference of carrier phase measurements is proportional to the frequency deviation between PLs and the time deviation between receivers. To solve this problem, two approaches, refer to hardware and software methods, are proposed, which are experimentally proven to be feasible.