Doppler Compensated Pseudorange Based Signal-of-Opportunity Positioning Using Iridium Satellite

Signal of opportunity (SOP) positioning is an important positioning technique that enhances the availability, continuity, and reliability of navigation systems. However, due to the non-navigation nature and the partially unknown information of the signals, the acquisition of navigation observables and positioning methods using SOPs are limited. In this article, we consider the joint delay-Doppler estimation of Iridium signals, and further apply the results for SOP receiver positioning. We propose an iterative algorithm for joint delay-Doppler estimation, acquire the pseudorange and Doppler of Iridium signal, and compensate the pseudorange with Doppler for receiver positioning. We discuss the impact of epoch time error on positioning accuracy and compensate for this error to improve the overall accuracy. We evaluate the proposed methods through theory, simulation, and experiments, comparing them with Doppler positioning and conventional pseudorange positioning, and analyze the distribution of positioning error. The experimental results show a significant reduction in the 3-D error of Iridium SOP positioning using the proposed methods, achieving a 46.7% (two-line element) and 65.7% (broadcast orbit) improvement in accuracy.