Carrier Assisted Robust Unambiguous Positioning Technique for Subcarrier Modulated Signals in GNSS

Various subcarrier modulations bring wider Gabor bandwidths and higher-precision ranging and positioning potential to the new generation of Global Navigation Satellite System (GNSS) signals. However, they may also introduce intolerable ambiguity problems for signal tracking, ranging, and positioning. In order to take advantage of high-precision subcarriers in subcarrier modulated signals for unambiguous ranging and positioning, we propose a Carrier Assisted Robust Unambiguous Positioning Technique (CARUPT), which consists of a Carrier Assisted Kalman filter (CA-Kalman) module and an Observation Cycle-slip Detection (OCD) module. The CA-Kalman module utilizes the undifferenced code and subcarrier observations and time-differenced carrier observations derived from two-dimensional tracking to resolve subcarrier ambiguities in the position domain. The OCD module includes a carrier-involved Subcarrier Cycle-slip Detector (SCD) and a high-order difference-based Carrier Cycle-slip Detector (CCD) so as to avoid the impact of subcarrier and carrier cycle slips on the robust resolution of subcarrier ambiguities. In this paper, performances in theory, simulation, and real data experiments comprehensively demonstrate that compared with existing techniques, the CARUPT can resolve subcarrier ambiguities with faster convergence speed, higher accuracy, and robustness, deriving the most reliable unambiguous positioning results.