Performance Evaluation of Vectorized NavIC Receiver Using Improved Dual-Frequency NavIC Measurements

This article presents a modified carrier-aided dual-frequency vectorized tracking (CA-DFVT) algorithm for Navigation with Indian Constellation (NavIC) receiver. In signal blockage and interference scenarios, even the most advanced receiver architecture may fail to provide accurate positioning solutions. Therefore, this article proposes an improved CA-DFVT architecture for NavIC signals. The architecture is based on the vector delay frequency lock loop (VDFLL), wherein precise carrier phase measurements from NavIC <inline-formula> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> and unambiguous code phase measurements from the <inline-formula> <tex-math notation="LaTeX">$L5$ </tex-math></inline-formula> signal are integrated to form new measurements. These measurements are improved by the novel vector tracking (VT) approach introduced in this article. The approach adopts the Savitzky–Golay filtering technique to improve the integrated measurements without deforming the actual measurements. Furthermore, the improved CA-DFVT receiver architecture includes a bidirectional algorithm called the Rauch–Tung–Striebel (RTS). This process involves a forward estimation extended Kalman filter (EKF) and a backward recursion smoother. In addition, this article also introduces VT for CA-DFVT based on an unscented Kalman filter (UKF). Simulations and hardware implementation are carried out to evaluate the effectiveness of the proposed algorithm under conditions of signal blockage and interference. Experiments demonstrate that the improved CA-DFVT can achieve better position accuracy than the single-frequency <inline-formula> <tex-math notation="LaTeX">$L5/S$ </tex-math></inline-formula> VT, CA-DFVT-EKF, and CA-DFVT-UKF approaches. The mean position accuracy of improved CA-DFVT improves by at least 2–6 and 1–2 m for signal blockage and interference conditions, respectively.