Performance of the vector tracking loop assisted by desired trajectory during short signal outages

This paper presents a vector tracking loop (VTL)-based carrier tracking algorithm assisted by desired trajectory of vehicles during short signal outages. The VTL-based carrier tracking algorithm is first derived. The desired trajectory of vehicles is then introduced to assist the VTL, ensuring that the carrier numerically controlled oscillator (NCO) keeps working during signal outages. The performance improvement of the proposed algorithm is verified in two different scenarios. It is shown that the VTL assisted by desired trajectory has higher frequency precision than that with no assistance. Besides, the proposed method can maintain the navigation solving and restrain the frequency error from increasing.

I. Introduction

In traditional Global Positioning System (GPS) receivers [1], each channel maintains an independent tracking loop, called the scalar tracking loop (STL). The pseudorange and pseudorange-rate are measured in each channel independently, and no information is fed back to the tracking loop from the navigation solver. Unlike STL, the vector tracking loop (VTL) combines all the tracking channels, estimating optimally the receiver's position, velocity and time (PVT) solution via an Extended Kalman Filter (EKF) [2]. The PVT solution and the satellite ephemeris are then used to predict the pseudorange and pseudorange-rate at the next time epoch, allowing all channels being controlled simultaneously. So, the VTL implements a deep coupling between baseband signal processing and navigation solution computation [3], [4]. Due to the inherent relation between the received signal and the receiver's PVT, the VTL can improve tracking performance in high dynamic circumstances [5], [6].