Assessment of the Multipath Mitigation Effect of Vector Tracking in an Urban Environment

Today, smart mobiles play an important role in our daily life. Most of these devices are equipped with a navigation function based on GNSS positioning. However, these devices may not work accurately in urban environments due to severe multipath interference and non-line of sight (NLOS) reception caused by nearby buildings. A promising approach for reducing the effect of multipath interference and NLOS reception is vector tracking (VT). VT is well-known for its robustness against poor signalto-noise levels. However, its capability against multipath and NLOS has yet to be determined. The new combination of this paper is therefore to evaluate the performance of vector tracking in the presence of multipath and NLOS effects. A vector delay lock loop (VDLL) is used as the vector tracking technique. The noise tuning of the extended Kalman filter (EKF) in vector tracking is a key factor affecting its performance. Therefore, developed an adaptive noise tuning algorithm had been based on the measurement innovation. In order to evaluate vector tracking’s performance, equivalent conventional tracking loops are used as a control. GNSS signals were collected, while walking around in a challenging urban environment subject to multipath interference. The experimental results show that VT generates a more stable code numerical-controlled oscillator (NCO) frequency than CT does. This characteristic could reduce the impact of multipath interference which is reflected in a smaller position error using VT during most of run. To further test capability of VT against signal attenuation, this paper applies a signal cancellation method called direct signal cancellation algorithm to simulate the scenario of signal termination and NLOS reception. According to the simulation, VT provides not only robustness against signal termination but can also detect NLOS reception without any external aiding.