| Popis: |
Modern global navigation satellite system (GNSS) receivers need to be robust towards interference to operate under challenging environments, such as out-of-band interference and jamming. A few regional navigation systems, such as navigation with Indian constellation (NavIC), utilize S-band frequency for navigation solutions in addition to L-band. However, utilization of the S-band for navigation solutions provides many challenges to designers of both GNSS navigation signals and signals used by other services. For instance, the NavIC S-band signals are interfered by the out-of-band S-band sources that fall in the unlicensed 2.4 GHz frequency band range. Furthermore, due to interference from various terrestrial communication systems such as wireless fidelity (Wi-Fi), Bluetooth, long-term evolution (LTE), and industrial scientific medical (ISM) band, the positioning performance of the NavIC receiver gets degraded. A possible solution is to implement interference detection and mitigation algorithms that operate directly on the intermediate baseband signal processing level. This paper focuses on the development of a detection and mitigation algorithm for the NavIC S-band signals by means of vector tracking loop (VTL) based software receiver architecture. The detection algorithm performs a hypothesis test to detect interference in the received signal, and the mitigation algorithm minimizes the error propagation in the extended Kalman filter (EKF). Several data were collected and analyzed in the presence of Wi-Fi interference to evaluate the performance of the proposed vector tracking-based algorithm. The root-mean-square error (RMSE) value of the horizontal position for vector tracking-based receiver with and without the proposed algorithm are 4.37 m and 13.92 m, respectively. However, it was 27.11 m for the conventional scalar tracking-based receiver. This shows that the proposed vector-based detection and mitigation algorithms perform better than the conventional tracking approaches. |
