Normalized Bandwidth Control Algorithm for Robust GNSS Adaptive Tracking

Time-varying scenarios challenge the synchronization capability of global navigation satellite system (GNSS) receivers with incoming GNSS signals. Previous research presents the loop-bandwidth control algorithm (LBCA): an adaptive tracking architecture that improves the tracking performance under these scenarios. This technique adapts the loop bandwidth under a fixed, coherent integration time. This paper presents an extension of the LBCA: the normalized bandwidth control algorithm (NBCA). This algorithm adapts not only the loop bandwidth of the tracking loop but also the integration time. The integration time has a significant impact on tracking sensitivity. A long integration time implies more sensitive tracking, whereas a short integration time benefits synchronization in high dynamic scenarios. The NBCA adapts both loop bandwidth and integration time based on the statistics of the discriminator's output. Two NBCAs are implemented in a full lookup table (LUT)-direct-state Kalman filter (DSKF) tracking scheme to adapt the time of response of the delay locked loop (DLL) and the FLL-assisted-PLL (FAP). This research presents a method to efficiently adapt the integration time in an open software interface GNSS hardware receiver. The NBCA-based tracking architecture is evaluated in the GPS L5 signal under a static and dynamic scenario with different carrier-to-noise density ratio (C/N0) levels. The results confirm that the NBCA improves the tracking performance compared to the LBCA with the cost of a slightly increased complexity.