Abstract
In GPS receivers, navigation bit allocation is performed throughout the process of signal tracking and detection. In the process of signal tracking, the locally generated signal must be synchronized with the received signal. The Costas phase-locked loop (PLL) behavior, which is often used for signal synchronization, is characterized by dominant tracking error sources. The resulting phase tracking errors are significant in the presence of weak signals, i.e. signals with the low signal-to-noise ratio (SNR). In order to improve the signal synchronization and enable signal tracking by the receiver, we here proposed the usage of a non-data-aided (NDA) phase estimator. Based on the practical processing of the GPS signals, it is shown that the applied NDA algorithm is more resistant to sudden changes in frequency (phase) of the input signal than the previously considered phase discriminator in the Costas PLL. Also, we have shown that the solution analyzed here exhibits more stable operation in signal tracking for a low SNR.
Highlights
The usage of the Global Positioning System (GPS) is considered in many different applications and under various operating conditions, where necessary, the presence of the continuous GPS information.the operation of a GPS receiver under harsh environmental conditions is limited by a complex nature of radio signal propagation (Djogatovic, Stanojevic, 2012, pp.650-671), which comprises multipath propagation, shadowing and interference
By observing the reception of weak GPS signals with such a developed receiver, we have shown that the carrier tracking solution proposed here improves the detection of weak signals when compared to the previously considered Costas phase-locked loop (PLL) based solution
In this paper, we have proposed the application of an NDA phase estimator that is less sensitive to the dynamic stress in order to avoid a frequent need for re-acquisition while receiving weak GPS signals
Summary
The usage of the Global Positioning System (GPS) is considered in many different applications and under various operating conditions, where necessary, the presence of the continuous GPS information. Since the digital tracking loops are normally used in GPS receivers, when the predetection integration time increases, the receiver dynamics uncertainty in the integration time increases which leads to an unacceptably high phase error Such a phase error can further result in losing signal tracking and/or in the incorrect detection of navigation bits (especially for the tracking of weak signals). By observing the reception of weak GPS signals (with a low SNR) with such a developed receiver, we have shown that the carrier tracking solution proposed here improves the detection of weak signals when compared to the previously considered Costas PLL based solution
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