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Sensors 2017, 17(7), 1468; doi:10.3390/s17071468

A Carrier Estimation Method Based on MLE and KF for Weak GNSS Signals

1
School of Aerospace Science and Technology, Xidian University, Xi’an 710126, China
2
School of Information and Communication, Guilin University of Electronic Technology, Guilin 541004, China
*
Author to whom correspondence should be addressed.
Received: 10 April 2017 / Revised: 8 June 2017 / Accepted: 16 June 2017 / Published: 22 June 2017
(This article belongs to the Section Remote Sensors)
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Abstract

Maximum likelihood estimation (MLE) has been researched for some acquisition and tracking applications of global navigation satellite system (GNSS) receivers and shows high performance. However, all current methods are derived and operated based on the sampling data, which results in a large computation burden. This paper proposes a low-complexity MLE carrier tracking loop for weak GNSS signals which processes the coherent integration results instead of the sampling data. First, the cost function of the MLE of signal parameters such as signal amplitude, carrier phase, and Doppler frequency are used to derive a MLE discriminator function. The optimal value of the cost function is searched by an efficient Levenberg–Marquardt (LM) method iteratively. Its performance including Cramér–Rao bound (CRB), dynamic characteristics and computation burden are analyzed by numerical techniques. Second, an adaptive Kalman filter is designed for the MLE discriminator to obtain smooth estimates of carrier phase and frequency. The performance of the proposed loop, in terms of sensitivity, accuracy and bit error rate, is compared with conventional methods by Monte Carlo (MC) simulations both in pedestrian-level and vehicle-level dynamic circumstances. Finally, an optimal loop which combines the proposed method and conventional method is designed to achieve the optimal performance both in weak and strong signal circumstances. View Full-Text
Keywords: GNSS receiver; High sensitivity; MLE; KF GNSS receiver; High sensitivity; MLE; KF
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Zhang, H.; Xu, L.; Yan, B.; Zhang, H.; Luo, L. A Carrier Estimation Method Based on MLE and KF for Weak GNSS Signals. Sensors 2017, 17, 1468.

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