Reliable real-time triple-frequency cycle slip detection and recovery with adaptive detection thresholds

Abstract

Fast and reliable cycle slip detection is a prerequisite for successive ambiguity resolution and precise positioning. For dual-frequency signals, sometimes small cycle slips or particular cycle slips cannot be detected. Benefiting from the triple-frequency signals of global navigation satellite systems, more useful linear combinations can be selected to reduce or avoid the cycle slips otherwise difficult to detect. We propose an improved algorithm with three independent geometry-free combinations to detect and recover potential cycle slips. To improve the reliability of cycle slip detection, adaptive thresholds determined using the posterior total noise of the approximately normal-distributed time-differenced combinations are used, rather than fixed thresholds by a priori information such as the measurement noise and ionosphere residual. After the detection procedure, four different types of detection results are obtained, and the corresponding recovery strategies are applied. In this way, we can reliably detect and recover potential integer cycle slips. To demonstrate the performance of the proposed algorithm, numerical analysis is carried out using observation data of the BeiDou Navigation Satellite System with real cycle slips. Different types of cycle slips are also discussed. The results show that the proposed algorithm can reliably avoid false-acceptance or false-rejection caused by the fixed thresholds, and correctly detect and recover different kinds of integer cycle slips for the experimental data with a 1 s sampling rate.

A Real-Time Cycle Slip Detection and Repair Method Based on Ionospheric Delay Prediction for Undifferenced Triple-Frequency BDS Signals

“…The empirical thresholds, which are used to decide whether a cycle slip occurs, may be too tolerant or too strict for cycle slip detections. Deng et al [23] proposed an algorithm for reliably detecting and repairing cycle slips using three GF triple-frequency combinations and dynamically determined thresholds without considering ionosphere disturbances.…”

“…So, assuming the noises of B1, B2 and B3 are the same will not affect the cycle slip detection. In addition, the code coefficient (1/3,1/3,1/3) was also recommended in references [16] and [23] and it is also suitable for GPS. In the classical algorithms of GF triple-frequency pseudorange minus phase combinations, as mentioned above, it is generally assumed that the ionospheric delay varies smoothly, and the ionospheric delay terms are thus ignored [28].…”

Real-time cycle slip detection and repair for BDS-3 triple-frequency and quad-frequency B1C/B1I/B3I/B2a signals

“…However, this method becomes unreliable due to the reduction of the rounding success rate under the condition of the active ionosphere. Hence, Huang et al (2016), Zangeneh-Nejad et al (2017, , and Deng et al (2019) applied a combination of two GF combinations and one EWL combination to detect cycle slip and employed the classic Least-square Ambiguity Decorrelation Adjustment (LAMBDA) method, which can determine the optimal candidate of cycle slip estimation value to fix cycle slip. Nevertheless, the above-mentioned theories are based on the observation of BDS-2 for cycle slip detection and repair without considering the applicability of BDS-3.…”

An Efficient Cycle-Slip Repair Model With High Success Rate for BDS Triple- Frequency Observations

“…Therefore, it is generally considered more reliable when the deviation is less than 0.3 cycles [25]- [28]. Another strategy is the classic least-squares ambiguity decorrelation adjustment (LAMBDA), which determines the optimal cycle-slip candidates using the floating solutions and a constrained search space [2], [12], [24], [29]- [31]. However, few studies using such an approach have discussed and analyzed whether the optimal solution is actually suitable, how large the threshold is.…”