Real-Time Cycle Slip Detection and Repair Method for BDS-3 Five-Frequency Data

Theoretically, five-frequency observations can form combined observations with longer wavelength, smaller ionospheric delay and smaller noise, which may improve the performance of cycle slip detection and repair. Four geometry-free phase combinations and one geometry-free phase and pseudorange combination are formed to detect and repair the cycle slips in real time. Firstly, the high-quality geometry-free phase combinations of three, four and five frequencies are discussed, then the optimal five-frequency geometry-free phase combinations are selected to detect the cycle slips. Secondly, one geometry-free phase and pseudorange combination which is linearly independent with the above four phase combinations is added to ensure that all the cycle slips can be detected. Thirdly, a real-time cycle slip repair algorithm based on the LAMBDA search method is deduced. The five-frequency real-time cycle slip detection and repair method has been tested by using BDS-3 undifferenced data, even under the condition of active ionospheric and low sampling interval. The results showed that the proposed method is capable of detecting and repairing all the simulated cycle slips on the five carriers in real time.