An Improved AmbiguityFree Method for Precise GNSS Positioning with Utilizing Single Frequency Receivers The solution of carrier phase ambiguity is essential for precise global navigation satellite system (GNSS) positioning. Methods of searching in the coordinate domain show their advantage over the methods based on ambiguity fixing, for example, immune to cycle slips, far fewer epochs taken for obtaining the precise solution. However, there are still some drawbacks via using the Ambiguity Function Method (AFM), such as low computation efficiency and the existence of a false global optimum. The false global optimum is a situation where the Least Square (LS) criterion achieves minimum in another place than the point of the actual position, which restricts the application of this method to singlefrequency receivers. The numerical search approach derived in this paper is based on the Modified Ambiguity Function Approach (MAFA). It focuses on eliminating the false optimum solution and reducing the computation load by utilizing singlefrequency receivers without solving the ambiguity fixing problem. An improved segmented simulated annealing method is used to decrease the computation load while the Kernel Density Estimator (KDE) method is used to filter out the false optimum candidates. Static experiments were carried out to evaluate the performance of the new approach. It is shown that a precise result can be obtained by handling two epochs of data with z coordinate fixed to the referenced value. Meanwhile, the new approach can achieve a millimeter level of position accuracy after dealing with nineteen epochs of observations data when searching in                                                                                                                                                                  :354,domain. The new approach shows its robustness even if the search region is broad, and the prior position is several meters away from the referenced value.

Unambiguous AcquisitionTracking Technique Based on SubCorrelation Functions for GNSS SineBOC Signals The autocorrelation function (ACF) of the Binary Offset Carrier modulation (BOC) signal for Global Navigation Satellite System (GNSS) has multiple peaks, ambiguity is easily generated during the synchronization of the baseband signal. Some methods have been proposed to remove the ambiguity, but the performance is not suitable for highorder BOC signals or does not maintain narrow correlation characteristics. This paper proposes a subfunction reconstruction synchronization algorithm to solve this problem, of which the key is to design a new local auxiliary code: the local PseudoRandom Noise (PRN) code is divided into several new codes with different delays. The auxiliary code performs a coherent integration operation with the received signal. Then, a correlation function without any positive side peaks is obtained by multiplying the two correlation results to make the acquisitiontracking completely unambiguous. The paper gives a design scheme of navigation signal acquisitiontracking and deduces the theoretical analysis of detection performance. The phase discrimination function is provided. The performance of the method is analyzed from both theoretical and simulation aspects. Compared with the Binary phase shift keyinglike (BPSKLIKE) method, Subcarrier Phase Cancellation (SCPC) method and the Autocorrelation SidePeak Cancellation Technique (ASPeCT) method, the proposed method has the best detection probability for the acquisition, which is 0.5 dBHz better than ASPeCT. For tracking, the proposed method performs best in terms of phasedetection curve, antimultipath performance, and antinoise performance. For highorder BOC signals, the SRSA technique successfully removes the false lock points, and there is only one multipath error envelope, and the code tracking error is almost the same as the ASPeCT method.