Reference satellite selection method for GNSS high-precision relative positioning

Selecting the optimal reference satellite is an important component of high-precision relat/ve positioning because the reference satellite directly influences the strength of the normal equation. The reference satellite selection methods based on elevation and positional dilution of precision （PDOP） value were compared. Results show that all the above methods cannot select the optimal reference satellite. We introduce condition number of the design matrix in the reference satellite selection method to improve structure of the normal equation, because condition number can indicate the ill condition of the normal equation. The experimental results show that the new method can improve positioning accuracy and reliability in precise relative positioning.

Structure and performance analysis of fusion positioning system with a single 5G station and a single GNSS satellite

NaGlobal vigation Satellite System(GNSS)positioning technology is widely used for its high precision,global,and all-weather service.However,in complex environments such as urban canyons,GNSS performance is often degraded due to signal occlusion and even fails to achieve positioning due to the insufficient visible satellites.Because of the characteristics of large band-width,low latency,and high Base Station(BS)density,the fifth-Generation mobile communication(5G)technology has gradually become a trend for positioning in cities while offering traditional communication service.To supply the communication demands of the User Equipment(UE),only one BS is usually considered to establish a connection with the UE during the BS construction.However,the positioning accuracy with a single BS in urban canyons will be significantly reduced.To further improve the positioning accuracy in such extreme scenarios,this paper proposes a simplified 5G/GNSS fusion positioning system architecture using observations from only a 5G BS and a GNSS satellite.In this system,the GNSS receiver is mounted on the 5G BS,and the measurements provided by the receiver are used to form the differential code and complete the position estimation.The positioning mathematical models of the system based on the original code and differential code are derived.Then,the impacts of the measurements noise and the time synchronization error on the positioning accuracy are analyzed theoretically.Finally,the positioning performance is investigated by a set of simulation experiments.Numerical results show that under the existing 5G measurement noise and 2 m’s code measurement noise,the improvement of the differential code based fusion positioning compared with the 5G-only positioning is more than 32%,which is also about 6%higher than the original code based fusion positioning.Besides,this improvement is not affected by the time synchronization error between the BS and the GNSS satellite.

Indirect-Inversion A lgorithm via Precise Integration for Ill-Conditioned Matrix in Ambiguity Resolution

Global navigation satellite system(GNSS)positioning depends on the correct integer ambiguity resolu-tion(AR).If the double difference equation for solving the float solution remains il-conditioned,often happening due to the environment complexity and the equipment mobility,the corrcct AR is difficult to achieve.Concern-ing the il-conditioned problem,methods of modifying the equation cofficient matrix are widely applied,whose effects are heavily dependent on modifying parameters.Besides,the direct inversion of the il-conditioned coef-ficient matrix can lead to a reduction in the accuracy and stability of the float solution.To solve the problem of il-conditioned matrix inversion and further improve the accuracy,the present study for the first time proves the positive definite symmetry of the coefficient matrix in AR model and employs precise integration method to the indirect inverse of cofficient matrix.AR model for the GNSS positioning and the general resolving strate-gies introduction are briefly introduced.An indirect-inversion algorithm via precise integration for il-conditioned coefficient matrix is proposed.According to the simulations and comparisons,the proposed strategy has higher precision and stability on foat solution,and less dependence on modifying parameters.