Research On GNSS Measurement And Positioning Technology Based On Pseudo Satellite

The global navigation satellite system’s accuracy and integrity is closely related to the number of visible satellites and geometric distribution,lessnumber of visible satellitesandgeometric distributionwould seriously reduce the positioning accuracy.Pseudo satellite technology is an effective way to improve the number of visible satellites and improve geometric distribution.It is of great value to improve the service performance of the satellite navigation system under special conditions.This paper study GNSS measurement and positioning technology of pseudo satellite,mainly includes the following four aspects:1)There is no relative motion between the stationary receiver and the pseudo satellite augmentation system.The digital processing may lead to decimeter ranging deviation,but currently there is no literature on this phenomenon.To solve this problem,this paper deduced expression oflimited time delay estimationusing the digital processing scheme,and pointed out the influence of limited resolution time delay estimation of navigation receivers deviation,finally given the optimization criterion of receiver frequency planningto improve the resolution of time delay estimation for the target.The simulation results show that navigation receivers deviation caused by the time delay estimation is less than 1cm when the frequency planning is optimized.2)The difference of the signal level of the traditional satellite navigation system is usually less than 20 dB,and the isolation of the code can ensure the weak signal reception is not affected by the strong signal.But for the pseudo satellite signal system with continuous enhancement system,inevitably exist near-far effect,the isolation of the code at this time has been unable to guarantee the normal reception of weak signals,reducing receiver acquisition probability and tracking accuracy.At present,the subspace projection algorithm is most concentrated in the research of near-far effect suppression,however,its large matrix operation is the obstacle for the realization of real-time application.To solve thecomputational problems of subspace projection matrix,this paper proposes a subspace projection suppression technology based on inner product,on the foundation of keeping the near-far effect suppression,the original multidimensional matrix operation is improved into one dimension vector operation,and without strong signal carrier phase parameter estimation.The analysis results show that when the signal strength differs by 30 dB,the use of the algorithm and did not take the near-far effect suppression technology can be compared,the acquisition probability is increased by about 70%,the carrier phase tracking accuracy is improved by 3 times,delay locked loop tracking accuracy is 13.6%.3)Because of the difference between the observation error of the satellite and the navigation satellite,the traditional receiver autonomous integrity monitoring algorithm cannot be applied to the constellation and heterogeneous of pseudo satellite,to solve this problem,a new method of the integrity of pseudo satellite based on the weighted parity vector is proposed,the parity vector is normalized weighted,significantly reduced the level of error protection,improve fault detection probability,enhance the availability and integrity of performance.The simulation results show that the use of pseudo satellite and navigation satellitejoint positioning,HPL isbetween 73 meters and 81 meters,smaller than the traditional method of HPL 84.6meters and 97 meters,improve the availability of the RAIM algorithm to a certain extent.The fault detection probability of weighted parity vector RAIM algorithm is 10% higher than that of conventional RAIM algorithm when the fault is between 25 meters and 40 meters.4)The traditional pseudo satellite is mainly used to solve the problem of integrity of the navigation system based on the configuration of the satellite,but it can not directly solve the problem of high precision positioning.According to submeter accuracy ofthe pseudo satellite enhancement system,the positioning technique based on eliminating the pseudosatellite range difference is studied.The simulation analysis shows that the standard deviation of the positioning accuracy can be reduced from 1.685 m to 0.657 m based on the 2 pseudo satellite differential positioning.Aiming at the requirement of the high precision positioning of the pseudo satellite,the relative positioning technology of the pseudo satellite carrier phase is studied,and the fast rate of carrier phase ambiguity resolution is improved by using the known baseline constraint.The simulation results show that the success rate of the fuzzy degree solution can be increased from 75.3% to 89%.Under the condition of 3km baseline length,the peak errorof the carrier phase difference positioning less than 3cm.