GPS Signal Parameter Estimation And Positioning Methods In Complicated Environment

This dissertation is going to study the GPS signal parameter estimation and positioning methodologies. We have fulfilled the studies of the pseudo-code delay estimation, the anti-multipath technique of the GPS signals and the GPS positioning fusion method. The pseudo-range delay estimation with the assistance of the carrier signal of the GPS is proposed. The making use of smart antenna to cope with multipath effect is investigated and the GPS/DR combination and the data fusion algorithm have been studied. GPS/MM technique providing better positioning performances has shown. GPS/UWB combined postioning system is discussed as well. The major works of this thesis are as follows:The effect of the Doppler frequency precision measurement of the pseudo-code delay in high dynamic circumstance is studied. The usage of the extended-Kalman-filter (EKF) method in estimation of the carrier phase and the receiving signal frequency are being investigated. Also making use of the carrier-assisted technology, we can calibrate the pseudo-code delay loop through carrier-phase deviations. Such that we can obtain the accurate pseudo-code delay estimation and improve the dynamic performance of the pseudocode delay loop.After careful analysis of the characteristics of the multipath signals, for those measurement pseudo-range errors and carrier-phase tracking errors which introduced by the mutlipath effect have a thorough study. The reduction of multipath effect by introduction of anti-multipath smart antenna is discussed. In a complicated environment, the performance of GPS is dependidng on the interference of the environment. A study on the anti-multipath effect is carried out and the smart antenna is used to tackle this problem and the anti-RF interference technologies are considered in this section. Besides, the structure of the vehicle integrated system with GPS/DR is given and the mathematical model of this system is established. Errors caused by the DR give poor signal performances. We proposed a data fusion algorithm for this integrated navigation system and the algorithm has improved the accuracy of the GPS and this is tested by actual vehicle data.The GPS and GLONASS receivers have quite similarity structures. With the maturity of the GPS technology and products, we would like to investigate the possibility of using GPS technology to develop the GLONASS receivers. The GLONASS C/A code receiver design is based on the GPS chip sets. Also the algorithm for the combined GLONASS/GPS including the combined positioning model and its calculating method are studied. The methods for calculating the GDOP, the satellite selection and ionospheric delay compensation are also discussed.Base on the complicated traffic environment of Hong Kong, the electronic map information is used to improve the accuracy of the positioning information of the vehicle obtained from the GPS signals. Also a modified map matching algorithm is introduced. The advantage of this method is that no additional hardwares or sensors are needed and the improvement of the positioning accuracy is based on the software and the proposed algorithm. Finally, we would like to investigate the navigation system reliability and robustness with the help of the GPS and UWB technologies.