GPS fine time delay estimation based on signal separation estimation theory

The signal multipath effect is one of the main reasons which lead to positioning error in the Global Positioning System (GPS). Although the differential technology can improve the positioning accuracy, the differential GPS system still can´t eliminate the positioning error caused by multipath signals, the reference stations and users being in different geographical environment. In the light of the GPS multipath signal model, this paper presents a GPS time delay estimation algorithm based on signal separation estimation theory. Firstly, Doppler frequency is estimated when the signal delay is unknown. Then, we use the estimated Doppler frequency to get signal delay information with signal separation estimation theory. In addition, we consider the previous estimated results as the initial value and a two-dimension optimization method is implemented in a small range for further improving the estimation accuracy. It can be shown from the simulation results that this method which is able to effectively eliminate the multipath has a better performance compared with the conventional method and narrow correlator spacing algorithm.