Research On GNSS Multipath Detection And Location Method Based On MEDLL

Global navigation satellite system(GNSS)can provide key space-time reference information all day and all-weather,and plays an indispensable role in national security,national economy and various fields of daily life.Due to the propagation characteristics of electromagnetic waves,in challenging scenarios like urban canyons,multipath effects will seriously affect the navigation signal ranging,resulting in degradation of positioning accuracy.How to reduce or eliminate the adverse effects of multipath effect has always been an important topic in the field of satellite navigation signal processing.Therefore,this dissertation focuses on the multipath detection technology in satellite navigation.The specific work is as follows:First,the existing multipath detection technologies are investigated and analyzed.On this basis,starting from the change of the correlation function curve caused by multipath,combined with the multipath estimating delay lock loop(MEDLL)technology,the multipath direct correlation ratio(MDCR)index is designed by using the estimated multipath parameters to evaluate the impact of multipath signals.The effectiveness of this index is verified by simulation under different carrier-to-noise ratios and different multipath conditions.Secondly,the Pearson correlation coefficient is introduced to measure the correlation between the multipath detection index and the pseudorange error caused by multipath.Based on this,the effectiveness of slope asymmetry metric(SAM),carrier-to-noise ratio(CNR),code-minus-carrier-deltarange(CMCD)and the MDCR index proposed in this dissertation is analyzed.And the estimation accuracy of pseudorange error for 4 different multipath detection indexes is evaluated.Finally,using the comprehensive fuzzy evaluation method,the membership function is established to describe the relationship between the 4 multipath detection indexs and pseudorange error caused by multipath,and the comprehensive evaluation weight of satellite ranging information is obtained.The weighted least square algorithm is used to suppress the influence of multipath signals to improve the positioning accuracy of the receiver in challenging scenarios.The simulation results show that the positioning algorithm based on multipath detection can significantly improve the positioning accuracy under static conditions,and the improvement of positioning error under dynamic conditions is relatively limited.