Research On Algorithm Of BDS Precision In Complex Landform

High-precision geospatial data is the core technology of BDS widely used in e-government,e-commerce,digital city and digital earth.In complex geomorphic environments such as urban canyons,BDS signal is susceptible to multipath interference,which affects the positioning accuracy of the receiver.The BDS positioning errors mainly include satellite-generated errors,satellite signal transmission process errors,and BDS receiver-generated errors.Ephemeris errors,clock errors,ionospheric errors,tropospheric errors,etc.can be effectively eliminated by existing models.However,existing techniques cannot completely eliminate multipath errors caused by complex geomorphological environments.At present,the multi-path interference suppression algorithm mainly has good suppression effect on long delay multipath interference,while the suppression effect of short delay multipath signal is weak.This paper mainly focuses on the short delay multipath interference suppression algorithm,mainly including the following two parts:(1)Multipath interference suppression algorithm based on blind equalizer.In order to effectively suppress multipath errors,improve the continuous tracking capability of the receiver and meet the design requirements of high-accuracy receivers,the paper introduces a blind equalization algorithm in the tracking loop.A blind equalizer is used to compensate for the distortion of the received signal caused by multipath interference and restore the original signal as much as possible.In harsh environments,serious multi-path interference can cause large multi-path errors.Using the decision feedback blind equalization algorithm to restore the original signal sequence,so that reduces the influence of multipath interference on the positioning accuracy.(2)In order to further improve the performance of the BDS receiver in suppressing multipath interference,the blind equalization technique is combined with vector tracking as an entry point to improve receiver positioning accuracy.Because the vector tracking can combine solve through each receiving channel,the code phase,carrier frequency and other information be shared to improve the anti-interference ability of the vector tracking loop.When the channel distortion is serious,the CMA-DFE algorithm is used to compensate for the distortion characteristics of the channel.If use the fixed-length,the algorithm will affect the global convergence,so the step sizes of the CMA-DFE algorithm need change.And the error signal introduced by the CMA-DFE algorithm is provided by the feedback loop of the vector tracking loop.The vector tracking loop provides feedback error of the CMA-DFE algorithm by combining the observation information of different channel signals and the feedback information of the navigation solution,and adjust the iteration step length to reduce the misjudgment of the feedback equalizer,thereby improving the convergence speed of the algorithm and improving the positioning accuracy of the GNSS receiver.The experimental simulation results show that the proposed multipath interference suppression algorithm based on blind equalizer effectively improves the ability of suppress multipath interference,and has high positioning accuracy and robustness.