A filter method that combines ensemble empirical modal decomposition(EEMD)and wavelet analysis methods was proposed to separate and correct the global navigation satellite system(GNSS)multipath error more effectively....A filter method that combines ensemble empirical modal decomposition(EEMD)and wavelet analysis methods was proposed to separate and correct the global navigation satellite system(GNSS)multipath error more effectively.In this method,the GNSS signal is first decomposed into several intrinsic mode functions(IMFs)and a residual through EEMD.Then,the IMFs and residual are classified into noise terms,mixed terms,and useful terms according to a combined classification criterion.Finally,the mixed term denoised by wavelet and the useful term are reconstructed to obtain the multipath error and thus enable an error correction model to be built.The measurement data provided by the Curtin GNSS Research Center were used for processing and analysis.Results show that the proposed method can separate multipath error from GNSS data to a great extent,thereby effectively addressing the defects of EEMD and wavelet methods on multipath error weakening.The error correction model established with the separated multipath error has a higher accuracy and provides a certain reference value for research on related signal processing.展开更多
Constellations of regional satellite navigation systems are usually constituted of geostationary satellites (GEO) and inclined geostationary satellites (IGSO) for better service availability. Analysis of real data sho...Constellations of regional satellite navigation systems are usually constituted of geostationary satellites (GEO) and inclined geostationary satellites (IGSO) for better service availability. Analysis of real data shows that the pseudorange measurements of these two types of satellites contain significant multipath errors and code noise, and the multipath for GEO is extremely serious, which is harmful to system services. In contrast, multipath error of carrier phase measurements is less than 3 cm, which is smaller than the multipath of pseudorange measurements by two orders of magnitude. Using a particular combination of pseudorange and dual-frequency carrier phase measurements, the pseudorange multipath errors are detected, and their time varying features are analyzed. A real-time multipath correction algorithm is proposed in this paper, which is called CNMC (Code Noise and Multipath Correction). The algorithm decreases the influence of the multipath error and therefore ensures the performance of the system. Data processing experiments show that the multipath error level may be reduced from 0.5 m to 0.15 m by using this algorithm, and 60% of GEO multipath errors and 42% of IGSO multipath errors are successfully corrected with CNMC. Positioning experiments are performed with a constellation of 3 GEO plus 3 IGSO satellites. For dual-frequency users the East-West position accuracy is improved from 1.31 m to 0.94 m by using the CNMC algorithm, the South-North position accuracy is improved from 2.62 m to 2.29 m, and the vertical position accuracy is improved from 4.25 m to 3.05 m. After correcting multipath errors, the three-dimensional position accuracy is improved from 5.16 m to 3.94 m.展开更多
In this paper we propose the derivation of the expressions for the non-coherent Delay Locked Loop (DLL) Discriminator Curve (DC) in the absence and presence of Multipath (MP). Also derived, are the expressions of MP t...In this paper we propose the derivation of the expressions for the non-coherent Delay Locked Loop (DLL) Discriminator Curve (DC) in the absence and presence of Multipath (MP). Also derived, are the expressions of MP tracking errors in non-coherent configuration. The proposed models are valid for all Binary Offset Carrier (BOC) modulated signals in Global Navigation Satellite Systems (GNSS) such as Global Positioning System (GPS) and Future Galileo. The non-coherent configuration is used whenever the phase of the received signal cannot be estimated and thus cannot be demodulated. Therefore, the signal must be treated in a transposed band by the non-coherent DLL. The computer implementations show that the proposed models coincide with the numerical ones.展开更多
基金The National Natural Science Foundation of China(No.41974030)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX17_0150).
文摘A filter method that combines ensemble empirical modal decomposition(EEMD)and wavelet analysis methods was proposed to separate and correct the global navigation satellite system(GNSS)multipath error more effectively.In this method,the GNSS signal is first decomposed into several intrinsic mode functions(IMFs)and a residual through EEMD.Then,the IMFs and residual are classified into noise terms,mixed terms,and useful terms according to a combined classification criterion.Finally,the mixed term denoised by wavelet and the useful term are reconstructed to obtain the multipath error and thus enable an error correction model to be built.The measurement data provided by the Curtin GNSS Research Center were used for processing and analysis.Results show that the proposed method can separate multipath error from GNSS data to a great extent,thereby effectively addressing the defects of EEMD and wavelet methods on multipath error weakening.The error correction model established with the separated multipath error has a higher accuracy and provides a certain reference value for research on related signal processing.
基金supported by the National High Technology Research and Development Program of China (863) (Grant Nos.2009Z12A324 and 2009AA12Z328)the National Natural Science Foundation of China (Grant Nos. 10703011, 11073047 and 11033004)the Science and Technology Commission of Shanghai (Grant No. 06DZ22101)
文摘Constellations of regional satellite navigation systems are usually constituted of geostationary satellites (GEO) and inclined geostationary satellites (IGSO) for better service availability. Analysis of real data shows that the pseudorange measurements of these two types of satellites contain significant multipath errors and code noise, and the multipath for GEO is extremely serious, which is harmful to system services. In contrast, multipath error of carrier phase measurements is less than 3 cm, which is smaller than the multipath of pseudorange measurements by two orders of magnitude. Using a particular combination of pseudorange and dual-frequency carrier phase measurements, the pseudorange multipath errors are detected, and their time varying features are analyzed. A real-time multipath correction algorithm is proposed in this paper, which is called CNMC (Code Noise and Multipath Correction). The algorithm decreases the influence of the multipath error and therefore ensures the performance of the system. Data processing experiments show that the multipath error level may be reduced from 0.5 m to 0.15 m by using this algorithm, and 60% of GEO multipath errors and 42% of IGSO multipath errors are successfully corrected with CNMC. Positioning experiments are performed with a constellation of 3 GEO plus 3 IGSO satellites. For dual-frequency users the East-West position accuracy is improved from 1.31 m to 0.94 m by using the CNMC algorithm, the South-North position accuracy is improved from 2.62 m to 2.29 m, and the vertical position accuracy is improved from 4.25 m to 3.05 m. After correcting multipath errors, the three-dimensional position accuracy is improved from 5.16 m to 3.94 m.
文摘In this paper we propose the derivation of the expressions for the non-coherent Delay Locked Loop (DLL) Discriminator Curve (DC) in the absence and presence of Multipath (MP). Also derived, are the expressions of MP tracking errors in non-coherent configuration. The proposed models are valid for all Binary Offset Carrier (BOC) modulated signals in Global Navigation Satellite Systems (GNSS) such as Global Positioning System (GPS) and Future Galileo. The non-coherent configuration is used whenever the phase of the received signal cannot be estimated and thus cannot be demodulated. Therefore, the signal must be treated in a transposed band by the non-coherent DLL. The computer implementations show that the proposed models coincide with the numerical ones.
