Research On Acquisition And Multipth Mitigation For Co-Band Positioning System

With the rapid development of the mobile Internet,location services have become a competitive hot spot in emerging industries worldwide.Mobile communication networks have the characteristics of large bandwidth,good robustness,and wide coverage.They have unique advantages in the field of navigation and positioning.The integration of navigation and communication has become a research hotspot in navigation and positioning technology.After years of development,the co-band communication and navigation fusion system proposed by Beijing University of Posts and Telecommunications has formed a systematic solution for seamless indoor and outdoor positioning.However,with the development of wireless networks and the increasing demand for location services,the co-band communication and navigation fusion system Still facing the challenge of further improving the positioning service capabilities.This paper focuses on the high-sensitivity high-precision fast acquisition with limited resources and the high-precision positioning under multipath and non-line-of-sight environment in co-band communication and navigation fusion system.Key technology research,theoretical innovation and engineering practice corresponding to these problems are carried out in this paper.1?Aiming at the high-sensitivity high-precision acquisition problem,a Partial Matched Filter-Fast Fourier Transformation(PMF-FFT)acquisition technology combined with Block Accumulation(BA)and Frequency Compensation(FC),search space reduction strategy based on prior information of Pseudo Random Noise(PRN)code and DD-MAX/TC-CACFAR detection method is proposed based on two stages of acquisition procedure.This dissertation also conducts a detailed analysis of the detection methods under noise and multipath interference,and proposes the evaluation index of the acquisition time based on the above methods.The innovations and effects of each method are as follows:1)PMF-FC-BA-FFT method uses block accumulation and frequency compensation technology to achieve a comprehensive improvement of acquisition sensitivity and frequency acquisition accuracy under limited resources.Frequency compensation technology combined with Double Dwell(DD)technology can effectively improve the frequency acquisition accuracy,while also avoiding the power attenuation caused by grooming filter characteristics of block accumulation and excessive consumption of computing resources.The block accumulation technology effectively improves the signal-to-noise ratio(SNR)while avoiding the significant reduction of the FFT frequency search space caused by coherent integration(CI).Compared with Zero Padding FFT(FFT-ZP)acquisition based on coherent integration,the proposed method can achieve high-sensitivity high-precision acquisition with less computional resources while ensuring that the frequency capture range is not reduced.2)The search space reduction method based on prior information of PRN code adds the PRN code number information of the adjacent source in the navigation message so the receiver can obtain the PRN code number of the adjacent source after the message demodulation of one signal has been completed.Based on the real-time code phase information of acquired or tracked signal and combined with the receiver's receivable signal range and the distance of the source,the receiver can obtain the phase prior information of the PRN code.The receiver can greatly reduce the size of the acquisition search space,thereby effectively reducing the acquisition time and realizing fast acquisition3)DD-MAX/TC-CACFAR detection technology combine double dwell technology,Maximum/Threshold Crossing(MAX/TC)technology and Cell Averaging Constant False Alarm Rate(CACFAR)technology to effectively improve the detection performance,and enables acquisition to maintain good and stable detection in the presence of interference noise fluctuations.The performance of this detection method under noise and multipath interference is deduced and analyzed in detail.Analysis and simulation results show that compared with the existing detection methods,this method has higher and more stable detection performance.4)Aiming at the evaluation problem of acquisition time consumption,this paper gives the acquisition time evaluation parameter based on Markov chain and signal flow graph technology and combined with the detection method and the search space reduction method,which is the mean acquisition time(Mean Acquisition Time,MAT).The impact of each parameter on acquisition time is analyzed in detail.The DD-MAX/TC-CACFAR method effectively reduces the false alarm penalty time(FAPT)by reducing and stabilizing the false alarm rate.Analysis and simulation results show that the combination of the DD-MAX/TC-CACFAR detection and decision method and the search space reduction method greatly reduces the acquisition time.2?Aiming at the problem of reduced positioning accuracy of co-band communication and navigation fusion system in multipath and non-line-of-sight(NLOS)environments,a method named Direct Path Identification-Sequential Maximum Likelihood(DPI-SML)is proposed.This method comprehensively considers the common influence of the signals corresponding to multiple paths on the correlation peak when estimating the multipath parameters,so that the initialization parameters of the iteration has a higher accuracy.Generalized likelihood ratio test is used to control the iteration which can effectively control the number of iterations while achieving high-precision multipath estimation.Based on the definition of the complete NLOS(CNLOS)and the incomplete NLOS(ICNLOS),the ICNLOS direct path identification method based on the delay selection ratio criterion is proposed,which can achieve accurate ranging result in ICNLOS environment.The simulation and measurement results based on typical fifth generation mobile communication technology(5G)LOS and NLOS channel model show that,compared with the existing typical non-parametric Strobe method and parameterized Multipath Estimation Delay Locked Loop(MEDLL)method,the DPI-SML method can achieve with fewer iterations and high-precision positioning in multipath NLOS environments...