| Location service has become a major infrastructure for national security,economic development and people's livelihood.High-accuracy indoor and outdoor location information is urgently needed in areas such as public safety,emergency rescue,smart city and so on.The existing wireless network positioning technologies mainly include wide area network positioning technologies(such as 2G/3G/4G mobile communication networks and broadcast networks)and local area network positioning technologies(such as Wireless-Fidelity(Wi-Fi),Bluetooth,Ultra Wideband(UWB),etc.),but they can not meet the requirements of wide coverage and high-accuracy positioning simultaneously.The communication and navigation integrated system researched is based on multiplexing the frequency resources and base stations of the mobile communication network,which does not interfere with the original communication signals.Finally,it can meet the requirements of indoor and outdoor seamless positioning with wide coverage,high precision,high robust and low cost.Due to the high complexity of the communication and navigation integrated system and the application environment,the integrated signal design and the navigation baseband processing are full of challenges.This dissertation deeply researches the key technical problems in the communication and navigation integrated system,such as the optimal anti-multiple-access interference code design under the homologous clock,the high-accuracy frequency acquisition under the constraints of computing resources,and the robust tracking loop under the instantaneous strong fluctuation of Signal to Noise Ratio(SNR).Theoretical researches and engineering practices have been carried out,and the main innovative achievements of this dissertation are as follows:1.Aiming at the problem of the positioning signal under the same clock constraint in the integrated system,the correlation properties of Pseudo Random Noise(PRN)and Truncated PRN(TPRN)are analyzed,and then a mixed code(PRN+TPRN)signal structure with optimal anti-multiple access performance is designed.Based on the analysis of the influence of TPRN on the signal acquisition,a novel acquisition algorithm named Predicting Reference Code Phase-Continuous Detection Acquisition(PRCP-CDA)is proposed.The pre-processing of the reference code phase improves the acquisition detection probability.The simulation and experimental results show that the proposed acquisition algoritlun can effectively estimate the phase of the mixed code,which provides guarantee for the subsequent tracking processing of the positioning receiver.2.Aiming at the problem of fine frequency acquisition with high-accuracy estimation and low computational complexity,a estimation method named Fast Orthogonal Search(FOS)is introduced,and the mapping relations between the candidate function and residual carrier frequency are established.To reduce the computational complexity,a fine frequency estimation algorithm based on Parallel Fast Orthogonal Search(PFOS)is proposed,which can reduce the computational load by 57.43%compared with FOS-based frequency estimation.Compared with the fine frequency estimation algorithm based on Fast Fourier Transform(FFT),the PFOS can achieve higher frequency resolution with lower computational complexity.The simulation and experimental results show that the PFOS algorithm can improve the frequency estimation accuracy,accelerate the convergence speed of the carrier loop,and reduce the Time to First Fix(TTFF)of the existing positioning receivers by about 5%.3.Aiming at the problem of the stable carrier tracking under the sudden change of the received signal amplitude,the influence of mixed code on the carrier tracking loop measurement is firstly analyzed,the mathematical models based on Kalman Filter(KF)-based Frequency Locked Loop(FLL)and Phase Locked Loop(PLL)are built.A novel canier tracking algorithm named the KF-based second-order FLL-assisted third-order PLL with the fuzzy control is proposed by introducing the fuzzy control theory.The carrier tracking loop bandwidth and the equivalent filter coefficient are automatically adjusted.The simulation and experimental results show that the thermal noise performance and dynamic performance of the carrier tracking loop are improved,and then the tracking accuracy,convergence and robustness of the carrier tracking loop are improved.Compared with the PLL and the second-order FLL-assisted third-order PLL,the proposed carrier algorithm improves the anti-signal amplitude sudden change capability by 5dB,and has higher the carrier phase estimation accuracy at high SNR.4.Aiming at the problem that the high-accuracy pseudorange can not be acquired under the sudden change of the receiving signal amplitude,the snapshot method is used to store the received signal,and the relatively independent storage data are analyzed by multiple playback.The snapshot method can reduce the influence of the sudden change of the signal amplitude.The mathematical analysis of the influence of RF front-end bandwidth on pseudo-range measurement is carried out.A snapshot-based pseudo-range measurement method based on Taylor expansion is proposed.The simulation and experimental results show that the proposed method reduces the sensitivity of the code loop to the sudden change of the receiving signal amplitude,and improves the pseudorange measurement accuracy.Compared with the infinite bandwidth-based pseudorange measurement method,the proposed method can improve the real pseudorange estimation accuracy by more than 9.7%. |
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