Research On Positioning Algorithm Based On Carrier Phase And DoA Estimation

With the development of society,people's daily life has gradually shifted to being indoor,and the blocking by buildings to satellite signals has greatly increased the difficulty of indoor positioning.Due to the complexity and multi-interference of indoor environments,the research on high precision indoor positioning method in low SNR environments has become a research hotspot of positioning technology.This thesis studies the indoor localization algorithm of 5G cellular network under low SNR environments.Based on the estimation of carrier phase and Direction of Arrival(DoA),this thesis proposes a positioning solution method,which combines the information of propagation distance obtained by carrier phase estimation with the information of DOA estimation,and uses geometric method to solve the position of mobile terminal.Firstly,a Do A estimation method combining the Multiple Signal Classification(MUSIC)algorithm and the Sparse Bayesian Learning(SBL)algorithm is proposed for the signals in low SNR environment in close incoming direction(less than 5°).The algorithm is divided into two stages.In the first stage,a complete set of angles is obtained by iterative MUSIC algorithm based on power spectrum dispersion principle.In the second stage,SBL algorithm was used to screen the obtained complete angle set to obtain the correct Do A estimate.Since the angle set obtained in the first stage is complete,all DoA estimates of incoming waves can be screened out in the second stage,which makes up for the defect that the traditional MUSIC algorithm cannot obtain all DoA estimates of incoming waves.Secondly,the thesis uses a dual-loop phase-locked loop(PLL)structure to perform the carrier phase estimation,and thus acquires the estimates of propagation distance.The inner loop of the PLL is used to estimate the time offset caused by the propagation delay and sampling clock deviation,and the outer loop is used to estimate the frequency offset caused by both the Doppler frequency shift and the crystal frequency offset of the received signal,to recover the correct received carrier phase.In addition,the least square(LS)algorithm is used to estimate the initial downlink signal and the relative full cycle ambiguity of each segment of downlink signal in Time Division Duplexing(TDD)mode.After the obtained carrier phase information is converted into the transmission distance,the terminal position is calculated by combining with the DoA estimates.Finally,the performance of the algorithm is verified by system-level positioning simulation.