| With the continuous evolution of mobile communication technology and the vigorous development of the Internet of Things,the application of 5G mobile communication networks is gradually expanding.With the intelligence of the 5G mobile communication system,positioning has become one of the important characteristics of 5G,and the demand for high-reliability and high-precision indoor positioning technology in 5G is increasing.Currently,due to the impact of environmental noise,signal multipath propagation,imperfect time synchronization between terminal users and positioning base stations,and other issues,the 5G system still cannot provide high-reliability and high-precision indoor positioning functionality.Based on the uplink detection reference signal,the thesis makes research on the key technologies of 5G mobile communication positioning,focusing on the high-precision time delay estimation algorithms and robust joint time synchronization and positioning algorithms in indoor multipath environments.The main research work of this thesis is as follows:Firstly,the existing time delay estimation methods are summarized.In traditional TOA estimation methods,the MUSIC algorithm is a relatively optimal algorithm with advantages such as super-resolution,low computational complexity and robustness.However,the disadvantage is not to be ignored,since it is difficult to achieve accurate time delay estimation in multipath environments.In response to the problem that traditional time delay estimation algorithms are difficult to distinguish weak first-path signal in multipath signals,a WRELAX algorithm based on channel response is proposed.WRELAX is a solution to complex nonlinear least squares problem based on the relaxation idea.By sequentially estimating the arrival time delay and amplitude attenuation of each multipath signal,the influence of environmental noise and multipath interference is reduced.Compared with the traditional spatial smoothing MUSIC algorithm,WRELAX has higher delay estimation accuracy and robustness in multipath environments.Time synchronization and positioning are two key technologies for 5G indoor positioning.In traditional positioning technologies,time synchronization and positioning are usually treated as two independent stages.However,from the perspective of signal processing,the two are closely related,and adopting a joint estimation method can improve the performance of the positioning network at the same time reduce the consumption of additional hardware and communication resources.Based on the TOA ranging positioning model with clock offset,a joint time synchronization and positioning algorithm based on the alternating iterative maximum likelihood idea is proposed for static terminal users,and the initial value of the algorithm is obtained by solving the MVIE problem.For moving terminals,a joint time synchronization and positioning algorithm based on EKF is proposed.The simulation results show that the alternating iteration algorithm can achieve a positioning accuracy of 2m and a synchronization accuracy of 4ns;the EKF joint estimation algorithm utilizes the constraint relationship between each motion frame,and therefore has better joint estimation performance,with positioning accuracy within 1m and synchronization accuracy within 3ns. |
