| In recent years,with the development of satellite positioning system,Beidou satellite positioning system has covered the whole world,and in the past few years,satellite system has provided users with a large number of positioning services.However,with the development of urbanization,in urban canyons,indoor and underground parking lots and shopping malls,the phenomenon of satellite loss is caused;the quality of satellite positioning services is degraded.Using the abundant LTE wireless signals on the ground for positioning,the construction of LTE(Long Term Evolution,LTE)base stations is quite complete,and indoor cells are installed indoors.LTE signals have strict time synchronization,and each base station has a unique identifier.Therefore,in the actual positioning process,it is first necessary to scan the base station cell to receive and then parse the data to obtain the physical cell ID(Physical cell Identify,PCI)and frame start position.In this paper,when analyzing the received signal to obtain the physical cell ID,how to use the limited frequency point information to obtain as much base station cell information as possible is a key issue in LTE signal positioning.This paper investigates the existing cell search algorithm and the same-frequency signal separation algorithm,and conducts research on the existing problems such as the excessively long analysis time of the same-frequency base station signal.The main work is as follows:First,the cell search algorithm of the current LTE signal is reproduced.Specifically,it includes primary synchronization signal(Primary Synchronization Signal,PSS)detection,secondary synchronization signal(Secondary synchronization signa,SSS)signal detection,and cyclic prefix(Cyclic Prefix,CP)detection.At the same time,the data reception situation is divided.Furthermore,different cell search algorithms are adopted due to different data reception conditions.Secondly,the co-frequency cell under synchronization is studied.Two base station cells will use different PSS sequences or the same PSS sequence to construct PCI.When two co-frequency base stations use the same PSS sequence and use the traditional co-frequency When the base station search algorithm is used,the detection success rate of weak signal cells is not high even when the received power is large.When using the frequency domain receiving model to calculate the channel frequency domain response,the SSS sequence of the weak base station is unknown in advance,so the calculation time is long when solving the channel frequency domain response.Therefore,to solve the problem of long time to solve the frequency domain model,it is proposed to first determine the SSS sequence of weak signal cells and then solve the equation.The number of equations changed from "186" to "124",and the number of solving equations decreased from 168 to 1.Simulations show that under certain conditions,the proposed algorithm can effectively reduce the computation time of the channel frequency domain response when it is used for cell search under the same frequency and PSS.Finally,a multi-channel synchronous receiver based on HackRF is built to verify the same-frequency base station cell and location parsed by the proposed algorithm.However,the positioning part is completed by other members of the project team,and this article does not give a detailed overview.At the same time,the cell search part is tested.The test results show that the proposed algorithm can resolve weak signal cells under certain conditions and can be used for positioning.This solves the problem of insufficient number of cells available for positioning in some environments. |
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