| In recent years,with the development and popularization of GPS and other satellite positioning and navigation systems,navigation technology has provided great convenience for people's lives.However,it is difficult for the navigation system to be used indoors because it is difficult for satellite signals to reach indoors.With the improvement of people's dependence on navigation technology,providing users with excellent positioning services in the indoor environment has become a new hotspot and challenge in the field of positioning and navigation.Currently,mainstream indoor positioning technologies,such as Wi-Fi,Bluetooth,and ultra-wideband,all have problems of one kind or another,and it is difficult to achieve the balance of indoor and outdoor compatibility,positioning performance,and the cost.Therefore,this project proposes an indoor positioning scheme based on pseudolite technology.By deploying pseudolite indoors and transmitting the simulated satellite navigation signals,traditional satellite navigation terminals(such as smart phones and car navigation systems,etc.)can complete positioning and navigation indoors.This article focuses on the two key technologies in this program-satellite navigation signal simulation technology and indoor positioning algorithms.The accurate simulation of satellite navigation signals indoors is a prerequisite for the completion of indoor positioning.Therefore,the real-time simulation technology of satellite navigation signals is first studied in this paper.Specifically,satellite orbit parameters are used to simulate the orbits of satellites,the spatial position of each satellite at the current moment is measured,and then this paper calculates the instantaneous phase and Doppler information of satellite signals by the transmission delay and relative velocity.At last,the satellite signals at the set time and location are simulated by the frequency synthesis technology.By deploying multiple pseudolites in a certain topology in the room,a virtual constellation of navigation satellites can be constructed indoors so that the navigation terminal can still work indoors.On the other hand,transmitting simulated satellite navigation signals through pseudolites indoors will result in a change in the propagation path of the satellite signals which will no longer transmit in a straight line.The change of the propagation path will introduce a large pseudo-range error,making the positioning result(which is referred to as a pseudo-point)by the traditional navigation terminal is output with a large deviation.Therefore,this paper proposes two indoor positioning algorithms to correct the pseudo-points output by the navigation terminal.The first algorithm is called the virtual grid method.The method establishes a mapping table between the pseudo-point and the real positioning result in advance.After the navigation terminal outputs a pseudo-point,it corrects the pseudo-point by looking up the table and finally outputs the correct positioning result.The second algorithm,which is referred to as the second positioning algorithm,uses the pseudo-point and time information output by the navigation terminal to obtain the virtual propagation path length of the pseudolite signal and the current position of the satellite,and then the pseudorange between the pseudolite and the indoor user can be acculated by subtracting the distance between the orbiting satellite and the preset location from the virtual propagation path,so as to obtain a correct positioning result by solving a positioning equation again.This paper verifies the correctness of the navigation signal simulation technology and the two indoor positioning algorithms through simulation.From the positioning performance of satellite navigation terminal and the pseudo-satellite deployment accuracy,the accuracy of the two indoor positioning algorithms is analyzed.It will be a great hornor if this research can provide theoretical and technical support for the study of indoor positioning based on pseudolite technology. |
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