Indoor UWB Positioning Technology Based On Time Reversal

With the continuous development of communication technology and the popularization of mobile devices,people have a higher demand for location services,such as shopping malls and outpatient clinics in hospitals.Although outdoor positioning technologies such as the Global Positioning System(GPS)are very mature,buildings will hinder the transmission of GPS data signals,making it impossible to use in indoor positioning technologies.Therefore,the urgent needs of various fields have prompted the opportunity for rapid development of indoor positioning technology.However,due to the complexity and diversity of the indoor environment,indoor positioning technology still has some limitations.The space-time focusing feature of Time Reversal(TR)can reduce the influence of complex indoor environment on the signal to a certain extent.In addition,Ultra-Wideband(UWB)technology can communicate without the carrier wave,it has features of low transmission power and strong anti-interference.Therefore,this article first analyzes the existing indoor positioning technology,and uses UWB signal as the carrier of TR technology to apply it to indoor positioning technology.Based on this research,it is determined that the research topic of this thesis is the indoor ultra-wideband positioning technology based on time reversal.This thesis mainly discusses from two aspects:First,the indoor Time of Arrival(TOA)positioning technology is usually based on the arrival time of the first direct path among multiple paths.The first direct path cannot be accurately estimated due to the influence of indoor multipath effects.The TOA of the path will affect the positioning accuracy.To solve this problem,this thesis considers UWB signal as a measurement signal,and establishes three reference points,uses TR technology at the reference point and its space-time focusing characteristics will receive the highest peak of the signal at the target point.After the TOA is estimated and the distance is obtained,the traditional positioning algorithm Least Squares(LS)is improved,and different estimated components are given corresponding weights to improve the positioning accuracy.Finally,the simulation verifies the accuracy of the TR technology to estimate TOA and the improvement of the improved algorithm to the accuracy of the positioning system.Second,the previously studied TR technology solves the problem that TOA positioning cannot accurately estimate TOA,but three reference points are set up during positioning,and the higher cost is exchanged for a smaller positioning accuracy improvement.Therefore,this article is in the above research Based on fingerprint positioning technology.Since fingerprints in the current fingerprint positioning technology mainly use Channel State Information(CSI)or Received Signal Strength Indicator(RSSI),using it as fingerprint data recognition will make the constructed database unstable and inconsistent.So this article proposes a distance-based fingerprint positioning technology: create a plane coordinate system in the area and divide the grid.In the offline phase,the position coordinates of each grid point are known,and two known locations are set up outside the area.The reference point of the coordinates,so that the distance from the reference point to the grid point is calculated according to the coordinates as a fingerprint to establish a database.The online phase uses TR technology and TOA to measure the distance from the reference point to the target point as a new fingerprint,which is matched with the fingerprint in the database.According to the similarity,the position coordinates of the target point are obtained.Finally,the simulation verifies the scheme of using distance as fingerprint and TR technology combined with TOA ranging,which reduces the complexity of fingerprint data,improves the robustness and positioning accuracy of the system,and reduces the positioning cost to a certain extent.