Indoor Positioning System Based On WIFI-RTT

With the continuous development of urbanization,people's demand for indoor location-based services in modern life is increasing.However,indoor location is faced with the challenges of complex indoor environment scene,many interferences,rapid change of personnel position and so on,which makes it a research hotspot to obtain high-precision location results in complex indoor environment.In the 2016 version of 802.11 mc protocol,a new type of Wi Fi-RTT(round trip time)ranging technology which can be used for indoor positioning is proposed.It has the characteristics of low deployment cost and high precision,which is a hot research direction of indoor positioning research in recent years.In order to improve the accuracy of location system based on wifi-rtt ranging technology,the system first optimizes the FTM(flight time measurement)protocol at the bottom of wifi-rtt.In FTM ranging experiment,a large number of FTM measurements are collected at different distances to estimate the specific distribution information of FTM ranging,different statistical estimation formulas are used to restore the real distance,and the statistical formula with the smallest error is selected as the distance estimation formula,so as to optimize the results of FTM ranging.The location coordinate calculation of the system needs to consider the conditions that wifi-rtt error does not meet the Gauss distribution and the distribution of Wi Fi base stations in reality.The coordinate calculation based on Bayesian formula can well meet the characteristics of wifi-rtt technology.Through the contrast experiment and analysis,the location algorithm based on Bayes formula is better than MLE algorithm and gradient descent algorithm.Finally,the map service part of indoor location service can be completed by using GIS(Geographic Information System).In order to reduce the pressure of map data loading on the system,we can segment the background map and build tile map cache.At the same time,the system analyzes the data flow in the system of map transmission and positioning data transmission,and further optimizes the positioning response time of the system by means of stage loading and full duplex communication.