The Research On Indoor Decimeter-level Localization Technology With A Single WIFI Access Point

In recent years,with the rapid development of wireless network,and indoor localization technology based on commercial WIFI devices has become a research hotspot in the field of mobile computing.In Light-of-Sight(LOS)/Non-Sight-of-Sight(NLOS),WIFI-based indoor location systems exhibit different properties.However,most of the WIFI-based indoor positioning systems are currently located under the known priori conditions of LOS/NLOS.In addition,the indoor positioning systems are based on multiple Access Points(Aps),but the actual application scenarios usually have only one AP.In view of the defects of the positioning system,we present a propagation environment identification system,Asor(Area Sensor,Asor)and an Asor-based localization system(Aloc),which can achieve high-precision indoor moving target positioning with a single AP.Firstly,based on the Fresnel Zone(FZ)model,we analyze the characteristics of Channel State Information(CSI)and establish two mathematical models,namely,CSI Power Absolute value(CPA),and Diversification of CSI Power Absolute values(DCPA).Secondly,we propose two propagation environment LOS/NLOS detectors,DCPA detector and CPA detector based on DCPA and CPA mathematical models respectively.However,the DCPA detector is only suitable for dynamic scenes,and the CPA detector works well in static scenes.To solve this problem,we make use of Hidden Markov Model(HMM)to propose a new adaptive propagation environment detection system,Asor,which can realize real-time and accurate LOS/NLOS identification in dynamic/static scenes.A large number of experiments are conducted to evaluate the performance of Asor,and the experimental results show that the median detection rates of LOS / NLOS are 93.44% and 86.56% in the static scene,and those of LOS / NLOS are 87.19% and 86.56% in the mobile scene.Finally,we present an indoor positioning system,Aloc,based on multipath frequency phase noise elimination,which realizes the indoor moving target positioning with a single AP.Aloc is consist of two parts: Time Of Flight(TOF)estimation and Angle Of Arrival(AOA)estimation.Furthermore,the performance evaluation of Aloc from multiple perspectives is carried out.The experimental results show that Aloc achieves high precision positioning in LOS/NLOS,especially in LOS,the median positioning error is less than 1m.