Research On Indoor Positioning System Based On Wi-Fi Singal Strength And Multi-sensor Data Fusion

Global Positioning System (GPS) has been widely used in our daily life and work, suchas in the navigation, positioning, tracking and mapping areas. Since GPS is mainly realized bysatellites, its positioning performance is usually poor in the indoor environments. With theincreasingly growing tendency of the indoor location-based services applications, convenientand high-precision indoor positioning system has attracted more and more attention.With the gradually improvement of communication infrastructure constructions, wirelesslocal area networks have been widely distributed in shopping malls, houses, schools, officebuildings and other indoor environments. Meanwhile, the rapidly proressed microelectronicstechnology increases functions of portable smart devices such as mobile phones and tabletPCs. They not only have processors with more powerful data processing ability and higheroperating frequency, but also are embedded with accelerator, magnetometer, gyroscope andtemperature sensors. Therefore, it is possible to implement indoor positioning systems basedon smart mobile devices by making use of current mobile terminals and network enviroments,which can help reducing the positioning cost and expanding the application scope effectively.In this thesis, the application background and developing trends of indoor positioningsystem are introduced firstly. The working principle of several common indoor positioningschemes are analyzed and compared, especially the positioning principles of Received SignalStrength Indicator (RSSI) and Dead Reckoning (DR). The RSSI-based positioning belongs toan absolute positioning scheme, but the radio frequency signals are unstable and easy to beinterfered. The DR-based positioning is a relatively positioning technique with lessinterference by outside environments, but it has some inherent shortcomings such as variedstep size and more accumulation error. Thus we propose a DR/RSSI integrated locationalgorithm to achieve indoor positioning system based on the information fusion technology,so that the advantages of the above two positioning techniques can be combined. The detailedreasearch work including the following content: analyzing the RSSI-based ranging model andthe position calculating method, optimizing the heading direction form the orientation sensor,realizing the pedometer via monitoring the Z-axis acceleration data, and updating the onlinestep length and amending the dead reckoning accumulation error during the DR algorithm byusing the absolute positioning of the RSSI method. Based on the Android developmentenvironment, the system modules are designed and the corresponding programs are completed.Finally, The indoor positioning system based on Android platform is implemented and testedfrom the viewpoints of pedometer accuracy, positioning trajectory comparison, thepositioning accuracy, real-time and power consumption performances. The feasibility andeffectiveness of the designed indoor positioning system are successfully verified.