Design Of Indoor Tag Positioning System Based On WiFi And Sensors

With the rapid development of wireless information technology, people’s requirements of location based service(LBS) gradually increase. In the outdoor environment, the global positioning system(GPS) can provide accurate location-based services and apply in various fields. However, for the indoor environment, because of the building itself barrier and internal structure such as doors, windows, walls, GPS signal receiving device receives in the indoor environment is very weak, the positioning accuracy is greatly decreased, it is difficult to meet the requirements of precise indoor localization. At present, indoor wireless positioning mainly use Wi Fi, sensor, infrared, ultrasonic, PFID positioning technology.Especially, positioning technology based on Wi Fi due to the wide deployment and the low cost, become the ideal solution for indoor positioning system.In this paper, in order to realize the indoor tag positioning system based on Wi Fi and sensors, we use not only the fingerprint matching technology based on Wi Fi, but also the multiple sensors of the mobile devices to assist the indoor positioning. Test shows that by applying the proposed algorithm, positioning precision is increased.Firstly, this paper introduces some location method based on Wi Fi, summarizes the basic theory and analyzes advantages and disadvantages of the positioning method. Positioning method based model(such as AOA, TOA, TDOA) requires additional hardware equipment and the reconstruction of the existing wireless network. Positioning method based on wireless signal model requires to establish the accurate mathematical model, and positioning method based on fingerprint matching without the need for improvement of the existing network.Therefore, positioning method based on Wi Fi is an ideal indoor positioning method. This paper uses a positioning method based on fingerprint matching of the average of the wireless signal strength repeated collected as position feature.Secondly, this paper uses not only the fingerprint matching technology based on Wi Fi, but also the multiple sensors of the mobile devices to assist the indoor positioning make up for the inadequacy of positioning method based on Wi Fi. Combined with the two technicaladvantages, this method improves the positioning accuracy. According to the information provided by sensors, this method calculates the moving distance and direction of a wireless positioning tag. In the case of the known initial position of the wireless positioning tag, we can get the position of the wireless positioning tag at any time.Finally, this paper implements an indoor tag positioning system based on Wi Fi and sensors. The positioning system is composed of wireless positioning tags and a positioning server. Wireless positioning tags collect periodically the strength of the signal of AP surrounded by them, and sent to the positioning server. The positioning server stores positioning fingerprint information, and executive positioning algorithm, locate wireless positioning tags, and displayed in the Flex end. The experiment results show that the algorithm has high speed and positioning error is about 3.65 meters, so it is very ideal positioning system in indoor environment.