Research Of WLAN-Based Positioning And Tracking Technology

With the widespread of wireless networks, positioning and tracking services become attractive and show great energy in many applications, such as emergency, logistics distribution, production management and navigation. The international standards of RTLS and the growing up of the Internet of Things have promoted the development and application of positioning and tracking technology.However, the existing positioning technique cannot fulfill the growing requirements of pervasive computing applications in practical applications, such as low cost and portability, which limits the popularization of location based services (LBS). With the help of the existing resources of WLAN, the positioning technique based on WLAN and location fingerprinting schemes can be implemented by using of wireless routers. Besides, it can work effectively in a wide range with low cost. Thus, positioning technique based on WLAN and location fingerprinting schemes has become a hot research topic in the field of location awareness.in recent years.Aiming at the problems and requirements in the accuracy, speed, energy consumption and map management of the existing location technique, this thesis proposed the corresponding solutions using the theory of NNSS weight matching, area zoning and GIS. Main works and innovations are as follows:(1) With the location fingerprints measured in a practical WLAN, the thesis analyzes some characteristics of radio signal propagation in indoor environments from the viewpoint of location, and makes a conclusion of how to construct a database of location fingerprints and how to measure the signal strength.The factors, such as the space between sample points, the numbers of the access points and the interference of the circumstance, are of great importance to position estimate based on WLAN and location fingerprints. However, until now, there is not a general strategy on how to determine these factors, they are mostly determined by experience. This thesis investigated the relationship between these factors and the location errors, which may be helpful for the location estimation algorithm and system, and the database of location fingerprints.(2) Based on the position weighing algorithm of LANDMARC system, the NNSS-AVG method in RADAR system is improved in this thesis.Due to the interference from noises of complex indoor environments, location fingerprints data are always with great uncertainty, thus how to improve the positioning accuracy is one of the important research focuses. In this thesis, NNSS-AVG algorithm is improved. The nearest neighbors are weighted with different values, which represent the different contribution to the positioning results. Besides, an adaptive method of matching the access points is proposed in this thesis.(3) An area zoning and decision method for WLAN based positioning technique is proposed.Efficiency and practicality of the location system are strongly related to the time cost in locating computation process. Thus, a low computational cost method, area zoning and decision method is proposed, which limit the computational region in the certain area. Since the energy consumption of mobile devices can be decreased by the reducing computation, the positioning system can to be transplanted to mobile devices.(4) Based on mobile station assisted positioning technique, active WiFi positioning tags are designed in this thesis, and the noise immunity, stability and energy consumption of the tag are investigated.(5) Using GIS and database technique, the platform provides users a series of serives based on location, such as real-time positioning, historical pathway replaying, limited region entering, safe region guarding and optimal path analysis for rescue and intercept.This thesis studys the positioning technique based on WLAN and position fingerprints, designs the active WiFi positioning tag based on mobile station assisted positioning technique, develops a management platform of positioning and tracking system, and provides users a series of serives based on location.