Positioning System Based On ZigBee Wireless Sensor Networks

As a new access to information technology, wireless sensor networks have greater practical value in many regions such as early warning and assistance for disaster, industrial equipment control and management, remote control of risk areas and other remotes. However, in some cases, such as a fire alarm monitoring, locating of pipeline leak point, collected sensor data will have the actual use value only combined with its location information, therefore, node localization have became the basis of wireless sensor networks for some practical applications. In recent years, some positioning methods and systems have been put forward at home and abroad, but every algorithm is usually suitable for a specific type of application scenarios.ZigBee is a short-range wireless communications technology based on IEEE 802.15.4standard, according to its technology features of low rate and low power consumption, ZigBee technology mainly is used for the application with smaller data throughput and more decentralized equipment such as industrial control and instrumentation automation.The node localization algorithms based on distance measurement are mainly studied in this paper. A stepwise weighted positioning algorithm based on distance measurement is designed on the basis of analyzing several typical positioning algorithms, static nodes positioning under natural environment is achieved.Wireless sensor node localization method and the structural characteristics of ZigBee protocol are firstly analyzed in this paper, to determine adopting the ranging method based on RSSI, and then the theoretical model of RSSI ranging is analyzed, by experiment, the impact of unstable factors such as RF antenna orientation and surrounding environment object on the received signal strength value are analyzed. Based on the statistical measurement of actual RSSI value, using least square fitting method, the quantitative relationship of RSSI ranging is established, while the effective range of this RSSI ranging is defined. By analyzing the typical method MLE method, DV-Hop and APIT, considering the impact of node spacing and beacon node distribution on positioning results, a stepwise weighted positioning algorithm based on distance measurement is designed combined with least square method and the centroid method. By MATLAB simulation, impact of beacon node density and ranging errors on the positioning results are analyzed. The simulated positioning error of the algorithm is small with less fluctuation.On this basis, with MC13213 selected as a core chip in the paper, the basic system circuit and peripheral interface circuit of node device is designed, and then using the development software BeeKit and CodeWarrior for node software design, localization algorithm is tested through experiment. After analyzing the results, the algorithm is mostly influenced by the RSSI ranging error, the coarse positioning of node can be achieved.