| Wireless sensor network (WSN) has received increasing attention in recent years, which has wide applications in the aspects of industry, military, and environment. As one of the key enabling technologies and research hotspots, researchers have provided many effective location protocols and implemented some localization systems.Forcing on the indoor location, this paper will analyze typical location protocols and localization systems, and implement an indoor localization system with small error, and provide some solutions to improve the performance. The main contents of this thesis can be listed as follows:A localization system for the indoor location is provided. This localization system based on time difference of arrival (TDOA) is implemented with the WSN nodes with ultrasonic transceivers and TinyOS which is the most widely used embedded system for WSN. The localization error is reduced with improving the range accuracy of the nodes. The sources of errors are analyzed.In order to solve localization error problem caused by wrong match of the two wireless signals from the different beacon nodes, the mechanisms for ultrasonic management is presented and implemented. For the ultrasonic management mechanism, the unknown node asserts whether the match is availability or not by recording the number of RF signals received from different beacon nodes in a cycle. The wrong results will be rejected.Because the beacon nodes transmit the ultrasonic and RF signals at the same time, the energy consumption of this system is high. To solve the problem, this paper presents and implements the mechanisms for energy-saving. For the energy-saving mechanism, beacon nodes switch their state with wireless signals from unknown nodes to make more beacons being in sleeping state. The experiment results show that the performance of the indoor localization system with mechanisms mentioned above is improved. The solutions could reduce the localization error rate, and extend the lifetime of localization system. |
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