ZigBee Wireless Indoor Positioning System Based On Accurate Measurement For Ultrasonic TOF

The rapid development of wireless communication technology and electronic technology force that sensors can be developed for the low cost, low power consumption and functional integration of sensor nodes. Information acquisition technology used by sensors is developing in the tendency of integration, intelligence and miniaturization. Then the wireless sensor network emerged and grows into the representative of new information acquisition technology. These characteristics of wireless sensor network, promote the development of wireless positioning technology. Recently, although research of outdoor positioning technology has achieved good results, research of indoor positioning technology is in a fledging period. Therefore the research of indoor positioning is significant.The main work of this paper is as follows:1. An indoor wireless positioning system is designed with ZigBee protocol which has features of low cost, low rate and low power. Wireless communication network is built by ZigBee protocol to transmit data between nodes. 2. Some typical propagation medium and positioning algorithms for positioning system are introduced, and then according to the characteristics of indoor environment ultrasonic singnals are selected to serve as the propagation medium of our positioning system. And TOA positioning algorithm is adopted to compute locations of nodes.3. In applications of ultrasonic measurement, since synchronization between transmitters and receivers can significantly affect on measurement accuracy, so we provide a solutions to improve the synchronization between transmitters and receivers:clock drift compensation. We also carry out experiments and simulations about the solution, and the results show that measurement errors are reduced.4. Hardware platform has been built to implement the proposed approaches. CC2530from Texas Instruments is employed as microcontroller and radio module of system nodes. After designing, we test these sensor nodes and the results indicate that the performance of real-time and reliability is relative nice. Moreover, to reduce power consumption of nodes, adaptive transmit power mechanism is adopted and simulated. The simulation result shows that the consumption of sensor nodes can be reduced significantly.