Research And Implementation Of Wireless Sensor Networks Positioning Technology Based On Time Measurement

This thesis focuses on time-measurement-based positioning algorithm, which compared with other positioning algorithm, has more accurate positioning accuracy. Higher though the hardware requirements are, with the advancement of technology, hardware costs will be reduced, time-measurement-based positioning algorithm must be applied more and more widely, therefore, it's significant for us to study it. Main tasks are as follows:1. On the basis of reading a large amount of related articles, the research status quo of WSN positioning techniques at home and abroad is introduced. The criterions of performance evaluation and the classification methods for WSN positioning techniques are also discussed. The principles and characteristics of recent representative positioning approaches are summarized.2. Aimed at the disadvantage that the calculation of two stage Taylor series expansion method is too large, a modified method is proposed, which makes a tradeoff between calculation and positioning success rate. Simulation confirms that the calculation is reduced obviously. Aimed at avoiding the drawbacks of current TDOA positioning algorithm, an improved method is proposed, in which the time synchronization is free. The improved method performs more accurate and possesses better practicability.3. The Cramer-Rao bounds of TO A, RT-TOA and TDOA are deduced and the factors related to those bounds are discussed. Given the bounds properly is of great significance for unbiased estimator evaluation.4. For the positioning error is related to the topology composed by anchor nodes, it is necessary to study the relationship between anchor nodes' deployment and positioning error. Based on the analysis of positioning fuzzy region, the function of average positioning error is constructed which is the emphasis of following discussion. The discussion achieves that when the topology shaped by anchor nodes is an equilateral triangle, the average positioning error is minimized. This criterion can work as a guide for the depolyment and choice of anchor nodes.5. A positioning algorithm similar to RT-TOA has been realized on nanoLOC nodes. To achieve a high accuracy, ranging is taken at both sides, so that high location performance is guaranteed. Under indoor and outdoor environment, the system has been tested, result shows a good positioning performance.Finally, the thesis summarizes all the completed work and gives out the prospect of future work.