Research On Indoor Positioning Algorithm Based On RFID Tags

With the development of computer and communication technology, the demand for goods or person’s location is also growing strongly and the positioning technology is developing rapidly. Outdoor positioning system such as GPS is most well-known. However, GPS cannot get a good result on the location in a small range place because of the impact on the surrounding environment. Therefore, the study on indoor location positioning technology has become a focus of research. RFID technology has low cost tags and non-line identification, which makes an advantage over other indoor positioning technology.This paper studies indoor positioning algorithm based on the RFID tags, especially for classic LANDMARC indoor positioning system which we have conducted in-depth research and completed optimization. The factors that influence indoor positioning accuracy from the system layout and positioning algorithm have been analyzed and improved through its shortcomings.Firstly, for the system layout, the principle of cellular is used to adjust the place of reference tags and readers. So it completes using the minimum reader to read the maximum reference tags in order to avoid the problem of signal interference and redundant calculations caused by excessive reference tags and the problem of positioning accuracy caused by bare reference tags.Secondly, for the positioning algorithm, because LANDMARC location system is based on the "nearest neighbor distance" idea, and the k-nearest neighbor method has low efficiency and the great amount of calculation when it chooses nearest neighbors, an improvement is made on its shortcomings. And a k*- nearest neighbor method based on LANDMARC indoor positioning systems is proposed. And k*- nearest neighbor method is used to choose k-nearest reference tags that has nearest distance to the tags to be positioned twice, and then we calculate the position coordinates of tags to be positioned based on the coordinates of obtained k-nearest neighbors. The way that we calculate coordinates after choosing tags has greatly reduced the computation of the system and improved the efficiency of the algorithm.Finally, a new weight formula is set in calculating the position coordinates of tags to be positioned in order to reduce the system’s positioning errors and improve the positioning accuracy of system.By the simulation experiments we have proved that the LANDMARC indoor location based on k*- nearest neighbor algorithm has a big advantage. Comparing to the traditional location algorithm we have found that the positioning error of the improved algorithm is smaller, and the positioning accuracy is greatly improved.