A Study Of Indoor Elderly Localization System Based On Wireless Sensor Network

In the background of China’s aging population, the number of empty nesters and the elderly living alone is increasing. The demand of guardianship for the elderly is increasing in the same time. Making sure of the positon of the elderly in real-time is the precondition for providing good service. The emergence of wireless sensor networks makes indoor elderly positioning possible.In this thesis, basic terminologies in wireless sensor networks, the classification and evaluation of localization algorithms are systematically introduced. And several localization algorithms and systems commonly used are summerized.In the indoor environment, the spread of wireless signal is easily interfered by a lot of factors, such as indoor obstacles, refraction material as well as multi-path transmission. Three different path loss models are analized, including free-space propagation model, two-ray ground reflection model and the the shadowing model. Factors which affect the received signal strength indicatior value are analyzed. In this paper, parameters identification experiment based on shadowing model is designed by using TI’s CC2530development kit. The least squares fitting method is used to fit the ranging model and estimate model parameters. Combined with the experimental measurement data, the indoor ranging model is corrected in the same time. The indoor elderly localization system is designed on the basis of corrected ranging model, including coordinator node, reference node, blind node and embeded gateway. Localization principle of the system as well as software design flow of each part are described in detail.A series of indoor localization measurements are made in different experimental conditions. The results showed that, within the range of3m x3m’distance, the accuracy of the elderly localization system is maintained in the range of0.69m.