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Indoor localization system using multi-modulation of ultrasonic sensors and digital compass

Several kinds of indoor localization systems have been developed for estimating objectpsilas position lately. They are classified according to the environment, the purpose of application, the media type and so on. In this paper, we propose an improved beacon system, having the ultrasonic media type, which can be used for indoor localization. Moreover, it can estimate the direction of a mobile object by using a digital compass. However it is very hard for the indoor localization system using ultrasonic sensors to achieve much highly precise localization for mobile objects since the ultrasonic sensor is highly sensitive to noises and external shocks. In order to overcome this problem, we adopt a bandpass-filter to protect ultrasonic sensors form external shocks or another noisy signals. In addition, the multi-modulation of ultrasonic sensors-using ultrasonic sensors with different frequency-improves the sampling rate of this system. And we present the application of UKF (Unscented Kalman Filter) to improve the localization performance of our indoor localization system. Consequently, the positioning accuracy and sampling rate of this system has been increased through bandpass-filter and multi-modulation.