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In recent years, there have been many cases of violent crimes against children. As a result there is an increasing need for systems which can identify the current positions of children, and keep watch over them in time slots where they may be alone, such as on the way to and from school. At present, the most typical approach is to have the children carry a wireless terminal so they can be tracked, but the power-saving performance of such devices needs to be improved. As a result, we have proposed a method of estimating the position of children without using GPS, and thereby improved the power-saving performance of the wireless terminals. In addition, we have confirmed through measurement experiments in an experiment field that the position of children can be appropriately estimated using this technique. Figure 1: Number of crimes (murder, abduction, kidnapping) involving children at each level.Figure 2: Abduction/kidnapping crimes by location outside the home (2009). 117 24-25,

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