  The proliferation of wireless localization technologies provides a promising
future for serving human beings in indoor scenarios. Their applications include
real-time tracking, activity recognition, health care, navigation, emergence
detection, and target-of-interest monitoring, among others. Additionally,
indoor localization technologies address the inefficiency of GPS (Global
Positioning System) inside buildings. Since people spend most of their time in
indoor environments, indoor tracking service is in great public demand. Based
on this observation, this paper aims to provide a better understanding of
state-of-the-art technologies and stimulate new research efforts in this field.
For these purposes, existing localization technologies that can be used for
tracking individuals in indoor environments are reviewed, along with some
further discussions.
