摘要：AbstractThe extensive usages of WLANs and mobile devices have increased the interest in Indoor localization systems for wireless environments. In the context of wireless-based localization system, researchers have always focused on device-based localization system, in which tracked entities must have a device attached. This practice for many years developed localization systems like Global Positioning System; Radio Frequency based system, Ultrasonic bases system and Infrared base systems. These all location based systems need a device to be attached with tracked entity, in order to run part of localization algorithm. Thus, all these systems are called as active device-based location systems. Recently a new concept device-free localization system is introduced; this system can detect and track any entity without carrying any radio device or participating actively in the localization process. A human body is detected in the device-free localization system by observing the changes in the received signal strength of WLAN environment. This paper presents a comprehensive survey of various techniques of the device-free localization system.
