Wireless sensor network using hybrid TDOA/RSS tracking of uncooperative targets

Accurate tracking of uncooperative wireless target devices, particularly WiFi devices, is valuable for many commercial, industrial and security applications. Tracking based on received signal strength is widely used, but has limited accuracy. The use of time-of-arrival (TOA) measurements can improve accuracy, but as most target devices cannot accurately measure TOA the device is not able to cooperate and time-difference-of-arrival (TDOA) techniques are required. In this paper we present a sensor network for tracking target devices based on both received signal strength and TDOA. A new hybrid algorithm combining both types of measurements based on a particle filter is presented, and shown to perform better than either technique alone. The use of difference of RSS measurements is also shown to give better tracking performance than RSS as errors in the assumed transmit power from the target do not affect the results.