Iterative algorithm using particle filter for positioning in NLOS environment

It is important to estimate the accurate position of sensor tag in sensor network, for example, RFID. Time difference of arrival (TDOA) positioning algorithm is well known as the positioning algorithm of the sensor tag. Therefore, the positioning accuracy of conventional linear search algorithm is decreased exceedingly in non-line-of sight (NLOS) environment. Especially, we adopt IEEE 802.15.4a ultra wideband (UWB) channel model as NLOS condition in order to assume that UWB system is used at indoors for positioning system. In this paper, we propose the iterative NLOS delay compensation algorithm based on TDOA in order to fulfill high accuracy in the damaged propagation through NLOS environment. At first, the temporary position is estimated by normal TDOA method and transmission start time is estimated. Next, the time difference between transmission start time and node arrival time is compensated by delay compensation function (DCF), and reliability of each node is decided by reliability weight function (RWF). By those iterative processes, the positioning accuracy is improved.