Iterative delay compensation algorithm to mitigate NLOS influence for positioning

It is important for sensor networks to estimate the sensor tag accurately, 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. 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 (DCOMF), and reliability of each node is decided by reliability weight function (RELF). Finally, abnormal error occurred in serious NLOS environment is improved by limitation method. By those iterative processes, the positioning accuracy is improved.