Indoor Localization Using 802.11 Time Differences of Arrival

This paper proposes a novel time-based method for determining the position of an IEEE 802.11g transmitter using multiple mutually synchronized 802.11g receivers. By means of baseband signal processing, the proposed algorithm obtains a high-resolution estimate of the time of arrival (TOA) of the long training sequence symbol at each receiver. An estimate of the position of the transmitter is obtained based on the estimation of the time differences of arrival (TDOA) of the symbols and the known fixed locations of the receivers. This paper investigates the effects of carrier and sampling clock offsets, in both frequency and phase, between nodes on the TOA and TDOA estimation error. In real-world experiments in a line of sight, low multipath indoor environment, the method was found to achieve mean errors of 42 cm per symbol for 1-D and 1.39 m per symbol for 2-D position estimation, for ranges of up to 25 m.