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We propose an IEEE 802.11b wireless LAN location system based on the time difference of arrival (TDOA) method. We confirm that IEEE 802.11b, as part of an indoor location system, is potentially highly accurate because of its broad bandwidth. When a location system is implemented in the IEEE 802.11b system, there are two important considerations; system architecture and required positioning accuracy. The accuracy of an indoor location system is apt to be degraded by multipath fading, which is a complex characteristic of indoor propagation. We developed a TDOA location system based on IEEE 802.11b, including several techniques such as access point (APs) synchronization, leading edge timing observations, and averaging with diversity. We experimentally evaluated the proposed system in a storehouse. The positioning accuracy when using ten APs and 3-branch diversity was 2.4 m at the 67th percentile.