Atsushi Ogino

TDOA location system for IEEE 802.11b WLAN

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 67/sup th/ percentile.

A study on the accuracy of a CDMA-based location system

Recently, positioning of the handset from which the calls occur has been required for public safety. For emergency services, USA wireless carriers have been obligated to provide a position location at the handset and the services are called Enhanced 911 (E911). We have developed a IS-95-based location system which uses forward link trilation (FLT) techniques. Performance evaluations in various environments through simulations are often required and the evaluation technique is the key issue for efficient development of such location systems. In this paper, the simulation model proposed here is verified with a field trial. The simulation results and the trial results show good agreement. The results show that the proposed scheme could give the ability to evaluate the performance of the location system. Then, this paper shows simulation results of the location accuracy in typical environments with actual geometric configuration of the handset and the base stations. The results show that the location system achieves positioning accuracy which satisfies the E911 requirements.