POSITIONING PORTABLE TERMINAL, METHOD AND SYSTEM FOR SPECIFYING POSITION OF PORTABLE TERMINAL, AND SECURITY SYSTEM USING PORTABLE TERMINAL

摘要

PROBLEM TO BE SOLVED: To specify the positions of portable terminals in a wireless communication system provided with asynchronous base stations. SOLUTION: The asynchronous base stations each include a GPS receiver and acquire GPS time on the basis of GPS signals from GPS satellites. The base stations periodically transmit beacon signals. The beacon signals carry information on the acquired GPS time; time delays from the most recent GPS time to the transmission of the beacon signals; ID numbers of the base stations; and base station position information. A portable terminal which has received the beacon signals computes propagation delay times of the beacon signals on the basis of the times of reception of the beacon signals; the most recent GPS time acquired from the beacon signals; and the time delays from the most recent GPS time to the transmission of the beacon signals. The difference of the propagation delay time from each base station is computed by subtracting the propagation delay times from one another. The position of the portable terminal is computed on the basis of the computed differences of the propagation delay times and the base station position information. COPYRIGHT: (C)2007,JPO&INPIT