Patent ID: 7627329

Claim:
A method of measuring a position of a node by using a radio communication system which includes the node to send a position measuring signal, and a plurality of access points to receive radio signals from the node, the method comprising: causing the access points to monitor the position measuring signal from the node through a predetermined channel; causing each of at least two of the access points to send a reference signal after receiving the position measuring signal; causing at least three of the access points to measure respective reception timings of the position measuring signal and respective reception timings of the reference signal; and calculating the position of the node by using the reception timings of the position measuring signal and the reception timings of the reference signal measured by the access points which received the position measuring signal and the reference signal, and position information of the access points which received the position measuring signal and the reference signal, wherein the at least one of the access points sends the reference signal with a passage of a predetermined delay time after receiving the position measuring signal, the predetermined delay is set to be longer as a strength of the received position measuring signal is lower, and the position of the node is calculated by using a reference signal first received among reference signals sent by each of at least two of the access points.