Positioning system using radio signal sent from node

A node position measuring system comprising:

• a node which sends a position measuring signal;
• and
• a plurality of access points which monitor for radio signals from the node, wherein:
• each of the access points comprises a signal reception timing measuring module which receives the position measuring signal from the node through a predetermined channel;
• each of at least two of the access points comprises a reference signal generating module which sends a reference signal after the signal reception timing measuring module receives;
• the position measuring signal
• at least three of the access points measure respective reception timings of the position measuring signal and respective reception timings of the reference signal by the respective signal reception timing measuring modules;
• and
• a position calculating module which calculates a 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, and
• wherein the at least one of the reference signal generating modules sends the reference signal with a passage of a predetermined delay time set to be longer as a strength of the received position measuring signal is lower, and the position calculating module calculates the position of the node by using a reference signal first received among reference signals sent by each of at least two of the access points.

A radio access point in a node positioning system which measures a position of a node to send a position measuring signal, comprising a signal reception timing measuring module and a communication unit, wherein

• the signal reception timing measuring module monitors the position measuring signal from the node through a predetermined channel, measures a reception timing of the position measuring signal, and measures reception timings of a reference signal sent from another access points after receiving the position measuring signal;
• and
• the communication unit sends the reception timing of the position measuring signal and the reception timing of the reference signal or a reception timing difference between the position measuring signal and the reference signal to a position calculating module which calculates a position of the node by using information regarding the reception timings of a reference signal first received among the reference signals sent by other access points and position information of at least three of access points which received the position measuring signal and the reference signal, and
• wherein the at least one of other access points sends the reference signal a passage of a predetermined delay time after receiving the position measuring signal, and the predetermined delay is set to be longer as a strenght of the received position measuring signal is lower.

A node position measuring system, comprising:

• a node which sends a position measuring signal;
• a plurality of reference stations each of which sends a reference signal;
• and
• a plurality of access points which monitor radio signals from the node, wherein each of the access points comprises a signal reception timing measuring module which receives the position measuring signal from the node through a predetermined channel, each of the reference stations sends the reference signal after the position measuring signal is received, and at least three of the access points receive the position measuring signal and the reference signal, and measure a reception timing of the position measuring signal and reception timings of the reference signals by the respective signal reception timing measuring modules, and
• wherein the node position measuring system further comprises a position calculating module which calculates a 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 at least three of the access points, and
• wherein the at least one of reference stations sends the reference signal with a passage of a predetermined delay time set to be longer as a strength of the received position measuring signal is lower, and the position calculating module calculates the position of the node by using a reference signal first received among reference signals sent by each of the plurality of the reference stations.

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, a plurality of reference stations to send a reference 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 the reference stations to send the 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 timing 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 at least three of the access points,
• wherein the at least one of reference stations 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 the plurality of the reference stations.