System and method for locating mobile devices
First Claim
1. A system for locating one of a plurality of mobile communications devices, comprising:
- a transmitter for transmitting a first signal, the first signal having a device identification code for identifying a particular mobile communications device to be located and a time indicator;
retransmission circuitry in each of the mobile communications devices for receiving the first signal and transmitting a second signal in response to a match between said identification code of said first signal and an internal identification code;
a plurality of receivers having respective internal clocks for receiving the first signal and setting their respective internal clocks based on the time indicator in the first signal, receiving the second signal, and determining a time difference between said first and second signals; and
control circuitry for determining the location of the particular mobile communications device responsive to time differences determined by multiple receivers.
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Accused Products
Abstract
A system for locating one of a plurality of mobile communications devices is provided. A transmitter (24) transmits a first signal (S1), with the first signal having a device identification code for identifying a particular mobile communications device to be located and a time indicator. Retransmission circuitry (40, 60) in the selected mobile communications device (20) receives the first signal and transmits a second signal (S2) in response thereto. Each of a plurality of receivers (22) has an internal clock. When the first signal is received, these clocks are set based on the time indicator in the first signal. When the second signal is received, a time difference between the first signal and second signal is determined. Network control circuitry (26) determines the location of the particular mobile communications device responsive to time differences determined by multiple receivers.
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Citations
16 Claims
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1. A system for locating one of a plurality of mobile communications devices, comprising:
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a transmitter for transmitting a first signal, the first signal having a device identification code for identifying a particular mobile communications device to be located and a time indicator;
retransmission circuitry in each of the mobile communications devices for receiving the first signal and transmitting a second signal in response to a match between said identification code of said first signal and an internal identification code;
a plurality of receivers having respective internal clocks for receiving the first signal and setting their respective internal clocks based on the time indicator in the first signal, receiving the second signal, and determining a time difference between said first and second signals; and
control circuitry for determining the location of the particular mobile communications device responsive to time differences determined by multiple receivers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for locating one of a plurality of mobile communications devices, comprising:
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transmitting a first signal, the first signal having a device identification code for identifying a particular mobile communications device to be located and a time indicator;
receiving the first signal in the mobile communications devices;
transmitting a second signal from one of the mobile communications devices in response to a match between said identification code of said first signal and an internal identification code;
receiving the first signal in a plurality of receivers having respective internal clocks and setting the respective internal clocks based on the time indicator in the first signal;
receiving the second signal in said receivers;
determining a time difference between reception of said first and second signals; and
determining the location of the particular mobile communications device responsive to time differences determined by multiple receivers. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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Specification