Geolocation of cellular phone using supervisory audio tone transmitted from single base station
First Claim
1. A method of geolocating a wireless communication device comprising the steps of:
- (a) transmitting a supervisory audio tone (SAT) signal from a base station;
(b) receiving said SAT signal returned from said wireless communication device;
(c) subjecting said SAT signal transmitted in step (a) and said SAT signal received in step (b) to a range processing operation so as to determine the range of said wireless communication device from said base station;
(d) subjecting signals received by said base station from said wireless communication device to a direction processing operation so as to determine the direction of said wireless communication device relative to said base station; and
(e) identifying the location of said wireless communication device in accordance with said range and direction.
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Accused Products
Abstract
In order to geolocate a wireless communication device (cellular phone) initiating a 911 call, a base station transceiver transmits a supervisory audio tone (SAT), which is automatically looped back by the calling cellular phone. Returned SAT signals are correlated with those transmitted to determine the range of the cellular phone. In addition, incoming signals from the cellular phone, such as the returned SAT signals, are received by a phased array antenna and subjected to angle of arrival processing to determine the direction of the cellular phone relative to the base station. Given this angle of arrival and range information the cellular phone is geolocated. Since the total travel distance of SAT signals between the base station and the cellular phone traverses a two-way path from the base station to the cellular phone and back, plus a loopback path through the circuitry of the phone, the range R of the cellular phone from the base station is calculated in accordance with the equation R=Cxm/2−k, where C is the velocity of light, m is a correlation time shift interval, and k is a correction factor associated with the loopback path, and varies with manufacturer and phone type. The value of k is provided by the phone manufacturer and is accessed using equipment serial number information conveyed in the incoming control channel call establishment request from the calling phone.
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Citations
27 Claims
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1. A method of geolocating a wireless communication device comprising the steps of:
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(a) transmitting a supervisory audio tone (SAT) signal from a base station;
(b) receiving said SAT signal returned from said wireless communication device;
(c) subjecting said SAT signal transmitted in step (a) and said SAT signal received in step (b) to a range processing operation so as to determine the range of said wireless communication device from said base station;
(d) subjecting signals received by said base station from said wireless communication device to a direction processing operation so as to determine the direction of said wireless communication device relative to said base station; and
(e) identifying the location of said wireless communication device in accordance with said range and direction. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of geolocating a wireless communication device relative to a base station comprising the steps of:
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(a) monitoring wireless communication request activity via a phased array antenna at said base station;
(b) in response to receiving an incoming call establishment request from said wireless communication device, transmitting a supervisory audio tone (SAT) signal from said base station to said wireless communication device and conducting a direction processing operation so as to determine the direction of said wireless communication device relative to said base station;
(c) processing said SAT signal transmitted from said base station in step (b) and SAT signals returned from said wireless communication device in accordance with a range determination operation so as to establish the range between said wireless communication device and said base station; and
(d) identifying the location of said wireless communication device in accordance with said range and direction. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. An arrangement for geolocating a wireless communication device comprising:
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a base station transceiver which is operative to transmit a supervisory audio tone (SAT) signal to said wireless communication device and to receive said SAT signal as returned from said wireless communication device; and
a signal processing unit, which is coupled to said base station transceiver and is operative to subject signals received from said wireless communication device to a direction processing operation so as to determine the direction of said wireless communication device relative to said base station, and to subject said transmitted SAT signal transmitted and said returned SAT signal to a range processing operation to determine the range of said wireless communication device from said base station, so that the location of said wireless communication device may be established in accordance with said range and direction. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
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Specification