Geolocation of cellular phone using supervisory audio tone transmitted from single base station

• US 6,292,665 B1
• Filed: 10/08/1998
• Issued: 09/18/2001
• Est. Priority Date: 10/08/1998
• Status: Expired due to Term

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Hildebrand, Robert C., Willingham, Julian Bartow, Boyd, Robert W., Hosang, David A.
• Primary Examiner(s): Kincaid, Lester G.
• Application Number:
  US09/168,534
• Time in Patent Office: 1,076 Days
• Field of Search: 455/404, 455/410, 455/411, 455/434, 455/435, 455/456, 455/457, 455/562, 455/132, 342/357, 342/368, 342/450, 342/457, 342/458, 342/357.01, 342/357.02, 342/357.1, 342/357.13
• US Class Current: 455/456.4
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

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=C×m/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.

Claims

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 wherein said range processing operation is operative to compensate for signal travel time over a loopback path through said wireless communication device using a correlation factor stored in a database and accessed with identification information received from the wireless communication device;

(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.

2. A method according to claim 1, wherein step (d) comprises subjecting returned SAT signals received by said base station from said wireless communication device to said direction processing operation to determine the direction of said wireless communication device relative to said base station.

3. A method according to claim 1, wherein step (c) includes correlating said SAT signal transmitted in step (a) with said SAT signal received in step (b).

4. A method according to claim 1, wherein step (d) comprises subjecting signals received by said base station from said wireless communication device other than returned SAT signals to said direction processing operation to determine the direction of said wireless communication device relative to said base station.

5. A method according to claim 1, wherein step (d) comprises subjecting signals received by a base station phased array antenna from said wireless communication device to said direction processing operation to determine the direction of said wireless communication device relative to said base station.

6. A method according to claim 1, wherein step (c) comprises determining range (R) from said base station to said wireless communication device in accordance with the relationship equation R=C×

m/2−

k, where C is the velocity of light, m is a correlation time shift interval, and k is a correction factor associated with said loopback path through said wireless communication device.

7. A method according to claim 1, wherein said wireless communication device comprises a cellular phone.

8. A method of geolocating a wireless communication device relative to a base station comprising the steps of:

(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 based on returned signals only from the wireless communication device;

(c) processing said SAT signal transmitted from said base station in step (b) and SAT signals returned from only 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; and

wherein

step (c) includes correlating said SAT signal transmitted in step (b) with SAT signals received from said wireless communication device,

said range processing operation is operative to compensate for signal travel time over a loopback path through said wireless communication device,

step (b) comprises determining range (R) from said base station to said wireless communication device in accordance with the relationship equation R=C×

m/2−

k, where C is the velocity of light, m is a correlation time shift interval, and k is a correction factor associated with said loopback path through said wireless communication device, and

said correction factor is stored in a database and is accessible in accordance with identification information transmitted to said base station from said wireless communication device.

9. An arrangement for geolocating a wireless communication device comprising:

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 over a phased array antenna at the base station; and

a signal processing unit, which is coupled to said base station transceiver and is operative to subject returned signals received only 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; and

wherein

said signal processing unit is operative to compensate for signal travel time over a loopback path through said wireless communication device,

said signal processing unit is operative to determine range (R) from said base station to said wireless communication device in accordance with the relationship equation R=C×

m/2−

k, where C is the velocity of light, m is a correlation time shift interval, and k is a correction factor associated with said loopback path through said wireless communication device, and

said correction factor is stored in a database and is accessible in accordance with identification information transmitted to said base station from said wireless communication device.