Method and apparatus for locating a remote unit within a communication system

• US 6,973,320 B2
• Filed: 04/29/2002
• Issued: 12/06/2005
• Est. Priority Date: 04/29/2002
• Status: Expired due to Fees

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Brown, Larry Michael, Miller, Marty Frank, Zerfas, Norman Joseph
• Primary Examiner(s): Trinh, Sonny
• Assistant Examiner(s): NGUYEN, KHAI MINH
• Application Number:
  US10/134,282
• Publication Number:
  US 20030203738A1
• Time in Patent Office: 1,317 Days
• Field of Search: 4554561-4566, 455/502, 455/403, 455/423, 455/457, 455/440, 455/441, 455/422, 4554041-4042, 455/422.1, 340988-996
• US Class Current: 455/456.1
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

Timing Advance information is obtained from base stations (103–105), and is utilized by a remote unit (113) to approximate the Time of Arrival (TOA) of the signals from each base station. The remote unit (113) accesses a single base station to determine its timing advance. In order to increase accuracy, the remote unit (113) then repeats the process, but during the next iteration, the transmission timing is advanced or delayed by a fraction of a bit (e.g. ¼ bit). The base station responds with a new timing advance value. This process is repeated until it is determined how many fractions of bit increments the remote unit (113) is away from a known timing advance boundary of the base station. Once known, this information is utilized to determine the location of the remote unit (113).

Claims

1. A method for locating a remote unit within a communication system, the method comprising the steps of:

transmitting a first message to a base station;

determining a timing advance based on the first message;

advancing or retarding transmission circuitry;

transmitting a second message to the base station;

determining a second timing advance based on the second message;

determining a location based on advancing or retarding transmission circuitry by a fraction of a timing-advance bit;

wherein the step of determining a distance from the base station comprises the steps of determining a value for C, wherein C is approximately equal to;

D_TA−

(N−

½

)D_ADV where,

D_TA=a distance to a timing-advance boundary;

D_ADV=distance attributed to advancing/retarding the transmission circuitry; and

N=a number of iterations in timing advance that causes a change in the timing advance.

2. The method of claim 1 wherein the step of transmitting the first message comprises the step of transmitting the first message on a Random Access Channel.

3. The method of claim 1 further comprising the steps of:

transmitting a third message to a second base station;

determining a third timing advance based on the third message;

advancing or retarding transmission circuitry;

transmitting a fourth message to the second base station;

determining a fourth timing advance based on the fourth message; and

determining the location based on the first, the second, the third, and the fourth timing advance.

4. The method of claim 3 wherein the step of determining the location comprises the step of determining the location based on a Time of Arrival (TOA) technique.

5. The method of claim 1 wherein the step of determining the location comprises the step of determining a distance from the base station.

6. A method for determining a distance (C) from a base station, the method comprising the steps of:

determining a distance to a timing-advance boundary (D_TA);

determining a distance attributed to advancing or retarding transmission circuitry (D_ADV);

determining a number of iterations (N) of advancing or retarding transmission that causes a change in a timing advance; and

determining C based on D_TA, D_ADV, and N.

7. The method of claim 6 wherein the step of determining the distance attributed to advancing or retarding transmission circuitry comprises the step of determining the distance attributed to advancing or retarding transmission circuit by a fraction of a timing-advance bit.

8. An apparatus for determining location, the apparatus comprising:

a transceiver outputting a first message and a second message, wherein the second message is advanced or retarded in time by a fraction of a timing-advance bit; and

logic circuitry determining a first and a second timing advance value based on the first and the second message and determining a distance from a first base station based on the first and the second timing advance values;

wherein the distance from the firm base station is calculated based on the formula;

D_TA−

(N−

½

)D_ADV where,

D_TA=a distance to a timing-advance boundary

D_ADV=a distance attributed to advancing/retarding the transmission circuitry; and

N=a number of iterations in timing advance that causes a change in the timing advance.

9. The apparatus of claim 8 wherein the first and the second messages comprise messages transmitted on a Random Access Channel (RACH).

10. The apparatus of claim 8 further comprising location finding equipment coupled to the logic unit, the location finding equipment having a first distance from a first base station as an input, having a second distance from a second base station as an input, having a third distance from a third base station as an input, and calculating a location based on the first, the second, and the third distances.