Method and apparatus for determining an algebraic solution to GPS terrestrial hybrid location system equations

• US 6,289,280 B1
• Filed: 12/10/1999
• Issued: 09/11/2001
• Est. Priority Date: 12/10/1999
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Soliman, Samir S., Agashe, Parag A., Vayanos, Alkinoos Hector, Fernandez-Corbaton, Ivan J.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Beaulieu, Yonel
• Application Number:
  US09/460,180
• Time in Patent Office: 641 Days
• Field of Search: 701/214, 701/207, 701/116, 701/300, 342/357.01, 342/357.06, 342/357.08, 342/357.09, 342/357.1, 342/357.02, 340/988, 340/991
• US Class Current: 701/214
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type

Abstract

A method and apparatus for use in a hybrid position location system. The method and apparatus combines measurements from Global Positioning System (GPS) and terrestrial transceiver stations to compute the location of a device. An algebraic solution to hybrid position location system equations is output from the method and apparatus. The method and apparatus determines the position of a device using a non-iterative method, as against the use of a conventional iterative least mean square method. The method of the present invention can be used to solve the location system equations in scenarios where a non-iterative solution is desirable. In certain scenarios, the location system equations may have two possible solutions. An iterative method would converge on one of the solutions, without any indication of the existence of the other ambiguous solution. Moreover, the iterative method may converge on the incorrect of the two ambiguous solutions. Use of the presently disclosed method and apparatus yields both the ambiguous solutions. The disclosed method may be followed up with iterative methods, using the solutions from the algebraic method as initial estimates of the device location for the iterative method. A different process can then select the correct solution. Thus, the algebraic method can be used to detect the existence of ambiguous solutions, and to find both solutions.

Claims

1. A method for determining in a processing unit the location of a device including:

a) receiving range information, pseudo-range information, and difference of arrival information related to a particular location sought to be determined, the range information being the distance between the location of the device and a first transmission point, the pseudo-range information being the distance between the location of the device and a second transmission point plus a clock bias, and the difference of arrival information being the difference between the time at which a reference signal transmitted from a third transmission point arrived at the location of the device and the time at which a second signal transmitted from a fourth transmission point arrived at the location of the device;

b) using a plane-wave approximation to eliminate any unknown second order terms associated with the pseudo-range information;

c) substituting a first quadratic variable for any unknown second order terms in the range information;

d) constructing a coordinate frame with one of the transmission points associated with the range information, the pseudo-range information, or the difference of arrival information as the origin of the coordinate frame;

e) expressing as a set of equations, the range difference of arrival, range, and pseudo-range information in terms of the newly constructed coordinate frame;

f) substituting a second quadratic variable for the coordinates of the unknown location, thus placing the equation for the difference of arrival, range, and pseudo-range information in the same form;

g) concatenating the equations for the range, pseudo-range and difference of arrival information into a single set of equations;

h) expressing the coordinates of the location of the device and the time bias as a function of the quadratic variable;

i) solving for the second quadratic variable, and thus determining two solutions for the location sought; and

j) outputting the location sought.

2. A method of determining in a processing unit the position of a device, including:

a) selecting an initial position estimate having an assumed accuracy;

b) linearlizing second order satellite and altitude aiding measurements around the initial estimate;

c) solving for the position of the device using the linearized satellite and altitude aiding measurements;

d) disregarding any solution for the position of the device that is more inaccurate than the assumed accuracy of the initial position estimate;

e) accepting any solution for the position of the device that is more accurate than the assumed accuracy of the initial position estimate; and

f) output the acceptable solutions for the position of the device.

3. The method of claim 2, wherein at least one of the acceptable solutions for the position of the device is used as an initial point for an iterative determination of the location of the position sought.

4. The method of claim 2, further including:

a) using at least one of the following criteria to identify a correction solution for the position of the device if more than one solution is more accurate than the assumed accuracy of the initial position estimate;

i) sector angle opening and orientation;

ii) distance to serving base station relative to expected cell size;

iii) relative Least Mean Square (LMS) cost of the two solutions for the position of the device in the case where there is reduncancy;

iv) received signal power; and

v) coverage maps available for network planning.

5. A method of determining in a processing unit the coordinates, and thus the location, of a mobile device, including:

a) receiving altitude aiding information in the form of earth center, earth fixed (ECEF) coordinates representing the location of the mobile device;

b) rotating the ECEF coordinate frame such that the z-axis passes through a point selected as an initial estimate of the location of the mobile device;

c) using the altitude aiding information to provide the value of the z coordinate in the new coordinate frame;

d) receiving one or more of range, pseudo-range, and range difference information;

e) solving for time bias, the y coordinate of the mobile device, and the x coordinate for the mobile device using one of more of the received range, pseudo-range, and range difference information; and

f) outputting the x, y, z coordinates of the mobile device.