Determining positioning of wireless terminal in telecommunications network

• US 8,654,010 B2
• Filed: 04/12/2007
• Issued: 02/18/2014
• Est. Priority Date: 04/12/2007
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Wigren, Torbjrn
• Primary Examiner(s): LIU, HARRY K
• Application Number:
  US12/595,317
• Publication Number:
  US 20100117898A1
• Time in Patent Office: 2,504 Days
• Field of Search: 342463-464, 3423572-35778, 342/450, 342/458, 342386-387, 342/465, 342/366, 370/338, 455/456.1
• US Class Current: 342/387
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type
• CPC Class Codes: G01S 5/0273 using multipath or indirect path propagation signals in position determination
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

In one of its aspects the technology concerns a method of determining a position of a wireless terminal in a radio access network using information of the travel time of radio waves between a base station and the wireless terminal, the travel time information being retrieved in a way consistent with SUPL positioning. The method comprises performing, at the wireless terminal, a time of arrival measurement for a respective downlink radio frame received from a node associated with a cell of a radio access network. The method thereafter uses the time of arrival measurement and an estimated time of downlink transmission from the node to make a determination of a distance between the wireless terminal and the node. The distance so determined can be used to generate an ellipsoid arc for describing a round trip time positioning of the wireless terminal. As an optional enhancement, the method further includes generating a thickness dimension of the ellipsoid arc, the thickness dimension of the ellipsoid arc reflecting clock uncertainty.

Claims

1. A server which is external to a radio access network, the server comprising:

a signaling interface through which the server is adapted to receive, from a wireless terminal of the radio access network and without invoking any radio access network protocol;

a first report comprising at least two information elements determined at a known universal clock time, the at least two information elements comprising;

a wireless terminal position; and

a location certain time of arrival measurement for a downlink radio frame received by the wireless terminal from a node associated with a cell of a radio access network;

a second report comprising;

a location uncertain time of arrival measurement for a subsequent downlink radio frame received by the wireless terminal;

a timer value indicative of time elapsed since determination of the known universal clock time;

a controller configured to;

estimate an estimated time of transmission of the subsequent downlink radio frame;

determine a current radio travel time as a difference between the estimated time of transmission of the subsequent downlink radio frame and the location uncertain time of arrival measurement of the subsequent downlink radio frame;

estimate a distance between the node and the wireless terminal using the current radio travel time and a geographical position of the node;

use the timer value to estimate a clock drift error of the wireless terminal;

use the distance between the node and the wireless terminal generate an ellipsoid arc for describing a range of possible geographical positions of the wireless terminal and use the timer value generating a thickness dimension of the ellipsoid arc.

2. The server of claim 1, wherein the controller is further adapted to determine the estimated time of downlink transmission using time of arrival measurements received from plural terminals of the cell.

3. The server of claim 1, wherein the universal clock time is maintained external to the radio access network.

4. The server of claim 1, wherein the controller is further configured to generate the ellipsoid arc for describing a single trip time positioning of the wireless terminal.

5. The server of claim 1, wherein the server is a Secure User Plane Location (SUPL) Location Platform (SLP) server and wherein the first report and the second report comprise SUPL signaling.

6. The server of claim 2, further comprising an interface for receiving, for each time of arrival measurement, a corresponding cell identity.

7. The server of claim 2, wherein the controller is further adapted to use a Kalman filter to determine the estimated time of downlink transmission, for a specific cell, by using:

(1) time of arrival measurements received from the plural terminals of the cell;

(2) wireless terminal position measurements from the plural terminals of the cell corresponding in time to said plural time of arrival measurements;

(3) information indicative of position of the node; and

wherein (1) and (2) are received as a pair, each pair corresponding to one wireless terminal.

8. The server of claim 7, wherein said Kalman filter is configured to process a measurement model, for each of the pairs of measurements, said measurement model being dependent on:

received time of arrival measurement of the pair and a corresponding measurement error variance;

received wireless terminal position of the pair and a corresponding measurement error variance; and

,

the information indicative of the position of the node.

9. The server of claim 8, wherein said Kalman filter is based on a random walk model.

10. The server of claim 9, wherein said Kalman filter is further based on an integrated random walk model.

11. A method of determining position of a wireless terminal in a radio access network, the method comprising:

generating, at the wireless terminal;

a first report comprising at least two information elements determined at a known universal clock time, the at least two information elements comprising;

a wireless terminal position; and

a location certain time of arrival measurement for a downlink radio frame received by the wireless terminal from a node associated with a cell of a radio access network;

a second report comprising;

a location uncertain time of arrival measurement for a subsequent downlink radio frame received by the wireless terminal;

a timer value indicative of time elapsed since determination of the known universal clock time;

using a controller at a server to;

estimate an estimated time of transmission of the subsequent downlink radio frame;

determine a current radio travel time as a difference between the estimated time of transmission of the subsequent downlink radio frame and the location uncertain time of arrival measurement of the subsequent downlink radio frame;

estimate a distance between the node and the wireless terminal using the current radio travel time and a geographical position of the node;

use the timer value to estimate a clock drift error of the wireless terminal;

use the distance between the node and the wireless terminal to generate an ellipsoid arc for describing the position of the wireless terminal;

use the timer value to generate a thickness dimension of the ellipsoid arc.

12. The method of claim 11, wherein the controller is further adapted to determine the estimated time of downlink transmission using time of arrival measurements received from plural terminals of the cell.

13. The method of claim 11, further comprising maintaining the universal clock time external to the radio access network.

14. The method of claim 11, further comprising using the distance between the wireless terminal and the node to generate the ellipsoid arc for describing a single trip time positioning of the wireless terminal.

15. The method of claim 12, further comprising the plural terminals of the cell each sending plural wireless terminal position measurements to the server, the wireless terminal position measurements corresponding in time to the time of arrival measurements, and using the wireless terminal position measurements for determining the estimated time of downlink transmission.

16. The method of claim 15, further comprising sending a cell identity from the wireless terminal to the server, the cell identity corresponding to the time of arrival measurement.

17. The method of claim 15, further comprising using a Kalman filter to determine the estimated time of downlink transmission, for a specific cell, the Kalman filter using:

(1) time of arrival measurements received from plural wireless terminals;

(2) plural wireless terminal position measurements from the plural terminals of the cell corresponding in time to said plural time of arrival measurements;

(3) information indicative of position of the node; and

wherein (1) and (2) are received as a pair, each pair corresponding to one wireless terminal.

18. The method of claim 17, further comprising using the Kalman filter to process a measurement model, for each of the pairs of measurements, the measurement model being dependent on:

received time of arrival measurement of the pair and a corresponding measurement error variance;

received wireless terminal position of the pair and a corresponding measurement error variance; and

,

the information indicative of the position of the node.

19. The method of claim 18, wherein said Kalman filter is based on a random walk model.

20. The method of claim 19, wherein said Kalman filter is further based on an integrated random walk model.

21. The method of claim 11, wherein the server is a Secure User Plane Location (SUPL) Location Platform (SLP) server and therein the method further comprises transmitting the first report and the second report using SUPL signaling.