Method and system for locating a mobile terminal in a cellular radio network

• US 20020107028A1
• Filed: 02/02/2001
• Published: 08/08/2002
• Est. Priority Date: 02/02/2001
• Status: Active Grant

• Current Assignee: Callahan Cellular LLC (Intellectual Ventures LLC)
• Original Assignee: Nokia Mobile Phones UK Limited (Nokia Corporation)
• Inventors: Rantalainen, Timo, Moilanen, Jani
• Granted Patent: US 6,665,540 B2
• Time in Patent Office: Days
• US Class Current: 455/456.6
• CPC Class Codes: G01S 1/026 of associated receivers
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A method and system for estimating the location of a mobile station in a cellular radio network having a reference base station and a plurality of neighboring base stations capable of communicating with the mobile station. At the beginning of the E-OTD measurements, the mobile station may be provided with the expected OTD values in the reference base station site, possibly instead of RTD values of the neighboring base stations, in order to make it possible for the mobile station can calculate the uncertainty in the measured OTD due to the unknown location of the mobile station. In an alternative scenario the network provides the mobile station the expected OTD values in the current location of the mobile station, and the estimated uncertainty of those values. When the uncertainty is greater than a predetermined value, the mobile station makes the E-OTD measurements based on the SCH bursts. When the uncertainty is smaller than the predetermined value, the mobile station makes the measurements based on normal/dummy bursts, and/or aligns the time window for taking samples from signals received from the neighboring base stations.

Claims

1. A method of estimating a location of a mobile station in a mobile telecommunications network having a first base station, and a plurality of second base stations neighboring the first base station for providing communication links to the mobile station, wherein the first base station is located at a first site and second base stations are located at respective second sites, and the first and second base stations provide synchronization channel bursts and further bursts to the mobile station for allowing the mobile station to make arrival time measurements, said method comprising the steps of:

providing the mobile station a first value regarding transmission of signals from the respective second base stations to the mobile station;

calculating a second value representative of an uncertainty in said arrival time measurements based on the first value and optionally a distance from the first site to the mobile station; and

providing the mobile station a predetermined value such that the mobile station makes said arrival time measurements based on the synchronization channel bursts when the second value is greater than the predetermined value, and the mobile station carries out a time adjustment process when the second value is smaller than or equal to the predetermined value.

2. The method of claim 1, wherein the first station is a serving station to the mobile station, and the first value is indicative of an expected arrival time of the signals from the respective second base stations to the mobile station as if the mobile station is located at the first site

3. The method of claim 2, wherein the distance from the first site to the mobile station is provided to the mobile station by the network.

4. The method of claim 1, wherein the first base station is a serving station to the mobile station, and wherein the first value is indicative of distances between the first site and the respective second sites and the distance from the first site to the mobile station is provided to the mobile station by the network.

5. The method of claim 1, wherein the first base station is a serving station to the mobile station, and wherein the first value is indicative of distances between the first site and the respective second sites.

6. The method of claim 1, wherein the first value is indicative of an expected arrival time of signals from the respective second base stations to a current location of the mobile station, and the second value is calculated by a serving mobile location center and provided to the mobile station.

7. The method of claim 6, wherein the first value is estimated by the serving mobile location center and provided to the mobile station.

8. The method of claim 6, wherein the second value is calculated partly based on a cell identity of the first base station.

9. The method of claim 6, wherein the second value is calculated partly based on a cell identity of the serving base station.

10. The method of claim 6, wherein the second value is calculated partly based on antenna sector information regarding a location of the mobile station.

11. The method of claim 6, wherein the second value is calculated partly based on received signal levels from the first and second base stations as reported by the mobile station.

12. The method of claim 2, wherein the second value is calculated by the mobile station.

13. The method of claim 3, wherein the second value is calculated by the mobile station.

14. The method of claim 1, wherein the mobile station makes the arrival Lime measurements based on the further bursts in the time adjustment process when the second value is smaller than or equal to the predetermined value.

15. The method of claim 1, wherein the mobile station aligns a time window for taking samples in the signals transmitted from the respective second base stations in the time adjustment process when the second value is smaller than or equal to the predetermined value.

16. The method of claim 1, wherein the mobile station further makes the arrival time measurements based on the further bursts, in addition to making said arrival time measurements based on the synchronization channel bursts, when the second value is greater than the predetermined value.

17. The method of claim 1, wherein the predetermined value is stored in the mobile station.

18. The method of claim 1, wherein the predetermined value is provided to the mobile station by the network.

20. The system of claim 19, wherein the first base station is a serving base station to the mobile station, and the first value is indicative of an expected arrival time of the signals from the respective second base stations to the mobile station as if the mobile station is located at the first site.

21. The system of claim 19, wherein the first base station is a serving base station to the mobile station, and the first value is indicative of a distance between the first. site and a respective second site.

22. The system of claim 19, wherein the first value is indicative of an expected arrival time of the signals from the respective second base stations to a current location of the mobile station.

23. The system of claim 19, wherein the first station is a reference station and the expected arrival time of the signals from the respected second base stations to the current location of mobile station is estimated by a serving mobile location center.

24. The system of claim 19, wherein the second means is located in the mobile station.

25. The system of claim 19, wherein the second means is located in a serving mobile location center.

26. The system of claim 19, wherein the mobile station makes said arrival time based on the further bursts in the time adjustment process when the second value is smaller than or equal to the predetermined value.

27. The system of claim 19, wherein the mobile station aligns a time window for taking samples in the transmitted signals from the respective second base stations in the time adjustment process when the second value is smaller than or equal to the predetermined value.

28. The system of claim 19, wherein the predetermined value is stored in the mobile station.

19. A system for estimating a location of a mobile station in a mobile telecommunications network having a first base station and a plurality of second base stations neighboring the first base station for providing communication links to the mobile station, wherein the first base station is located at a first site and second base stations are located at respective second sites, and the first and second base stations provide synchronization channel bursts and further bursts to the mobile station for allowing the mobile station to make arrival time, said system comprising:

a first means for providing the mobile station a first value regarding transmission of signals from the respective second stations to the mobile station;

a second means, responsive to the first value, for providing a second value representative of uncertainty in said arrival time measurements based on the first value and optionally a distance from the first cite and the mobile station; and

a third means, responsive to the second value and a predetermined value, for making said arrival time measurements based on the synchronization channel bursts when the second value is greater than the predetermined value, and the mobile station carries out a time adjustment process when the second value is smaller than or equal to the predetermined value.