Method of locating terminal, and cellular radio system

• US 6,397,073 B1
• Filed: 03/31/2000
• Issued: 05/28/2002
• Est. Priority Date: 10/03/1997
• Status: Expired due to Fees

• Current Assignee: Nokia Networks (Nokia Corporation)
• Original Assignee: Nokia Networks (Nokia Corporation)
• Inventors: Hottinen, Ari
• Primary Examiner(s): Hunter, Daniel
• Assistant Examiner(s): Nguyen, Thuan T.
• Application Number:
  US09/540,913
• Time in Patent Office: 788 Days
• Field of Search: 455/456,457,67.7,67.1
• US Class Current: 455/456.5
• CPC Class Codes: G01C 21/30 Map- or contour-matching
• CPC Class Codes: G01S 5/02528 Simulating radio frequency fingerprints
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

The invention relates to a cellular radio system and a method of locating a terminal in a cellular radio system having in each cell at least one base station 104 communicating with the terminals 100 within its area. The base station measures channel parameters from the signals transmitted by the terminals. The coverage area of each base station is modelled by a digital map. To enable accurate localization of the terminals, to each point on the digital map is added a model of the channel parameters of a signal to be transmitted from the point. The channel parameters estimated from the signal of the terminal are compared with the parameters at different points on the map, and the terminal is located on the basis of the comparison.

Claims

1. A method of locating a terminal in a cellular radio system having in each cell at least one base station communicating with the terminals within its area, comprising:

measuring channel parameters from a signal transmitted by the terminal, wherein measured channel parameters comprise information about the impulse response of the received signal,

modeling the coverage area of each base station by a digital map,

adding a model of channel parameters to each point on the digital map,

locating the terminal by comparing measured channel parameters with the model of channel parameters at the different points on the map.

2. A method as claimed in claim 1, wherein the digital map comprises information about the position of buildings, other obstructions and routes within the coverage area of the base station.

3. A method as claimed in claim 1, wherein the model of channel parameters at each point on the digital map are predetermined and stored in a memory, and in the localization of the terminal, the measured channel parameters are compared with the values in the memory.

4. A method as claimed in claim 3, wherein the model of channel parameters at each point on the digital map are determined by means of the ray tracing technique.

5. A method as claimed in claim 2, wherein the model of channel parameters at each point on the digital map is experimentally determined in such a way that a transmitter is disposed at the point on the map, and the base station measures the parameters of the signal.

6. A method as claimed in claim 1, wherein in the comparison, information is utilized about the direction of arrival of the signal of the terminal.

7. A method as claimed in claim 1, wherein the terminal measures the channel parameters of the signals received from different base stations, and that the terminal and the base station determine a rough location estimate of the terminal on the basis of the measurement results, and that the rough estimate approximation is used in locating the terminal.

8. A method as claimed in claim 1, wherein the base stations closest to the terminal measure the channel parameters of the signal received from the terminal, and that the rough location estimate of the terminal is determined on the basis of the measurement results, and that the rough estimate is used in locating the terminal.

9. A method as claimed in claim 1, wherein in the localization of the terminal, information is utilized about the previous locations of the terminal.

10. A method as claimed in claim 1, wherein the digital map comprises information about the typical speeds of the routes of the base station, and that the base station estimates the speed of the terminal on the basis of the signal of the terminal, and that the speed of the terminal is used for the localization.

11. A cellular radio system comprising in each cell at least one base station communicating with terminals within its area, comprising:

a circuit to measure channel parameters from a signal transmitted by the terminals, wherein the parameters comprise information about the impulse response of the received signal,

a digital map wherein the coverage area of each base station is modeled and a model of channel parameters is added at each point on the digital map, and

a circuit for comparing the measured channel parameters with the model of channel parameters at different points on the map to determine the location of the terminal.

12. A system as claimed in claim 11, wherein the base stations of the system maintain the digital map comprising information about the position of buildings, other obstructions and routes within the coverage area of the base station.

13. A system as claimed in claim 11, wherein the base stations of the system determine the model of channel parameters at each point on the digital map by means of the ray tracing technique.

14. A system as claimed in claim 11, wherein the terminal of the system is arranged to measure the intensity and time delay of the signals received from different base stations, and that the terminal and the base station are arranged to determine a rough location estimate of the terminal on the basis of the measurement results, and that the base station comprises the means for using the rough estimate in locating the terminal.

15. A system as claimed in claim 11, wherein the base stations of the system which are closest to the terminal are arranged to measure the intensity and time delay of the signal received from the terminal, and that the base station is arranged to determine the rough location estimate of the terminal on the basis of the measurement results, and that the base station uses the rough estimate in locating the terminal.