Method and apparatus for mobile station geographical location determination

• US 6,122,512 A
• Filed: 09/30/1997
• Issued: 09/19/2000
• Est. Priority Date: 09/30/1996
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Bodin, Stig Roland
• Primary Examiner(s): Trost, William G.
• Assistant Examiner(s): WASHINGTON, ERIKA ALISE
• Application Number:
  US08/940,840
• Time in Patent Office: 1,085 Days
• Field of Search: 455/440, 455/456, 455/560, 455/561, 455/524, 455/525, 455/436, 455/437, 455/438, 455/439
• US Class Current: 455/440
• CPC Class Codes: G01S 2205/008 using a mobile telephone network
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

In a cellular mobile telecommunication system, particularly a Global System for Mobile Communications (GSM) system, a method and apparatus determine the geographical position of a mobile station. The distance between the mobile station and a radio base station is estimated from the propagation delay. The propagation delay is determined according to the present method when the mobile station sends access bursts to the base station, which measures the access delay of the arrived bursts in the same way as an ordinary handover. However, no confirmation of received access bursts is sent from the base station to the mobile station and therefore the handover attempt is terminated. The connection between the mobile station and the previous base station is re-established. The measured access delay is proportional to the propagation delay and thereby also to the distance to the mobile station. The mobile position can be determined with good accuracy if values from at least three base stations are obtained, although with less accuracy if only two values are obtained. Also, an access delay measured by earlier known methods can be used together with measurements achieved with the present method to determine the mobile position.

Claims

1. A method of determining the position of a mobile station in a TDMA-type mobile radio system, which includes at least one base station controller with associated radio base transceiver stations and at least one mobile radio switching center, wherein while connected to a given first base station the mobile station continuously evaluates the radio connections from a first plurality of base stations, and wherein said first plurality of base stations are placed in ranking order and inserted in a ranking list, the method comprising the steps of:

a) designating a second plurality of base stations from said first plurality of base stations from said list;

b) ordering the mobile station to handover to a designated second base station among said second plurality of base stations;

c) initiating a handover from the mobile station to said designated second base station by sending an access signal to said designated second base station;

d) in the same way as with handover, at said designated second base station,

measuring and recording a first time delay upon the arrival of the access signal relative to the arrival time expected at said designated second base station if the mobile station were located in the same place as said designated second base station;

e) inhibiting confirmation of the access signal received from the mobile station by said designated second base station;

f) evaluating the recorded first time delay; and

g) repeating the commands and measuring procedures according to steps b)-f) in at least one additional base station selected from said second plurality of base stations; and

wherein after there is obtained at least one additional time delay, the recorded first time delay along with the at least one additional time delay can be used to calculate the position of the mobile station.

2. A method according to claim 1, further comprising the step of:

carrying out steps b)-f) in at least one base station selected from said second plurality of base stations in a); and

wherein the time delay obtained from said at least one base station is used together with another time delay measured by an earlier known method in said given first base station to determine the position of the mobile station.

3. A method according to claim 2, wherein:

at least three time delays are obtained for the purpose of calculating the position of the mobile station.

4. A method according to claim 2, wherein:

the mobile radio system is a GSM-system.

5. A method according to claim 1, wherein:

at least three time delays are obtained for the purpose of calculating the position of the mobile station.

6. A method according to claim 1, wherein:

the mobile radio system is a GSM-system.

7. A method according to claim 1, further comprising the step of:

during an established connection with said given first base station,

measuring, by the mobile station, a time reference for each of the base stations of said first plurality of base stations recorded in said list, said time reference and an order number of a designated time slot determining a point in time at which the access signal is sent from the mobile station to said designated second base station.

8. A method according to claim 1, further comprising the step of:

in said designated second base station,

receiving a mobile position determining command which includes a modified version of the channel activity command, whereupon said designated second base station inhibits confirmation of the receipt of the access signal from the mobile station.

9. A modified radio base transceiver station, which effects measuring and registration of an access signal arrival time in the same manner as with typical handover so as to enable the position of a mobile station that has sent the access signal in a mobile radio system of the TDMA-type to be calculated, said mobile radio system including at least one base station controller with associated radio base transceiver stations and at least one mobile radio switching center, wherein during an established connection with a given first base transceiver station said mobile station continuously evaluates the radio connections from a plurality of base transceiver stations, and wherein said plurality of base transceiver stations are placed in ranking order in a list, said modified radio base transceiver station comprising:

a memory space in which there is stored a mobile position determining command;

means for comparing said mobile position determining command with commands received from said at least one base station controller to thereby identify a command concerning the determination of the position of said mobile station;

means for inhibiting confirmation of an access signal obtained from said mobile station if said command concerning the determination of the position of said mobile station is identified;

a further memory space capable of storing a flag; and

wherein the flag is enabled when the mobile position determining command is received from the base station controller; and

wherein the flag is checked during the handover procedure so as to inhibit confirmation of the access signal received from the mobile station in the event of the flag being enabled.

10. A modified radio base transceiver station according to claim 9, wherein:

said radio base transceiver station comports with the GSM-system specification.

11. A modified radio base transceiver station, which effects measuring and registration of an access signal arrival time in the same manner as with typical handover so as to enable the position of a mobile station that has sent the access signal in a mobile radio system of the TDMA-type to be calculated, said mobile radio system including at least one base station controller with associated radio base transceiver stations and at least one mobile radio switching center, wherein during an established connection with a given first base transceiver station said mobile station continuously evaluates the radio connections from a plurality of base transceiver stations, and wherein said plurality of base transceiver stations are placed in ranking order in a list, said modified radio base transceiver station comprising:

a memory space in which there is stored a mobile position determining command;

means for comparing said mobile position determining command with commands received from said at least one base station controller to thereby identify a command concerning the determination of the position of said mobile station;

means for inhibiting confirmation of an access signal obtained from said mobile station if said command concerning the determination of the position of said mobile station is identified;

a further memory space in which a program loop is stored; and

wherein the program loop is executed when a mobile position determining command is received from the base station controller; and

wherein the station measures the access signal received from the mobile station in manner typical with handover, but inhibits confirmation of said receipt to the mobile station.

12. A modified radio base transceiver station according to claim 11, wherein:

said radio base transceiver station comports with the GSM-system specification.

13. An electronically-executable command or program in a computer-accessible memory or on a computer-readable medium, said command or program adapted for interacting with a radio communications system, said command or program comprising:

means for participating in the initiation of a handover process;

means for ascertaining a propagation delay with respect to a transmission from an element of the radio communications system, said element participating in the initiation of said handover process; and

means for intentionally failing to complete said handover process.

14. An electronically-executable command or program according to claim 13, further comprising:

means for receiving and interpreting a mobile position determining command.

15. A base transceiver station in a radio communications system, said base transceiver station adapted for interacting with a mobile station to participate in a geographical location determination, said base transceiver station comprising:

means for beginning a handover process;

means for ascertaining a propagation delay; and

means for terminating said handover process by failing to respond to an access signal from said mobile station.

16. An electronically-executable command or program according to claim 15, further comprising:

means for receiving and interpreting a mobile position determining command.

17. A method in a base transceiver station in a radio communications system, said base transceiver station adapted for interacting with a mobile station to participate in a geographical location determination, the method comprising the steps of:

beginning a handover process;

ascertaining a propagation delay; and

terminating said handover process by failing to respond to an access signal from said mobile station.

18. A base transceiver station according to claim 17, further comprising:

means for receiving and properly interpreting a mobile position determining command.