Mobile positioning method for a portable communications device using shortened repetitive bursts

• US 6,243,588 B1
• Filed: 03/10/1998
• Issued: 06/05/2001
• Est. Priority Date: 03/10/1998
• Status: Expired due to Term

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Lundqvist, Patrick Nils, Koorapaty, Havish, Raith, Alex Krister
• Primary Examiner(s): Nguyen, Lee
• Assistant Examiner(s): SOBUTKA, PHILIP
• Application Number:
  US09/037,988
• Time in Patent Office: 1,183 Days
• Field of Search: 455/456, 455/457, 455/433, 455/524, 455/550, 455/566, 455/67.1, 455/67.4, 455/67.7, 455/115, 455/422, 342/457, 342/357.02, 370/252, 370/351
• US Class Current: 455/456.2
• 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

Standard mobile cellular telephones use shortened burst signal transmissions to synchronize the transmission of a call over a cellular telephone network. These shortened bursts as well as other traffic channel bursts can be used to locate the position of the cell phone. In operation, a primary base station sends a traffic channel designation message to a selected mobile phone which then initiates selected traffic channel burst transmissions, such as shortened bursts, over an interval of five seconds or less. The primary station and at least two other neighboring base stations receive these burst transmissions and determine their respective distances from the cell phone based upon the time of arrival of the bursts or some other suitable distance related measurement. A command center determines the location of the cell phone by triangulating the distance measurements of the base stations.

Claims

1. A method for detecting the position of a mobile communication unit in a communication system having a plurality of spatially dispersed base stations, the system using a shortened traffic channel burst transmission from the mobile unit, the method comprising the steps of:

a) transmitting shortened traffic channel burst signals from the mobile unit to a primary base station and a plurality of other neighboring base stations;

b) measuring a distance related characteristic of the shortened traffic channel burst signals from the mobile unit to said primary base station and said plurality of neighboring base stations;

c) detecting the accuracy of said measurements;

d) when the accuracy of said measurements is not acceptable, continuing steps a through c until an accurate measurement is achieved or a defined time has passed; and

e) when the accuracy of said measurements is acceptable, calculating the position of the mobile unit from said measurements.

2. The method of claim 1, wherein the requirement of locating a position is identified when said mobile unit sets up a call serviced by said primary base station.

3. The method of claim 1, wherein the requirement of locating a position is identified after a call is set up for the mobile unit by the primary base station.

4. The method of claim 1, wherein the system operates under IS-54.

5. The method of claim 1, wherein the system operates under IS-136, and further includes the step of sending the signal to the mobile unit that enables the unit to transmit a shortened traffic channel burst.

6. The method of claim 1, further including the step of said neighboring base stations and primary base station measuring the time of arrival of the bursts from the mobile unit.

7. The method of claim 1, further including the step of said neighboring base stations and primary base station measuring the time difference of arrival of the bursts from the mobile unit.

8. The method of claim 1, wherein said measurements are continued and are used to track the mobile unit.

9. A method for locating the position of a mobile communication unit in a mobile communications system that includes a plurality of base stations, the system using shortened burst transmissions on the traffic channel from the mobile unit to a primary base station and corresponding responsive time alignment signals from the primary base station that synchronize communications between the primary base station and the mobile unit, the method comprising the steps of:

selecting at least two neighboring base stations in the geographical vicinity of said mobile unit;

said neighboring base stations receiving said shortened bursts from said mobile unit;

using at least one signal of the shortened bursts to determine the distance of the primary and neighboring base stations from said mobile unit; and

calculating the location of the mobile unit from said distances.

10. The method of claim 9, including the further step of identifying the nature of the control channel used by the mobile unit as analog or digital, and in the event the channel is digital, setting the traffic channel designation to enable a shortened burst mode of operation by said mobile unit.

11. The method of claim 9, wherein the step of calculating the location of the mobile unit is accomplished at the primary base station.

12. The method of claim 9, wherein the requirement of locating the position of the mobile unit is identified when the mobile unit sets up a call serviced by said primary base station.

13. The method of claim 9, wherein the requirement of locating the position of the mobile unit is identified after a call is set up for the mobile unit by the primary base station.

14. The method of claim 9, wherein the system operates under IS-54.

15. The method of claim 9, wherein the system operates under IS-136, and further includes the step of sending a traffic channel designation message to the mobile unit that enables the unit to transmit said shortened burst.

16. The method of claim 9, further including the steps of measuring the time of arrival of the signals of said shortened bursts, and determining the distance based upon the time of arrival measurements.

17. The method of claim 9, further including the step of measuring the time difference of arrival of the signals of the shortened bursts between the mobile unit and the primary and neighboring base stations, and determining the distances between the mobile unit and these base stations based upon the time difference of arrival measurements.

18. The method of claim 9, wherein the distance measurements are continued and are used to track the mobile unit.

19. The method of claim 9, further including the steps of:

combining measures of distance derived from shortened burst transmissions and terminating the combining if the measures of distance are not found to be sufficiently accurate after a defined time;

aligning and synchronizing a time slot of the mobile communication unit;

generating voice burst signals by the mobile communication unit;

deriving from at least one voice burst signal received by each of a plurality of base stations a measure of the distance of the mobile communication unit from the base stations; and

determining the location of said mobile communication unit from sufficiently accurate measures of distance for at least one signal of the voice burst.

20. The method of claim 9, further including the step of evaluating the accuracy of the distance measurements and calculating the location of the mobile unit only after the measurements have been determined to be sufficiently accurate.

21. The method of claim 20, further comprising the steps of:

aligning the time slot of the mobile unit if sufficient accuracy of the distance measurements for shortened burst signals is not achieved within a set time;

generating voice bursts by the mobile unit; and

calculating the location of the mobile unit from sufficiently accurate distance measurements for at least one of said voice bursts.

22. The method of claim 20, further including the step of initiating the transmission of shortened bursts from the mobile unit if the distance measurements derived from the voice bursts are not sufficiently accurate.

23. A method for locating the position of a mobile communication device that operates with a network of spatially disposed base stations, the method comprising the steps of:

using the network to cause the mobile communication device to transmit voice burst signals suitable for deriving position information;

receiving said voice burst signals at a plurality of said base stations;

deriving from at least one voice burst signal received by each base station a measure of the distance of the mobile communication device from the base station;

combining a plurality of said measures of distance;

determining the accuracy of the combined measure of distance based on a standard deviation derived from previous combined measures of distance;

terminating the combining of the measures of distance if the measures of distance are not found to be sufficiently accurate after a defined time;

determining the location of said mobile communication device from the combination of sufficiently accurate measures of distance for at least one signal of the voice burst; and

aligning and synchronizing a time slot of the mobile communication device.

24. The method of claim 23, wherein said step of deriving includes detecting the time of arrival of said at least one burst signal and said step of determining includes using the times of arrival for at least three base stations to solve at least three equations for the x, y spatial coordinates of said mobile communication device.

25. The method of claim 23, wherein said step of deriving includes detecting the time difference of arrival of said at least one burst signal with respect to at least three base stations, and said step of determining includes using these time difference of arrival measurements to solve at least three equations for the x,y spatial coordinates of said mobile communication device.

26. The method of claim 23, wherein said step of transmitting includes transmitting shortened burst signals from said mobile communication device.

27. The method of claim 23, wherein said measure of distance is the time of arrival of at least one signal of the burst at each one of a plurality of said base stations.

28. The method of claim 23, wherein said measure of distance is the time difference of arrival of at least one signal of the burst at a plurality of base stations.

29. The method of claim 23, further including the step of initiating the transmission of shortened bursts from the mobile communication device if the measures of distance derived from the voice bursts are not sufficiently accurate.

30. The method of claim 23, wherein said network operates in accordance with IS-54.

31. The method of claim 23, wherein said network operates in accordance with IS-136, and further includes the step of sending a traffic channel designation message to the mobile communication device that enables the device to transmit a shortened voice channel burst.

32. The method of claim 23, wherein the measurements of distance are continued and are used to track the mobile communication device.

33. The method of claim 23, further including the step of using the angle of arrival of the burst signals at said base stations to calculate the location of the mobile device.

34. The method of claim 23, further including the step of eliminating possible locations of the mobile communication device based upon known geographical characteristics of a possible location.

35. A method for locating the position of a mobile communication unit in a mobile communications system that includes a plurality of base stations, the system using shortened burst transmissions on the traffic channel from the mobile unit to a primary base station and corresponding responsive time alignment signals from the primary base station that synchronize communications between the primary base station and the mobile unit, the method comprising the steps of:

selecting at least two neighboring base stations in the geographical vicinity of said mobile unit;

said neighboring base stations receiving said shortened bursts from said mobile unit;

using at least one signal of the shortened bursts to determine the distances of the primary and neighboring base stations from said mobile unit;

evaluating the accuracy of the distance measurements;

aligning a time slot of the mobile unit if sufficient accuracy of the distance measurements for shortened burst signals is not achieved within a set time; and

calculating the location of the mobile unit from sufficiently accurate distance measurements for at least one of said bursts.

36. The method of claim 35, further including the step of initiating the transmission of voice bursts from the mobile unit if the distance measurements derived from the shortened bursts are not sufficiently accurate.

37. A method for locating the position of a mobile communication device that operates with a network of spatially disposed base stations, the method comprising the steps of:

using the network to cause the mobile communication device to transmit voice burst signals suitable for deriving position information;

receiving said voice burst signals at a plurality of said base stations;

deriving from at least one voice burst signal received by each base station a measure of the distance of the mobile communication device from the base station;

combining a plurality of said measures of distance;

terminating the combining of the measures of distance if the measures of distance are not found to be sufficiently accurate after a defined time;

determining the location of said mobile communication device from the combination of sufficiently accurate measures of distance for at least one signal of the voice burst;

aligning and synchronizing a time slot of the mobile communication device; and

initiating the transmission of shortened bursts from the mobile communications device if the measures of distance derived from the voice bursts are not sufficiently accurate.