Methods and apparatus for location determination based on dispersed radio frequency tags

• US 6,900,762 B2
• Filed: 09/30/2002
• Issued: 05/31/2005
• Est. Priority Date: 09/30/2002
• Status: Expired due to Term

• Current Assignee: Gemalto SA (Thales SA)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Thomson, David J., Lanzerotti, Louis J., Kochanski, Gregory P., Ho, Tin Kam, Andrews, Michael R.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Mull, Fred H.
• Application Number:
  US10/261,112
• Publication Number:
  US 20040061646A1
• Time in Patent Office: 974 Days
• Field of Search: 342/463, 342/464, 342/465, 342/387, 342/386
• US Class Current: 342/463
• CPC Class Codes: G01S 13/75 using transponders powered from received waves, e.g. using passive transponders , or using passive reflectors
• CPC Class Codes: G01S 2205/02 Indoor
• CPC Class Codes: G01S 5/0036 of measured values, i.e. measurement on mobile and position calculation on base station
• CPC Class Codes: G01S 5/0295 Proximity-based methods, e.g. position inferred from reception of particular signals

Abstract

Systems and techniques for location determination. A plurality of tags emitting radio frequency signals are dispersed throughout a region, such as a building, within which a user'"'"'s location is to be determined. The radio frequency signals emitted by the tags include information that can be used to identify the location in which the tags axe placed, or simply to distinguish the tags from one another. A portable device receives signals from the tags and provides the signal information to a location server that computes the location of the portable device by comparing the signal information received from the portable device to a map of location venus stored signal information, and identifies the location of the portable device as the location for which the stored signal information best matches the signal information received from the portable device.

Claims

1. A location identification system comprising:

a location server operative to store location identification information for each of a plurality of locations in a region, the location identification information comprising a location identifier and RF information characteristic of the location, the RF information comprising signals received at the location from ones of a plurality of RF tags distributed throughout the region, the tags being chosen and arranged such that the signals received from the tags can be used to reliably identify a location by distinguishing differences between times of transmissions of signals from said tags.

2. The location identification system of claim 1, wherein the RF information for each location is a location vector including tag identification information for each tag from which a signal is received and signal strength of each signal.

3. The location identification system of claim 1, further including a plurality of RF tags distributed throughout the region, each of the tags emitting a signal including tag identification information.

4. The location identification system of claim 3, wherein each tag emits a signal within a particular time slot of a plurality of available time slots and wherein the tag identification information includes identification of the signal emission as occurring within a particular time slot.

5. The location identification system of claim 4, wherein the location server is operative to receive a transmission indicating RF signals received by a portable device and to identify a location of the portable device by comparing RE information received by the portable device against RE information stored in association with the location identifiers.

6. The location identification system of claim 5, wherein the location server is operative to receive signal information from a wireless telephone used to make a call to an emergency call center, the signal information indicating RE information received by the wireless telephone from tags in the vicinity of the wireless telephone, the location server being operative to identify the location of the wireless telephone and to transmit the location of the wireless telephone to the emergency call center.

7. The location information system of claim 5, wherein the location server is at a location remote from the region where the tags are distributed and from the emergency call center and wherein the location server receives the signal information indicating the RF information received by the wireless telephone by remote transmission from the emergency call center.

8. A location identification system comprising:

a location server for receiving transmissions from a plurality of tags arranged in regions wherein locations are to be identified, each lag emitting an encoded signal identifying the location in which the tag is placed, the location server being operative to store each encoded signal emitted by a tag, the encoded signal including the location in which the tag is placed, wherein the encoded signals are divided into broader or narrower classes, with encoded signals in broader classes identifying larger regions and encoded signals in narrower classes identifying smaller regions within the larger regions, and wherein the location server associates a particular location with all encoded information defining the location, wherein the location server is further operative to receive a transmission from a portable device, the transmission representing encoded signals received by the portable device in order to allow the location server to identify the location of the portable device, and wherein the transmission from the portable device includes evaluation information for evaluating the encoded information received by the portable device, including the signal strength of a signal containing the encoded information, the time when the signal was received and the date when the tag emitting the signal was programmed with the encoded information and wherein the location server uses the evaluation information to determine which signals are to be used to identify the location of the portable device.

9. A method of location identification for a wireless device, comprising the steps of:

dispersing a plurality of radio frequency tags throughout a volume within which the location of the wireless device is to be identified, each tag emitting a signal including identifying information, the tags being chosen and arranged such that the signals received from the tap can be used to reliably identify a location by distinguishing differences between times of transmissions of signals from said tags;

mapping the signals emitted by the tags against locations within the volume; and

storing a map of locations to signal characteristics.

10. The method of claim 9, further comprising:

receiving signals emitted by the tags at a wireless device;

comparing signals emitted by the tags against the map of locations to signal characteristics; and

identifying the location of the wireless device as the location indicated by the map as the location wherein the signal characteristics most closely match those experienced by the wireless device.

11. The method of claim 10, wherein the step of receiving signals emitted by the tags at a wireless device includes sequentially receiving signals as the device moves in a path through the volume and wherein identifying the location of the wireless device includes identifying the location arrived at by following a path indicated by the sequentially received signals.

12. The method of claim 11, wherein the tags are one of passive resonators and tags that actively transmit location information.

13. The method of claim 11, wherein the stop of identifying the location of the user further comprises analyzing the sequence of tags in a manner that accounts for the possibility of one of the tags along the path being defective.

14. The method of claim 13, wherein the sequence of radiofrequency tag signals is received at a location distant from the user and wherein the step of compiling is responsive to receiving the sequence from the user.

15. The method of claim 9, comprising:

each tag emitting a signal including identifying information within a particular time slot of a plurality of available time slots, said tag identification information including identification of the signal emission as occurring within a particular time slot.

16. A program storage medium encoded with a computer executable program for performing stops of a method, the method comprising:

mapping signals emitted by a plurality of radiofrequency tags distributed throughout a region against locations within the region, the tags emitting signals including identifying information, the tags chosen and arranged so that the signals emitted by the tags may be used to reliably identify a location by distinguishing differences between times of transmissions of signals from said tags; and

storing a map of locations to signal characteristics.

17. The program storage medium of claim 16, wherein the method encoded onto the medium further comprises steps of receiving a transmission from a portable device indicating RF signals received by the portable device and comparing the RF signals received by the portable device against RF signals associated with each location in the map of locations and identifying the location of the portable device as the location associated with RF signals most closely matching the RF signals received by the portable device.

18. The program storage medium of claim 16, wherein the method encoded onto the medium further comprises steps of:

compiling a sequence of radiofrequency tag identification signals along a path traveled by the user carrying the wireless device; and

identifying the location of the user as the location arrived at by following a path defined by the sequence.

19. The program storage medium of claim 18, wherein the step of identifying the location of the user further comprises analyzing the sequence of tags in a manner that accounts for the possibility of one of the tags along the path being defective.

20. The program storage medium of claim 16, wherein the method encoded onto the medium further comprises:

each tag emitting a signal including identifying information within a particular time slot of a plurality of available time slots, said tag identification information including identification of the signal emission as occurring within a particular time slot.