Collision recovery in a wireless location system

• US 6,563,460 B2
• Filed: 12/05/2001
• Issued: 05/13/2003
• Est. Priority Date: 01/08/1999
• Status: Expired due to Term

• Current Assignee: Skyhook Holding, Inc. (Liberty Broadband Corp.), Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology, TruePosition Incorporated
• Inventors: Sheehan, Joseph W., Rogers, Alan E. E., Anderson, Robert J., Stilp, Louis A.
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US10/005,068
• Publication Number:
  US 20020080069A1
• Time in Patent Office: 524 Days
• Field of Search: 342/450, 342/456, 342/457, 342/463, 455/456
• US Class Current: 342/457
• CPC Class Codes: G01S 1/026 of associated receivers
• CPC Class Codes: G01S 2205/006 for emergency situations
• CPC Class Codes: G01S 2205/008 using a mobile telephone network
• CPC Class Codes: G01S 2205/06 Emergency
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0215 Interference
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/02216 Timing or synchronisation of the receivers
• CPC Class Codes: G01S 5/0244 Accuracy or reliability of position solution or of measurements contributing thereto
• CPC Class Codes: G01S 5/0246 involving frequency difference of arrival or Doppler measurements G01S5/02685 takes precedence
• CPC Class Codes: G01S 5/02521 using a radio-map
• CPC Class Codes: G01S 5/0268 by deriving positions from different combinations of signals or of estimated positions in a single positioning system
• CPC Class Codes: G01S 5/0284 Relative positioning
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: H04W 4/90 Services for handling of emergency or hazardous situations, e.g. earthquake and tsunami warning systems [ETWS]
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H04W 76/50 for emergency connections
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A collision recovery method for use in a Wireless Location System includes receiving a transmission from a wireless transmitter at multiple signal collection systems and multiple antenna ports of each of the multiple signal collection systems. At each of the multiple signal collection systems, the transmission received at each antenna port is converted into a digital format, and digital data representative of the received transmission is stored. The transmission is then demodulated, and TDOA analysis is performed on the digital data from pairs of signal collection systems. The location of the wireless transmitter is determined using the TDOA data. The method further involves verifying that the RF data from each antenna port is from the wireless transmitter to be located, e.g., by demodulating a segment of the transmission received at each antenna port and verifying that at least a combination of the following fields is correct: MIN, MSID, TMSI, IMSI, and ESN.

Claims

1. A collision recovery method for use in a wireless location system, comprising:

receiving a transmission from a mobile wireless transmitter at multiple signal collection systems and multiple antenna ports of each of said multiple signal collection systems, said signal collection systems being at known, fixed locations;

at each of said multiple signal collection systems, storing digital RF data representative of the received transmission; and

verifying that the RF data from each antenna port is from the wireless transmitter to be located.

2. A method as recited in claim 1, wherein the verifying step is accomplished by demodulating a segment of the transmission received at each antenna port and verifying that a combination of the following fields is correct:

MIN, MSID, TMSI, IMSI, and ESN.

3. A method as recited in claim 1, wherein the verifying step is accomplished by demodulating a segment of the transmission received at each antenna port and verifying that at least the MIN is correct.

4. A method as recited in claim 1, wherein the verifying step is accomplished by demodulating a segment of the transmission received at each antenna port and verifying that at least the MSID is correct.

5. A method as recited in claim 1, wherein the verifying step is accomplished by demodulating a segment of the transmission received at each antenna port and verifying that at least the TMSI is correct.

6. A method as recited in claim 1, wherein the verifying step is accomplished by demodulating a segment of the transmission received at each antenna port and verifying that at least the IMSI is correct.

7. A method as recited in claim 1, wherein the verifying step is accomplished by demodulating a segment of the transmission received at each antenna port and verifying that at least the ESN is correct.

8. A method as recited in claim 1, wherein the wireless location system also correlates a short segment of the received signal at an antenna port with the signal received at a reference or primary signal collection system and verifying that at least the correlation result is above a predetermined threshold.

9. A method as recited in claim 1, wherein the wireless location system also correlates a short segment of the received signal at an antenna port with the signal received at a reference signal collection system and verifying that at least the correlation result is above a predetermined threshold.

10. A method as recited in claim 1, wherein the wireless location system also correlates a short segment of the received signal at an antenna port with the signal received at a primary signal collection system and verifying that at least the correlation result is above a predetermined threshold.

11. A method as recited in claim 1, wherein the SNR of the transmission is measured and, if the variance over the entire length of the transmission is above a predetermined threshold, the transmission is divided into segments and each segment is tested to determine whether the energy in that segment is primarily from the transmission from the wireless transmitter for which location processing has been selected.

12. A method as recited in claim 1, wherein, if the wireless location system has detected that a partial collision has occurred at a signal collection system/antenna, the signal collection system identifies those segments of the received transmission that represent a signal from the wireless transmitter for which location processing has been selected, and those segments of the received transmission which contain co-channel interference.

13. A method as recited in claim 12, wherein the wireless location system commands the signal collection system to send only selected segments of the received transmission that do not contain the co-channel interference.

14. A method as recited in claim 12, wherein the wireless location system commands the signal collection system to use only selected segments of the received transmission that do not contain the co-channel interference.

15. A method as recited in claim 1, wherein, when determining TDOA and/or FDOA for a baseline using only selected segments from a signal collection system/antenna, the wireless location system uses only the corresponding segments of the transmission as received at a reference signal collection system.

16. A method as recited in claim 1, wherein, when determining TDOA and/or FDOA for a baseline using only selected segments from a signal collection system/antenna, the wireless location system uses only the corresponding segments of the transmission as received at a reference antenna.

17. A collision recovery method for use in a wireless location system that determines the geographic location of a mobile wireless transmitter, wherein the wireless location system performs the following acts in locating the wireless transmitter:

receiving a transmission from the wireless transmitter at multiple signal collection systems and multiple antenna ports of each of said multiple signal collection systems;

at each of said multiple signal collection systems, converting the transmission received at each antenna port into digital RF data;

at each of said multiple signal collection systems, storing digital data representative of the received transmission;

demodulating the transmission;

performing TDOA analysis on the digital data from pairs of signal collection systems, whereby TDOA data is provided; and

determining the location of the wireless transmitter using the TDOA data;

wherein the method further comprises verifying that the RF data from each antenna port is from the wireless transmitter to be located.

18. A method as recited in claim 17, wherein the verifying step is accomplished by demodulating a segment of the transmission received at each antenna port and verifying that at least a combination of the following fields is correct:

MIN, MSID, TMSI, IMSI, and ESN.

19. A method as recited in claim 17, wherein the verifying step is accomplished by demodulating a segment of the transmission received at each antenna port and verifying that at least the MIN is correct.

20. A method as recited in claim 17, wherein the verifying step is accomplished by demodulating a segment of the transmission received at each antenna port and verifying that at least the MSID is correct.

21. A method as recited in claim 17, wherein the verifying step is accomplished by demodulating a segment of the transmission received at each antenna port and verifying that at least the TMSI is correct.

22. A method as recited in claim 17, wherein the verifying step is accomplished by demodulating a segment of the transmission received at each antenna port and verifying that at least the IMSI is correct.

23. A method as recited in claim 17, wherein the verifying step is accomplished by demodulating a segment of the transmission received at each antenna port and verifying that at least the ESN is correct.

24. A method as recited in claim 17, wherein the wireless location system also correlates a short segment of the received signal at an antenna port with the signal received at a reference or primary signal collection system and verifying that at least the correlation result is above a predetermined threshold.

25. A method as recited in claim 17, wherein the wireless location system also correlates a short segment of the received signal at an antenna port with the signal received at a reference signal collection system and verifying that at least the correlation result is above a predetermined threshold.

26. A method as recited in claim 17, wherein the wireless location system also correlates a short segment of the received signal at an antenna port with the signal received at a primary signal collection system and verifying that at least the correlation result is above a predetermined threshold.

27. A method as recited in claim 17, wherein the SNR of the transmission is measured and, if the variance over the entire length of the transmission is above a pre-determined threshold, the transmission is divided into segments and each segment is tested to determine whether the energy in that segment is primarily from the transmission from the wireless transmitter for which location processing has been selected.

28. A method as recited in claim 17, wherein, if the wireless location system has detected that a partial collision has occurred at a signal collection system/antenna, the signal collection system identifies those segments of the received transmission that represents a signal from the wireless transmitter for which location processing has been selected, and those segments of the received transmission which contains co-channel interference.

29. A method as recited in claim 28, wherein the wireless location system commands the signal collection system to send only selected segments of the received transmission that do not contain the co-channel interference.

30. A method as recited in claim 28, wherein the wireless location system commands the signal collection system to use only selected segments of the received transmission that do not contain the co-channel interference.

31. A method as recited in claim 17, wherein, when determining TDOA and/or FDOA for a baseline using only selected segments from a signal collection system/antenna, the wireless location system uses only the corresponding segments of the transmission as received at a reference signal collection system.

32. A method as recited in claim 17, wherein, when determining TDOA and/or FDOA for a baseline using only selected segments from a signal collection system/antenna, the wireless location system uses only the corresponding segments of the transmission as received at a reference antenna.

33. An apparatus for use in a wireless location system, comprising:

means for receiving a transmission from a mobile wireless transmitter at multiple signal collection systems and multiple antenna ports of each of said multiple signal collection systems, said signal collection systems being at known, fixed locations;

means for storing digital RF data representative of the received transmission at each of said multiple signal collection systems; and

means for verifying that the RF data from each antenna port is from the wireless transmitter to be located.

34. An apparatus as recited in claim 33, wherein the means for verifying demodulates a short segment of the transmission received at each antenna port and verifying that at least combination of the following fields is correct:

MIN, MSID, TMSI, IMSI, and ESN.

35. An apparatus as recited in claim 33, wherein the means for verifying demodulates a short segment of the transmission received at each antenna port and verifying that at least the MIN is correct.

36. An apparatus as recited in claim 33, wherein the means for verifying demodulates a short segment of the transmission received at each antenna port and verifying that at least the MSID is correct.

37. An apparatus as recited in claim 33, wherein the means for verifying demodulates a short segment of the transmission received at each antenna port and verifying that at least the TMSI is correct.

38. An apparatus as recited in claim 33, wherein the means for verifying demodulates a short segment of the transmission received at each antenna port and verifying that at least the IMSI is correct.

39. An apparatus as recited in claim 33, wherein the means for verifying demodulates a short segment of the transmission received at each antenna port and verifying that at least the ESN is correct.

40. An apparatus as recited in claim 33, wherein the wireless location system also correlates a short segment of the received signal at an antenna port wi th the signal received at a reference or primary signal collection system and verifying that at least the correlation result is above a predetermined threshold.

41. An apparatus as recited in claim 33, wherein the wireless location system also correlates a short segment of the received signal at an antenna port with the signal received at a reference signal collection system and verifying that at least the correlation result is above a predetermined threshold.

42. An apparatus as recited in claim 33, wherein the wireless location system also correlates a short segment of the received signal at an antenna port with the signal received at a primary signal collection system and verifying that at least the correlation result is above a predetermined threshold.

43. An apparatus as recited in claim 33, wherein the SNR of the transmission is measured and, if the variance over the entire length of the transmission is above a pre-determined threshold, the transmission is divided into segments and each segment is tested to determine whether the energy in that segment is primarily from the transmission from the wireless transmitter for which location processing has been selected.

44. (Amended) An apparatus as recited in claim 33, wherein, if the wireless location system has detected that a partial collision has occurred at a signal collection system/antenna, the signal collection system identifies those segments of the received transmission that represent a signal from the wireless transmitter for which location processing has been selected, and those segments of the received transmission which contain co-channel interference.

45. An apparatus as recited in claim 33, wherein the wireless location system commands the signal collection system to send only selected segments of the received transmission that do not contain the co-channel interference.

46. An apparatus as recited in claim 33, wherein the wireless location system commands the signal collection system to use only selected segments of the received transmission that do not contain the co-channel interference.

47. An apparatus as recited in claim 33, wherein, when determining TDOA and/or FDOA for a baseline using only selected segments from a signal collection system/antenna, the wireless location system uses only the corresponding segments of the transmission as received at a reference signal collection system.

48. An apparatus as recited in claim 33, wherein, when determining TDOA and/or FDOA for a baseline using only selected segments from a signal collection system/antenna, the wireless location system uses only the corresponding segments of the transmission as received at a reference antenna.