Pseudolite-augmented GPS for locating wireless telephones

• US 6,771,625 B1
• Filed: 07/10/2000
• Issued: 08/03/2004
• Est. Priority Date: 07/10/1997
• Status: Expired due to Term

• Current Assignee: Skyhook Holding, Inc. (Liberty Broadband Corp.)
• Original Assignee: KSI Inc. (Liberty Broadband Corp.)
• Inventors: Beal, Robert E.
• Primary Examiner(s): LEE, CHI HO A
• Application Number:
  US09/612,920
• Time in Patent Office: 1,485 Days
• Field of Search: 370/316, 370/314, 370/326, 370/321, 370/335, 370/336, 370/337, 370/342, 370/347, 455/457, 455/524, 455/561, 455/575, 342/357.01, 342/357.02, 342/357.06, 342/357.09
• US Class Current: 370/336
• CPC Class Codes: G01S 19/10 providing dedicated supplementary positioning signals
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type
• CPC Class Codes: G01S 5/0027 of actual mobile position, i.e. position determined on mobile
• CPC Class Codes: G01S 5/0045 Transmission from base station to mobile station G01S5/009 takes precedence
• CPC Class Codes: G01S 5/145 Using a supplementary range measurement, e.g. based on pseudo-range measurements
• CPC Class Codes: H04B 7/18552 using a telephonic control signal and a second ranging satellite determining absolute distances from a plurality of spaced points of known location G01S5/14

Abstract

Ground-based pseudolites support accurate determination of mobile receiver locations by broadcasting CDMA signals interleaved by a TDMA system. Pseudolites synchronize signal transmissions with an accurate timing reference, such as can be derived from GPS satellites. Adjacent pseudolites broadcast CDMA signals at different times, eliminating near-far signal interference between pseudolites. A mobile receiver, typically a cellular telephone, receives and enables determination of times of arrival (TOA) of the pseudolite signals. A location processor associated with the mobile receiver may access an internal database of pseudolite locations, or pseudolite location information may be encoded in pseudolite transmissions. The location processor uses pseudolite location information and TOA to determine mobile receiver location. The TDMA pseudolite-based system may augment the GPS to provide more accurate location information than is available from the GPS alone.

Claims

1. A geolocation system for augmenting the Global Positioning System with a network of pseudolites, comprising:

at least three binary code signal sources wherein at least one of said binary code signal sources is a pseudolite capable of transmitting binary code signals on at least one radio frequency not used by the Global Positioning System, said pseudolite transmitting binary code signals according to a time division multiplexing system, said binary code signals being receivable by a mobile receiver whose location is to be determined; and

means for interleaving the binary code signals of said binary code signal sources wherein a different binary code signal broadcast slot is assigned to each of said binary code signal sources.

2. A geolocation system as claimed in claim 1, further comprising a mobile receiver including a signal time processor capable of determining the arrival times of binary code signals at the mobile receiver, and a location processor capable of determining the location of the mobile receiver from binary code signal arrival times and binary code signal source location information.

3. A geolocation system as claimed in claim 2 wherein the signal time processor and location processor are embedded in the mobile receiver.

4. A geolocation system of the type recited in claim 1, further comprising a mobile receiver, the mobile receiver being capable of receiving the binary code signals and comprising a signal time processor capable of determining the arrival times of the binary code signals at the mobile receiver, and a location processor capable of determining the location of the mobile receiver from binary code signal arrival times and binary code signal source location information.

5. A geolocation system as claimed in claim 1 wherein at least a second of the at least three binary code signal sources is a satellite of the Global Positioning System.

6. A geolocation system as claimed in claim 1 wherein at least one pseudolite is chronologically synchronized with a satellite of the Global Positioning System.

7. A geolocation system as claimed in claim 1 wherein each of the binary code signal sources is a pseudolite.

8. A geolocation system as claimed in claim 1 wherein the binary code signal sources comprise at least one pseudolite and at least one satellite of the Global Positioning System.

9. A geolocation system as claimed in claim 2 wherein the location processor further comprises data indicative of pseudolite locations.

10. A geolocation system as claimed in claim 2 wherein the binary code signals include location information.

11. A geolocation system as claimed in claim 10 wherein the location information includes the location of the pseudolite.

12. A geolocation system as claimed in claim 10 wherein the location information includes an identification number for the pseudolite.

13. A geolocation system as claimed in claim 10 wherein the location information includes at least one pseudolite identification number, and the location processor includes an index to a database having an index of the pseudolite accessible by the location processor.

14. A geolocation system as claimed in claim 1 wherein the pseudolite reduces binary code signal attenuation by transmitting the binary code signals at higher power levels than binary code signals transmitted by satellites of the Global Positioning System.

15. A geolocation system as claimed in claim 1 wherein the pseudolite simultaneously transmits more than one binary code transmission sequence on a single frequency.

16. A geolocation system as claimed in claim 1 wherein the pseudolite transmits pseudo-random noise on a first frequency and location information on a second frequency.

17. A geolocation system as claimed in claim 1 wherein the pseudolite encodes and transmits location information in a bit stream comprising pseudo-random noise.

18. A geolocation system as claimed in claim 1 wherein the pseudolite transmits pseudo-random noise in a first binary code sequence and location information in a second binary code sequence.

19. A geolocation system as claimed in claim 10 wherein the location information comprises latitude and longitude information.

20. A geolocation system as claimed in claim 10 wherein the location information comprises a grid reference.

21. A geolocation system as claimed in claim 10 wherein the location information comprises latitude, longitude, and elevation information.

22. A geolocation system as claimed in claim 10, further comprising a telephone device coupled with said mobile Global Positioning System receiver, the telephone device transmitting the location information.

23. A geolocation system as claimed in claim 2, further comprising a mobile transmitter for transmitting the location of the mobile receiver to a remote location.

24. A method for locating a wireless telephone by augmenting the Global Positioning System with a network of pseudolites, comprising the steps of:

transmitting binary code signals from at least three binary code signal sources, at least one binary code signal being transmitted from a pseudolite on a radio frequency not used by the Global Positioning System;

interleaving the binary code signals of said binary code signal sources so as to assign a different binary code signal broadcast time for each of said binary code signal sources;

receiving the binary code signals with a mobile receiver;

determining the times the binary code signal sources transmitted the binary code signals;

determining the times the mobile receiver received the binary code signals; and

determining the location of the mobile receiver from each binary code signal time of transmission and time of arrival, and from binary code signal source location information.

25. A method for locating a wireless telephone as claimed in claim 24, comprising the additional step of chronologically synchronizing at least one pseudolite with a Global Positioning System satellite.

26. A method for locating a wireless telephone as claimed in claim 24 wherein at least one of the binary code signal sources is a Global Positioning System satellite.

27. A method for locating a wireless telephone as claimed in claim 24 wherein all of the binary code signal sources are pseudolites.

28. A method for locating a wireless telephone as claimed in claim 24 wherein the binary code signal sources comprise the at least one pseudolite and at least one satellite of the Global Positioning System.

29. A method for locating a wireless telephone as claimed in claim 24, comprising the additional step of transmitting binary code signals from the pseudolite at power levels higher than binary code signals transmitted by satellites of the Global Positioning System.

30. A method for locating a wireless telephone as claimed in claim 24 wherein the pseudolite simultaneously transmits more than one binary code sequence on a single frequency.

31. A method for locating a wireless telephone as claimed in claim 24 wherein the step of determining the location of the mobile receiver includes the step of accessing a database containing pseudolite location information.

32. A method for locating a wireless telephone as claimed in claim 24 wherein the binary code signals include location information.

33. A method for locating a wireless telephone as claimed in claim 32 wherein the step of determining the location of the mobile receiver includes the step of extracting the location information.

34. A method for locating a wireless telephone as claimed in claim 32 wherein the location information includes a location of the one pseudolite.

35. A method for locating a wireless telephone as claimed in claim 32 wherein the location information includes a pseudolite identification number correlating to an index in a database containing pseudolite locations.

36. A method for locating a wireless telephone as claimed in claim 32 wherein the location information includes at least one pseudolite identification number.

37. A method for locating a wireless telephone as claimed in claim 32, further comprising the pseudolite transmitting pseudo-random noise on a first frequency and the location information on a second frequency.

38. A method for locating a wireless telephone as claimed in claim 32, further comprising the pseudolite encoding and transmitting the location information in a bit stream comprising pseudo-random noise.

39. A method for locating a wireless telephone as claimed in claim 32, further comprising the pseudolite transmitting pseudo-random noise in a first binary code sequence and the location information in a second binary code sequence.

40. A method for locating a wireless telephone as claimed in claim 32 wherein the location information comprises latitude and longitude information.

41. A method for locating a wireless telephone as claimed in claim 32 wherein the location information comprises a grid reference information.

42. A method for locating a wireless telephone as claimed in claim 32 wherein the location information comprises latitude, longitude, and elevation information.

43. A method for locating a wireless telephone as claimed in claim 32, further comprising transmitting location information when a telephone device coupled with said mobile Global Positioning System receiver transmits a signal.

44. A method for locating a wireless telephone as claimed in claim 24, further comprising transmitting the location of the mobile Global Positioning System receiver from the mobile receiver.