Providing global positioning system timing signals to remote cellular base stations

• US 20060067451A1
• Filed: 09/30/2004
• Published: 03/30/2006
• Est. Priority Date: 09/30/2004
• Status: Active Grant

• Current Assignee: Ericsson Evdo, Inc. (CommScope Holding Company, Inc.)
• Original Assignee: Airvana Incorporated (CommScope Holding Company, Inc.)
• Inventors: Pollman, Michael D., Grosch, Theodore O.
• Granted Patent: US 7,558,356 B2
• Time in Patent Office: Days
• US Class Current: 375/367
• CPC Class Codes: H04L 7/043 Pseudo-noise [PN] codes variable during transmission synchronisation of spread spectrum receivers H04B1/69
• CPC Class Codes: H04L 7/08 the synchronisation signals recurring cyclically

Abstract

In a cellular network, a GPS receiver includes circuitry that modulates a global positioning system (GPS) timing pulse signal with a carrier signal and transmits the modulated signal to one or more remote base stations. When the modulated timing pulse signal is received at a remote base station it is demodulated and a timing pulse signal corresponding to the GPS timing pulse signal is recovered. The remote base station may be configured to transmit a reply signal back to the GPS receiver, which can then be used to estimate a propagation delay between the GPS receiver and the remote base station.

Claims

1. A method comprising:

generating a oscillating signal and a timing pulse signal having a fixed frequency from received global positioning system signals at a first location;

modulating the oscillating signal with the timing pulse signal; and

transmitting the modulated signal to a device located at a second location through a communications channel.

2. The method of claim 1 wherein modulating the oscillating signal with the timing pulse signal comprises:

using the oscillating signal to generate a pseudorandom noise code of symbols that repeats over time at a frequency of no greater than the fixed frequency of the timing pulse signal, wherein for each instance of the pseudorandom noise code of symbols, the occurrence of a pulse in the timing pulse signal is aligned with a predetermined position of one of the symbols in the code.

3. The method of claim 2 wherein the predetermined position is the same symbol position for each instance of the pseudorandom noise code of symbols.

4. The method of claim 2 wherein the predetermined position is the first symbol position for each instance of the pseudorandom noise code of symbols.

5. The method of claim 1 wherein the pseudorandom noise code of symbols has a period less than the period of the timing pulse signal, the method further comprising:

adding bits to each instance of the pseudorandom noise code of symbols such that the resulting signal has a period approximately equal to the period of the timing pulse signal.

6. The method of claim 5 wherein the additional bits carry no information.

7. The method of claim 5 wherein the additional bits comprise bits representing messaging information.

8. The method of claim 1 further comprising:

generating a time-of-day message from the received global positioning system signals.

9. The method of claim 5 wherein the additional bits comprise bits representing the time-of-day message.

10. The method of claim 2 wherein modulating the oscillating signal with the timing pulse signal further comprises:

mixing message data with the generated pseudorandom noise code.

11. The method of claim 1 further comprising:

receiving the modulated signal at the second location; and

deriving the oscillating signal and timing pulse signal from the received modulated signal.

12. The method of claim 2 further comprising:

receiving the modulated signal at the second location; and

driving an oscillator at the second location with the received signal to derive the oscillator signal.

13. The method of claim 2 further comprising:

comparing the received pseudorandom noise code of symbols over time with a copy of the pseudorandom noise code stored at the second location; and

generating a pulse when the received pseudorandom noise code matches with the copy of the pseudorandom noise code stored at the second location.

14. The method of claim 1 further comprising:

determining a propagation delay time for propagating the modulated signal from the first location to the second location.

15. The method of claim 14 further comprising:

adjusting the modulated signal to account for the propagation delay time.

16. The method of the claim 15 wherein adjusting the modulated signal occurs at the first location.

17. The method of claim 15 wherein adjusting the modulated signal occurs at the second location.

18. The method of claim 2 further comprising:

upon receiving the modulated signal at the second location, generating a second pseudorandom noise code of symbols that repeats over time at a frequency no greater than the fixed frequency of the timing pulse signal; and

transmitting the second pseudorandom noise code signal to the first location.

19. The method of claim 18 wherein transmission the second pseudorandom noise code of signal is over the same communications channel as transmission of the modulated signal.

20. The method of claim 18 further comprising:

receiving the second pseudorandom noise code signal at the first location; and

determining the propagation delay time between the first and second locations based on the received signal.

21. The method of claim 20 further comprising:

receiving the second pseudorandom noise code of symbols at the first location;

comparing the second pseudorandom noise code of symbols received over time with a copy of the second pseudorandom noise code stored at the first location; and

generating a pulse when the received second pseudorandom noise code matches with the copy of the second pseudorandom noise code stored at the first location.

22. The method of claim 21 further comprising:

comparing a pulse generated by the received second pseudorandom noise code signal with a pulse of the timing pulse signal to determine a propagation delay time.

23. The method of claim 22 further comprising:

adjusting the alignment of the predetermined position of the one of the symbols in the code with the occurrence of a pulse by the propagation delay time such that when the modulated signal is received at the second location, the occurrence of a symbol in the predetermined position within the code at the second location happens when at approximately the same time as a pulse in the timing pulse signal at the first location.

24. The method of claim 23 wherein the adjustment step occurs at the second location.

25. The method of claim 23 wherein the adjustment step occurs at the first location.

26. The method of claim 24 further comprising transmitting a message indicating the determined propagation delay to the second location.

27. Apparatus comprising:

a global positioning receiver configured to receive signals from a constellation of global positioning satellites and produce a timing pulse signal having a fixed frequency;

a pseudorandom noise code generator configured to generate a pseudorandom noise code of symbols that repeats over time at a frequency of no greater than the fixed frequency of the timing pulse signal, wherein for each instance of the pseudorandom noise code of symbols, the occurrence of a pulse in the timing pulse signal is aligned with a predetermined position of one of the symbols in the code; and

a transmitter configured to transmit the pseudorandom code of symbols to a remote device.

28. The apparatus of claim 27 wherein the global positioning receiver is configured to generate an oscillating signal from the signals received from the constellation of global positioning satellites.

29. The apparatus of claim 28 wherein the oscillating signal is applied to the pseudorandom code generator to produce the series of pseudorandom noise code of symbols.

30. The apparatus of claim 27 wherein the predetermined position is the same symbol position for each instance of the pseudorandom noise code of symbols.

31. The apparatus of claim 27 wherein the predetermined position is the first symbol position for each instance of the pseudorandom noise code of symbols.

32. The apparatus of claim 27 wherein the pseudorandom noise code generator is configured to generate a pseudorandom code of symbols having a length less than the period of the timing pulse signal.

33. The apparatus of claim 32 wherein the pseudorandom noise code generator is further configured to add bits to each instance of the pseudorandom noise code of symbols such that the resulting signal has a period approximately equal to the period of the timing pulse signal.

34. The apparatus of claim 32 wherein the additional bits comprise bits representing messaging information.

35. The apparatus of claim 27 wherein the global positioning receiver is configured to generate a time-of-day message from the received global positioning system signals.

36. The apparatus of claim 27 further comprising:

a mixing circuit configured to mix message data with the generated pseudorandom noise code.

37. The apparatus of claim 27 further comprising:

a receiver configured to receive a pseudorandom code of symbols from the remote device that was transmitted by the remote device upon the remote device'"'"'s receipt of the transmitted pseudorandom code of symbols.

38. The apparatus of claim 37 further comprising:

a shift register circuit configured to receive a pseudorandom code signal from the remote device and produce a pulse when the received a sequence of symbols in the received pseudorandom code signal matches with a predetermined sequence of symbols.

39. The apparatus of claim 37 further comprising:

a delay circuit configured to delay transmission of the pseudorandom code of symbols to the remote device by an amount derived from the time the shift register circuit produced the pulse and a time at which a timing pulse occurs in the timing pulse signal.

40. A base station for use in a cellular communication network, the base station comprising:

an input configured to receive a modulated timing pulse signal derived from a timing pulse signal having a fixed frequency generated by a remote global position system receiver; and

a demodulation circuit operably connected to the input and configured to demodulate the modulated timing pulse signal to derive a timing pulse signal corresponding to the timing pulse signal of the global positioning system receiver.

41. The base station of claim 40 wherein the modulated timing pulse signal comprises a pseudorandom code of symbols having a frequency no greater than that of the fixed frequency of the timing pulse signal, wherein the base station demodulation circuit comprises:

a shift register circuit configured to receive the pseudorandom code signal and produce a pulse when the received a sequence of symbols in the received pseudorandom code signal matches with a predetermined sequence of symbols; and

an oscillator configured to drive the shift register circuit at a reference frequency.

42. The base station of claim 40 further comprising:

a phase lock loop circuit configured to receive the pseudorandom code of symbols and drive the oscillator circuit at the frequency of the pseudorandom code of signals.

43. The base station of claim 42 wherein the frequency of the pseudorandom code of signals corresponds to a frequency of an oscillating signal produced by the remote global position system receiver.

44. The base station of claim 41 further comprising:

a transmitter circuit configured to transmit a signal to a remote device upon receiving the modulated timing pulse signal.

45. The base station of claim 44, wherein the transmitter circuit comprises:

a pseudorandom noise code generator configured to generate a repeating pseudorandom sequence of symbols that have a frequency of no greater than the frequency of the timing pulse signal.

46. A method for providing timing information to a base station in a cellular network, the method comprising:

receiving global positioning signals from a constellation of global positioning satellites;

generating a timing pulse signal having a series of timing pulses occurring at a fixed frequency from the received global positioning signals;

modulating at a first location the timing pulse signal with a carrier signal; and

transmitting the modulated signal to a base station located at a second location, wherein the second location is remote from the first location.

47. The method of claim 46 further comprising:

receiving the modulated signal at the remote base station; and

demodulating the modulated signal to derive a timing pulse signal at the remote base station corresponding to the timing pulse signal generated from the received global positioning signals.

48. The method of claim 46 further comprising:

upon receiving the modulated signal at the remote base station, generating at the remote base station a reply signal; and

transmitting the reply signal to a receiver at the first location.

49. The method of claim 48 further comprising:

receiving the reply signal at the first location; and

determining a delay between a derived timing signal at the remote base station and the timing signal generated from the received global positioning signals based on when the reply signal is received at the first location.

50. The method of claim 46 wherein modulating at a first location the timing pulse signal with a carrier signal comprises:

generating a pseudorandom noise code of symbols that repeats over time at a frequency of no greater than the fixed frequency of the timing pulse signal, wherein for each instance of the pseudorandom noise code of symbols, the occurrence of a pulse in the timing pulse signal is aligned with a predetermined position of one of the symbols in the code.