Preamble detection with unknown channel

• US 20070217534A1
• Filed: 03/13/2007
• Published: 09/20/2007
• Est. Priority Date: 03/17/2006
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Lee, Jungwon, Lou, Hui-Ling
• Granted Patent: US 8,175,197 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04L 27/2656 Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 27/2675 Pilot or known symbols
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601

Abstract

A system comprises a correlation module that correlates modulated signals with a plurality of preamble sequences and that generates correlation values. A control module selects a largest correlation value from said correlation values and detects one of said preamble sequences in said modulated signals upon determining that a magnitude of said largest correlation value is greater than or equal to a first predetermined threshold.

Claims

1. A system, comprising:

a correlation module that correlates modulated signals with a plurality of preamble sequences and that generates correlation values; and

a control module that selects a largest correlation value from said correlation values and that detects one of said preamble sequences in said modulated signals upon determining that a magnitude of said largest correlation value is greater than or equal to a first predetermined threshold.

2. The system of claim 1 wherein each of said preamble sequences is different from others of said preamble sequences.

3. The system of claim 1 wherein said preamble sequences are stored in one of said correlation module and said control module.

4. The system of claim 1 wherein said control module identifies a segment of a base station that transmitted said modulated signals based on said one of said preamble sequences.

5. The system of claim 1 wherein said modulated signals include sub-carriers that are modulated using orthogonal frequency domain multiplexing (OFDM).

6. The system of claim 5 wherein every P^th one of said sub-carriers is modulated with a preamble bit, where P is an integer greater than or equal to 1.

7. The system of claim 5 wherein said sub-carriers have a common channel gain and a random channel phase.

8. The system of claim 1 wherein said preamble sequences have a cross-correlation value of less than or equal to a second predetermined threshold.

9. The system of claim 8 wherein said second predetermined threshold is less than approximately 0.2 for an orthogonal frequency domain multiplexing (OFDM) system using a 1024 fast Fourier transform (FFT) mode.

10. The system of claim 1 wherein said first predetermined threshold is based on the signal strength of said modulated signals.

11. The system of claim 1 wherein said modulated signals include a fractional carrier frequency offset (CFO) that generates a phase error that is substantially the same in each one of said modulated signals.

12. The system of claim 1 wherein said modulated signals include an integer carrier frequency offset (CFO) that generates a phase error that is substantially the same in each one of said modulated signals.

13. A physical layer module (PHY) comprising the system of claim 1 and further comprising a transceiver module that communicates with said correlation module and said control module and that receives said modulated signals.

14. A network device comprising the PHY of claim 13 and further comprising at least one antenna that communicates with said transceiver module.

15. The system of claim 5 wherein said control module divides N of said sub-carriers into L bands when a channel gain of said sub-carriers is not substantially the same for all of said sub-carriers, where N and L are integers greater than or equal to 1, and where each of said L bands includes N/L of said sub-carriers.

16. The system of claim 15 wherein said correlation module correlates symbols in every P^th one of said N/L sub-carriers in each of said L bands with corresponding symbols in each of said preamble sequences and generates intra-band correlation values for each band for each of said preamble sequences, where P is an integer greater than or equal to 1.

17. The system of claim 16 wherein said control module:

generates a band correlation value for each of said L bands and for each of said preamble sequences by adding said intra-band correlation values;

generates a magnitude of each of said band correlation value; and

generates said correlation values by adding said magnitude of each of said band correlation value for each of said preamble sequences.

18. A method, comprising:

correlating modulated signals with a plurality of preamble sequences;

generating correlation values based on said correlating;

selecting a largest correlation value from said correlation values; and

detecting one of said preamble sequences in said modulated signals upon determining that a magnitude of said largest correlation value is greater than or equal to a first predetermined threshold.

19. The method of claim 18 further comprising storing said preamble sequences, wherein each of said preamble sequences is different from others of said preamble sequences.

20. The method of claim 18 further comprising identifying a segment of a base station that transmitted said modulated signals based on said one of said preamble sequences.

21. The method of claim 18 further comprising receiving said modulated signals that include sub-carriers that are modulated using orthogonal frequency domain multiplexing (OFDM), wherein every P^th one of said sub-carriers is modulated with a preamble bit, where P is an integer greater than or equal to 1, and wherein said sub-carriers have a common channel gain and a random channel phase.

22. The method of claim 18 further comprising correlating said modulated signals with said preamble sequences having a cross-correlation value of less than or equal to a second predetermined threshold.

23. The method of claim 22 further comprising determining that said second predetermined threshold is less than approximately 0.2 for an orthogonal frequency domain multiplexing (OFDM) method using a 1024 fast Fourier transform (FFT) mode.

24. The method of claim 18 further comprising determining said first predetermined threshold based on the signal strength of said modulated signals.

25. The method of claim 18 further comprising receiving said modulated signals having a fractional carrier frequency offset (CFO) that generates a phase error that is substantially the same in each one of said modulated signals.

26. The method of claim 18 further comprising receiving said modulated signals having an integer carrier frequency offset (CFO) that generates a phase error that is substantially the same in each one of said modulated signals.

27. The method of claim 21 further comprising dividing N of said sub-carriers into L bands when a channel gain of said sub-carriers is not substantially the same for all of said sub-carriers, where N and L are integers greater than or equal to 1, and where each of said L bands includes N/L of said sub-carriers.

28. The method of claim 27 further comprising correlating symbols in every P^th one of said N/L sub-carriers in each of said L bands with corresponding symbols in each of said preamble sequences and generating intra-band correlation values for each band for each of said preamble sequences, where P is an integer greater than or equal to 1.

29. The method of claim 28 further comprising generating a band correlation value for each of said L bands and for each of said preamble sequences by adding said intra-band correlation values, generating a magnitude of each of said band correlation value, and generating said correlation values by adding said magnitude of each of said band correlation value for each of said preamble sequences.

30. A system, comprising:

correlation means for correlating modulated signals with a plurality of preamble sequences and generating correlation values; and

control means for selecting a largest correlation value from said correlation values and detecting one of said preamble sequences in said modulated signals upon determining that a magnitude of said largest correlation value is greater than or equal to a first predetermined threshold.

31. The system of claim 30 wherein each of said preamble sequences is different from others of said preamble sequences.

32. The system of claim 30 wherein said preamble sequences are stored in one of said correlation means and said control means.

33. The system of claim 30 wherein said control means identifies a segment of a base station that transmitted said modulated signals based on said one of said preamble sequences.

34. The system of claim 30 wherein said modulated signals include sub-carriers that are modulated using orthogonal frequency domain multiplexing (OFDM).

35. The system of claim 34 wherein every P^th one of said sub-carriers is modulated with a preamble bit, where P is an integer greater than or equal to 1.

36. The system of claim 34 wherein said sub-carriers have a common channel gain and a random channel phase.

37. The system of claim 30 wherein said preamble sequences have a cross-correlation value of less than or equal to a second predetermined threshold.

38. The system of claim 37 wherein said second predetermined threshold is less than approximately 0.2 for an orthogonal frequency domain multiplexing (OFDM) system using a 1024 fast Fourier transform (FFT) mode.

39. The system of claim 30 wherein said first predetermined threshold is based on the signal strength of said modulated signals.

40. The system of claim 30 wherein said modulated signals include a fractional carrier frequency offset (CFO) that generates a phase error that is substantially the same in each one of said modulated signals.

41. The system of claim 30 wherein said modulated signals include an integer carrier frequency offset (CFO) that generates a phase error that is substantially the same in each one of said modulated signals.

42. A physical layer means (PHY) comprising the system of claim 30 and further comprising transceiver means for communicating with said correlation means and said control means and that receives said modulated signals.

43. A network device comprising the PHY means of claim 42 and further comprising at least one antenna means for communicating with said transceiver means.

44. The system of claim 34 wherein said control means divides N of said sub-carriers into L bands when a channel gain of said sub-carriers is not substantially the same for all of said sub-carriers, where N and L are integers greater than or equal to 1, and where each of said L bands includes N/L of said sub-carriers.

45. The system of claim 44 wherein said correlation means correlates symbols in every P^th one of said N/L sub-carriers in each of said L bands with corresponding symbols in each of said preamble sequences and generates intra-band correlation values for each band for each of said preamble sequences, where P is an integer greater than or equal to 1.

46. The system of claim 45 wherein said control means:

generates a band correlation value for each of said L bands and for each of said preamble sequences by adding said intra-band correlation values;

generates a magnitude of each of said band correlation value; and

generates said correlation values by adding said magnitude of each of said band correlation value for each of said preamble sequences.

47. A computer program executed by a processor, comprising:

correlating modulated signals with a plurality of preamble sequences;

generating correlation values based on said correlating;

selecting a largest correlation value from said correlation values; and

detecting one of said preamble sequences in said modulated signals upon determining that a magnitude of said largest correlation value is greater than or equal to a first predetermined threshold.

48. The computer program of claim 47 further comprising storing said preamble sequences, wherein each of said preamble sequences is different from others of said preamble sequences.

49. The computer program of claim 47 further comprising identifying a segment of a base station that transmitted said modulated signals based on said one of said preamble sequences.

50. The computer program of claim 47 further comprising receiving said modulated signals that include sub-carriers that are modulated using orthogonal frequency domain multiplexing (OFDM), wherein every P^th one of said sub-carriers is modulated with a preamble bit, where P is an integer greater than or equal to 1, and wherein said sub-carriers have a common channel gain and a random channel phase.

51. The computer program of claim 47 further comprising correlating said modulated signals with said preamble sequences having a cross-correlation value of less than or equal to a second predetermined threshold.

52. The computer program of claim 51 further comprising determining that said second predetermined threshold is less than approximately 0.2 for an orthogonal frequency domain multiplexing (OFDM) computer program using a 1024 fast Fourier transform (FFT) mode.

53. The computer program of claim 47 further comprising determining said first predetermined threshold based on the signal strength of said modulated signals.

54. The computer program of claim 47 further comprising receiving said modulated signals having a fractional carrier frequency offset (CFO) that generates a phase error that is substantially the same in each one of said modulated signals.

55. The computer program of claim 47 further comprising receiving said modulated signals having an integer carrier frequency offset (CFO) that generates a phase error that is substantially the same in each one of said modulated signals.

56. The computer program of claim 50 further comprising dividing N of said sub-carriers into L bands when a channel gain of said sub-carriers is not substantially the same for all of said sub-carriers, where N and L are integers greater than or equal to 1, and where each of said L bands includes N/L of said sub-carriers.

57. The computer program of claim 56 further comprising correlating symbols in every P^th one of said N/L sub-carriers in each of said L bands with corresponding symbols in each of said preamble sequences and generating intra-band correlation values for each band for each of said preamble sequences, where P is an integer greater than or equal to 1.

58. The computer program of claim 57 further comprising generating a band correlation value for each of said L bands and for each of said preamble sequences by adding said intra-band correlation values, generating a magnitude of each of said band correlation value, and generating said correlation values by adding said magnitude of each of said band correlation value for each of said preamble sequences.