Preamble detection with unknown channel

• US 8,175,197 B2
• Filed: 03/13/2007
• Issued: 05/08/2012
• Est. Priority Date: 03/17/2006
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Marvell World Trade Limited (Marvell Technology Group Limited)
• Inventors: Lee, Jungwon, Lou, Hui-Ling
• Primary Examiner(s): PATEL, DHAVAL V
• Application Number:
  US11/717,405
• Publication Number:
  US 20070217534A1
• Time in Patent Office: 1,883 Days
• Field of Search: 375/260, 375/267, 375/295, 375/296, 375/297, 375/340, 375/345, 375/346, 375/343, 370/203, 370/204, 370/205, 370/208, 370/209, 370/210
• US Class Current: 375/343
• 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 includes a correlation module and a control module. The correlation module is configured to generate correlation values based on a correlation of modulated signals with a plurality of preamble sequences and generate correlation values. The modulated signals include sub-carriers modulated using orthogonal frequency domain multiplexing (OFDM). The control module is configured to select a largest correlation value from the correlation values and detect one of the preamble sequences in the modulated signals upon determining that a magnitude of the largest correlation value is greater than or equal to a first predetermined threshold. The control module divides N of the sub-carriers into L bands in response to a channel gain of the sub-carriers not being substantially the same for all of the sub-carriers, where N and L are integers greater than 1, and where each of the L bands includes N/L of the sub-carriers.

Claims

1. A system, comprising:

a correlation module configured to generate correlation values based on a correlation of modulated signals with a plurality of preamble sequences, wherein the modulated signals include sub-carriers modulated using orthogonal frequency domain multiplexing (OFDM); and

a control module configured to

select a largest correlation value from the correlation values, and

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

wherein the control module divides N of the sub-carriers into L bands in response to a channel gain of the sub-carriers not being substantially the same for all of the sub-carriers, where N and L are integers greater than 1, and where each of the L bands includes N/L of the sub-carriers.

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

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

4. The system of claim 1, wherein the control module is configured to identify a segment of a base station that transmitted the modulated signals based on the one of the preamble sequences.

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

6. The system of claim 1, wherein the sub-carriers have a random channel phase.

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

8. The system of claim 7, wherein the 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.

9. The system of claim 1, wherein the first predetermined threshold is based on a signal strength of the modulated signals.

10. The system of claim 1, wherein the modulated signals include a fractional carrier frequency offset (CFO) configured to generate a phase error that is substantially the same in each one of the modulated signals.

11. The system of claim 1, wherein the modulated signals include an integer carrier frequency offset (CFO) configured to generate a phase error that is substantially the same in each one of the modulated signals.

12. A physical layer module (PHY) comprising:

the system of claim 1; and

a transceiver module configured to

communicate with the correlation module and the control module; and

receive the modulated signals.

13. A network device comprising:

the PHY of claim 12; and

at least one antenna configured to communicate with the transceiver module.

14. The system of claim 1, wherein the correlation module is configured to:

correlate symbols in every P^th one of the N/L of the sub-carriers in each of the L bands with corresponding symbols in each of the preamble sequences; and

generate intra-band correlation values for each band for each of the preamble sequences,

where P is an integer greater than or equal to 1.

15. The system of claim 14, wherein the control module is configured to:

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

generate a magnitude of each of the band correlation value; and

generate the correlation values by adding the magnitude of each of the band correlation value for each of the preamble sequences.

16. A method, comprising:

receiving modulated signals, wherein the modulated signals include sub-carriers modulated using orthogonal frequency domain multiplexing (OFDM);

dividing N of the sub-carriers into L bands in response to a channel gain of the sub-carriers not being substantially the same for all of the sub-carriers, where N and L are integers greater than 1, and where each of the L bands includes N/L of the sub-carriers;

correlating the modulated signals with a plurality of preamble sequences;

generating correlation values based on the correlating;

selecting a largest correlation value from the correlation values; and

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

17. The method of claim 16, further comprising storing the preamble sequences, wherein each of the preamble sequences is different from others of the preamble sequences.

18. The method of claim 16, further comprising identifying a segment of a base station that transmitted the modulated signals based on the one of the preamble sequences.

19. The method of claim 16, wherein every P^th one of the sub-carriers is modulated with a preamble bit, where P is an integer greater than or equal to 1, and wherein the sub-carriers have a random channel phase.

20. The method of claim 16, wherein the preamble sequences have a cross-correlation value of less than or equal to a second predetermined threshold.

21. The method of claim 20, further comprising determining that the 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.

22. The method of claim 16, further comprising determining the first predetermined threshold based on a signal strength of the modulated signals.

23. The method of claim 16, wherein the modulated signals have a fractional carrier frequency offset (CFO) that generates a phase error that is substantially the same in each one of the modulated signals.

24. The method of claim 16, wherein the modulated signals have an integer carrier frequency offset (CFO) that generates a phase error that is substantially the same in each one of the modulated signals.

25. The method of claim 16, further comprising

correlating symbols in every P^th one of the N/L of the sub-carriers in each of the L bands with corresponding symbols in each of the preamble sequences;

and

generating intra-band correlation values for each band for each of the preamble sequences,

where P is an integer greater than or equal to 1.

26. The method of claim 25, further comprising:

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

generating a magnitude of each of the band correlation value; and

generating the correlation values by adding the magnitude of each of the band correlation value for each of the preamble sequences.

27. A system, comprising:

correlation means for generating correlation values based on a correlation of modulated signals with a plurality of preamble sequences, wherein the modulated signals include sub-carriers modulated using orthogonal frequency domain multiplexing (OFDM); and

control means for

selecting a largest correlation value from the correlation values, and

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

wherein the control means divides N of the sub-carriers into L bands in response to a channel gain of the sub-carriers not being substantially the same for all of the sub-carriers, where N and L are integers greater than 1, and where each of the L bands includes N/L of the sub-carriers.

28. The system of claim 27, wherein each of the preamble sequences is different from others of the preamble sequences.

29. The system of claim 27, wherein the preamble sequences are stored in one of the correlation means and the control means.

30. The system of claim 27, wherein the control means identifies a segment of a base station that transmitted the modulated signals based on the one of the preamble sequences.

31. The system of claim 27, wherein every P^th one of the sub-carriers is modulated with a preamble bit, where P is an integer greater than or equal to 1.

32. The system of claim 27, wherein the sub-carriers have a random channel phase.

33. The system of claim 27, wherein the preamble sequences have a cross-correlation value of less than or equal to a second predetermined threshold.

34. The system of claim 33, wherein the 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.

35. The system of claim 27, wherein the first predetermined threshold is based on a signal strength of the modulated signals.

36. The system of claim 27, wherein the modulated signals include a fractional carrier frequency offset (CFO) that generates a phase error that is substantially the same in each one of the modulated signals.

37. The system of claim 27, wherein the modulated signals include an integer carrier frequency offset (CFO) that generates a phase error that is substantially the same in each one of the modulated signals.

38. A physical layer means (PHY) comprising:

the system of claim 27; and

transceiver means for communicating with the correlation means and the control means and that receives the modulated signals.

39. A network device comprising:

the PHY means of claim 38; and

at least one antenna means for communicating with the transceiver means.

40. The system of claim 27, wherein the correlation means:

correlates symbols in every P^th one of the N/L of the sub-carriers in each of the L bands with corresponding symbols in each of the preamble sequences, and

generates intra-band correlation values for each band for each of the preamble sequences,

where P is an integer greater than or equal to 1.

41. The system of claim 40 wherein the control means:

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

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

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

42. A computer program stored on a non-transitory computer-readable medium and executable by a processor, the computer program comprising instructions for:

receiving modulated signals, wherein the modulated signals include sub-carriers modulated using orthogonal frequency domain multiplexing (OFDM);

dividing N of the sub-carriers into L bands in response to a channel gain of the sub-carriers not being substantially the same for all of the sub-carriers, where N and L are integers greater than 1, and where each of the L bands includes N/L of the sub-carriers;

correlating the modulated signals with a plurality of preamble sequences;

generating correlation values based on the correlating;

selecting a largest correlation value from the correlation values; and

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

43. The computer program of claim 42, further comprising instructions for storing the preamble sequences, wherein each of the preamble sequences is different from others of the preamble sequences.

44. The computer program of claim 42, further comprising instructions for identifying a segment of a base station that transmitted the modulated signals based on the one of the preamble sequences.

45. The computer program of claim 42, wherein every P^th one of the sub-carriers is modulated with a preamble bit, where P is an integer greater than or equal to 1, and wherein the sub-carriers have a random channel phase.

46. The computer program of claim 42, wherein the preamble sequences have a cross-correlation value of less than or equal to a second predetermined threshold.

47. The computer program of claim 46, further comprising instructions for determining that the 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.

48. The computer program of claim 42, further comprising instructions for determining the first predetermined threshold based on a signal strength of the modulated signals.

49. The computer program of claim 42, wherein the modulated signals have a fractional carrier frequency offset (CFO) that generates a phase error that is substantially the same in each one of the modulated signals.

50. The computer program of claim 42, wherein the modulated signals have an integer carrier frequency offset (CFO) that generates a phase error that is substantially the same in each one of the modulated signals.

51. The computer program of claim 42, further comprising instructions for:

correlating symbols in every P^th one of the N/L of the sub-carriers in each of the L bands with corresponding symbols in each of the preamble sequences; and

generating intra-band correlation values for each band for each of the preamble sequences,

where P is an integer greater than or equal to 1.

52. The computer program of claim 51, further comprising instructions for:

generating a band correlation value for each of the L bands and for each of the preamble sequences by adding the intra-band correlation values,

generating a magnitude of each of the band correlation value, and

generating the correlation values by adding the magnitude of each of the band correlation value for each of the preamble sequences.