Novel pilot sequences and structures with low peak-to-average power ratio

• US 20060291431A1
• Filed: 05/30/2006
• Published: 12/28/2006
• Est. Priority Date: 05/31/2005
• Status: Abandoned Application

• Current Assignee: Nokia Corporation
• Original Assignee: Nokia Corporation
• Inventors: Pajukoski, Kari, Tiirola, Esa
• Application Number:
  US11/442,150
• Publication Number:
  US 20060291431A1
• Time in Patent Office: Days
• US Class Current: 370/335
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/26134 Pilot insertion in the transmitter chain, e.g. pilot overlapping with data, insertion in time or frequency domain
• CPC Class Codes: H04L 27/262 Reduction thereof by selection of pilot symbols

Abstract

Pilot signal sequences with a low Peak-to-average ratio are generated by a method comprising the steps of providing a first signal sequence consisting of a first number, m, of signal elements and known to have a frequency spectrum with either identical or nearly identical non-zero amplitude values in a first frequency interval, performing an invertible first transformation of the first signal sequence into a first frequency spectrum in the first frequency interval, the first frequency spectrum consisting of m first frequency samples, performing a second transformation of the first frequency spectrum into a second frequency spectrum consisting of n frequency samples in the first frequency interval, the n frequency samples being formed by the m first frequency samples and a third number, n minus m, of additional second frequency samples, which have zero amplitude, such that the second frequency spectrum has m frequency spikes distributed over the second frequency interval, and performing a third transformation, which forms an inverse of the first transformation, to the second frequency spectrum to obtain a second signal sequence forming the pilot signal sequence.]

Claims

1. A method for generating a pilot signal sequence for a data transmission from a transmitter to a receiver via a transmission carrier, comprising the steps of:

providing a first signal sequence comprising a first number, m, of signal elements and known to have a frequency spectrum with either identical or nearly identical non-zero amplitude values in a first frequency interval;

performing an invertible first transformation of the first signal sequence into a first frequency spectrum in the first frequency interval, the first frequency spectrum comprising m first frequency samples;

performing a second transformation of the first frequency spectrum into a second frequency spectrum comprising n frequency samples in the first frequency interval, the n frequency samples being formed by the m first frequency samples and a third number, n minus m, of additional second frequency samples, which have zero amplitude, such that the second frequency spectrum has m frequency spikes distributed over the second frequency interval; and

performing a third transformation, which forms an inverse of the first transformation, to the second frequency spectrum to obtain a second signal sequence forming the pilot signal sequence.

2. The method of claim 1, wherein the first signal sequence is a signal sequence, the first frequency spectrum of which comprises m first frequency samples with either identical or nearly identical amplitude values in the first frequency interval.

3. The method of claim 1, wherein the first signal sequence is a Constant-Amplitude-and-Zero-Autocorrelation sequence (CAZAC sequence).

4. The method of claim 1, wherein the step of providing the first signal sequence comprises selecting the first signal sequence in dependence on a bandwidth parameter of the transmission carrier.

5. The method of claim 1, wherein the first transformation is an m-point finite Fourier transformation.

6. The method of claim 5, wherein, the inverse of the first transformation is an n-point inverse finite Fourier transformation.

7. The method of claim 1, wherein the second transformation step is performed such that the frequency spikes of the second frequency spectrum are distributed over the complete bandwidth of the transmission carrier.

8. The method of claim 1, wherein the second transformation step comprises inserting the third number of additional frequency samples into the first frequency spectrum to form the second frequency spectrum.

9. The method of claim 8, wherein the second transformation step comprises inserting the third number of additional frequency samples into the first frequency spectrum such that there is at least one first frequency sample per coherence bandwidth in the second frequency spectrum.

10. The method of claim 8, wherein the second transformation step comprises inserting between adjacent first frequency samples a fourth number, p, of additional frequency samples, p being equal to the quotient of n/m minus one, and wherein n and m are chosen such that their quotient is an integer.

11. The method of claim 1, wherein the second frequency interval forms a transmission carrier in a Frequency Division Multiple Access (FDMA) technique.

12. The method of claim 1, wherein the second frequency interval has a bandwidth of either 1.25 MHz, 2.5 MHz, 5 MHz, 10 MHz, or 20 MHz.

13. The method of claim 12, wherein a frequency distance between the frequency samples of the second frequency spectrum is 240 kHz.

14. The method of claim 12, wherein the second number n of signal elements of the pilot-signal sequence is 32 for the bandwidth of 1.25 MHz, 64 for 2.5 MHz, 128 for 5 MHz, 256 for 10 MHz, or 512 for 20 MHz, respectively.

15. The method of claim 1, wherein the second transformation step comprises inserting a fifth number, q, of the n minus m second frequency samples at frequencies lower than the lowest frequency value of the first frequency samples, and a sixth number, r, of the n minus m second frequency samples at frequencies higher than the highest frequency value of the first frequency samples.

16. The method of claim 15, comprising, before the step of inserting the q and r second frequency samples, a step of selecting a code index value, and a step of selecting the values of the fifth and sixth numbers in dependence on the code index value.

17. The method of claim 15, wherein the step of selecting the values of the fifth and sixth numbers is performed under a constraint requiring that any selected combination of the fifth and sixth number, q and r, have a preset sum.

18. The method of claim 1, further comprising a step of storing a generated pilot sequence to a permanent memory, which is accessible by the transmitter before a transmission of the pilot sequence.

19. The method of claim 18, comprising the repeated performance of the steps of generating and storing a pilot signal sequence to the memory, until for each available bandwidth option of the transmission carrier a pilot sequence is stored in the memory.

20. A pilot signal sequence having a second number, n, of signal elements for transmission from a transmitter to a receiver via a transmission carrier in a data transmission according to a Frequency Division Multiple Access (FDMA) technique, the pilot signal having a frequency spectrum in a first frequency interval, as calculated by an n-point finite Fourier transform of the pilot signal sequence, which comprises:

a first number, m, of frequency spikes formed by m first frequency samples having non-zero amplitude frequency interval; and

a third number, n minus m, of second frequency samples having zero amplitude.

21. The pilot signal sequence of claim 20, comprising a frequency spectrum that can be transformed into a CAZAC-sequence by removing the second frequency samples from the spectrum and then performing an m-point inverse finite Fourier transform.

22. The pilot signal sequence of claim 20, comprising between adjacent first frequency samples a fourth number, p, of second frequency samples, p being equal to the quotient of n/m minus one, and wherein the quotient of n and m is an integer number.

23. The pilot signal sequence of claim 20, wherein the frequency spectrum of the pilot signal sequence extends over a bandwidth of either, 1.25 MHz, 2.5 MHz, 5 MHz, 10 MHz, or 20 MHz.

24. The pilot signal sequence of claim 22, wherein a frequency distance between the frequency spikes of the frequency spectrum is 240 kHz.

25. The pilot signal sequence of claim 22, wherein the second number n of signal elements of the pilot-signal sequence is 32 for the bandwidth of 1.25 MHz, 64 for 2.5 MHz, 128 for 5 MHz, 256 for 10 MHz, or 512 for 20 MHz, respectively.

26. The pilot signal sequence of claim 20, wherein the frequency spectrum of the pilot signal includes at least one frequency spike per coherence bandwidth of the transmission carrier.

27. The pilot signal sequence of claim 20, comprising a fifth number, q, of the n minus m second frequency samples at frequencies lower than the lowest frequency value of the first frequency samples, and a sixth number, r, of the n minus m additional frequency samples at frequencies higher than the highest frequency value of the first frequency samples.

28. A pilot generator for generating a pilot signal sequence for a data transmission from a transmitter to a receiver via a transmission carrier comprising:

a signal generator, which is configured to provide at its output a first signal sequence consisting of a first number, m, of signal elements and known to have a frequency spectrum with either identical or nearly identical non-zero amplitude values in a first frequency interval;

a first transformation unit which is configured to transform the first signal sequence into a first frequency spectrum in the first frequency interval using an invertible transformation, the first frequency spectrum consisting of m first frequency samples;

a second transformation unit, which is configured to transform the first frequency spectrum into a second frequency spectrum consisting of n frequency samples in a second frequency interval, the n frequency samples being formed by the m first frequency samples and a third number, n minus m, of additional second frequency samples, which have zero amplitude, such that the second frequency spectrum has m frequency spikes distributed over the second frequency interval; and

a third transformation unit, which is configured to apply the inverse of the first transformation to the second frequency spectrum to obtain a second signal sequence forming the pilot signal sequence.

29. The pilot generator of claim 28, wherein the signal generator is configured to provide at its output the first signal sequence in the form of a signal sequence, the first frequency spectrum of which consists of m first frequency samples with either identical or nearly identical amplitude values in the first frequency interval.

30. The pilot generator of claim 28, wherein the signal generator is configured to provide at its output the first signal sequence in the form of a Constant-Amplitude-and-Zero-Autocorrelation sequence (CAZAC sequence).

31. The pilot generator of claim 28, wherein the signal generator is configured to select the first signal sequence in dependence on a bandwidth parameter of the transmission carrier.

32. The pilot generator of claim 28, wherein the first transformation unit is configured to perform an m-point finite Fourier transformation.

33. The pilot generator of claim 32, wherein the third transformation unit is configured to perform an n-point inverse finite Fourier transformation.

34. The pilot generator of claim 28, wherein the second transformation step is performed such hat the frequency spikes of the second frequency spectrum are distributed over the complete bandwidth of the transmission carrier.

35. The pilot generator of claim 28, wherein the second transformation unit is configured to insert the third number of additional frequency samples into the first frequency spectrum to form the second frequency spectrum.

36. The pilot generator of claim 35, wherein the second transformation unit is configured to insert the third number of additional frequency samples into the first frequency spectrum such that there is at least one first frequency sample per coherence bandwidth in the second frequency spectrum.

37. The pilot generator of claim 36, wherein the second transformation unit is configured to insert between adjacent first frequency samples a fourth number, p, of additional frequency samples, p being equal to the quotient of n/m minus one, and wherein n and m are chosen such that their quotient is an integer.

38. The pilot generator of claim 28, which is configured to generate a pilot signal sequence for a data transmission from a transmitter to a receiver via a transmission carrier in a Frequency Division Multiple Access (FDMA) technique.

39. The pilot generator of claim 28, which is configured to generate a pilot signal sequence for a data transmission from a transmitter to a receiver via a transmission carrier having a bandwidth of either 1.25 MHz, 2.5 MHz, 5 MHz, 10 MHz, or 20 MHz.

40. The pilot generator of claim 39, wherein the signal generation unit is configured to provide a first signal sequence having a first frequency spectrum containing first frequency samples with a frequency distance of 240 kHz between each other.

41. The pilot generator of claim 40, which is configured to provide a pilot signal sequence, in which the second number n of signal elements of the pilot-signal sequence is 32 for the bandwidth of 1.25 MHz, 64 for 2.5 MHz, 128 for 5 MHz, 256 for 10 MHz, or 512 for 20 MHz, respectively.

42. The pilot generator of claim 28, wherein the second transformation step unit is configured to insert a fifth number, q, of the n minus m second frequency samples at frequencies lower than the lowest frequency value of the first frequency samples, and a sixth number, r, of the n minus m second frequency samples at frequencies higher than the highest frequency value of the first frequency samples.

43. The pilot generator of claim 42, comprising a pilot coding unit, which is connected with the second transformation unit and configured to select and provide at its output a code index value, wherein the second transformation unit is configured to select the values of the fifth and sixth numbers in dependence on the code index value received from the pilot coding unit.

44. A method for transmitting data from a transmitter to a receiver using a Frequency Division Multiple Access (FDMA) technique via a transmission carrier, comprising a step of:

transmitting a pilot signal sequence having a second number, n, of signal elements for transmission from the transmitter to the receiver via the transmission carrier in a data transmission according to the FDMA technique, the pilot signal having a frequency spectrum in a first frequency interval, as calculated by an n-point finite Fourier transform of the pilot signal sequence, wherein the pilot signal sequence comprises a first number, m, of frequency spikes formed by m first frequency samples having non-zero amplitude frequency interval and a third number, n minus m, of second frequency samples having zero amplitude.

45. The method of claim 44, wherein the pilot signal sequence is generated at the transmitter immediately before it is sent.

46. The method of claim 45, wherein the pilot signal sequence is read from a memory before it is sent.

47. The method of claim 45, wherein the data is transmitted in uplink direction from a terminal device to a network.

48. The method of claim 44, wherein the data is transmitted through a single transmission carrier.

49. The method of claim 48, wherein the pilot signal sequence is transmitted at least once during a transmission time interval allocated to the transmitter.

50. The method of claim 49, wherein each transmission of the pilot signal sequence in the transmission time interval is anteceded by a transmission of a cyclic prefix.

51. A method for generating a frequency spectrum of a pilot signal sequence, comprising the steps of:

providing a first signal sequence consisting of a first number, m, of signal elements and known to have a frequency spectrum with either identical or nearly identical non-zero amplitude values in a first frequency interval;

performing an invertible first transformation of the first signal sequence into a first frequency spectrum in the first frequency interval, the first frequency spectrum consisting of m first frequency samples; and

obtaining the frequency spectrum of the pilot signal sequence by performing a second transformation of the first frequency spectrum into a second frequency spectrum consisting of n frequency samples in the first frequency interval, the n frequency samples being formed by the m first frequency samples and a third number, n minus m, of additional second frequency samples, which have zero amplitude, such that the second frequency spectrum has m frequency spikes distributed over the second frequency interval.

52. The method of claim 51, wherein the first signal sequence is a signal sequence, the first frequency spectrum of which comprises m first frequency samples with either identical or nearly identical amplitude values in the first frequency interval.

53. The method of claim 51, further comprising a step of storing a representation of a generated frequency spectrum to a permanent data medium.

54. The method of claim 53, comprising the repeated performance of the steps of generating and storing representation of the frequency spectrum of a pilot signal sequence to the data medium, until for each available bandwidth option of the transmission carrier a representation of a frequency spectrum of a pilot signal sequence is stored in the data medium.

55. A pilot-frequency-spectrum generator for generating a frequency spectrum of a pilot signal sequence comprising:

a signal generator, which is configured to provide at its output a first signal sequence consisting of a first number, m, of signal elements and known to have a frequency spectrum with either identical or nearly identical non-zero amplitude values in a first frequency interval;

a first transformation unit which is configured to transform the first signal sequence into a first frequency spectrum in the first frequency interval using an invertible transformation, the first frequency spectrum consisting of m first frequency samples; and

a second transformation unit, which is configured to transform the first frequency spectrum into a second frequency spectrum consisting of n frequency samples in a second frequency interval, the n frequency samples being formed by the m first frequency samples and a third number, n minus m, of additional second frequency samples, which have zero amplitude, such that the second frequency spectrum has m frequency spikes distributed over the second frequency interval.

56. The pilot-frequency-spectrum generator of claim 55, wherein the signal generator is configured to provide at its output the first signal sequence in the form of a signal sequence, the first frequency spectrum of which consists of m first frequency samples with either identical or nearly identical amplitude values in the first frequency interval.

57. A data medium comprising at least one of:

a representation of at least one pilot signal sequence having a second number, n, of signal elements for transmission from a transmitter to a receiver via a transmission carrier in a data transmission according to a Frequency Division Multiple Access (FDMA) technique, the pilot signal having a frequency spectrum in a first frequency interval, as calculated by an n-point finite Fourier transform of the pilot signal sequence, the pilot signal sequence having a first number, m, of frequency spikes formed by m first frequency samples having non-zero amplitude frequency interval and a third number, n minus m, of second frequency samples having zero amplitude;

or

a representation of a frequency spectrum of the at least one pilot signal sequence.

58. A transmitter comprising:

a data medium comprising at least one of a representation of at least one pilot signal sequence having a second number, n, of signal elements for transmission from a transmitter to a receiver via a transmission carrier in a data transmission according to a Frequency Division Multiple Access (FDMA) technique, the pilot signal having a frequency spectrum in a first frequency interval, as calculated by an n-point finite Fourier transform of the pilot signal sequence, the pilot signal sequence having a first number, m, of frequency spikes formed by m first frequency samples having non-zero amplitude frequency interval and a third number, n minus m, of second frequency samples having zero amplitude, or a representation of a frequency spectrum of the at least one pilot signal sequence;

or

a pilot generator for generating the pilot signal sequence for data transmission from the transmitter to the receiver via the transmission carrier, the pilot generator, comprising

a signal generator, which is configured to provide at its output the first signal sequence consisting of the first number, m, of signal elements and known to have a frequency spectrum with either identical or nearly identical non-zero amplitude values in a first frequency interval;

a first transformation unit which is configured to transform the first signal sequence into a first frequency spectrum in the first frequency interval using an invertible transformation, the first frequency spectrum consisting of m first frequency samples;

a second transformation unit, which is configured to transform the first frequency spectrum into a second frequency spectrum consisting of n frequency samples in a second frequency interval, the n frequency samples being formed by the m first frequency samples and a third number, n minus m, of additional second frequency samples, which have zero amplitude, such that the second frequency spectrum has m frequency spikes distributed over the second frequency interval; and

a third transformation unit, which is configured to apply the inverse of the first transformation to the second frequency spectrum to obtain a second signal sequence forming the pilot signal sequence.

59. The transmitter of claim 58, wherein an output of either the data medium or the pilot generator and an output of a user-data source are connected with different inputs of a switching unit, which is configured to provide at its output either the output of the pilot generator or the output of the user-data source according to a predefined time schedule.

60. A receiver comprising:

a data medium comprising at least one of a representation of at least one pilot signal sequence having a second number, n, of signal elements for transmission from a transmitter to a receiver via a transmission carrier in a data transmission according to a Frequency Division Multiple Access (FDMA) technique, the pilot signal having a frequency spectrum in a first frequency interval, as calculated by an n-point finite Fourier transform of the pilot signal sequence, the pilot signal sequence having a first number, m, of frequency spikes formed by m first frequency samples having non-zero amplitude frequency interval and a third number, n minus m, of second frequency samples having zero amplitude, or a representation of a frequency spectrum of the at least one pilot signal sequence;

or

a pilot-frequency-spectrum generator for generating the pilot signal sequence for data transmission from the transmitter to the receiver via the transmission carrier, the pilot-frequency-spectrum generator, comprising

a signal generator, which is configured to provide at its output the first signal sequence consisting of the first number, m, of signal elements and known to have a frequency spectrum with either identical or nearly identical non-zero amplitude values in a first frequency interval;

a first transformation unit which is configured to transform the first signal sequence into a first frequency spectrum in the first frequency interval using an invertible transformation, the first frequency spectrum consisting of m first frequency samples;

a second transformation unit, which is configured to transform the first frequency spectrum into a second frequency spectrum consisting of n frequency samples in a second frequency interval, the n frequency samples being formed by the m first frequency samples and a third number, n minus m, of additional second frequency samples, which have zero amplitude, such that the second frequency spectrum has m frequency spikes distributed over the second frequency interval; and

a third transformation unit, which is configured to apply the inverse of the first transformation to the second frequency spectrum to obtain a second signal sequence forming the pilot signal sequence.

61. The receiver of claim 60, wherein an output of the data medium or of the pilot generator is connected to a channel-correction unit.

62. The receiver of claim 61, wherein the channel-correction unit is further connected to a Fast-Fourier-Transform unit on its input side and to an Inverse-Fast-Fourier-Transform unit on its output side, and configured to compare a frequency spectrum of a pilot signal sequence received from the Fast-Fourier-Transform unit to a frequency spectrum received from the data medium or the pilot generator, and to adjust channel-correction parameters in dependence on the result of the comparison.