Training sequences for peak to average power constrained modulation formats

• US 7,016,429 B1
• Filed: 09/28/2001
• Issued: 03/21/2006
• Est. Priority Date: 09/28/2001
• Status: Expired due to Fees

• Current Assignee: Intel Corporation
• Original Assignee: ArrayComm LLC (Ygomi LLC)
• Inventors: Dogan, Mithat C., Trott, Mitchell D.
• Primary Examiner(s): Tran, Khai
• Assistant Examiner(s): CHANG, EDITH M
• Application Number:
  US09/967,056
• Time in Patent Office: 1,635 Days
• Field of Search: 375/279, 375229-236, 375295-296, 375/308, 375/260, 375/267, 375/299, 375/272, 375/303, 375/329, 375/334, 375/347, 375/355, 375/364, 370/310, 370/227, 370328-329, 370/334, 370/347, 370/546, 342/386, 342/417, 342443-444, 455/68, 455/69, 455/78, 455/101, 455/10, 455/562.1
• US Class Current: 375/279
• CPC Class Codes: H04L 27/262 Reduction thereof by selection of pilot symbols

Abstract

A method and apparatus are provided that generate, transmit, or receive a training sequence in a communications system, where the training sequence exhibits certain desirable characteristics when used by a peak to average power constrained modulation formal. In one embodiment, the invention includes selecting an original training sequence from a set of possible original training sequences having at least one desired property, forming a modified training sequence by modifying the original training sequence based on a corresponding modifying sequence, such that the modified training sequence exhibits the desired property of the original training sequence when used in a peak to average power constrained modulation format that would otherwise impair the desired property of the original training sequence.

Claims

1. A method comprising:

selecting an original training sequence from a set of possible original training sequences having at least one or more desired properties, the selected original training sequence comprising a sequence of complex numbers corresponding to phase shifts employed by a π

/M−

MPSK modulation format, M being a positive integer; and

forming a modified training sequence by multiplying each element of the selected original training sequence by a corresponding element of a modifying sequence, the modifying sequence comprising a sequence of pairs of equal complex numbers, wherein each pair of equal complex numbers comprises the previous pair of equal complex numbers multiplied by exp<sup>j2π

/M</sup>;

wherein the modified training sequence exhibits the-one or more desired properties of the selected original training sequence when used in a peak to average power constrained modulation format that would otherwise impair the at least one or more desired properties of the selected original training sequence.

2. The method of claim 1, further comprising appending a prefix and a suffix to the selected original training sequence prior to forming the modified training sequence.

3. The method of claim 1, wherein the selecting of the selected original training sequence comprises cyclically shifting the original training sequence by some integer.

4. The method of claim 1, wherein the at least one or more desired properties comprise a function of an autocorrelation of any original training sequence in the set of possible original training sequences being below a threshold value.

5. The method of claim 1, wherein the at one or more desired properties comprise a function of a cross-correlation of any original training sequence in the set of possible original training sequences with any other original training sequence in the set of possible original training sequences being below a threshold value.

6. The method of claim 1, wherein the modulation format is π

/2−

2PSK modulation when M=2.

7. The method of claim 6, wherein the modifying sequence repeats the sequence (1,1,−

1,−

1).

8. The method of claim 1, wherein selecting the original training sequence comprises selecting a Gold sequence from Gold sequences.

9. The method of claim 1, wherein the modified training sequence is applied to at least one of a TDMA, a FDMA, a CDMA and a FDD radio communications system.

10. A method comprising:

selecting an original training sequence from a set of possible original training sequences having at least one or more desired properties, the selected original training sequence comprising a sequence of phase shifts to be performed on a waveform as employed by a π

/M−

MPSK modulation format, M being a positive integer; and

forming a modified training sequence by multiplying each element of the selected original training sequence by a corresponding element of a modifying sequence, the modifying sequence comprising a sequence of pairs of equal phase shifts, wherein each pair of equal phase shifts is larger in magnitude by 2π

/M radians than the previous pair of equal phase shifts;

wherein the modified training sequence exhibits at least one or more desired properties of the selected original training sequence when used in a peak to average power constrained modulation format that would otherwise impair at least one or more desired properties of the selected original training sequence.

11. The method of claim 10, wherein the modulation format is π

/2−

2PSK modulation, when M=2.

12. The method of claim 11, wherein the modifying sequence repeats the sequence (0,0,π

,π

) radians.

13. A method comprising:

transmitting a modified training sequence derived by selecting an original training sequence from a set of possible original training sequences having at least one or more desired properties, the selected original training sequence comprising a sequence of phase shifts to be performed on a waveform employed by a π

/M−

MPSK modulation format, M being a positive integer, and multiplying each element of the selected original training sequence by a corresponding element of a modifying sequence, the modifying sequence comprising a sequence of pairs of equal phase shifts, wherein each pair of equal phase shifts is larger in magnitude by 2π

/M radians than the previous pair of equal phase shifts.

14. A base station comprising:

a data storage element to store a modified training sequence derived by selecting an original training sequence from a set of possible original training sequences having at one or more desired properties, the selected original training sequence comprising a sequence of phase shifts to be performed on a waveform as employed by a π

/M−

MPSK modulation format, M being a positive integer, and multiplying each element of the selected original training sequence by a corresponding element of a modifying sequence, the modifying sequence comprising a sequence of pairs of equal phase shifts, wherein each pair of equal phase shifts is larger in magnitude by 2π

/M radians than the previous pair of equal phase shifts;

a receiver to receive a communication waveform; and

a processor to train the base station using the received communication waveform and the stored modified training sequence.

15. The base station of claim 14, wherein the selected original training sequence is selected by cyclically shifting the selected original training sequence by some integer.

16. The base station of claim 14, wherein the at least one or more desired properties comprise a function of the autocorrelation of any original training sequence in the set of possible original training sequences being below a threshold value.

17. The base station of claim 14, wherein the at least one or more desired properties comprise a function of the cross-correlation of any original training sequence in the set of possible original training sequences with any other original training sequence in the set of possible original training sequences being below a threshold value.

18. A machine-readable medium having stored thereon data representing instructions that, when executed by a processor, cause the processor to perform operations to:

select an original training sequence from a set of possible original training sequences having at least one or more desired properties, the selected original training sequence comprising a sequence of complex numbers corresponding to phase shifts employed by a π

/M−

MPSK modulation format, M being a positive integer; and

form a modified training sequence by multiplying each element of the selected original training sequence by a corresponding element of a modifying sequence, the modifying sequence comprising a sequence of pairs of equal complex numbers, wherein each pair of equal complex numbers comprises the previous pair equal complex numbers multiplied by exp<sup>j2π

/M</sup>;

wherein the modified training sequence exhibits at least one or more desired properties of the selected original training sequence when used in a peak to average power constrained modulation format that would otherwise impair the one or more desired properties of the selected original training sequence.

19. The machine-readable medium of claim 18, further comprising appending a prefix and a suffix to the selected original training sequence prior to forming the modified training sequence.

20. The machine-readable medium of claim 18, wherein the select the selected original training sequence comprises cyclically shifting the original training sequence by some integer.

21. The machine-readable medium of claim 18, wherein the at least one or more desired properties comprise a function of the autocorrelation of any original training sequence in the set of possible original training sequences being below a threshold value.

22. The machine-readable medium of claim 18, wherein the at least one or more desired properties comprise a function of the cross-correlation of any original training sequence in the set of possible original training sequences with any other original training sequence in the set of possible original training sequences being below a threshold value.

23. The machine-readable medium of claim 18, wherein the modified training sequence is applied to at least one of a TDMA, a FDMA, a CDMA and a FDD radio communications system.