Method for retrieving sequences having minimum PAPR in OFDM communication system

• US 20040136315A1
• Filed: 12/29/2003
• Published: 07/15/2004
• Est. Priority Date: 12/27/2002
• Status: Abandoned Application

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Chang, Seok-Il
• Application Number:
  US10/745,638
• Publication Number:
  US 20040136315A1
• Time in Patent Office: Days
• US Class Current: 370/206
• CPC Class Codes: H04L 27/2614 Peak power aspects
• CPC Class Codes: H04L 27/3411 reducing the peak to average power ratio or the mean power of the constellation; Arrangements for increasing the shape gain of a signal set

Abstract

In a method for retrieving sequences having a minimum PAPR (peak to average power ratio) in an OFDM (orthogonal frequency division multiplexing) system, by using characteristics in which all sequences of the OFDM system are classified into cosets having the same PAPR, PAPRs of sequences in which early two elements are fixed as “0” are calculated. A sequence having a minimum PAPR is selected from among the calculated PAPRs, and sequences allocated to the coset in which the selected sequence is included are retrieved as sequences having the minimum PAPR. In addition, according to PAPRs of sequences having early two elements fixed as “0” and the number of sequences of a coset including the sequences having early two elements fixed as “0,” it is possible to quickly and efficiently analyze PAPR distribution of all sequences. Accordingly, the OFDM system can be designed as a device having a low PAPR and low dynamic range.

Claims

1. A method for retrieving sequences having a minimum peak to average power ratio in an orthogonal frequency division multiplexing system, comprising:

classifying all input sequences into cosets having the same peak to average power ratio;

retrieving sequences in which early two elements are fixed as a prescribed value;

detecting sequences having a minimum peak to average power ratio among the retrieved sequences;

selecting cosets in which the detected sequences are included; and

extracting sequences included in the selected cosets.

2. The method of claim 1, wherein the prescribed value is “

0.”

3. The method of claim 1, wherein sequences generated by conversion for shifting by a prescribed time on a timing axis and conversion for multiplying by a random phase are allocated to the same coset in the classifying step.

4. The method of claim 1, wherein said classifying allocates a sequence a(φ

) and a sequence a^(m) to the same coset on the basis of a sequence a=(a₀,a₁, . . . , a<sub>N−

1</sub>) when the number of carriers is N and a M-PSK modulation method is used, and wherein

a(φ

)=(a₀+φ

, a₁+φ

, . . . , a<sub>N−

1</sub>+φ

), where φ

=0,1, . . . M−

1,a^(m)=(a^(m)₀,a^(m)₁, . . . , a^(m)<sub>N−

1</sub>), where m=0,1,2, . . . , M−

1, and

an i-th sequence of the sequence a^(m) is

a^(m)_i=a_i+im (mod M), where i=0,1, . . . , N−

1.

5. The method of claim 1, wherein said retrieving retrieves a sequence a=(0,0,a₂,a₃, . . . , a_N−

1),where a_i=0,1,2, . . . M−

1 when the number of carriers is N and a M-PSK modulation method is used.

6. The method of claim 1, wherein said retrieving includes:

calculating peak to average power ratios of the retrieved sequences; and

selecting a minimum peak to average power ratio among the calculated peak to average power ratios.

7. The method of claim 1, further comprising:

calculating peak to average power ratios of sequences in which the early two elements are fixed as the prescribed value; and

analyzing peak to average power ratio distribution of the all input sequences by using a number of sequences respectively allocated to cosets in which the sequences having the early two elements fixed as the prescribed value are included and using the calculated peak to average power ratios.

8. The method of claim 7, wherein the analyzed peak to average power ratio distribution is used for determining a dynamic range required for a device of the orthogonal frequency division multiplexing system.

9. A method for retrieving sequences having a minimum peak to average power ratio in an orthogonal frequency division multiplexing system, comprising:

retrieving sequences in which early two elements are fixed as “

0”

;

calculating peak to average power ratios of the retrieved sequences;

selecting a minimum peak to average power ratio among the calculated peak to average power ratios and detecting sequences having the minimum peak to average power ratio;

selecting cosets in which the detected sequences are included; and

generating sequences included in the selected cosets.

10. The method of claim 9, wherein sequences having the early two elements fixed as “

0”

are included in different cosets, and sequences included in the same coset have the same peak to average power ratio characteristics.

11. The method of claim 9, wherein said retrieving retrieves sequences a=(0,0,a₂,a₃, . . . , a_i, . . ., a_N−

1) when the number of carriers is N and a M-PSK modulation method is used, and wherein a_i=0,1,2, . . . M−

1, and i=2,3, . . . , N−

1.

12. The method of claim 9, wherein said generating generates sequences having the same peak to average power ratio characteristics as the peak to average power ratio of the detected sequence by a first conversion for multiplying the detected sequence by a prescribed phase, and by a second conversion for shifting the detected sequence by a prescribed time on a timing axis.

13. The method of claim 12, wherein sequences generated by the first conversion are

a(φ

)=(a₀+φ

, a₁+φ

, . . . , a<sub>N−

1</sub>+φ

), where φ

=0,1, . . . M−

1, and

sequences generated by the second conversion are

a^(m)=(a^(m)₀,a^(m)₁, . . . , a^(m)<sub>N−

1</sub>), where m=0,1,2, . . . , M−

1,

when the number of carriers is N and a M-PSK modulation method is used, and wherein

an i-th sequence of the sequence a^(m) is

a^(m)_i=a_i+im (mod M), where i=0,1, . . . , N−

1.

14. An apparatus for retrieving sequences having a minimum peak to average power ratio in a communication system, comprising:

a signal mapper;

a retriever; and

a modulator,

wherein input sequences are classified into cosets having the same peak to average power ratio, and sequences are extracted from selected cosets in which detected sequences are included, said detected sequences having minimum peak to average power ratio among retrieved sequences in which early two elements are a prescribed value.

15. The apparatus of claim 14, wherein said prescribed value is “

0.”

16. The apparatus of claim 14, wherein sequences having said prescribed value are included in different cosets, and sequences included in the same coset have the same peak to average power ratio characteristics.

17. An apparatus for retrieving sequences having a minimum peak to average power ratio in a communication system, comprising:

a signal mapper;

a retriever; and

a modulator,

wherein sequences included in selected cosets are generated, said selected cosets including sequences having both minimum peak to average power ratio and a prescribed value for early two elements.

18. The apparatus of claim 17, wherein said prescribed value is “

0.”

19. The apparatus of claim 17, wherein sequences having said prescribed value are included in different cosets, and sequences included in the same coset have the same peak to average power ratio characteristics.