Method and apparatus for scrambling based peak-to-average power ratio reduction without side information

• US 7,318,185 B2
• Filed: 12/09/2002
• Issued: 01/08/2008
• Est. Priority Date: 08/23/2001
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Zhu, Peiying, Tong, Wen, Khandani, Amir
• Primary Examiner(s): Lamarre, Guy
• Assistant Examiner(s): Alphonse, Fritz
• Application Number:
  US10/314,347
• Publication Number:
  US 20040093545A1
• Time in Patent Office: 1,856 Days
• Field of Search: 714/758, 714/748, 714/752, 714/798, 714/707
• US Class Current: 714/758
• CPC Class Codes: H04L 1/004 by using forward error control H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00
• CPC Class Codes: H04L 1/0058 Block-coded modulation
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 25/03866 using scrambling
• CPC Class Codes: H04L 27/2614 Peak power aspects
• CPC Class Codes: H04L 27/2615 Reduction thereof using coding

Abstract

Provided is a system and method for scrambling based peak-to-average power ratio reduction without side information. One of a set of scrambling sequences is used at the transmitter which results in either a minimum or acceptable peak power. Rather than transmitting side information identifying which of the set of scrambling sequences was selected, the scrambling sequence is also applied to the CRC, and using syndrome detection the receiver is capable of determining which scrambling sequence was used at the transmitter and can proceed with the necessary de-scrambling.

Claims

1. A method comprising:

calculating a CRC (cyclic redundancy check) for data block and combining the CRC with the data block;

applying a plurality of different scrambling sequences to the CRC combined with the data block to generate a corresponding plurality of scrambled blocks;

determining a respective communications performance characteristic associated with each of the scrambled blocks; and

selecting one of the scrambled blocks for transmission as a function of the performance characteristics.

2. A method according to claim 1 further comprising:

performing at least one signal processing step upon each scrambled block before determining the respective communications performance characteristic.

3. A method according to claim 2 wherein performing at least one signal processing step upon each scrambled block before determining the respective communications performance characteristic comprises:

performing at least one step from a group consisting of;

channel encoding, interleaving, modulation.

4. A method according to claim 2 wherein performing at least one signal processing step upon each scrambled block before determining the respective communications performance characteristic comprises:

performing a frequency-to-time conversion operation.

5. A method according to claim 4 wherein performing a frequency-to-time conversion operation comprises performing an inverse fast Fourier transform (IFFT).

6. A method according to claim 5 wherein the communications performance characteristic comprises a peak power measurement or any measure representative of peak power determined by identifying a maximum value of a time domain signal output by the IFFT.

7. A method according to claim 4 wherein the data block has a size larger than a frequency-to-time conversion block size, and wherein performing a frequency-to-time conversion comprises performing a respective frequency-to-time conversion operation in respect of each of a plurality of subsets of the scrambled block.

8. A method according to claim 1 wherein the communications performance characteristic comprises a peak power measurement or any measure representative of peak power.

9. A method according to claim 1 wherein the communications performance characteristic comprises a combination of peak power and an average energy measurement or any measure representative of the combined effect of the peak power and the average energy.

10. A method according to claim 1 wherein the data block has a size smaller than a frequency-to-time conversion block size, the method further comprising:

in respect of each of at least one additional data block;

a) calculating a CRC for the additional data block and combining the CRC with the additional data block;

b) applying a plurality of different scrambling sequences to the CRC combined with the additional data block to generate a corresponding plurality of scrambled blocks;

wherein determining a respective communications performance characteristic associated with each of the scrambled blocks comprises;

c) for each of a plurality of permutations of scrambled blocks, each permutation including one scrambled block for the data block and one scrambled block for each additional data block, combining the permutation of scrambled blocks and performing frequency-to-time conversion to generate a respective time domain signal;

d) determining a respective communications performance characteristic for cacti time domain signal; and

e) selecting one of the permutations of scrambled blocks for transmission as a function of the performance characteristics.

11. A method according to claim 1 wherein applying a plurality of different scrambling sequences to the CRC combined with the data block to generate a corresponding plurality of scrambled blocks is done in sequence.

12. A method according to claim 11 wherein applying a plurality of different scrambling sequences to the CRC combined with the data block to generate a corresponding plurality of scrambled blocks is done in sequence until a stopping criteria is satisfied.

13. A method according to claim 1 wherein applying a plurality of different scrambling sequences to the CRC combined with the data block to generate a corresponding plurality of scrambled blocks is done simultaneously for multiple scrambling sequences.

14. A method according to claim 1 further comprising performing multi-tone modulation by:

defining a respective signal constellation comprising a plurality of constellation points for each of a plurality of center frequencies;

defining for each tone and for each permutation of values for M data elements, a respective set of at least one constellation point any one of which may be used to represent the permutation of values for M data elements thereby providing a choice of constellation points for the permutation of values for M data elements, with at least one said set of at least one constellation point having more than one constellation point;

for each scrambled sequence, generating a multi-tone signal by mapping data elements of the scrambled sequence to each of said plurality of signal constellations and where there is a choice of constellation points, selecting a constellation point which will result in a reduced peak average power ratio for the multi-tone signal;

wherein the communications performance characteristic associated with each scrambled block is determined from the selected constellation points.

15. A method according to claim 14 wherein selecting a constellation point which will result in a reduced peak power for the multi-tone signal where there is a choice of constellation points comprises one of:

searching through all possible permutations of choices of constellation points for a set of constellation points which will result in an absolute minimum possible peak average power ratio; and

searching through possible permutations of choices of constellation points for a set of constellation points which will result in a peak average power ratio which is less than a predetermined threshold.

16. A method comprising:

encoding a data block using a cyclic code to generate an encoded block;

applying at least one of a plurality of different scrambling sequences to the encoded block to generate a scrambled block, each of the plurality of different scrambling sequences being uniquely associated with a respective information;

transmitting at least one scrambled block;

wherein only one of the plurality of different scrambling sequences is applied to the encoded block to generate a scrambled block, the one being selected in order to convey the respective information.

17. An apparatus comprising:

a CRC encoder adapted to calculate a CRC (cyclic redundancy check) for a data block and combining the CRC with the data block;

at least one scrambling sequence generator adapted to apply a plurality of different scrambling sequences to the CRC combined with the data block to generate a corresponding plurality of scrambled blocks;

a signal selector adapted to determine a respective communications performance characteristic associated with each of the scrambled blocks and to select one of the scrambled blocks for transmission as a function of the performance characteristics.

18. An apparatus according to claim 17 further comprising:

at least one of a channel encoder, interleaver and modulator adapted to process each scrambled block before determination of the respective communications performance characteristic.

19. An apparatus according to claim 17 further comprising:

an FFT block adapted to performing a frequency to time conversion operation prior to determination of the respective communications performance characteristic.

20. An apparatus according to claim 17 wherein the communications performance characteristic comprises a peak power measurement or any measure representative of peak power.

21. An apparatus according to claim 17 wherein the communications performance characteristic comprises a combination of peak power and an average energy measurement or any measure representative of the combined effect of the peak power and the average energy.

22. An apparatus according to claim 17 wherein the communications performance characteristic comprises a peak power to average power ratio or any measure representative of the peak power to average power ratio.

23. An apparatus according to claim 22 wherein the one scrambled block is selected for transmission based on having a minimum peak power to average power ratio.

24. A method of de-scrambling a sequence, the method comprising:

maintaining a respective syndrome associated with each of a plurality of scrambling sequences;

performing a CRC computation on the sequence to generate a CRC output;

determining if there is a match between the CRC output and any of said syndromes;

if there is a match between the CRC output and a particular one of the syndromes, applying the respective scrambling sequence to the sequence to generate a de-scrambled sequence.

25. A method according to claim 24 further comprising:

receiving a signal;

performing at least one signal processing step upon the received signal to generate the sequence.

26. A method according to claim 25 wherein performing at least one signal processing step upon the received signal to generate the sequence comprises performing at least one step from a group consisting of:

channel decoding, de-interleaving, demodulation.

27. A method according to claim 25 wherein performing at least one signal processing step upon the received signal to generate the sequence comprises performing a time-to-frequency conversion operation.

28. A method according to claim 27 wherein performing a time-to-frequency operation comprises performing a fast Fourier transform (FFT).

29. A method according to claim 24 wherein the sequence comprises a plurality of smaller sequences each having a size smaller than a frequency-to-time conversion block size, the method further comprising:

performing a time to frequency conversion operation on a received signal to generate the sequence;

sub-dividing the sequence into the plurality of smaller sequences;

wherein performing a CRC computation on the sequence to generate a CRC output comprises performing a respective CRC computation on each of the plurality of smaller sequences to generate a respective CRC output; and

for each of the plurality of smaller sequences and respective CRC outputs;

a) determining if there is a match between the respective CRC output and any of said syndromes;

b) if there is a match between the respective CRC output and a particular one of the syndromes, applying the respective scrambling sequence to the smaller sequence to generate a de-scrambled sequence.

30. A method according to claim 24 wherein the data block has a size larger than a frequency-to-time conversion block size, the method further comprising:

receiving a plurality of signals, and performing a time to frequency conversion on each of the received signals, and combining outputs of the time to conversion operations to generate the sequence.

31. A method according to claim 30 further comprising:

extracting information associated with did use of the respective scrambling sequence.

32. A method of de-scrambling a sequence, the method comprising:

maintaining a respective syndrome associated with each of a plurality of scrambling sequences;

performing a decoding operation associated with a cyclic code to generate a decoded output;

determining if there is a match between the decoded output and any of said syndromes;

if there is a match between the decoded output and a particular one of the syndromes, applying the respective scrambling sequence to the sequence to generate a de-scrambled sequence.

33. An apparatus comprising:

at least one storage element adapted to maintain a respective syndrome associated with each of a plurality of scrambling sequences;

a CRC device adapted to process a received data block of a sequence to generate a CRC output;

a descrambler adapted to determine if there is a match between the CRC output and any of said syndromes, and if there is a match between the CRC output and a particular one of the syndromes, to apply the respective scrambling sequence to the sequence to generate a de-scrambled sequence.

34. An apparatus according to claim 33 further comprising:

receiving circuitry for receiving a signal;

signal processing circuitry adapted to perform at least one signal processing step upon the received signal to generate the sequence.

35. An apparatus according to claim 33 further comprising at least one of:

a channel decode, de-interleaver, and demodulater.

36. An apparatus according to claim 33 further comprising time-to-frequency conversion circuitry adapted to perform a time-to-frequency conversion operation.

37. An apparatus according to claim 36 wherein the time-to-frequency conversion circuitry comprises a fast Fourier transform (FFT) function.

38. An apparatus according to claim 33 further adapted to extract information associated with the use of the respective scrambling sequence.