Apparatus and method for soft-decision demodulating in non-square quadrature amplitude modulation

• US 9,832,065 B2
• Filed: 05/11/2016
• Issued: 11/28/2017
• Est. Priority Date: 05/15/2015
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Jung, Joon Young, Lee, Je Won, Choi, Dong Joon, Hur, Nam Ho
• Primary Examiner(s): Yu, Lihong
• Application Number:
  US15/151,768
• Publication Number:
  US 20160337081A1
• Time in Patent Office: 566 Days
• Field of Search: 375341
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 27/38 Demodulator circuits; Receiver circuits

Abstract

Disclosed are an apparatus and a method for soft-decision demodulating in non-square quadrature amplitude modulation. The apparatus includes: a signal receiving unit receiving a quadrature amplitude modulation (QAM) modulated signal at an m modulation degree at a transmitting side; a soft-decision bit calculating unit determining a soft-decision bit value by calculating log likelihood ratios (LLRs) for m bits of the received QAM modulated signal; and a signal decoding unit restoring the received QAM modulated signal based on the determined soft-decision bit value, in which the soft-decision bit calculating unit defines a log likelihood ratio calculation equation by approximating soft-decision boundary points of constellation points for m bits of non-square QAM having odd bits, respectively.

Claims

1. An apparatus for soft-decision demodulating in non-square quadrature amplitude modulation, the apparatus comprising:

a signal receiving unit receiving a quadrature amplitude modulation (QAM) signal modulated using m states of modulation at a transmitting side;

a soft-decision bit calculating unit determining a soft-decision bit value by calculating log likelihood ratios (LLRs) for m bits of the received QAM modulated signal; and

a signal decoding unit restoring the received QAM modulated signal based on the determined soft-decision bit value,

wherein the soft-decision bit calculating unit defines a log likelihood ratio calculation equation by approximating soft-decision boundary points of constellation points for m bits of non-square QAM having odd bits, respectively, and

wherein the soft-decision bit calculating unit calculates a log likelihood ratio for a third bit by using an equation given below;

2. The apparatus of claim 1, wherein the soft-decision bit calculating unit calculates a log likelihood ratio for a first bit by using an I channel value.

3. The apparatus of claim 1, wherein the soft-decision bit calculating unit calculates a log likelihood ratio for a second bit by using a Q channel value.

4. The apparatus of claim 1, wherein the soft-decision bit calculating unit calculates a log likelihood ratio for a fourth bit by using an equation given below:

5. The apparatus of claim 1, wherein the soft-decision bit calculating unit calculates a log likelihood ratio for a fifth bit by using an equation given below:

6. The apparatus of claim 1, wherein the soft-decision bit calculating unit calculates a log likelihood ratio for an even numbered bit of a sixth bit or more by using an equation given below:

7. The apparatus of claim 1, wherein the soft-decision bit calculating unit calculates a log likelihood ratio for an odd numbered bit of a seventh bit or more by using an equation given below:

8. A method for soft-decision demodulating in non-square quadrature amplitude modulation, the method comprising:

receiving a quadrature amplitude modulation (QAM) signal modulated using m states of modulation at a transmitting side;

defining a log likelihood ratio calculation equation by approximating soft-decision boundary points of constellation points for m bits of non-square QAM having odd bits, respectively;

calculating log likelihood ratios (LLRs) for m bits of the received QAM modulated signal by using the defined log likelihood ratio calculation equation;

determining soft-decision bit values based on the calculated log likelihood ratios; and

restoring the received QAM modulated signal based on the determined soft-decision bit value,

wherein in the calculating of the log likelihood ratios (LLRs) for m bits, a log likelihood ratio for a third bit is calculated by using an equation given below;

9. The method of claim 8, wherein in the calculating of the log likelihood ratios (LLRs) for m bits, a log likelihood ratio for a first bit is calculated by using an I channel value.

10. The method of claim 8, wherein in the calculating of the log likelihood ratios (LLRs) for m bits, a log likelihood ratio for a second bit is calculated by using a Q channel value.

11. The method of claim 8, wherein in the calculating of the log likelihood ratios (LLRs) for m bits, a log likelihood ratio for a fourth bit is calculated by using an equation given below:

12. The method of claim 8, wherein in the calculating of the log likelihood ratios (LLRs) for m bits, a log likelihood ratio for a fifth bit is calculated by using an equation given below:

13. The method of claim 8, wherein in the calculating of the log likelihood ratios (LLRs) form bits, a log likelihood ratio for an even numbered bit of a sixth bit or more is calculated by using an equation given below:

14. The method of claim 8, wherein in the calculating of the log likelihood ratios (LLRs) for m bits, a log likelihood ratio for an odd numbered bit of a seventh bit or more is calculated by using an equation given below:

15. An apparatus for soft-decision demodulating in non-square quadrature amplitude modulation, the apparatus comprising:

a signal receiving unit receiving a quadrature amplitude modulation (QAM) signal modulated using m states of modulation at a transmitting side;

a soft-decision bit calculating unit determining a soft-decision bit value by calculating log likelihood ratios (LLRs) for m bits of the received QAM modulated signal; and

a signal decoding unit restoring the received QAM modulated signal based on the determined soft-decision bit value,

wherein the soft-decision bit calculating unit defines a log likelihood ratio calculation equation by approximating soft-decision boundary points of constellation points for m bits of non-square QAM having odd bits, respectively, and

wherein the soft-decision bit calculating unit calculates a log likelihood ratio for a fourth bit by using an equation given below;