The Journal of Korean Institute of Communications and Information Sciences (한국통신학회논문지)

The Korean Institute of Commucations and Information Sciences (한국통신학회)
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Design of a Low-Power LDPC Decoder by Reducing Decoding Iterations

반복 복호 횟수 감소를 통한 저전력 LDPC 복호기 설계

  • 이준호 (서강대학교 전자공학과 대학원 CAD & ES연구실) ;
  • 박창수 (서강대학교 전자공학과 대학원 CAD & ES연구실) ;
  • 황선영 (서강대학교 전자공학과 대학원 CAD & ES연구실)
  • Published : 2007.09.30
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Abstract

LDPC Low Density Parity Check) code, which is an error correcting code determined to be applied to the 4th generation mobile communication systems, requires a heavy computational complexity due to iterative decodings to achieve a high BER performance. This paper proposes an algorithm to reduce the number of decoding iterations to increase performance of the decoder in decoding latency and power consumption. Measuring changes between the current decoded LLR values and previous ones, the proposed algorithm predicts directions of the value changes. Based on the prediction, the algorithm inverts the sign bits of the LLR values to speed up convergence, which means parity check equation is satisfied. Simulation results show that the number of iterations has been reduced by about 33% without BER performance degradation in the proposed decoder, and the power consumption has also been decreased in proportional to the amount of the reduced decoding iterations.

LDPC 부호는 4G 이동통신 시스템에 적합한 오류 정정 부호이다. 그러나 알고리듬의 특성상 좋은 BER 성능을 위해서는 반복 복호에 의한 많은 연산량이 요구된다. 본 논문에서는 복호지연과 전력 소모에 대한 복호기의 성능을 증가시키기 위하여 반복 복호 횟수를 줄이는 알고리듬에 대하여 제안한다. 제안된 알고리듬은 현재 LLR 복호값과 이전 LLR 복호값 사이의 변화를 측정하고 변화 방향을 예측하며, 패리티 검사식을 만족시켜 수렴속도를 높이도록 LLR 값의 sign 비트를 반전시킨다. 실험결과, 제안한 방법은 BER 성능의 감소 없이 반복 복호 횟수를 약 33% 정도 줄이는 것이 가능하며 감소된 반복 복호 횟수에 비례하여 소모 전력도 감소시킬 수 있다.

Keywords

References

  1. 황승구, '4세대 이동통신 무선 전송 기술 동향,' 주간기술동향, 통권 1168호, 2004년 10월
  2. T. Richardson and R. Urbanke, 'The Renaissance of Gallager's Low-Density Parity-Check Codes,' IEEE Communication Magazine, vol. 41, no. 8, pp. 126 131, Aug. 2003
  3. T. Richardson and R. Urbanke, 'The Capacity of Low-density Parity-check Codes under Message-passing,' IEEE Trans. Inform. Theory, vol. 47, no. 2, pp. 599-618, Feb. 2001 https://doi.org/10.1109/18.910577
  4. D. MacKay and R. Neal, 'Near Shannon Limit Performance of Low Density Parity Check Codes,' IEE Electronics Letters, vol. 32, no. 18, pp. 1645-1646, Aug. 1996 https://doi.org/10.1049/el:19961141
  5. R. Gallager, 'Low-Density Parity-Check Codes,' IRE Trans. Inform. Theory, vol. IT-8, pp. 21-28, Jan. 1962
  6. D. Mackay, 'Good Error-correcting Codes Based on Very Sparse Matrices,' IEEE Trans. Inform. Theory, vol. 45, no. 2, pp. 399-431, Mar. 1999 https://doi.org/10.1109/18.748992
  7. R. Tanner, 'A Recursive Approach to Low Complexity Codes,' IEEE Trans. Inform. Theory, vol. 27, no. 5, pp. 533-547, Sep. 1981 https://doi.org/10.1109/TIT.1981.1056404
  8. V. Zyablov and M. Pinsker, 'Estimation of the Error Correction Complexity of Gallager Low Density Parity Codes,' Problems of Information Transmission, vol. 11, no. 1, pp. 23-26, Jan. 1976
  9. A. Blankby and C. Howland, 'A 690-mW 1-Gb/s 1024-b, Rate-1/2 Low-Density Parity-Check Code Decoder,' IEEE J. Solid-State Circuits, vol. 37, no. 3, pp. 404-412, Mar. 2002 https://doi.org/10.1109/4.987093
  10. V. Sorokine, F. Kschischang, and S. Pasupathy, 'Gallager Codes for CDMA Applications - Part II: Implementations, Complexity, and System Capacity,' IEEE Trans. Communications, vol. 48, no. 11, pp. 1818-1828, Oct. 2000 https://doi.org/10.1109/26.886472
  11. S. Hong and W. Stark, 'Design and Implementation of a Low Complexity VLSI Turbo-code Decoder Architecture for Low Energy Mobile Wireless Communications,' J. VLSI Signal Processing System, vol. 24, no. 1, pp. 43-57, Feb. 2000 https://doi.org/10.1023/A:1008114510995
  12. N. Wiberg, H. Loeliger, and R. Kotter, 'Codes and Iterative Decoding on General Graphs,' in Proc. Information Theory, pp. 468, Sep. 1995
  13. R. Morelos-Zaragoza, The Art of Error Correcting Coding. Wiley: New York, 2002
  14. J. Fan, Constrained Coding and Soft Iterative Decoding. Kluwer Academic Pub.: Norwell, MA, 2001
  15. F. Kshischang and B. Frey, 'Iterative Decoding of Compound Codes by Probability Propagation in Graphical Models,' IEEE Journal on Selected Area in Communications, vol. 16, no. 2, pp. 219-230, Feb. 1998 https://doi.org/10.1109/49.661110
  16. B. Sklar, Digital Communications: Fundamental and Applications. 2nd Edition, Prentice Hall Inc.,: New Jersey, 2001