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

The Korean Institute of Commucations and Information Sciences (한국통신학회)
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Retransmission Scheme with Equal Combined Power Allocation Using Decoding Method with Improved Convergence Speed in LDPC Coded OFDM Systems

LDPC로 부호화된 OFDM 시스템에서 수렴 속도를 개선시킨 복호 방법을 적용한 균등 결합 전력 할당 재전송 기법

  • 장민호 (울산과학대학교 전기전자공학부)
  • Received : 2013.04.29
  • Accepted : 2013.09.11
  • Published : 2013.09.30
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Abstract

In this paper, we introduce the low-density parity-check (LDPC) coded orthogonal frequency division multiplexing (OFDM) subframe reordering scheme for achieving equal combined power allocation in type I hybrid automatic repeat request (H-ARQ) systems and analyze the performance improvement by using the channel capacity. Also, it is confirmed that the layered decoding for subframe reordering scheme in H-ARQ systems gives faster convergence speed. It is verified from numerical analysis that a subframe reordering pattern having larger channel capacity shows better bit error rate (BER) performance. Therefore the subframe reordering pattern achieving equal combined power allocation for each subframe maximizes the channel capacity and outperforms other subframe reordering patterns. Also, it is shown that the subframe reordering scheme for achieving equal combined power allocation gives better performance than the conventional Chase combining scheme without increasing the decoding complexity.

본 논문은 type I 혼합-자동 반복 요구 (hybrid automatic repeat request: H-ARQ) 시스템에서 저밀도 패리티검사 (low-density parity-check: LDPC)로 부호화된 직교 주파수 분할 다중화 (orthogonal frequency division multiplexing: OFDM) 서브프레임의 전송 순서를 균등 결합 전력이 할당되도록 조정한 재전송 방법을 기초로 성능 개선을 채널 용량을 사용하여 분석하고, 계층 복호 방법을 적용하여 H-ARQ 재전송 기법의 수렴 속도 개선을 확인한다. 구체적으로 임의의 서브프레임 재전송 패턴에 대하여 채널 용량이 클수록 비트오류율 (bit error rate: BER) 성능도 우수하다는 사실을 검증한다. 그러므로 각 서브프레임에 대하여 균등 결합 전력 할당을 보장하는 서브프레임 재전송 패턴은 채널 용량을 최대로 하며, 임의의 다른 서브프레임 전송 순서 조정을 통한 재전송 패턴보다 성능이 우수하다. 결국 균등 결합 전력 할당을 만족하도록 서브프레임 순서를 조정하는 재전송 방법은 기존 체이스 결합 (Chase combining)보다 복호 복잡도를 증가시키지 않으면서도 주목할 만한 성능 개선을 보인다.

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