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

The Korean Institute of Commucations and Information Sciences (한국통신학회)
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PAPR Reduction in Limited Feedback MIMO Beeamforming OFDM Systems

제한된 되먹임의 송신 빔성형 MIMO OFDM 시스템에서 PAPR 감소 기법

  • 신준우 (한국과학기술원 전자전산학과 디지털통신 연구실) ;
  • 정의림 (한국과학기술원 전자전산학과 디지털통신 연구실) ;
  • 이용훈 (한국과학기술원 전자전산학과 디지털통신 연구실)
  • Published : 2007.08.31
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Abstract

High peak-to-average power ratio(PAPR) is one of serious problems in the orthogonal frequency division multiplexing(OFDM) systems. This paper proposes a PAPR reduction technique for limited feedback multiple input multiple output(MIMO) OFDM systems. The proposed method is based on the null space of the MIMO channel where a dummy signal is made in the channel's null space and then, subtracted from the original signal to reduce the PAPR. First, we show that a problem occurs when the existing method is directly applied to limited feedback MIMO case. Then, a weight function for the dummy signal is proposed to mitigate the degradation of the receiver performance while still reducing PAPR significantly. The weight function is derived from a constrained nonlinear optimization problem to minimize the mean square error between the received signal and its ideal signal. Simulation results shows that the proposed technique provides about 2.5dB PAPR reduction with 0.2dB bit-error probability loss.

높은 주파수 효율 때문에 무선 통신에 널리 쓰이고 있는 직교 주파수 분할 다중화 방식의(orthogonal frequency division multiplexing: OFDM) 문제점 중 하나는 높은 첨두대평균 전력비(peak to average power ratio: PAPR) 이다. 본 논문에서는 제한된 되먹임 정보를 가지는 송신 다중 안테나(multiple input single output: MISO) 빔성형 OFDM(beamforming OFDM) 시스템을 위한 PAPR 감소 기법을 제안한다. 제안된 방식은 채널의 영공간(null space)에서 생성된 부가신호를 원 신호에 더하여 PAPR을 줄이는 방법에 기반한다. 먼저 전체 채널 되먹임을 가정한 기존의 시스템을 부분 채널 정보 되먹임 시스템에 적용할 때의 문제점을 파악하고, 이를 바탕으로 수신 성능 열화를 줄이면서 PAPR을 감소시키는 부가 신호에 대한 가중 함수를 제안한다. 가중 함수는 수치적으로 구하며 컴퓨터 모의 실험을 통해 제안된 방식이 비트오류율(bit error rate: BER) 성능 손실은 거의 없으면서 2.5dB 정도의 PAPR감소 효과를 얻을 수 있음을 보인다.

Keywords

References

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