Journal of the Korea Institute of Information and Communication Engineering (한국정보통신학회논문지)

The Korea Institute of Information and Commucation Engineering (한국정보통신학회)
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A Study on Reducing PAPR of OFDM Transmit System by Clipping Structural Improvement

Clipping 구조를 개선한 OFDM 전송시스템의 PAPR 감소에 관한 연구

  • 김완태 (한국항공대학교 대학원 정보통신 공학과) ;
  • 조성준 (한국항공대학교 대학원 정보통신 공학과)
  • Published : 2007.08.31
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Abstract

Recently many communication systems ate adapting the OFDM(Orthogonal Frequency Division Multiplexing) for multimedia data services. However, OFDM has some problems that PAPR is increased when sub-carries are summed up with same phases. This problem causes severe signal distortions while the signal is passing through non-linear system such as power amplifier resulting in performance degradation of transmission system. In this paper, we use IF-Clipping method to solve PAPR problem and the signal distortion caused by clipping is limited by use of SAW (Surface Acoustic Wave) filter and power amplifier(TWTA). And we derive the optimal parameter(PAPR, Backoff) values to meet the spectrum mask of WiBro system.

현재의 통신 시스템은 멀티미디어 서비스를 제공하기 위하여 OFDM(Orthogonal Frequency Division Multiplexing) 방식이 주로 쓰이고 있다. 그러나 OFDM 방식은 다수의 부반송파를 사용하므로 부반송파들이 동일위상으로 더해질 때 놀아지는 PAPR(Peak-to-Average Power Ratio)이 문제가 되고 있다. PAPR의 문제는 신호가 전력증폭기와 같은 비선형 소자를 통과할 때 심각한 왜곡을 받게 되므로 전송시스템 성능이 저하된다. 본 논문에서는 PAPR 문제를 해결하기 위해 IF-Clipping 기법을 제안하고, 신호의 clipping에 의해 발생되는 신호의 왜곡을 SAW(Solace Acoustic Wave) 필터와 전력증폭기를 사용하여 제한하였다. 또한 clipping 기법 이용 후 SAW Filter와 전력증폭기를 사용하여 WiBro 시스템의 Spectrum Mask를 만족하는 이상적인 파라메터 값(PAPR, Backoff)을 찾았다.

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References

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