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

The Korean Institute of Commucations and Information Sciences (한국통신학회)
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Frequency Offset Estimation for OFDM-based Cognitive Radio Systems in Non-Gaussian Impulsive Channels

비정규 충격성 잡음에서 OFDM 기반 인지 무선 시스템을 위한 주파수 옵셋 추청 기법

  • 송정한 (성균관대학교 정보통신공학부) ;
  • 이영포 (성균관대학교 정보통신공학부) ;
  • 송익호 (한국과학기술원 전기및전자공학과) ;
  • 윤석호 (성균관대학교 정보통신공학부)
  • Received : 2010.11.02
  • Accepted : 2010.12.21
  • Published : 2011.01.31
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Abstract

Cognitive radio (CR) systems have received significant interest as a promising solution to the spectral shortage problem through efficient use of the frequency spectrum by opportunistically exploiting unlicensed frequency bands. Orthogonal frequency division multiplexing (OFDM) is widely regarded as a highly promising candidate for CR systems. However, the frequency bands used by CR systems are expected to suffer from non-Gaussian noise, which considerably degrades the performance of the conventional OFDM carrier frequency offset (CFO) estimation schemes. In this paper, robust CFO estimation schemes for OFDM-based CR systems in non-Gaussian channels are proposed. Simulation results demonstrate that the proposed estimators offer robustness and substantial performance improvement over the conventional estimator.

주파수 부족 문제를 해결하기 위하여 무선 통신 환경을 인지하여 활용할 수 있는 인지 무선(cognitive radio: CR) 시스템이 크게 주목받고 있다. 이러한 CR 시스템을 위한 변조 기법으로서 (orthogonal frequency division multiplexing: OFDM) 기술이 가장 유력하게 제안되고 있다. 하지만 CR 시스템이 사용되는 주파수 대역에는 인위적인 충격성 잡음, 간섭 등으로 인한 비정규 잡음이 존재하며, 이로 인해 정규 잡음을 기반으로 하는 OFDM 주파수 옵셋 추정 기법들은 심각한 성능 저하를 겪는다. 본 논문에서는 OFDM 기반 CR 시스템을 위한 최대 우도 주파수 옵셋 추정 기법을 제안하였으며, 또한 적은 개수의 시행 값을 사용함으로써 낮은 복잡도를 갖는 준최적 주파수 옵셋 추정 기법을 제안하였다. 모의실험을 통해 제안한 추정 기법들이 기존 추정 기법보다 비정규 충격성 잡음 환경에서 강인하고, 우수한 성능을 가짐을 확인하였다.

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