Performance Improvement for Nonchoherent DS/CDMA Reverse Links using Channel Estimation and Multiuser Detection

비동기 복조 DS/CDMA 역방향 링크에서 채널 추정 및 다중 사용자 검파를 이용한 성능 개선

  • 홍대기 (연세대학교 공과대학 전기전자공학과) ;
  • 윤석현 (연세대학교 공과대학 전기전자공학과) ;
  • 홍대식 (연세대학교 공과대학 전기전자공학과) ;
  • 강창언 (연세대학교 공과대학 전기전자공학과)
  • Published : 2001.08.01

Abstract

In this paper, we propose maximum likelihood (ML) decision feedback channel estimation (DFCE) for M-ary orthogonal modulation in direct sequence/code division multiple access (DS/CDMA) systems. The proposed DFCE uses the maximum combiner output in a RAKE receiver as decision feedback information, enabling M-ary orthogonal signals to be demodulated coherently and a RAKE receiver to use a em maximal ration combining (MRC) scheme. However, the performance of the proposed DFCE in the multiuser environment is severely degraded due to multiple access interference (MAI). To overcome this problem, a multistage parallel interference cancellation (PIC) scheme is combined with the proposed DFCE for multiuser environments. Accurate knowledge of the channel coefficient estimated by the proposed DFCE is used to regenerate the signal of each user for the multistage PIC scheme. According to the results of our simulations, the performance of coherent demodulation using the proposed system is significantly improved in comparison with conventional noncoherent demodulation.

Keywords

References

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