The Journal of the Institute of Internet, Broadcasting and Communication (한국인터넷방송통신학회논문지)

The Institute of Internet, Broadcasting and Communication (한국인터넷방송통신학회)
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An Enhanced Scheme with CFO and SFO in OFDMA system

OFDMA 시스템에서 SFO와 CFO 저감 기법에 관한 연구

  • Lee, Young-Gwang (Dept. of Electronic & Electrical Engineering, Hongik University) ;
  • Lee, Kyu-Seop (Dept. of Electronic & Electrical Engineering, Hongik University) ;
  • Choi, Gin-Kyu (Dept. of Electronic & Electrical Engineering, Hongik University)
  • 이영광 (홍익대학교 전자전산공학과) ;
  • 이규섭 (홍익대학교 전자전산공학과) ;
  • 최진규 (홍익대학교 전자전산공학과)
  • Received : 2014.01.01
  • Accepted : 2014.02.07
  • Published : 2014.02.28
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Abstract

Recently, orthogonal frequency-division multiplexing(OFDM), with clusters of subcarriers allocated to different subscribers(often referred to as OFDMA), has gained much attention for its ability in enabling multiple-access wireless multimedia communications. In such systems, carrier frequency offsets (CFOs) can destroy the orthogonality among subcarriers. And the mismatch in sampling frequencies between transmitter and receiver can lead to serious degradation due to the loss of orthogonality between the subcarriers. As a result, multiuser interference (MUI) along with significant performance degradation can be induced. In this paper, we present a scheme to compensate for the SFOs and CFOs at the base station of an OFDMA system. A novel sampling frequency offset estimation algorithm is proposed, which is based on the repetition of a symbol at the communication start-up. Then, circular convolutions are employed to generate the interference after the discrete Fourier transform processing, which is then removed from the original received signal to increase the signal to interference power ratio(SIR). Simulation result shows that the proposed scheme can improve system performance.

최근 OFDM시스템의 부반송파의 묶음을 각각 다른 사용자에게 할당하는 다중접속 기법인 OFDMA 기법이 멀티미디어 통신의 무선 다중 접속 능력 때문에 큰 주목을 받고 있다. 기존의 OFDM 통신 시스템에서 채널을 통과한 수신신호를 복조할 때 여러 가지 방법을 사용하는데, 채널을 통과할 때 CFO(carrier frequency offset)와 샘플링을 할 때 SFO(sampling frequency offset)이 생기게 된다. 이러한 주파수 오프셋 때문에 복조를 할 때 정확한 신호를 검출 할 수 없게 된다. 본 논문에서는 다중 사용자 환경인 OFDMA에서 이 CFO와 SFO에 대한 영향력을 감소하는 방법을 제시한다. 또한 CFO로 인하여 MUI(multi user interface)가 생기는데 이는 서로 다른 사용자들 간의 간섭으로 인해 생기는 것으로 일종의 잡음(nosie)라고 볼 수 있다. 이 MUI에 관한 것을 재귀적인 알고리즘을 사용하여 상쇄(cancellation)하고 또 CFO와 SFO에 대한 값을 추정하고 최소화하여 기존의 CFO와 SFO가 일어난 OFDM의 신호에 대한 검출보다 더 좋게 검출을 할 수 있는 알고리즘을 제안한다.

Keywords

References

  1. P. H. Moose, "A Technique for Orthogonal Frequency Division Multiplexing Frequency Offset Correction", IEEE Trans. on Comm., Vol. 42, No. 10, pp. 2908-2914, Oct. 1994 https://doi.org/10.1109/26.328961
  2. Juinn-Horng Deng and Yi-Hsin Lin, "An Iterative Receiver Design with CFO, SFO, Channel Estimation and Equalization for OFDM Systems over Multipath Fading Channels" ICACT, 2013 15th International Conference.
  3. Jinyoung An, Sangchoon Kim, "Performance Analysis of UWB MIMO System with Prerake Transmit Processing", Journal of Korean Institute of Information Technology, Vol. 8, No. 9, pp. 43-50, Sep. 2009.
  4. M. Sliskovic, "Sampling frequency offset estimation and correction in OFDM systems", Electronics, Circuits and Systems, 2001. ICECS 2001. The 8th IEEE International Conference on Volume 1.
  5. Joong-Soo Lim, "An Accurate Direction Finding Technology Using a Phase Comparison and Time Difference of Arrival", Journal of the Korea Academia-Industrial Cooperation Society, Vol. 12, No. 11, pp. 5208-5213, 2011. https://doi.org/10.5762/KAIS.2011.12.11.5208
  6. M. Sliskovic, B. Jeren, "Clock frequency synchronisation in OFDM system for Power line Communications", Proc, 1st Int. Workshop on Image and Signal Processing, Pula, Croatia, pp. 241-246, June 2000.
  7. Defeng (David) Huang, "An interference-cancellation scheme for carrier frequency offset correction in OFDMA Systems" IEEE. Trans. on Comm. Vol. 53, No. 7, pp. 1155-1165, JULY 2005. https://doi.org/10.1109/TCOMM.2005.851558
  8. Juphil Choi, Sang In Cho, Kyu Min Kang and Heon Jin Hong, "Analysis on WiBro Interfering to WLAN under Co-channel in TV White Spaces", IJIBC Vol. 5 No. 1 pp. 1-5, Feb. 2013.
  9. Seung-Gag Lim, "The Performance Comparison of CR-CMA and CM-CMA Adaptive Equalization in 16-QAM Signal", IIBC VOL. 11, No. 3, pp.137-143, June 2011.
  10. J. Choi, C. Lee, H. W. Jung, and Y. H. Lee, "Carrier frequency offset compensation for uplink of OFDM-FDMA systems", IEEE Commun. Lett. vol. 4, no. 12, pp. 414-416, Dec. 2000. https://doi.org/10.1109/4234.898725