Journal of the Institute of Electronics Engineers of Korea TC (대한전자공학회논문지TC)

The Institute of Electronics and Information Engineers (대한전자공학회)
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Adaptive Bit-Interleaved Coded OFDM over Time-Varying Channels

시변 채널에서 Bit-Interleaved Coded OFDM을 위한 적응 변조 기법

  • Published : 2009.01.25
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Abstract

When adapting the transmitter to the channel state information(CSI), improved transmission is possible compared to the open loop system where no CSI is provided at the transmitter. However, since the perfect channel information is rarely available at the transmitter, the system design based on the partial CSI becomes an important factor. Especially, in mobile environments, the consideration for the outdated CSI should be applied for mitigating the performance degradation. In this paper, we propose a robust adaptive modulation and coding scheme for bit-interleaved coded orthogonal frequency division multiplexing over time-varying channels. With reasonable feedback overhead, the proposed scheme shows the enhanced performance by compensating for the outdated CSI due to Doppler spread. Simulation results confirm that the performance gain is achieved by applying an accurate BER estimation method.

송신 단에서 채널 상태 정보를 알고 있는 폐루프 시스템은 개방 루프 시스템에 비하여 더 효율적인 전송을 수행할 수 있다. 그러나 실제 시스템은 제한된 피드백 채널을 가지므로 송신단에서 완벽한 채널 정보를 알 수 없으며, 따라서 부분 채널 정보를 활용하는 시스템의 설계가 중요한 요소로 부각되고 있다. 특히, 모바일 환경에서는 사용자의 이동성으로 인하여 채널 상태가 유동적으로 변화하며 이는 성능의 열화를 초래한다. 본 논문에서는 비트 인터리버와 결합한 부호화된 직교 주파수 다중 분할(BIC-OFDM; Bit-Interleaved Coded Orthogonal Frequency Division Multiplexing) 시스템을 위하여 채널 변화에 적절히 대응하는 적응 변조 코딩 기법을 제안한다. 합리적인 피드백 정보량을 통해, 제안하는 기법은 도플러 확산에 의한 채널 변화를 보상하여 향상된 성능을 제공한다. 실험 결과를 통해 제안하는 기법이 정확한 비트 에러율의 추정을 통한 성능 이득을 가짐을 확인한다.

Keywords

References

  1. IEEE 802.11, Wireless LAN medium access control (MAC) physical layer (PHY) specifications, amendment Ⅰ: High speed physical layer in the 5-GHz band, July 1999
  2. A. J. Goldsmith and S.-G. Chua, "Variable-rate variable power MQAM for fading channels," IEEE Transactions on Communications, vol. 45, pp. 1218-1230, October 1997 https://doi.org/10.1109/26.634685
  3. K.-B. Song, A. Ekbal, S. T. Chung, and J. M. Cioffi, "Adaptive modulation and coding (AMC) for bit-interleaved coded OFDM (BIC-OFDM)," in Proc. Globecom '04, vol. 6, pp. 3197-3201, Dallas, USA, June 2004
  4. C. K. Sung and I. Lee, "Adaptive bit-interleaved coded OFDM with reduced feedback information," IEEE Transactions on Communications, Vol.55, No.9, pp.1649-1655, September 2007 https://doi.org/10.1109/TCOMM.2007.904361
  5. G. Caire, G. Taricco, and E. Biglieri, "Bit-interleaved coded modulation," IEEE Transactions on Information Theory, vol. 44, pp. 927-946, May 1998
  6. J. Hagenauer, "Rate-compatible punctured convolutional codes and their applications," IEEE Transactions on Communications, vol. 36, pp. 389-399, April 1988 https://doi.org/10.1109/26.2763
  7. A. G. Fabregas, A. Martinez, and G. Caire, "Error probability of bit-interleaved coded modulation using Gaussian Approximation," in Proc. of the Conf. on Information Science and Systems, Princeton, USA, March 2004
  8. P. Xia, S. Zhou, and G. B. Giannakis, "Adaptive MIMO-OFDM based on partial channel state information," IEEE Transactions of Signal Processing, vol. 52, pp. 202-213, January 2004 https://doi.org/10.1109/TSP.2003.819986
  9. W. C. Jakes, Microwave mobile communications, IEEE Press, 1974
  10. P. Frenger, P. O. Tony, and A. Svensson, Multi-rate convolutional codes, Tech. Rep. Chalmers University of Uechnology, 1998
  11. R. Gozali, R. M. Buehrer, and B. D. Woerner, "On the performance of scheduling over space-time architectures," in Proc. VTC 02, vol. 1, pp. 415-419, Vancouver, Canada, Sep. 2002