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Design Philosophy of MIMO OFDM system for Underwater Communication

수중 통신 환경을 위한 MIMO-OFDM 시스템 설계

  • Received : 2010.08.06
  • Accepted : 2010.08.17
  • Published : 2011.01.31

Abstract

In this paper, we first analyze the differences of underwater acoustic (UWA) orthogonal frequency division multiplexing (OFDM) systems and conventional terrestrial OFDM system, and give a simple introduction of the backgrounds. By considering the real UWA channel environments, the measured channel data is used to generate the UWA channel model and calculate the relative parameters for underwater OFDM systems. Practical least square (LS) based channel estimation with linear interpolation are adopted to obtain the channel state information (CSI) at receiver side. As multi-input multi-output (MIMO) processing techniques, Alamouti code is implemented and evaluated to perform for space time block coding (STBC) and space frequency block coding (SFBC) for UWA OFDM systems with the MIMO configuration of $2{\times}1$, at the same time, $1{\times}2$ maximum ratio combining (MRC) is performed for the purpose of comparison. The simulation results show that, with perfect channel estimation, SFBC failed to work duo to the serious frequency selectivity of UWA channel environments. When the practical channel estimation is applied, in the case of STBC, the proposed 4-column pilot pattern gives better performance about 7dB than SISO system.

본 논문에서는 수중 통신 환경에서의 Orthogonal Frequency Division Multiplexing (OFDM) 시스템과 지상에서의 일반적인 OFDM 시스템과의 차이점을 분석하고, 실제 측정된 채널 데이터를 사용한 수중 채널 모델을 기반으로 OFDM 파라미터들을 설정하였다. 또한, 선형 보간법을 이용한 least square (LS) 채널 추정기법을 이용하여 채널의 상태 정보를 획득하였다. Alamouti code를 이용한 space-time block code (STBC) 및 space-frequency blcok code (SFBC)를 적용하여 그 성능을 평가 및 분석 하였으며, 동시에 $1{\times}2$ maximum ratio combining (MRC)을 적용하여 성능을 비교 분석 한 결과, SFBC의 경우 수중 채널의 심각한 주파수 선택적 특성으로 인하여 유효한 BER 특성을 보이지 못하였으나, STBC의 경우 4-column 파일럿 구조를 적용하였을 때, SISO 시스템과 비교하여 약 7dB 정도의 향상된 성능을 나타내고 있음을 확인하였다.

Keywords

References

  1. M. Chitre, S. Shahabudeen, and M. Stojanovic, "Underwater acoustic communications and networking: recent advances and future challenges," in Marine Technology Society Journal, vol.42, num.1, pp.103-116, Spring 2008.
  2. M.C. Domingo, "Overview of channel models for underwater wireless communication networks," Physical Commun., vol.1, pp.163-182, 2008. https://doi.org/10.1016/j.phycom.2008.09.001
  3. B. Li, S. Zhou, M. Stojanovic, and L. Freitag, "Pilot-tone based ZP-OFDM demodulation for an underwater acoustic channel," in Proc. IEEE Oceans, Sept. 2006, pp.1-5.
  4. R. Coates, Underwater Acoustic Systems, NewYork: Wiley, 1989.
  5. L. E. Freitag and J. A. Catipovic, "A signal processing system for underwater acoustic ROV communication", in Proc. International Symposium on Unmanned Untethered Submersible Technology, 1989, pp.34-41.
  6. H. K. Yeo, B. S. Sharif, A. E. Adams & O. R. Hinton, "Multiuser detection for time-variant multipath environment", in Proc. of the 2000 International Symposium on Underwater Technology, 2000, pp.399-404
  7. Xiaoka Xu, Gang Qiao, Jun Su, Pengtao Hu and Enfang Sang, "Study on turbo code for multicarrier underwater acoustic communication," in Proc. Wireless Communications, Networking and Mobile Computing, 2008. pp.1-4.
  8. Zhang Lan, Xu Xiaomei, Sun Haixin and Chen Yougan, "Performance analysis of IRA codes for underwater acoustic OFDM communication system," in Proc. Wireless Communications, Networking and Mobile Computing, 2009. pp. 1-4.
  9. Jie Huang, Shengli Zhou and Peter Willett, "Nonbinary LDPC coding for multicarrier underwater acoustic communication," IEEE J. Sel. Areas Commun., vol. 26, no. 9, pp. 1684-1696, Dec. 2008. https://doi.org/10.1109/JSAC.2008.081208
  10. S. Roy, T.M. Duman and V.K. McDonald, "Error rate improvement in underwater MIMO communication using sparse partial response equalization," IEEE J. Ocean. Eng., vol. 34, pp.181-201, Apr. 2009. https://doi.org/10.1109/JOE.2009.2014658
  11. K. Grythe and J.E. Hakegard, "Non-perfect channel estimation in OFDM-MIMO based underwater communication," in Proc. OCEANS 2009-EUROPE, 2009, pp.1-9.
  12. M. Stojanovic, "Adaptive channel estimation for underwater acoustic MIMO OFDM systems," in Proc. of IEEE DSP Workshop, Marco Island, FL, Jan. 2009, pp.132-137.
  13. 김정주, 고상준, 장경희, "WRAN 응용을 위한 하향 링크 무선전송 방식 : OFDMA 상황인식 시스템에서의 적응 부채널 할당 및 고정 빔 형성 기법," 한국통신학회 논문지, vol.31, No.3A, pp. 291-303, 2006. 03.
  14. 선태형, 강승원, 김규현, 장경희, ''IEEE 802.16e OFDMA/TDD 이동국 모뎀의 링크 성능과 복잡도 최적화를 위한 부동 및 고정 소수점 설계,'' 대한전자공학회 논문지, 43권, TC편, 11호, pp. 95-117, 2006. 11.

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