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

The Korean Institute of Commucations and Information Sciences (한국통신학회)
권호 표지

Joint Estimation and Compensation for Frequency Selective IQ Imbalance in OFDM Systems

OFDM 시스템에서의 주파수 선택적 IQ 불균형의 추정 및 보상

  • 진영환 (충남대학교 전자전파정보통신공학과 이동멀티미디어통신 연구실) ;
  • 김혜진 (충남대학교 전자전파정보통신공학과 이동멀티미디어통신 연구실) ;
  • 김직동 (정보통신부) ;
  • 안재민 (충남대학교 전자전파정보통신공학과 이동멀티미디어통신 연구실)
  • Published : 2008.03.31
Download PDF
⟨ Previous Next ⟩

Abstract

Orthogonal Frequency Division Multiplexing (OFDM) systems utilizing direct conversion receiver suffer from frequency selective (FS) and frequency independent (FI) phase and gain imbalances caused by imperfect local oscillator and low pass filter. In this paper, we analyze the impacts of the transmit/receive IQ imbalances on the system and propose the estimation and compensation schemes for those imbalances. The preamble signals coded by Alamouti scheme in the frequency domain could be used in the estimation of relatively large IQ imbalances with FS and FI characteristics and the estimation results are used for the compensation of distortions caused by the FI and FS IQ imbalances. The optimal maximum likelihood (ML) receiver or suboptimal ordered successive interference cancallation (OSIC) receiver utilizing the estimation results show symbol error rate (SER) performance improvement compared to zero-forcing (ZF) technique due to diversity gain inherent in the frequency domain IQ imbalances combined with the frequency selective channels.

직접변환 수신기를 사용하는 OFDM (Orthogonal Frequency Division Multiplexing) 시스템의 경우 로컬 오실 레이터 및 저역통과 필터에 의해 발생하는 주파수 선택적 또는 비선택적 특성을 갖는 위상 및 이득 불균형으로 인해 성능 저하가 발생한다. 본 논문에서는 주파수 선택적 또는 비선택적 특성을 갖는 송수신기 IQ 불균형 성분들이 시스템에 초래하는 영향을 분석하고, 동시에 이 성분들을 추정 및 보상하는 방안을 제시하였다. 주파수 영역에서 Alamouti 코딩된 프리엠블을 사용할 경우 채널 성분 뿐만아니라 IQ 불균형 성분까지도 정확히 추정 및 보상할 수 있다. IQ 불균형이 존재하는 수신 신호에 대해 ML(Maximum Likelihood) 또는 OSIC(Ordered Successive Interference Cancellation) 신호 검출 기법을 이용하여 SER (Symbol Error Rate) 성능검증을 통해 주파수 선택적 채널 계수와 송수신 IQ 불균형 성분의 결합에 의하여 초래되는 다이버시티 이득으로 인해 기존의 간섭억제 기법인 ZF (Zero-forcing) 기법에 비해 성능향상이 있음을 보인다.

Keywords

References

  1. B.Razavi, RF Microelectronics, Prentice Hall, NJ, 1998
  2. J. Tubbax, B. Come, L. Van der Perre, S. Donnay, M. Engels, M. Moonenm and H. De Man, "Joint compensation of IQ imbalance and frequency offset in OFDM systems," in Proc. of IEEE Radio and Wireless Conference, pp.39-42, Aug. 2003
  3. M. Valkama, M. Renfors, and V. Koivunen, "Advanced methods for I/Q imbalance compensation in communication receivers," IEEE Transactions on Wireless Communications, vol.10, pp. 673-680, Mar. 2001
  4. A. Tarighat and A. H. Sayed, "On the baseband compensation of IQ imbalances in OFDM systems," in Proc. of IEEE International Conference on Acoustics, Speech and Signal Processing, vol. 4, pp. 1021, June 2004
  5. M. Valkama, M. Renfors, anmd V. Koivunen, "Compensation of frequency-selective I/Q imbalances in wideband receivers: models and algorithms," in Proc. of IEEE Third Workshop on Signal Processing Advances in Wireless Communications, vol. 10, pp. 673-680, Mar. 2001
  6. K. P. Pun, J. E. Franca, C. Aceredo-Leme, C. F. Chan, and C. S. Choy, "Correction of frequency- dependent I/Q mismatches in quadrature receivers," Electronic Letters, vol.37, pp. 673-680, Nov. 2001 https://doi.org/10.1049/el:20010448
  7. G. Xing, M. Shen, and H. Liu, "Frequency offset and I/Q imbalance compensation for direct- conversion receivers," IEEE Transactions on Wireless Communications, vol. 4, pp. 673-680, March 2005 https://doi.org/10.1109/TWC.2004.842969
  8. Tommi M. Ylamurto, "Frequency domain IQ imbalance correction scheme for orthogonal frequency division multiplexing (OFDM) systems," in Proc. of IEEE Wireless Communications and Networking, vol. 1, pp. 20-25, March 2003
  9. A. Schuchert and R. Hasholzner, "A novel IQ imbalance compensation scheme for the reception of OFDM signals," IEEE Transactions on Consumer Electronics, vol.47, pp. 313, Aug. 2001 https://doi.org/10.1109/30.964115
  10. H. Kamata, K. Sakaguchi, and K. Arakai, "An effective IQ imbalance compensation scheme for MIMO-OFDM communication system," in Proc. of Personal, Indoor and Mobile Radio Communications, vol. 1, pp. 181-185, Sept. 2005
  11. A. Tarughat and A. H. Sayed, "OFDM systems with both transmitter and receiver IQ imbalances," in Proc. of Signal Processing Advances in Wireless Communications, pp.735-739, June 2005
  12. J. Lin and E. Tsui, "Joint adaptive transmitter/ receiver IQ imbalance correction for OFDM systems," in Proc. of Personal, Indoor and Mobile Radio Communications, vol. 2, pp. 1511-1518, Sept. 2004
  13. E. Lopez-Estraviz, S. De Rore, F. Horlin, A. Boyrdoux, and L. Van der Perre, "Pilot design for joint channel and frequency-dependent transmit/ receive IQ imbalance estimation and compensation in OFDM-based tranceivers," in Proc. of IEEE International Conference on Communications, pp.4861-4866, June 2007
  14. 진영환, 권지현, 이유로, 안재민, "I/Q 불균형에 의하여 왜곡된 OFDM 시스템에서의 다이버시티 이득 획득 기법," 한국통신학회 논문지, Vol.31, pp. 1205-1213, Dec. 2006