Browse > Article

IQ Unbalance Compensation for OPDM Based Wireless LANs  

Kim, Ji-Ho (연세대학교 전기전자공학과 정보통신SoC설계 연구실)
Jung, Yun-Ho (연세대학교 TMS정보기술사업단)
Kim, Jae-Seok (연세대학교 전기전자공학과)
Publication Information
The Journal of Korean Institute of Communications and Information Sciences / v.32, no.9C, 2007 , pp. 905-912 More about this Journal
Abstract
This paper proposes an efficient estimation and compensation scheme of IQ imbalance for OFDM-based WLAN systems in the presence of symbol timing error. Since the conventional scheme assumes perfect time synchronization, the criterion of the scheme used to derive the estimation of IQ imbalance is inadequate in the presence of the symbol timing error and the system performance is seriously degraded. New criterion and compensation scheme considering the effect of symbol timing error are proposed. With the proposed scheme, the IQ imbalance can be almost perfectly eliminated in the presence of symbol timing error. The bit error rate performance of the proposed scheme is evaluated by the simulation. In case of 54 Mbps transmission mode in IEEE 802.11a system, the proposed scheme achieves a SNR gain of 4.3dB at $BER=2{\cdot}10^{-3}$. The proposed compensation algorithm of IQ imbalance is implemented using Verilog HDL and verified. The proposed IQ imbalance compensator is composed of 74K logic gates and 6K bits memory from the synthesis result using 0.18um CMOS technology.
Keywords
IQ imbalance; Symbol timing error; OFDM; Training symbol; WLAN;
Citations & Related Records
연도 인용수 순위
  • Reference
1 T. Pollet, M. Van Bladel, and M. Moeneclaey, 'BER sensitivity of OFDM systems to carrier frequency offset and wiener phase noise', IEEE Transactions on Communications, Vol. 43, No. (2/3/4), pp. 191-193, Feb./Mar./Apr. 1995   DOI   ScienceOn
2 P. H. Moose, 'A technique for orthogonal frequency division mltiplexing frequency offset correction', IEEE Transactions on Communication, vol. 45, no. 12, December 1997
3 S. Fouladifard, H. Shafiee, 'Frequency offset estimation in OFDM systems in presence of IQ imbalance', Proc. of IEEE Conf. on Communication Systems(ICCS) 2002, Vol. 1, pp 214-218, Nov. 2002
4 M. Valkama, M. Renfors, and V. Koivunen. 'Advanced methods for I/Q imbalance compensation in communication receivers', IEEE Transactions on Signal Processing, 49(10): 2335-2344, October 2001   DOI   ScienceOn
5 IEEE 802.11a, Wireless LAN Medium Access Control(MAC) and Physical Layer(PHY) Specifications, 1999
6 S. Mirabbasi and K. Martin, 'Classical and modern receiver architectures', IEEE Comm. Magazine, pp. 132-139, Nov. 2000
7 J. Tubbax, A. Fort, L. Van der Perre, S. Donnay, M. Engels, M. Moonen, H. De Man, 'Joint compensation of IQ imbalance and frequency offset in OFDM systems', GLOBECOM '03, vol. 4, pp. 2365-2369, Dec. 2003
8 T. M. Schmidl and D. C. Cox, 'Robust frequency and timing synchronization for OFDM', IEEE Trans. on Communication, vol 45, no 12, pp. 1613-1621, December, 1997   DOI   ScienceOn
9 J. Heiskala, J. Terry, OFDM Wireless LNAs: A Theoretical and Practrical Guide, Sams, 2001