Joint Estimation and Compensation for Frequency Independent and Frequency Selective IQ Imbalances in OFDM Systems

I. Hwang, Y. Jin, H. Kim, and J. Ahn (Korea)


Frequency independent (FI) IQ imbalance, frequency selective (FS) IQ imbalance, estimation and compensation, orthogonal frequency division multiplexing (OFDM).


In this paper, we analyze the effect of IQ (In-phase/ Quadrature-phase) imbalances at both transmitter and receiver of OFDM system and propose the joint estimation and compensation method. Accurate estimation and compensation of IQ imbalance can be achieved in the frequency domain with the Alamouti coded preamble. It is shown that relatively large IQ imbalance can be effectively compensated using the proposed method. In addition, by using a proper receiver scheme can be obtained the additional diversity gain due to transmit IQ imbalance and frequency selective channel. Simulation results on the symbol error rate (SER) performance show that even severe IQ imbalance error could be compensated effectively achieving a SER about 1~2 dB error at the specified SER of 10-3 compared to reference. SER performance with ML (Maximum Likelihood) and OSIC (Ordered Successive Interference Cancellation) receiver show that significant performance gain can be achieved with the diversity gain caused by the IQ imbalances combined with the frequency selective channels.

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