OFDM channel estimation in the presence of transmitter and receiver I/Q imbalance

In this paper, we consider channel estimation for orthogonal frequency division multiplexing (OFDM) systems when both the transmitter and receiver suffer from in-phase and quadrature-phase (I/Q) imbalance. By exploiting the fact that the block size of an OFDM system is usually larger than the channel order, we propose a new method which can jointly estimate the transmitter and receiver I/Q mismatch and channel response. The estimates of the transmitter and receiver I/Q imbalance parameters are given in a closed form. Using only one arbitrary OFDM block for training, the proposed method can accurately estimate these parameters and a very good performance can be achieved. Simulation results show that the bit error rate (BER) performance of the proposed method is very close to the ideal case where the I/Q mismatch and channel response are perfectly known at the receiver.