The Impact of IQ Imbalance on the BER of Adaptive Modulation in the MIMO System

The effect of IQ imbalance on adaptive MQAM modulation in MIMO systems with direct conversion receivers is investigated in this paper. A continues power، discrete rate adaptive modulation scheme in using MIMO system with perfect channel information in both transmitter and receiver is considered. The selected adaptation mechanism changes the transmit power and transmit constellation size under an average transmit power and instantaneous bit error rate (BER) constraints to obtain the maximum average spectral efficiency. First، a closed from expression for the BER of MQAM modulation under the effect of IQ imbalance is introduce. Then، the impact of IQ imbalance on the BER of adaptive modulation in MIMO system is studied. This effect is also investigated for the different configuration of trancmit-recive antenna. The analytic results are compared with the Mont Carlo simulation results to verify the analytic expression.