Blind source separation-based multi-user detection for multi-antenna QAM receivers with I/Q imbalances

This paper presents a blind multi-user detection technique for multi-antenna quadrature amplitude modulation (QAM) receivers with Inphase/Quadrature phase (I/Q) imbalances. The estimation of multiple users in the presence of I/Q imbalances is performed by Blind Source Separation (BSS) methods. While the complex-valued signal model for multi-antenna QAM receivers does not lend itself to BSS due to the effect of I/Q imbalances, reformulating the signal model to a real-valued equivalent form enables the application of BSS. The proposed method enables multiple users to share the same bandwidth simultaneously in different geographical locations, and avoids the need for the knowledge of the channel state information. In addition, despite of the presence of I/Q imbalances in all receiver branches, the number of antenna required in the receiver is equal to the number of users. Computer simulations are conducted using the popular Fast-ICA (Independent Component Analysis) algorithm, and the simulation results confirmed the effectiveness of the proposed technique.