An Efficient CSI Feedback Scheme for Dual-Polarized Massive MIMO

As an effective solution to the tradeoff between array size and the number of antenna elements, dual-polarization antenna is widely utilized in massive MIMO systems. However, the existing channel state information (CSI) feedback schemes are not suitable for dual-polarized massive MIMO as they ignore the polarization leakage between the polarization directions, causing significant performance degradation. To facilitate accurate channel acquisition, this paper proposes a practical channel model for dual-polarized massive MIMO by taking polarization leakage into consideration. The model formulates the channel as the sum of two components, i.e., the ideal polarization channel and the polarization leakage channel between the polarization directions. Based on the channel model, the eigenvector structures of both the ideal polarization channel and the polarization leakage channel are analyzed. Moreover, two novel CSI feedback schemes are also designed, i.e., explicit feedback scheme (EFS) and implicit feedback scheme (IFS). In EFS, the parameters determining the eigenvectors of the two channels are fed back explicitly, while the two channels are fed back using predetermined codebook in IFS. Extensive link level and system level simulations are conducted to validate the performance of the proposed schemes and the results show that they significantly outperform the existing CSI feedback schemes.