A Novel PMI Feedback Method for EUTRA TDD Systems

This paper proposes a novel method to feedback PMI (precoding matrix index) in EUTRA TDD (Time Division Duplex) systems. The proposed method groups the precoding matrices which have opposite phase rotations into one precoding matrix group and feedback the PGI (precoding group index) to the transmitter. The transmitter will utilize the reciprocal channel state information to recover the selected precoding matrix from the received PGI. Numerical results show that even under very unideal channel reciprocity assumptions, the proposed scheme can save feedback bits without performance loss.