LTE-Advanced Multi-User MIMO: Improved Feedback and Precoding Design

This paper considers feedback and precoding design for multi-user MIMO in long term evolution (LTE) and LTE-Advanced systems. We show that LTE precoders are characterized by a diversity loss, mainly attributed to their characteristic of equal gain transmission (EGT). We therefore propose a precoding design based on marginal increase of feedback and show that the performance of multi-user MIMO comes quite close to the lower bound. We claim that the proposed codebook structure is not only restricted to the framework of LTE and LTE-Advanced, but also applicable as a fundamental design guidance for the ongoing standardizations of modern wireless systems.