A Comparative Study for Downlink Multi-User MIMO Systems

In this paper, precoding methods used in downlink multi-user, multi-input multi-output systems (downlink MU-MIMO) are investigated. Precoding methods provide inter-user interference management and are designed to maximize the achievable sum rate. Downlink MU-MIMO systems can be underloaded, critically loaded or overloaded depending on the number of antennas at the base station and users and the number of users. This study provides a comparison between the generalized power iteration precoding (GPIP) (which is newly proposed in the literature) with the minimum mean square error precoding (MMSE). It is observed that the GPIP method results in similar or worse sum rate performance than the MMSE method in all load cases. Moreover, the MMSE method has lower complexity.