Near-optimality of the one-step max-sum-rate precoder with MMSE initialization for large downlink multi-user MIMO systems

Our recent study demonstrated that an iterative max-sum-rate (MSR) precoder with MMSE initialization gives an excellent sum-rate performance in downlink multi-user MIMO systems. As the number of transmit antennas increases, two crucial remarks were made: (1) its performance approaches the dirty-paper coding upper-bound and (2) the one-step iteration gives a decent performance. In this paper first, we further illustrate the second observation by looking at the optimality of this one-step max-sum-rate precoder with MMSE initialization (MSR-MMSE-1) for large MIMO systems. This shows that we can get near-optimal performance of the iterative MSR precoder without having to deal with any iteration at all. Then, we compare its sum-rate performance against one from the well-known block diagonalization algorithm (BD). Again, it is found that, when the number of transmit antennas is large enough, MSR-MMSE-1 outperforms BD across all SNR values under consideration.