Cell-Edge-Aware Precoding for Downlink Massive MIMO Cellular Networks

摘要

We propose a cell-edge-aware (CEA) zero forcing (ZF) precoder that exploitsthe excess spatial degrees of freedom provided by a large number of basestation (BS) antennas to suppress inter-cell interference at the mostvulnerable user equipments (UEs). We evaluate the downlink performance ofCEA-ZF, as well as that of a conventional cell-edge-unaware (CEU) ZF precoderin a network with random base station topology. Our analysis and simulationsshow that the proposed CEA-ZF precoder outperforms CEU-ZF precoding in terms of(i) aggregate per-cell data rate, (ii) coverage probability, and (iii)95%-likely, or edge user, rate. In particular, when both perfect channel stateinformation and a large number of antennas N are available at the BSs, wedemonstrate that the outage probability under CEA-ZF and CEU-ZF decay as 1/N^2and 1/N, respectively. This result identifies CEA-ZF as a more effectiveprecoding scheme for massive MIMO cellular networks. Our framework also revealsthe importance of scheduling the optimal number of UEs per BS, and confirms thenecessity to control the amount of pilot contamination received during thechannel estimation phase.