Novel Multi-cell Precoding Schemes for TDD Massive MIMO Systems

Two novel multi-cell precoding schemes, maximum ratio combining precoding with base station cooperation (MRC-BSC) and zero forcing precoding with BS cooperation (ZF-BSC), are proposed for time division duplex massive multiple-input multiple-output system. By making full use of other cells (not target cell) channel estimate information and changing the matrix structure of classical single-cell maximum ratio combining (MRC) precoding and zero forcing (ZF) precoding, proposed precoding schemes are obtained to reduce inter-cell interference with low complexity. The expressions of lower bound per-user achievable rate of proposed precoding schemes for different uplink pilot reuse factors situations are derived through theoretic analysis. Simulation results demonstrate that the proposed MRC-BSC and ZF-BSC can always achieve higher rates than single-cell MRC precoding and ZF precoding. For each precoding scheme, the downlink achievable rate can be improved greatly when enlarging the uplink pilot reuse factor. In addition, the proposed precoding schemes does not affect (or even improve) other cells' performance while improving the target cell's performance.