A Low-Complexity AoA-driven Multi-cell Constant Envelope Precoding for Massive MIMO Systems

This paper deals with the problem of multi-cell precoding in downlink transmission of a massive multiple input multiple output (MIMO) system, where a constant envelope precoding (CEP) construction is employed with the purpose of reducing the implementation cost as well as improving the hardware efficiency. To this end, initially, the optimization problem of multi-cell CEP is formulated in a centralized construction. In the following, the outgoing problem is relaxed such that the equivalent problem would be convex. Furthermore, an iterative distributed structure is proposed where, each iteration involves the precoding in one of the cells. Numerical results demonstrate, from the downlink data rate per user point of view, the performance of the proposed iterative method faces a slight drop in comparison with the general realization of the CEP, while the overall complexity of the system is significantly reduced.