Partially-Connected Hybrid Beamforming for Multi-User Massive MIMO Systems

Abstract

Due to the high power consumption and hardware cost of radio frequency (RF) chains, the conventional fully-digital beamforming will be impractical for large-scale antenna systems (LSAS). To address this issue, hybrid beamforming has been proposed to reduce the number of RF chains. However, the fullyconnected structure assumed in most hybrid beamforming schemes is still cost-intensive. Recently, the partially-connected structure employing notably fewer phase shifters has received considerable attention in both academia and industry. But the design of partially-connected hybrid beamforming has not been fully understood, especially in multiuser systems. In this paper, we directly address the challenging non-convex non-smooth partially-connected hybrid beamforming design problem with individual signal-to-interferenceplus-noise ratio (SINR) constraints and unit-modulus constraints in a multiuser massive multiple-input multiple-output (MIMO) system. An iterative alternating algorithm based on a penalty method is proposed to obtain a stationary point, which inevitably has relatively high computational complexity. Thus, two lowcomplexity algorithms are then proposed by utilizing matrix approximation. Numerical results demonstrate significant performance gains of the proposed algorithms over existing hybrid beamforming algorithms. Moreover, the proposed low-complexity algorithms can achieve near-optimal performance with dramatically reduced computational complexity. INDEX TERMS Massive MIMO, hybrid beamforming, SINR constraints, penalty method, penalty dual decomposition.

Downlink Beamforming for Dynamic Metasurface Antennas

“…The new SINR expression in (32) presents a different optimizable variable θ n,m with a manageable constraint. Consequently, the inputs of the objective function (when F is fixed) in ( 14) must be modified to…”