Hybrid Beamforming Design in Multi-Cell MU-MIMO Systems with Per-RF or Per-Antenna Power Constraints

摘要

This work deals with hybrid beamforming for the MIMO Interfering Broadcast Channel (IBC), i.e. the Multi-Input Multi-Output (MIMO) Multi-User (MU) Multi-Cell (MC) downlink (DL) channel. Hybrid beamforming (HBF) is a low complexity alternative for fully digital precoding in Massive MIMO systems. Hybrid architectures involve a combination of digital and analog processing that enables both beamforming and multiplexing gains. We consider BF design by maximizing the Weighted Sum Rate (WSR) for the case of Perfect Channel State Information at the Transmitter (CSIT). We optimize the WSR using minorization and alternating optimization, the result of which is observed to converge fast. The design is proposed for both fully and partially connected analog BF architectures. Moreover, we consider the BF design under realistic scenarios with per-RF (radio frequency) chain or per-antenna power constraints, leading to novel interference leakage aware water filling procedures. Simulation results illustrate the good WSR performance of the designs and the gains over naive constraint satisfaction approaches.