A Multi-User-Hybrid Beamforming Scheme for Dual-Band Wireless Networks

Abstract

To highly increase the system capacity to cater to the ever-increasing mobile service requirements, millimeter wave (mmWave) bands with massive available bandwidth have been envisioned as promising candidates in spectrum extension by the fifth generation (5G) wireless communication networks. Nevertheless, compared with conventional microwave cellular bands, mmWave bands suffer from severer propagation loss and are hard to be directly applied into practical wireless communication systems. With an ability not only to overcome the unfavorable path loss of millimeter wave (mmWave) bands but also to provide spatial multiplexing at economical hardware costs, the hybrid analog and digital beamforming (HBF) technology attracts growing attention recently. Based on the feature of HBF, we propose a multi-user HBF (MU-HBF) precoding scheme for user closely co-located scenarios where users are too close to each other that they cannot be distinguished only by physically-separated directional beams. Considering that the limited coverage scope of mmWave directional beams cannot guarantee the network robustness, the control/user (C/U) plane decoupled network architecture is applied to integrate microwave bands with mmWave bands and form a dual-band wireless network, in which microwave bands provide omnidirectional coverage for mobility-related control plane signaling and mmWave bands provide high-speed transmission rate for user plane data. Analysis and simulations are provided to demonstrate the superior performance of the proposed MU-HBF precoding scheme under user closely co-located scenarios.