5G massive MIMO with digital beamforming and two-stage channel estimation for low SHF band

Abstract

The fifth-generation (5G) mobile communication system will utilize higher frequency bands with wider bandwidth for super high bit rate and large system capacity. Massive multiple-input multiple-output (Massive MIMO) beamforming (BF) technology has attracted much attention to compensate larger path-loss of a disadvantage at higher frequency bands. In low-SHF bands, approximately 100 MHz bandwidth is assumed, thus fully-digital Massive MIMO having flexibility of BF can be applied. In this paper, we modify joint processing of analog fixed BF and channel state information (CSI)-based precoding (called FBCP), which is a hybrid BF technology, to fully-digital method (called Digital-FBCP). Although conventional studies about Massive MIMO with BF do not take account of channel estimation (CE) in detail, this paper describes two-stage CE required for multi-user (MU) Massive MIMO with BF. Throughput performance is evaluated by link level computer simulation in consideration of the reference design and pilot insertion loss. This paper shows that Digital-FBCP achieves almost equal or better throughput performance than conventional precoding (PR) without fixed BF.