A Wireless Backhaul using a Massive MIMO - 5G NR HetNet design; at Sub-6GHz and MillimetreWave Frequencies

Abstract

The three core means to increasing system capacity, considering the heterogeneity of the Next Generation Mobile Network (NGMN) are: - bandwidth, spectrum efficiency, and cell densification. For the latter one, small cells are envisioned to provide higher throughput by distributing vast numbers of them under macro cell coverage, creating a way to offload traffic and reduce transmitter-receiver distance. However, it immediately poses a problem of routing traffic from small cells to backbone network (backhauling). Here, advances in Massive Multiple Input Multiple Output (MIMO) antenna systems could bridge the gap in wireless backhaul, which is considered the most viable option for dense-urban small cell deployments. In this paper, we propose a 5GNR-compatible Heterogeneous Network (HetNet) architecture, where backhaul for millimeter wave small cells is provided by Massive MIMO enabled macro cell using FDD duplex in sub-6GHz band. Such an uncommon design would have the following advantages: (1) Non-mmWave backhaul links need not to be Line-Of-Sight, (2) Inter-cell interference between mmWave small cells is negligible, (3) The required Channel State Information(CSI) feedback rate for backhaul links is much smaller, if compared to the prospected 5G NR Base Station (gNB) to User Equipment (UE) fast fading links due to high level mobility; making MMIMO FDD deployment feasible in overcoming the issue of CSI feedback overhead, which is the major contribution of the proposed architecture.