Full-stack Hybrid Beamforming in mmWave 5G Networks

This paper analyzes Hybrid Beamforming (HBF) and Multi-User Multiple-Input Multiple-Output (MU-MIMO) in millimeter wave (mmWave) 5th generation (5G) cellular networks considering the full protocol stack with TCP/IP traffic and MAC scheduling. Prior work on HBF and MU-MIMO has assumed full-buffer transmissions and studied link-level performance. We report non-trivial interactions between the HBF technique, the front-loaded channel estimation pilot scheme in NR, and the constraints of MU-MIMO scheduling. We also report that joint multi-user beamforming design is imperative, in the sense that the MU-MIMO system cannot be fully exploited when implemented as a mere collection of single-user analog beams working in parallel. By addressing these issues, throughput can be dramatically increased in mmWave 5G networks by means of Spatial Division Multiple Access (SDMA).

I. Introduction

The next generations of mobile networks will need to support a wide range of applications that demand significantly higher rates, such as video and content delivery; lower latency, such as eHealth and Connected Autonomous Vehicless (CAVs); and increased reliability, such as Internet of Things (IoT) in smart factories and smart cities [1]. The 3rd Generation Partnership Project (3GPP) specification for 5G cellular networks [2] is positioned to address these challenges, introducing a new Radio Access Network (RAN) design (i.e., 3GPP NR). It features a flexible Orthogonal Frequency Division Multiplexing (OFDM) frame structure with a flexible numerology, and, for the first time in the RAN, the support for mm Wave communications in the 24–53 GHz band, referred to as Frequency Range 2 (FR2).