Massive MIMO in Sub-6 GHz and mmWave: Physical, Practical, and Use-Case Differences

TL;DR

This paper compares Massive MIMO technology in sub-6 GHz and mmWave bands, highlighting their physical and practical differences, and proposes tailored signal processing schemes and use cases for each frequency range.

Contribution

It provides a comprehensive analysis of the differences between sub-6 GHz and mmWave Massive MIMO, and suggests optimized schemes and applications for each band.

Findings

Distinct propagation behaviors affect MIMO deployment

Hardware characteristics influence signal processing approaches

Use-case recommendations vary between frequency bands

Abstract

The use of base stations (BSs) and access points (APs) with a large number of antennas, called Massive MIMO (multiple-input multiple-output), is a key technology for increasing the capacity of 5G networks and beyond. While originally conceived for conventional sub-6GHz frequencies, Massive MIMO (mMIMO) is ideal also for frequency bands in the range 30-300 GHz, known as millimeter wave (mmWave). Despite conceptual similarities, the way in which mMIMO can be exploited in these bands is radically different, due to their specific propagation behaviors and hardware characteristics. This paper reviews these differences and their implications, while dispelling common misunderstandings. Building on this foundation, we suggest appropriate signal processing schemes and use cases to efficiently exploit mMIMO in both frequency bands.