Massive MIMO

Massive Multiple Input Multiple Output

Physical Layer

Introduced in Rel-15

Antenna technology using large antenna arrays (64+) for high capacity and beamforming.

Description

Massive MIMO uses a large number of antenna elements (typically 64-256) at the base station to serve multiple users simultaneously through spatial multiplexing and beamforming.

In 5G NR, Massive MIMO is essential for both sub-6 GHz (capacity improvement) and mmWave (compensating path loss). It enables advanced beamforming with beam management procedures for initial access and mobility.

Purpose & Motivation

Massive MIMO was enhanced for 5G to:

- Dramatically increase spectral efficiency - Enable mmWave operation through beamforming gain - Support many users simultaneously (MU-MIMO) - Improve coverage and cell-edge performance

Key Features

  • 64-256 antenna elements
  • 3D beamforming
  • Beam management (P1/P2/P3)
  • CSI-RS based measurements
  • Type I and Type II codebooks
  • Multi-user MIMO (MU-MIMO)

Evolution Across Releases

Rel-13Initial

FD-MIMO in LTE with 2D antenna arrays (precursor)

NR Massive MIMO with beam management, Type I/II codebooks

Enhanced Type II codebook, multi-TRP operation

AI/ML for beam management, further codebook enhancements

Defining Specifications

SpecificationTitle
NR Physical Channels and Modulation
NR Physical Layer Procedures for Data
Physical Layer Measurements