MIMO

Multiple Input Multiple Output

Physical Layer

Introduced in Rel-8

Antenna technology using multiple transmit and receive antennas to increase throughput.

Description

Multiple Input Multiple Output (MIMO) is an antenna technology that uses multiple antennas at both transmitter and receiver to improve communication performance. LTE supports various MIMO configurations (2x2, 4x4, 8x8).

MIMO can be used for spatial multiplexing (increased data rate), transmit diversity (improved reliability), or beamforming (increased coverage).

Purpose & Motivation

MIMO was essential for LTE to achieve its target throughput:

- Double/quadruple peak rates with spatial multiplexing - Improve cell-edge performance with diversity - Increase capacity without additional spectrum - Enable advanced features like CoMP

Key Features

  • Spatial multiplexing
  • Transmit diversity
  • Beamforming
  • Precoding matrices
  • Codebook-based feedback

Evolution Across Releases

Rel-8Initial

Initial MIMO with 2x2 and 4x4 configurations

Enhanced MIMO up to 8x8 DL, improved feedback (eMIMO)

Full Dimension MIMO (FD-MIMO) with 2D antenna arrays

Defining Specifications

SpecificationTitle
Physical Channels and Modulation
Physical Layer Procedures
Physical Layer Measurements