5G Research

MIMO

Practical Massive MIMO (multiple input, multiple output). MIMO is an antenna technology for wireless communications in which multiple antennas are used at both the transmitter and receiver.
Stairs landing in Dipoli with people sitting in two armchairs and looking at a painting / photo by Aalto University, Tuomas Uusheimo

Practical Massive MIMO

  • Remove the pilot contamination problem
    • Channel estimation based on subspace approach, random matrix theory

  • Codebooks for massive MIMO

    • Closed form low coherence frames / Grassmannian codebooks for k-dimensional subspaces in 2m–dimensional spaces, some optimal
    • Stiefel & Grassmannian codebooks
    • Convergence of gradient search for low-dimensional matrix completion in high-dimensional spaces
    • Minimum distance bounds on Stiefel and Grassmannian manifolds

  • Distributed Antenna Systems (DAS)

    • Over the air synchronization of remote radio units
    • Centralized base band processing
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