Massive Near-Field Spatial Multiplexing: Higher Capacity Without More Bandwidth

Abstract
The demand for wireless data traffic is steadily growing, thus, increasing the network capacity must remain the center point of the 6G network development. In the 5G era, we have witnessed how the attempts to build high-capacity cellular networks in the mmWave bands have largely failed. The key example is South Korea, which discontinued these networks in 2023. As we are running out of spectrum suitable for wide-area connectivity, we must search for alternative ways to cater to the exponential traffic growth. In this talk, we will examine whether enhancement in the multiple-input multiple-output (MIMO) technology can lead the way. The concepts of radiative near-field propagation with spherical wavefronts, finite-depth beamforming, and spatial degrees of freedom will be explained and connected to the physical antenna array dimensions. We will conclude on whether massive spatial multiplexing is an untapped resource that can boost the capacity of 6G networks, and what MIMO functionality we can expect in the first 6G deployments.

This is a recording of a talk that was previously given as a keynote at ELLIIT "6G – forming a better future", BalkanCom 2024, International Conference on Applied Research in Electrical Engineering (AREE) 2025, IEEE AP-MTTS SBC IITKGP Online Invited Talk 2025, IEEE Young Professionals Singapore "Technical Talk Series on Emerging Technologies" 2025.

Presenter: Emil Björnson, Professor of Wireless Communication, KTH Royal Institute of Technology, Stockholm, Sweden.

The slides are available here: https://github.com/emilbjornson/prese...