Technology Roadmap Working Group Hosts Extreme MIMO Panel
ATIS’ Next G Alliance Technology Roadmap Working Group (TRWG) hosted a panel on January 7, 2026 to shape a realistic, forward-looking vision for extreme/massive MIMO in 6G, emphasizing that 6G extreme MIMO should represent a fundamental architectural evolution rather than a simple extension of 5G. Participants highlighted the need to balance ambition with deployability, grounding both research and standardization efforts in technical feasibility, spectrum realities, and economic constraints.
The evolution of massive and extreme MIMO was identified as a major enabler for 6G capacity and coverage, particularly in mid-band and upper-mid-band spectrum. While very large antenna arrays promise significant gains, participants raised concerns around channel modeling accuracy, calibration complexity, power consumption, cost, and site-level deployment constraints. The group emphasized the need for realistic assumptions when extrapolating performance gains, especially when reusing existing infrastructure.
Extreme MIMO and Propagation
Robert Heath provided an academic, theory-driven perspective on extreme MIMO and propagation, highlighting the limitations of existing channel models when extrapolated to very large arrays and emphasizing the need for measurement-based validation. He also described a new framework for MIMO communication that embraces reconfigurable antennas, which he calls the tri-hybrid MIMO architecture. Heath explained how this architecture may contribute towards low-power extreme MIMO in 6G, if ongoing research at the intersection of communication theory, electromagnetics and AI is successful.
Spectrum Strategy
Fred Vook focused on 6G spectrum strategy, emphasizing mid-band and upper-mid-band tradeoffs, coexistence and regulatory realism, and noting that spectrum availability, rather than theory, will ultimately constrain 6G performance. Spectrum strategy emerged as a critical and potentially limiting factor for 6G. Discussions covered mid-band, upper-mid-band, and sub-THz frequencies, with broad agreement that no single band will suffice. Higher frequencies offer bandwidth, but face challenges related to propagation, coverage, energy efficiency, densification issues and coexistence with incumbents. Regulatory alignment, global harmonization, and credible coexistence studies were viewed as essential prerequisites for successful 6G deployment. Additional discussions focused on the numerous features and options supported by 5G and how those features can be streamlined and improved as we move into 6G. Also discussed was how AI/ML techniques are expected to be incorporated into 6G MIMO standardization, along with the associated challenges; the current standards status; and how such techniques are expected to compare against existing classical methodologies.
Yeliz Tokgoz noted that while higher frequencies introduce certain challenges, advances in device and infrastructure capabilities enable upper‑mid‑band deployments to be co‑sited with existing mid‑band sites, paving the way for fast and cost‑effective 6G extreme‑MIMO rollouts. She emphasized that transmit‑power enhancements and beamforming gains are critical to improving both downlink and Uplink (UL) coverage and capacity.
Lessons Learned from 5G Massive MIMO
Mark Harrison spoke of some lessons learned from 5G massive MIMO and a few opportunities for 6G MIMO enhancements. We’ve learned how to make MIMO work better in practice by understanding implementation limitations in both User Equipment (UE) and base stations, e.g., in terms of Radio Frequency (RF) hardware and channel state information that degrade MIMO performance. Opportunities for 6G include MIMO techniques that better match the bursty traffic that is observed in networks, Channel State Information (CSI) enhancements, and uplink MIMO schemes taking into account UE Power Amplifier (PA) limitations like multi-layer Discrete Fourier Transform-spread-Orthogonal Frequency Division Multiplexing (DFT-s-OFDM).
ATIS’ Next G Alliance: The Role of Standardization
From a standardization perspective, Next G Alliance was seen as a valuable forum to align industry, academia, and regulatory stakeholders early in the 6G lifecycle. Participants cautioned against premature over-standardization that could stifle innovation, while recognizing the need for early guidance on architectures, spectrum assumptions, and AI enablers. Cross-industry collaboration, including vertical sectors, was viewed as increasingly important.
Near-Field MIMO
Finally, Jyotish Robin discussed the potential of near-field MIMO, which introduces distance domain as an additional dimension for radio resource management (alongside traditional dimensions such as time, frequency, spatial domain, polarization, etc.) in mid-band and upper mid-band spectrum. He highlighted key operational aspects required to support the simultaneous coexistence of near field and far field users within the same cell. Some panelists indicated that this area needs to be further researched. The panelists were asked what kind of spectrum efficiency gain 6G Extreme MIMO will offer over 5G Massive MIMO. The consensus was 2-3x improvement in spectrum efficiency.
Overall, the discussion was pragmatic and evidence-driven, focusing on credible paths from research to deployment. The panel did not aim to make decisions, but rather to frame key challenges, identify research gaps, and guide future NGA contributions to the global 6G Extreme MIMO dialogue.
Key Takeaways from the Extreme MIMO Panel Discussion
- The evolution of massive and extreme MIMO was identified as a major enabler for 6G capacity and coverage, particularly in mid-band and upper-mid-band spectrum.
- Advances in device and infrastructure capabilities enable upper‑mid‑band deployments to be co‑sited with existing mid‑band sites.
- Higher frequencies offer bandwidth, but face challenges related to propagation, coverage, energy efficiency, densification issues and coexistence with incumbents.
- AI/ML techniques for extreme MIMO should be compared against existing classical methodologies (suitably optimized) and should provide reasonable improvements in terms of various Key Performance Indicators (KPIs).
- UL coverage and capacity enhancements should be one of the key 6G Day 1 features.
- 6G should include MIMO techniques that better match the bursty traffic that is observed in networks and better reflect implementation limits of UEs and base stations.
- Advanced techniques like reconfigurable antenna architectures, tri-hybrid MIMO, and near field MIMO should be investigated further.
Learn more about the work of the NGA Technology Roadmap Working Group, which is developing and maintaining a lifecycle roadmap for 6G that extends from research to market readiness.
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