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6G Takes Shape

Jeffrey G. Andrews, Todd E. Humphreys, Tingfang Ji

Abstract

The contours of 6G -- its key technical components and driving requirements -- are finally coming into focus. Through twenty questions and answers, this article defines the important aspects of 6G across four categories. First, we identify the key themes and forces driving the development of 6G, and what will make 6G unique. We argue that 6G requirements and system design will be driven by (i) the tenacious pursuit of spectral (bits/Hz/area), energy (bits/Joule), and cost (bits/dollar) efficiencies, and (ii) three new service enhancements: sensing/localization/awareness, compute, and global broadband/emergency connectivity. Second, we overview the important role of spectrum in 6G, what new spectrum to expect in 6G, and outline how the different bands will be used to provide 6G services. Third, we focus our attention on the 6G physical layer, including waveforms, MIMO advancements, and the potential use of deep learning. Finally, we explore how global connectivity will be achieved in 6G, through non-terrestrial networks as well as low-cost network expansion via disaggregation and O-RAN. Although 6G standardization activities will not begin until late 2025, meaning this article is by definition speculative, our predictions are informed by several years of intensive research and discussions. Our goal is to provide a grounded perspective that will be helpful to both researchers and engineers as we move into the 6G era.

6G Takes Shape

Abstract

The contours of 6G -- its key technical components and driving requirements -- are finally coming into focus. Through twenty questions and answers, this article defines the important aspects of 6G across four categories. First, we identify the key themes and forces driving the development of 6G, and what will make 6G unique. We argue that 6G requirements and system design will be driven by (i) the tenacious pursuit of spectral (bits/Hz/area), energy (bits/Joule), and cost (bits/dollar) efficiencies, and (ii) three new service enhancements: sensing/localization/awareness, compute, and global broadband/emergency connectivity. Second, we overview the important role of spectrum in 6G, what new spectrum to expect in 6G, and outline how the different bands will be used to provide 6G services. Third, we focus our attention on the 6G physical layer, including waveforms, MIMO advancements, and the potential use of deep learning. Finally, we explore how global connectivity will be achieved in 6G, through non-terrestrial networks as well as low-cost network expansion via disaggregation and O-RAN. Although 6G standardization activities will not begin until late 2025, meaning this article is by definition speculative, our predictions are informed by several years of intensive research and discussions. Our goal is to provide a grounded perspective that will be helpful to both researchers and engineers as we move into the 6G era.

Paper Structure

This paper contains 26 sections, 4 figures, 1 table.

Table of Contents

  1. Introduction: What this paper is about
  2. The case for 6G
  3. Question 1: There is a widespread sense that 5G has been a disappointment. Why is that? Is it true?
  4. Question 2: Based on lessons learned from 5G, what should 6G do differently?
  5. Question 3: Besides "fixing 5G," what new use cases, services, and applications will drive 6G?
  6. Question 4: What will be the new value proposition for 6G?
  7. Question 5: Will 6G be backward-compatible with 5G?
  8. Question 6: Will 6G be the last G?
  9. Spectrum for 6G
  10. Question 7: Which spectrum bands will have a major impact on 6G?
  11. Question 8: Will millimeter wave actually be used in 6G?
  12. Question 9: How will the different spectral bands in 6G be utilized?
  13. Question 10: You forgot to mention Terahertz (THz) spectrum and Reflective Intelligent Surfaces (RIS), which are often touted to be a big part of 6G. What’s their role?
  14. Question 11: How will spectrum be allocated in 6G? Will dynamic spectrum sharing across operators and systems become the norm?
  15. The 6G Physical Layer
  16. ...and 11 more sections

Figures (4)

  • Figure 1: 6G Efficiency Triangle. 6G system design will not focus so strongly on maximizing spectral efficiency and delivered data rate. Cost and energy efficiency will take on peer status, if not primacy, in communications system design.
  • Figure 2: 6G New Services Triangle. The 6G network will provide three key new types of value: pervasive sensing, compute resources, and true global connectivity including emergency access.
  • Figure 3: 6G Network Value Prism. The 6G network's newly created value versus 5G can be visualized as the volume of a prism. The top of the prism is the 6G new services triangle, while the bottom is the efficiency triangle. The extent of the 6G rollout is the height of the prism.
  • Figure 4: 6G Spectrum Pyramid.