Is OFDMA Still the Best Multiple Access for 6G?

Every new generation of mobile technology raises the question of whether the next step should be an evolution or a revolution. The prevailing industry view is that 6G will be an evolution rather than a radical departure. For decades, the telecom sector has relied on Orthogonal Frequency Division Multiple Access (OFDMA) as the backbone of wireless communication, and with 6G development progressing, it appears increasingly certain that OFDMA will continue to be the cornerstone of future networks.

The recent formation of ETSI’s new Industry Specification Group (ISG) on Multiple Access Techniques (MAT) highlights the industry’s continued exploration of various multiple access methods. The press release emphasizes that the group aims to build industry consensus on innovative multiple access techniques, based on 3GPP specifications.

Scope of ISG MAT

The ISG focuses on downlink Multi-User (MU) multiple access techniques for the physical layer of the 3GPP radio interface, aiming to enhance transmission efficiency in key areas such as spectrum efficiency, power consumption, latency, and user fairness.

Two delivery modes for downlink are considered:

  • Unicast-only delivery
  • Joint broadcast/multicast and unicast delivery

Candidate downlink multiple access techniques under consideration include:

  • OMA (Orthogonal Multiple Access)
  • SDMA (Spatial Division Multiple Access)
  • NOMA (Non-Orthogonal Multiple Access)
  • RSMA (Rate-Splitting Multiple Access)

Relevant deployment environments include indoor hotspots, urban macro (e.g., high-density areas), and rural settings.

Areas of Activity

The ISG will focus on the following areas of research and evaluation:

  • Use cases, deployment scenarios, key performance indicators, and evaluation methodology
  • Study of transmitter and receiver processing structures, including complexity aspects
  • Study of physical layer procedures
  • Study of link-level and system-level performance
  • Study of potential specification impact and gaps in new multiple access techniques
  • Proof-of-concepts, prototypes, and field trials

The new ETSI Group will produce Group Reports for consideration by 3GPP and other relevant industry bodies in their 6G standardization efforts. The initiative aligns with evolving network needs, supporting new interactive immersive experiences and enhancing connectivity in high-demand density areas. It also aims to improve media delivery over mobile networks at scale.

OFDMA’s Continued Dominance

While ETSI’s announcement confirms that alternative multiple access techniques are being studied, the industry remains aligned with OFDMA as the gold standard. A thorough examination of alternatives does not necessarily indicate a shift away from OFDMA unless significant, demonstrable improvements emerge.

Both 4G LTE and 5G have successfully employed OFDMA, with 5G refining it further for enhanced flexibility and efficiency. Real-world deployments consistently show that while alternative multiple access techniques may offer theoretical advantages, their practical implementation introduces complexities that outweigh their benefits. For example, despite years of academic research on NOMA, its adoption in real-world 5G deployments has been minimal. The same trend is likely for 6G.

Optimizing OFDMA for 6G

Instead of pursuing disruptive changes in multiple access technology, the more practical path for 6G lies in optimizing OFDMA. Enhancements could include:

  • Improved spectral efficiency
  • Reduced overhead
  • Greater adaptability for emerging 6G use cases such as immersive interactive experiences and ultra-reliable low-latency communication

While ETSI’s ISG MAT initiative is an important step in reaffirming industry consensus on multiple access techniques, its formation should not be mistaken as a threat to OFDMA’s dominance. If anything, this effort is likely to reinforce the conclusion that OFDMA remains the most effective and scalable approach for the future of wireless networks.

As 6G development continues, the industry will undoubtedly explore refinements and optimizations, but the fundamental multiple access technology is unlikely to change. OFDMA is not just good enough—it remains the best way forward.

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