ETSI ISG MAT: Bridging Multiple Access Techniques Research and 6G Standardisation

Bruno Clerckx; Carles Ant\'on-Haro; David Vargas; Dheeraj Raja Kumar; Fehmi Emre Kadan; H. M. Furqan; Kenza Abela; Malte Schellmann; Mert Ozates; Onur Dizdar

REVIEW 2 major objections 5 minor 12 references

ETSI ISG MAT: Bridging Multiple Access Techniques Research and 6G Standardisation

T0 review · 2 major / 5 minor · reviewed 2026-07-31 · grok-4.5

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Pith's one-line read Candidate 6G multiple-access methods beat today’s 3GPP baselines only under power imbalance or highly correlated user channels, and each gain has a clear cost in receivers, network help, and reference signals.

desk verdict Useful standards-bridging note on ETSI ISG MAT and GR MAT 001; gains are mostly vs TIN, and the paper already flags that the real 6G baseline is stronger. read the letter →

arxiv 2607.24226 v1 pith:6XWAUNU3 submitted 2026-07-27 eess.SP

Dheeraj Raja Kumar , Mert Ozates , Yong Jin Daniel Kim , David Vargas , Onur Dizdar , Fehmi Emre Kadan , Carles Antón-Haro , Sebastian Wagner

show 6 more authors

Bruno Clerckx Malte Schellmann Xavier Mestre H. M. Furqan Kenza Abela Shaima Abidrabbu

This is my paper · ORCID

classification eess.SP

keywords spectralefficiencymultipleaccesstechniquesinter-userinterferenceMU-MIMOpower-domainNOMARSMA6Gstandardisationnetwork-assistedcancellation

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

This paper reports what ETSI’s Industry Specification Group on Multiple Access Techniques found when it compared today’s 3GPP downlink schemes (orthogonal access, multi-user MIMO, and MUST) with candidate techniques (power-domain NOMA, rate-splitting multiple access, and cache-aided multi-user MIMO) under a common, standards-oriented yardstick. The central finding is that the candidates improve spectral efficiency only in identifiable operating regimes—chiefly power imbalance between users and/or highly correlated channels—and that those gains come with concrete requirements on successive-cancellation or reduced-complexity maximum-likelihood receivers, network assistance information, and (for rate-splitting) an extra demodulation reference signal. The group is now moving from capacity formulas to realistic 5G NR link-level simulations and to non-terrestrial networks so that 3GPP’s 6G study has timely, implementation-aware evidence rather than academic rankings alone. A sympathetic reader cares because spectral efficiency and inter-user interference mitigation are named IMT-2030 goals, and the paper maps which techniques actually help under which conditions and what the radio interface would have to carry to use them.

What carries the argument

The common standards-oriented comparison framework of GR MAT 001: it scores each technique on transmit architecture, receiver type, network assistance to the user equipment, demodulation-reference-signal count, and spectral-efficiency performance under a shared line-of-sight model with low-complexity precoders, so research candidates and already-specified 3GPP features can be judged on the same implementation-relevant axes.

What would settle it

Run the planned 5G NR PDSCH link-level simulations (finite block length, specified modulation and coding, realistic channels) for the same power-imbalance and high-correlation cases: if power-domain NOMA and RSMA no longer beat MU-MIMO with TIN or OMA on sum or weak-user throughput once real receivers and overhead are counted, the claimed operating-condition gains do not hold.

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Extended reading notes

Core claim

Under the standards-oriented comparison in ETSI GR MAT 001 V1.1.1, power-domain NOMA and rate-splitting multiple access can improve spectral efficiency relative to orthogonal multiple access or multi-user MIMO that treats interference as noise, but only when scheduled users show power imbalance and/or highly correlated channels; each candidate also imposes specific costs in transceiver processing, network assistance information, and reference-signal overhead that a 6G radio interface would have to support.

Load-bearing premise

The reported performance rankings rest on capacity formulas that assume Gaussian signaling, infinite block length, and a simple line-of-sight channel with low-complexity precoders, not full link- or system-level 5G simulations.

Editorial extensions

If this is right

6G study items on enhanced network-assisted interference cancellation can cite concrete regimes (power imbalance, high channel correlation) where NOMA or RSMA are worth the extra assistance signalling.
Rate-splitting multiple access would need standard support for an additional common-stream DM-RS and for message-splitting/combining at both ends.
MU-MIMO sum throughput only clearly beats OMA when advanced R-ML receivers with network assistance are used; TIN alone is not enough under the reported setups.
Cache-aided MU-MIMO remains a niche option limited to cacheable content until simplified performance metrics exist for the same comparison framework.
Ongoing NR link-level and NTN work items can supply the missing finite-block-length and non-terrestrial evidence before Release 21 normative text freezes.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

If the link-level campaign confirms the capacity rankings, 3GPP may prioritise common DCI that carries co-scheduled users’ modulation, coding, and DM-RS configuration as the practical enabler for both R-ML MU-MIMO and NOMA/RSMA.
The same condition map (power imbalance vs correlation) could be reused to decide when to fall back from RSMA to plain MU-MIMO, reducing always-on common-stream overhead.
NTN beams with strong path-loss disparity look like a natural fit for the power-imbalance regimes where the report already sees NOMA/RSMA gains, so the MAT-for-NTN study may become the first deployment driver.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

This is a clear status note on ETSI ISG MAT and GR MAT 001, not a new PHY result. What it does well is put OMA, MU-MIMO, MUST, power-domain NOMA, RSMA, and cache-aided MU-MIMO on one standards-facing ledger: who needs what network assistance, what DM-RS count, SIC vs R-ML vs TIN, and under which simple LoS conditions (power imbalance, high correlation) the capacity screen says candidates can beat OMA or MU-MIMO-TIN. The hedging is honest—Gaussian/infinite-blocklength, low-complexity precoders, CA MU-MIMO not scored, “not definitive LLS/SLS”—and the 3GPP timing and liaison trail is useful context for anyone tracking Rel-20/21.

The soft spot is real but disclosed, not hidden. The headline “can improve SE” comparisons are largely against MU-MIMO with TIN. 3GPP already has an R-ML advanced MU-MIMO receiver with network assistance (TS 38.101-4 lineage). Their own Fig. 1 shows R-ML taking a large bite out of the TIN gap under None/MRT. So the incremental win of NOMA/RSMA over the strongest specified baseline may shrink exactly where the capacity story looked best, and the extra SIC/common-stream/DM-RS costs then matter more. That is a scope gap the paper owns and is trying to close with NR PDSCH LLS; it is not a contradiction inside the manuscript.

Math and citations look fine for this genre: standard capacity comparisons, known RSMA/NOMA/MUST/NAIC references, no invented entities, no circular fitting. Novelty is modest by design—exposition of an already-published GR plus one illustrative LLS figure and NTN work items.

Who it is for: people who need a compact, fair map of MAT options and implementation costs before 3GPP 6G feature fights, not people hunting a new algorithm. I would send it to peer review as a short standards/position piece; it is competent and timely enough to deserve referee time, with the baseline-comparison caveat kept visible. Engage if you care about 6G multi-user PHY process; skip if you only want primary methods.

Referee Report

2 major / 5 minor

Summary. This short paper describes the scope and first output of ETSI ISG MAT, a pre-standardisation group for downlink multiple access techniques in 3GPP-based 6G. It summarises ETSI GR MAT 001 V1.1.1, which compares specified baselines (OMA, MU-MIMO with TIN and R-ML receivers, MUST Case 1) against candidate techniques (power-domain NOMA, RSMA, cache-aided MU-MIMO) under a simplified line-of-sight capacity model with varying power imbalance and user-channel correlation. The reported findings are that NOMA and RSMA can improve spectral efficiency over OMA and MU-MIMO-with-TIN in identifiable regimes (power imbalance, high channel correlation), with explicit accounting of receiver complexity, network assistance information, and DM-RS overheads. The paper also previews one 5G NR PDSCH link-level simulation comparing TIN and R-ML receivers across precoders, and lists ongoing work items on high-order SU-MIMO and NTN. The tone is appropriately hedged for a position/survey piece.

Significance. If taken at face value, the paper's contribution is modest in new technical results but useful in function: it documents an open pre-standardisation venue whose outputs (common terminology, comparison against specified 3GPP features, DM-RS and assistance-information cost accounting) are genuinely relevant to the 3PP Release 20/21 timeline it cites. The manuscript deserves credit for unusual candour in a standards-adjacent piece: it states plainly that the capacity expressions assume Gaussian signalling and infinite block length, that R-ML receivers were therefore not scored, that CA MU-MIMO was not evaluated, and that the results 'do not constitute definitive link-level or system-level comparisons.' It also provides verifiable, falsifiable anchors — the named liaison statements, the GR number, and a fully specified LLS configuration in Fig. 1 — that allow the community to check and extend the work. The main risk to its significance is the baseline issue in Major Comment 1: the case for candidate MAT is made against TIN, while the standardisation-relevant comparator is the already-specified R-ML advanced receiver.

major comments (2)

[Section II (evaluation paragraphs) and Section III (LLS plans)] The central relevance claim — that GR MAT 001 provides 'timely technical evidence' for 6G standardisation decisions on candidate MAT — rests on comparisons against MU-MIMO with TIN receivers only. Yet Section III itself notes that 3GPP has already specified an R-ML advanced MU-MIMO receiver with network assistance information (performance requirements in TS 38.101-4), and Fig. 1 shows R-ML delivering large gains over TIN for the None and MRT precoders. It is therefore plausible that the regimes where NOMA/RSMA beat TIN (power imbalance plus high channel correlation) substantially overlap with regimes where specified MU-MIMO with R-ML already captures most of the available gain, in which case the incremental benefit of the candidate techniques against the decision-relevant baseline could be much smaller, while their overheads (SIC processing, extra DM-RS for the RSMA common stream, additi
[Section III, Fig. 1 discussion] The interpretation of Fig. 1 is under-supported and partly confusing as written. (i) The statement that 'MU-MIMO with MRT outperforms ZF because it does not affect the power of the precoded transmit symbols' is not a standard explanation: with per-RE precoding and perfect CSI, ZF performance is normally limited by normalisation-induced power loss when user channels are correlated, and MRT is limited by residual inter-user interference that TIN cannot handle; the observed ordering likely depends on the R-ML receiver cleaning up MRT's residual interference. (ii) The claim that R-ML provides no gain 'for ZF where all interference is suppressed at the transmitter' should be quantified — the ZF/TIN and ZF/R-ML curves in Fig. 1 appear close but the figure alone does not establish exact interference suppression. Since Fig. 1 is the only original quantitative evidence in the paper and is used to

minor comments (5)

[Section III, Fig. 1] Fig. 1 and caption: 'Zero Forzing' should be 'Zero Forcing'. The caption is very dense; consider splitting the simulation assumptions (4Tx2Ue2Rx, TDL-C300, 52 RBs, MCS 9/15, etc.) into a short itemised list in the text for readability.
[Section III] 'To achieve a similar sum throughput than MU-MIMO' should read 'as MU-MIMO'.
[Section headings I-III] Headings render with missing spaces in the provided text ('INTRODUCTION AND6G STANDARDISATIONCONTEXT', 'ETSI ISG MATANDGR MAT 001', 'ONGOINGWORK ANDRELEVANCE TO3GPP 6G'); presumably a LaTeX spacing artifact, but worth checking in the final version.
[References and affiliations] Reference [7] (Jorswieck) is cited for power-domain NOMA generally; a more specific NOMA survey or the original MUST/NOMA comparison literature might serve readers better. Also, author-name spellings with diacritics (Antón-Haro, Vodafone capitalisation 'V odafone') show OCR/encoding artifacts in several places.
[Section II] Section II states CA MU-MIMO 'was not evaluated because suitable simplified performance metrics were unavailable' — one sentence on what metric gap prevented the evaluation (e.g., cache-content modeling within the LoS capacity framework) would help readers judge whether this is a temporary or structural exclusion.

Circularity Check

0 steps flagged · score 0.0 of 10

No circular derivation: standards overview summarizing GR MAT 001 comparisons, not a first-principles prediction chain.

full rationale

This paper is a pre-standardisation overview of ETSI ISG MAT and GR MAT 001. It does not claim to derive spectral-efficiency rankings from first principles, fit parameters then re-predict them, or import a uniqueness theorem that forces its conclusions. Reported gains for power-domain NOMA and RSMA are framed as capacity-expression comparisons under a stated simplified LoS model with Gaussian signaling and infinite block length, with explicit caveats that they are not definitive link- or system-level results and that R-ML receivers were excluded. Figure 1 is an illustrative 5G NR LLS example, not a fitted-then-predicted quantity. Citations to the group’s own GR and to prior RSMA/NOMA/caching literature are ordinary prior-art and deliverable references for this genre; none reduce a central claim to an input by construction. No circular steps identified.

Assumptions & free parameters 3 free parameters · 5 assumptions · 0 invented entities

The paper’s load-bearing content is comparative and procedural, not a closed-form discovery. It inherits standard wireless multi-user models (TIN, SIC, R-ML, linear precoding), 3GPP feature definitions, and a simplified LoS capacity evaluation regime from the GR. No new physical entities are postulated. Free choices are simulation/evaluation settings that affect quantitative curves but not the qualitative taxonomy.

free parameters (3)

LoS power-imbalance and channel-correlation operating points
Capacity rankings for NOMA/RSMA vs OMA/MU-MIMO are reported as depending on chosen imbalance/correlation regimes in the simplified model; specific sweep values are not fully tabulated in this manuscript.
LLS MCS and resource allocation (MCS 9 MU-MIMO vs MCS 15 OMA; 52 RBs total, 26 RBs/UE for OMA) = MCS 9 (MU-MIMO), MCS 15 (OMA); 52 RBs / 26 RBs per UE OMA
Fig. 1 sum-throughput comparison depends on these hand-chosen MCS/RB settings to place OMA and MU-MIMO on the same plot.
Precoder choice set (None, MRT, ZF) and perfect-CSI assumption = perfect CSI; no Doppler; no HARQ
LLS conclusions about R-ML gains and MRT vs ZF are conditioned on this discrete precoder set and ideal CSI/no Doppler/no HARQ.

assumptions (5)

domain assumption Inter-user interference under MU-MIMO can be modeled as noise (TIN) or jointly demodulated via R-ML with network assistance on co-scheduled modulation orders, without full decode-and-cancel of interferers.
Used throughout Section II when defining specified MU-MIMO advanced receivers and contrasting them with SIC-based NOMA.
domain assumption Gaussian signaling and infinite block-length capacity expressions are informative enough to identify promising operating conditions for candidate MAT versus OMA/MU-MIMO.
Explicit evaluation basis in GR MAT 001 as summarized in Section II; paper notes this excludes R-ML techniques from that comparison.
ad hoc to paper A simple line-of-sight channel with varying power imbalance and user correlation, plus low-complexity precoders, is an acceptable standards-oriented first screen.
Stated evaluation setup for GR MAT 001 comparisons; drives the reported NOMA/RSMA gain regions.
domain assumption 3GPP-specified OMA, MU-MIMO (TIN and R-ML), and MUST Case 1 definitions are the correct baselines for 6G downlink MAT discussion.
Section II baseline list; comparison framework depends on these feature definitions.
domain assumption Cache-aided MU-MIMO applicability is restricted to cacheable content and can cancel inter-group interference using cached side information.
Candidate definition in Section II citing prior caching literature; explains why it was not capacity-evaluated here.

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Pith. "Pith review of ETSI ISG MAT: Bridging Multiple Access Techniques Research and 6G Standardisation." pith.science (2026). https://pith.science/paper/6XWAUNU3

@misc{pith2026260724226,
  author       = {Pith},
  title        = {Pith review of: ETSI ISG MAT: Bridging Multiple Access Techniques Research and 6G Standardisation},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/6XWAUNU3}},
  note         = {Machine review of arXiv:2607.24226}
}

read the original abstract

Improved spectral efficiency and inter-user interference mitigation are important aspects of IMT-2030 and the ongoing 3GPP 6G study. ETSI established the Industry Specification Group on Multiple Access Techniques (ISG MAT) as a research and pre-standardisation activity to build wider consensus on downlink MAT for 3GPP-based 6G systems. Its first report, ETSI GR MAT 001 V1.1.1, provides a standards-oriented comparison of 3GPP-specified techniques, including OMA, MU-MIMO, and MUST, with candidate techniques comprising power-domain NOMA, RSMA, and cache-aided MU-MIMO. The report identifies operating conditions in which candidate MAT can improve spectral efficiency and assesses implications for transceiver processing, network assistance information, and reference-signal requirements. Ongoing work includes realistic 5G NR link-level evaluations and the study of MAT for non-terrestrial networks, providing timely technical evidence for 3GPP 6G standardisation discussions.

Figures

Figures reproduced from arXiv: 2607.24226 by the authors.

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

12 extracted references

[1]

Framework and overall objectives of the future development of IMT for 2030 and beyond,

ITU-R, “Framework and overall objectives of the future development of IMT for 2030 and beyond,” Recommendation ITU-R M.2160-0, November 2023
[2]

Future technology trends of terrestrial International Mobile Telecommunications systems towards 2030 and beyond,

ITU-R, “Future technology trends of terrestrial International Mobile Telecommunications systems towards 2030 and beyond,” Report ITU-R M.2516-0, November 2022
[3]

Addressing CAPEX/OPEX requirement in RAN1,

V odafone, AT&T, BT, Bouygues Telecom, Deutsche Telekom, Orange, Telecom Italia, Nokia, and China Unicom, “Addressing CAPEX/OPEX requirement in RAN1,” in3GPP TSG RAN WG1 #123, 2025. R1- 2509397, 2025

2025
[4]

Revised SID: Study on 6G Radio,

3GPP, “Revised SID: Study on 6G Radio,” in3GPP TSG RAN #110,
[5]

Release 21 Timeline,

3GPP, “Release 21 Timeline,” in3GPP TSG RAN #112, 2026. RP- 260868, June 2026

2026
[6]

Multiple Access Techniques (MAT); Classification of Candidate Multiple Access Techniques for 6G and their comparison with specified 3GPP features,

ETSI, “Multiple Access Techniques (MAT); Classification of Candidate Multiple Access Techniques for 6G and their comparison with specified 3GPP features,” ETSI GR MAT 001 V1.1.1, January 2026

2026
[7]

Next-generation multiple access: From basic principles to modern architectures,

E. A. Jorswieck, “Next-generation multiple access: From basic principles to modern architectures,”Proceedings of the IEEE, 2024

2024
[8]

Rate-splitting multiple access for downlink communication systems: bridging, generalizing, and outper- forming SDMA and NOMA,

Y . Mao, B. Clerckx, and V . O. Li, “Rate-splitting multiple access for downlink communication systems: bridging, generalizing, and outper- forming SDMA and NOMA,”J Wireless Com Network, 2018

2018

Show all 12 references

[9]

Adding transmitters dramatically boosts coded- caching gains for finite file sizes,

E. Lampiris and P. Elia, “Adding transmitters dramatically boosts coded- caching gains for finite file sizes,”IEEE J. Sel. Areas Commun., 2018

2018
[10]

Views on 6G PHY choices,

BT, Orange, V odafone, Deutsche Telekom, Turkcell, and KPN, “Views on 6G PHY choices,” in3GPP TSG RAN WG1 #122, 2025. R1-2506394, 2025

2025
[11]

Common DCI scheduling MU- MIMO UEs,

Orange, Deutsche Telekom, AccelerComm, BBC, BT, V odafone, CMCC, China Telecom, China Unicom, T-Mobile USA, Verizon, Sam- sung, VIA VI Solutions Inc., and ZTE, “Common DCI scheduling MU- MIMO UEs,” in3GPP TSG RAN WG1 #125, 2026. R1-2604454, 2026

2026
[2025]

RP-253876, December 2025

2025

Pith tools

Reviewed July 31, 2026 · model on record in the stance chip above.

[1] [1]

Framework and overall objectives of the future development of IMT for 2030 and beyond,

ITU-R, “Framework and overall objectives of the future development of IMT for 2030 and beyond,” Recommendation ITU-R M.2160-0, November 2023

[2] [2]

Future technology trends of terrestrial International Mobile Telecommunications systems towards 2030 and beyond,

ITU-R, “Future technology trends of terrestrial International Mobile Telecommunications systems towards 2030 and beyond,” Report ITU-R M.2516-0, November 2022

[3] [3]

Addressing CAPEX/OPEX requirement in RAN1,

V odafone, AT&T, BT, Bouygues Telecom, Deutsche Telekom, Orange, Telecom Italia, Nokia, and China Unicom, “Addressing CAPEX/OPEX requirement in RAN1,” in3GPP TSG RAN WG1 #123, 2025. R1- 2509397, 2025

2025

[4] [4]

Revised SID: Study on 6G Radio,

3GPP, “Revised SID: Study on 6G Radio,” in3GPP TSG RAN #110,

[5] [5]

Release 21 Timeline,

3GPP, “Release 21 Timeline,” in3GPP TSG RAN #112, 2026. RP- 260868, June 2026

2026

[6] [6]

Multiple Access Techniques (MAT); Classification of Candidate Multiple Access Techniques for 6G and their comparison with specified 3GPP features,

ETSI, “Multiple Access Techniques (MAT); Classification of Candidate Multiple Access Techniques for 6G and their comparison with specified 3GPP features,” ETSI GR MAT 001 V1.1.1, January 2026

2026

[7] [7]

Next-generation multiple access: From basic principles to modern architectures,

E. A. Jorswieck, “Next-generation multiple access: From basic principles to modern architectures,”Proceedings of the IEEE, 2024

2024

[8] [8]

Rate-splitting multiple access for downlink communication systems: bridging, generalizing, and outper- forming SDMA and NOMA,

Y . Mao, B. Clerckx, and V . O. Li, “Rate-splitting multiple access for downlink communication systems: bridging, generalizing, and outper- forming SDMA and NOMA,”J Wireless Com Network, 2018

2018