This page is the detailed, release-by-release companion to Standards: 5G Multicast Broadcast Services (MBS): the work items behind each release, and what each one added. See that page for the full specification list and current scope. For acronyms used here, see the Glossary.
Technology & Analysis
The implementer-facing analysis of the MBS architecture, including the Release 18 RAN procedures this page covers below.
Software Tools
The reference implementation for 5G-native multicast and broadcast delivery.
5G MBS is not one 3GPP work item but a family, run in parallel across SA2 (core architecture), SA4 (user-service layer), CT1/CT3/CT4/CT6 (stage-3 protocols), RAN2/RAN3 (radio and RAN interfaces) and SA3 (security), each with its own work item under a shared umbrella. The table below lists every work item confirmed directly against the 3GPP work item portal for this page; see "References to verify" at the end for exactly what that does and does not establish.
Release-by-release summary
| 3GPP Release | Key additions |
|---|---|
| Rel-17 | The foundational feature: Stage 2 architecture (TS 23.247), user-service layer protocols (TS 26.502, TS 26.517), Stage 3 core network services (TS 29.532, TS 29.580, TS 29.581, TS 29.537), NR/NG-RAN broadcast support. Security study TR 33.850. |
| Rel-18 | RAN: MBS multicast reception in RRC_INACTIVE (new TS 38.331 clause 5.10, a new DCI format split at the physical layer — see below). Core: charging for SMF/MB-SMF (TS 32.279). UE: pre-configuration Management Object (TS 24.575). Architecture study TR 23.700-47 and security study TR 33.883 precede/accompany this phase. |
| Rel-19 | Non-terrestrial network (NTN) extensions to MBS broadcast, tracked as part of the general NTN Phase 3 feature rather than a dedicated MBS work item; see MBS Broadcast over NTN for the technical detail. No Rel-19 MBS work item beyond this has been found. |
Check the version of each specification you are targeting for the exact release content; see Standards: 5G MBS for the full list.
Work items behind each release
| 3GPP Release | Work item (parent, then children) |
|---|---|
| Rel-17 (SA2, core architecture) | Parent: 900038 Multicast-broadcast services in 5G (acronym 5MBS; TSG SA#90 approval) Children: 830030 Study on Architectural enhancements for 5MBS (the TR 23.757 study phase), 900009 Stage 2 for 5MBS (TS 23.247), 910002 CT4 aspect of 5MBS, 920023 Security Aspects of Enhancements for 5G Multicast-Broadcast Services (TR 33.850), 920043 CT1 aspects of 5MBS, 920044 CT3 aspects of 5MBS, 960067 CT6 aspects of 5MBS. TS 29.532 and TS 29.581 are CT4's; TS 29.580 and TS 29.537 are CT3's — confirmed by checking which TSG sub-group meeting ( 3GPPCT3#.../3GPPCT4#...) actually handled each spec's Change Requests: every one of TS 29.532's 154 and TS 29.581's 102 tracked CRs went through CT4; every one of TS 29.580's 128 and TS 29.537's 73 went through CT3, with no exceptions. |
| Rel-17 (SA4, user-service layer) | 940008 5G Multicast-Broadcast Protocols (acronym 5MBP3; TS 26.502, TS 26.517; TSG SA#94 approval; rapporteur Thomas Stockhammer, Qualcomm). Both specifications were created directly by this work item rather than added to pre-existing ones, so neither has an "introducing CR" in 3GPP's Change Request database — a brand-new specification's first version is approved directly via the work item's own Tdoc, not tracked as a CR. |
| Rel-18 (SA2/CT core network, "Phase 2") | Parent: 989999 5G multicast-broadcast services Phase 2 (acronym 5MBS_Ph2; TSG SA#98 approval; rapporteur Meng Li, Huawei) Children: 940067 Study on architectural enhancements ... Phase 2 (FS_5MBS_Ph2, the TR 23.700-47 study), 960041 Study on security enhancements ... Phase 2 (TR 33.883), 980013 Stage 2 of 5MBS_Ph2 (TS 23.247's Rel-18 update — see below), 990001 CT1 aspects for 5MBS_Ph2, 990075 CT aspects for 5MBS_Ph2, 990076 CT3 aspects for 5MBS_Ph2 (TS 29.580, TS 29.537), 990077 CT4 aspects for 5MBS_Ph2 (TS 29.532, TS 29.581), 1000005 Security Enhancements ... Phase 2 |
| Rel-18 (RAN) | Parent: 940099 Enhancements of NR Multicast and Broadcast Services (acronym NR_MBS_enh) Child: 940199 Core part: Enhancements of NR Multicast and Broadcast Services (NR_MBS_enh-Core) |
| Rel-18 (charging) | 1000010 Charging Aspects for SMF and MB-SMF to Support 5G Multicast-broadcast Services (TS 32.279, a brand-new specification created by this work item) — recorded as a child of the Rel-17 5MBS umbrella (900038) despite being Rel-18 work; 3GPP work items are sometimes added to an existing umbrella rather than a new one for the later release. |
| Rel-18 (UE pre-configuration) | 990078 UE pre-configuration for 5MBS (acronym UEConfig5MBS; TS 24.575, also a brand-new specification) |
| Rel-19 (NTN) | Tracked under 1020097 Non-Terrestrial Networks (NTN) for NR Phase 3 (acronym NR_NTN_Ph3) and its core child 1021097 NR_NTN_Ph3-Core — a general NTN feature, not an MBS-specific one; the MBS-relevant CRs against TS 23.247 are simply tagged with this acronym alongside the generic TEI19 maintenance code. No dedicated "5MBS Phase 3" work item exists. |
Release 17: the foundational feature
The Rel-17 SA2 architecture work is 5MBS (WI 900038), approved at TSG SA#90 (rapporteur Meng Li, Huawei), following the study phase captured in TR 23.757. Its Stage 2 child work item (900009) delivered TS 23.247, the architectural enhancements defining MBS session concepts (broadcast and multicast delivery, session identifiers, the MB-SMF/MB-UPF network functions) at the core network layer. Four further CT-group children under the same umbrella carried this into stage-3 protocols and NAS: 910002 (CT4, delivering TS 29.532 and TS 29.581), 920044 (CT3, delivering TS 29.580 and TS 29.537), 920043 (CT1) and 960067 (CT6) — confirmed by checking which TSG sub-group actually processed each spec's Change Requests, not merely inferred from the work item names. Security is tracked separately: 920023 delivered the TR 33.850 study.
In parallel, SA4 ran its own work item for the user-service layer: 5MBP3 (WI 940008, "5G Multicast-Broadcast Protocols"), approved at TSG SA#94 with Thomas Stockhammer (Qualcomm) as rapporteur, delivering TS 26.502 (user service architecture) and TS 26.517 (protocols and formats) — the two specifications this project's MBS Client, MBSF and MBSTF components implement against directly.
NR/NG-RAN broadcast support (delivery mode 2: reception without an active RRC connection to a specific session) was also introduced at Rel-17, by CR 0088 to TS 38.212 ("Introduction of NR Multicast and Broadcast Services"), approved at RAN#94-e (2021-11-26, Tdoc RP-212979) — this is the same CR that first defines DCI formats 4_0 and 4_1, later extended at Rel-18 below. TS 29.580 (Nmbsf, CT3) and TS 29.581 (Nmbstf, CT4), the stage-3 protocol services this project's own reference tools (MBSF, MBSTF) implement, were created directly by the matching CT-group children of the 5MBS umbrella above. See Standards: 5G MBS for the complete Rel-17 specification list.
Release 18: RAN multicast in RRC_INACTIVE, charging, and UE pre-configuration
The Rel-18 RAN work is NR_MBS_enh (WI 940099, "Enhancements of NR Multicast and Broadcast Services"), with its core part carried by the child work item NR_MBS_enh-Core (WI 940199). Its headline addition, confirmed by direct comparison of the Rel-17 and Rel-18 issues of the specifications themselves rather than inferred from the work item alone, is letting a UE receive MBS multicast while in RRC_INACTIVE state — in Rel-17, multicast reception required an active RRC connection (RRC_CONNECTED).
Concretely, comparing TS 38.331 V17.17.0 (Rel-17) against V18.10.0 (Rel-18) directly: Rel-18 adds an entire new top-level clause absent from Rel-17, clause 5.10, "MBS multicast reception in RRC_INACTIVE" (with sub-clauses 5.10.1 Introduction, 5.10.2 Multicast MCCH information acquisition, 5.10.3 MRB configuration). This clause was introduced by CR 4490 rev 5, "Introduction of eMBS to RRC", approved at RAN#102 (2023-12-06, Tdoc RP-233907) — "eMBS" (enhanced MBS) is 3GPP's own shorthand for this Rel-18 RAN feature. At the physical layer, comparing TS 38.212 V17.13.0 against V18.8.0: DCI format 4_0's own scope statement changes from "used for the scheduling of PDSCH for broadcast in DL cell" (Rel-17) to "used for the scheduling of PDSCH for broadcast or for multicast in RRC_INACTIVE state in DL cell" (Rel-18), and gains a second scrambling option, Multicast MCCH-RNTI, alongside the existing broadcast MCCH-RNTI — introduced by CR 0173, "Introduction of Rel-18 enhancements of NR Multicast and Broadcast Services", also approved at RAN#102 (2023-11-30, Tdoc RP-233733). The corresponding Stage 2 addition at the core network layer, TS 23.247 clause 6.17 ("Support of Multicast MBS session data reception in UE with RRC_INACTIVE state" — see MBS Multicast Inactive - RAN Procedures for how the two layers connect), was introduced by CR 0149 rev 8 ("Support of MBS multicast reception by UEs in RRC_INACTIVE state"), agreed at SA2#155 and approved at SA#99 (Tdoc SP-230051) under work item 5MBS_Ph2 — bundled in the same Tdoc as two companion CRs, 0159 ("Support RRC_INACTIVE UE receiving multicast MBS data") and 0179 ("Mobility procedures for UEs receiving multicast MBS session data in RRC Inactive state"). The full acquisition path (SIB24, the multicast MCCH, MBSMulticastConfiguration, the DCI 4_0/4_1 split between MCCH and MTCH) is analysed in detail on MBS Multicast Inactive - RAN Procedures.
Two further, independent Rel-18 work items round out the release: UEConfig5MBS (WI 990078, "UE pre-configuration for 5MBS") delivered TS 24.575, the Management Object letting a UE be pre-configured with MBS PLMN/DNN/S-NSSAI information; and WI 1000010 ("Charging Aspects for SMF and MB-SMF to Support 5G Multicast-broadcast Services") delivered TS 32.279, charging management for MBS sessions. An architecture study (TR 23.700-47) and a security study (TR 33.883) accompany this phase.
Every other RAN/PDCP/RLC/MAC/F1AP/E1AP clause this project's own compliance-audit work already relies on (MCCH change-notification timing, the PDCP/RLC MRB receive-window bootstrap, the F1AP Broadcast Context Setup message family, both relevant E1AP clauses) was checked directly against its Rel-18 text and found byte-identical to Rel-17 — the multicast-in-RRC_INACTIVE addition above is the one substantive Rel-18 RAN change identified.
Release 19: non-terrestrial network extensions
Release 19 extends 5G MBS broadcast to non-terrestrial networks (NTN) — satellite and HAPS-based delivery. See MBS Broadcast over NTN for the technical analysis. There is no dedicated "5MBS Phase 3" work item at Rel-19; the feature instead rides on the general NR_NTN_Ph3 ("Non-Terrestrial Networks (NTN) for NR Phase 3") feature, under its core child NR_NTN_Ph3-Core.
At the core network layer, the CR database confirms CR 0372 rev 5 to TS 23.247, "MBS broadcast support for NTN", agreed at SA2#166-Ad Hoc-e and approved at SA#107 (Tdoc SP-250037), tagged NR_NTN_Ph3-Core alongside the generic TEI19 maintenance code. Two companion CRs submitted at the same SA2 meeting (0375, "Definition of MBS service area in case of NR NTN"; 0377, "Supporting MBS broadcast service for NR NTN") were merged into 0372 rather than approved separately. Two later corrections continue the same feature: CR 0387 rev 2, "Clarification on MBS broadcast service area" (SA#108, SP-250461), and CR 0388 rev 3, again titled "MBS broadcast support for NTN" (SA#110, SP-251334) — indicating the feature was still being refined roughly a year after its introduction.
NR_NTN_Ph3-Core does touch TS 38.331 at Rel-19, but not for MBS. 17 Change Requests carry that work item tag against this specification — CR 5481 ("Introduction of NTN Phase 3 enhancements", RAN#109, RP-252778) and CR 5590/5627/5682/5726/5744 (corrections, RAN#110-112) among them — but every one of the 17 subjects is generic NTN work: SMTC timing, cell selection, UE capability signalling, positioning reports. None mentions MBS, multicast or broadcast. The only Rel-19-adjacent TS 38.331 CRs touching both MBS and NTN (4859, 4860, "Correction on multicast DRX to support NTN", RAN#104, RP-241553) are tagged NR_MBS-Core/NR_NTN_solutions-Core — Rel-18 work items, not the Rel-19 NR_NTN_Ph3 family. This page's own linked MBS Broadcast over NTN analysis cites TS 38.331 for this topic and is marked "under development and subject to change"; the CR evidence here is consistent with that — the RAN-layer normative work for Rel-19 MBS-over-NTN does not yet appear to have reached CR stage, even though the Stage 2 (TS 23.247) side has.
References to verify
All work item entries above (900038, 830030, 900009, 910002, 920023, 920043, 920044, 960067, 940008, 940099, 940199, 989999, 940067, 960041, 980013, 990001, 990075, 990076, 990077, 1000005, 990078, 1000010) were each fetched directly from portal.3gpp.org's work item detail pages and confirm their acronym, title, release, responsible group and (where shown) rapporteur and TSG approval meeting number, exactly as stated above. Two work items (940099, 990078) were already named, without their release or child/parent structure, in this project's own Standards: 5G MBS page and in src/data/specs/5g-mbs.js's specification notes; that existing citation was independently re-confirmed against the portal, not merely carried over.
The TS 38.212/TS 38.331 Rel-17-versus-Rel-18 clause comparison (DCI format 4_0's scope, the new clause 5.10) was made by extracting both issues' text directly and diffing the relevant clauses, not inferred from the work item titles.
CR-level detail, unlike the first version of this page, is now established, using this project's own 3GPP Explorer tool: 3GPP's full public Change Request database export (CRDB_20260715.zip, ~597,000 rows) was downloaded and filtered to the specifications this page names. Every CR cited above (TS 38.212 CR 0088 and CR 0173; TS 38.331 CR 4490 rev 5; TS 23.247 CR 0149 rev 8, CR 0159 rev 7, CR 0179 rev 8) was confirmed agreed at working-group level and approved at TSG level in that export, not merely proposed — and each carries the work item acronym its own portal page names (NR_MBS-Core, NR_MBS_enh-Core, 5MBS_Ph2), an independent cross-check between the two data sources. Meeting dates were converted from the export's Excel serial date values (epoch 1899-12-30); TSG meeting numbers and Tdoc numbers are quoted directly from the export, not looked up separately. No 3GPP delegate login was needed for any of this — the CR database itself is public, only per-CR document text (which this page does not quote) sits behind the delegate-only portal the Broadcast page's own references section describes.
The Release 19 NTN section above was resolved the same way: NR_NTN_Ph3/NR_NTN_Ph3-Core (WI 1020097/1021097) were confirmed against the work item portal, and the specific CRs (TS 23.247 CR 0372/0375/0377/0387/0388) were found by searching the CR database for that acronym combined with "MBS"/"broadcast"/"multicast" in the subject text — not by trusting the work plan's own impacted-specs list for this WI, which is empty for 1020097/1021097 in the 2026-06-26 export (a real gap in that source, not evidence either way, which is why the CR database was searched directly instead). Correction, caught by an independent re-verification pass before publishing: an earlier draft of this page claimed no NR_NTN_Ph3-Core-tagged Change Request existed at all against TS 38.331, and called that as strong a claim as the positive findings. That was wrong, and not a small imprecision — the tag is used 17 times against this specification. The corrected claim in the Release 19 section above is the one actually checked: none of those 17 has an MBS/multicast/broadcast-relevant subject (all 17 subjects were read directly, not sampled). An unqualified absence claim and a qualified one are different claims, and only the second was ever actually verified.
One further gap, surfaced by the same re-verification pass and not otherwise resolvable from the sources used here: TS 24.575's attribution to WI 990078 could not be independently confirmed via the work item portal's own "specifications resulting from this work item" listing, which returns no records for 990078 or its own children (990022, 990079) — a gap in that specific portal endpoint, not evidence the attribution is wrong. The CR database extract used elsewhere on this page does not cover TS 24.575, so that route could not cross-check it either. The attribution rests on the specification's own front matter and this project's existing inventory (rt-mbs-specs-index.md), not on this portal endpoint.
The CT1/CT3/CT4 mapping is now resolved. Every CR against all four of TS 29.532/29.580/29.581/29.537 in the database is tagged with only the parent work item acronym (5MBS for Rel-17, 5MBS_Ph2 for Rel-18), not an individual CT-group child code — so the child work item names alone do not distinguish them. The meetingWg field does, though: it names the actual TSG sub-group (e.g. 3GPPCT4#128) that processed each individual CR, independently of the work item tag. Checked exhaustively, not sampled: all 154 of TS 29.532's tracked CRs and all 102 of TS 29.581's went through CT4; all 128 of TS 29.580's and all 73 of TS 29.537's went through CT3. No exceptions in either direction.
Still not established by this page: full meeting-by-meeting history for every CR against every specification. The CRDB holds this, but only the introducing/headline CRs on this page were pulled out; matching the sibling Broadcast page's exhaustive CR-by-CR table would mean doing this for every one of the roughly 450 CRs the filtered export holds across TS 23.247, TS 29.532, TS 29.580, TS 29.581 and TS 29.537 alone, which was judged disproportionate for this pass.
Related Standards Work
- Standards: 5G Multicast Broadcast Services (MBS)
- Standards: 5G Broadcast
- Standards: 5G Broadcast - Standards Evolution
- Standards: Non-Terrestrial Networks (NTN)
- Tech: Multicast & Broadcast in 5G
Refer to the Standards repository to contribute to this documentation.