Description
The MBMS point-to-multipoint Traffic Channel (MTCH) is a unidirectional, downlink logical channel defined within the 3GPP radio interface protocol architecture for Multimedia Broadcast Multicast Service (MBMS). It operates at the Medium Access Control (MAC) layer and is dedicated to carrying the actual user plane data of an MBMS service, such as video streams, file downloads, or audio broadcasts, from the network to a group of user equipments (UEs). The MTCH is mapped to transport channels, specifically the Multicast Channel (MCH) in LTE and the Forward Access Channel (FACH) in UMTS, which are then mapped to physical resources. How it works is intrinsically linked to the MBMS session. When an MBMS session starts, the network configures the necessary radio bearers. The MTCH is associated with a specific Temporary Mobile Group Identity (TMGI) and MBMS Service Area. Data packets for the service are processed by the Packet Data Convergence Protocol (PDCP) and Radio Link Control (RLC) layers, which may apply header compression and segmentation. At the MAC layer, these packets are scheduled onto the MTCH logical channel. In a given cell, all MTCHs for different services are multiplexed onto the same MCH transport channel. UEs interested in receiving a service monitor the MCCH (MBMS Control Channel) for scheduling information, which tells them when and on which subframes the MTCH for their desired service will be transmitted. They then tune in to receive the data broadcast, enabling efficient spectrum usage as a single transmission serves all interested UEs in the coverage area. Its role is fundamental to the point-to-multipoint nature of MBMS, providing the pipe for the content delivery that distinguishes it from unicast traffic channels like the DTCH.
Purpose & Motivation
The MTCH was created to fulfill the need for an efficient, standardized mechanism to deliver identical content to many users simultaneously over a cellular radio interface, a capability not supported by traditional point-to-point (unicast) channels. Before MBMS and the MTCH, delivering popular content like live TV or software updates to a mass audience required establishing individual unicast bearers for each user, which rapidly consumes radio resources and core network bandwidth as the audience grows. This approach is neither scalable nor spectrum-efficient. The MTCH, as part of the broader MBMS framework, solves this problem by enabling true broadcast/multicast at the radio level. It allows a single transmission from the network to be received by an unlimited number of UEs within the coverage area, dramatically improving spectral efficiency for group communication services. Its creation was motivated by the desire to enable mobile TV, live event streaming, public warning systems, and group data delivery (like vehicular software updates) over cellular networks, turning them into a broadcast-capable platform. The MTCH provides the dedicated, service-specific data path that makes these applications feasible.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (47 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-2, normative work from Rel-15.
In Release 15, enhancements for the MTCH function included enabling MBMS bearer event notification and improving MBMS session setup procedures through alignment with RAN WG3. The release also introduced MB2 interface improvements, allowing a GCS AS to request the application of Forward Error Correction (FEC) and/or Robust Header Compression (RoHC) to an MBMS bearer. Furthermore, specific support for RoHC was added to enable Mission Critical services over MBMS.
- Enabling MBMS Bearer Event Notification TS 36.300CR1138
- MBMS reception in Receive Only Mode TS 36.300CR1207
- MBMS session setup procedure /event notification alignment with RAN WG3 TS 23.468CR0080
- MB2 improvements for GCS AS to be able to request application of FEC and/or RoHC to a MBMS bearer TS 23.468CR0081
- Fix missed update to Modify MBMS Bearer procedure - add resources reporting TS 23.468CR0082
- RoHC support for Mission Critical services over MBMS TS 36.300CR1116
+ 10 more changes
In Release 16, the MTCH function itself was not the primary focus of the enhancements. The key developments related to point-to-multipoint traffic delivery involved improvements to the supporting Integrated Access and Backhaul (IAB) infrastructure. Specifically, the release introduced corrections and new procedures for Backhaul (BH) RLC channel management, including mechanisms for transmission suspension upon IAB-Mobile Termination failure and miscellaneous corrections for BH RLC channel operation.
- Mapping of Uplink Traffic to Backhaul RLC Channels TS 38.300CR0255
- CP length and reference signal for MBSFN with sub-carrier spacing of 0.375 kHz and 2.5 kHz TS 36.300CR1322
- Corrections of NR operating with shared spectrum channel access in 38.321 TS 38.321CR0726
- Corrections for NR operating with shared spectrum channel access TS 38.321CR0882
- MAC corrections for NR operating in shared spectrum channel access TS 38.321CR0966
- CR to 38.322 on Backhaul RLC Channel TS 38.322CR0037
+ 7 more changes
In Release 17, specific corrections were made to the MTCH function, including a correction to the description of the `mtch-neighbourCell` field. Additionally, a separate correction was introduced for handling the PLMN index within the MCCH when transmitted on a Secondary Cell (SCell).
- CRS-IM default network configuration assumptions for MBSFN configuration in non-DSS scenario TS 38.331CR3497
- Channel Access Control for msg1/msgA in FR2-2 TS 38.331CR3827
- Correction to RRC for 71 GHz on channel occupancy duration TS 38.331CR3968
- Correction to mtch-neighbourCell field description TS 38.331CR4015
- Correction for PLMN index in MCCH of SCell TS 38.331CR4161
- Correction to support autonomous change of UE channel bandwidth during RACH TS 38.331CR4395
+ 1 more changes
In Release 18, specific corrections were made to the MTCH function to improve multicast service continuity. The release introduced a procedure for multicast reception after a UE reselects to a cell broadcasting an MCCH. Additionally, technical corrections were applied to the handling and release procedures for the associated PC5 RLC channels used for sidelink multicast delivery.
- UE capability for Enhanced channel raster TS 38.331CR4445
- Introduction of new capability for intra-band EN-DC channel spacing [Intra-Band_EN-DC_Channelspacing] TS 38.331CR5013
- Correction on Co-channel coexistence for LTE sidelink and NR sidelink TS 38.321CR1942
- Multicast reception after reselection to cell with MCCH TS 38.331CR5153
- Rapporteur correction on multicast MCCH TS 38.331CR5190
- Correction to PC5 RLC channel handling TS 38.331CR5270
+ 3 more changes
In Release 19, the primary new development for the MTCH function was the introduction of a 7MHz channel bandwidth. This defines a new, wider RF bandwidth to support a single RF carrier for the downlink transmission, measured in MHz and used as a reference for transmitter and receiver requirements. No other changes to the MTCH are indicated by the provided CR titles or grounding context.
Explore further
Broader topics and technologies where MTCH plays a role.
Defining Specifications
3GPP specifications that define or reference MTCH, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TR 21.905 vj00 | 3GPP Technical Terms and Definitions | Rel-19 |
| TS 23.468 vj00 | Group Communication System Enablers for LTE | Rel-19 |
| TS 23.768 vc10 | Group Communication System Enablers for LTE | Rel-12 |
| TS 25.102 vj00 | UTRA TDD RF Characteristics | Rel-19 |
| TS 25.301 vj00 | UE-UTRAN Radio Interface Protocol Architecture | Rel-19 |
| TS 25.302 vj00 | UTRA Physical Layer Services | Rel-19 |
| TS 25.304 vj00 | UTRA Idle Mode Procedures Specification | Rel-19 |
| TS 25.321 vj00 | MAC Protocol Specification for UTRAN | Rel-19 |
| TS 25.322 vj00 | RLC Protocol Specification | Rel-19 |
| TS 25.331 vj00 | UTRAN RRC Protocol Specification | Rel-19 |
| TS 25.346 vj00 | MBMS in UTRA Technical Specification | Rel-19 |
| TS 25.401 vj00 | UTRAN Overall Architecture | Rel-19 |
| TS 25.402 vj00 | UTRAN Synchronisation Mechanisms | Rel-19 |
| TR 25.912 vj00 | Evolved UTRA and UTRAN Technical Report | Rel-19 |
| TS 36.300 vj00 | E-UTRAN Radio Interface Protocol Architecture Overview | Rel-19 |
| TS 36.302 vj00 | E-UTRA Physical Layer Services | Rel-19 |
| TS 36.304 vj00 | UE Idle Mode Procedures in E-UTRA | Rel-19 |
| TS 36.322 vj00 | E-UTRA Radio Link Control Protocol Specification | Rel-19 |
| TR 36.976 vj00 | LTE-based 5G Terrestrial Broadcast Overview | Rel-19 |
| TS 38.300 vj00 | NG-RAN Overall Description | Rel-19 |
| TS 38.304 vj00 | UE RRC_IDLE and RRC_INACTIVE Procedures | Rel-19 |
| TS 38.321 vj00 | NR MAC Protocol Specification | Rel-19 |
| TS 38.322 vj00 | NR Radio Link Control (RLC) Protocol | Rel-19 |
| TS 38.323 vj00 | Packet Data Convergence Protocol (PDCP) | Rel-19 |
| TS 38.331 vj00 | NR Radio Resource Control (RRC) Protocol Specification | Rel-19 |
| TS 38.523 vj20 | 5G NR UE Conformance Testing: Idle/Inactive | Rel-19 |