Description
Mobile Terminated Short Message Service (MT-SMS) is the process by which a Short Message Service Center (SMSC) delivers a text message to a User Equipment (UE). The architecture involves several network entities: the originating entity (which could be another UE or an application), the SMSC, the Home Location Register (HLR) or Home Subscriber Server (HSS) for routing information, the Mobile Switching Center (MSC) for circuit-switched networks, or the Mobility Management Entity (MME) and Serving GPRS Support Node (SGSN) for packet-switched networks in later releases. The process begins when the SMSC receives a message for a subscriber. It queries the HLR/HSS to obtain the current routing information (e.g., the serving MSC or SGSN/MME address). The SMSC then forwards the message to this serving node via the MAP (Mobile Application Part) protocol in GSM/UMTS or Diameter in LTE/5G. The serving node pages the UE and, upon response, establishes the necessary signaling connection to deliver the SMS payload. In LTE and 5G, SMS can be delivered over both Circuit-Switched Fallback (CSFB) and the IP Multimedia Subsystem (IMS) via the SGs and SGd interfaces, respectively, or directly over the Non-Access Stratum (NAS) as SMS over NAS. The MT procedure is tightly integrated with mobility management, ensuring message delivery even when the user is roaming. It supports both point-to-point and cell broadcast modes. Reliability mechanisms include delivery reports and retry attempts upon failure. The service is defined across a vast range of 3GPP specifications, covering service requirements, architecture, protocols, and charging.
Purpose & Motivation
The purpose of MT-SMS is to provide a reliable, store-and-forward mechanism for delivering text messages to mobile subscribers. It solved the problem of asynchronous, non-real-time communication where the recipient might be temporarily unavailable (e.g., powered off or out of coverage). Before SMS, mobile communication was primarily voice-centric. SMS introduced a low-bandwidth, highly efficient data service that leveraged existing signaling channels, minimizing network impact. Its creation was motivated by the need for a simple, ubiquitous messaging service that could work across all GSM (and later 3GPP) networks globally. It addressed the limitation of requiring both parties to be simultaneously available, as required by voice calls. The MT component specifically ensures that the network can initiate delivery to a mobile device, which is essential for any service where the originator is not the UE itself, such as alerts, notifications, and application-to-person messages. Its standardization ensured interoperability between different network operators and equipment vendors, which was crucial for its global success.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (81 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, specific corrections and enhancements were introduced for the Mobile Terminated (MT) function, including a corrected MT NIDD procedure and the addition of an RDS indication within the MT NIDD acknowledgement. These updates also encompassed successful code corrections for group message delivery APIs and improvements to the handling of HTTP message retransmissions.
- Introduction of shortened TTI and processing time for LTE TS 36.331CR3202
- CR on message content in inter-RAT handover TS 38.300CR0030
- SI message scheduling enhancement to avoid conflicts between legacy and positioning System Information TS 36.331CR3596
- Correction to AT+CSCON when MT connected to NR TS 27.007CR0586
- New AT Command for enabling reporting of LADN information from the MT +CLADN TS 27.007CR0621
- OpenAPI updates for MSISDN-less Mobile Originated SMS TS 29.122CR0027
+ 19 more changes
In Release 16, the MT (Mobile Termination) function saw enhancements for specific services, including the introduction of Mobile Terminated Data Transfer over the N16 interface and the removal of the SHORT_DELAY_STORED mechanism. These updates were part of broader optimizations, such as those for Control Plane CIoT 5GS, and included clarifications for procedures like the UE CONTEXT MODIFICATION REQUEST message.
- Indicating to the MT the user's intention for requesting access to RLOS TS 27.007CR0656
- Mobile Originated Data Transfer for Control Plane CIoT 5GS Optimisation TS 29.502CR0228
- MT Data Transfer N16 TS 29.502CR0296
- Remote Interference Management Message Transfer Support TS 38.410CR0017
- Add UE requested V2XP message into +CSUEPOLICY TS 27.007CR0700
- Remove SHORT_DELAY_STORED TS 29.122CR0140
+ 11 more changes
In Release 17, specific enhancements for the Mobile Termination (MT) function included updates to support L2TP within both RADIUS and Diameter message flows, which are protocols used for authentication and authorization. Furthermore, the release introduced a new command for sending EAP messages specifically for relay authentication procedures. These changes refined the MT's role in managing the PLMN access interface during service establishment and messaging.
- Add command for EAP message for relay authentication TS 27.007CR0785
- Updates to support L2TP in RADIUS message flow TS 29.061CR0537
- Updates to support L2TP in Diameter message flow TS 29.061CR0538
- Sending UUAA Authentication message TS 29.502CR0493
- Correction on the SidelinkUEInformationNR message TS 38.300CR0744
- Correction on the user consent in PATH SWITCH REQUEST ACKNOWLEDGE message (REL-17) TS 38.413CR0920
+ 5 more changes
In Release 18, the key new feature for the MT function is the introduction of Mobile-Terminated Small Data Transmission (MT-SDT), which adds a new trigger condition for this procedure. The release also includes corrections and enhancements to the MT Communication Handling Procedures to ensure proper operation. Furthermore, support was added for including the downlink data size within the RAN PAGING REQUEST message to facilitate MT-SDT.
- Support of Mobile Base Station Relay in SMF services TS 29.502CR0678
- Introduction of MT-SDT in Stage-2 TS 38.300CR0711
- Introduction of Mobile IAB TS 38.300CR0727
- Introduction on MT-SDT TS 38.300CR0751
- Introduction of mobile IAB in TS 38.340 TS 38.340CR0033
- (CR to 38.413) Support for mobile IAB TS 38.413CR0988
+ 13 more changes
In Release 19, the key enhancement for the Mobile Termination (MT) function was the clarification of handover procedures for WAB-MT, improving the reliability of mobility management for the PLMN access interface component. This update specifically refined the network-triggered handover evaluation process based on the measured radio environment. No other MT-specific changes were introduced in this release.
- Add message flows of converged charging for UE positioning assisted by Sidelink Positioning and involving 5GC TS 32.271CR0022
- Add message flows of converged charging for Ranging and Sidelink Positioning service exposure TS 32.271CR0024
- Introduction of Message content for Ranging and Sidelink Positioning converged charging TS 32.271CR0025
- Introduction of Detailed message format for Ranging and Sidelink Positioning converged charging TS 32.271CR0027
- Add message flow of converged charging for 5GC-MT-LR TS 32.271CR0031
- Add message flow of converged charging for 5GC-MO-LR TS 32.271CR0032
+ 3 more changes
Explore further
Broader topics and technologies where MT plays a role.
Defining Specifications
3GPP specifications that define or reference MT, 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 |
| TR 21.978 v1300 | CAMEL Control of VoIP Services Feasibility Study | Rel-4 |
| TS 22.031 vj00 | Fraud Information Gathering System (FIGS) Stage 1 | Rel-19 |
| TS 22.034 vj00 | High Speed Circuit Switched Data (HSCSD) Stage 1 | Rel-19 |
| TS 22.101 vk00 | Service Principles for PLMNs | Rel-20 |
| TS 22.105 vj00 | Telecommunication Services Framework | Rel-19 |
| TR 22.944 vj00 | UE Functionality Split Scenarios and Requirements | Rel-19 |
| TS 23.018 vj00 | Basic call handling in 3GPP CS domain | Rel-19 |
| TS 23.031 vj00 | Fraud Information Gathering System (FIGS) - Stage 2 | Rel-19 |
| TS 23.035 vj00 | Immediate Service Termination (IST) Stage 2 | Rel-19 |
| TS 23.050 v1100 | UMTS Network Principles and Architecture | R99 |
| TS 23.057 vj00 | Mobile Execution Environment (MExE) Specification | Rel-19 |
| TS 23.060 vj00 | GPRS Service Description Stage 2 | Rel-19 |
| TS 23.078 vj00 | CAMEL Phase 4 Stage 2 Specification | Rel-19 |
| TS 23.101 vj00 | UMTS Architecture and Functional Separation | Rel-19 |
| TS 23.107 vj00 | UMTS QoS Framework | Rel-19 |
| TS 23.146 vj00 | 3G Facsimile Group 3 Technical Realization | Rel-19 |
| TS 23.207 vj00 | End-to-End QoS Framework for GPRS | Rel-19 |
| TS 23.218 vj00 | IMS Call Model Specification | Rel-19 |
| TS 23.278 vj00 | CAMEL for IMS Stage 2 Specification | Rel-19 |
| TS 23.540 vj20 | 5G Service Based SMS Stage 2 | Rel-19 |
| TS 23.725 vg20 | Study on URLLC Architecture Enhancements | Rel-16 |
| TR 23.910 v1400 | UMTS Circuit Switched Bearer Services Overview | Rel-5 |
| TR 23.923 v1300 | Mobile IP+ Feasibility Study for UMTS/GPRS | Rel-4 |
| TS 25.222 vj00 | UTRA TDD Multiplexing & Channel Coding | Rel-19 |
| TS 26.130 vj00 | RTP Payload Format Testing for 3GPP Codecs | Rel-19 |
| TS 27.007 vj40 | AT Command Set for UE | Rel-19 |
| TS 27.060 vj00 | TE-MT Interworking for Packet Domain | Rel-19 |
| TR 28.816 vh00 | Charging for 5G Cellular IoT | Rel-17 |
| TS 29.061 vj00 | Packet Domain Interworking for PLMN | Rel-19 |
| TS 29.078 vj00 | CAMEL Phase 4 CAP Specification | Rel-19 |
| TS 29.122 vj40 | T8 Reference Point for Northbound APIs | Rel-19 |
| TS 29.502 vj50 | 5G System; Nsmf Service Based Interface; Stage 3 | Rel-19 |
| TS 29.542 vj30 | SMF NIDD Service Based Interface Stage 3 | Rel-19 |
| TS 32.102 vj00 | Telecom Management Physical Architecture Framework | Rel-19 |
| TS 32.240 vj40 | Charging Management Architecture & Principles | Rel-19 |
| TS 32.251 vj00 | PS Domain Charging Management | Rel-19 |
| TS 32.270 vj00 | MMS Charging Management Specification | Rel-19 |
| TS 32.271 vj20 | 3GPP LCS Charging Management Spec | Rel-19 |
| TS 32.272 vj00 | Charging for Push-to-Talk over Cellular (PoC) | Rel-19 |
| TS 32.276 vj00 | VCS Online Charging from Proxy Function | Rel-19 |
| TS 32.293 vj00 | Proxy Function in Domestic Service Provider | Rel-19 |
| TS 32.849 vd00 | IMS Roaming Charging Study | Rel-13 |
| TS 36.331 vj00 | LTE RRC Protocol Specification | Rel-19 |
| TS 38.201 vj00 | NR Physical Layer General Description | Rel-19 |
| TS 38.300 vj00 | NG-RAN Overall Description | Rel-19 |
| TS 38.340 vj00 | Backhaul Adaptation Protocol (BAP) Specification | Rel-19 |
| TS 38.410 vj10 | NG Interface Introduction for NG-RAN to 5GC | Rel-19 |
| TS 38.413 vj10 | NG Application Protocol (NGAP) | Rel-19 |
| TS 43.802 vc00 | GERAN Enhancements for Mobile Data Applications | Rel-12 |