Description
A Radio Access Technology (RAT) is the complete set of technical specifications and implementations that define the air interface and associated network functions for wireless communication between user equipment (UE) and the core network. It encompasses the physical layer (modulation, coding, duplexing), the data link layer (medium access control, radio link control), and key radio resource management procedures. Each RAT, such as GSM (2G), UMTS (3G), LTE (4G), and NR (5G), has a distinct architecture: GSM uses TDMA/FDMA with Base Station Subsystems; UMTS employs W-CDMA with NodeBs and RNCs; LTE utilizes OFDMA/SC-FDMA with a simplified eNodeB; NR uses flexible OFDMA with gNBs. The RAT defines the specific protocols for random access, channel establishment, handover, power control, and scheduling. It works by converting digital data into radio waves transmitted over specific frequency bands, with the base station (eNodeB, gNB) managing radio resources for multiple UEs. Key components include the UE's radio transceiver, the base station's radio unit and baseband processor, and the defined channel structures (physical, transport, logical). Its role is to provide the wireless link that carries user data and control signaling, forming the essential bridge between mobile devices and the core network. Modern networks are multi-RAT, with UEs and networks capable of operating across several RATs (e.g., LTE and NR), managed through mechanisms like inter-RAT mobility and carrier aggregation. The RAT fundamentally determines key performance indicators like data rate, latency, coverage, and capacity.
Purpose & Motivation
RATs exist to standardize wireless communication, enabling interoperability between devices and networks globally. Each new RAT generation is created to solve the limitations of its predecessors, driven by increasing demands for higher data rates, lower latency, greater capacity, and new service types. GSM (2G) introduced digital voice and SMS, moving beyond analog. UMTS (3G) addressed the need for mobile broadband data. LTE (4G) was developed to provide all-IP, high-speed data with simplified architecture, overcoming the complexity and inefficiency of UMTS's dedicated channels. NR (5G) is designed for extreme broadband, ultra-reliable low latency, and massive IoT, tackling LTE's limitations in latency and flexibility for diverse use cases. The evolution of RATs is motivated by spectrum efficiency improvements, technological advancements (like MIMO, advanced coding), and changing user demands. Multi-RAT operation is crucial for seamless service continuity, allowing networks to leverage existing infrastructure (e.g., LTE coverage) while deploying new technologies (NR). Standards bodies like 3GPP define these RATs to ensure a cohesive ecosystem, preventing fragmentation and enabling economies of scale.
Classification
Release Timeline
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (77 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the RAT function was enhanced with new procedures for inter-RAT mobility, including handover support from EN-DC and GERAN/UTRAN to E-UTRA configured with EN-DC, and specific corrections for inter-RAT cell reselection in the RRC_INACTIVE state. The release introduced mechanisms like sending secondary RAT usage data over the N14 interface during handover and clarified full configuration for inter-RAT handover. Additionally, it added NR to co-existence requirements for single RAT base stations and provided corrections for inter-RAT measurement and mobility procedures.
- Introduction of New Radio Access Technology in TS 36.300 TS 36.300CR0998
- RAT Selector for PWS TS 29.518CR0001
- Sending Secondary RAT usage over N14 during N2 handover with AMF change TS 29.518CR135
- Support for inter-RAT handover from EN-DC TS 36.300CR1148
- Inter-RAT Handover from GERAN or UTRAN to E-UTRA configured with EN-DC (36.300) TS 36.300CR1200
- Corrections to 36.304 speed dependent mobility and inter-RAT cells with cell reservations, access restrictions, or unsuitable for normal camping TS 36.304CR0748
+ 26 more changes
In Release 16, key RAT-related enhancements focused on improving inter-RAT mobility and measurement capabilities, specifically introducing support for inter-RAT handover from NR SA to EN-DC and enabling a second SMTC for inter-RAT cell reselection. It also introduced new UE capability indicators for such handovers and added mechanisms for failure recovery via Conditional Handover (CHO) for inter-RAT handover failures. Furthermore, corrections and support were added for cross-RAT V2X functionality and inter-RAT RRM measurements on NR-U.
- Introduction of UE capability indicator of supporting inter-RAT handover from NR to EN-DC in 36.306 TS 36.306CR1745
- Introduction of a second SMTC for inter-RAT cell reselection TS 36.331CR4114
- Support of inter-RAT handover from NR to EN-DC in TS 36.331 TS 36.331CR4232
- Support of inter-RAT handover from NR to EN-DC in TS 38.331 TS 38.331CR1505
- CR to 36.300 on support of inter-RAT HO from SA to EN-DC TS 36.300CR1286
- Correction on RLF Report for Inter-RAT MRO NR TS 36.306CR1778
+ 11 more changes
In Release 17, key RAT-related enhancements included the formal introduction of RAT Types for Satellite access and new UE capabilities for inter-RAT NR FR2 measurements without requiring a measurement gap. The release also introduced further multi-RAT dual-connectivity enhancements and specified mechanisms for Secondary RAT data usage reporting, including reporting over the N14 interface during Inter-AMF handover.
- RAT Type TS 29.274CR2043
- Introduction of further multi-RAT dual-connectivity enhancements TS 36.331CR4774
- Introduction of further multi-RAT dual-connectivity enhancements TS 38.331CR2954
- Secondary RAT Usage Report TS 29.274CR2028
- RAT Types for Satellite TS 29.274CR2053
- Introduction of UE capability for inter-RAT NR FR2 measurements without measurement gap TS 36.306CR1873
+ 3 more changes
In Release 18, key RAN enhancements focused on improving inter-RAT mobility and measurement procedures, including introducing a specific procedure for the measurement sequence for both intra-RAT and inter-RAT measurements. The release also brought enhancements for mobile Integrated Access and Backhaul (mIAB) nodes, specifically for inter-RAT cell reselection across multiple technical specifications. Furthermore, it provided clarifications and corrections for inter-RAT operations, such as for NB-IoT cell selection and FR2 measurement capabilities.
- LCS continuity during inter-RAT mobility TS 29.274CR2080
- Introduction of mIAB Inter-RAT cell reselection enhancements for 36.304 [TEI18_MIAB_IRAT] TS 36.304CR0870
- Introduction of mIAB Inter-RAT cell reselection enhancements for 36.306 [TEI18_MIAB_IRAT] TS 36.306CR1882
- Introduction of mIAB Inter-RAT cell reselection enhancements for 36.331 [TEI18_MIAB_IRAT] TS 36.331CR4993
- Introducing procedure for measurement sequence for intra-RAT and inter-RAT measurement [MeasSequence] TS 38.331CR4439
- CR for TS 36.104: Operating band unwanted emissions for Single RAT BS supporting multi-band operation TS 36.104CR4976
+ 7 more changes
In Release 19, key enhancements for the RAT function introduced new restrictions on RAT utilization and defined conditionally mandatory support for inter-RAT configuration when using dedicated NR FR1 spectrum less than 5MHz. The release also included updates for the Secondary RAT Usage Data Report and removed an editor's note related to Secondary RAT procedures. These changes build upon existing PLMN selection procedures where RAT choice is prioritized after network selection.
- Restriction on RAT utilization TS 25.304CR0395
- Restriction on RAT utilization TS 36.300CR1432
- Restriction on RAT utilization TS 36.304CR0884
- Restriction on RAT utilization TS 38.304CR0446
- Remove the editor's note for Secondary RAT Usage Data Report TS 29.274CR2122
- Conditionally mandatory support for inter-RAT configuration for dedicated spectrum less than 5MHz for NR FR1 TS 36.306CR1941
Explore further
Broader topics and technologies where RAT plays a role.
Defining Specifications
3GPP specifications that define or reference RAT, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 21.810 v1300 | Multi-mode UE Issues - Categories, principles and procedures | Rel-4 |
| TR 21.905 vj00 | 3GPP Technical Terms and Definitions | Rel-19 |
| TR 21.910 v1300 | Multi-mode UE Operation Principles | Rel-4 |
| TS 22.811 v1700 | Network Selection Mechanisms Overview | Rel-7 |
| TS 22.822 vg00 | Satellite Access in 5G Study | Rel-16 |
| TR 22.980 vj00 | Network Composition Feasibility Study | Rel-19 |
| TS 23.279 vj00 | Combined CS and IMS Services (CSI) Architecture | Rel-19 |
| TS 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TS 25.104 vj00 | UTRA FDD Base Station RF Characteristics | Rel-19 |
| TS 25.105 vj00 | UTRA TDD Base Station RF Requirements | Rel-19 |
| TS 25.123 vj00 | Radio Resource Management for TDD | Rel-19 |
| TS 25.133 vj00 | UTRAN RRM Requirements for FDD | Rel-19 |
| TS 25.141 vj00 | UTRA FDD Base Station RF Conformance Testing | Rel-19 |
| TS 25.142 vj00 | UTRA TDD Base Station RF Test Methods | Rel-19 |
| TS 25.304 vj00 | UTRA Idle Mode Procedures Specification | Rel-19 |
| TS 25.331 vj00 | UTRAN RRC Protocol Specification | Rel-19 |
| TS 25.367 vj00 | Home NodeB Mobility Procedures | Rel-19 |
| TS 25.413 vj00 | Radio Access Network Application Part (RANAP) | Rel-19 |
| TR 25.912 vj00 | Evolved UTRA and UTRAN Technical Report | Rel-19 |
| TS 26.891 vg00 | Media Distribution Services in 5G System | Rel-16 |
| TR 26.938 vj00 | DASH Deployment Guidelines for 3GPP Networks | Rel-19 |
| TS 28.661 vj00 | Generic RAN NRM IRP Requirements | Rel-19 |
| TR 28.808 vh00 | 5G satellite integration management study | Rel-17 |
| TR 28.841 vi01 | Technical Report on IoT NTN Enhancements | Rel-18 |
| TS 29.274 vj50 | GTPv2-C Control Plane Protocol Specification | Rel-19 |
| TS 29.518 vj50 | AMF Service Based Interface Protocol | Rel-19 |
| TS 32.405 vj00 | UTRAN Performance Measurements Specification | Rel-19 |
| TS 32.406 vj00 | Performance Management for CN PS Domain | Rel-19 |
| TS 32.450 vj00 | E-UTRAN Key Performance Indicators (KPI) Definitions | Rel-19 |
| TS 32.451 vj00 | KPI Requirements for E-UTRAN | Rel-19 |
| TS 32.791 vb00 | Common RAT NRM IRP Requirements | Rel-11 |
| TS 32.827 va10 | UE Management over Itf-N for MDT/SON | Rel-10 |
| TS 32.834 vb00 | Inter-RAT Energy Saving Management Study | Rel-11 |
| TR 33.739 vi10 | Study on security enhancement of support for | Rel-18 |
| TS 33.836 vg10 | Security Study for Advanced V2X Services | Rel-16 |
| TR 33.847 vh10 | 5G Proximity Services Security Study | Rel-17 |
| TR 33.853 vh00 | Study on User Plane Integrity Protection | Rel-17 |
| TS 33.859 vb10 | UTRAN Key Hierarchy Enhancement Study | Rel-11 |
| TS 36.104 vj10 | Base Station (BS) radio transmission and reception | Rel-19 |
| TS 36.116 vj00 | E-UTRA Relay RF Requirements | Rel-19 |
| TS 36.117 vj00 | E-UTRA Relay RF Test Methods & Requirements | Rel-19 |
| TS 36.133 vj20 | E-UTRA RRM Requirements | Rel-19 |
| TS 36.141 vj00 | E-UTRA BS Conformance Testing | 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 36.306 vj00 | E-UTRA UE Radio Access Capability Parameters | Rel-19 |
| TS 36.331 vj00 | LTE RRC Protocol Specification | Rel-19 |
| TS 36.410 vj00 | S1 Interface: General Aspects and Principles | Rel-19 |
| TR 36.902 v931 | SON Use Cases and Solutions for LTE | Rel-9 |
| TS 37.104 vj10 | MSR Base Station RF Characteristics | Rel-19 |
| TS 37.105 vj10 | AAS Base Station Transmission & Reception Requirements | Rel-19 |
| TS 37.113 vj00 | EMC Requirements for Multi-Standard Radio Base Stations | Rel-19 |
| TS 37.141 vj10 | RF Test Methods for Multi-Standard Radio Base Stations | Rel-19 |
| TS 37.145 vj10 | AAS Base Station Conducted Conformance Testing | Rel-19 |
| TS 37.320 vj00 | Minimization of Drive Tests (MDT) Overview | Rel-19 |
| TS 37.801 va00 | UMTS/LTE 3500 MHz Band Study | Rel-10 |
| TS 37.802 va10 | MSR BS RF Requirements for Non-Contiguous Spectrum | Rel-10 |
| TS 37.808 vc00 | PIM Handling for Base Stations Study | Rel-12 |
| TS 37.810 vc20 | Study on Base Station Specification Structure | Rel-12 |
| TS 37.812 vb30 | Multi-band Multi-standard Radio BS Requirements | Rel-11 |
| TS 37.813 vc00 | LTE-HRPD SON Use Cases & Solutions | Rel-12 |
| TR 37.900 vj00 | Multi-Standard Radio (MSR) Base Station Requirements | Rel-19 |
| TS 38.113 vj00 | NR Base Station EMC Specification | Rel-19 |
| TS 38.133 vj20 | 5G UE Radio Requirements for RRC_IDLE Mobility | Rel-19 |
| TS 38.161 vj10 | NR UE TRP and TRS Requirements for FR1 | Rel-19 |
| TS 38.175 vj00 | EMC for NR IAB Nodes | Rel-19 |
| TS 38.304 vj00 | UE RRC_IDLE and RRC_INACTIVE Procedures | Rel-19 |
| TS 38.331 vj00 | NR Radio Resource Control (RRC) Protocol Specification | Rel-19 |
| TS 38.410 vj10 | NG Interface Introduction for NG-RAN to 5GC | Rel-19 |
| TS 38.523 vj20 | 5G NR UE Conformance Testing: Idle/Inactive | Rel-19 |
| TR 38.803 ve40 | Study on Coexistence and RF Feasibility for 5G NR | Rel-14 |
| TR 38.808 vh00 | Study on NR above 52.6 GHz to 71 GHz | Rel-17 |
| TS 38.811 vf40 | Study on NR Support for Non-Terrestrial Networks | Rel-15 |
| TS 38.817 | 3GPP TR 38.817 | Rel-4 |
| TR 38.859 vi10 | Technical Report | Rel-18 |
| TR 38.882 vi00 | Technical Report on UE Location Service | Rel-18 |
| TR 38.889 vg00 | NR-based access to unlicensed spectrum study | Rel-16 |
| TR 38.913 vj00 | Next Gen Access Tech Scenarios & Requirements | Rel-19 |
| TS 43.055 vj00 | Dual Transfer Mode (DTM) for GSM/GPRS | Rel-19 |
| TS 43.129 vj00 | PS Handover in GERAN A/Gb and GAN Modes | Rel-19 |
| TS 43.318 vj00 | Generic Access Network (GAN) Stage 2 | Rel-19 |
| TR 43.902 vj00 | GAN Enhancements Feasibility Study | Rel-19 |
| TS 44.318 vj00 | Generic Access Network (GAN) Interface Procedures | Rel-19 |
