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
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (121 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-4, normative work from Rel-15.
In Release 15, the primary new introduction for the RAT function was the foundational support for the New Radio (NR) access technology, enabling 5G. This release also specifically enhanced inter-RAT operations, such as handover from EN-DC and improvements to procedures for inter-RAT mobility, cell reselection in RRC_INACTIVE state, and CGI reporting towards NR. Furthermore, it introduced mechanisms for transferring UE radio capability between AMFs and sending secondary RAT usage data during handover with an AMF change.
- Introduction of New Radio Access Technology in TS 36.300 TS 36.300CR0998
- Introduction of increased number of E-UTRAN data bearers TS 36.306CR1613
- Introduction of increased number of E-UTRAN data bearers TS 36.331CR3446
- RAT Selector for PWS TS 29.518CR0001
- Transfer UE Radio Capability between AMFs TS 29.518CR60
- Sending Secondary RAT usage over N14 during N2 handover with AMF change TS 29.518CR135
+ 41 more changes
In Release 16, key RAN enhancements included the introduction of a second SMTC for inter-RAT cell reselection and specific support for inter-RAT handover from NR to EN-DC. The release also introduced new UE radio access capabilities for Industrial IoT and established procedures for Radio Capability Optimisation (RACS) and UE Radio Capability Mapping for EN-DC. Furthermore, it provided corrections and enhancements for even further mobility improvements in E-UTRAN and for cross-RAT V2X functionality.
- Add NB-IoT specific UE Radio Access Capability in UE context TS 29.518CR184
- Transferring UE Radio Capability ID between AMFs TS 29.518CR0248
- Introduction of even further mobility enhancement in E-UTRAN TS 36.300CR1270
- Introduction of UE capability indicator of supporting inter-RAT handover from NR to EN-DC in 36.306 TS 36.306CR1745
- UE radio access capabilities introduction for IIOT WI (CR for 36.306) TS 36.306CR1758
- Introduction of a second SMTC for inter-RAT cell reselection TS 36.331CR4114
+ 23 more changes
In Release 17, key RAT enhancements included the formal introduction of RAT Types for Satellite access and specific capabilities for inter-RAT operations, such as a UE capability for inter-RAT NR FR2 measurements without a measurement gap. The release also introduced procedures like the Secondary RAT Usage Report and defined enhancements for multi-RAT dual-connectivity, alongside mobility corrections to handle areas with only GERAN or UTRAN coverage. Furthermore, it specified mechanisms for transferring UE radio capability for paging between AMFs and introduced a cell-specific offset for inter-RAT measurement in LTE for NR neighbors.
- 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
- UE Security Capabilities signaling in E-UTRAN [UE_Sec_Caps] TS 36.300CR1359
- Secondary RAT Usage Report TS 29.274CR2028
- 5G-SRVCC from NG-RAN to UTRAN Handover Cancellation TS 29.274CR2040
+ 8 more changes
In Release 18, key RAT enhancements included new procedures to ensure Location Services (LCS) continuity during inter-RAT mobility and introduced specific enhancements for mobile Integrated Access and Backhaul (mIAB) nodes to improve inter-RAT cell reselection. The release also introduced a defined procedure for measurement sequences for both intra-RAT and inter-RAT measurements and implemented protections against improper reselection to legacy GERAN/UTRAN networks. Furthermore, corrections and clarifications were made for inter-RAT and intra-RAT operations, such as for NB-IoT cell selection and for radio bearer handling during cell switch execution in NR-Dual Connectivity.
- LCS continuity during inter-RAT mobility TS 29.274CR2080
- Protection against improper reselection to GERAN/UTRAN [RESELECTION_TO GSM_AND_UTRAN] TS 36.304CR0866
- Introduction of mIAB Inter-RAT cell reselection enhancements for 36.304 [TEI18_MIAB_IRAT] TS 36.304CR0870
- Protection against improper reselection to GERAN/UTRAN [RESELECTION_TO GSM_AND_UTRAN] TS 36.306CR1874
- Introduction of mIAB Inter-RAT cell reselection enhancements for 36.306 [TEI18_MIAB_IRAT] TS 36.306CR1882
- Protection against improper reselection to GERAN/UTRAN [RESELECTION_TO GSM_AND_UTRAN] TS 36.331CR4971
+ 12 more changes
In Release 19, key RAN enhancements focused on integrating Non-Terrestrial Networks (NTN), specifically for NB-IoT over satellite. This included introducing NB-IoT satellite information in E-UTRAN and defining UE capabilities and band list indications for mobility and redirection between terrestrial E-UTRAN and NB-IoT NTN. The release also finalized procedures for reporting Secondary RAT Usage Data and clarified UE Radio Capability handling for Indirect Network Sharing.
- Clarification on UE Radio Capability ID for Indirect Network sharing TS 29.518CR1191
- Introduction of NB-IoT satellite information in E-UTRAN [EUTRAN-to-NBIoTNTN] TS 36.300CR1427
- Restriction on RAT utilization TS 36.300CR1432
- Restriction on RAT utilization TS 36.304CR0884
- Introduction of E-UTRAN to NB-IoT NTN Mobility UE Capability [EUTRAN-to-NBIoTNTN] TS 36.306CR1917
- Introduction of NB-IoT satellite information in E-UTRAN [EUTRAN-to-NBIoTNTN] TS 36.331CR5140
+ 7 more changes
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 |