Description
The Radio Access Network (RAN) constitutes the critical infrastructure that facilitates wireless communication between User Equipment (UE) such as smartphones and IoT devices, and the operator's core network. It is responsible for all the radio-related functions, including transmitting and receiving radio signals, modulating/demodulating data, managing the radio spectrum, and handling the mobility of users as they move. Physically, the RAN consists of cell sites equipped with antennas and radio equipment (often called base stations), which are interconnected via backhaul links (microwave or fiber) to centralized or distributed processing units.
Architecturally, the RAN has evolved through generations. In 2G/3G (GSM/UMTS), it was a hierarchical network with a Base Transceiver Station (BTS/NodeB) and a centralized Radio Network Controller (RNC). The 4G LTE RAN introduced a flattened architecture with the eNodeB, which integrated the controller functions into the base station itself, reducing latency. The 5G NR RAN further evolved with the gNodeB (gNB) and introduced concepts like Centralized Unit (CU) and Distributed Unit (DU) splits, allowing for more flexible and cloud-native deployments. Regardless of the generation, the RAN performs key functions: radio resource management (scheduling, power control), connection mobility control (handovers), radio admission control, and measurement reporting.
At the protocol layer, the RAN implements the stack across the physical layer (PHY), Medium Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP), and Radio Resource Control (RRC). These layers handle tasks from raw bit transmission over the air to establishing and maintaining radio bearers for user data and signaling. The RAN interfaces with the core network via standardized interfaces: the Iu interface in 3G, the S1 interface in 4G, and the NG interface in 5G. It is the RAN's performance—its spectral efficiency, latency, and reliability—that directly dictates the end-user experience for all mobile services, from voice calls to ultra-reliable low-latency communications (URLLC).
Purpose & Motivation
The Radio Access Network exists to bridge the gap between the wired core network and the multitude of wireless end-user devices. Its fundamental purpose is to provide ubiquitous radio coverage and capacity, enabling mobile communication. Without the RAN, the core network's services would be inaccessible to mobile users. It solves the problem of delivering reliable, high-quality wireless connectivity to users who are moving and whose connection characteristics are constantly changing due to factors like distance, interference, and obstacles.
Historically, the evolution of the RAN has been driven by the need for higher data rates, lower latency, greater capacity, and more efficient spectrum use. Early RANs (1G, 2G) were designed primarily for circuit-switched voice. The 3G RAN introduced packet-switched data capabilities. The shift to a flat architecture in 4G LTE was motivated by the need to reduce latency for IP-based services. The ongoing evolution towards 5G and Open RAN is driven by demands for extreme mobile broadband, massive IoT connectivity, and mission-critical services, requiring unprecedented flexibility, efficiency, and innovation in the radio layer.
The RAN addresses the core technical challenges of wireless communication: managing a shared, interference-prone medium (the radio spectrum), supporting user mobility with seamless handovers, and adapting to highly variable channel conditions. It abstracts these complexities, presenting a stable data pipe to the core network. Continuous innovation in RAN technology, through techniques like MIMO, carrier aggregation, and network slicing, is what enables each new generation of mobile technology to deliver transformative new services and experiences.
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (20 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, new RAN capabilities were introduced to enhance energy efficiency, including coordinated power saving control between RAN resources and other subsystems like network links, and procedures such as switching off superposing carriers or reducing system bandwidth in response to low traffic. The release also introduced specific corrections and configurations for radio link failure actions, Radio Link Monitoring, and security within the RadioBearerConfig. Furthermore, it established mechanisms for automated power adaptation and defined a Network Power Saving Configuration to translate high-level energy efficiency policies into specific RAN control operations.
- Addition of RAN specific Access Category TS 38.331CR0188
- Corrections on number of RadioLinkMonitoringRS condifuration TS 38.331CR0587
- Corrections on radio link failure related actions TS 38.331CR0902
- Correction to configuration of security in RadioBearerConfig TS 38.331CR1083
- Security Algorithms for Radio Bearers TS 38.331CR1332
In Release 16, the RAN introduced new, coordinated energy-saving capabilities to improve system-wide efficiency. Key additions included mechanisms for automated power adaptation, such as switching off superposing carriers or MIMO layers during low traffic, and the synchronization of power-saving controls between the RAN and other subsystems like network links. The release also formalized energy efficiency evaluation for different deployment environments and extended SON functions to manage these new power-saving operations based on operator-defined policies.
- TR approved by TSG RAN plenary TS 38.821
In Release 17, the RAN introduced enhanced support for RAN slicing through RRC protocol updates and corrections, providing more defined network slice management. Furthermore, the release expanded energy-saving capabilities by enabling coordinated power saving control between RAN resources and other subsystems like network links, aiming to maximize system-wide energy efficiency. These enhancements included mechanisms for automated, traffic-dependent actions such as switching off superposing carriers or reducing system bandwidth.
In Release 18, the RAN introduced new capabilities for coordinated energy saving, including the synchronization of power saving control between RAN resources and other subsystems like network links connecting base stations. This enables automated, coordinated switching processes for actions such as switching off superposing radio carriers or reducing system bandwidth in response to low traffic. Furthermore, enhancements were made to handle radio and RLC bearers during cell switch execution in NR-DC and to provide RAN feedback for adjusting burst sending time and periodicity.
- RAN feedback for burst sending time adjustment TS 23.503CR0755
- RAN feedback for burst sending time and periodicity adjustment TS 23.503CR0853
- Handling of radio and RLC bearers at LTM cell switch execution in NR-DC TS 38.331CR5383
- TR under change control further to the approval for inclusion in Rel-18 by RAN TS 38.859
In Release 19, the RAN introduced enhancements for coordinated energy saving, enabling automated power adaptation and the switching off of superposing carriers or MIMO layers based on traffic thresholds. It also added support for uplink rate control for QoS flows at the RAN and for providing the MMSID from the 5G Core to the NG-RAN via the NGAP interface. Furthermore, the release included corrections to ensure the proper release of RAN-visible QoE configurations.
- Support of enabling correct header compression to be performed by NG-RAN TS 23.503CR1423
- Support of providing MMSID from 5GC to NG-RAN through NGAP TS 23.503CR1457
- 23.503 Support of uplink rate control for QoS flows at RAN TS 23.503CR1531
- R19 CR 28.662 Correct references to align with RAN specifications TS 28.662CR0023
- Correction on the release of RAN visible QoE configuration TS 38.331CR5646
Explore further
Broader topics and technologies where RAN plays a role.
Defining Specifications
3GPP specifications that define or reference RAN, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TR 21.866 vf00 | Study on Energy Efficiency in 3GPP Standards | Rel-15 |
| TR 21.905 vj00 | 3GPP Technical Terms and Definitions | Rel-19 |
| TS 22.468 vj00 | Group Communication System Enabler Requirements | Rel-19 |
| TS 22.811 v1700 | Network Selection Mechanisms Overview | Rel-7 |
| TS 22.822 vg00 | Satellite Access in 5G Study | Rel-16 |
| TR 22.944 vj00 | UE Functionality Split Scenarios and Requirements | Rel-19 |
| TS 23.050 v1100 | UMTS Network Principles and Architecture | R99 |
| TS 23.107 vj00 | UMTS QoS Framework | Rel-19 |
| TS 23.110 vj00 | Access Stratum Services Specification | Rel-19 |
| TS 23.171 v1300 | LCS Stage 2 Specification for UMTS | Rel-4 |
| TS 23.179 vd50 | MCPTT Functional Architecture | Rel-13 |
| TS 23.203 vj20 | Policy and charging control architecture | Rel-19 |
| TS 23.207 vj00 | End-to-End QoS Framework for GPRS | Rel-19 |
| TS 23.221 vj00 | 3GPP System Architectural Requirements | Rel-19 |
| TS 23.236 vj00 | Intra Domain Connection of RAN Nodes to Multiple CN Nodes | Rel-19 |
| TS 23.271 vj00 | LCS Stage 2 Specification | Rel-19 |
| TS 23.280 vk10 | Common Architecture for Mission Critical Services | Rel-20 |
| TS 23.379 vk00 | MCPTT Functional Architecture | Rel-20 |
| TS 23.503 vk00 | 5G Policy and Charging Control Framework | Rel-20 |
| TS 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TR 23.780 ve00 | MBMS for Mission Critical Communication Services | Rel-14 |
| TS 23.795 vg10 | V2X Application Architecture Study | Rel-16 |
| TS 23.851 v1600 | Network Sharing Architecture for 3G Systems | Rel-6 |
| TR 23.923 v1300 | Mobile IP+ Feasibility Study for UMTS/GPRS | Rel-4 |
| TR 23.976 vj00 | Push Service Requirements Analysis | Rel-19 |
| TS 24.312 vj00 | ANDSF Management Objects Specification | Rel-19 |
| TS 25.305 vj00 | UTRAN UE Positioning Stage 2 | Rel-19 |
| TS 25.402 vj00 | UTRAN Synchronisation Mechanisms | Rel-19 |
| TS 25.423 vj00 | UTRAN RNSAP Specification | Rel-19 |
| TR 25.914 vj00 | 3G UE Radio Performance Test Methods | Rel-19 |
| TS 26.093 vj00 | SCR operation of AMR codec for UMTS | Rel-19 |
| TS 26.102 vj00 | Mapping of AMR and other codecs to interfaces | Rel-19 |
| TS 26.193 vj00 | AMR-WB Source Controlled Rate (SCR) Operation | Rel-19 |
| TS 26.202 vj00 | AMR-WB Speech Codec Mapping Specification | Rel-19 |
| TS 26.501 vj30 | 5G Media Streaming (5GMS) Architecture | Rel-19 |
| TS 26.804 vj10 | 5G Media Streaming Extensions Study | Rel-19 |
| TR 26.806 vi00 | Technical Report on Smartly Tethering AR Glasses | Rel-18 |
| TS 26.849 vc10 | MBMS Operation on Demand (MooD) | Rel-12 |
| TR 26.916 ve20 | eSRVCC Transcoding Minimization Study | Rel-14 |
| TR 26.926 vj00 | Traffic Models & Quality Evaluation for Media/XR in 5G | Rel-19 |
| TR 26.937 vj00 | 3GPP PSS Characterization | Rel-19 |
| TR 26.942 vj00 | Study on Media Energy Consumption Exposure & Evaluation | Rel-19 |
| TR 26.998 vj00 | 5G AR/MR Glasses Integration Study | Rel-19 |
| TS 28.062 vj00 | Tandem Free Operation (TFO) Service Description | Rel-19 |
| TS 28.661 vj00 | Generic RAN NRM IRP Requirements | Rel-19 |
| TS 28.662 vj10 | Generic RAN Network Resource Model (NRM) IRP IS | Rel-19 |
| TS 28.663 vj00 | Generic RAN NRM IRP Solution Set Definitions | 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 29.060 vj00 | GPRS Tunnelling Protocol (GTP) version 1 | Rel-19 |
| TR 29.835 vh10 | Study on Port Allocation for 3GPP Interfaces | Rel-17 |
| 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 32.277 vj20 | Charging Management for Proximity Services (ProSe) | Rel-19 |
| TS 32.278 vj00 | Monitoring Events Offline Charging Specification | Rel-19 |
| TS 32.293 vj00 | Proxy Function in Domestic Service Provider | Rel-19 |
| TS 32.791 vb00 | Common RAT NRM IRP Requirements | Rel-11 |
| TS 32.792 vb10 | Generic RAN Network Resource Model (NRM) IRP | Rel-11 |
| TS 32.796 vc00 | Generic RAN NRM IRP Solution Set Definitions | Rel-12 |
| TS 32.808 v1800 | Common User Profile Storage Framework | Rel-8 |
| TS 32.826 va00 | Study on Energy Savings Management in LTE/SAE Networks | Rel-10 |
| TS 33.821 v900 | LTE/SAE Security Threat Analysis and Countermeasures | Rel-9 |
| TS 33.836 vg10 | Security Study for Advanced V2X Services | Rel-16 |
| TR 33.847 vh10 | 5G Proximity Services Security Study | Rel-17 |
| TS 33.859 vb10 | UTRAN Key Hierarchy Enhancement Study | Rel-11 |
| TS 34.114 vc20 | Radiated Performance Test Procedure for UE/MS | Rel-12 |
| TS 36.102 vj10 | E-UTRA UE Satellite Access RF Requirements | Rel-19 |
| TS 36.521 vj00 | E-UTRA UE Conformance ICS Proforma | Rel-19 |
| TS 36.750 ve10 | Study on enhancement of VoLTE | Rel-14 |
| TR 36.763 vh00 | NB-IoT/eMTC Support for Non-Terrestrial Networks | Rel-17 |
| TS 36.855 vd00 | E-UTRA Positioning Enhancements Study | Rel-13 |
| TS 36.887 vc00 | Energy Saving Enhancement for E-UTRAN Study | Rel-12 |
| TS 36.894 vd00 | Study on LTE Measurement Gap Enhancement | Rel-13 |
| TR 36.927 vj00 | Network Energy Saving for E-UTRAN | Rel-19 |
| TS 37.544 vg70 | UE Radiated Performance Test Procedures | Rel-16 |
| TR 37.902 vj00 | OTA TRP/TRS Measurement for LTE Terminals | Rel-19 |
| TS 38.101 vj31 | NR User Equipment Radio Transmissions | Rel-19 |
| TS 38.331 vj00 | NR Radio Resource Control (RRC) Protocol Specification | Rel-19 |
| TS 38.521 vj20 | NR Physical Layer UE Conformance Testing | Rel-19 |
| TS 38.741 vj00 | NTN L-/S-band for NR Technical Specification | Rel-19 |
| TS 38.811 vf40 | Study on NR Support for Non-Terrestrial Networks | Rel-15 |
| TS 38.821 vg20 | NR Support for Non-Terrestrial Networks | Rel-16 |
| TR 38.859 vi10 | Technical Report | Rel-18 |
| TS 38.863 vj10 | NR NTN RF and Co-existence Spec | Rel-19 |
| TR 38.913 vj00 | Next Gen Access Tech Scenarios & Requirements | Rel-19 |
| TS 43.129 vj00 | PS Handover in GERAN A/Gb and GAN Modes | Rel-19 |
| TS 43.130 vj00 | Iur-g Interface Overview | Rel-19 |
| TR 43.901 vj00 | Generic Access to A/Gb Interface Feasibility Study | Rel-19 |
| TR 44.901 vj00 | Extended NACC for External Cell Change | Rel-19 |
| TR 45.902 vj00 | Flexible Layer One (FLO) for GERAN | Rel-19 |
| TS 48.018 vj00 | BSS-SGSN Interface for GPRS Control | Rel-19 |