Description
The RAN-based Notification Area (RNA) is a core mobility management concept for the RRC_INACTIVE state introduced in LTE (eNB-based) and evolved in NR (gNB-based). It defines a geographical area, configured by the RAN, within which a User Equipment (UE) can move freely without notifying the network of its cell-level location. The RNA is composed of one or more cells, which can be configured as a list of cells, a list of RAN areas (each being a group of cells), or a tracking area. When a UE transitions to RRC_INACTIVE, the last serving base station (the last serving gNB in NR or eNB in LTE) assigns it an RNA, typically based on UE mobility patterns, subscription, or network policy.
The primary operational mechanism involves the UE performing periodic or triggered RNA Updates. While in RRC_INACTIVE, the UE monitors system information to identify the RNA Identity of its current cell. If the UE moves to a cell whose RNA ID is not part of its assigned RNA, it must initiate an RNA Update procedure to inform the RAN of its new location and potentially get a new RNA assigned. This procedure is a lightweight RRC connection resume, reactivating the UE context stored in the RAN and the core network. Conversely, if the UE remains within its RNA, it can stay in this low-power state indefinitely. When downlink data arrives for the UE, the RAN initiates a paging procedure within all cells of the UE's last known RNA to locate and resume the connection.
The architecture relies on the RAN's ability to store the Access Stratum (AS) context of the UE and manage the RNA area. In NR, this is facilitated by the NG-RAN architecture where gNBs are interconnected via the Xn interface. The last serving gNB acts as the “Anchor” gNB, retaining the UE context. Other gNBs within the RNA can assist in paging. RNA configuration is signaled to the UE via RRCRelease messages and broadcast in system information blocks (SIBs). This mechanism decouples mobility management for inactive UEs from the core network's Tracking Area (TA), reducing signaling load on the N2/N3 interfaces and enabling faster state transitions compared to the traditional IDLE state procedures.
Purpose & Motivation
RNA was created to address the signaling overhead and power consumption challenges associated with the massive number of IoT and smartphone devices that transmit data infrequently but require always-on connectivity. Traditional LTE mobility relied on two main states: RRC_IDLE and RRC_CONNECTED. IDLE state required core network (MME) involvement for location updates (Tracking Area Updates) and paging, causing latency and signaling load. CONNECTED state kept radio resources active, wasting power for bursty traffic. The RRC_INACTIVE state, for which RNA is a key enabler, was introduced to provide a middle ground.
The motivation stemmed from 5G use cases like massive Machine-Type Communication (mMTC) and enhanced Mobile Broadband (eMBB) with bursty traffic patterns. RNA solves the problem by keeping the UE's context in the RAN, allowing mobility within an area without core network signaling. This drastically reduces the signaling storm that would occur if every small cell change required a Tracking Area Update. It also enables faster connection resume (compared to IDLE to CONNECTED transition) and better battery life than staying in CONNECTED. RNA represents a shift of mobility management responsibility from the core to the RAN, optimizing for scenarios where session continuity with low latency and low signaling is paramount.
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (117 CRs across 6 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-10, normative work from Rel-15.
In Release 15, the RNA (RAN-based Notification Area) function was introduced to manage the mobility of UEs in RRC_Inactive state, enabling efficient notification without full connection establishment. The release included clarifications on RNA update procedures and the core network registration process, as detailed in the CR for clarification N023. This established the foundational mechanism for a UE to transition to RRC_Connected mode under a different NG-RAN node within the same RNA while the original node retains the UE context.
- Introduction of DEFLATE based UDC Solution TS 36.300CR1090
- Enabling MBMS Bearer Event Notification TS 36.300CR1138
- Implementing network-based CRS interference mitigation TS 36.304CR0729
- Introduction of DEFLATE based UDC Solution TS 36.331CR3211
- Implementing network-based CRS interference mitigation TS 36.331CR3408
- Stage 2 Changes based on CN type indication for Redirection from ng-eNB to E-UTRA TS 36.300CR1185
+ 13 more changes
In Release 16, the RNA function was enhanced with clarifications on the initiation of an RNA update procedure and a correction on the usage of access category 2 for Unified Access Control (UAC) during such an update. These refinements provided more precise rules for when a UE in RRC_INACTIVE state must perform the RNA update, particularly when moving to a different gNB within the same RNA. Additionally, the specification clarified the notification mechanisms for system information changes relevant to UEs in RRC_INACTIVE.
- Solution 8 Updates for QoS monitoring solution based on time synchronization TS 23.725CR0004
- Accurate time stamping based solution for Key issue #6 TS 23.725CR0007
- KI#7: Extending notification control for QoS flow setup and handover TS 23.725CR0011
- Introduction of LTE-based 5G terrestrial broadcast TS 36.331CR4190
- Release-16 UE capabilities based on RAN1, RAN4 feature lists and RAN2 TS 38.331CR1665
- Implementing confirmation of code block group based transmission TS 38.331CR1717
+ 22 more changes
In Release 17, the enhancements for the RAN-based Notification Area (RNA) function specifically addressed scenarios where a UE transitions from RRC_Inactive to RRC_Connected under a different NG-RAN node within the same RNA. This refinement focused on improving the handling of UE context during such mobility events to support efficient notification and connection resumption.
- Add measurements related to data modification notification subscription for UDR TS 28.552CR0302
- Add location determination and notification related measurements for LMF TS 28.552CR0354
- Adding new packets based performance measurements TS 28.552CR0360
- Updating packets based performance measurements TS 28.552CR0361
- Introduction of new bands and bandwidth allocation for LTE-based 5G terrestrial broadcast TS 36.300CR1360
- Introduction of event-based trigger for LTE MDT logging [LTE-Event-MDT] TS 36.304CR0834
+ 31 more changes
In Release 18, specific corrections and clarifications were made to the RNA function, primarily focusing on location-based and timer-based procedures for conditional handover in IoT NTN and NR NTN scenarios. These included corrections to location-based measurements and timer-based conditional handover triggers to improve reliability. Furthermore, enhancements were introduced for event-based conditional handover support, such as adding UE capability for event A4-based CHO for ATG.
- Addition of Distribution of Scheduled PUSCH/PDSCH PRBs based on MIMO Layers Coverage Map measurement TS 28.552CR0411
- Add performance measurement related with number of notifications for NWDAF data collection TS 28.552CR0431
- Introduction of MAC CE based PL RS updates for Type-1 CG-PUSCH [PL RS Type 1 CG] TS 38.331CR4513
- Correction of timer-based conditional handover for IoT NTN TS 36.300CR1399
- Corrections to location-based measurement TS 36.300CR1417
- Corrections on distance-based measurements during T-Service for IoT NTN TS 36.304CR0876
+ 14 more changes
In Release 19, the RNA function was enhanced with a clarification on Notification Configuration, as indicated in the CR titles. The specification text details a key scenario for study, specifically when a UE transitions from RRC_Inactive to RRC_Connected under a different NG RAN node than the one storing its context, but within the same RAN Notification Area. This clarification helps address challenges related to QoS and resource management during such state transitions.
- Introduction of LTE-based 5G Broadcast Phase 2 TS 36.300CR1428
- Introduction of CAS muting in LTE-based 5G broadcast [5GB_CASMuting] TS 36.331CR5139
- Introduction of LTE-based 5G Broadcast Phase 2 TS 36.331CR5143
- Rapporteur correction on CAS muting for LTE based 5G broadcast [5GB_CASMuting] TS 36.331CR5162
- Corrections to LTE-based 5G Broadcast Phase 2 after ASN.1 review TS 36.331CR5168
- Clarification on Notification Configuration TS 36.331CR5186
+ 6 more changes
In Release 20, the RNA function was enhanced to support scenarios where a UE transitions from RRC_Inactive to RRC_Connected Mode under a different NG RAN node within the same RNA, which is a key study area for maintaining connectivity. The release also introduced mechanisms for redundant user plane paths based on dual connectivity, where the SMF uses a Redundancy Sequence Number (RSN) from the UE to identify and manage redundant PDU Sessions. Furthermore, the RAN is impacted to attempt to establish and maintain dual connectivity when redundant handling is indicated for a pair of PDU Sessions.
- Rel-20 CR 28.552 Add a new measurement related to the number of roaming data collection service notifications generated by RE-NWDAF TS 28.552CR0718
Explore further
Broader topics and technologies where RNA plays a role.
Defining Specifications
3GPP specifications that define or reference RNA, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.725 vg20 | Study on URLLC Architecture Enhancements | Rel-16 |
| TS 25.471 vj00 | RNSAP User Adaptation (RNA) for Iurh | Rel-19 |
| TS 28.552 vk10 | 5G Performance Management Measurements | Rel-20 |
| TS 36.300 vj00 | E-UTRAN Radio Interface Protocol Architecture Overview | Rel-19 |
| TS 36.304 vj00 | UE Idle Mode Procedures in E-UTRA | Rel-19 |
| TS 36.331 vj00 | LTE RRC Protocol Specification | 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 38.331 vj00 | NR Radio Resource Control (RRC) Protocol Specification | Rel-19 |