Description
The Remote Interference Management Reference Signal (RIM-RS) is a physical layer signal defined in the 5G New Radio (NR) standard, specified in 3GPP TS 38.211. It is a dedicated downlink reference signal whose sole purpose is to facilitate the detection and measurement of remote interference in Time Division Duplex (TDD) networks. When a gNB (5G base station) transmits its normal downlink signals, a distant victim gNB receiving unintended interference needs a way to identify and characterize that interference. The RIM-RS provides this capability. It is designed with specific sequences and is mapped to predetermined resource elements within the downlink frame structure, making it recognizable even in the presence of other signals and noise.
The operational procedure involves the interfering gNB periodically transmitting the RIM-RS in its downlink. This transmission typically occurs in specific symbols, often within or adjacent to the guard period or special frame configurations. The victim gNB, while configured to receive in its uplink slot, instead scans for the presence of these known RIM-RS sequences arriving from distant sources. Upon detection, the victim gNB performs precise measurements on the received RIM-RS. Key measurements include the received signal power, which indicates the interference strength, and crucially, the time of arrival. By comparing the arrival time of the detected RIM-RS with its own internal frame timing, the victim gNB can estimate the propagation delay of the interfering signal.
This measured delay is a critical parameter. It directly informs how much the interfering gNB would need to adjust its transmission timing to prevent its downlink from overlapping with the victim's uplink. The measurement results, including a source identifier potentially derived from the RIM-RS sequence, are packaged into a RIM report. This report is then sent to the interfering gNB via the Xn application protocol (XnAP), as specified in TS 38.473. Upon receiving the report, the interfering gNB can initiate mitigation actions, such as shifting its transmission window. Thus, the RIM-RS acts as the fundamental enabling signal that transforms the RIM process from a theoretical concept into a practical, measurable, and actionable system, allowing base stations to 'see' and quantify interference from over the horizon.
Purpose & Motivation
The RIM-RS was created to provide a standardized, optimized signal specifically for the Remote Interference Management (RIM) use case in 5G NR. Prior to its definition, systems might have attempted to use existing synchronization or cell-specific reference signals for interference detection, but these were not ideal. They were not designed for long-distance, weak-signal detection in another base station's receive band, and they lacked the necessary properties for accurate delay estimation and source identification in the challenging remote interference scenario.
The specific problem RIM-RS solves is the need for reliable detection and accurate measurement of ultra-long-delay interference. The signal is designed with good autocorrelation and cross-correlation properties to ensure it can be detected at very low signal-to-interference-plus-noise ratios (SINR), which is typical for a distant interfering signal arriving at a victim base station's uplink receiver. Its structured placement in the time domain allows for precise timing measurement, which is essential for calculating the required timing adjustment for mitigation.
Introduced in 3GPP Release 16 as part of the enhanced RIM framework for NR, the RIM-RS addressed the limitations of earlier, less formalized approaches. It provided a unified physical layer foundation that all NR equipment vendors could implement, ensuring interoperability and effective performance of the RIM feature across multi-vendor 5G TDD networks. Its creation was motivated by the anticipated large-scale 5G TDD deployments, where managing remote interference is a prerequisite for stable network operation, especially with features like coordinated scheduling and network synchronization that are central to 5G performance.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (101 CRs across 6 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the RIM-RS function was introduced as part of the Network Resource Model (NRM) for management and orchestration, specified within the TS 28.541 document family. The introduction involved defining its information model semantics and behaviour for management interfaces, alongside a corresponding solution set with specific protocols. This allowed for the integrated management of this RAN feature within the 5G network management framework.
- Adding missing attribute, and correction of reference TS 28.541CR0023
- Replace symbol for network slice state management TS 28.541CR0027
- Align the management of external function and cell with TS 28.658 TS 28.541CR0033
- Correction of references TS 28.541CR0048
- Correction on reference name of UE capability of additional DMRS for co-existence with LTE CRS TS 38.211CR0011
- Correction of secured signalling connection TS 38.413CR0161
+ 2 more changes
In Release 16, the new RIM-RS (Remote Interference Management Reference Signal) function was introduced to manage remote interference between base stations. This introduction included the addition of specific RIM monitoring parameters and RIM parameters for remote interference management within the management framework. Furthermore, the signalling design for RIM was specified in TS 38.413 to support this new capability.
- Add the RIM monitoring parameters for remote interference management TS 28.541CR0202
- Management of NR ANR, Stage 2 TS 28.541CR0222
- Management of NR ANR, Stage 3 TS 28.541CR0223
- Add the RIM parameters for remote interference management TS 28.541CR0245
- ANR management for EN-DC architecture TS 28.541CR0268
- Stage3 add the NRM fragment for SON management TS 28.541CR0289
+ 17 more changes
In Release 17, the RIM-RS function was enhanced with specific corrections and provisioning updates. These included corrections to RRC references for procedures like SL relay and DRX, mapping of SRB1 for the remote UE, and enabling the retrieval of data forwarding progress information by provisioning MBS Multicast F1-U references to the UE context in the gNB-CU. Additionally, corrections were made to management areas such as MBS session management and network slice state management.
- Add NRM IOC definitions for N5, N70 and N71 reference points TS 28.541CR0526
- Add subclause reference of MRO related attribute TS 28.541CR0407
- Update 5GC NRM for 5G_DDNMF reference point TS 28.541CR0613
- Correct NRM fragment for DMRO Management TS 28.541CR0649
- Correct YANG Network Slice NRM solution set reference TS 28.541CR0672
- Address the unnecessary reference for the yaml file TS 28.541CR0723
+ 21 more changes
In Release 18, the enhancements for RIM-RS primarily involved updates to the Network Resource Model (NRM) for management and orchestration, specifically adding NRM Information Model definitions to support Non-Terrestrial Network (NTN) management. These updates included stage 2 and stage 3 YAML definitions within TS 28.541 to formalize the management data structures for NTN scenarios.
- Update NWDAFFunction IOC to support management and control purpose TS 28.541CR0765
- Update NWDAFFunction IOC to support management and control purpose TS 28.541CR0823
- Rel-18 CR TS 28.541 Add NRM Info Model definitions for NTN management(stage2) TS 28.541CR1007
- Rel-18 CR TS 28.541 Add NRM Info Model definitions for NTN management(Stage3 Yaml) TS 28.541CR1008
- Correction of inheritance relationships figure name for NTN management support TS 28.541CR1170
- TS28.541 Rel18 correction to Forge reference TS 28.541CR1206
+ 12 more changes
In Release 19, the RIM-RS (Remote Interference Management Reference Signal) function was enhanced with a correction to the PRACH signal generation for LTM (Long-Term Management), as specified in TS 38.211. This update ensures the proper generation of reference signals used for managing remote interference across the radio access network. The change is part of the broader management corrections and enhancements introduced in this release.
- Rel-19 CR TS 28.541 Enhance NR NRM to support management of RedCap feature TS 28.541CR1460
- Rel-19 CR TS 28.541 Enhance NR NRM to support management of RedCap BWP feature TS 28.541CR1469
- Rel-19 CR TS 28.541 Add AIOTF and ADM IOC to support management of Ambient IoT TS 28.541CR1510
- NRM changes to support IAB-node management TS 28.541CR1598
- Introduction of low-power wake-up signal TS 38.211CR0152
- Introduction of low-power wake-up signal and receiver for NR TS 38.413CR1261
+ 10 more changes
In Release 20, the RIM-RS (Remote Interference Management Reference Signal) function introduced new management support capabilities within the Network Resource Model (NRM). These enhancements included stage 3 management support for XRM services and updates to align ATSSS management capabilities with SA2 definitions. The release also provided management support for dynamic traffic characteristics updates and for delivering media-related information for encrypted traffic using the on-path N6 signaling method.
- Rel-20 CR TS 28.541 Management Support for Dynamic Traffic Characteristics Update TS 28.541CR1647
- Rel-20 CR TS 28.541 Management Support to Deliver Media Related Information for Encrypted Traffic Using On-path N6 Signaling Method TS 28.541CR1650
- Rel-20 CR TS 28.541 Stage 3 of Management Support for XRM TS 28.541CR1651
- Rel-20 CR TS 28.541 Management Support for Dynamic Traffic Characteristics Update TS 28.541CR1667
- Rel-20 CR TS 28.541 Management Support for Policy Control Enhancements to Support Multi-modality Flows TS 28.541CR1668
- Rel-20 CR TS 28.541 Management Support for UE Power Saving for XRM Services TS 28.541CR1669
+ 3 more changes
Explore further
Broader topics and technologies where RIM-RS plays a role.
Defining Specifications
3GPP specifications that define or reference RIM-RS, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 28.541 vk00 | 5G Network Resource Model (NRM) Stage 2/3 | Rel-20 |
| TS 38.211 vj10 | NR Physical Channels and Modulation | Rel-19 |
| TS 38.401 vj10 | NG-RAN Architecture Specification | Rel-19 |
| TS 38.413 vj10 | NG Application Protocol (NGAP) | Rel-19 |
| TS 38.473 vj10 | 5G F1 Application Protocol (F1AP) | Rel-19 |