Description
Interference Measurement Resource (IMR) is a physical layer concept in LTE-Advanced and NR where specific resource elements (REs) within the time-frequency grid are configured by the network for the User Equipment (UE) to perform interference measurement. These resources are typically configured via higher layer signaling (RRC) as part of a CSI (Channel State Information) measurement set. An IMR consists of zero-power or non-zero-power Channel State Information Reference Signals (CSI-RS) resources on which the UE assumes no desired signal from its serving cell is transmitted, allowing it to measure the interference plus noise power from neighboring cells or other sources. The UE measures the received power on these configured REs, and this measurement is used to calculate metrics like the Signal to Interference plus Noise Ratio (SINR) or to derive CSI reports, including Channel Quality Indicator (CQI), Precoding Matrix Indicator (PMI), and Rank Indicator (RI). In Coordinated Multi-Point (CoMP) scenarios, multiple IMR configurations can be provided to measure interference from different hypothesized transmission points or interference hypotheses. The gNB (in NR) or eNB (in LTE) uses these interference reports to make intelligent scheduling decisions, select appropriate modulation and coding schemes (MCS), and apply advanced multi-antenna techniques like beamforming and interference coordination. The configuration includes parameters like resource mapping, periodicity, subframe offset, and scrambling identity. IMR is a key enabler for dynamic and accurate interference awareness in dense and heterogeneous networks.
Purpose & Motivation
IMR was introduced to address the growing challenge of inter-cell interference in LTE-Advanced and 5G NR networks, which became more severe with features like heterogeneous network (HetNet) deployments, cell densification, and the use of shared spectrum. Traditional wideband interference measurements were insufficient for advanced multi-antenna and coordination techniques that require precise, resource-specific interference knowledge. IMR provides a standardized, configurable mechanism for the network to instruct UEs where and how to measure interference, solving the problem of how to obtain accurate interference estimates for link adaptation and CoMP. Its creation was motivated by the need to improve spectral efficiency and cell-edge user performance in interference-limited scenarios. By enabling precise interference measurement, IMR allows the network to implement sophisticated interference mitigation strategies, such as dynamic point selection, joint transmission, and interference nulling, which were key goals of LTE-Advanced from Release 11 onwards and are fundamental to 5G's performance targets.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (23 CRs across 4 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-11, normative work from Rel-15.
In Release 15, the IMR (Interference Measurement Resource) function was newly introduced as a PUCI (Protecting Users from unsolicited Communications in IMS) method for protecting the IMS from unsolicited communication. This IMR functionality is hosted by a PUCI Application Server and is executed based on iFC settings in the S-CSCF. Furthermore, its applicability was extended to include procedures for BFD (Beam Failure Detection) and measurement.
- addition of applicability for BFD and measurement TS 38.522CR0021
In Release 17, the IMR function saw enhancements to its applicability for specific measurement procedures, including L1-SINR measurement and NR SA FR2 SSB based Inter-cell L1-RSRP measurement in non-DRX scenarios. The release also added applicability for UE Rx-Tx time difference measurement using TRS in FR2 for propagation delay compensation and addressed Idle Mode CA/DC Measurements test cases. These updates refined the test conditions and operational scope for interference and radio resource measurements without altering the core IMR architecture hosted by the PUCI AS.
- Correction to applicability of FR2 intra-frequency measurement without DRX and BFD TCs TS 38.522CR0149
- Addition of Idle Mode CA/DC Measurements test cases applicability TS 38.522CR0155
- Addition of test applicability for L1-SINR measurement cases TS 38.522CR0148
- Adding applicability UE Rx-Tx time difference measurement for propagation delay compensation using TRS in FR2 TS 38.522CR0272
- Adding applicability statement for NR SA FR2 SSB based Inter-cell L1-RSRP measurement in non-DRX test case TS 38.522CR0306
In Release 18, updates to the IMR (Interference Measurement Resource) function primarily focused on refining test applicability and correcting specifications for various interference measurement scenarios. These enhancements included specific applicability updates for PDSCH interference test cases, corrections for CQI reporting with inter-cell interference, and additions for PDSCH CRS interference mitigation under NR-LTE coexistence. Furthermore, the release introduced applicability for new measurement contexts such as gap-based measurement tests for RedCap devices and inter-cell SSB based L1-RSRP measurements.
- Applicability update for PDSCH interference test cases TS 38.522CR0390
- Correction of test applicability rule for CQI reporting test cases with inter-cell interference TS 38.522CR0408
- Applicability correction to gap-based measurement tests for RedCap TS 38.522CR0439
- Applicability correction to gap-based measurement tests TS 38.522CR0440
- Applicability spec update for inter-cell CRS interference test case TS 38.522CR0442
- Additional applicability for Inter-cell SSB based L1-RSRP measurements TS 38.522CR0415
+ 8 more changes
In Release 19, the updates for the IMR function focused on refining test applicability and measurement procedures. Specifically, corrections and updates were made to the applicability of test cases for measurement gap enhancements and to reselection test cases with a relaxed measurement criterion. These changes ensure the proper execution of the IMR function, which is hosted by a PUCI Application Server and triggered by iFC settings from the HSS.
Explore further
Broader topics and technologies where IMR plays a role.
Defining Specifications
3GPP specifications that define or reference IMR, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 33.838 vb00 | Study on Protection against Unsolicited Communication for IMS | Rel-11 |
| TS 38.522 vj11 | UE Conformance Test Applicability Statement | Rel-19 |
| TR 38.802 ve20 | Study on New Radio Access Technology Physical Layer Aspects | Rel-14 |
| TR 38.912 vj00 | Study on New Radio Access Technology | Rel-19 |