Description
CSI-RSRQ (CSI Reference Signal Received Quality) is a critical physical layer measurement defined in the 5G New Radio (NR) standards. It quantifies the quality of the received Channel State Information Reference Signal (CSI-RS) by evaluating the ratio of the desired CSI-RS power to the total interference and noise power within the measurement bandwidth. Unlike RSRP (Reference Signal Received Power), which measures signal strength, CSI-RSRQ provides a signal-to-interference-plus-noise ratio (SINR)-like metric specific to the CSI-RS resource, offering a more comprehensive view of the radio link quality in the presence of co-channel interference and noise.
Architecturally, CSI-RSRQ measurement is performed by the User Equipment (UE) in the downlink. The gNodeB configures the UE with specific CSI-RS resources for measurement via RRC signaling. The UE measures the received power of these configured CSI-RS resources, denoted as RSRP_CSI-RS. Simultaneously, the UE measures the total received power (including interference from other cells, noise, and any other signals) within the same frequency bandwidth as the CSI-RS resource. The CSI-RSRQ is then calculated as (N * RSRP_CSI-RS) / (E-UTRA carrier RSSI), where N is the number of resource blocks (RBs) over which the RSSI (Received Signal Strength Indicator) is measured, and the RSSI encompasses the total wideband power. This calculation yields a linear ratio, often reported in dB.
The role of CSI-RSRQ in the network is multifaceted. It is a primary input for Channel State Information (CSI) reporting, which the UE provides to the gNodeB. This reporting is essential for advanced radio resource management functions. Based on CSI-RSRQ, the gNodeB can perform accurate link adaptation, selecting the optimal modulation and coding scheme (MCS) to maximize throughput while maintaining block error rate targets. It is also vital for beam management procedures, helping to identify the best transmit/receive beam pairs by assessing the quality of different CSI-RS beams. Furthermore, CSI-RSRQ measurements support mobility management, including handover decisions and cell reselection, by providing a quality-centric metric alongside RSRP.
Key components involved in CSI-RSRQ operation include the configured CSI-RS resources (with specific time/frequency locations, periodicity, and scrambling), the UE's physical layer measurement circuitry, and the higher-layer filtering and reporting mechanisms defined in 3GPP specifications. The measurement is designed to be flexible, supporting various use cases such as connected-mode mobility, beam failure detection, and radio link monitoring. Its accuracy is critical for the performance of 5G NR, especially in dense deployments and high-frequency bands where interference dynamics are more pronounced.
Purpose & Motivation
CSI-RSRQ was introduced in 5G NR to address the need for a robust, interference-aware channel quality metric specifically tailored for advanced reference signals like CSI-RS. In LTE, RSRQ served a similar purpose for Cell-specific Reference Signals (CRS), but 5G's decoupled architecture, with CSI-RS used for beamformed data transmission and tracking, required a dedicated quality measurement. The primary problem it solves is enabling accurate channel state estimation in interference-limited scenarios, which is essential for the high spectral efficiency targets of 5G.
Historically, relying solely on RSRP (a power-based metric) for link adaptation and mobility could lead to suboptimal decisions in the presence of strong inter-cell interference. A high RSRP value does not guarantee good throughput if the interference level is also high. CSI-RSRQ provides a direct measure of signal quality relative to interference and noise, filling this gap. Its creation was motivated by the evolution towards more complex multi-beam operations and network densification in 5G, where interference management becomes paramount.
The technology addresses limitations of previous approaches by being tightly coupled with the CSI framework. Unlike the LTE RSRQ defined for CRS, CSI-RSRQ is measured on configurable CSI-RS resources, which can be beam-specific and user-specific. This allows for precise quality assessment of the actual beams used for data transmission, rather than a cell-wide average. It enables gNodeBs to make finer-grained scheduling and beam management decisions, directly improving user experience and network capacity in challenging radio conditions.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (47 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the CSI-RSRQ function was not newly introduced; the provided grounding context and Change Request titles only describe corrections and clarifications to existing CSI-RS procedures. These corrections specifically addressed aperiodic CSI-RS triggering when there was different numerology between the PDCCH and the CSI-RS, and clarifications to the CSI-RS configuration as specified in 38.214. Therefore, Release 15 work focused on refining the existing framework for CSI-RS, including its configuration and triggering mechanisms, rather than defining a new CSI-RSRQ measurement.
In Release 16, key enhancements for CSI-RSRQ-related procedures included corrections to aperiodic CSI-RS triggering with specific beam switching timing values of 224 and 336, and clarifications on cross-carrier scheduling for CSI-RS triggering. The release also introduced corrections for the default TCI state of aperiodic CSI-RS in multi-TRP scenarios and provided fixes for measurement restrictions and enabling configurations specifically for L1-RSRP and CSI measurements.
- Aperiodic CSI-RS Triggering for UE reporting beamSwitchTiming values of 224 and 336 TS 38.214CR0060
- Corrections of cross-slot scheduling restriction and CSI/L1-RSRP measurement outside active time TS 38.214CR0074
- Correction on SRS-RSRP reception procedure for CLI TS 38.214CR0094
- Correction on aperiodic CSI-RS triggering with beam switching timing of 224 and 336 and on CSI reporting TS 38.214CR0107
- Correction on aperiodic CSI-RS triggering with beam switching timing of 224 and 336 TS 38.214CR0121
- Corrections for default TCI state of AP CSI-RS in multi-TRP TS 38.214CR0131
+ 13 more changes
In Release 17, specific corrections were introduced for CSI-RS to enhance multi-TRP (mTRP) operations and timing accuracy. These included corrections on CSI-RS port restriction for mTRP CSI and on slot offsets for CSI-RS resource pairs in MTRP scenarios. Additionally, the release provided corrections for aperiodic CSI-RS timing under mixed numerologies and for frequency resources when CSI-RS is used for tracking.
- CR for CSI-RS power for inter-cell mTRP TS 38.214CR0313
- CR on default QCL for unified TCI state for PDSCH and A-CSI-RS TS 38.214CR0314
- Correction on CSI-RS port restriction for mTRP CSI TS 38.214CR0319
- Correction on slot offsets of CSI-RS resource pairs for MTRP TS 38.214CR0320
- Correction on aperiodic CSI-RS for tracking for fast SCell activation TS 38.214CR0321
- Correction on frequency resource for CSI-RS for tracking in TS 38.214 TS 38.214CR0351
+ 6 more changes
In Release 18, specific corrections and clarifications were introduced for the CSI-RSRQ function. These included a correction on the threshold for A-CSI-RS reception aligned with the Rel-18 TCI framework and a clarification of the CSI-RS transmission occasion for NCJT CSI. Additionally, procedures were adjusted to address CSI report dropping due to the absence of CSI-RS.
- Correction of physical channels and signals during cell DTX/DRX operation TS 38.214CR0566
- Correction on CSI processing criteria for new NES capability signaling TS 38.214CR0584
- Correction on threshold for A-CSI-RS reception for Rel-18 TCI framework TS 38.214CR0613
- Correction to reference point for NG-RAN measurement for UL SRS-RSRP and UL SRS-RSRPP TS 38.215CR0070
- CR on clarification of CSI-RS transmission occasion for NCJT CSI TS 38.214CR0475
- ssb-index-RSRP/SINR CSI report dropping due to absence of CSI-RS TS 38.214CR0521
+ 1 more changes
In Release 19, the enhancements for CSI-RSRQ primarily involved corrections and clarifications to the counting and configuration rules for CSI-RS resources used in measurements. Specifically, changes were made to the counting of CSI-RS resources referred to by multiple CSI reporting settings and to the simultaneous counting of NZP-CSI-RS resources with NES. Additionally, the release included a correction on the association between NZP CSI-RS and CSI-IM resources.
- TEI19 Counting of CSI-RS resource referred by N CSI reporting settings [SimCSI_count] TS 38.214CR0681
- TEI19 Simultaneous NZP-CSI-RS resource counting with NES [SimCSI_countNES] TS 38.214CR0689
- Correction on Semi-persistent CSI/Semi-persistent CSI-RS for LTM TS 38.214CR0733
- Correction on association between NZP CSI-RS and CSI-IM TS 38.214CR0744
- Clarification on the number of simultaneous L1 CLI-RSSI and simultaneous L1 SRS-RSRP measurement resources TS 38.214CR0745
- Correction on the maximum number of SRS-RSRP measurement resource sets and CLI-RSSI measurement resource sets TS 38.214CR0746
Explore further
Broader topics and technologies where CSI-RSRQ plays a role.
Defining Specifications
3GPP specifications that define or reference CSI-RSRQ, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 38.214 vj10 | NR Physical Layer Procedures for Data | Rel-19 |
| TS 38.215 vj10 | NR Physical Layer Measurements | Rel-19 |