Description
SS-RSRQ (Synchronization Signal Reference Signal Received Quality) is a derived radio resource management measurement in 5G NR that quantifies the quality of the received synchronization signal block. It is defined as the ratio N * SS-RSRP / (NR carrier RSSI), where N is the number of resource blocks (RBs) of the NR carrier Received Signal Strength Indicator (RSSI) measurement bandwidth. The RSSI represents the total wideband received power within the specified measurement bandwidth, including co-channel serving and non-serving cell signals, adjacent channel interference, and thermal noise. Therefore, SS-RSRQ provides a measure of how much the desired SS signal power (SS-RSRP) stands out against the total interference and noise in the channel.
From an architectural perspective, SS-RSRQ calculation occurs within the UE's physical layer and Layer 3 RRM functions. The UE first measures the SS-RSRP for a specific SSB as described in its own entry. Concurrently, or over a configured measurement period, the UE measures the total RSSI over the same carrier bandwidth used for the SS-RSRP measurement. The RSSI measurement involves sampling the total power across the entire configured measurement bandwidth. The ratio is then computed, typically resulting in a negative dB value, as the SS-RSRP (a portion of the total power) is divided by the total RSSI. This computed SS-RSRQ value is filtered to average out short-term fluctuations.
The role of SS-RSRQ in the network is complementary to SS-RSRP. While SS-RSRP indicates absolute signal strength, SS-RSRQ indicates the 'cleanness' or quality of that signal. This is particularly important in dense network deployments, such as urban macro cells or indoor small cells, where interference from neighboring cells can be significant. During cell reselection in idle mode, the UE uses criteria that can incorporate both SS-RSRP and SS-RSRQ (parameters like Qqualmeas and Qqualmin) to select the best cell, not just the strongest one. For connected mode mobility, the network can configure handover events (e.g., A5 event) that trigger based on SS-RSRQ thresholds, allowing handovers from a cell with acceptable signal strength but poor quality (high interference) to a cell with better quality. It is a key input for load balancing and interference coordination algorithms run by the RAN.
Purpose & Motivation
SS-RSRQ was introduced in 3GPP Release 15 alongside SS-RSRP to provide a standardized measure of signal quality in 5G NR. In LTE, RSRQ served a similar purpose, calculated as N * RSRP / (E-UTRA carrier RSSI). The motivation for defining an SS-based RSRQ in NR stemmed from the same architectural shift that motivated SS-RSRP: the move away from always-on CRS. Since the primary signals for initial access and mobility became the periodically transmitted SSBs, the quality measurement also needed to be based on these signals to maintain consistency and accuracy.
SS-RSRQ addresses the critical problem of interference assessment in cellular networks. A cell might have a strong SS-RSRP, but if the surrounding interference (from other cells or noise) is also very high, the actual quality of the communication link can be poor, leading to low throughput and high error rates. Relying solely on signal strength (SS-RSRP) for mobility decisions could cause a UE to camp on or handover to a heavily interfered cell. SS-RSRQ provides the necessary additional dimension to make more intelligent decisions. It solves the limitation of having only a power metric by incorporating the interference-plus-noise floor, enabling the network and UE to differentiate between a truly good cell and a strong-but-congested one. This is especially vital for the success of 5G networks, which aim for ultra-dense deployments and high spectral efficiency, where interference management is paramount.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (20 CRs across 4 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-15, normative work from Rel-16.
In Release 16, no new SS-RSRQ functionality is introduced in the provided grounding context. The text only reiterates existing assumptions for SS-RSRQ measurements, such as the constant EPRE across the bandwidth and the 0 dB ratio between SSS and PBCH DM-RS EPRE. The listed Change Requests pertain to other areas like positioning, sidelink, carrier aggregation, and NR-U, not to the SS-RSRQ measurement procedure itself.
- CR for parameter name alignment and reference corrections in PRS reception procedure TS 38.214CR0152
- CR on timestamp reference in NR positioning measurement report TS 38.214CR0172
- Corrections for transmitting sidelink reference signals in TS 38.214 TS 38.214CR0197
- 38.214 CR on unaligned frame boundary CA with A-CSI-RS transmission and CSI reference resource definition TS 38.214CR0200
- Corrections to RSSI definition for NR-U TS 38.215CR0026
In Release 17, the key change for SS-RSRQ was the introduction of corrections to its measurement definition, along with corrections to the RSSI measurement definition. These clarifications were made to ensure accurate and consistent UE measurement reporting. The release did not alter the fundamental assumption that, for the purpose of SS-RSRQ measurements, the downlink EPRE is constant across the bandwidth.
- Clarification of a field in SCI format 2-C indicating the time offset of the first resource of each tuple with respect to the reference slot TS 38.214CR0401
- Corrections to SS-RSRQ and RSSI measurement definitions TS 38.215CR0043
- Update applicability for Tx modulation quality test cases TS 38.522CR0125
- Update 38.522 for 7.3A.3 Reference sensitivity power level for 4DL CA TS 38.522CR0263
- CR on reference point for UL SRS-RSRP TS 38.215CR0041
In Release 18, the primary update for the SS-RSRQ function was the addition of missing applicability to new SS-RSRQ test cases for Reduced Capability (RedCap) UEs. This work, based on the provided Change Request titles, specifically involved ensuring the proper test coverage and validation of SS-RSRQ measurements for these new RedCap device categories, complementing similar updates made for SS-RSRP RedCap testing.
- 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 to reference point for NG-RAN measurement for UL SRS-RSRP and UL SRS-RSRPP TS 38.215CR0070
- Addition of missing applicability to new SS-RSRQ RedCap test cases TS 38.522CR0393
- Addition of missing applicability to RedCap SS-RSRP test cases TS 38.522CR0425
- Update of applicability for RRM RedCap SS-RSRP test cases TS 38.522CR0524
+ 2 more changes
In Release 19, clarifications and corrections were introduced regarding the maximum number and simultaneous usage of specific measurement resource sets. These changes addressed the configuration limits for SRS-RSRP and CLI-RSSI measurement resource sets, which are related but distinct procedures from SS-RSRQ. The core SS-RSRQ measurement principle itself, where the UE assumes constant downlink EPRE across the bandwidth for synchronization signals, remained unchanged from previous releases.
Explore further
Broader topics and technologies where SS-RSRQ plays a role.
Defining Specifications
3GPP specifications that define or reference SS-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 |
| TS 38.522 vj11 | UE Conformance Test Applicability Statement | Rel-19 |