Description
SS-RSRP (Synchronization Signal based Reference Signal Received Power) is a fundamental radio resource management (RRM) measurement defined in 3GPP New Radio (NR) standards. It is a linear average over the power contributions (in watts) of the resource elements that carry the secondary synchronization signals (SSS) within the synchronization signal/physical broadcast channel (SS/PBCH) block, commonly known as the SSB. The measurement is performed by the user equipment (UE) on the downlink signals transmitted by the gNodeB. The SSB is a critical signal structure that is periodically broadcast by the cell, containing the Primary Synchronization Signal (PSS), Secondary Synchronization Signal (SSS), and the Physical Broadcast Channel (PBCH). SS-RSRP measurement specifically focuses on the SSS, as it provides a stable and cell-specific reference. The UE measures the power of these specific resource elements after performing necessary synchronization and channel estimation procedures.
The architecture supporting SS-RSRP involves the UE's physical layer processing chain. Upon powering on or during mobility events, the UE scans for SSBs across different frequency bands and beam directions. Once an SSB is detected and its timing is acquired, the UE isolates the resource elements corresponding to the SSS within that SSB. The power of these REs is measured, typically involving filtering to average out fast fading and interference effects, resulting in a stable RSRP value reported in dBm. This measurement is then reported to the higher layers (Layer 3) of the UE's protocol stack and can be further reported to the network via measurement reports (e.g., in RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED states) to assist network decisions.
SS-RSRP plays a central role in several network functions. It is the primary metric for cell selection and reselection procedures, where the UE compares the SS-RSRP of the serving cell and neighboring cells against predefined thresholds (e.g., Squal, Srxlev). For handover and beam management, SS-RSRP measurements of different SSBs (which correspond to different beams in FR2) are used to determine the best cell or beam for connectivity. The network configures measurement objects, reporting configurations, and event triggers (like A3, A5 events) based on SS-RSRP. Its accuracy and reliability are paramount, as errors can lead to ping-pong handovers, call drops, or suboptimal cell attachment, directly impacting user experience and network performance.
Purpose & Motivation
SS-RSRP was introduced in 3GPP Release 15 as part of the 5G NR standardization to provide a standardized, accurate method for measuring downlink signal strength from synchronization signals. In previous generations like LTE, RSRP was measured based on Cell-Specific Reference Signals (CRS). However, 5G NR introduced a more flexible and beam-centric design, where the always-on CRS was eliminated to save overhead and energy. The SS/PBCH block became the primary signal for initial access and mobility. Therefore, a new measurement analogous to RSRP, but based on the SS block, was necessary. SS-RSRP solves the problem of providing a consistent reference for signal power in a network where reference signals are not continuously transmitted.
The creation of SS-RSRP was motivated by the need to support efficient mobility in diverse 5G deployment scenarios, including high-frequency bands (mmWave) with beamforming. In these scenarios, signal quality can vary significantly across different beams. SS-RSRP measurements per SSB (beam) allow the UE and network to identify the strongest beam for communication. It addresses the limitation of LTE's CRS-based RSRP, which was not suitable for the bursty, beam-swept transmission of SSBs in NR. By defining the measurement specifically on the SSS, it ensures a cell-specific and stable power estimate that is decoupled from potential power variations in other channels, enabling reliable radio link monitoring and mobility decisions in the 5G ecosystem.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (79 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the specification text does not contain information regarding newly introduced aspects of the SS-RSRP function. The provided grounding context exclusively details requirements for NR Integrated Access and Backhaul (IAB) nodes, including radiated and conducted reference points and co-location specifications. The listed Change Request titles pertain to uplink transmission procedures and PDSCH scheduling, not to SS-RSRP.
In Release 16, the SS-RSRP function was enhanced to support new operational scenarios, including NR-based access to unlicensed spectrum and operation for Integrated Access and Backhaul (IAB) nodes. The specifications introduced new requirements for measuring SS-RSRP in these contexts, such as for IAB-MT and IAB-DU types with radiated and conducted reference points. Furthermore, corrections and alignments were made to related procedures, including sidelink resource pool determination and the PRS reception procedure, to ensure consistent SS-RSRP measurement and reporting.
- Introduction of NR-based access to unlicensed spectrum TS 38.215CR0013
- Correction on 38.214 for PUSCH with UL skipping (Note: CR was not implementable because "not based on the latest version of the specification") TS 38.214CR0123
- Corrections to NR-based access to unlicensed spectrum TS 38.214CR0129
- Correction on sidelink resource pool determination based on PSBCH TS 38.214CR0141
- CR for parameter name alignment and reference corrections in PRS reception procedure TS 38.214CR0152
- CR on L1-SINR based beam measurement TS 38.214CR0163
+ 4 more changes
In Release 17, the SS-RSRP function itself did not receive new procedural enhancements according to the provided context. The release included corrections and clarifications to related measurement definitions, such as for SS-RSRQ and RSSI. Furthermore, the release introduced new test applicability, including for NR SA FR2 SSB based Inter-cell L1-RSRP measurement in non-DRX test cases, which relies on the foundational SS-RSRP measurement.
- Introduction of NR UE Power Saving Enhancements TS 38.214CR0236
- Introduction of Timing advance (TA) PRACH based solution for NR UL E-CID [NRTADV] TS 38.215CR0038
- Correction to IAB-MT timing reference point in TS 38.174 TS 38.174CR0042
- Corrections on NR UE Power Saving Enhancements TS 38.214CR0258
- Correction on CQI derivation accounting for provided DL Tx power adjustment for IAB-MT TS 38.214CR0308
- Correction on uplink suspension for CA-based SRS carrier switching TS 38.214CR0312
+ 16 more changes
In Release 18, the primary enhancements for the SS-RSRP function focused on expanding test applicability for Reduced Capability (RedCap) devices, as indicated by the Change Request for the addition of missing applicability to RedCap SS-RSRP test cases. Furthermore, corrections and updates were made to ensure consistent measurement procedures, such as those impacting gap-based measurement tests which also affect measurement reliability. These updates ensured that SS-RSRP requirements and validation were properly extended to support new device categories and operational scenarios introduced in the release.
- Corrections on RRC parameters for R18 NES spatial/power domain adaptation TS 38.214CR0544
- Correction on contiguous RB based resource allocation TS 38.214CR0550
- Correction of power consistency and phase continuity during cell DRX operation TS 38.214CR0554
- Correction of physical channels and signals during cell DTX/DRX operation TS 38.214CR0566
- Correction on Rel-18 Type II Doppler codebook based CSI enhancement TS 38.214CR0567
- Correction on CSI processing criteria for new NES capability signaling TS 38.214CR0584
+ 33 more changes
In Release 19, the SS-RSRP function saw no direct updates within the provided scope, as the listed Change Requests and grounding specification text focus on other areas. The modifications pertain to AI/ML-based CSI prediction, Non-Terrestrial Network (NTN) power control, Extended Reality (XR) UE REFSENS tests, and transmitter power for simultaneous multi-direction transmission, but none specify changes to SS-RSRP measurement procedures or requirements.
- Correction on Rel-19 AI/ML based CSI prediction TS 38.214CR0735
- Addition of NR NTN power control test cases TS 38.522CR0634
- Applicability updates REFSENS power level test for XR UEs TS 38.522CR0657
- Update to applicability of gap-based RRM FR2 tests TS 38.522CR0653
- Addition of a new test case for transmitter power for simultaneous transmission to multiple directions TS 38.522CR0684
- Applicability for power class 6 R18 HST TS 38.522CR0702
Explore further
Broader topics and technologies where SS-RSRP plays a role.
Defining Specifications
3GPP specifications that define or reference SS-RSRP, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 38.174 vj10 | NR Integrated Access and Backhaul Radio Spec | Rel-19 |
| TS 38.176 vj20 | IAB Conformance Testing Specification | Rel-19 |
| 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 |
| TR 38.903 vj00 | Test Tolerances & Measurement Uncertainties | Rel-19 |