Description
Narrowband Reference Signal Received Power (NRSRP) is a key radio measurement specific to Narrowband Internet of Things (NB-IoT) and LTE-M (Cat-M1) technologies within the 3GPP LTE and 5G NR frameworks. It represents the linear average power received by a User Equipment (UE) over the resource elements that carry narrowband reference signals (NRS) within a specified measurement bandwidth, typically 180 kHz for NB-IoT. NRSRP is derived from the downlink reference signals transmitted by the base station (eNodeB in LTE, gNB in NR), which are designed for channel estimation and synchronization. The measurement process involves the UE demodulating these reference signals, which are spaced in time and frequency across the narrowband carrier, and calculating the received power in units of dBm. This value is crucial for evaluating signal strength in low-power, wide-area scenarios where IoT devices often operate in challenging radio conditions, such as deep indoors or rural areas. NRSRP is used by the UE for cell selection and reselection procedures, determining the best cell to camp on based on signal quality. It also informs handover decisions and power control mechanisms, ensuring reliable connectivity while minimizing battery consumption. The measurement is reported to the network via Radio Resource Control (RRC) signaling, enabling the network to optimize resource allocation and coverage. Compared to wider-band measurements like RSRP in legacy LTE, NRSRP is tailored for narrowband operations, providing accurate assessments in bandwidth-constrained environments essential for IoT deployments.
Purpose & Motivation
The purpose of Narrowband Reference Signal Received Power (NRSRP) is to address the unique requirements of IoT devices in cellular networks, particularly for NB-IoT and LTE-M technologies introduced in 3GPP Release 13 and beyond. Traditional LTE measurements like RSRP were designed for wider bandwidths (e.g., 1.4 MHz to 20 MHz) and higher data rates, which are inefficient for IoT devices that prioritize low power consumption, extended coverage, and operation in narrow bandwidths (e.g., 180 kHz). NRSRP was created to provide a precise signal strength measurement optimized for these narrowband carriers, enabling accurate cell evaluation in environments with limited spectrum and challenging propagation conditions. It solves problems like reliable cell selection in coverage-enhanced modes (e.g., up to 20 dB additional gain for NB-IoT), where devices need to detect very weak signals. The motivation stems from the proliferation of massive IoT applications, such as smart meters, sensors, and trackers, which require long battery life and robust connectivity in areas with poor signal strength. By introducing NRSRP, 3GPP enabled efficient radio resource management for IoT, supporting features like extended discontinuous reception (eDRX) and power saving mode (PSM), ultimately facilitating scalable and energy-efficient IoT deployments.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (8 CRs across 3 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-14, normative work from Rel-16.
In Release 16, the NRSRP function itself was not updated within the provided context; however, the release introduced new positioning-related reporting capabilities. Specifically, it added a description for the timestamp reference within the NR positioning measurement report. Additionally, Release 16 included corrections to the reference Transmission Reception Point (TRP) for reporting in the Downlink Angle-of-Departure (DL-AoD) and Multi-Round Trip Time (Multi-RTT) measurement procedures.
- Introduction of B1C signal in BDS system in A-GNSS TS 37.355CR0248
- Update B1I signal ICD file to v3.0 in BDS system in A-GNSS TS 37.355CR0259
- Description on timestamp reference in NR positioning measurement report TS 37.355CR0311
- Correction of reference TRP for DL-AoD and Multi-RTT measurement report TS 37.355CR0330
In Release 17, no new changes were introduced for the NRSRP (Narrowband Reference Signal Received Power) function itself, as the CR titles and grounding context pertain to corrections in other measurement procedures like GNSS SSR and Rx timing error, as well as OAM requirements for collecting existing NRSRP distribution data. The grounding context only describes pre-existing use cases where network management collects cell-level NRSRP distribution information from UEs, a capability established prior to Release 17. Therefore, the release focused on clarifications and corrections in adjacent areas rather than modifying the NRSRP measurement procedure.
- Corrections on applicability of timing error margin of RxTEG in NR-Multi-RTT-SignalMeasurementInformation field descriptions and other Miscellaneous corrections TS 37.355CR0431
- GNSS SSR BDS orbit emphemeris reference clarification to align with RTCM TS 37.355CR0461
- Clarifying Galileo NAV message in the GNSS Navigation model to clarify SSR clock correction signal reference TS 37.355CR0412
In Release 19, the new development for NRSRP was the introduction of a standardized network management capability to collect and report its performance measurements. Specifically, this allowed the network operator to receive cell-level distribution information of NRSRP values reported by UEs in an NB-IoT cell via the OAM system. This functionality was added to existing management specifications, aligning NRSRP reporting with similar procedures already defined for RSRP.
- Introduction of B2b signal in BDS system in A-GNSS TS 37.355CR0545
Explore further
Broader topics and technologies where NRSRP plays a role.
Defining Specifications
3GPP specifications that define or reference NRSRP, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 32.857 vf00 | Management of LTE IoT RAN Features | Rel-15 |
| TS 36.355 vj00 | LTE Positioning Protocol (LPP) | Rel-19 |
| TS 37.355 vj20 | LTE Positioning Protocol (LPP) | Rel-19 |