The Mapping Problem
When you decode an RRC Measurement Report, RSRP values are not transmitted in dBm. The UE sends an integer range index, and the network (and your analysis tool) must convert it back to an actual power level.
The catch: LTE and 5G NR use different mapping formulas. If you apply the wrong offset, your handover analysis is off by 16 dB.
The 3GPP Conversion Formulas
LTE (TS 36.133, Section 9.1.4)
RSRP (dBm) = range_value - 141
Valid range: 0 to 97
Maps to: -141 dBm to -44 dBm
5G NR (TS 38.133, Section 10.1.6.1)
RSRP (dBm) = range_value - 157
Valid range: 0 to 127
Maps to: -157 dBm to -30 dBm
The 16 dB offset difference between the two formulas comes from NR’s extended measurement range, designed to handle mmWave propagation where signal levels drop well below LTE’s minimum reporting threshold.
Why This Matters for Handover Analysis
When a Measurement Report carries threshold-RSRP = 30, the actual trigger level depends on the RAT:
- LTE: 30 - 141 = -111 dBm
- NR: 30 - 157 = -127 dBm
If your post-processing tool applies the LTE formula to NR data (or vice versa), every threshold comparison in your handover analysis will be shifted by 16 dB. That is enough to completely misinterpret cell reselection behavior.
Quick Field Example
You capture a MeasurementReport with these values:
| Parameter | Reported Value | LTE Conversion | NR Conversion |
|---|---|---|---|
| RSRP range | 45 | -96 dBm | -112 dBm |
| RSRP range | 62 | -79 dBm | -95 dBm |
| threshold-RSRP | 30 | -111 dBm | -127 dBm |
If you mix up the formulas, you might conclude a cell has adequate coverage when it is actually 16 dB below your threshold.
Full Mapping Tables
For complete RSRP/RSRQ/SINR threshold mapping tables with both LTE and NR formulas verified against 3GPP specifications:
3GPP RSRP Threshold Mapping Reference (interactive, all ranges)
For more RF diagnostic tools (ARFCN calculator, EARFCN lookup, NCI decoder):
Takwa Sebai | HiCellTek | Pro 4G/5G diagnostics on Android