Why Signal Bars Are Insufficient
The signal bar display on smartphones is a proprietary, OS-specific representation that varies between manufacturers and operating systems. Each manufacturer maps raw dBm values to bar counts using their own thresholds, which are not standardized. A "4-bar" display on one device may correspond to a substantially different RSRP value than on another device.
Additionally, signal bars typically reflect only signal strength (RSRP), not signal quality (RSRQ) or interference (SINR). A phone can show full bars from a strong but heavily loaded or interfered cell, while experiencing poor data performance.
RSRP — Reference Signal Received Power
RSRP (Reference Signal Received Power) is the average power of the LTE or 5G reference signals received by the device, measured in dBm. It is the most fundamental indicator of signal strength in LTE/5G networks.
| RSRP Range (dBm) | Signal Level | Expected Performance |
|---|---|---|
| ≥ −80 dBm | Excellent | Maximum throughput, stable connection |
| −80 to −90 dBm | Good | High throughput, stable connection |
| −90 to −100 dBm | Fair | Adequate data, possible occasional drops |
| −100 to −110 dBm | Poor | Reduced throughput, reconnection may occur |
| < −110 dBm | No signal / Edge of coverage | Service unreliable or unavailable |
RSRQ — Reference Signal Received Quality
RSRQ (Reference Signal Received Quality) is a ratio that accounts for interference from other cells and the overall load on the serving cell. It is calculated as:
RSRQ = (N × RSRP) / RSSIWhere N is the number of physical resource blocks (PRBs) of the RSSI measurement bandwidth, and RSSI is the total received wideband power. RSRQ values range from −3 dB (excellent) to −19.5 dB (poor).
| RSRQ Range (dB) | Signal Quality |
|---|---|
| −3 to −9 | Excellent |
| −9 to −12 | Good |
| −12 to −15 | Fair |
| −15 to −19.5 | Poor |
SINR — Signal to Interference and Noise Ratio
SINR (Signal to Interference and Noise Ratio) measures how much stronger the desired signal is compared to background interference and noise, expressed in decibels. It is one of the strongest predictors of achievable data throughput in LTE and 5G networks.
| SINR Range (dB) | Network Condition | Modulation Achievable |
|---|---|---|
| > 20 dB | Excellent | 256-QAM (highest throughput) |
| 13–20 dB | Good | 64-QAM or higher |
| 0–13 dB | Fair | 16-QAM or lower |
| −3 to 0 dB | Poor | QPSK (basic modulation) |
| < −3 dB | Very poor | Connection may drop |
5G NR Specific Metrics
5G NR uses equivalent metrics with slight naming differences:
- SS-RSRP (Synchronization Signal Reference Signal Received Power)
- The 5G equivalent of LTE RSRP, measured from synchronization signal blocks (SSBs).
- SS-RSRQ (Synchronization Signal Reference Signal Received Quality)
- The 5G equivalent of LTE RSRQ.
- SS-SINR (Synchronization Signal Signal to Interference and Noise Ratio)
- The 5G equivalent of LTE SINR. Interpretation ranges are similar to LTE SINR.
In NSA mode, devices also report LTE metrics for the anchor cell alongside 5G NR metrics for the secondary cell.
Measurement Tools and Apps
The following tools can display live RSRP, RSRQ, and SINR values on a smartphone:
Android
- Network Cell Info Lite — Displays RSRP, RSRQ, RSSNR for the serving cell and neighboring cells. Shows cell ID, band, and frequency. Free on Google Play.
- NetMonitor Cell Signal Logging — Logs signal metrics over time with export capability. Useful for systematic coverage testing.
- Device diagnostic (field test mode) — Available via
*#*#4636#*#*(varies by manufacturer) or in Developer Options. Shows raw modem data.
iOS (iPhone)
- Field Test Mode — Accessible by dialing
*3001#12345#*and tapping Call. Shows serving cell RSRP, RSRQ, SINR under LTE/5G tabs. Not all metrics are shown on all iOS versions. - Network Signal Info (paid) — Third-party app showing detailed signal information on iOS.
Dedicated Test Equipment
For systematic coverage measurements, professional tools include the Rohde & Schwarz TSMW, Anritsu MT8000A, and similar spectrum analyzers. These are used by operators and network planning firms for drive tests and indoor surveys.
Speed Tests
Speed tests measure the achievable download and upload throughput over the current network connection. While not a substitute for RF metrics, they provide a user-perspective view of actual performance.
The Bundesnetzagentur Breitbandmessung tool (breitbandmessung.de) is the official German measurement tool. It is used for regulatory reporting and allows users to contribute measurements to the official database. The tool measures download speed, upload speed, latency, and packet loss.
Third-party tools such as fast.com (Netflix) and speedtest.net (Ookla) are widely used but measure to specific server locations and may reflect server capacity or internet routing rather than the radio access network alone.
Frequently Asked Questions
What RSRP value should I have for reliable voice calls?
For VoLTE calls, RSRP above −100 dBm is generally sufficient. Below −105 dBm, call quality may degrade. Below −110 dBm, call drops become likely unless the cell is uncongested and SINR remains adequate.
Why do my metrics change when I move a few meters?
Indoor signal levels can vary dramatically over short distances due to multipath interference — radio waves arriving at the device via multiple reflected paths interfere constructively or destructively at specific points. Moving even 0.5–1 meter can shift the interference pattern and change RSRP by 10–15 dB.
Can I measure 5G signal strength on a 5G device?
Yes. Apps like Network Cell Info Lite on Android can display 5G NR SS-RSRP and SS-SINR values when the device is connected to a 5G cell. The display requires the device to have 5G capability and be in 5G coverage. In NSA mode, both the LTE anchor and NR secondary cell metrics may be shown.