By using field test mode *3001#12345#*, we can check the RSRP, RSRQ, SINR0, SINR1 information of the serving cell. But i have observed when RSRP was as good as or better than -85dBm, the signal bar is showing only 2 bars. It seem like iPhone is using difference method to display signal bar instead of only based on signal strength (i.e: RSRP). But what is the method that iPhone using to display the signal bar?
iPhone 16 Pro Max, iOS 18
Apple does not define what each bar represents. As you know the Power is just one part of the Signal, and you also have Quality and the Signal-Noise Ratio, which are all relevant when determining the representation of a cell signal.
I would not consider -85dBm as being a great number. It falls in the middle of what would be expected, so a 2 bar signal strength on your iPhone may actually be more valid than you think.
None of that is published.
Across all vendors, signal bars are centrally designed to avoid support calls to Apple and to the carrier.
(This design goal parallels the designs of instrument gauges used in computer-controlled vehicles.)
The signal strength displayed bars can vary by vendor, device, and firmware version, as well.
How does iPhone define signal bars?
