Comment Re:Formula change (Score 1) 534
Please excuse me if this sounds pedantic but it is relevant for the subject.
When we're talking about levels of -51, -91, -113, etc., these are probably GSM signal levels, and the unit should be dBm.
dB alone is just a ratio, which is suitable for indicating for example Ec/Io, which is sort of signal to noise ratio when in WCDMA mode (the iPhone, being an UMTS phone can use GSM or WCDMA). -113, -51 do not look like Ec/Io values (these are good around -10dB).
When in WCDMA mode, Ec/Io is much more relevant than signal level and I believe phones show bars proportional to that. When in GSM mode, signal level is more relevant, and phones show bars proportional to that.
In WCDMA mode, the level is much less important than the phone capacity of extracting meaning out of the noise. You may have a very low signal level, but if the Ec/Io is good, you can place a call. You may have a high signal level, and not be able to place a call if your Ec/Io is poor. This is also true (but not as critical) for GSM mode.
A conclusive test or comparison should not be based only on signal levels, but use a proper GSM/WCDMA phone test equipment, capable of generating different signal levels (GSM) and Ec/Io (WCDMA), then collecting the phone's received Bit Error Rate, or Frame Error Rate. Believing in the level information the phone itself informs and relating that to dropped calls is quite subjective, as it is not a controlled environment, and what the phone informs may be wrong.
In the analog times (AMPS), signal level was all you could measure, and interference just meant the sound would be crappy (and the occasional undesired "group call"). If there was a good signal level, you could place the call (but the quality could be awful, there was no way of knowing).
With digital, bit error rate is what matters, and signal quality is more important than signal level. As long as the received signal level is above the phone's sensitivity (and here is a place where you separate manufacturers who know their RF from the ones who don't), then that's "level enough". It doesn't help to have a lot of signal strength (power) if due to the signal quality (signal/noise) or your hardware/software quality you cannot pull the useful data from it.
In the digital age, it's not the size of your signal which matters, but what you manage to do with it.