AnandTech on Apple’s iOS 4.0.1 signal-strength meter adjustment. Seems sensible. Click through for more great explanations and illustrations.
So, the bars represent signal strength more linearly now, which is great. Except that call quality is very non-linear with respect to signal strength! Not to mention that the data that can be recovered from a transmission depends highly on the profile of the signal and the profile of the noise. A couple of clean multipath signals will do you just as much good as a strong signal. Built in redundancies make it possible to recover a transmission despite noise and errors. This means a drop in signal strength could mean no loss at all in quality of the call.
If adaptive multi-rate codes are used to sacrifice call quality for redundancy, there will be some step down of call quality in a semi-“linear” way as signal is overwhelmed by noise, but this should be after the signal is degraded enough that AMR is needed.
I think Apple’s original mapping more closely reflects the call quality you might actually experience. As signal strength starts dropping, you should not notice any changes in call quality. As it drops further, then, you might notice a decrease as AMR codecs reduce your call quality.
Of course it’s probably not going to cut it right now to explain to the public that a 4 bar drop is not that much for a non-linear profile that tries to represent what is going on in the signal/data flow, not just what’s hitting the RF antenna. The public does not usually hear and understand engineering too well. Only Steve’s RDF can save Apple now.
