2010-07-02

Signal-strength-to-bars mapping on iPhone 4

Apple released the statement today that they were "stunned to find" (could they be any more dramatic?) that the formula used to map signal strength to bars on the iPhone 4 is "totally wrong".  They state they will fix the problem by reducing the number of bars displayed for a given signal strength.

"Our formula, in many instances, mistakenly displays 2 more bars than it should for a given signal strength.  For example, we sometimes display 4 bars when we should be displaying as few as 2 bars. Users observing a drop of several bars when they grip their iPhone in a certain way are most likely in an area with very weak signal strength, but they don’t know it because we are erroneously displaying 4 or 5 bars. Their big drop in bars is because their high bars (sic) were never real in the first place (sic again)."

HOWEVER I claim that they will increase the number of bars for weak signals, and only decrease the number of bars for medium-strength signals.  Here's the reasoning:

  • The open letter implies several times that when the number of bars is low, the reading doesn't reflect the actual operability of the phone, i.e. that the low end of the bar scale is too low: "iPhone 4 can drop 4 or 5 bars when tightly held...This is a far bigger drop than normal, and as a result some have accused the iPhone 4 of having a faulty antenna design.  At the same time, we continue to read articles and receive hundreds of emails from users saying that iPhone 4 reception is better than the iPhone 3GS. They are delighted. This matches our own experience and testing...The iPhone 4's performance is the best we've ever shipped".
  • They say "To fix this, we are adopting AT&T’s recently recommended formula for calculating how many bars to display for a given signal strength", but it's impossible to believe that they'll just apply AT&T's formula without tweaking it if you also believe their claims that the iPhone 4 really is better at operating on a weak signal than previous phones -- because bars are a subjective measure of the cellphone's ability to connect over the cell network.  These two claims simply don't match up.  They'll jack up the number of bars compared to the AT&T recommendation if it really is true the iPhone 4 can get the same quality of connection on a weaker signal than previous iPhones.
  • There would be a public outcry if they just drop the signal threshold for each of the bars (a drop of 4->2 could now be 2->1 or 2->0 if they are just displaying "two more bars than we should"), or even if they just dropped the signal strength threshold of the high-numbered bars -- "I got the iOS update and now my phone has a weaker signal than ever!".  The whole problem is that people believe bars and don't understand the science or math behind the bars.
  • Apple's magic fix for previous iPhone signal strength problems was supposedly an inflation of the number of displayed bars.  (It keeps people happier.)

The great irony of all this is that it appears Apple has been caught red-handed trying to inflate their signal strength in the first place...

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