Apple’s fix doesn’t fix your iPhone Signal

Graph of how the iPhone interprets signal reception, and how the Hold effect changes the signal.

With the announcement of Apple’s software fix, many people have begun to believe that all of their iPhone 4 signal problems will soon be a thing of the past. Unfortunately that is not quite the case. The signal problem experienced by some but not all users is a combination of software AND hardware defect. As you can see from the chart above the iPhone 4 is programmed to show the user that they have signal strength of 4+ bars as long as they have a Signal to Noise Ratio greater than -90dBm.

Normally this would not be a problem since a SNR near -90dBm is more than adequate to make a phone call. However once the phone is held in a users left hand with the palm covering the “dead zone” the phone experience a drop of 19dBm on average.

Imagine you are using the phone in a well covered area. You are likely to have an SNR of -50dBm or more, so when you hold the phone in your left hand, your signal will be hurt, but not damaged enough to prevent you from making phone calls. However, if you are using the phone and you happen to be on the bottom range of “adequate” SNR (i.e. -90dBm) the 19dBm drop will be enough to prevent you from making calls.

The software “fix” Apple is releasing does nothing to solve the signal attenuation (hardware) issue in the iPhone 4, but rather, simply, makes a change to the graph above. Now when an iPhone is used in an area of -90dBm the phone may show 2 or 3 bars instead of the 4 it used to. Calls can still be made, but should the phone end up in the palm of the user they won’t be quite as surprised to see the signal drop to one bar or even zero. Thus Apple’s “fix” is more about managing expectations rather than actually fixing the issue. Many engineers have said that the only way to actually fix the problem is to reengineer the phone which could take months as a “new” model would have to pass all FCC regulations again.

After having sold 1.7 million iPhones in just the first week of sales it remains to be seen if Apple will put forth a concrete solution to this problem. At the moment, a case seems like the best solution.

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