iPhone 4 signal issues: Blame the formula, says Apple

Is too much bar-hopping a result of a maths mistake?
Written by Jo Best, Contributor

Is too much bar-hopping a result of a maths mistake?

Apple has responded to reports of signal problems with the iPhone 4.

Since its launch last month, users have been reporting that when they hold the iPhone 4 in a particular way, the device's signal strength can drop noticeably.

According to Apple, some users have reported signal strength falling by four or five bars when the phone is "tightly held in a way which covers the black strip in the lower left corner of the metal band". The band, which runs around the device's outer edge, is part of its antenna system.

iPhone 4's stainless steel band

The stainless steel band that wraps around the iPhone 4
(Photo credit: Apple)

The company today published a statement on the issue it claims is causing the drop in reception.

"Upon investigation, we were stunned to find that the formula we use to calculate how many bars of signal strength to display is totally wrong. Our formula, in many instances, mistakenly displays two more bars than it should for a given signal strength. For example, we sometimes display four bars when we should be displaying as few as two 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 four or five bars. Their big drop in bars is because their high bars were never real in the first place," Apple said.

Given that, according to Apple itself, users are reporting a drop of four or five bars, and Apple reports that the formula mistake means the iPhone 4 can show two extra bars of signal strength, it would suggest that gripping the phone in a particular way can often cause a drop of around two bars of signal strength.

Apple has yet to respond to request for confirmation that the falling bars are a result of a real drop in signal quality, albeit an exaggerated one. In its statement today, however, the company did note: "Gripping almost any mobile phone in certain ways will reduce its reception by one or more bars".

According to the company, the faulty formula was also used on earlier iPhone models, the iPhone 3G and 3G S.

"To fix [the formula problem], we are adopting [US mobile carrier] AT&T's recently recommended formula for calculating how many bars to display for a given signal strength. The real signal strength remains the same but the iPhone's bars will report it far more accurately, providing users with a much better indication of the reception they will get in a given area," Apple said.

Apple iPhone 4

Apple's forthcoming iPhone 4 smartphone
(Photo credit: James Martin/CNET)

Apple will also be "making bars 1, 2 and 3 a bit taller so they will be easier to see" - a welcome development for those with worse than average sight perhaps, but unlikely to make a difference to those experiencing signal drops.

"We will issue a free software update within a few weeks that incorporates the corrected formula," the company said, adding: "For the vast majority of users who have not been troubled by this issue, this software update will only make your bars more accurate."

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