Apple iPhone: Code analysis shows how a 20-byte error could have resulted in Antennagate
The Apple iPhone 4 suffered one of the biggest scandals in iPhone history, Antennagate. The issue was so widespread that Apple founder Steve Jobs declared at a hastily convened emergency press conference that users were holding the iPhone 4 incorrectly.
To address the issue, Apple gave customers a free bumper case designed to prevent users from touching the antenna integrated into the frame. The company also released a firmware update to iOS 4.0.1 that was supposed to resolve the issue. The update didn't resolve the issue in all cases, as the iPhone 4's antennas did indeed lose signal strength when touched by hand, but there were far fewer Antennagate complaints from users after the update.
Sam Henri Gold has now examined the code changes in detail, discovering that Apple only had to change around 20 bytes to curb the spread of Antennagate. Prior to the update, the iPhone 4 displayed five bars even with relatively weak signal strength. However, as soon as the signal strength dropped slightly, two or three fewer bars were displayed. This made the actual signal loss when touching the antenna appear much more drastic than it actually was.
With iOS 4.0.1, Apple adjusted the 20 values that determine how many bars are displayed at what signal strength, based on the recommended values of US network operator AT&T. At a signal strength that previously displayed five bars, there were suddenly only two bars, so users had a more realistic display of signal strength even before touching the antenna, and the impact of the signal loss caused by touching was displayed more moderately.
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