This graphic shows why some people experience the iPhone 4 signal drop problems while others haven't been able to reproduce it. It also explains why Apple's incoming software update—which promises more accurate signal bars—won't fix the antenna problem.
Which is sad, because I was hoping for a real fix to the antenna problem itself, not just the signal display (I want this phone badly, but I want it to work well at all times). After talking with some wireless engineers, it seems that this is not going to be the case. Michael Anderson, who used to work at Motorola's FCC testing lab, points out that "it's a fundamental flaw that can only be fixed through a redesign. If that is redone, all the FCC will have to be completed again. This may be a long slow process to fix."
In his reply to Apple's letter, Richard Gaywood—PhD on wireless network design from Cardiff University—thinks the signal display fix is a good step to fix user perception, but it won't fix the antenna interference problem that exists in the iPhone 4:
But if there is no design issue at work here, why did Anandtech and I both show significantly different attenuation when holding an iPhone 4 in a bare hand compared to holding it in a case? And why did Apple themselves recommend "using a case" as a possible solution to the problem?
The antenna interference problem
According to wireless experts consulted by Gizmodo, the iPhone 4 antenna interference problem happens to everyone, and it's not a matter of signal bars displayed in the phone. However, some people are not noticing it. Why?
Although Anandtech believes the iPhone 4 holds calls better than the previous iPhones under poor signal strength ("From my day of testing, I've determined that the iPhone 4 performs much better than the 3GS in situations where signal is very low, at -113 dBm (1 bar).") he notes that hand position and touching the antenna in the lower left hand spot also causes more interference. Scientific tests conducted by Anandtech, there's always up to a 19.8dB signal loss when you grab the iPhone naturally with your hand, with your skin touching the deadly spot. That's losing signal by a factor of almost 100. The iPhone 3GS only loses 1.9dbs in this case, which is less than double.
Experiencing this transmission/reception loss, however, depends on the strength of the signal itself:
• If your signal-to-noise ratio is perfect—like when you have a clear line of sight with a cell tower that is not overloaded—a typical 19.8dB attenuation will leave you with a healthy data transmission. In this case, the interference will not cause any problems to your normal usage of the iPhone 4. Your web pages will load normally and your calls will work just fine.
• However, you can experience the transmission and reception problems when you're working with a moderate quality signal. Since no wireless network provides us with optimal transmission absolutely everywhere, every iPhone 4 user is likely to encounter such problems at some point. In these cases, depending on the signal-to-noise ratio level, the attenuation caused by your hand may make your iPhone 4's signal health drop into dangerous areas, causing data loss and voice quality degradation.
• In the worst case, if the base signal is anywhere from moderate to bad, you will not be able to make calls or receive any data at all, like this video shows:
The problem with the signal bars display
Apple claims that this is all a problem with the way your iPhone 4 displays bars. Like wireless engineer and PhD from Cardiff University Richard Gaywood explains, there is indeed a disparity between the actual signal and the bars displayed in your iPhone 4.
Like Apple explains, the iPhone 4 doesn't display signal bars correctly. So you may have five bars and your signal may be excellent or your signal may be regular, while it probably should be displaying three bars.
This disparity explains why—when you touch the problematic antenna spot—some users can't get the display to drop from five bars. No matter how hard they try the death grip, the iPhone still shows five bars and the data will keep flowing. But then, other people with five bars will see the phone drop to one bar the moment they hold their iPhone in their hand, touching the bottom left corner dead spot.
As the graphic shows, in the best case scenario starting with five bars, a 19.8dB attenuation has no effect on the iPhone bar display or performance. In the worst case scenario starting with five bars, however, grabbing the iPhone will make both the signal bars and the quality of the signal to drop to bad levels.
Perception vs Reality
LIke Gaywood says in his article commenting on Apple's statement, "making the bars more closely represent reality is a step forward, and I believe the perception of the size of the problem has certainly been exaggerated by the miscalibration."
Apple's position is that the reception strength is so much better on the iPhone 4 that, even with the attenuation factored in, it's still better than the 3GS. They, of course, would say that; they've just sold a couple of million of the things. Maybe they're right but I remain unconvinced. The problem isn't as big as some people are saying - but it's not the non-problem Apple are trying to paint it as either.
By making the bars display the actual signal strength, Apple will avoid the bars going from five to zero. They will fix a perception problem. But if you have experienced it already, the data loss will still happen when you hold the phone. The only difference is that, after the update, touching the dead spot will make you go from three bars to one or zero. The jump in bars won't be as dramatic, but the signal attenuation will still happen.
Fixing the real problem
So yes, there is a problem with the way the iPhone 4 display bars. And yes, there is a problem with signal attenuation while grabbing the phone that results in data loss and voice degradation.
Apple says that they will fix the former in an incoming update. But their update will not affect the latter.
The real problem still remains: According to the wireless experts, there is an antenna design problem. Anandtech says, even after his praise of the design, "At the end of the day, Apple should add an insulative coating to the stainless steel band, or subsidize bumper cases. It's that simple."
And I hope they fix it soon without requiring a rubber band, because I want the iPhone 4 badly. Every time I see the amazing display, the speed, and the camera in action, I have cravings.
If you are an iPhone 4 user experiencing the antenna problem, sign the petition for a real, free solution.