iPhone 4: The bars are a lie

There has been, well, some vigorous discussion this past week about the iPhone 4 and what those bastards at Apple have foisted upon us. People are losing their freaking minds. Lawsuits have been filed. People are threatening to take their phones back. And, of course, people have emailed Steve Jobs directly, with results of varying veracity.

Only, the thing is, it’s really not such a big deal. I know people are angry, and they have every right in the world to feel that way. And I know Apple has been unusually tone-deaf in how they’ve handled this situation, but I also think they’re doing the right thing. So let’s take a step back, look at the situation for what it really is and see how this all sorts out. (This would be a good place to take your happy pills if you need them.)


The single most striking feature of the iPhone design, which you notice even before you see the ZOMG droolworthy screen, is the stainless steel band sandwiched between the two plates of glass. This is not only the structural support for the phone, but also the antenna. The left side, from the headphone jack around past the volume buttons, is the WiFi/Bluetooth antenna, and the rest is the cellular antenna. While this design choice simplifies and minimizes the layout of the phone, it also means that you will, in the act of holding the phone, alter the the reception of the phone as you, who are essentially a bag of salt water as far as RF signals are concerned, change the conductivity of the antenna.

The result is what has become known as the "iPhone Death Grip." If you hold the phone so that your skin bridges the tiny gap between the WiFi and cellular antennas, you can watch in awe and/or horror as your signal bars drop from five to one. This "design flaw" is what all this fuss is about.

Signal attenuation, by the numbers

Sure seems like a design flaw, right? To go from full signal down to nothing just by touching the phone? Touching the phone in the exact same way you see Steve Jobs holding it in just about every picture of him and the iPhone 4 on the web?

Well, maybe, maybe not.

See, the truth is that five bars can be well removed from "full signal," and even that’s kind of a misnomer left over from analog phones that doesn’t mean much in a digital world. Let’s look at the actual math for a minute. This won’t hurt a bit.

Click to read more the by creator of this chartRF signals are measured in negative decibels. The best signal you can get, standing right next to the tower, is -51 dBm. The worst is -113, the point at which AT&T’s towers just stop trying to talk to you. Now, you would think that the bars would be evenly distributed over that 65 dBm range. But the problem is that it’s a logarithmic scale. -100 dBm is ten times weaker than -90 dBm.

As a result, you see a "full" five bars all the way down to -90 dBM. Meaning as soon as you start losing bars at all, you’re not approaching the cliff, you’re already falling off.

This is already confusing, but it gets worse. When you touch the antenna, depending on conditions (moisture, etc.) you will cause the signal to drop by 20-24 dB. If you’re in a strong "five bars" area, this will still leave you with more than 90, and thus still have "five" bars. If you’re sitting right around 90, dropping 24 dB can drop you all the way down to the cut off point, even though you started with "five" bars.

Passing the bar

Only, even that isn’t really the case. Because as I mentioned before, the whole concept of bars is a hold-over from analog cell phones and doesn’t really make sense in a digital world. With digital cell phones, signal is a binary condition. Either you have enough signal to make the call, or you don’t. (It’s the same way with digital TV over the air now. You either get a perfect picture or you get nothing, no more snow that kinda resembles your favorite show.) Numerous reports have shown that the iPhone 4 holds on to a call just fine all the way down to -111 dBm, and holds calls in places the iPhone 3GS would have dropped or not shown service at all.

Apple contends that the iPhone 4 has the best reception yet of any iPhone, and even with the attenuation problem factored in, this does in fact seem to be the case. Personally, I’ve lost a grand total of one call that I can blame definitively on the Death Grip. Granted, when I touched the antenna and dropped the signal enough to drop the call, I was already in an underground parking garage. o_O

Bump the Bumper

Apple raised eyebrows at WWDC when they announced the iPhone 4 by also announcing their first ever case for the iPhone, something they’d previously left to third party companies. The Bumper is a minimalist case that only covers the steel band around the iPhone, leaving the glass front and back mostly uncovered. Once reports of problems with the antenna surfaced, it didn’t take long for people to figure out that 2 + 2 = Conspiracy Theory!

Obviously, they say, Apple knew about this problem, and that’s why they’re ripping us off to the tune of $30 for a band of rubber and plastic to cover up the problem they knew they had! Those bastards!

Maybe, maybe not.

I’ll admit the Bumper is suspicious. And yes, it does seem to reduce, but not completely eliminate, the attenuation. But a wise man once advised to never attribute to malice what could be explained by simple incompetence. And I can also see not only why Apple would have offered the Bumper without knowing anything about the signal issue, but how they never would have seen the signal issue.

The Bumper is good for more than just antenna insulation. It also provides a good deal of shock absorption, something at which steel and glass are notoriously bad. An iPhone 4 wearing a Bumper is much less likely to crack or shatter when dropped to a hard surface on the corner than a naked iPhone. So Apple could have provided it simply because they knew the iPhone 4 might benefit from the extra protection.

As for them knowing about the signal issue, think about how this problem manifests and how Apple tested the phone. You don’t see it at all in strong signal areas where even dropping the full 24 dB still leaves you with five bars. And within the Apple campus at Cupertino, you can bet they have impeccable AT&T signal. So on campus, they’d never notice it.

Of course, they don’t just test it on campus. In fact, we know at least one radio baseband engineer who, while testing the phone in a bar, had a little too much German beer and wound up without his prototype iPhone 4. But we also know from that little escapade that when off of Apple’s campus, the iPhone 4 was hidden inside a specially built case that made it look like a 3GS. And holding it inside that case would have insulated the antenna, similar to how the Bumper works, which means they wouldn’t have seen it there either.

In short, Apple’s testing methodology seemed to guarantee that they’d never the test the iPhone naked and in poor signal at the same time. When they say they were "shocked" to discover this problem, I believe them. I really don’t think they tested it in all possible conditions.

Don’t hold it that way

Apparently, Apple was caught so off guard by this controversy that they they stumbled repeatedly in dealing with it in public. The first time a user emailed Steve Jobs himself about it, or at least the first (only?) one Jobs replied to, Jobs actually told the guy not to hold it that way. This struck most people as flippant and dismissive, which is probably why Apple quickly followed up with an official statement with more careful wording. BGR reported that Jobs also had a longer exchange with someone else where he ended up telling the user to get over it, it’s just a phone. Apple claims this conversation is a hoax, though BGR stands by their reporting.

What we do know is that Apple’s official stance at the time of this writing is that all phones have this issue to one degree or another, but that iOS4 has badly calibrated signal bars that don’t give people a realistic idea of how likely they are to drop a call. This seems to be true, as people have been able to grip other phones from the Moto RAZR to the Google’s Nexus One in ways that cause similar signal drops, and the "hey, my bars are dropping like flies" effect is showing up on older iPhones that have been upgraded to iOS4. Apple is not recalling the phone or even offering free Bumpers as a matter of policy. Instead, they’re going to address this with a software fix.

Can’t fix the signal, so fix the bars

Wait a second. How can a software fix resolve a physical design issue? Because, as with everything in this story, things are more complex than they seem.

The iPhone 4 handles signal differently than other iPhones. Differently than other phones, as near as I can tell. Previously, iPhones tried to home in on the strongest signal from a tower they could find. The problem is that the tower they’re closest to–thereby providing the strongest signal–might also be the most crowded. Or there might be more electromagnetic interference in that area. So even though the signal is stronger, your call quality might actually be worse.

The iPhone 4 seeks out the "best" signal, not necessarily the strongest. It looks for clarity, lack of interference, low traffic on the tower. As a result, and keeping with digital calling’s binary nature, you "do" have a signal with the iPhone 4 more often than you "don’t" compared to older iPhones, even if the reported signal strength is a lower number.

Apple is going to change the way the bars are displayed so they follow AT&T’s guidelines on how many bars to report for a given signal strength. This seems to be another source for angry misunderstanding among the digerati, so pay attention.

Counterintuitively, this change is going to show fewer bars than you had before for any but really strong signals. Where you used to have four or five bars, you might now only see two. But, and this is important, those two bars are more "durable" and a more accurate indicator of what kind of signal you’ve actually had all along. You never really had the kind of signal strength you thought you did if you used to see five bars and now you see two after installing the patch. You always had "two bar" strength, you just didn’t know it. Everyone clear on that?

Let me sum up

So. Should you hold off on buying an iPhone 4 because of this issue? If you already have one, should you take it back? That depends. Are you dropping calls? Are you dropping more calls than you did with your previous phone, iPhone or not? If not, then I wouldn’t worry about it. As mentioned above, the iPhone 4’s antenna is actually better than the 3GS at holding on to a call at low signal strength, so for all practical purposes the numbers don’t matter.

Personally, my iPhone 4 performs at least as well as my iPhone 3G, and offers so many advantages besides, so I’d be a fool to take it back. Do I use a case? Sometimes. Sometimes not. I keep mine in a Griffin Elan Passport Wallet when I’m on the go along with my driver’s license and debit card. But I take it out frequently to sync, use around the house, for use as a GPS and when typing or watching video in the Griffin Travel Stand (no, I’m not sponsored by Griffin, but I wouldn’t turn them down; I like their products). In or out of a case, I don’t notice the “problem” much. It’s just not an issue. Put aside the hype and noise, and you might see the same.

5 thoughts on “iPhone 4: The bars are a lie”

  1. What we have here is simply the best explanation of how both a service provider and manufacture relate the same information (signal strength) to their end user. I must say it’s unfortunate (mildly out) that Apple failed to “calibrate” the signal strength displayed in a manner consistent with other phones on AT&T’s network.

    Perhaps in the future Apple with better test their devices out in the wild. Can you imagine if this were a car?!? It would have been like calibrating the airbags to deploy based on a fully camouflaged vehicle only to get reports that the airbags in the finished product now deploy in collisions under 15mph.

    Thanks for a detailed, plain English post on what could easily have become a mess of technospeak. And thanks for previewing what’s likely the next wave of complaints when the software “fix” suddenly shows true signal strength. I wonder who’s responsibility will it be to explain the change and will the masses view it as a poor network operated by AT&T or a flawed cellphone manufactured by Apple.

  2. this is a nice write up and yes i drop calls but i can deal with it… what i CANT deal with is the proximity sensor issues… how about a write up on that, huh?

  3. It's my understanding that the proximity sensor issues have to do with something that gets brought over during the upgrade, a corrupt setting or something. I heard that if you restore your iPhone as a new phone you won't have this issue. I know it's a pain, but I set up my iPhone 4 from scratch rather than from a backup of my 3G, and I don't have this issue. If you can't wait for Apple to release a fix, you could always try that.

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