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Inside Apple's changes to the iPhone's signal strength visual bars

post #1 of 26
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With the release of iOS 4.0.1 on Thursday, Apple instated changes to the way its iPhone handsets visualize bars representing cellular signal strength, doing away with a previously optimistic approach that compressed the dynamic range of bars to make it appear that a user's reception was much stronger than it actually was.

In fact, AnandTech, which has been following the matter closely for weeks, discovered that Apple had compressed the dynamic range to such an extent that cradling the company's new iPhone 4 with the so-called "death grip" would make all of its bars disappear from just a 24 dB drop in signal.

Extensive testing of iOS 4.0.1 indicated a drastic change in the cutoffs for the 5 signal bar strength indicators. The pair that authored the report concluded that "Appleā€™s mappings have gone from having probably the most compressed dynamic range among handset vendors to less compressed than Android." iOS 4.0.1 also broadens the range for displaying a signal, with the lower limit shifting from -113 dBm to -121 dBm.* Both testers were able to keep calls connected at the lower limit of -121 dBm when testing with an iPhone 4. They theorized that the increase in display range was to accommodate the iPhone 4's increased sensitivity.

Compared to iOS 4.0, iOS 4.0.1 spreads the signal bars much more evenly throughout the range. It also significantly reduces the range of bar 5, from a range of 40 dB to a range of 25 dB. Bars 4 and 5 in iOS 4.0.1 now cover almost the same range as just bar 5 in iOS 4.0.

With the broader range between bars, users will see less of a drop when experiencing a loss of signal from gripping the phone. As reported earlier, the distance between the low end of bar 5 and no bars in iOS 4.0 was 24 dB (-91 dBm to -113 dBm). In iOS 4.0.1, the distance between the low end of bar 5 and no bars is now 45 dB (-76 dBm to -121 dBm).

The report warned that users will most likely experience an across-the-board apparent loss in signal with the new software update. "The new signal strength visualization in iOS 4.0.1 is simply going to be more honest with iPhone users."



As expected, Apple changed the heights of the signal strength bars. Bars 1, 2, and 3 are taller, making the relative heights appear exponential, rather than linear. Although bars 1 and 2 changed the most, "their respective cutoffs are virtually unchanged."

Although the new display is easier to read, the heightened bars without a corresponding change in cutoff value may lead users to believe that they have better signal than before. According to the report, this change in either the height or cutoff of some of the signal strength visual bars could potentially cause confusion and anger among users.

Anandtech had also conducted tests to verify the loss in signal from contact with the iPhone 4 antenna, as compared to a drop due to a hand simply being close enough to the phone to block signal.

After wrapping high-insulation tape around the stainless steel band, the drop in signal from gripping the phone improved from a drop of 24 dB to a drop of 16.6 dB.* When the tester wore a latex glove, the signal drop reduced even further to a drop of 14.7 dB. While the tape and gloves weren't presented as potential solutions, they did bring the signal drop "in league with the Nexus One's worst case drop, and almost in league with the iPhone 3GS worst case drop."*
post #2 of 26
Quote:
Originally Posted by AppleInsider View Post

With the release of iOS 4.0.1 on Thursday, Apple instated changes to the way its iPhone handsets visualize bars representing cellular signal strength, doing away with a previously optimistic approach that compressed the dynamic range of bars to make it appear that a user's reception was much stronger than it actually was.

In fact, AnandTech, which has been following the matter closely for weeks, discovered that Apple had compressed the dynamic range to such an extent that cradling the company's new iPhone 4 with the so-called "death grip" would make all of its bars disappear from just a 24 dB drop in signal.

Extensive testing of iOS 4.0.1 indicated a drastic change in the cutoffs for the 5 signal bar strength indicators. The pair that authored the report concluded that "Apples mappings have gone from having probably the most compressed dynamic range among handset vendors to less compressed than Android." iOS 4.0.1 also broadens the range for displaying a signal, with the lower limit shifting from -113 dBm to -121 dBm.* Both testers were able to keep calls connected at the lower limit of -121 dBm.

Compared to iOS 4.0, iOS 4.0.1 spreads the signal bars much more evenly throughout the range. It also significantly reduces the range of bar 5, from a range of 40 dB to a range of 25 dB. Bars 4 and 5 in iOS 4.0.1 now cover almost the same range as just bar 5 in iOS 4.0.

With the broader range between bars, users will see less of a drop when experiencing a loss of signal from gripping the phone. As reported earlier, the distance between the low end of bar 5 and no bars in iOS 4.0 was 24 dB (-91 dBm to -113 dBm). In iOS 4.0.1, the distance between the low end of bar 5 and no bars is now 45 dB (-76 dBm to -121 dBm).

The report warned that users will most likely experience an across-the-board apparent loss in signal with the new software update. "The new signal strength visualization in iOS 4.0.1 is simply going to be more honest with iPhone users."



As expected, Apple changed the heights of the signal strength bars. Bars 1, 2, and 3 are taller, making the relative heights appear exponential, rather than linear. Although bars 1 and 2 changed the most, "their respective cutoffs are virtually unchanged."

Although the new display is easier to read, the heightened bars without a corresponding change in cutoff value may lead users to believe that they have better signal than before. According to the report, this change in either the height or cutoff of some of the signal strength visual bars could potentially cause confusion and anger among users.

Anandtech had also conducted tests to verify the loss in signal from contact with the iPhone 4 antenna, as compared to a drop due to a hand simply being close enough to the phone to block signal.

After wrapping high-insulation tape around the stainless steel band, the drop in signal from gripping the phone improved from a drop of 24 dB to a drop of 16.6 dB.* When the tester wore a latex glove, the signal drop reduced even further to a drop of 14.7 dB. While the tape and gloves weren't presented as potential solutions, they did bring the signal drop "in league with the Nexus One's worst case drop, and almost in league with the iPhone 3GS worst case drop."*


So they're saying the software not only changes the bar display but allows you to hold onto calls in a weak signal area longer ?
post #3 of 26
Quote:
Originally Posted by AppleInsider View Post

While the tape and gloves weren't presented as potential solutions, they did bring the signal drop "in league with the Nexus One's worst case drop, and almost in league with the iPhone 3GS worst case drop."

So maybe we'll see the release of the iGlove tomorrow?

Quote:
Originally Posted by Magic8Ball View Post

So they're saying the software not only changes the bar display but allows you to hold onto calls in a weak signal area longer ?

I don't think the results can really indicate the iOS 4.0.1 maintains calls at weaker signals compared to iOS 4.0. In iOS 4.0 and earlier, the lowest signal readout was -113dBm, but I think that's just the lowest number on the scale and anything lower will still be rounded/reported as -113dBm as long as there is a connection. iOS 4.0.1 simply adds additional range to the scale to -121dBm rather than suddenly allowing calls at lower signal levels. Certainly, I don't believe Anandtech made the claim that they are seeing better call performance with iOS 4.0.1 compared to iOS 4.0.
post #4 of 26
I still can't tell from the report whether installing this update will help or hurt. Anyone has an answer?
post #5 of 26
Quote:
Originally Posted by OC4Theo View Post

I still can't tell from the report whether installing this update will help or hurt. Anyone has an answer?

Neither. It's all visual as far as we can tell.
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post #6 of 26
Quote:
Originally Posted by OC4Theo View Post

I still can't tell from the report whether installing this update will help or hurt. Anyone has an answer?

This update does not change performance. It only changes the way that the signal strength is displayed to be a more accurate representation.

I am surprised at just how skewed the original scale was. Guess fudging the numbers to make AT&T look good bit them in the arse.
post #7 of 26
Update sure helps me on the iPad with wifi... finally!
post #8 of 26
Quote:
Originally Posted by OC4Theo View Post

I still can't tell from the report whether installing this update will help or hurt. Anyone has an answer?

It's not just cosmetic. The scale actually measures a broader signal range. That in itself should help.

I'm still waiting to find out if the new algorithm helps the phone determine if it still has a strong enough signal to hold a connection. If the reported disconnections were the result of the phone *thinking* the signal was too weak, then this update will definitely help because weaker signals are now reported to the user, and to the phone itself, more accurately.

I say go ahead and install.
post #9 of 26
Quote:
Originally Posted by OC4Theo View Post

I still can't tell from the report whether installing this update will help or hurt. Anyone has an answer?

It'll make your iPhone 4 snappier!

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post #10 of 26
Quote:
Originally Posted by OC4Theo View Post

I still can't tell from the report whether installing this update will help or hurt. Anyone has an answer?

It is only visual improvement. The problem before was the drop from 5 bars to No Service, which was in fact a drop from 2 or 3 bars to zero. With this update the drop will be 2 bars.

Before this update my iPhone 3GS always showed full bars in my apartment and after the update it is showing 4 bars and when I hold it in my left hand I experience 1 to 2 bars drop. Personally, I think the previous bar scale was intentional and Apple knew how it affects iPhone 4. Remember this two days before the iPhone 4 was released:

Quote:
Yet, in some places where the signal was relatively weak, the iPhone 4 showed no bars, or fewer bars than its predecessor. Apple says that this is a bug it plans to fix, and that it has to do with the way the bars are presented, not the actual ability to make a call. And, in fact, in nearly all of these cases, the iPhone 4 was able to place calls despite the lack of bars

.
post #11 of 26
Quote:
Originally Posted by OC4Theo View Post

I still can't tell from the report whether installing this update will help or hurt. Anyone has an answer?

It won't actually change your performance. It's strictly so the range of signal strength is more accurately displayed. If someone is bothered by seeing it drop from 5 bars to 1 bar, they'll be less affected to see it start out at 3 bars and then drop to 1 bar. Then, that 1 bar is taller so it's visible whereas before it looked to some as zero bars. It's psychological.
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post #12 of 26
Quote:
Originally Posted by gto65l View Post

This update does not change performance. It only changes the way that the signal strength is displayed to be a more accurate representation.

I am surprised at just how skewed the original scale was. Guess fudging the numbers to make AT&T look good bit them in the arse.

Yeah, and it's easy to see why people could have been dropping so many bars before. By the chart, you could be almost at half signal and still have four bars showing, but if you grabbed it at that point, you could drop to one bar by only losing 6db and go to zero bars by only losing 13db.

Even if this is all they do, the drops will be less dramatic, and the angry folks will have to re-focus on whether it actually drops calls or not.
post #13 of 26
Bars are for drinking, not for calling.

But seriously, someone please explain to me WHY in 2010 we still use a crappy graphical representation of signal strength? What's wrong with using a simple percentage meter like the battery does?
post #14 of 26
Quote:
Originally Posted by rtm135 View Post

Bars are for drinking, not for calling.

But seriously, someone please explain to me WHY in 2010 we still use a crappy graphical representation of signal strength? What's wrong with using a simple percentage meter like the battery does?

Thank You! HELLO!!!
post #15 of 26
Quote:
Originally Posted by rtm135 View Post

Bars are for drinking, not for calling.

But seriously, someone please explain to me WHY in 2010 we still use a crappy graphical representation of signal strength? What's wrong with using a simple percentage meter like the battery does?

what does it have to do with 2010? % is actually as bad as linear bars, because the unit itself is logarithmic (dB). If anything, just show the dB loss. However, most users will be thoroughly confused.
I like the bar display, especially the new curved one. It works for me, I'm smart enough to read the actual numbers but don't feel the need to prove it to myself every time I read the screen, bars are fine.
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post #16 of 26
I think the new reporting is so much better and more accurate too!

And now since it's easier to go from 5 to 4 bars (as it should be), I can easily replicate the "death grip" on my old 3GS almost as easily as on my iP4, making it drop from 5 to 4 bars when I hold it around the bottom. And that's as far as they both drop here.

This should definitely at least change the focus of all the complaints and it'll be easier to separate people who really are having dropped calls and slower data transmission from those who just whine due to lost bars...
post #17 of 26
After installing this update I noticed two things:

1. The bars don't jump up and down between one and five bars any more
2. I now have less bars (three, instead of mostly five)

Previously, I could reduce the five bars to one or zero by just holding the phone (with bumper!), now the three bars will become one when I simply pick up the handset. Without the bumper, it used to go from five bars to "searching" as soon as I held the phone in my hand.

Apple's problems are not solved by any means and it is going to be very interesting to hear what they have to say about it today...
post #18 of 26
Quote:
Originally Posted by rtm135 View Post

Bars are for drinking, not for calling.

But seriously, someone please explain to me WHY in 2010 we still use a crappy graphical representation of signal strength? What's wrong with using a simple percentage meter like the battery does?

Because db follow a logarithmic scale, so a relatively small number of db drop would show a correspondingly large percentage drop. Let's say you're in a good signal area and lose 12 db. Under your system, that would display as 94% signal loss - and most people would panic. Yet they would still get a great connection.

I'm assuming that you're at least as knowledgeable as the average public, so the fact that you didn't understand that is an indication that it's probably a bad idea.
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post #19 of 26
Regardless of the bars being displayed, can you place or answer a call and carry on a conversation. That is what really matters.
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post #20 of 26
awesome update.
BEFORE: death grip would go from 5 bars to NO SIGNAL standing in front of my microcell
AFTER: death grip goes from 5 bars to one bar standing in front of my microcell, and if i try to make a call with that one bar, it constantly says "call failed". MUCH BETTER!
post #21 of 26
Quote:
Originally Posted by desarc View Post

awesome update.
BEFORE: death grip would go from 5 bars to NO SIGNAL standing in front of my microcell
AFTER: death grip goes from 5 bars to one bar standing in front of my microcell, and if i try to make a call with that one bar, it constantly says "call failed". MUCH BETTER!

If you have a microcell and can't get a good signal standing right next to it, return either the microcell or the phone (or both) for replacement. What you're describing clearly indicates that one or the other is seriously broken.
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post #22 of 26
Quote:
Originally Posted by jragosta View Post

Because db follow a logarithmic scale, so a relatively small number of db drop would show a correspondingly large percentage drop. Let's say you're in a good signal area and lose 12 db. Under your system, that would display as 94% signal loss - and most people would panic. Yet they would still get a great connection.

I'm assuming that you're at least as knowledgeable as the average public, so the fact that you didn't understand that is an indication that it's probably a bad idea.

I had the same thought - regrading Log vs Linear.

Maybe a better approach would be this scale:
instead of 5 bars - Awesome!
instead of 4 bars - Better
Instead of 3 bars - Cool
Instead of 2 bars - Depends (trying to find a better one here)
Instead of 1 bar - Eek
Instead of 0 bars - Fail

Which could be abbreviated A - B - C - D - E - F

and maybe even use a plus or minus to indicate either data signal or WiFi as in

A+, B- etc.
post #23 of 26
Quote:
Originally Posted by desarc View Post

awesome update.
BEFORE: death grip would go from 5 bars to NO SIGNAL standing in front of my microcell
AFTER: death grip goes from 5 bars to one bar standing in front of my microcell, and if i try to make a call with that one bar, it constantly says "call failed". MUCH BETTER!

If my gas gauge shows empty I put gas in the tank, if I show no bars, I move my hand. I know, I know, we all want to use the phone any place, any time and any way we hold it with nothing less than 5 bars.

Isn't going to happen, with this phone or any other.
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post #24 of 26
Whatever might be the case but seems like with 4.0.1 update, the death grip on my phone is no more so. I do see the bars dropping when I hold the phone "wrong way", but I can still surf and talk and not seeing the No Service problem prior to update. Maybe there is some truth to for SteveJ said. I guess will find the next step in about an hour.
post #25 of 26
Right now, dB strength is converted to bars. I'm proposing that we instead convert it to a numerical value between 0-100 percent, which is much easier to read. It works for the battery meter, so why not this?

By 2010, we've been using signal bars forever. We should have moved on by this point.

Quote:
Originally Posted by mobility View Post

what does it have to do with 2010? % is actually as bad as linear bars, because the unit itself is logarithmic (dB). If anything, just show the dB loss. However, most users will be thoroughly confused.
I like the bar display, especially the new curved one. It works for me, I'm smart enough to read the actual numbers but don't feel the need to prove it to myself every time I read the screen, bars are fine.
post #26 of 26
Quote:
Originally Posted by jragosta View Post

Because db follow a logarithmic scale, so a relatively small number of db drop would show a correspondingly large percentage drop. Let's say you're in a good signal area and lose 12 db. Under your system, that would display as 94% signal loss - and most people would panic. Yet they would still get a great connection.

I'm assuming that you're at least as knowledgeable as the average public, so the fact that you didn't understand that is an indication that it's probably a bad idea.

Yeah, db measures a logarithmic scale, but but it's indicated as db which is the inverse log of the ratio of signal to full signal. In essence it works very well as a percentage indicator (with some adjustments) because it mirrors the way we sense things naturally. The fact that these are digital rather than analog signals makes it somewhat irrelevant though since digital signals have good fidelity until a minimum threshold is reached, then they fail completely (the so called "cliff effect.) I think Apple was trying to indicate this with their original bar calculation algorithm (the one they "goofed up on" and that "stunned" them) which was a good idea, which they should have fessed-up to.
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