iOS 4 vs. iOS 4.0.1 (and iOS 4.1) signal mapping changes

iOS 4 vs. iOS 4.0.1 signal mapping changes

Anandtech compared the differences in signal mapping between iOS 4 and iOS 4.0.1 (and iOS 4.1) and concluded that Apple has indeed produced a much more reliable system (meaning the old system was less than honestly reporting strength):

As you can see the old way (top) put far too much weight into the 5th bar of signal. Apple's new approach not only splits it up more reasonably between the 4th and 5th bar (still non-linearly keeping you in the 5th bar if possible) but also extends the range of the lower bars.

[...] The result is that most iPhone users will see fewer bars disappear when they hold the iPhone 4 in a bare hand. The side effect is that the iPhone now displays fewer bars in most places, and users that haven’t been reporting signal in dBm will time see the - perhaps a bit shocking - reality of locations previously denoted as having excellent signal.

That was my experience as well -- even with iPhone 3GS.


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Rene Ritchie

EiC of iMore, EP of Mobile Nations, Apple analyst, co-host of Debug, Iterate, Vector, Review, and MacBreak Weekly podcasts. Cook, grappler, photon wrangler. Follow him on Twitter and Google+.

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Reader comments

iOS 4 vs. iOS 4.0.1 (and iOS 4.1) signal mapping changes


This is a huge joke, if any other company portrayed this type of "dishonesty", they would be bashed into oblivion. It sickens me to witness this type of invincibility from a company which brainwashes and transforms the general public into brand loyalty zombies.

@VTP are you serious? Apple is getting hammered from all angles - far from invincible since the 4 launch. I agree they need to do better and say more (hopefully tomorrow), but I'd say they've received a fair amount of criticism.

Who cares how many bars you have, just as long as the coverage is there and there and you can make a call. Its just a display!
But I do like how they extended the coverage for lower bars, so where you would have 0 bars with iOS 4 you could have 1 and make a call with iOS 4.0.1.

The reception on my 3GS got much better after the update, before I only got 1-2 bars in my aparment but now I have got as many as 5 bars (only for a short while though). However, I cannot get any 3G speed, only EDGE grrr :)

I think many of us have experienced that the signal strength on our phones did not seem to match the bars, well before iphone. Its jus now being confessed to. Has Anandtech have other phones mapped out like this?

I still haven't seen five bars since the update! I've fluctuated between 2 and 4, typically more toward the 2 side. I used to get consistent 5 bars in my apt! They had to know they weren't being honest about signal all along!

So basically, this will be another effort to blame AT&T in the US or whatever carrier in other countries...gotta love it: not our fault, blame the carrier.

Apple deserves to be hammered. They did a sh1t job with this signal thing and expect people to just let them off easily? they didnt seem to hesitate when charge me £599 for my iphone 4, and when their products f8ck up its suddenly we consumers are doing the wrong thing for blaming them.

There is no standard for bars. If you want one, can't see how it would be better. Even the SNR number would not be an adequate value as it is just a signal indicator and doesn't tell you what's happening at the tower.
Also, just compare the bar algorithm between what iOS uses and what Android uses. For iOS 4.0 and prior it's basically the same. Just look at the graphic Anandtech has in the same article.

Seems pretty good to me. According to the illustration the old method was definitely majorly flawed. My house, where I thought I would have terrible reception if any before I switched to AT&T, actually gets me full bars AFTER the update and I live in a pretty small town in Southern VA. I definitely didn't think I'd have that good of a signal.
Anyway, holding it in my bare hand as I would if I were to be making a left-handed call, I MIGHT drop one bar but usually don't have any change at all. If I try to go full death grip I've been able to manage dropping two bars max. That's it. So basically, I'm not having much problem with it.

i would like to see the signal "map" pre 2.01 or 2.1 firmware(when apple previously changed how signal is portrayed and see if it is very much different from the new map

Bars, what bars? I don't even look at them. If I can make a phone call, I have a good signal. Do people actually check before making a call?!?

To be honest I can always recreate the result of a death grip & my phone will drop from 5 bars to 1. However, even tho my ip4 shows I have one bar the data speed is still fast and never failed to make a call.
I haven't updated yet...

You don't get it. These are graphic representations of the signal strength. They aren't actually what determines if you can make a call or not. You can make a solid call at 1 bars just like you can with 5 bars. I've made calls with zero bars.
Apple ONLY changed how the phone DISPLAYS the effing signal strenght. Apple DID NOT change how the phone actually receives the signals themselves for communications.

"Improves the formula to determine how many bars of signal strength to display."
In other words, we've rewritten some math numbers to better show you the strength of the cell signal your phone is receiving. NOT, we've rewritten the some math numbers to improve your cell phone reception.
Would changing the colors on your TV allow you to get more channels? No, it wouldn't.
Neither does this software update.
So, again...

I was honestly going to wait until tomorrow before I update but after reading this report I think I will do it now. It seems they are trying to let us see the real kind of reception that we actually get. Seems like a good move on Apple's behalf, but a fix is also what is required. This is Apple after all, I am sure they will make this right.

Yes they only changed the displayed bars.
Compare the Numerical -dbm numbers where one bar changes to another. You can see the Fudge factor introduced about release 2.0.1 because people were whining about low bars (top) has been replaced by a more realistic straight line (bottom).
It doesn't change the actual signal, just the display.
The phones should show about the same signal and bars as any other phone (with allowance for antenna efficiency).
What does this do for Joe User? Nothing, except give him fair warning when he should not risk bridging the Antenna gap.
This is a tempest in a teapot, which they would never have addressed at all were it not for the REAL problem which still persists. We say the mirrors, (blame the user), now we see the smoke (bar adjustments).
Tomorrow will Apple step up and do the right thing? Or are they going to wash their hands and tell us deal with it?

P.S. I've always blamed the iPhone as a reason why I got dropped calls. I've had ATT for about 7 years ( two with the iPhone ) now and of course I got a dropped call here and there but on the iPhone it was a completely different story.
Dropped calls one after the other...
I only hear iPhone users complain about dropped calls. From my point of view, amoung the data devices, blackberry users had less to complain about than iPhone users when it comes to network reliability.
The iPhone was made from the ground up just within the last four years, software and all, while RIM has more experience over many years ... I blame apple's inexperience making mobile data devices on why ATT has came under fire for " bad coverage ".


Bars, what bars? I don’t even look at them. If I can make a phone call, I have a good signal. Do people actually check before making a call?!?

City boy. ;-)

..... I agree.
lol, i JUST updated my iPhone 3GS and grabbed my phone and pulled it closer to my face to make sure that i wasnt seeing things.
It's ugly.

Att may suck but i don't want my iPhone on a network that doesn't allow calls and data (Internet) at the same time. Vz would be slammed as bad as AT&T is if they got the iPhone first. It's just a phone. Return it if you are unsatisfied after tomorrows press conf. Get a life.

i don't understand, but I am not dropping calls in my house now after the 4.0.1 update.
My house has a wide metal roof (the house is the managers quarters of a motel), there is a second floor with another metal roof, and the first floor roof extends far to the east and west sides of the house. there were pockets of 1 bar and "No Service" areas in the house unless I used a signal booster.
After the 4.0.1 update I did a 20-30 minute call with the signal booster (NOT a microcell) turned off and unpowered, and although I hit one bar at times, the audio was crystal clear and had no hickups or slur sounds, plus I could walk thru the "dead zone" areas of the house without having issues.
all in all i am happy. i'll be happier if Apple announced free replacements for current owners, but a case is just as good for me.

How is anyone going to see signal strength in dBm when any apps that displayed it are gone and field test access has been removed as well?

It's not Apples fault. AT&T confesses to it in all of their ads. You just need to read between the lines.
AT&T covers 97% of all Americans. The other 3% is your left hand.

I noticed that. And WHY did they remove that standard GSM functionality from the phone other than to hide something?
I just don't get it. Why wouldn't they want to prove just how superior the iPhone4 is at digging signals out of the noise. (And it is pretty amazingly good at this if not death gripped). A phone delivering clear as a bell conversations at -121db is impressive. Flaunt it!
Instead they hide it.

It's like Toyota fixing their sticky gas pedal problem by changing the Speedometer display to 0.
@VTP you are my hero. All the VTP bashers are probably Apple fanbois with Macintoshs.

Uhh, this does not affect reception. It just adjusts how it's reported to the end user. Those of you who think you are getting better reception from this update are buying into a placebo effect.
There were two problems with the reception issue. One was the software was misrepresenting the reception. The other was the physical location of the antenna being susceptible to being blocked and/or touched.
This update only addresses one of the problems. The hardware issue is still there.
THere CAN be more the one issue for each problem. People tend to think there is only one issue to each problem.

The iphone4 is so amazing.
Oops, i think i have now 10 new virtual friends.
This is so incredible, just like Apple! The most incredible company around thecworld.
Oops, seem to get more virtual friends. Me & my Apple fanboys :)

I just updated my wife's 3Gs and the download was 3xx MB. I updated my 4 and the download was 5xx MB. What's the difference?!?!

So why was it "wrong" in the first place?????? How could something so simple and core to a phone be calculated wrong.
On purpose, probably!
This site should be renamed, the ifanboyblog.
And before you bash, I have an iphone 4. (had a 3gs and 3g as well)

They should have changed it to just one bar: either you have signal or you don't. I'm sure they wish they could get away with that. Just like not showing the battery percentage by default, or the idiot lights in cars, people (non-geeks) can't handle gauges.

Wow the bar calculations in iOS 4 are totally jacked up. They really had problems, there really isn't even a third bar. It's no wonder mine always went from 4 to 2 bars so easily.
I'm still confused though because Apple said this problem has stricken every iPhone to date. My iPhone 3G never displayed behavior like this, the bar readings were pretty constant. In my work break room my 3G normally showed 3-4 bars. My iPhone 4 goes up and down every few minutes just sitting on the table from 1-5 bars.

I installed 4.0.1 earlier and my phone has called 3 people and left vociemails all while in my pocket and in sleep mode. Anyone else?

Very well said. I too have been with cingilar/AT&T many years and have been very happy with coverage and quality. I just upgrade to the iPhone 4 and haven't had too many problems, just normal new product bugs, like any other tech. company. What is fun to observe is the crazies that think apple is perfect. They are just like all of their peers except with the great job they do making many consumers think they are special. The fanboys actually seem to like having to make an apointment to get the seemingly many problems fixed.
I like my iPhone, I love my AT&T service, but it really isn't a great phone.