Sidebar Sidebar
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

ATT disables LTE during voice calls, drops speeds down to 3G

A

aneftp

macrumors 601
Original poster
Jul 28, 2007
4,379
574
I posted this on Howard Forums also. But thought this is an important issue to address since we all know the next generation iPhone will support LTE data.

http://www.howardforums.com/showthr...-(this-is-a-fact)-WTF?p=14787290#post14787290

But it appears ATT disables LTE data during a voice call. ATT tech level support confirmed this limitation to me also. You can call ATT to confirm yourself. You will drop down to 3G speeds. Not only that, I am barely getting 1mpbs when on a voice call.

Why is this important? Matters big time for those who pay for tethering. Expecting LTE speeds tethering. But suppose you are on a 60 minute conference call on your iPhone LTE. Your spouse is tethering off your iPhone LTE and wonders why her wifi computer speeds are so slow. So ATT has a lot of explaining to do if they advertise the LTE speeds but don't clearly disclose you will drop to 3G data on a voice call.

Another user on another forum had same almost exact speed drops as I did with LTE down to 3G speeds.
 
That's weird.
Would that be something that AT&T put there on purpose or a hardware/design limitation by the phone manufacturer?
I dont see how AT&T would dictate how a phone uses its hardware.
 
I am not sure if this is ATT's thing.

Do we have any Canadian users who have LTE phones who tether? And do you drop down to 3G speeds also?

I would be pissed if I were paying for a tethering plan and knew I would have perfect LTE coverage (Like I have in Orlando). But data drops to 3G on a voice call.
 
I would assume AT&T and whoever your phone manufacturer is puts that in the software so you can't drain your device in 30 minutes. Or overheat. So really, it's more of a protection of the hardware.

Now, the new LTE chips coming later this year will probably enable you to have voice and data over LTE at the same time.
 
aneftp said:
I am not sure if this is ATT's thing.

Do we have any Canadian users who have LTE phones who tether? And do you drop down to 3G speeds also?

I would be pissed if I were paying for a tethering plan and knew I would have perfect LTE coverage (Like I have in Orlando). But data drops to 3G on a voice call.
Click to expand...

But it could vary per device also.
How many LTE phones does AT&T have available now and do they all behave the same?

Kyotoma said:
I would assume AT&T and whoever your phone manufacturer is puts that in the software so you can't drain your device in 30 minutes. Or overheat. So really, it's more of a protection of the hardware.
Click to expand...

I doubt about that.
Drain your device in 30 minutes or overheat by pulling LTE data while on the phone? Doesnt make sense.
 
Maybe just maybe they dont want to separate radios running at the same time or are the LTE radios integrated with the UMTS/GSM radios?
 
SGMD1 said:
Well it's not a Verizon thing. Verizon allows simultaneous voice and data while on 4G LTE.
Click to expand...

Well, Verizon doesn't have a choice, really, unless they want users complaining that they still don't have simultaneous voice and data.
 
Voice-over-LTE (VoLTE) won't be available until 2013.

Until then, only the CDMA carriers are doing simultaneous voice + LTE calls:

To date, only CDMA operators like Verizon Wireless and MetroPCS Inc. (NYSE: PCS) have supported voice calls on LTE smartphones by having more than one radio active in the device -- one for the packet-based LTE data service and another for circuit-switched CDMA voice service.

Now, GSM operators like AT&T Inc. (NYSE: T), Rogers Communications Inc. (Toronto: RCI) and soon TeliaSonera AB (Nasdaq: TLSN) can also support voice on their LTE smartphones. The LTE devices will have multiple radios to support LTE, UMTS and even GSM, but with CS fallback only one radio can be active at any time. So, the device is forced off the LTE network and onto the 2G or 3G network for voice calls.

http://www.lightreading.com/document.asp?doc_id=215057
Click to expand...

Verizon is trialing VoLTE already in a couple of cities.
 
CDMA carriers allow it to be simultaneous out of necessity, and it has one huge, huge problem - it KILLS the battery. CDMA LTE devices have terrible battery life. Though, geting better.

CSFB (Circuit Switched FallBack) is the best approach until VoLTE takes over. It's not a problem for 99% of users, seriously. And for most of us, we'd much rather have improved battery life!
 
Clever if you ask me. Move voice to 3G keeping lte for data only stops things getting congested!!
 
Doesn't surprise me. They also throttle everyone's speeds when on a voice call too. Do a speedtest next time and you'll see. I was 10 feet from the tower and ran a speedtest multiple times and got no less than 7 down, but on a voicecall it was a struggle to get 1 mbps down. Once I hung up I was getting 7 down again. Weird.
 
Gav2k said:
Clever if you ask me. Move voice to 3G keeping lte for data only stops things getting congested!!
Click to expand...

It's not about that. Voice will be over LTE next year.

Right now, AT&T moves both voice and data to 3G during a voice call. The LTE radio turns off.

markie said:
CDMA carriers allow it to be simultaneous out of necessity...
Click to expand...

Good point.
 
Last edited:
markie said:
CDMA carriers allow it to be simultaneous out of necessity, and it has one huge, huge problem - it KILLS the battery. CDMA LTE devices have terrible battery life. Though, geting better.
Click to expand...

Not just CDMA LTE phones, ALL LTE phones. Also, they don't have terrible batteries, it's just that LTE murders phones. My cousin has the Droid Razr and there's a strong significance in battery life when using 3G only vs. 4G.
 
kdarling said:
It's not about that. Voice will be over LTE next year.

Right now, AT&T moves both voice and data to 3G during a voice call. The LTE radio turns off.



Good point.
Click to expand...

Why does LTE radio need to be turned off? That's the part I do not understand. Is it a technical problem? Hardware limitation? Wont they have to disclose that to those who assume they get LTE speeds while tethering and if a long voice call takes place they will be downgraded to 3G data?
 
markie said:
AT&T has been very very open about what's going on here:

http://www.droidmatters.com/news/at...technology-boasts-long-battery-and-slim-form/
Click to expand...

"circuit-switch fallback (CSFB) technology that allows the phone to run on the 4G network, but to “fallback” on to the 3G network when it’s out of the 4G coverage area"

How open is that? I am not out of the 4G coverage area. I got full bars of LTE. I am on LTE data. But once I initiated a phone call I fall out of the 4G coverage area?

Doesn't seem very open to me. Don't you think AT&T should say, "LTE radios are automatically turned off once a phone call is initated and the user will revert to 3G while on a phone call."
 
aneftp said:
Why does LTE radio need to be turned off? That's the part I do not understand. Is it a technical problem? Hardware limitation?
Click to expand...

Hardware. The answer is in the article that markie posted above:

The main difference between (AT&T) phones and the LTE phones offered by competitor Verizon Wireless is that the Verizon phones use two separate radios for the 4G and the 3G with each one utilizing battery power and driving the need for a larger battery and body.

Because a single radio will be employed in the AT&T models, a smaller, more compact battery lends itself well to the refined form and design of these new 4G LTE models.
Click to expand...

With a single radio, AT&T phones have no choice at this time, but to drop LTE and switch back to 3G when a voice call is initiated.

Another downside is that switching to 3G at any time (from 2G or LTE) is an opportunity for a call drop.

The upside is improved battery life.
 
This is NOT a reason AT&T "blows" - I'd reckon the vast majority of people, myself included, would much rather have CSFB than the power-sucking dual-radio solution Verizon is forced into. Seriously, having "only" 1mbps or so (I just speed tested during a call and got just under 1mbps) during a call - that is the speed of an average DSL line - is is NOT a horrible downside.

A power-sucking behemoth device (this is getting better with newer chipsets tho!) is much worse, IMHO. CDMA when out of LTE coverage is much worse. My entire state has no Verizon LTE coverage, but is pretty much totally blanketed with AT&T HSPA+ and gets 3-7mbps or so. Faster than the majority of DSL lines available in my neck of the woods. Fast enough to stream 480p video with no issue (and HD much of the time).

Not only that, but this AT&T HSPA+ coverage is available many places in my state where Verizon phones have a big fat "Searching" - even if I woke up tomorrow and Verizon had LTE everywhere they have CDMA now, I'd stay with AT&T because I'd rather have HSPA+ and much larger coverage. As it is, I don't understand WHY anyone in my neck of the woods has Verizon - it's slower, more expensive, and has far worse coverage. Yet, so many people drink the Flavor-Aid and believe "it's the best"

Verizon and Apple have one huge thing in common - a massive reality distortion field that causes people to believe they're the best even when they're not. Verizon and Apple both have things they're DARN GOOD AT. But the idea among the fanboys that either company is infallible, or always the best, gets on my nerves.
 
markie said:
A power-sucking behemoth device (this is getting better with newer chipsets tho!) is much worse, IMHO.
Click to expand...

The VZW Galaxy Nexus with LTE is quite slim.

CDMA when out of LTE coverage is much worse. My entire state has no Verizon LTE coverage, but is pretty much totally blanketed with AT&T HSPA+ and gets 3-7mbps or so.
Click to expand...

Curious as to which state you're in. Vermont? That's the only one without any VZW LTE which might be considered to have more than the usual AT&T 3G coverage.

There's still many areas of the US where AT&T has no 3G coverage, which means when a user leaves LTE behind, they could drop all the way back to EDGE.
 
kdarling said:
The VZW Galaxy Nexus with LTE is quite slim.



Curious as to which state you're in. Vermont? That's the only one without any VZW LTE which might be considered to have more than the usual AT&T 3G coverage.

There's still many areas of the US where AT&T has no 3G coverage, which means when a user leaves LTE behind, they could drop all the way back to EDGE.
Click to expand...

I'm in Montana. And yes, there are places Verizon's the best choice and places AT&T's the best choice. Neither one is universally great and neither one universally sucks.

As for the Galaxy Nexus, note that I did acknowledge the situation is getting MUCH better for CDMA/LTE devices.
 
markie said:
This is NOT a reason AT&T "blows" - I'd reckon the vast majority of people, myself included, would much rather have CSFB than the power-sucking dual-radio solution Verizon is forced into. Seriously, having "only" 1mbps or so (I just speed tested during a call and got just under 1mbps) during a call - that is the speed of an average DSL line - is is NOT a horrible downside.

A power-sucking behemoth device (this is getting better with newer chipsets tho!) is much worse, IMHO.
Click to expand...

I agree.
I can deal with a 1mpbs download speed when Im on a call. That's not even an issue compared to having an LTE device that dies within 2-3 hours of usage.
If battery is as bad as some Verizon LTE phones then Im sticking to my 4S for a few more years.
 
You must log in or register to reply here.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.
Top Bottom
Back