iPhone using cell data on wi-fi, even with wi-fi assist turned off?

[bedouin]

I have an iPhone 4S and an iPhone 6, which have 400mb and 1.25gb data plans, respectively.

Wi-fi assist is turned off on the iPhone 6, and the iPhone 4S does not support it in the first place.

I reset the usage stats at the beginning of each billing month on both devices. The iPhone 6's reported cellular data usage is more or less identical to what my carrier reports; on the other hand, my iPhone 4S's reported usage is way off when compared to my carrier — as much as ~300mb off.

Both devices are on wi-ifi nearly all day, and rarely more than 25–30 feet from an access point. I have no reason to believe that the wi-fi signal is weak in my house, as I never experience drop outs and have a very strong signal. In fact, I have two access points in my apartment to make sure there are no dead zones.

I contacted my carrier about this and they claim there is nothing wrong on their end.

Is there any way that the 4S could be using cellular data without me knowing it? At this point I just shut off cellular data on the 4S when I'm at home, as I've seen chunks of data get used up (according to my carrier's stats) even while it is on wi-fi.

Neither device is jailbroken, so I have little reason to believe that malware could be at play.

 

[geoff5093]

Is there a chance you used a lot of cellular data on your 4S before you reset it? The time between when you use your data and when your carrier updates their usage meters can be off by a couple hours. If you reset it again, does the usage still differ greatly?

 

[I7guy]

Wifi assist moves the needle as to when the phone switches to cellular data and not have your ongoing communications interrupted. If wifi assist is off, the phone can still switch to cellular data (provided cellular data is on) although the transition is abrupt and communications will display an error message.

IMO, the only guarantee you don't use cellular data is to turn off cellular data or turn on airplane mode and wifi calling. It's possible there is a bug and IOS prematurely switches to cellular data when the wifi signal is plenty strong...but the best way to guarantee no cellular data is used is to turn it off using the control panel.

 

[bedouin]

Is there a chance you used a lot of cellular data on your 4S before you reset it? The time between when you use your data and when your carrier updates their usage meters can be off by a couple hours. If you reset it again, does the usage still differ greatly?

It's possible I guess, but being that I was at home and on wi-fi around the hours leading up to the reset, I kind of doubt it. Chunks of my data plan were disappearing on my carrier's end throughout the month until the quota was used up in its entirety. When I had a 1.25gb plan on the same phone I never had any major
discrepancies between the usage reported by iOS and my carrier. The conspiracy theorist in me wants to suspect that they miscalculate usage on lower-tier plans to try and force upgrades.

IMO, the only guarantee you don't use cellular data is to turn off cellular data or turn on airplane mode and wifi calling. It's possible there is a bug and IOS prematurely switches to cellular data when the wifi signal is plenty strong...but the best way to guarantee no cellular data is used is to turn it off using the control panel.

I started doing that this billing period. However, my carrier had a promotion last month where they gave away free MBs for a couple of weeks, which I took advantage of when not at home. Unfortunately, their counter reset back to the stats from before the promotion started, so I cannot accurately gauge their stats against my phone's until the package renews in the middle of the month.

 

[Stefan johansson]

If you're on a stable wifi connection,there is no reason to worry.

 

[bedouin]

You would think.

 

[bedouin]

So I was reading this Apple Discussuons thread, which seems to indicate that the iPhone 'sleeps' wi-if when locked and not plugged into a power source.

I did a little investigating and pinged my iPhone 4S that was not plugged in. It did not respond. I picked it up and hit the home button and then the pings were received.

I then pinged my wife's iPad that's plugged in. Pings came back.

Next I pinged my old iPod Touch that was not connected to a power source. No response until hitting the home button.

The confusing thing to me is how devices without cellular connections, like my iPads and iPod Touch, receive push notifications and iMessages flawlessly when their wi-fi is seemingly sleeping.

I guess this answers some of my questions.

The answer would seem to be just ensuring that my devices are always plugged in while at home, but that's a bit impractical because (a) I try to keep my batteries conditioned properly, and do not merely plug devices in if a small amount of power was consumed; and (b) even devices that are plugged in go to 'sleep' if they are not used for a prolonged period (e.g., long enough for TouchID to require entering your passcode again). Besides that, who wants to make and receive phone calls while tethered to a cord, or have to leave their phones in a single room most of the day?

All of this might also explain why cellular usage during wi-fi sleep is not included in the iPhone's own usage calculations, since it still technically considers itself to be connected to an access point while sleeping . . .

 

[Applejuiced]

iPhone data plans nowadays with 400mb and 1.2GB per month?
Most can blow through that in an hours use.
Get a better plan to avoid counting kilobytes or paying data overages.

 

[bedouin]

I work from home, so I rarely consume much from my data plans. The sole reason I have the 1.25gb plan on my iPhone 6 is because I generally take it with me on long trips, or when I think I will need to use the internet heavily. Even so, I rarely put more than a 500mb dent in its plan each month. The iPhone 6 is like new with a battery capacity still above 90%; I try to baby it as much as possible.

The 4S has a 400mb plan and is my daily driver, as well as what I keep beside me around the house to make/receive calls; for that reason, its rarely connected to a power source (unlike the iPhone 6, which is always plugged in). Outside of the home, I use the 4S almost exclusively for e-mails. I am about three weeks into the billing cycle on the 4S and, at least according to the iPhone's stats, have only consumed about 60mb of data; on the other hand, my carrier says I've used more than 100mb. That figure would be much higher if I did not begin turning off cellular data when at home. At least I now know why the 4S eats data even when connected to wi-fi.

 

[C DM]

The confusing thing to me is how devices without cellular connections, like my iPads and iPod Touch, receive push notifications and iMessages flawlessly when their wi-fi is seemingly sleeping.

From what I recall, those types of devices (that don't have support for cellular data) should keep their WiFi connection active, at the very least for notifications.

 

[nebo1ss]

I have the opposite problem to you. I have 30 Gig available on my cell plan and would like to find an automated way to switch off wifi when i leave the house. What happens in my case is that i am away from home and take my phone out to check something on the internet and get no response. Then i find that my phone has connected to some wifi public hotspot that requires a log in and for which i have no ID. I then have to go to settings and switch off WIFI each time. Find it very annoying, that my phone will automatically connect to these networks and provide no access to the internet.

 

[Garen]

I have the opposite problem to you. I have 30 Gig available on my cell plan and would like to find an automated way to switch off wifi when i leave the house. What happens in my case is that i am away from home and take my phone out to check something on the internet and get no response. Then i find that my phone has connected to some wifi public hotspot that requires a log in and for which i have no ID. I then have to go to settings and switch off WIFI each time. Find it very annoying, that my phone will automatically connect to these networks and provide no access to the internet.

Go to settings - WIFI - uncheck "Ask to join Networks " hopefully your problem is solved.

 

[bedouin]

From what I recall, those types of devices (that don't have support for cellular data) should keep their WiFi connection active, at the very least for notifications.

That would make sense, but does not seem to be the case. I just pinged my iPad and my wife's iPad (both wi-fi models). Neither are connected to a power source and have not been for a few hours. No response. If I press the home button, the pings immediately start going through. The plugged in devices, including an iPod Touch, responded to pings as expected.

My only guess is that the push notifications send some kind of magic packet (like wake on LAN) that takes wi-fi out of sleep mode. The idea of sleeping wi-fi on cellular device is weird in the first place, because you'd think 3G/4G would eat up more power than wi-fi.

 

[C DM]

That would make sense, but does not seem to be the case. I just pinged my iPad and my wife's iPad (both wi-fi models). Neither are connected to a power source and have not been for a few hours. No response. If I press the home button, the pings immediately start going through. The plugged in devices, including an iPod Touch, responded to pings as expected.

My only guess is that the push notifications send some kind of magic packet (like wake on LAN) that takes wi-fi out of sleep mode. The idea of sleeping wi-fi on cellular device is weird in the first place, because you'd think 3G/4G would eat up more power than wi-fi.

I guess it's the idea of having both cellular/mobile and WiFi going that might potentially result in more battery usage compared to only having cellular/mobile being active.

As for pinging, what exactly are you doing to accomplish that?

 

[bedouin]

As for pinging, what exactly are you doing to accomplish that?

Pinging them from the terminal, either in macOS or on Linux machines.

 

[C DM]

Pinging them from the terminal, either in macOS or on Linux machines.

I see. Yeah, I'm guessing that it's mostly the connection to APNS that is likely kept active in those situations.