Important Revision: Improper use of iPhone 4 and iPhone 3GS multitasking in iOS 4 appears to be the cause of dramatic increase in data plan usage for many people, and faster battery drain for many people. The important take away, is that so long as you have enough memory, when you switch applications on the multi-tasking iPhones, you actually leave the old application running.
If that application has location services enabled, or periodically reloads it’s data from the internet, or trickles in new advertising because it’s a free ad-supported application – you will continue consuming battery power and network usage.
If your screen is locked, your WiFi connection becomes unavailable, which means that the increased network usage is carried by the 3G network and consumes your data plan even though you are powering up next to your WiFi base station.
The temporary fix is to take the time to learn how iPhone multi-tasking works and shut down any unneeded applications that are running:
- double tap the home button to bring up the task bar
- press and hold any application that is running but you no longer want to be running
- then press the minus sign on that application to actually stop it from running
- target any streaming, location aware, and advertising supported applications first
Frankly, I am annoyed with Apple & AT&T that WiFi is shutdown when the iPhone screen locks. That needs to be fixed, but at least we can reduce consumption by closing down noisy apps and additional Safari web pages (we should block Safari anyway until the serious remote exploit security hole is fixed). I am also annoyed with Apple for not making it very clear that behavior had dramatically changed from older iPhones to newer ones. I had no idea I was still running all those applications (and am a little amazed that I had over 60 running simultaneously with no noticeable lag).
Links:
MacWorld Article on MultiTasking
Apple Sales Pitch (I wish this came with a warning about additional resources being used)
Original post and attempted solutions below the fold…
I got an SMS text alert from AT&T today warning me that I was getting close to my data plan’s limits!?
I deliberately converted to the cheaper 200MB/month plan when I got the new iPhone because I’d only used ~175MB in the entire 18 months I owned my iPhone 3G, which gave me an order of magnitude of cushion.
Suddenly I have used 1.3GB in only three weeks!? Needless to say I found this alarming, and we started looking at the detailed bills from AT&T more closely. Turns out my iPhone and my wife’s are reporting many megabytes of data every night while we sleep.
On the surface that is wrong, wrong, wrong.
First off, we are asleep. Our phones should not be incurring expenses without our permission.
Secondly, at home, where we sleep and our iPhones are idle – we have wifi; so data should be using our home network and not the 3G plan.
We have a mystery; what is using up so much data plan over 3G every night even though we have wifi available?
A google search turned up this Apple Support Forum thread, we are not alone:
http://discussions.apple.com/thread.jspa?threadID=2450738&start=0&tstart=0
If you have an iPhone, you are probably experiencing this too; check your detailed billing plan to find out.
If you are not experiencing unexplained late night data usage, please post the list of iPhone applications you have installed!!! Please. I am concerned that there is a trojan horse in amongst the many applications I use, all of which come through the iTunes Music Store, that transmits data late at night. I’d like to get points of difference for comparison, and to eliminate apps that are not doing this.
One common suggestion from that thread is that possibly Safari is waking up in the background of the new iOS 4 operating system and re-loading websites in Pages/Tabs that you have left open… They suggest closing all pages, then going to a new page (aka: “untitled”) before you exit Safari so this cannot happen. Just a theory, and an ugly one, but worth checking out.
Update: Many have pointed out that the reporting on AT&T service plans is not exactly a good indicator of when data plan is getting used, and I can accept that; but my usage still should not have jumped from ~10MB/month to 1.3GB in 3 weeks! That is what I am trying to find out about. The change is about when I switched from iPhone 3G with 3.1.3 OS to iPhone 4 with iOS 4. Many applications got upgraded around the same time (to work correctly with the new OS). Multi-tasking was added.
Update 2: one possible explanation is multi-tasking Safari… I was in the habit of exiting Safari with several pages open. That made resuming mobile web surfing easy and fast. One theory is that multi-tasking allows mobile Safari to wake up and reload those pages periodically; even when I am not on wifi… testing that by closing all safari pages before exit now…
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