Huge data uploads on WiFi even when phone is idle
I have an iPhone 6+. The current iOS version is 8.4.1
When travelling I connect to the internet using a MiFi device. The MiFi is effectively a WiFi router which connects to the internet via the cell phone network. Thus, while the phone communicates via WiFi the actual internet communication is via an expensive cellular data connection.
I have used a MiFi for more than 2 years, with iPhone 3GS, iPhone 5S and iPhone 6 Plus. Until recently this has worked satisfactorily, typically using around 500MB of data per day. I am a fairly heavy internet user so have not been surprised by this amount of data usage.
However, on our most recent trip I have experienced much heavier data usage. I first noticed this when my internet data allowance ran out earlier than expected. When I then bought an additional data allowance I noticed that I had used about 1.5GB in the first day, a large proportion of which was in the form of uploads. In particular I noticed that nearly 1GB was uploaded overnight while the phone was idle.
Since noticing the problem I have been careful to disconnect the phone from the MiFi when not in use. Even so, uploads have still been hundreds of megabytes per day greater than I would expect (sometimes I have noticed 30MB or so being uploaded within a few minutes of connecting).
I have downloaded the DataMan app to supplement the information provided by the MiFi device itself. However, DataMan only reports total data downloads and uploads and I have not been able to find any app that will analyse these totals.
I do upload photos to Facebook, but (a) the total uploads are far, far greater than the total file size of the photos concerned and (b) the uploads happen even when the phone is idle.
I have tried to consider possible culprits:
- iCloud is turned off
- I have not subscribed to Dropbox or any other cloud storage service
- I have turned off Background Data Usage
- I have turned off automatic app (and OS) updates
What can be causing these excessive uploads?
How can I identify which app or apps (or which part of the Operating System) is causing them?
What can I do to limit the amount of data uploaded?
(Since returning home, I have checked and the unexpectedly large uploads still happen when the phone is connected via WiFi to our home router. So the problem seems to be related to the use of WiFi in general rather than to our specific MiFi device.)
iPhone 6 Plus, iOS 8.4.1, null