ipad wifi usage unknown download file ios 7 , 8 , 8.2

hi . i have problem with ios wifi usage and don't know to what download in background !!!

here is some picture to show why my ipad download even i turn off everything in setteing : background refresh , automatic update, location , time zone , ...

i have this problem on 8 ipad on ios 7 and later !!!! i test on mini retina , ipad air , ipad 4, ipad mini 1 ,...

i restore my ipad with dfu on itunes and until now don't find way to stop this download even i test hard reset (home+power)

in this picture you can view in download folder , size of file increase and folder and file don't have a name !!!!!!!!!

i track IP address with system monitor app and i see something download from apple server and i don't know what???

since i have this problem some times must be wait to download finish . size of download most time 200-350 mb and i have slow internet connection and must be wait for 1 or 2 hours to finish download .

this time my ipad shutdown for low battery and then i connect to power this problem back and you can see uptime is 1:20 and all my bandwidth speed is Taking up and i cant even open one page in safari !!!!