windows phone 8 - Adding new BackgroundTransferRequest's once app is in background -

adding backgroundtransferrequest's backgroundtransferservice once app in background successful, new requests don't run until app comes foreground. not great scenario of downloading lots of small files may take fair amount of time complete.

i imagine microsoft has implemented behavior design(?), know way around or alternative approach?

a bit of background problem:

i'm developing windows phone 8 map app allows sections of maps downloaded , cached offline use. process can lead 1,000's of map tiles needing downloaded.

i've created process spawns full limit of 25 backgroundtransferrequest's, adds more backgroundtransferservice requests complete. works fine until app goes in background.

i have considered doing web server side processing allow tiles bundled in zip , downloaded single request, complication , result in twice space being required on phone complete download , extract files before deleting original package. but, ideally i'd find way force new backgroundtransferrequest's start running in background.

it's not clear actual question i'd recommend bundling them zip file , downloading that. it's easier work single file thousands.

if disk space genuine issue (not theoretical 1 - i've put thousands of map tiles in under 20mb before, depend on image complexity & quality) make few zip files. you'd avoid btr issue , not take disk space (even temporarily).