in 3g [[UIApplication sharedApplication] setIdleTimerDisabled:YES]; is not working sometimes
===

I am working on a application which upload images and videos to server. User can create a queue and upload files so it will take a lot of time to finish uploading, so while uploading we set the idle timer disabled to true

    [[UIApplication sharedApplication] setIdleTimerDisabled:YES];

  
But problem is that its working fine in WiFi network but sometimes its not working when i am in 3G network. Is apple overriding this call because 3G consumes more battery? If so can I stop the screen from sleeping. 

My requirement is that the videos should continue upload even on 3G
Thanks in advance,
