Download remote files on Android while phone is in standby mode

Hi,

We're building a Unity Android application which downloads a large video file from a remote server. Because this download takes a long time, we would like to be able to put the phone in standby mode or browse to a different app while the download continues in the background.

However, if we leave the app or turn off the phone screen, the download simply stops.

How can we continue downloading big files in the background?