Android - prevent sleep

[Guest snixuletz]

Hi guys, I will appreciate if you can help me to setup my android to keep the 3g connection ON even if the display is OFF. I'm using Sipdroid and when the phone go to sleep sipdroid also die and I can't receive any calls. I have on my iphone a keep alive app, do you know if it exist for android also. I don't care if my battery die faster.

Thanks