Thanks for your prompt response, but the patched dsdt didn't actually work on the wake up problem and my modified one is the same.
system will go to sleep without any problem, either with a schedule sleep at a specific time or from the apple menu and choose Sleep or go to sleep by pressing PC's power button.
but once it goes to sleep, the only way to bring it back up is to hold down power button to shut down it, and then i have to turn off and on power supply and restart it, if i don't turn the power off/on first and before i restart it, it'll restart into the sleep state again.