try these first:
1. determine the wifi adapter from device manager;
2. uninstall, reboot, and install the latest driver from asus website (or the latest compatible from the original manufacturer);
3. determine from the device manager that there is no exclamation mark beside the wifi adapter;
4. at the power management tab, uncheck the option that let computer to turn the wifi adapter off to save power;
5. check your power plan and select high performance plan.
the problem should be fixed by now.