if you don't use bluetooth turn it off; as for wifi there are lots of reasons why it won't work (overcrowded airspace, microwaves that interfere, etc). If you are not using WPA2; then you need to upgrade. I would try changing the channel your wifi is on as well (e.g. if it is 6 now, go to 1 or 11)
What do you mean "protect"? If you don't want the android device to connect to your wifi, don't connect it to the network, or setup a "white list" in the connection filter by MAC address in the router.