You can already buy home automation solutions that do this.
You could also use an off-the-shelf Ethernet over mains transceiver to enable an Arduino or other device with an Ethernet interface to communicate. You could use similar products supporting phone or serial data connections over mains if that is closer to what you want.
If you want to make your own mains transceiver, that's difficult and potentially dangerous.
If you want to make your own pretend version of a mains transceiver that sends over a low voltage circuit, you need to explain how this is going to be any different to using a plain bit old of wire. It's possible, if you know enough electronics to apply a carrier to an existing AC circuit, but why you would want to and whether you know enough to do it isn't clear.