Yes power line adapter: originally they were just for extending Ethernet connections.
Now they do the same but basically, you plug it into next to your router. Connect Ethernet from router into adapter.
Plug other adapter into your router and it will extend your wifi. And you can create an Ethernet connection from it too
Here is one I recommend to buy.
http://www.amazon.co.uk/gp/aw/d/B00DHB2T44/ref=mp_s_a_1_1?qid=1442057518&sr=8-1&pi=SX200_QL40&keywords=powerline+wifi&dpPl=1&dpID=418G-LktvOL&ref=plSrch