|Another option is to usehomeplug adapters which allow cat-5/ethernet connection...|
Plug one adapter into a mains socket adjacent to your router; connect it to your router via a cat-5/ethernet cable. In your other location plug another adapter into a convenient mains outlet; and then you can connect your Voip device via cat-5/ethernet to that adapter.
Homeplug system is a means of using mains wiring as a network around the premises; the system also being known as lan over mains.
Devolo in Germany was the first such device, not available in the USA/Canada. However Netgear, D-link, Linksys/Cisco have similar; as does TP-link, but this latter brand is pretty low on my list of recommendation..
The lan over mains approach is more stable than the method that uses wifi only to link the router and any other extender. There are homeplug adapters which also provide wifi output as well as cat-5/ethernet.