Problem: The Router/hub you have connected to the Internet cable (ADSL/VDSL/ Cablemodem/ Optic Fiber FttH cable) has Wi-Fi but it reaches only a couple of rooms. The walls decreases the broadband you thought you would get.
You can buy Wi-Fi boosters or Wi-Fi extenders on the powercables, but that will blast your neighbors Wi-Fi out of the ether, and is very unsafe too, because its radiation can be monitored outside too.
A much better solution is to employ low cost Plastic Optic Fiber (POF) dual cable and slide it through the 230 AC yellow plastic pipes in your home and fix a Wi-Fi picocell on the end of that, with wireless enough power in/out to cover the room.
These cables and do-it-yourself installation boxes are for sale at http://ls2connect.nl/ in Hierden, near Harderwijk, The Netherlands. For the EUROPEAN MARKET.
Ls2Connect BV, Zuiderzeestraatweg 55
3849AB Hierden Tel: 0341-453308
Yes, such cabling will be valid if you later change to Wi-Fi 6 (or 5G) picocells and when your home gets an external optic fiber (FttH) network access connection and you want to get the Gigabit/s speeds INSIDE the house too !!
jaap van till, TheConnectivist