I've signed up for the NBN 100/40 plan and i'm only getting 11.92Mbps down and 31.83Mbps up.
I've tested connected directly to the modem/router and over WIFI.
Before switching over to the NBN i was getting 115Mbps down over WIFI our line was upgraded yesterday and the new modem was installed
The modem is a Sagemcom Fast 5355-A I'm not able to find information about signal quality or line attenuation.