Re-locate NBN connection

Hi, 

When my NBN was connected it was put just inside of the garage door at the front of the house. The modem is in the same location.

Due to intermittent Wifi connection (it slows down quite a lot when under a lot of use), can i move the modem to another point of the house or does the modem need to stay where the NBN comes in from the street?

I've thought of using Wifi Extenders and Wifi Powerlines but i don't think this will resolve my issue.

Any thoughts?

Thanks