I'm not sure why you are worried about speed if you want to run a core node. I run a node over various public WiFi services, and I don't have any problems over speed, and some are really made with intermittent connection failures. The big problem could be storage of the blockchain, but an external hdd is fairly cheap these days. Your major problem will be getting hold of a copy of the blockchain to get started. To do this, you will need to find someone who will let you download the chain over a fast connection, or copy a recent chain from a trusted source. It really does have to be a trusted source though, as there have been some cases of people supplying dodgy copies in the past.