USB modem.

Unlimited is provided not by a modem, but by a telecom operator.
Coverage also depends on which operator. Maybe - or maybe the speed is not very good.
Mts has unlimited from 1 am to 7 am. For some operators, the speed cuts or the monthly fee is awful.
In any case, depending on what you need. If you download games for a computer, then this is a difficult case - it will take a long time with the current volume of games.

Partner tariff plans, there is full unlimited and there are no restrictions. (From partners Beeline or Megafon).