For smart meters to operate and communicate with your energy provider there are radio towers around your area to allow the smart meters to communicate.
The smart meter transmits data to the radio towers every 6 minutes or so and the radio tower sends that information instantly to the energy providers computers.
Smart meters are pretty safe too and actually transmits less radiation than your cellphone does so your risk of cancer is very low when having a smart meter on your home.
Smart meters basically communicate with radio towers like your cellphone communicates with cellphone towers.