Digital Audio Radio Satellite or DARS (also as SDARS, for Satellite Digital Audio Radio Service, among many variations) is the FCC term for satellite radio, currently being made popular in the U.S. by XM Radio and Sirius. It operates in the 2.3-GHz S band, from 2320 to 2345 MHz. Terrestrial repeaters retransmit the signals in areas that are prone to weak signals, due to overhead obstructions like tall buildings in downtown areas.